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  • 1.
    Ambarki, Khalid
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Hallberg, Per
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Jóhannesson, Gauti
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
    Lindén, Christina
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
    Zarrinkoob, Laleh
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Wåhlin, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics. Umeå University, Faculty of Medicine, Umeå Centre for Functional Brain Imaging (UFBI).
    Birgander, Richard
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology.
    Malm, Jan
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Blood flow of ophthalmic artery in healthy individuals determined by phase-contrast magnetic resonance imaging2013In: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 54, no 4, 2738-2745 p.Article in journal (Refereed)
    Abstract [en]

    PURPOSE: Recent development of magnetic resonance imaging (MRI) offers new possibilities to assess ocular blood flow. This prospective study evaluates the feasibility of phase-contrast MRI (PCMRI) to measure flow rate in the ophthalmic artery (OA) and establish reference values in healthy young (HY) and elderly (HE) subjects.

    METHODS: Fifty HY subjects (28 females, 21-30 years of age) and 44 HE (23 females, 64-80 years of age) were scanned on a 3-Tesla MR system. The PCMRI sequence had a spatial resolution of 0.35 mm per pixel, with the measurement plan placed perpendicularly to the OA. Mean flow rate (Qmean), resistive index (RI), and arterial volume pulsatility of OA (ΔVmax) were measured from the flow rate curve. Accuracy of PCMRI measures was investigated using a vessel-phantom mimicking the diameter and the flow rate range of the human OA.

    RESULTS: Flow rate could be assessed in 97% of the OAs. Phantom investigations showed good agreement between the reference and PCMRI measurements with an error of <7%. No statistical difference was found in Qmean between HY and HE individuals (HY: mean ± SD = 10.37 ± 4.45 mL/min; HE: 10.81 ± 5.15 mL/min, P = 0.655). The mean of ΔVmax (HY: 18.70 ± 7.24 μL; HE: 26.27 ± 12.59 μL, P < 0.001) and RI (HY: 0.62 ± 0.08; HE: 0.67 ± 0.1, P = 0.012) were significantly different between HY and HE.

    CONCLUSIONS: This study demonstrated that the flow rate of OA can be quantified using PCMRI. There was an age difference in the pulsatility parameters; however, the mean flow rate appeared independent of age. The primary difference in flow curves between HE and HY was in the relaxation phase of the systolic peak.

  • 2.
    Ambarki, Khalid
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Israelsson, Hanna
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Neurology.
    Wåhlin, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Birgander, Richard
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Malm, Jan
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Neurology.
    Brain ventricular size in healthy elderly: comparison between evans index and volume measurement.2010In: Neurosurgery, ISSN 0148-396X, E-ISSN 1524-4040, Vol. 67, no 1, 94-99 p.Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: A precise definition of ventricular enlargement is important in the diagnosis of hydrocephalus as well as in assessing central atrophy. The Evans index (EI), a linear ratio between the maximal frontal horn width and the cranium diameter, has been extensively used as an indirect marker of ventricular volume (VV). With modern imaging techniques, brain volume can be directly measured. OBJECTIVE: To determine reference values of intracranial volumes in healthy elderly individuals and to correlate volumes with the EI. METHODS: Magnetic resonance imaging (3 T) was performed in 46 healthy white elderly subjects (mean age +/- standard deviation, 71 +/- 6 years) and in 20 patients (74 +/- 7 years) with large ventricles according to visual inspection. VV, relative VV (RVV), and EI were assessed. Ventricular dilation was defined using VV and EI by a value above the 95th percentile range for healthy elderly individuals. RESULTS: In healthy elderly subjects, we found VV = 37 +/- 18 mL, RVV = 2.47 +/- 1.17%, and EI = 0.281 +/- 0.027. Including the patients, there was a strong correlation between EI and VV (R = 0.94) as well as between EI and RVV (R = 0.95). However, because of a wide 95% prediction interval (VV: +/-45 mL; RVV: +/- 2.54%), EI did not give a sufficiently good estimate of VV and RVV. CONCLUSION: VV (or RVV) and the EI reflect different properties. The exclusive use of EI in clinical studies as a marker of enlarged ventricles should be questioned. We suggest that the definition of dilated ventricles in white elderly individuals be defined as VV >77 mL or RVV >4.96 %. Future studies should compare intracranial volumes with clinical characteristics and prognosis.

  • 3.
    Ambarki, Khalid
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Lindqvist, Tomas
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Wåhlin, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Petterson, E
    Warntjes, JBM
    Birgander, Richard
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology.
    Malm, Jan
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Evaluation of automatic measurement of the intracranial volume based on quantitative MR imaging2012In: American Journal of Neuroradiology, ISSN 0195-6108, E-ISSN 1936-959X, Vol. 33, no 10, 1951-1956 p.Article in journal (Refereed)
    Abstract [en]

    BACKGROUND AND PURPOSE: Brain size is commonly described in relation to ICV, whereby accurate assessment of this quantity is fundamental. Recently, an optimized MR sequence (QRAPMASTER) was developed for simultaneous quantification of T1, T2, and proton density. ICV can be measured automatically within minutes from QRAPMASTER outputs and a dedicated software, SyMRI. Automatic estimations of ICV were evaluated against the manual segmentation.

    MATERIALS AND METHODS: In 19 healthy subjects, manual segmentation of ICV was performed by 2 neuroradiologists (Obs1, Obs2) by using QBrain software and conventional T2-weighted images. The automatic segmentation from the QRAPMASTER output was performed by using SyMRI. Manual corrections of the automatic segmentation were performed (corrected-automatic) by Obs1 and Obs2, who were blinded from each other. Finally, the repeatability of the automatic method was evaluated in 6 additional healthy subjects, each having 6 repeated QRAPMASTER scans. The time required to measure ICV was recorded.

    RESULTS: No significant difference was found between reference and automatic (and corrected-automatic) ICV (P > .25). The mean difference between the reference and automatic measurement was -4.84 ± 19.57 mL (or 0.31 ± 1.35%). Mean differences between the reference and the corrected-automatic measurements were -0.47 ± 17.95 mL (-0.01 ± 1.24%) and -1.26 ± 17.68 mL (-0.06 ± 1.22%) for Obs1 and Obs2, respectively. The repeatability errors of the automatic and the corrected-automatic method were <1%. The automatic method required 1 minute 11 seconds (SD = 12 seconds) of processing. Adding manual corrections required another 1 minute 32 seconds (SD = 38 seconds).

    CONCLUSIONS: Automatic and corrected-automatic quantification of ICV showed good agreement with the reference method. SyMRI software provided a fast and reproducible measure of ICV.

  • 4.
    Ambarki, Khalid
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Petr, J.
    Wahlin, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics. Umeå University, Faculty of Medicine, Umeå Centre for Functional Brain Imaging (UFBI).
    Wirestam, R.
    Zarrinkoob, Laleh
    Umeå University, Faculty of Medicine, Umeå Centre for Functional Brain Imaging (UFBI).
    Malm, Jan
    Umeå University, Faculty of Medicine, Umeå Centre for Functional Brain Imaging (UFBI).
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Partial Volume Correction of Cerebral Perfusion Estimates Obtained by Arterial Spin Labeling2015In: 16th Nordic-Baltic Conference on Biomedical Engineering: 16. NBC & 10. MTD 2014 joint conferences. October 14-16, 2014, Gothenburg, Sweden, 2015, Vol. 48, 17-19 p.Conference paper (Refereed)
    Abstract [en]

    Arterial Spin labeling (ASL) is a fully non-invasive MRI method capable to quantify cerebral perfusion. However, gray (GM) and white matter (WM) ASL perfusions are difficult to assess separately due to limited spatial resolution increasing the partial volume effects (PVE). In the present study, ASL PVE correction was implemented based on a regression algorithm in 22 healthy young men. PVE corrected perfusion of GM and WM were compared to previous studies. PVE-corrected GM perfusion was in agreement with literature values. In general, WM perfusion was higher despite the use of PVE correction.

  • 5.
    Ambarki, Khalid
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Wåhlin, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Birgander, Richard
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Malm, Jan
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    MR imaging of brain volumes: evaluation of a fully automatic software2011In: American Journal of Neuroradiology, ISSN 0195-6108, E-ISSN 1936-959X, Vol. 32, no 2, 408-412 p.Article in journal (Refereed)
    Abstract [en]

    BACKGROUND AND PURPOSE: Automatic assessment of brain volumes is needed in researchand clinical practice. Manual tracing is still the criterionstandard but is time-consuming. It is important to validatethe automatic tools to avoid the problems of clinical studiesdrawing conclusions on the basis of brain volumes estimatedwith methodologic errors. The objective of this study was toevaluate a new commercially available fully automatic softwarefor MR imaging of brain volume assessment. Automatic and expertmanual brain volumes were compared.

    MATERIALS AND METHODS: MR imaging (3T, axial T2 and FLAIR) was performed in 41 healthyelderly volunteers (mean age, 70 ± 6 years) and 20 patientswith hydrocephalus (mean age, 73 ± 7 years). The softwareQBrain was used to manually and automatically measure the followingbrain volumes: ICV, BTV, VV, and WMHV. The manual method hasbeen previously validated and was used as the reference. Agreementbetween the manual and automatic methods was evaluated by usinglinear regression and Bland-Altman plots.

    RESULTS: There were significant differences between the automatic andmanual methods regarding all volumes. The mean differences wereICV = 49 ± 93 mL (mean ± 2SD, n = 61), BTV = 11± 70 mL, VV = –6 ± 10 mL, and WMHV = 2.4± 9 mL. The automatic calculations of brain volumes tookapproximately 2 minutes per investigation.

    CONCLUSIONS: The automatic tool is promising and provides rapid assessmentof brain volumes. However, the software needs improvement beforeit is incorporated into research or daily use. Manual segmentationremains the reference method.

