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  • 251.
    Vågberg, Mattias
    et al.
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Lindqvist, T.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology.
    Ambarki, Khalid
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology. 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).
    Warntjes, J. B. M.
    Sundström, Peter
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Birgander, Richard
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology.
    Svenningsson, Anders
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Automated Determination of Brain Parenchymal Fraction in Multiple Sclerosis2013In: American Journal of Neuroradiology, ISSN 0195-6108, E-ISSN 1936-959X, Vol. 34, no 3, p. 498-504Article in journal (Refereed)
    Abstract [en]

    BACKGROUND AND PURPOSE: Brain atrophy is a manifestation of tissue damage in MS. Reduction in brain parenchymal fraction is an accepted marker of brain atrophy. In this study, the approach of synthetic tissue mapping was applied, in which brain parenchymal fraction was automatically calculated based on absolute quantification of the tissue relaxation rates R1 and R2 and the proton attenuation. MATERIALS AND METHODS: The BPF values of 99 patients with MS and 35 control subjects were determined by using SyMap and tested in relationship to clinical variables. A subset of 5 patients with MS and 5 control subjects were also analyzed with a manual segmentation technique as a reference. Reproducibility of SyMap was assessed in a separate group of 6 healthy subjects, each scanned 6 consecutive times. RESULTS: Patients with MS had significantly lower BPF (0.852 0.0041, mean +/- SE) compared with control subjects (0.890 +/- 0.0040). Significant linear relationships between BPF and age, disease duration, and Expanded Disability Status Scale scores were observed (P < .001). A strong correlation existed between SyMap and the reference method (r = 0.96; P < .001) with no significant difference in mean BPF. Coefficient of variation of repeated SyMap BPF measurements was 0.45%. Scan time was <6 minutes, and postprocessing time was <2 minutes. CONCLUSIONS: SyMap is a valid and reproducible method for determining BPF in MS within a clinically acceptable scan time and postprocessing time. Results are highly congruent with those described using other methods and show high agreement with the manual reference method.

  • 252.
    Vågberg, Mattias
    et al.
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience.
    Lindqvist, T.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology.
    Birgander, R.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology.
    Svenningsson, Anders
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Brain parenchymal fraction in the healthy - determined by MRI in an age stratified population and via a systematic review of the literature2014In: Multiple Sclerosis, ISSN 1352-4585, E-ISSN 1477-0970, Vol. 20, no Supplement 1, p. 259-259Article in journal (Other academic)
  • 253.
    Waldner, Rikard
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    ConvNet Pap Smear Single Cell Image Classifier - Deep Learning for automatic image-based diagnosis of histological cervix pap smears2018Independent thesis Basic level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 254.
    Wallstén, Elin
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Axelsson, Jan
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Karlsson, Mikael
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Riklund, Katrine
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology.
    Larsson, Anne
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    A Study of Dynamic PET Frame-Binning on the Reference Logan Binding Potential2017In: IEEE Transactions on Radiation and Plasma Medical Sciences, ISSN 2469-7311, Vol. 1, no 2, p. 128-135Article in journal (Refereed)
    Abstract [en]

    Objective: The reference Logan plot is a tool for determining the non-displaceable binding potential for dynamic PET exams using tracers with reversible bindings. Dynamic frame protocols affect noise in PET images and short frames can lead to quantitative uncertainties and noise-induced reconstruction bias. The aim of this study was to analyze the effect of frame binning on 11C-Raclopride striatal binding potential from reference Logan analysis. Methods: 12 healthy volunteers were scanned in list mode using 11C-raclopride, and the image data were reconstructed into 9 different frame binning schemes whereof 3 clinical schemes. Reconstruction was performed with 3 different algorithms, one based on filtered back projection (FBP) and two based on ordered subset expectation maximization (OSEM); one including resolution recovery. Logan plots were used for calculating the non-displaceable binding potential. Variation in binding potential was evaluated using Students t-tests. Results: It was found that frame lengths of up to 60 s gave significantly different results compared to the reference clinical protocol for OSEM, both with and without resolution recovery (maximum deviation: 10.3 % for the 15 s protocol). For FBP, frame lengths of up to 30 s gave significantly different results with a maximum deviation of 2.8 %. The higher sampling dependence of OSEM compared to FBP is likely due to noise-dependent bias in the OSEM algorithm, most apparent at high noise levels. Conclusions: Bias related to OSEM reconstruction of high-noise data is an important factor for dynamic PET protocols. Time frames of 120 s or more generate the most stable values for the striatum binding potential with the reference Logan plot for 11C-Raclopride brain PET.