  • 6.
    Ambarki, Khalid
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Wåhlin, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences. Umeå University, Faculty of Medicine, Umeå Centre for Functional Brain Imaging (UFBI).
    Zarrinkoob, Laleh
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Wirestam, R.
    Petr, J.
    Malm, Jan
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF). Umeå University, Faculty of Medicine, Umeå Centre for Functional Brain Imaging (UFBI).
    Accuracy of Parenchymal Cerebral Blood Flow Measurements Using Pseudocontinuous Arterial Spin-Labeling in Healthy Volunteers2015In: American Journal of Neuroradiology, ISSN 0195-6108, E-ISSN 1936-959X, Vol. 36, no 10, 1816-1821 p.Article in journal (Refereed)
    Abstract [en]

    BACKGROUND AND PURPOSE: The arterial spin-labeling method for CBF assessment is widely available, but its accuracy is not fully established. We investigated the accuracy of a whole-brain arterial spin-labeling technique for assessing the mean parenchymal CBF and the effect of aging in healthy volunteers. Phase-contrast MR imaging was used as the reference method. MATERIALS AND METHODS: Ninety-two healthy volunteers were included: 49 young (age range, 20-30 years) and 43 elderly (age range, 65-80 years). Arterial spin-labeling parenchymal CBF values were averaged over the whole brain to quantify the mean pCBF(ASL) value. Total. CBF was assessed with phase-contrast MR imaging as the sum of flows in the internal carotid and vertebral arteries, and subsequent division by brain volume returned the pCBF(PCMRI) value. Accuracy was considered as good as that of the reference method if the systematic difference was less than 5 mL/min/100 g of brain tissue and if the 95% confidence intervals were equal to or better than +/- 10 mL/min/100 g. RESULTS: pCBF(ASL) correlated to pCBF(PCMRI) (r = 0.73; P < .001). Significant differences were observed between the pCBF(ASL) and pCBF(PCMRI) values in the young (P = .001) and the elderly (P < .001) volunteers. The systematic differences (mean 2 standard deviations) were -4 +/- 14 mL/min/100 g in the young subjects and 6 +/- 12 mL/min/100 g in the elderly subjects. Young subjects showed higher values than the elderly subjects for pCBF(PCMRI) (young, 57 +/- 8 mL/min/100 g; elderly, 54 +/- 7 mL/min/100 g; P = .05) and pCBF(ASL) (young, 61 +/- 10 mL/min/100 g; elderly, 48 +/- 10 mL/min/100 g; P < .001). CONCLUSIONS: The limits of agreement were too wide for the arterial spin-labeling method to be considered satisfactorily accurate, whereas the systematic overestimation in the young subjects and underestimation in the elderly subjects were close to acceptable. The age-related decrease in parenchymal CBF was augmented in arterial spin-labeling compared with phase-contrast MR imaging.

  • 7.
    Andersson, Kennet
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Manchester, I. R.
    Laurell, Katarina
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Cesarini, K. Giuliana
    Malm, Jan
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Measurement of CSF dynamics with oscillating pressure infusion2013In: Acta Neurologica Scandinavica, ISSN 0001-6314, E-ISSN 1600-0404, Vol. 128, no 1, 17-23 p.Article in journal (Refereed)
    Abstract [en]

    Introduction Infusion tests are used to diagnose and select patients with idiopathic normal pressure hydrocephalus (INPH) for shunt surgery. The test characterizes cerebrospinal fluid dynamics and estimates parameters of the cerebrospinal fluid system, the pressure-volume index (PVI) and the outflow conductance (Cout). The Oscillating Pressure Infusion (OPI) method was developed to improve the test and reduce the investigation time. The aim of this study was to evaluate the new OPI method by comparing it with an established reference method. Methods Forty-seven patients (age 71.2 +/- 8.9years) with communicating hydrocephalus underwent a preoperative lumbar infusion investigation with two consecutive infusion protocols, reference (42min) and new (20min), that is, 94 infusion tests in total. The OPI method estimated Cout and PVI simultaneously. A real-time analysis of reliability was applied to investigate the possibility of infusion time reduction. Results The difference in Cout between the methods was 1.2 +/- 1.8l/s/kPa (Rout=-0.8 +/- 3.5mmHg/ml/min), P<0.05, n=47. With the reliability analysis, the preset 20min of active infusion could have been even further reduced for 19 patients to between 10 and 19min. PVI was estimated to 16.1 +/- 6.9ml, n=47. Conclusions The novel Oscillating Pressure Infusion method produced real-time estimates of Cout including estimates of reliability that was in good agreement with the reference method and allows for a reduced and individualized investigation time.

  • 8.
    Andersson, Kennet
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Manchester, Ian R
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Andersson, Nina
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Shiriaev, Anton
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Malm, Jan
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Neurology.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Assessment of cerebrospinal fluid outflow conductance using an adaptive observer-experimental and clinical evaluation2007In: Physiological Measurement, ISSN 0967-3334, E-ISSN 1361-6579, Vol. 28, no 11, 1355-1368 p.Article in journal (Refereed)
    Abstract [en]

    Idiopathic normal pressure hydrocephalus (INPH) patients have a disturbance in the dynamics of the cerebrospinal fluid (CSF) system. The outflow conductance, C, of the CSF system has been suggested to be prognostic for positive outcome after treatment with a CSF shunt. All current methods for estimation of C have drawbacks; these include lack of information on the accuracy and relatively long investigation times. Thus, there is a need for improved methods. To accomplish this, the theoretical framework for a new adaptive observer (OBS) was developed which provides real-time estimation of C. The aim of this study was to evaluate the OBS method and to compare it with the constant pressure infusion (CPI) method. The OBS method was applied to data from infusion investigations performed with the CPI method. These consisted of repeated measurements on an experimental set-up and 30 patients with suspected INPH. There was no significant difference in C between the CPI and the OBS method for the experimental set-up. For the patients there was a significant difference, −0.84 ± 1.25 µl (s kPa)−1, mean ± SD (paired sample t-test, p < 0.05). However, such a difference is within clinically acceptable limits. This encourages further development of this new real-time approach for estimation of the outflow conductance.

  • 9.
    Andersson, Kennet
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Manchester, Ian R
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Malm, Jan
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Neurology.
    Eklund, Anders
    Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF). Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Real-time estimation of cerebrospinal fluid system parameters via oscillating pressure infusion2010In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 48, no 11, 1123-1131 p.Article in journal (Refereed)
    Abstract [en]

    Hydrocephalus is related to a disturbed cerebrospinal fluid (CSF) system. For diagnosis, lumbar infusion test are performed to estimate outflow conductance, C (out), and pressure volume index, PVI, of the CSF system. Infusion patterns and analysis methods used in current clinical practice are not optimized. Minimizing the investigation time with sufficient accuracy is of major clinical relevance. The aim of this study was to propose and experimentally evaluate a new method, the oscillating pressure infusion (OPI). The non-linear model of the CSF system was transformed into a linear time invariant system. Using an oscillating pressure pattern and linear system identification methods, C (out) and PVI with confidence intervals, were estimated in real-time. Forty-two OPI and constant pressure infusion (CPI) investigations were performed on an experimental CSF system, designed with PVI = 25.5 ml and variable C (out). The ARX model robustly estimated C (out) (mean C (out,OPI) - C (out,CPI) = 0.08 μl/(s kPa), n = 42, P = 0.68). The Box-Jenkins model proved most reliable for PVI (23.7 ± 2.0 ml, n = 42). The OPI method, with its oscillating pressure pattern and new parameter estimation methods, efficiently estimated C (out) and PVI as well as their confidence intervals in real-time. The results from this experimental study show potential for the OPI method and supports further evaluation in a clinical setting.

  • 10.
    Andersson, Kennet
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Sundström, Nina
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Malm, Jan
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Effect of resting pressure on the estimate of cerebrospinal fluid outflow conductance2011In: Fluids and barriers of the CNS, ISSN 2045-8118, Vol. 8, no 1, 15- p.Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: A lumbar infusion test is commonly used as a predictive test for patients with normal pressure hydrocephalus and for evaluation of cerebrospinal fluid (CSF) shunt function. Different infusion protocols can be used to estimate the outflow conductance (Cout) or its reciprocal the outflow resistance, (Rout) with or without using the baseline resting pressure, Pr. Both from a basic physiological research and a clinical perspective, it is important to understand the limitations of the model on which infusion tests are based. By estimating Cout using two different analyses, with or without Pr, the limitations could be explored. The aim of this study was to compare the Cout estimates, and investigate what effect Pr had on the results.

    METHODS: Sixty-three patients that underwent a constant pressure infusion protocol as part of their preoperative evaluation for normal pressure hydrocephalus, were included (age 70.3+/-10.8 years (mean +/-SD). The analysis was performed without (Cexcl Pr) and with (Cincl Pr) Pr. The estimates were compared using Bland-Altman plots and paired sample t-tests (p<0.05 considered significant).

    RESULTS: Mean Cout for the 63 patients was: Cexcl Pr = 7.0+/-4.0 (mean +/-SD) ul/(s kPa) and Cincl Pr = 9.1+/-4.3 ul/(s kPa) and Rout was 19.0+/-9.2 and 17.7+/-11.3 mmHg/ml/min, respectively. There was a positive correlation between methods (r=0.79, n=63, p<0.01). The difference, DeltaCout, -2.1+/-2.7 ul/(s kPa) between methods was significant (p<0.01) and DeltaRout was 1.2 +/- 8.8 mmHg/ml/min). The Bland-Altman plot visualized that the variation around the mean difference was similar all through the range of measured values and there was no correlation between DeltaCout and Cout.

    CONCLUSIONS: The difference between Cout estimates, obtained from analyses with or without Pr, needs to be taken into consideration when comparing results from studies using different infusion test protocols. The study suggests variation in CSF formation rate, variation in venous pressure or a pressure dependent Cout as possible causes for the deviation from the CSF absorption model seen in some patients.