  • 255.
    Wallstén, Elin
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Axelsson, Jan
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Karlsson, Mikael
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Riklund, Katrine
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Nyberg, Lars
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Häggström, I.
    Larsson, Anne
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    The Influence of Time Sampling on Parameters in the Logan Plot2013In: 2013 IEEE NUCLEAR SCIENCE SYMPOSIUM AND MEDICAL IMAGING CONFERENCE (NSS/MIC), 2013Conference paper (Refereed)
    Abstract [en]

    The Logan plot is a graphical method for reversible tracer bindings. The bias and uncertainties of this method have previously been analyzed with respect to noise, but little is known about the direct effects from varying the time sampling scheme. This study aims to investigate the effect of time sampling on the binding potential from the reference Logan plot. Image data from seven healthy subjects imaged with [11C]raclopride was reconstructed into six dynamic series of equal length time frames with frame times between 15 s and 480 s. Images were reconstructed using both filtered back projection (FBP) and a resolution enhanced ordered subset expectation maximization (OSEM) algorithm, SharpIR. For each sampling scheme, the nondisplaceable binding potential (BPND) parameter was calculated from the reference Logan plot with cerebellum as a reference region. The variation in BPND was analyzed as percentage deviations from the BPND for the 480 s scheme. R-2 of the linear fit was also analyzed. Comparison between all sampling schemes showed that the largest deviation in BPND was 7.4% between the 15 s sampling scheme and the 480 s sampling scheme reconstructed with SharpIR. The corresponding deviation for FBP images was 1.6%. R-2 was highest for long time frames, but all R-2 values were above 0.997 in this study.

  • 256.
    Wennstig, Anna-Karin
    et al.
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Surgery. Department of Oncology, Sundsvall Hospital, Sundsvall, Sweden.
    Garmo, Hans
    Isacsson, Ulf
    Gagliardi, Giovanna
    Rintelae, Niina
    Lagerqvist, Bo
    Holmberg, Lars
    Blomqvist, Carl
    Sund, Malin
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Surgery.
    Nilsson, Greger
    The relationship between radiation doses to coronary arteries and location of coronary stenosis requiring intervention in breast cancer survivors2019In: Radiation Oncology, ISSN 1748-717X, E-ISSN 1748-717X, Vol. 14, article id 40Article in journal (Refereed)
    Abstract [en]

    BackgroundTo assess the relationship between radiation doses to the coronary arteries (CAs) and location of a coronary stenosis that required intervention after three-dimensional conformal radiotherapy (3DCRT) for breast cancer (BC).MethodsThe study population consisted of 182 women treated for BC in Sweden between 1992 and 2012. All women received 3DCRT and subsequently underwent coronary angiography due to a suspected coronary event. CA segments were delineated in the patient's original planning-CT and radiation doses were recalculated based on the dose distribution of the original radiotherapy (RT) plan. The location of the CA stenosis that required intervention was identified from the Swedish Coronary Angiography and Angioplasty Registry (SCAAR). Logistic regression analysis was used to assess the relationship between CA radiation doses and risk of a later coronary intervention at this specific location.ResultsThe odds ratio (OR) varied by radiation dose to the mid left anterior descending artery (LAD) (p=0.005). Women receiving mean doses of 1-5 Gray (Gy) to the mid LAD had an adjusted OR of 0.90 (95% CI 0.47-1.74) for a later coronary intervention compared to women receiving mean doses of 0-1Gy to the mid LAD. In women receiving mean doses of 5-20Gy to the mid LAD, an adjusted OR of 1.24 (95% CI 0.52-2.95) was observed, which increased to an OR of 5.23 (95% CI 2.01-13.6) for mean doses over 20Gy, when compared to women receiving mean doses of 0-1Gy to the mid LAD.ConclusionsIn women receiving conventional 3DCRT for BC between 1992 and 2012, radiation doses to the LAD remained high and were associated with an increased requirement of coronary intervention in mid LAD. The results support that the LAD radiation dose should be considered in RT treatment planning and that the dose should be kept as low as possible. Minimising the dose to LAD is expected to diminish the risk of later radiation-induced stenosis.

  • 257.
    Wermer, Marieke J. H.
    et al.
    Departments of Neurology, Leiden University Medical Center, Albinusdreef 2, PO Box 9600, 2300 RC Leiden, The Netherlands.
    van Walderveen, Marianne A. A.
    Departments of Radiology, Leiden University Medical Center, Albinusdreef 2, PO Box 9600, 2300 RC Leiden, The Netherlands.
    Garpebring, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    van Osch, Matthias J. P.
    Departments of Radiology, Leiden University Medical Center, Albinusdreef 2, PO Box 9600, 2300 RC Leiden, The Netherlands; C.J. Gorter Center for High Field MRI of the Leiden University Medical Center, Albinusdreef 2, PO Box 9600, 2300 RC Leiden, The Netherlands.
    Versluis, Maarten J.
    Departments of Radiology, Leiden University Medical Center, Albinusdreef 2, PO Box 9600, 2300 RC Leiden, The Netherlands; C.J. Gorter Center for High Field MRI of the Leiden University Medical Center, Albinusdreef 2, PO Box 9600, 2300 RC Leiden, The Netherlands.
    7 Tesla MRA for the differentiation between intracranial aneurysms and infundibula2017In: Magnetic Resonance Imaging, ISSN 0730-725X, E-ISSN 1873-5894, Vol. 37, p. 16-20Article in journal (Refereed)
    Abstract [en]

    Objective: The differentiation between an aneurysm and an infundibulum with time-of-flight MRA is often difficult. However, this distinction is important because it affects further patient follow-up. The purpose of this study was to assess the added value of high resolution 7 Tesla MRA for investigating small vascular lesions suspect for an aneurysm or an infundibulum.