  • 11.
    Andersson, Nina
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Grip, Helena
    Umeå University, Faculty of Medicine, Department of Community Medicine and Rehabilitation, Physiotherapy.
    Lindvall, Peter
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Koskinen, Lars-Owe D
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Brändström, Helge
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Anaesthesiology.
    Malm, Jan
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Air transport of patients with intracranial air: computer model of pressure effects2003In: Aviation, Space and Environmental Medicine, ISSN 0095-6562, E-ISSN 1943-4448, Vol. 74, no 2, 138-144 p.Article in journal (Refereed)
  • 12.
    Andersson, Nina
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Malm, Jan
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Neurology. Neurologi.
    Bäcklund, Tomas
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Assessment of cerebrospinal fluid outflow conductance using constant-pressure infusion - a method with real time estimation of reliability2005In: Physiological Measurement, ISSN 0967-3334, E-ISSN 1361-6579, Vol. 26, no 6, 1137-1148 p.Article in journal (Refereed)
  • 13.
    Andersson, Nina
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics. Department of Biomedical Engineering and Informatics, Umeå University Hospital.
    Malm, Jan
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Neurology.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics. Department of Biomedical Engineering and Informatics, Umeå University Hospital.
    Dependency of cerebrospinal fluid outflow resistance on intracranial pressure2008In: Journal of Neurosurgery, ISSN 0022-3085, E-ISSN 1933-0693, Vol. 109, no 5, 918-922 p.Article in journal (Refereed)
    Abstract [en]

    OBJECT: The outflow resistance (Rout) of the cerebrospinal fluid (CSF) system has generally been accepted by most investigators as independent of intracranial pressure (ICP), but there are also those claiming that it is not. The general belief is that this question has been investigated numerous times in the past, but few studies have actually been specifically aimed at looking at this relationship, and no study has been able to provide scientific evidence to elucidate fully this fundamental and important issue. The objective of this study was to investigate the relationship between ICP and CSF outflow in 30 patients investigated for idiopathic normal-pressure hydrocephalus. METHODS: Lumbar infusion tests with constant pressure levels were performed, and ICP and corresponding flow were measured on 6 pressure levels for each patient. All data were standardized for comparison. RESULTS: In the range of moderate increases from baseline pressure (approximately 5-12 mm Hg, mean baseline pressure 11.7 mm Hg), the assumption of a pressure-independent Rout was confirmed (p = 0.5). However, when the pressure increment from baseline pressure was larger (approximately 15-22 mm Hg), the relationship had a nonlinear tendency (p < 0.05). CONCLUSIONS: The results of this study support the classic textbook theory of a pressure-independent Rout in the normal ICP range, where the CSF system is commonly operating. However, the theory might have to be questioned in regions where ICP exceeds baseline pressure by too much.

  • 14.
    Andersson, Nina
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Malm, Jan
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Neurology.
    Wiklund, Urban
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Adaptive method for assessment of cerebrospinal fluid outflow conductance.2007In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 45, no 4, 337-343 p.Article in journal (Refereed)
    Abstract [en]

    Outflow conductance (C out) is important for predicting shunt responsiveness in patients with suspected idiopathic adult hydrocephalus syndrome (IAHS). C out is determined by performing an infusion test into the cerebrospinal fluid system, and the reliability of the test is dependent on the measurement time. The objective of this study was to develop an adaptive signal analysis method to reduce the investigation time, by taking the individual intracranial pressure variations of the patient into consideration. The method was evaluated on 28 patients with suspected IAHS. The results from full time investigations (60 min) were compared to the results of the new algorithm. Applying the new adaptive method resulted in a reduction of mean investigation time by 14.3 ± 5.9 min (mean ± SD), p < 0.01. The reduction of reliability in the C out estimation was found clinically negligible. We thus recommend this adaptive method to be used when performing constant pressure infusion tests.

  • 15.
    Arnell, Kai
    et al.
    Department of Paediatric Surgery, University Hospital, Uppsala.
    Koskinen, Lars-Owe D
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Neurosurgery.
    Malm, Jan
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Neurology.
    Eklund, Anders
    Evaluation of Strata NSC and Codman Hakim adjustable cerebrospinal fluid shunts and their corresponding antisiphon devices: laboratory investigation2009In: Journal of Neurosurgery: Pediatrics, ISSN 1933-0707, E-ISSN 1933-0715, Vol. 3, no 3, 166-172 p.Article in journal (Refereed)
    Abstract [en]

    OBJECT: The authors investigated and compared the in vitro characteristics of 2 CSF shunts, the Strata NSC and the Codman Hakim, and their corresponding antisiphon devices (ASDs).

    METHODS: Six new CSF shunts and the corresponding ASDs for each model were tested in an automated, computerized experimental setup based on pressure regulation. Opening pressure accuracy, resistance, sensitivity to abdominal pressure, antisiphon effect, and the influence of different ASD positions were determined.

    RESULTS: In general the shunts performed according to the manufacturers' specifications. However, at the lowest setting, the opening pressure of the Strata NSC was close to 0, and in the Codman Hakim shunt, it was higher than specified. The resistance in the Codman Hakim shunt (5.4 mm Hg/ml/min) was much higher than that in the Strata NSC (3.6 mm Hg/ml/min). Abdominal pressure affected opening pressure in both valves. Positioning the Strata ASD above or below the ventricular catheter tip resulted in higher and lower opening pressures, respectively, than when it was placed in line with the catheter. The positioning of the Codman Hakim ASD did not influence the opening pressure.

    CONCLUSIONS: Both CSF shunts work properly, but at the lowest setting the opening pressure of the Strata NSC was near 0 and in the Codman Hakim it was twice the manufacturer's specifications. The resistance in the Strata NSC was below the normal physiological range, and in the Codman Hakim device it was in the lower range of normal. The ASD did not change the shunt characteristics in the lying position and therefore might not do so in children. If this is the case, then a shunt system with an integrated ASD could be implanted at the first shunt insertion, thus avoiding a second operation and the possibility of infection.

  • 16.
    Behrens, Anders
    et al.
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience. Blekinge Centre of Competence, Blekinge Hospital Karlskrona, Karlskrona, Sweden.
    Eklund, Anders
    Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF). Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Elgh, Eva
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Psychiatry.
    Smith, Cynthia
    Williams, Michael A
    Malm, Jan
    A computerized neuropsychological test battery designed for idiopathic normal pressure hydrocephalus2014In: Fluids and Barriers of the CNS, ISSN 2045-8118, E-ISSN 2045-8118, Vol. 11, 22Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: A tool for standardized and repeated neuropsychological assessments in patients with idiopathic normal pressure hydrocephalus (INPH) is needed. The objective of this study was to develop a computerized neuropsychological test battery designed for INPH and to evaluate its reliability, validity and patient's ability to complete the tests.

    METHODS: Based on a structured review of the literature on neuropsychological testing in INPH, the eight tests most sensitive to the INPH cognitive profile were implemented in a computerized format. The Geriatric Depression Scale (GDS) was also included. Tests were presented on a touch-screen monitor, with animated instructions and speaker sound. The battery was evaluated with the following cohorts: A. Test-retest reliability, 44 healthy elderly; B. Validity against standard pen and pencil testing, 28 patients with various cognitive impairments; C. Ability to complete test battery, defined as completion of at least seven of the eight tests, 40 investigated for INPH.

    RESULTS: A. All except the figure copy test showed good test-retest reliability, r = 0.67-0.90; B. A high correlation was seen between conventional and computerized tests (r = 0.66-0.85) except for delayed recognition and figure copy task; C. Seventy-eight percent completed the computerized battery; Patients diagnosed with INPH (n = 26) performed worse on all tests, including depression score, compared to healthy controls.

    CONCLUSIONS: A new computerized neuropsychological test battery designed for patients with communicating hydrocephalus and INPH was introduced. Its reliability, validity for general cognitive impairment and completion rate for INPH was promising. After exclusion of the figure copy task, the battery is ready for clinical evaluation and as a next step we suggest validation for INPH and a comparison before and after shunt surgery.

    TRIAL REGISTRATION: ClinicalTrials.org NCT01265251.

  • 17.
    Behrens, Anders
    et al.
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Neurology.
    Lenfeldt, Niklas
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Neurology.
    Ambarki, Khalid
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Malm, Jan
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Neurology.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Koskinen, Lars-Owe
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Neurosurgery.
    Transcranial Doppler pulsatility index: not an accurate method to assess intracranial pressure.2010In: Neurosurgery, ISSN 0148-396X, E-ISSN 1524-4040, Vol. 66, no 6, 1050-1057 p.Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Transcranial Doppler sonography (TCD) assessment of intracranial blood flow velocity has been suggested to accurately determine intracranial pressure (ICP). OBJECTIVE: We attempted to validate this method in patients with communicating cerebrospinal fluid systems using predetermined pressure levels. METHODS: Ten patients underwent a lumbar infusion test, applying 4 to 5 preset ICP levels. On each level, the pulsatility index (PI) in the middle cerebral artery was determined by measuring the blood flow velocity using TCD. ICP was simultaneously measured with an intraparenchymal sensor. ICP and PI were compared using correlation analysis. For further understanding of the ICP-PI relationship, a mathematical model of the intracranial dynamics was simulated using a computer. RESULTS: The ICP-PI regression equation was based on data from 8 patients. For 2 patients, no audible Doppler signal was obtained. The equation was ICP = 23*PI + 14 (R = 0.22, P < .01, N = 35). The 95% confidence interval for a mean ICP of 20 mm Hg was -3.8 to 43.8 mm Hg. Individually, the regression coefficients varied from 42 to 90 and the offsets from -32 to +3. The mathematical simulations suggest that variations in vessel compliance, autoregulation, and arterial pressure have a serious effect on the ICP-PI relationship. CONCLUSIONS: The in vivo results show that PI is not a reliable predictor of ICP. Mathematical simulations indicate that this is caused by variations in physiological parameters.