    Materials and methods: We included patients in whom an intracranial vascular lesion was detected in our University Hospital and in whom the discrimination between a true aneurysms or an infundibulum could not be made on conventional 1.5 or 3 T MRI were included in the study. All patients underwent an additional 7 T time-of-flight MRA at higher spatial resolution.

    Results: We included 6 patients. The age range of the patients was 35–65 years and 5 of them were women. 1 out of 6 had a 1.5 T MRI, the other 5 patients had a 3 T MRI previous to the 7 T MRI. The lesion size varied between 0.9 mm and 2.0 mm. In 5 of the 6 patients the presence of an infundibulum could be proven using the high resolution of the 7 T MRA. All patients tolerated the 7 T MRI well.

    Conclusion: Our results suggest that high resolution and contrast of 7 T MRA provides added diagnostic value in discriminating between intracranial aneurysms and infundibula. This finding may have important consequences for patient follow-up and comfort because it might reduce unnecessary follow-up exams and decrease uncertainty about the diagnosis. Larger studies, however, are needed to confirm our findings.

  • 258.
    Westlund, Arvid
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences. Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience.
    Holmlund, Petter
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Johansson, Elias
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience.
    Malm, Jan
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Semi-automatic method for segmentation of the internal jugular vein in ultrasound movies evaluated at different body postures2019In: Biomedical Physics & Engineering Express, E-ISSN 2057-1976, Vol. 5, no 4, article id 045034Article in journal (Refereed)
    Abstract [en]

    Objective: The collapse of the internal jugular vein (IJV) regulates intracranial pressure (ICP) in upright body positions. The cross-section area (CSA) is therefore of interest when studying the effects of postural changes in various neurological diseases. We have developed a semi-automatic segmentation method, which tracks the CSA of the IJV in ultrasound movies, and evaluated its performance in three body positions (supine, 16°, 71°). Approach: The proposed method utilized post-processing image filtering combined with a modified snake active contour algorithm. The ultrasound movies were retrospectively analysed (n = 231, 3s, 28 fps) based on previously collected data from 17 healthy volunteers. The computed CSAs (CA) from the segmentation method were compared to manually segmented CSAs (MA) in two frames per movie. Tracking performance were evaluated by visual inspection. Main results: In the supine position, 100% of the ultrasound movies were tracked successfully, and the mean of CA-MA was −4.4 ± 6.9 mm2 (MA, 88.4 ± 50.5 mm2). The most challenging movies occurred in upright body posture where tracking success rate was 90% and mean of CA-MA was −1.4 ± 2.2 mm2 (MA, 12.0 ± 11.1 mm2). The semi-automatic segmentations took 55 s to perform on average (per movie) compared to manual segmentations which took 50 min. Significance: Segmentations made by the proposed method were comparable to manual segmentations in all tilt-angles, however much faster. Efficient and accurate tracking of the CSA of the IJV, with respect to postural changes, could help furthering our understanding of how IJV-biomechanics relates to regulation of intracranial pressure in different neurological diseases and physiological states.

  • 259.
    Wezel, Joep
    et al.
    Leiden University Medical Center, Leiden, The Netherlands.
    Boer, Vincent O.
    University Medical Center Utrecht, Utrecht, The Netherlands.
    van der Velden, Tijl A.
    University Medical Center Utrecht, Utrecht, The Netherlands.
    Webb, Andrew G.
    Leiden University Medical Center, Leiden, The Netherlands.
    Klomp, Dennis W.J.
    University Medical Center Utrecht, Utrecht, The Netherlands.
    Versluis, Maarten J.
    Philips Healthcare Benelux, Eindhoven, The Netherlands.
    van Osch, Matthias J.P.
    Leiden University Medical Center, Leiden, The Netherlands.
    Garpebring, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics. Leiden University, Leiden University Medical Center, Leiden, The Netherlands.
    A comparison of navigators, snap-shot field monitoring, and probe-based field model training for correcting B0-induced artifacts in T2*-weighted images at 7 T2017In: Magnetic Resonance in Medicine, ISSN 0740-3194, E-ISSN 1522-2594, Vol. 78, p. 1373-1382Article in journal (Refereed)
    Abstract [en]

    Purpose

    To compare methods for estimating B0 maps used in retrospective correction of high-resolution anatomical images at ultra-high field strength. The B0 maps were obtained using three methods: (1) 1D navigators and coil sensitivities, (2) field probe (FP) data and a low-order spherical harmonics model, and (3) FP data and a training-based model.

    Methods

    Data from nine subjects were acquired while they performed activities inducing B0 field fluctuations. Estimated B0 fields were compared with reference data, and the reductions of artifacts were compared in corrected T2* images.

    Results

    Reduction of sum-of-squares difference relative to a reference image was evaluated, and Method 1 yielded the largest artifact reduction: 27 ± 15%, 20 ± 18% (mean ± 1 standard deviation) for deep breathing and combined deep breathing and hand motion activities. Method 3 performed almost as well (24 ± 18%, 15 ± 17%), provided that adequate training data were used, and Method 2 gave a similar result (21 ± 16%, 19 ± 17%).