  • 18.
    Behrens, Anders
    et al.
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Lenfeldt, Niklas
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Ambarki, Khalid
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Malm, Jan
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Koskinen, Lars-Owe D
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Neurosurgery.
    Intracranial Pressure and Pulsatility Index:  2011In: Neurosurgery, ISSN 0148-396X, E-ISSN 1524-4040, Vol. 69, no 4, E1033-E1034 p.Article in journal (Refereed)
  • 19.
    Behrens, Anders
    et al.
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Lenfeldt, Niklas
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Qvarlander, Sara
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Koskinen, Lars-Owe
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Malm, Jan
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Are intracranial pressure wave amplitudes measurable through lumbar puncture?2013In: Acta Neurologica Scandinavica, ISSN 0001-6314, E-ISSN 1600-0404, Vol. 127, no 4, 233-241 p.Article in journal (Refereed)
    Abstract [en]

     Objective The aim of this study was to investigate whether pulsations measured in the brain correspond to those measured in lumbar space, and subsequently whether lumbar punctures could replace invasive recordings. Methods In ten patients with normal pressure hydrocephalus, simultaneous recordings of the intracranial pressure (ICP; intraparenchymal) and lumbar pressure (LP; cerebrospinal fluid pressure) were performed. During registration, pressure was altered between resting pressure and 45mmHg using an infusion test. Data were analyzed regarding pulsations (i.e., amplitudes). Also, the pressure sensors were compared in a bench test. Results The correlation between intracranial and lumbar amplitudes was 0.98. At resting pressure, and moderately elevated ICP, intracranial pulse amplitudes exceeded that of lumbar space with about 0.9mmHg. At the highest ICP, the difference changed to 0.2mmHg. The bench test showed that the agreement of sensor readings was good at resting pressure, but reduced at higher amplitudes. Conclusions Compared to intracranial registrations, amplitudes measured through lumbar puncture were slightly attenuated. The bench test showed that differences were not attributable to dissimilarities of the sensor systems. A lumbar pressure amplitude measurement is an alternative to ICP recording, but the thresholds for what should be interpreted as elevated amplitudes need to be adjusted.

  • 20.
    Dunås, Tora
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Wahlin, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences. Umeå University, Faculty of Medicine, Umeå Centre for Functional Brain Imaging (UFBI).
    Ambarki, Khalid
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Zarrinkoob, Laleh
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Birgander, Richard
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Malm, Jan
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences. Umeå University, Faculty of Medicine, Umeå Centre for Functional Brain Imaging (UFBI).
    Automatic labeling of cerebral arteries in magnetic resonance angiography2016In: Magnetic Resonance Materials in Physics, Biology and Medicine, ISSN 0968-5243, E-ISSN 1352-8661, Vol. 29, no 1, 39-47 p.Article in journal (Refereed)
    Abstract [en]

    In order to introduce 4D flow magnetic resonance imaging (MRI) as a standard clinical instrument for studying the cerebrovascular system, new and faster postprocessing tools are necessary. The objective of this study was to construct and evaluate a method for automatic identification of individual cerebral arteries in a 4D flow MRI angiogram. Forty-six elderly individuals were investigated with 4D flow MRI. Fourteen main cerebral arteries were manually labeled and used to create a probabilistic atlas. An automatic atlas-based artery identification method (AAIM) was developed based on vascular-branch extraction and the atlas was used for identification. The method was evaluated by comparing automatic with manual identification in 4D flow MRI angiograms from 67 additional elderly individuals. Overall accuracy was 93 %, and internal carotid artery and middle cerebral artery labeling was 100 % accurate. Smaller and more distal arteries had lower accuracy; for posterior communicating arteries and vertebral arteries, accuracy was 70 and 89 %, respectively. The AAIM enabled fast and fully automatic labeling of the main cerebral arteries. AAIM functionality provides the basis for creating an automatic and powerful method to analyze arterial cerebral blood flow in clinical routine.

  • 21.
    Dunås, Tora
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Wåhlin, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics. Umeå University, Faculty of Medicine, Umeå Centre for Functional Brain Imaging (UFBI).
    Zarrinkoob, Laleh
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Ambarki, Khalid
    Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF). Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Malm, Jan
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Towards Automatic Identification of Cerebral Arteries in 4D Flow MRI2015In: 16th Nordic-Baltic Conference on Biomedical Engineering / [ed] Henrik Mindedal, Mikael Persson, 2015, Vol. 48, 40-43 p.Conference paper (Refereed)
    Abstract [en]

    4D flow MRI is a powerful imaging technique which provides an angiographic image with information about blood flow in a large volume, time resolved over the cardiac cycle, in a short imaging time. This study aims to develop an automatic method for identification of cerebral arteries. The proposed method is based on an atlas of twelve arteries, developed from 4D flow MRI of 25 subjects. The atlas was constructed by normalizing all images to MNI-space, manually identifying the arteries and creating an average over the volume. The identification is done by extracting a vascular skeleton from the image, transforming it to MNI-space, labeling it with the atlas and transforming it back to subject space. The method was evaluated on a pilot cohort of 8 subjects. The rate of correctly identified arteries was 97%.

  • 22.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Resonator sensor technique for medical use: an intraocular pressure measurement system2002Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In the work of this doctoral dissertation a new resonator sensor technique, first presented in 1989, has been further developed and evaluated with focus on technical characteristics and applications within the medical field.

    In a first part a catheter-type tactile sensor using the resonator sensor technique was evaluated in a silicone model and applied to human prostate in vitro. The main finding was that different histological compositions of prostate tissue correlated with the frequency shift, .fS, of the resonator sensor and that the common property was the hardness of the tissue. The results indicated that hardness of the prostate tissue, and maybe hardness of human tissue in general, can be expressed according to a cone penetration standard (DIN ISO 2137) and that the hardness can be measured with this tactile sensor system. The tissue hardness application for the resonator sensor technique has to be further developed and evaluated in a larger study. The study also produced results that has led to the basic understanding of the resonator sensor system. One important result was that .fS of the sensor system was related to the contact area between sensor and sample. This indicated that the resonance sensor could be used for contact area measurement.

    In a second part, containing three studies, the area-sensing capability from the first study was utilised in the development and evaluation of the applanation resonator sensor (ARS) for measurement of intraocular pressure (IOP). For the purpose of evaluating IOP-tonometers, an in vitro pig-eye model was developed, and it was shown that a saline column connected to the vitreous chamber could be used successfully to induce variations in IOP.

    A ARS sensor with a flat contact surface was applied onto the cornea with constant force and .fS was measured. A mathematical model based on the Imbert-Fick law and the assumption that .fS was linearly related to contact area was proposed and verified with a convincing result. IOP measured with the ARS correlated well (r=0.92, n=360) with the IOP elicited by a saline column.

    The ARS in a constant-force arrangement was evaluated on healthy human subjects in vivo. The results verified the sensor principle but revealed a nonnegligible source of error in off-centre positioning between the sensor and cornea. The sensor probe was redesigned and evaluated in the in vitro model. The new probe, with a spherical contact surface against the eye reduced the sensitivity to off-centre positioning. It was also shown that a .fS normalisation procedure could reduce the between-eye differences.

    The ARS method for IOP measurement was further developed using combined continuous force and area measurement during the dynamic phase when the sensor initially contacts the cornea. A force sensor was included with the resonator sensor in one probe. Evaluation was performed with the in vitro pig-eye model. The hypothesis was that the IOP could be deduced from the differential change of force and area during that phase. The study showed good accuracy and good reproducibility with a correlation of r=0.994 (n=414) between measured pressure in the vitreous chamber and IOP according to the ARS. Measurement time was short, 77 ms after initial contact. Problems with inter-eye differences and low resolution at high pressures were reduced. The ARS method is the first to combine simultaneous, continuous sampling of both parameters included in the applanation principle. Consequently, there is a potential for reducing errors in the clinical IOP tonometry.

  • 23.
    Eklund, Anders
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Bäcklund, Tomas
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Henein, Michael Y
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology. Heart centrum, Umeå universitet.
    Natural angioplasty as a mechanical effect of exercise2013In: International Journal of Cardiology, ISSN 0167-5273, E-ISSN 1874-1754, Vol. 168, no 3, 3083-3085 p.Article in journal (Refereed)
  • 24.
    Eklund, Anders
    et al.
    Umeå University, Faculty of Medicine, Department of Medical Biosciences.
    Hallberg, Per
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Lindén, Christina
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
    Lindahl, Olof A.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    An applanation resonator sensor for measuring intraocular pressure using combined continuous force and area measurement2003In: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 44, no 7, 3017-3024 p.Article in journal (Refereed)
  • 25.
    Eklund, Anders
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Koskinen, Lars-Owe D
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Neurosurgery.
    Williams, Michael A
    Luciano, Mark G
    Dombrowski, Stephen M
    Malm, Jan
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience.
    Hydrodynamics of the CertasTM programmable valve for the treatment of hydrocephalus2012In: Fluids and barriers of the CNS, ISSN 2045-8118, Vol. 9, no 1, 12- p.Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: The new CertasTM shunt for the treatment of hydrocephalus has seven standard pressure settings that according to the manufacturer range from 36 to 238 mmH2O, and an additional "Virtual Off" setting with an opening pressure >400 mmH2O. Information on actual pressure response and reliability of shunt performance is important in clinical application, especially the "Virtual Off" setting as a non-surgical replacement for shunt ligation. The objective of this study was to evaluate the in-vitro hydrodynamic performance of the CertasTM shunt.

    METHODS: Six new CertasTM shunts with proximal and distal catheters were tested with an automated, computerized test system that raised the pressure from zero to a maximum pressure and back to zero at each valve setting. Opening pressure and flow resistance were determined.

    RESULTS: For settings 1-7 the measured opening pressure range was 26 to 247 mmH2O, and the mean change in opening pressure for a one-step adjustment was between 33 and 38 mmH2O. For setting 8 ("Virtual Off") the measured mean opening pressure was 494 +/- 34 mmH2O (range 451 to 556 mmH2O). The mean outflow resistance was 7.0 mmHg/ml/min (outflow conductance 17.9 ul/s/kPa).

    CONCLUSIONS: The six shunts had similar characteristics and closely matched the manufacturer's specifications for opening pressure at settings 1-7. The opening pressure for the "Virtual Off" setting was nearly 500 mmH2O, which is 100 mmH2O higher than the manufacturer's specification of ">400" and should be functionally off for most patients with communicating hydrocephalus. Clinical studies are needed to evaluate if the CSF dynamic profile persists after implantation in patients.