    Conclusion

    This study confirms that all of the investigated methods can be used in retrospective image correction. In terms of image quality, Method 1 had a small advantage, whereas the FP-based methods measured the B0 field slightly more accurately. The specific strengths and weaknesses of FPs and navigators should therefore be considered when determining which B0-estimation method to use. 

  • 260.
    Wezel, Joep
    et al.
    Leiden University Medical Center, Leiden, The Netherlands.
    Garpebring, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics. Leiden University, Leiden University Medical Center, Leiden, The Netherlands.
    Webb, Andrew G.
    Leiden University Medical Center, Leiden, The Netherlands.
    van Osch, Matthias J.P.
    Leiden University Medical Center, Leiden, The Netherlands.
    Beenakker, Jan-Willem M.
    Leiden University Medical Center, Leiden, The Netherlands.
    Automated eye blink detection and correction method for clinical MR eye imaging2017In: Magnetic Resonance in Medicine, ISSN 0740-3194, E-ISSN 1522-2594, Vol. 78, no 1, p. 165-171Article in journal (Refereed)
    Abstract [en]

    Purpose: To implement an on-line monitoring system to detect eye blinks during ocular MRI using field probes, and to reacquire corrupted k-space lines by means of an automatic feedback system integrated with the MR scanner.

    Methods: Six healthy subjects were scanned on a 7 Tesla MRI whole-body system using a custom-built receive coil. Subjects were asked to blink multiple times during the MR-scan. The local magnetic field changes were detected with an external fluorine-based field probe which was positioned close to the eye. The eye blink produces a field shift greater than a threshold level, this was communicated in real-time to the MR system which immediately reacquired the motion-corrupted k-space lines.

    Results: The uncorrected images, using the original motion-corrupted data, showed severe artifacts, whereas the corrected images, using the reacquired data, provided an image quality similar to images acquired without blinks.

    Conclusion: Field probes can successfully detect eye blinks during MRI scans. By automatically reacquiring the eye blink-corrupted data, high quality MR-images of the eye can be acquired. 

  • 261.
    Widmark, Anders
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
    Gunnlaugsson, A.
    Beckman, L.
    Thellenberg-Karlsson, Camilla
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
    Hoyer, M.
    Lagerlund, M.
    Fransson, Per
    Umeå University, Faculty of Medicine, Department of Nursing.
    Kindblom, J.
    Ginman, C.
    Johansson, B.
    Seke, M.
    Björnlinger, K.
    Kjellén, E.
    Franzen, Lars
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
    Nilsson, P.
    Extreme Hypofractionation versus Conventionally Fractionated Radiotherapy for Intermediate Risk Prostate Cancer: Early Toxicity Results from the Scandinavian Randomized Phase III Trial "HYPO-RT-PC"2016In: International Journal of Radiation Oncology, Biology, Physics, ISSN 0360-3016, E-ISSN 1879-355X, Vol. 96, no 5, p. 938-939Article in journal (Refereed)
  • 262.
    Widmark, Anders
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
    Helle, S. I.
    James, N.
    Larsson, Anders
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Histology and Cell Biology.
    Staudacher, K.
    Haugen, I.
    Garcia-Vargas, J.
    Nilsson, S.
    Hematologic Safety Profile of Radium-223 Dichloride (Ra-223) From the Phase 3 ALSYMPCA Trial in Castration-Resistant Prostate Cancer (CRPC) Patients With Bone Metastases2013In: European Journal of Nuclear Medicine and Molecular Imaging, ISSN 1619-7070, E-ISSN 1619-7089, Vol. 40, no Supplement 2, p. S189-S190Article in journal (Other academic)
  • 263. Wiesinger, Florian
    et al.
    Bylund, Mikael
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Yang, Jaewon
    Kaushik, Sandeep
    Shanbhag, Dattesh
    Ahn, Sangtae
    Jonsson, Joakim
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Lundman, Josef
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Hope, Thomas
    Nyholm, Tufve
    Umeå University, Faculty of Medicine, Department of Radiation Sciences. Uppsala University, Uppsala, Sweden.
    Larson, Peder
    Cozzini, Cristina
    Zero TE-based pseudo-CT image conversion in the head and its application in PET/MR attenuation correction and MR-guided radiation therapy planning2018In: Magnetic Resonance in Medicine, ISSN 0740-3194, E-ISSN 1522-2594, Vol. 80, no 4, p. 1440-1451Article in journal (Refereed)
    Abstract [en]

    Purpose: To describe a method for converting Zero TE (ZTE) MR images into Xray attenuation information in the form of pseudo-CT images and demonstrate its performance for (1) attenuation correction (AC) in PET/MR and (2) dose planning in MR-guided radiation therapy planning (RTP).