  • 26.
    Eklund, Anders
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Lindén, Christina
    Umeå University, Faculty of Medicine, Department of Clinical Sciences.
    Bäcklund, Tomas
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Andersson, Britt M
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Lindahl, Olof A
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Evaluation of applanation resonator sensors for intra-ocular pressure measurement: results from clinical and in vitro studies.2003In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 41, no 2, 190-197 p.Article in journal (Refereed)
    Abstract [en]

    Glaucoma is an eye disease that, in its most common form, is characterised by high intra-ocular pressure (IOP), reduced visual field and optic nerve damage. For diagnostic purposes and for follow-up after treatment, it is important to have simple and reliable methods for measuring IOP. Recently, an applanation resonator sensor (ARS) for measuring IOP was introduced and evaluated using an in vitro pig-eye model. In the present study, the first clinical evaluation of the same probe has been carried out, with experiments in vivo on human eyes. There was a low but significant correlation between IOP(ARS) and the IOP measured with a Goldmann applanation tonometer (r = 0.40, p = 0.001, n = 72). However, off-centre positioning of the sensor against the cornea caused a non-negligible source of error. The sensor probe was redesigned to have a spherical, instead of flat, contact surface against the eye and was evaluated in the in vitro model. The new probe showed reduced sensitivity to off-centre positioning, with a decrease in relative deviation from 89% to 11% (1 mm radius). For normalised data, linear regression between IOP(ARS) and direct IOP measurement in the vitreous chamber showed a correlation of r = 0.97 (p < 0.001, n = 108) and a standard deviation for the residuals of SD < or = 2.18 mm Hg (n = 108). It was concluded that a spherical contact surface should be preferred and that further development towards a clinical instrument should focus on probe design and signal analysis.

  • 27.
    Eklund, Anders
    et al.
    Umeå University, Faculty of Medicine, Radiation Sciences.
    Smielewski, Peter
    Chambers, Iain
    Alperin, Noam
    Malm, Jan
    Umeå University, Faculty of Medicine, Pharmacology and Clinical Neuroscience, Neurology.
    Czosnyka, Marek
    Marmarou, Anthony
    Assessment of cerebrospinal fluid outflow resistance.2007In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 45, no 8, 719-735 p.Article in journal (Refereed)
  • 28.
    el Azazi, Mildred
    et al.
    S:t Erik, Stockholm.
    Wang, Ling
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Wachtmeister, Lillemor
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
    Background light adaptation of the retinal neuronal adaptive system. II. Dynamic effects2004In: Documenta Ophthalmologica, ISSN 0012-4486, Vol. 109, no 2, 201-213 p.Article in journal (Refereed)
    Abstract [en]

    The dynamic effects of continuous exposure to light on the neuronal adaptive system of the retina, as indicated by the oscillatory response (OPs) of the electroretinogram (ERG) were studied in the albino rat. Digitally filtered OPs and the a- and b-waves of the corneal ERG were simultaneously recorded in dark adaptation, during continuous light adaptation to four levels of background light (BGL) changing in steps of two log units from 1.43 x 10(-6) cd/m2, referred to as 'low and high scotopic, low and high mesopic' levels. Exposed to 'high scotopic' BGL the total oscillatory response (SOP) significantly enhanced within the first minute, whereas the amplitudes of the a- and b-waves were unaffected. In 'low mesopic' BGL the SOP increased within the first minute, whereas the a- and b-waves significantly decreased. 'High mesopic' BGL instantaneously and profoundly reduced both the SOP and the slow potentials. The individual OPs changed in amplitudes mainly within the first minute of BGL. In general, the earlier OPs (O1 and O2) reacted more to the two 'scotopic' BGL levels, whereas the later OPs (O3 and 04) were more affected by the relatively brighter two 'mesopic' conditions. In conclusion, the rapid increase of the OPs within the first minute of 'high scotopic' and 'low mesopic' BGL exposure may represent a rudimentary light adaptational effect in the rod-dominated rat retina. These findings also suggest that the neuronal adaptive mechanism of the retina seems to be a robust system, probably attaining preservation of visual abilities in the rat on exposure to light.

  • 29.
    Farahmand, Dan
    et al.
    Hydrocephalus Research Unit, Institute of Neuroscience and Physiology, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
    Qvarlander, Sara
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Malm, Jan
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Wikkelsö, Carsten
    Hydrocephalus Research Unit, Institute of Neuroscience and Physiology, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Tisell, Magnus
    Hydrocephalus Research Unit, Institute of Neuroscience and Physiology, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
    Intracranial pressure in hydrocephalus: impact of shunt adjustments and body positions2015In: Journal of Neurology, Neurosurgery and Psychiatry, ISSN 0022-3050, E-ISSN 1468-330X, Vol. 86, no 2, 222-228 p.Article in journal (Refereed)
    Abstract [en]

    Background The association between intracranial pressure (ICP) and different shunt valve opening pressures in relation to body positions is fundamental for understanding the physiological function of the shunt.

    Objective To analyse the ICP and ICP wave amplitude (AMP) at different shunt settings and body positions in patients with hydrocephalus.

    Methods In this prospective study 15 patients with communicating hydrocephalus were implanted with a ligated adjustable ventriculoperitoneal shunt. They also received a portable intraparenchymatous ICP-monitoring device. Postoperative ICP and AMP were recorded with the patients in three different body positions (supine, sitting and walking) and with the shunt ligated and open at high, medium and low valve settings. In each patient 12 10 min segments were coded, blinded and analysed for mean ICP and mean AMP using an automated computer algorithm.

    Results Mean ICP and mean AMP were lower at all three valve settings compared with the ligated shunt state (p<0.001). Overall, when compared with the supine position, mean ICP was 11.5 +/- 1.1 (mean +/- SD) mm Hg lower when sitting and 10.5 +/- 1.1 mm Hg lower when walking (p<0.001). Mean ICP was overall 1.1 mm Hg higher (p=0.042) when walking compared with sitting. The maximal adjustability difference (highest vs lowest valve setting) was 4.4 mm Hg.

    Conclusions Changing from a supine to an upright position reduced ICP while AMP only increased at trend level. Lowering of the shunt valve opening pressure decreased ICP and AMP but the difference in mean ICP in vivo between the highest and lowest opening pressures was less than half that previously observed in vitro.

  • 30.
    Fordell, Helena
    et al.
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Bodin, Kenneth
    Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, High Performance Computing Center North (HPC2N).
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Malm, Jan
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    RehAtt – scanning training for neglect enhanced by multi-sensory stimulation in Virtual Reality2016In: Topics in Stroke Rehabilitation, ISSN 1074-9357, E-ISSN 1945-5119, Vol. 23, no 3, 191-199 p.Article in journal (Refereed)
    Abstract [en]

    Background: There is a lack of effective treatment for neglect. We have developed a new training method, RehAtt (TM). The objective of this study was to determine whether RehAtt (TM) improves spatial attention in chronic neglect after stroke. Methods: RehAtt (TM) consists of a computer with monitor, 3D glasses, and a force feedback interface (Robotic pen) giving sensory motor activation to the contra-lesional arm. The software combines visual scanning training with multi-sensory stimulation in 3D virtual reality (VR) game environment. Fifteen stroke patients with chronic neglect (duration > 6 month) had repeated baseline evaluations to confirm stability of symptoms. There were no test-retest effects for any of the tests. Thereafter, all patients trained 15 h in RehAtt (TM) (3 x 1 h for 5 weeks). A neglect test battery and Catherine Bergego Scale, CBS, were used to assess behavioral outcome after intervention. CBS was also used at a 6-month follow-up. Results: Using repeated measurement analysis improvements due to the training were found for Star cancellation test (p = 0.006), Baking tray task (p < 0.001), and Extinction test (p = 0.05). In the Posner task improvements were seen fewer missed targets (p = 0.024). CBS showed improvements in activities of daily life immediately after training (p < 0.01). After 6 months the patients still reported improvement in CBS. Conclusion: RehAtt (TM) is a new concept for rehabilitation of neglect. Training with the VR-method improved spatial attention and showed transfer to improved spatial attention in activities of daily living in chronic neglect. Our results are promising and merit further studies.

  • 31. Hallberg, Per
    et al.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Bäcklund, Tomas
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Lindén, Christina
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
    Clinical evaluation of applanation resonance tonometry: a comparison with Goldmann applanation tonometry.2007In: Journal of glaucoma, ISSN 1057-0829, E-ISSN 1536-481X, Vol. 16, no 1, 88-93 p.Article in journal (Refereed)
    Abstract [en]

    PURPOSE: The purpose of this study was to calibrate and evaluate the precision of the new applanation resonance tonometry (ART) in a clinical study designed in accordance with the International Standard Organization's requirements. METHODS: This was a prospective, randomized, single-center study, where healthy volunteers and patients participated. A total of 153 eyes were divided into 3 groups with respect to their intraocular pressure (IOP) at screening: <16 mm Hg, 16 to 23 mm Hg, and >23 mm Hg. IOP was measured with Goldmann applanation tonometry (GAT) as reference method and by ART in both a biomicroscope (ARTBiom) and a handheld (ARTHand) setup with a 10-minutes pause between methods. The mean of 6 readings was regarded as one measurement value. RESULTS: Mean age of the subjects was 59 years (range 20 to 87 y). GAT showed a mean IOP of 20.0 mm Hg (range 8.5 to 43.5 mm Hg, n=153). The precision was 2.07 mm Hg for ARTBiom and 2.50 mm Hg for ARTHand, with a significant dependency for age as compared with GAT. Measurement order produced a decreasing IOP with a mean of 2.3 mm Hg between the first and last method. CONCLUSIONS: The precision obtained in both ARTBiom and ARTHand was within the limits set by the International Standard Organization standards for tonometers. The standardized procedure and the stability of the biomicroscope setup resulted in a slightly better precision as compared with the handheld setup. Despite a 10-minutes pause between measurements, the order was a significant factor, possibly because the patients were more apprehensive at the first measurement.