    Methods: Proton density-weighted ZTE images were acquired as input for MRbased pseudo-CT conversion, providing (1) efficient capture of short-lived bone signals, (2) flat soft-tissue contrast, and (3) fast and robust 3D MR imaging. After bias correction and normalization, the images were segmented into bone, soft-tissue, and air by means of thresholding and morphological refinements. Fixed Hounsfield replacement values were assigned for air (-1000 HU) and soft-tissue (142 HU), whereas continuous linear mapping was used for bone.

    Results: The obtained ZTE-derived pseudo-CT images accurately resembled the true CT images (i. e., Dice coefficient for bone overlap of 0.73 +/- 0.08 and mean absolute error of 123 +/- 25 HU evaluated over the whole head, including errors from residual registration mismatches in the neck and mouth regions). The linear bone mapping accounted for bone density variations. Averaged across five patients, ZTE-based AC demonstrated a PET error of -0.04 +/- 1.68% relative to CT-based AC. Similarly, for RTP assessed in eight patients, the absolute dose difference over the target volume was found to be 0.23 +/- 0.42%.

    Conclusion: The described method enables MR to pseudo-CT image conversion for the head in an accurate, robust, and fast manner without relying on anatomical prior knowledge. Potential applications include PET/MR-AC, and MR-guided RTP.

  • 264.
    Wilén, Jonna
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Exposure assessment of electromagnetic fields near electrosurgical units.2010In: Bioelectromagnetics, ISSN 0197-8462, E-ISSN 1521-186X, Vol. 31, no 7, p. 513-518Article in journal (Refereed)
    Abstract [en]

    Electrosurgical units (ESU) are widely used in medical health services. By applying sinusoidal or pulsed voltage in the frequency range of 0.3-5 MHz to the electrode tip, the desired mixture of coagulation and cutting are achieved. Due to the high voltage and current in the cable, strong electromagnetic fields appear near the ESU. The surgeon and others inside the operating room such as nurses, anesthesiologists, etc., will be highly exposed to these fields. The stray fields surrounding the ESU have previously been measured, but now a deeper analysis has been made of the curve shape of the field and the implication of this when assessing exposure from a commonly used ESU in accordance with the International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines. The result showed that for some of the modes, especially those using high-pulsed voltage with only a few sinusoidal periods, the E-field close to the cable could reach linear spatially averaged values of 20 kV/m compared to the 2.1 kV/m stated in ICNIRP guidelines. Assessing the E- and B-field from ESU is not straightforward since in this frequency range, both induced current density and specific absorption rate are restricted by the ICNIRP guidelines. Nevertheless, work needs to be done to reduce the stray fields from ESU. Bioelectromagnetics (c) 2010 Wiley-Liss, Inc.

  • 265.
    Wilén, Jonna
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    de Vocht, Frank
    Health complaints among nurses working near MRI scanners-A descriptive pilot study2011In: European Journal of Radiology, ISSN 0720-048X, E-ISSN 1872-7727, Vol. 80, no 2, p. 510-513Article in journal (Refereed)
    Abstract [en]

    A questionnaire-based descriptive pilot study was conducted among all nurses routinely working with MRI in the Northern part of Sweden to provide an indication of the self-reported prevalence of health complaints related to working with MRI systems. Fifty-nine nurses (88% response rate), with on average 8 (±6) years experience with MRI scanning procedures, returned the questionnaire. In total, 9 nurses (15%) reported regularly experiencing at least one of the health complaints (1-5% for specific health complaints) attributed to arise or be aggravated by their presence in the MRI scanning room. Stratification of the results indicated that reporting of adverse symptoms was not related to the level of occupational workload/stress. However, reporting of health complaints was related to the strength of the magnet(s) the nurses worked with, with 57% of symptoms reported by those nurses working with the strongest systems (both 1.5 and 3T scanners in this population). Although this descriptive study did not include a control population and was based on self-reporting of health complaints, these data indicate that the prevalence of reported health complaints is not related to perceived work load or occupational stress, but does confirm data from other occupational sectors and indicates that the prevalence of adverse health complaints increases with the strength of the MRI system for nurses as well.

  • 266.
    Wärner, Harald
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Knowledge, Attitudes and Practices on dengue: A KAP-study aimed for health care personnel at hospitals in the district of Yogyakarta, Indonesia2015Independent thesis Basic level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 267.
    Wåhlin, Anders
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Ambarki, Khalid
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Hauksson, Jón
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    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.
    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).
    Phase contrast MRI quantification of pulsatile volumes of brain arteries, veins, and cerebrospinal fluids compartments: repeatability and physiological interactions2012In: Journal of Magnetic Resonance Imaging, ISSN 1053-1807, E-ISSN 1522-2586, Vol. 35, no 5, p. 1055-1062Article in journal (Refereed)
    Abstract [en]

    PURPOSE: To study measurement repeatability and physiological determinants on measurement stability for phase contrast MRI (PC-MRI) measurements of cyclic volume changes (ΔV) of brain arteries, veins, and cerebrospinal fluid (CSF) compartments.

    MATERIALS AND METHODS: Total cerebral blood flow (tCBF), total internal jugular flow (tJBF) and spinal CSF flow at C2-C3 level and CSF in the aqueduct was measured using five repetitions in 20 healthy subjects. After subtracting net flow, waveforms were integrated to calculate ΔV of arterial, venous, and cerebrospinal fluid compartments. The intraclass correlation coefficient (ICC) was used to measure repeatability. Systematic errors were investigated by a series of phantom measurements.

    RESULTS: For ΔV calculated from tCBF, tJBF and both CSF waveforms, the ICC was ≥0.85. ΔV from the tCBF waveform decreased linearly between repetitions (P = 0.012). Summed CSF and venous volume being shifted out from the cranium was correlated with ΔV calculated from the tCBF waveform (r = 0.75; P < 0.001). Systematic errors increased at resolutions <4 pixels per diameter.

    CONCLUSION: Repeatability of ΔV calculated from tCBF, tJBF, and CSF waveforms allows useful interpretations. The subject's time in the MR system and imaging resolution should be considered when interpreting volume changes. Summed CSF and venous volume changes was associated with arterial volume changes.

    J. Magn. Reson. Imaging 2011;. © 2011 Wiley Periodicals, Inc.

  • 268.
    Zackrisson, Björn
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
    Kjellén, Elisabeth
    Söderström, Karin
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
    Brun, Eva
    Nyman, Jan
    Friesland, Signe
    Reizenstein, Johan
    Sjodin, Helena
    Ekberg, Lars
    Lödén, Britta
    Franzén, Lars
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
    Ask, Anders
    Wickart-Johansson, Gun
    Lewin, Freddi
    Björk-Eriksson, Thomas
    Lundin, Erik
    Dalianis, Tina
    Wennerberg, Johan
    Johansson, Karl-Axel
    Nilsson, Per
    Mature results from a Swedish comparison study of conventional versus accelerated radiotherapy in head and neck squamous cell carcinoma - The ARTSCAN trial2015In: Radiotherapy and Oncology, ISSN 0167-8140, E-ISSN 1879-0887, Vol. 117, no 1, p. 99-105Article in journal (Refereed)
    Abstract [en]

    Background and purpose: This report contains the mature five-year data from the Swedish ARTSCAN trial including information on the influence of p16 positivity (p16+) for oropharyngeal cancers. Material and methods: Patients with previously untreated squamous cell carcinoma without distant metastases of the oral cavity, oropharynx, larynx (except T1-2, NO glottic cancers) and hypopharynx were included. Patients were randomised between accelerated fractionation (AF) (1.1 Gy + 2 Gy per day, 5 days/week for 4.5 weeks, total dose 68 Gy) and conventional fractionation (CF) (2 Gy per day, 5 days/week for 7 weeks, total dose 68 Gy). Human papillomavirus (HPV)-associated p16-expression was assessed retrospectively in tumour tissues from patients with oropharyngeal carcinoma. Results: There was no significant difference in loco-regional control (LRC) between AF and CF (log-rank test p = 0.75). LRC at 5 years was 65.5% for AF and 64.9% for CF. Overall survival (OS) was similar in both arms (p = 0.99). The estimated cancer specific survival (CSS) at 5 years was 62.2% (AF) and 63.3% (CF) (p = 0.99). 206 specimens were analysed for p16 with 153 specimens (74%) identified as p16+. P16 status did not discriminate for response to AF vs. CF with regard to LRC, OS or CSS. Patients with p16+ tumours had a statistically significant better overall prognosis compared with p16 tumours. Conclusion: This update confirms the results of the 2-year report. We failed to identify a positive effect resulting from AF with regards to LRC, OS and CSS. The addition of information on the HPV-associated p16 overexpression did not explain this lack of effect.

  • 269.
    Zarrinkoob, Laleh
    et al.
    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.
    Wåhlin, Anders
    Umeå University, Faculty of Medicine, Umeå Centre for Functional Brain Imaging (UFBI). Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Birgander, Richard
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Carlberg, Bo
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    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, Clinical Neuroscience.
    Aging alters the dampening of pulsatile blood flow in cerebral arteries2016In: Journal of Cerebral Blood Flow and Metabolism, ISSN 0271-678X, E-ISSN 1559-7016, Vol. 36, no 9, p. 1519-1527Article in journal (Refereed)
    Abstract [en]

    Excessive pulsatile flow caused by aortic stiffness is thought to be a contributing factor for several cerebrovascular diseases. The main purpose of this study was to describe the dampening of the pulsatile flow from the proximal to the distal cerebral arteries, the effect of aging and sex, and its correlation to aortic stiffness. Forty-five healthy elderly (mean age 71 years) and 49 healthy young (mean age 25 years) were included. Phase-contrast magnetic resonance imaging was used for measuring blood flow pulsatility index and dampening factor (proximal artery pulsatility index/distal artery pulsatility index) in 21 cerebral and extra-cerebral arteries. Aortic stiffness was measured as aortic pulse wave velocity. Cerebral arterial pulsatility index increased due to aging and this was more pronounced in distal segments of cerebral arteries. There was no difference in pulsatility index between women and men. Dampening of pulsatility index was observed in all cerebral arteries in both age groups but was significantly higher in young subjects than in elderly. Pulse wave velocity was not correlated with cerebral arterial pulsatility index. The increased pulsatile flow in elderly together with reduced dampening supports the pulse wave encephalopathy theory, since it implies that a higher pulsatile flow is reaching distal arterial segments in older subjects.