  • 32.
    Hallberg, Per
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Santala, Kenneth
    Koskela, Timo
    Lindahl, Olof A.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Lindén, Christina
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
    Underestimation of intraocular pressure after photorefractive keratectomy - a biomechanical analysisArticle in journal (Refereed)
  • 33. Hallberg, Per
    et al.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Santala, Kenneth
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
    Koskela, Timo
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
    Lindahl, Olof
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Lindén, Christina
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
    Underestimation of intraocular pressure after photorefractive keratectomy: a biomechanical analysis2006In: Med Biol Eng Comput, Vol. 44, 609-168 p.Article in journal (Refereed)
    Abstract [en]

    Excimer laser surgery, to correct corneal refraction, induces changes in corneal thickness and curvature. Both factors can cause measurement errors when determining intraocular pressure (IOP). This study evaluates effects of photorefractive keratectomy (PRK) on IOP measurements, using Goldmann applanation tonometry (GAT) and Applanation resonance tonometry (ART), in an in vitro model. Six porcine eyes was enucleated and pressurised to a constant IOP=30 mmHg. After removal of the epithelium, the eyes were PRK-treated for a total of 25 dioptres. The measured IOP decreased 13.2 mmHg for GAT and 9.0 mmHg for ART. The total underestimation by GAT was larger than for ART, and a part of the ART underestimation (3.5 mmHg) was assigned to sensitivity to the change in corneal surface structure resulting from the removal of epithelium. The flat contact probe of GAT, as compared with the convex tip of ART, provided explanation for the difference in IOP measurement error after PRK.

  • 34.
    Hallberg, Per
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Lindén, Christina
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
    Bäcklund, Tomas
    Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Symmetric sensor for applanation resonance tonometry of the eye2006In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 44, no 1-2, 54-60 p.Article in journal (Refereed)
    Abstract [en]

    Applanation resonance tonometry (ART) has been shown in a number of studies to be useful for measuring intraocular pressure (IOP). Data from in vitro laboratory bench testing, where the sensor was carefully centralised onto the cornea, has been very consistent with good precision in the determination of IOP. However, in a clinical study the unavoidable off-centre placement of the sensor against the cornea resulted in a reduced precision. The aim of this study was to evaluate a new design of the sensor with a symmetric sensor probe and a contact piece with a larger diameter. Two in vitro porcine eye experimental set-ups were used. One bench-based for examining position dependence and one biomicroscope-based set-up, simulating a clinical setting, for evaluating IOP(ART) precision at seven different pressure levels (1040 mmHg), set by connecting a saline column to the vitreous chamber. The reference IOP was recorded using a pressure transducer. There was no significant difference between four positions 1 mm off centre and the one centre position. The precision of the ART as compared with the reference pressure was +/- 1.03 mmHg (SD, n = 42). The design improvement has enhanced the precision of the ART in the biomicroscope set-up to be in parity with bench test results from a set-up using perfect positioning. This indicates that off-centre positioning was no longer a major contributor to the deviations in measured IOP. The precision was well within the limits set by ISO standard for eye tonometers. Therefore, a larger in vivo study on human eyes with the ART should be performed.

  • 35.
    Hallberg, Per
    et al.
    Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Lindén, Christina
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
    Lindahl, Olof A.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Bäcklund, Tomas
    Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Eklund, Anders
    Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Applanation resonance tonometry for intraocular pressure in humans2004In: Physiological Measurement, ISSN 0967-3334, E-ISSN 1361-6579, Vol. 25, no 4, 1053-1065 p.Article in journal (Refereed)
    Abstract [en]

    Glaucoma is a group of diseases associated with optic nerve damage and loss of visual field. The aetiology is not completely understood, but one of the major risk factors is elevated intraocular pressure (IOP). Reliable methods for measuring the IOP are therefore important. The aim of the study was to investigate the ability of the applanation resonance tonometry (ART) system, based on continuous force and area recording, to measure IOP in humans. Both the phase of initial indentation (IOPIndentation) and the phase when the sensor was removed (IOPRemoval) from the cornea were analysed. The Goldmann applanation tonometry (GAT) was used as reference method. The study included 24 healthy volunteers with normal IOP and 24 patients with elevated IOP. The correlation and standard deviation (SD) between IOPIndentation and IOPGAT was R = 0.92 (p < 0.001), SD = 3.6 mmHg, n = 104, and between IOPRemoval and IOPGAT R = 0.94 (p < 0.001), SD = 3.1 mmHg, n = 104. In conclusion, resonance sensor technology has made it possible to introduce a new multi-point method for measuring IOP, and the method is relevant for measuring IOP in humans. The study indicates that with further development towards elimination of position dependence, the ART has the potential to become a useful clinical instrument for IOP measurement.

  • 36.
    Hallberg, Per
    et al.
    Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Santala, Kenneth
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
    Lindén, Christina
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
    Lindahl, Olof A
    Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF). Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Comparison of Goldmann applanation and applanation resonance tonometry in a biomicroscope-based in vitro porcine eye model2006In: J Med Eng Technol, ISSN 0309-1902, Vol. 30, no 6, 345-352 p.Article in journal (Refereed)
  • 37.
    Israelsson, Hanna
    et al.
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Allard, Per
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Psychiatry.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Malm, Jan
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Symptoms of Depression are Common in Patients With Idiopathic Normal Pressure Hydrocephalus: The INPH-CRasH Study2016In: Neurosurgery, ISSN 0148-396X, E-ISSN 1524-4040, Vol. 78, no 2, 161-168 p.Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: If patients with idiopathic normal pressure hydrocephalus (INPH) also have depression, this could have important clinical ramifications in assessment and management of their cognitive function and response to shunting. In many dementias, depression is overrepresented, but the prevalence of depression in shunted patients with INPH is unknown.

    OBJECTIVE: The objective of this case-control study was to assess the prevalence of symptoms of depression in shunted INPH patients compared with population-based controls.

    METHODS: INPH patients consecutively shunted from 2008 to 2010 in Sweden were analyzed. Patients remaining after inclusion (within 60-85 years and not having dementia, ie, mini-mental state examination >=23) had a standardized visit to their healthcare provider and answered an extensive questionnaire. Age- and sex-matched population-based controls underwent the same procedure. Symptoms of depression were assessed using the Geriatric Depression Scale 15 (suspected depression defined as >=5 points, suspected severe depression as >=12 points). This study is part of the INPH-CRasH study.

    RESULTS: One hundred seventy-six INPH patients and 368 controls participated. After adjustment for age, sex, cerebrovascular disease, and systolic and diastolic blood pressure, patients had a higher mean depression score (patients: 4.9 ± 3.7 SD, controls: 1.9 ± 2.3 SD; OR 1.4, 95% CI 1.3-1.6, P < .001), more patients had suspected depression (46% vs 13%, OR 6.4, 95% CI 3.8-10.9, P < .001), and more patients had suspected severe depression (7.3% vs 0.6%, OR 14.4, 95% CI 3.0-68.6, P < .005).

    CONCLUSION: Symptoms of depression are overrepresented in INPH patients compared with the population, despite treatment with a shunt. Screening for depression should be done in the evaluation of INPH patients in order to find and treat a coexisting depression.

  • 38.
    Israelsson, Hanna
    et al.
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience.
    Birgander, Richard
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology.
    Ambarki, Khalid
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Malm, Jan
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience.
    Ventriculomegaly and balance disturbances in patients with TIA2012In: Acta Neurologica Scandinavica, ISSN 0001-6314, E-ISSN 1600-0404, Vol. 125, no 3, 163-170 p.Article in journal (Refereed)
    Abstract [en]

    Objectives -  Dilated ventricles and gait disturbances are common in the elderly, and these are also features of the treatable syndrome idiopathic normal pressure hydrocephalus (INPH). Many studies report an association between hypertension, vascular disease and INPH. The objective of this study was to study the frequency of ventriculomegaly, with or without hydrocephalic symptoms, in patients who had suffered from a transitory ischaemic attack (TIA).

    Methods -  Gait, Romberg sign, tandem standing and one-leg stance were consecutively evaluated in elderly >24 h after a TIA. Ventricular size, white matter lesions and atrophy were assessed on computed tomography scans. Exclusion criteria were conditions possibly influencing the balance tests.

    Results -  Seventy-six patients with TIA out of 105 were included. Ventriculomegaly [Evans Index (EI) > 0.30] was observed in 19.7% and very large ventricles (EI > 0.33) in 7.9%. Ventriculomegaly was found in 58% of the patients with a previous 'history of balance or gait disturbance', but only in 12% of those without any prior disturbance (chi-square test; P = 0.0009). Three out of 76 patients with TIA (3.9%) fulfilled both radiological and clinical criteria for 'possible INPH'.

    Conclusion -  Ventriculomegaly is a common finding in elderly. One out of 20 patients with TIA may suffer from INPH, existing before and independent of the TIA diagnosis. Therefore, patients presenting with ventriculomegaly and gait/balance disturbances not attributable to other causes should be referred to a hydrocephalus centre or a neurologist with special interest in INPH.

  • 39.
    Israelsson, Hanna
    et al.
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience. Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Carlberg, Bo
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine.
    Wikkelsö, Carsten
    Laurell, Katarina
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience.
    Kahlon, Babar
    Leijon, Göran
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Malm, Jan
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience.
    Vascular risk factors contribute to idiopathic normal pressure hydrocephalus: the INPH-CRasH StudyManuscript (preprint) (Other academic)
    Abstract [en]

    Objective

    The objective was to determine the complete modern vascular risk factor (VRF) profile of idiopathic normal pressure hydrocephalus (INPH) using a large sample of representative INPH-patients and population-based controls, in order to confirm the impact of vascular disease on INPH pathophysiology.

     

    Methods

    All shunted INPH-patients in Sweden 2008-2010 were compared to age- and gender-matched population-based controls. Inclusion criteria: 60-85 years and mini mental state estimation ³23. The ten most important modern VRFs as well as cerebrovascular and peripheral vascular disease were prospectively assessed through blood samples, by-protocol clinical examinations and standardized questionnaires. Investigated VRFs: hypertension, hyperlipidemia, diabetes, obesity, psychosocial factors, smoking, diet, alcohol intake, cardiac disease and, physical activity.

     

    Results

    After exclusion, 176 INPH-patients and 368 controls participated. Using multivariable logistic regression, hyperlipidemia (OR: 2.380, 95%CI: 1.434-3.950), diabetes (OR: 2.169, 95%CI: 1.195-3.938), obesity (OR: 5.428, 95%CI: 2.502-11.772) and, psychosocial factors (OR: 5.343, 95%CI: 3.219-8.868) were independently associated with INPH. Hypertension, physical inactivity, cerebrovascular and peripheral vascular disease were overrepresented in INPH, although not independently. The protective factors: moderate alcohol intake and physical activity were overrepresented among the controls. The population attributable risk percentage was 24%.

     

    Conclusions

    Our findings confirm that INPH-patients have a more dangerous VRF-profile and lack the protective factors present in the population. Almost one quarter of INPH could be explained by VRF, suggesting that INPH possibly may be a subgroup of vascular dementia. Targeted interventions against modifiable VRF are likely to have beneficial effects in INPH.

  • 40.
    Israelsson, Hanna
    et al.
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Malm, Jan
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience.
    CSF shunting improves long-term quality of life in idiopathic normal pressure hydrocephalus: the INPH-CRasH StudyManuscript (preprint) (Other academic)
    Abstract [en]

    Introduction

    Measurements of quality of life (QoL) are important when evaluating a surgical method. However, QoL after shunting in idiopathic normal pressure hydrocephalus (INPH) is seldom assessed. The objective of this study was to assess QoL in a large cohort of shunted INPH patients, compared to the population, and investigate which factors influence QoL in INPH.

     

    Methods

    All INPH patients shunted in Sweden 2008-2010 were scrutinized. Population-based controls were age- and gender-matched to the patients. One hundred and seventy-six INPH patients and 368 controls were included. QoL was assessed using the EQ5D5L instrument, measuring overall QoL and health status in five dimensions. Independency, measured by accommodation and need for in-home care, and comorbidities were assessed. Patients were followed up 6-45 months after surgery (mean follow-up time: 21 months).

     

    Results

    Shunted INPH patients had lower QoL than controls (p<0.001). The patients’ health status in mobility, self-care, daily activities, and anxiety/depression was worse than the controls both before and after surgery (p<0.001). Shunting improved QoL (p<0.001) and health status in all dimensions (p<0.005). The main predictors of low QoL in INPH were depression (p<0.001) and severity of gait disturbance (p=0.001). Fewer INPH patients than controls lived independently (45% vs 85%, p<0.001) Time after shunting had no influence on QoL.

     

    Interpretation

    Improvement in QoL after shunting in INPH is long lasting, but shunted INPH patients do not reach the same level of QoL as the population. Depression and severity of gait disturbance are the strongest predictors of low QoL in INPH. 

  • 41.
    Johannesson, Gauti
    et al.
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
    Hallberg, Per
    Umeå University, Faculty of Medicine, Department of Radiation Sciences. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Ambarki, Khalid
    Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF). Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Eklund, Anders
    Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF). Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Linden, Christina
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
    Age-dependency of ocular parameters - a cross sectional study of young and old healthy subjects2015In: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 56, no 7, Meeting Abstract: 116Article in journal (Other academic)
    Abstract [en]

    Purpose: To investigate aging effect on ocular parameters inkluding intraocular pressure (IOP) measured with different tonometry methods in healthy young (HY) and elderly (HE) subjects.

    Methods: Fifty eyes of 50 HY subjects (28 females, 22-31 years of age) and 43 eyes of 43 HE subjects (22 females, 64-79 years of age) were included. IOP was measured with four tonometry methods in a standardized order: Ocular Response Analyser (ORA), Dynamic Contour Tonometry (DCT), Applanation Resonance Tonometry (ART) and Goldmann Applanation Tonometry (GAT). Other measurements included axial length (AL), central corneal thickness (CCT), corneal curvature (CC), ocular pulse amplitude (OPA) and aqueous humor (aq).

    Results: The mean IOP (HY/HE; mmHg ± standard deviation) was 13.9 ± 2.7/16.4 ± 3.4 with ORA, 15.1 ± 2.1/16.3 ± 3.1 with DCT, 12.3 ± 2.0/13.7 ± 2.8 with GAT and 13.1 ± 2.2/12.1 ± 2.5 with ART. IOP was significantly higher (difference ± standard error) in HE compared to HY measured with ORA (+2.5 mmHg ± 0.6), GAT (+1.4 ± 0.5) and DCT (+1.2 ± 0.6). There was a trend towards lower IOP in HE when measured with ART (-1.0 ± 0.5, p=0.05). There was no difference between HE and HY in CCT, CC, AL or OPA.

    Conclusions: Tonometry methods are affected differently by age. IOP was measured higher in elderly people with ORA, DCT and GAT in this Scandinavian population. This effect was not seen in measurements with ART. Other ocular parameters did not differ between the age groups indicating that these measured parameters are not influenced by age in this population.

  • 42.
    Johannesson, Gauti
    et al.
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
    Hallberg, Per
    Umeå University, Faculty of Medicine, Department of Radiation Sciences. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Ambarki, Khalid
    Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF). Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Eklund, Anders
    Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF). Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Linden, Christina
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
    Age-dependency of ocular parameters: a cross sectional study of young and elderly healthy subjects2015In: Graefe's Archives for Clinical and Experimental Ophthalmology, ISSN 0721-832X, E-ISSN 1435-702X, Vol. 253, no 11, 1979-1983 p.Article in journal (Refereed)
    Abstract [en]

    To investigate the effect of aging on ocular parameters, including intraocular pressure (IOP), measured with different tonometry methods in healthy young (HY) and healthy elderly (HE) subjects and to study the effect of corneal parameters on tonometry methods. In this prospective, cross-sectional study, fifty eyes of 50 HY subjects (28 females, 22-31 years of age) and 43 eyes of 43 HE subjects (22 females, 64-79) were included. IOP was measured with four tonometry methods in a standardized order: ocular response analyser (ORA), dynamic contour tonometry (DCT), applanation resonance tonometry (ART) and Goldmann applanation tonometry (GAT). Other measurements included axial length (AL), central corneal thickness (CCT), corneal curvature (CC), anterior chamber volume (ACV), corneal hysteresis (CH) and corneal resistance factor (CRF). The mean IOP (HY/HE; mmHg +/- standard deviation (SD)) was 12.2 +/- 2.2/14.1 +/- 3.5 with GAT. IOP was significantly higher (difference +/- standard error) in HE compared to HY measured with an ORA (+3.1 mmHg +/- 0.6), GAT (+1.9 +/- 0.6) and DCT (+1.6 +/- 0.6). No significant difference was found in IOP measured with ART. CH and ACV were significantly lower in HE compared to HY. There was no difference between the groups in CCT, CC, AL or CRF. No tonometry method was dependant on CCT or CC. IOP measured with an ORA and via DCT and GAT was higher in HE compared to HY Swedish subjects, while IOP measured with ART did not differ between the groups. In these homogeneous groups, tonometry methods were independent of CCT and CC.

  • 43.
    Johannesson, Gauti
    et al.
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
    Hallberg, Per
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Behndig, Anders
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
    Linden, Christina
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
    Effects of topical anaesthetics and repeated tonometry on intraocular pressure2014In: Acta Ophthalmologica, ISSN 1755-375X, E-ISSN 1755-3768, Vol. 92, no 2, 111-115 p.Article in journal (Refereed)
    Abstract [en]

    Purpose:

    To investigate the effects of repeated measurements of intraocular pressure (IOP) using Goldmann applanation tonometry (GAT) and applanation resonance tonometry (ART) to identify mechanisms contributing to the expected IOP reduction.

    Methods:

    A prospective, single-centre study with six healthy volunteers. Consecutive repeated series (six measurements/serie/method) were made alternately on both eyes for 1 hr with oxybuprocaine/fluorescein in the right eye and tetracaine in the left. The left eye was Pentacam((R)) photographed before and repeatedly for 20 min after the IOP measurements. On a separate occasion, the same volunteers received the same amount of anaesthetic drops for 1 hr but without repeated IOP measurements.

    Results:

    A significant IOP reduction occurred with both ART and GAT in the oxybuprocaine-treated eye, -4.4 mmHg and -3.8 mmHg, respectively and with ART in the tetracaine eye, -2.1 mmHg. There was a significant difference in IOP reduction between the oxybuprocaine and tetracaine eyes with ART. There was a significant drop in anterior chamber volume (ACV) immediately after the IOP measurements, -12.6 mu l that returned to pretrial level after 2 min. After 1 hr of receiving anaesthetic eye drops (without IOP measurements), the IOP decreased significantly in the oxybuprocaine eye for both ART and GAT, -3.1 and -1.7 mmHg, respectively, but not in the tetracaine eye (p = 0.72).

    Conclusion:

    The IOP reduction cannot be explained solely by aqueous humor being pressed out of the anterior chamber. While significant IOP reduction occurred with both tetracaine and oxybuprocaine after repeated mechanical applanation, the IOP reduction was significantly greater with oxybuprocaine.