  • 270.
    Zborayova, Katarina
    et al.
    Umeå University, Faculty of Medicine, Department of Clinical Sciences.
    Antti, Henrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Blomqvist, L.
    Flygare, Lennart
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology.
    Gebre-Medhin, M.
    Jonsson, Joakim
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Söderkvist, Karin
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
    Zackrisson, Björn
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
    Early changes in multiparametric imaging parameters during radiotherapy of squamous carcinoma2019In: Radiotherapy and Oncology, ISSN 0167-8140, E-ISSN 1879-0887, Vol. 132, p. 63-63Article in journal (Other academic)
  • 271.
    Zhao, Ying
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine.
    Effect of valve replacement for aortic stenosis on ventricular function2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    BackgroundAortic stenosis (AS) is the commonest valve disease in the West. Aortic valve replacement (AVR) remains the only available management for AS and results in improved symptoms and recovery of ventricular functions. In addition, it is well known that AVR results in disruption of LV function mainly in the form of reversal of septal motion as well as depression of right ventricular (RV) systolic function. The aim of this thesis was to study, in detail, the early and mid-term response of ventricular function to AVR procedures (surgical and TAVI) as well as post operative patients’ exercise capacity.

    MethodsWe studied LV and RV function by Doppler echocardiography and speckle tracking echocardiography (STE) in the following 4 groups; (1) 30 severe AS patients (age 62±11 years, 19 male) with normal LV ejection fraction (EF) who underwent AVR, (2) 20 severe AS patients (age 79±6 years, 14 male) who underwent TAVI, (3) 30 healthy controls (age 63±11 years, 16 male), (4) 21 healthy controls (age 57±9 years, 14 male) who underwent exercise echocardiography.

    Results: After one week of TAVI, the septal radial motion and RV tricuspid annulus peak systolic excursion (TAPSE) were not different from before, while surgical AVR had significantly reversed septal radial motion and TAPSE dropped by 70% compared to before. The extent of the reversed septal motion correlated with that of TAPSE (r=0.78, p<0.001) in the patients as a whole after AVR and TAVI (Study I). Compared with controls, the LV twist function was increased in AS patients before and normalized after 6 months of surgical AVR. In controls, the LV twist correlated with LV fractional shortening (r=0.81, p<0.001), a relationship which became weak in patients before (r=0.52, p<0.01) and after AVR (r=0.34, p=ns) (Study II). After 6 months of surgical AVR, the reversed septal radial motion was still significantly lower than before. The septal peak displacement also decreased and its time became prolonged. In contrast, the LV lateral wall peak displacement increased and the time to peak displacement was early. The accentuated lateral wall peak displacement correlated with the septal peak displacement time delay (r=0.60, p<0.001) and septal-lateral time delay (r=0.64, p<0.001) (Study III). In 21 surgical AVR patients who performed exercise echocardiography, the LV function was normal at rest but different from controls with exercise. At peak exercise, oxygen consumption (pVO2) was lower in patients than controls. Although patients could achieve cardiac output (CO) and heart rate (HR) similar to controls at peak exercise, the LV systolic and early diastolic myocardial velocities and strain rate as well as their delta changes were significantly lower than controls. pVO2 correlated with peak exercise LV myocardial function in the patients group only, and the systolic global longitudinal strain rate (GLSRs) at peak exercise was the only independent predictor of pVO2 in multivariate regression analysis (p=0.03) (Study IV).

    Conclusion: Surgical AVR is an effective treatment for AS patients, but results in reversed septal radial motion and reduced TAPSE. The newly developed TAVI procedure maintains RV function which results in preservation of septal radial motion. In AS, the LV twist function is exaggerated, normalizes after AVR but loses its relationship with basal LV function. While the reversed septal motion results in decreased and delayed septal longitudinal displacement which is compensated for by the accentuated lateral wall displacement and the time early. These patients remain suffering from limited exercise capacity years after AVR.

  • 272.
    Ångström-Brännström, Charlotte
    et al.
    Umeå University, Faculty of Medicine, Department of Nursing.
    Engvall, Gunn
    Mullaney, Tara
    Umeå University, Faculty of Science and Technology, Umeå Institute of Design.
    Nilsson, Kristina
    Wickart-Johansson, Gun
    Svärd, Anna-Maja
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Nyholm, Tufve
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Lindh, Jack
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Lindh, Viveca
    Umeå University, Faculty of Medicine, Department of Nursing.
    Children Undergoing Radiotherapy: Swedish Parents' Experiences and Suggestions for Improvement2015In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 10, no 10, article id e0141086Article in journal (Refereed)
    Abstract [en]