  • 44.
    Johannesson, Gauti
    et al.
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
    Hallberg, Per
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Koskela, Timo
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
    Linden, Christina
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
    Change in intraocular pressure measurement 2 years after myopic laser-assisted subepithelial keratectomy2012In: Journal of cataract and refractive surgery, ISSN 0886-3350, E-ISSN 1873-4502, Vol. 38, no 9, 1637-1642 p.Article in journal (Refereed)
    Abstract [en]

    PURPOSE: To evaluate intraocular pressure (IOP) measurements 24 months after laser-assisted subepithelial keratectomy (LASEK) with 3 tonometry methods-Goldmann applanation tonometry (DCT), Pascal dynamic contour tonometry (DCT), and applanation resonance tonometry (ART)-and to compare them with measurements taken preoperatively and 3 and 6 months postoperatively. SETTING: Department of Ophthalmology, Umea University, lima Sweden. DESIGN: Prospective randomized single-center. METHODS: One randomized eye per person from myopic healthy individuals who had LASEK was included. Visual acuity, central corneal thickness (CCT), corneal curvature, and IOP were measured at all time points. Six IOP measurements were performed per method, with a 5-minute lapse between methods. RESULTS: The study evaluated 38 eyes. Two years after LASEK, dynamic ART was the only method that did not measure significantly lower IOP than before LASEK (mean -0.2 mm Hg +/- 1.6 [SD]). The greatest difference was with GAT (mean -1.9 +/- 1.7 mm Hg) followed by static ART (mean -1.2 +/- 1.6 mm Hg) and then DCT (mean -0.9 +/- 1.3 mm Hg). All methods measured significantly lower IOP at 3 months and 6 months. CONCLUSIONS: Dynamic ART, which analyses IOP measurement during indentation, showed no significant difference in measured IOP after 24 months. The convex tip of the ART device and the continuous sampling of data during corneal indentation seem to be factors in why dynamic ART was less affected by corneal properties and therefore more suitable for IOP measurement in LASEK-treated eyes, although this must be confirmed in larger trials.

  • 45. Johansson, Staffan B.
    et al.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Malm, Jan
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Stemme, Göran
    Roxhed, Niclas
    A MEMS-based passive hydrocephalus shunt for body position controlled intracranial pressure regulation2014In: Biomedical microdevices (Print), ISSN 1387-2176, E-ISSN 1572-8781, Vol. 16, no 4, 529-536 p.Article in journal (Refereed)
    Abstract [en]

    This paper reports a novel micro electro mechanical system (MEMS) valve with posture controlled flow characteristics for improved treatment of hydrocephalus, a disease that is characterized by elevated pressure in the cerebrospinal fluid (CSF) that surrounds the brain and spinal cord. In contrast to conventional differential pressure CSF valves, the CSF valve presented here features a third port which utilizes hydrostatic pressure from a pressure compensating catheter to adapt CSF drainage to optimized levels irrespective of body position. Prototypes have been fabricated using standard MEMS manufacturing processes and the experimental evaluation successfully showed that the flow rate was adjustable with a varying hydrostatic pressure on the third port. Measured data showed that flow rate was at near ideal values at laying body position and that the flow rate can be adjusted to optimal values at standing body position by selecting an appropriate length of the pressure compensating catheter. This is the first pressure balanced CSF valve intended for body position controlled CSF pressure regulation.

  • 46.
    Jóhannesson, Gauti
    et al.
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
    Hallberg, Per
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Koskela, Timo
    Lindén, Christina
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
    Change in intraocular pressure measurement after myopic LASEK: a study evaluating Goldmann, Pascal and applanation resonance tonometry2012In: Journal of glaucoma, ISSN 1057-0829, E-ISSN 1536-481X, Vol. 21, no 4, 255-259 p.Article in journal (Refereed)
    Abstract [en]

    PURPOSE: To prospectively evaluate 3 tonometry methods-the gold standard, Goldmann applanation tonometry, a new method, Pascal dynamic contour tonometry (PDCT), and a method under development, applanation resonance tonometry (ART)-with respect to intraocular pressure (IOP) measurements before, 3 and 6 months after laser-assisted subepithelial keratectomy (LASEK).

    MATERIALS AND METHODS: One randomly assigned eye of each of 53 healthy individuals, who underwent LASEK surgery for myopia was studied. Visual acuity, central corneal thickness, corneal curvature, and IOP were measured at each visit. Six IOP measurements/methods with 5 minutes pause between methods were performed.

    RESULTS: All tonometry methods measured a significantly lower IOP after LASEK correction by a mean of -3.1 diopters. The IOP reduction was largest after 6 months for Goldmann applanation tonometry (-1.7±1.8 mm Hg) followed by ARTstat (-1.2±1.5 mm Hg), PDCT (-1.1±1.6 mm Hg), and ARTdyn (-1.0±1.5 mm Hg). The reduction of IOP did not differ significantly between different methods (P=0.11). There was a significant further reduction of measured IOP for PDCT between 3 and 6 months (-0.5±1.0 mm Hg). Uncorrected visual acuity improved significantly between 3 and 6 months postoperatively from 1.32±0.28 to 1.43±0.27.

    CONCLUSIONS: All tonometry methods measured a significant, but low, reduction of IOP 3 and 6 months after LASEK. Further change in visual acuity and IOP measurements between 3 and 6 months suggest a still ongoing postoperative process.

  • 47.
    Jóhannesson, Gauti
    et al.
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
    Hallberg, Per
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Lindén, Christina
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
    Introduction and clinical evaluation of servo-controlled applanation resonance tonometry2012In: Acta Ophthalmologica Scandinavica, ISSN 1395-3907, E-ISSN 1600-0420, Vol. 90, no 7, 677-682 p.Article in journal (Refereed)
    Abstract [en]

    Purpose:  In recent years, Applanation Resonance Tonometry (ART) has been suggested for intraocular pressure (IOP) measurements. The manual version of ART (ARTmanual) has been further developed, and to improve usability, an automatic servo-controlled prototype (ARTservo) has been proposed. The aim of this study was to assess the limits of agreement (LoA) of ARTmanual and ARTservo as compared with the reference method, Goldmann Applanation Tonometry (GAT).

    Methods:  This was a prospective single-centre study on 152 eyes from 77 subjects. It was designed according to International Standard Organization’s (ISO) requirements for tonometers (ISO 2001). Intraocular pressure was measured six times/method in a standardized order. The ART technique has two available analysis procedures: a dynamic one that measures IOP during the indentation phase and a static one that causes a Goldmann-like measurement during two seconds of full applanation. The 95% LoA was defined as ±1.96 × standard deviation of difference against GAT.

    Results:  Mean IOP for GAT was 19.1 mmHg (range: 10–37 mmHg). The 95% LoA of ARTmanual was ±4.5 mmHg for both dynamic and static analyses. The 95% LoA of ARTservo was ±5.7 mmHg for dynamic and ±4.9 mmHg for static analyses.

    Conclusions:  This study confirms that the ART methodology is feasible. The further developed ARTmanual fulfilled the ISO standard with both the dynamic and the static analysis techniques. ARTservo with static analysis was close to fulfilling the standard but failed to do so in the highest IOP range. ARTservo has the potential to greatly improve usability if further development is completed.

  • 48.
    Jóhannesson, Gauti
    et al.
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
    Hallberg, Per
    Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Lindén, Christina
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
    Pascal, ICare and Goldmann applanation tonometry: a comparative study2008In: Acta ophthalmologica, ISSN 1755-3768, Vol. 86, no 6, 614-621 p.Article in journal (Refereed)
    Abstract [en]

    PURPOSE: To compare intraocular pressure (IOP) measurements by Pascal, ICare and Goldmann applanation tonometry (GAT), to evaluate the effects of central corneal thickness (CCT) and curvature on IOP measurement and to estimate the intra-observer variability.

    METHODS: A prospective, single-centre study of 150 eyes with a wide range of pressures. Six masked IOP measurements/method; corneal thickness and curvature were studied for each eye. GAT was the reference.

    RESULTS: IOPPascal and IOPICare correlated with IOPGAT (r = 0.91, 0.89). Mean ICare measurement exceeded GAT by 2 mmHg. Pascal measured higher than GAT at low IOPs and lower at high IOPs. For every 10 mmHg increase in IOP above 31 mmHg, Pascal measured 2 mmHg lower than GAT and vice versa. CCT was correlated significantly with IOPGAT (r = 0.23) and IOPICare (r = 0.43) but not with IOPPascal (P = 0.12). CCT was correlated with age. In a subgroup (>50 years), ICare and the difference between IOPGAT and IOPPascal were affected significantly by the CCT, whereas IOPGAT and IOPPascal were not. Corneal curvature was correlated significantly with IOPGAT (r = -0.27) and IOPPascal (r = -0.26) but not with IOPICare (P = 0.60). Intra-observer variability within each set of six measurements was approximately 2 mmHg, irrespective of method.

    CONCLUSION: This study showed a reasonable overall correlation and concordance between the IOP obtained with the three instruments. None of the methods were completely independent of the biomechanical properties of the cornea. ICare showed a significant dependency upon CCT, whereas GAT and Pascal showed a significant dependency on corneal curvature. All methods showed intra-observer variability, which leaves room for further improvement of methods.

  • 49.
    Jóhannesson, Gauti
    et al.
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
    Hallberg, Per
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Koskela, Timo
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Lindén, Christina
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
    Change in intraocular pressure measurement after myopic LASEK: a study evaluating Goldmann, Pascal and applanation resonance tonometryArticle in journal (Refereed)
  • 50.
    Jóhannesson, Gauti
    et al.
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
    Lindén, Christina
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Behndig, Anders
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
    Hallberg, Per
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Can we trust intraocular pressure measurements in eyes with intracameral air?2014In: Graefe's Archives for Clinical and Experimental Ophthalmology, ISSN 0721-832X, E-ISSN 1435-702X, Vol. 252, no 10, 1607-1610 p.Article in journal (Refereed)
    Abstract [en]

    PURPOSE: To evaluate the effect of intracameral air on intraocular pressure (IOP) measurements using Goldmann applanation tonometry (GAT) and applanation resonance tonometry (ART) in an in-vitro porcine eye model.

    METHODS: IOP was measured on thirteen freshly enucleated eyes at three reference pressures: 20, 30, and 40 mmHg. Six measurements/method were performed in a standardized order with GAT and ART respectively. Air was injected intracamerally in the same manner as during Descemet's stripping endothelial keratoplasty (DSEK) and Descemet's membrane endothelial keratoplasty (DMEK), and the measurements were repeated.

    RESULTS: Measured IOP increased significantly for both tonometry methods after air injection: 0.7 ± 2.1 mmHg for GAT and 10.6 ± 4.9 mmHg for ART. This difference was significant at each reference pressure for ART but not for GAT.

    CONCLUSIONS: Although slightly affected, this study suggests that we can trust GAT IOP-measurements in eyes with intracameral air, such as after DSEK/DMEK operations. Ultrasound-based methods such as ART should not be used.

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