    Approximately 300 children, from 0 to 18 years old, are diagnosed with cancer in Sweden every year. Of these children, 80-90 of them undergo radiotherapy treatment for their cancer. Although radiotherapy is an encounter with advanced technology, few studies have investigated the child's and the parent's view of the procedure. As part of an ongoing multi-center study aimed to improve patient preparation and the care environment in pediatric radiotherapy, this article reports the findings from interviews with parents at baseline. The aim of the present study was twofold: to describe parents' experience when their child undergoes radiotherapy treatment, and to report parents' suggestions for improvements during radiotherapy for their children. Sixteen mothers and sixteen fathers of children between 2-16 years old with various cancer diagnoses were interviewed. Data were analyzed using content analysis. The findings showed that cancer and treatment turns people's lives upside down, affecting the entire family. Further, the parents experience the child's suffering and must cope with intense feelings. Radiotherapy treatment includes preparation by skilled and empathetic staff. The parents gradually find that they can deal with the process; and lastly, parents have suggestions for improvements during the radiotherapy treatment. An overarching theme emerged: that despair gradually turns to a sense of security, with a sustained focus on and close interaction with the child. In conclusion, an extreme burden was experienced around the start of radiotherapy, though parents gradually coped with the process.

  • 273.
    Öhberg, Fredrik
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    The effect of anisotropic systematic errors in estimating helical angles2008In: Computer Methods in Biomechanics and Biomedical Engineering, ISSN 1025-5842, E-ISSN 1476-8259, Vol. 11, no 2, p. 205-213Article in journal (Refereed)
    Abstract [en]

    A common question in movement studies is how the results should be interpreted with respect to systematic and random errors. In this study, simulations are made in order to see how a rigid body's orientation in space (i.e. helical angle between two orientations) is affected by (1) a systematic error added to a single marker (2) a combination of this systematic error and Gaussian white noise. The orientation was estimated after adding a systematic error to one marker within the rigid body. This procedure was repeated with Gaussian noise added to each marker.

    In conclusion, results show that the systematic error's effect on estimated orientation depends on number of markers in the rigid body and also on which direction the systematic error is added. The systematic error has no effect if the error is added along the radial axis (i.e. the line connecting centre of mass and the affected marker).

  • 274.
    Öhberg, Lars
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology. Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Sports Medicine.
    The chronic painful Achilles tendon: sonographic findings and new methods for treatment2003Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The aim of the present thesis was to evaluate sonographic methods for investigation of the chronic painful Achilles tendon.

    In a prospective study on patients with chronic painful mid-portion Achilles tendinosis, grey-scale ultrasound (US) showed a decreased tendon thickness and a “normalized” structure in the majority of patients successfully treated with eccentric calf-muscle training. By combining US with colour Doppler examination (CDV), a neovascularisation was shown in the region with structural tendon changes in all painful tendons, but not in any of the pain-free normal tendons. In a small pilot study, the sclerosing agent Polidocanol was injected towards the neovessels under US and CDV guidance. The majority of the patients became painfree and had no remaining neovessels, while the patients with remaining pain had remaining neovessels. The combined findings from US, immuno-histochemical analyses of biopsies, and diagnostic injections, showed that the patients were temporarily pain-free after US and CDV guided injections of local anaesthesia towards the region with neovessels, and biopsies from the region with tendon changes and neovascularisation showed nerve structures in close relation to blood vessels. The presence of neovessels was shown also in patients with chronic pain in the Achilles tendon insertion, and it was found that treatment with sclerosing injections cured the pain in the majority of patients. A good result of treatment was associated with no remaining neovessels.

    In a prospective study on patients with chronic mid-portion Achilles tendinosis treated with eccentric training, CDV after treatment showed no remaining neovessels in the majority of the pain-free patients. In the patients with remaining tendon pain there were remaining neovessels. In conclusion, the findings in this thesis indicate that neovessels and accompanying nerves might be the source of chronic Achilles tendon pain. Sclerosing injections towards the neovessels, and eccentric training, seem to have a potential to cure the pain.

  • 275.
    Öhman, Anders
    et al.
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Forsgren, Lars
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    NMR metabonomics of cerebrospinal fluid distinguishes between Parkinson's disease and controls2015In: Neuroscience Letters, ISSN 0304-3940, E-ISSN 1872-7972, Vol. 594, p. 36-39Article in journal (Refereed)
    Abstract [en]

    This study assesses if nuclear magnetic resonance (NMR) metabonomics can discriminate between Parkinson's disease (PD) patients and control subjects, and consequently identify metabolic markers for the disease. One-dimensional H-1 NMR spectroscopy was used for quantitative analysis of metabolites in the cerebrospinal fluid (CSF) from 10 PD patients and 10 control individuals, together with uni- and multivariate statistical analysis to discriminate between the groups and to identify significantly altered metabolite concentrations. In total 60 metabolites were identified and of those 38 were quantified in all CSF samples. An overall lowering of metabolite content was observed in PD patients compared to control subjects (fold change of 0.85 +/- 0.30). Multivariate statistics reveal significant changes (vertical bar w*vertical bar>0.2) among nine metabolites (alanine, creatinine, dimethylamine, glucose, lactate, mannose, phenylalanine, 3-hydroxyisobutyric acid and 3-hydroxyisovaleric acid). Three of these (alanine, creatinine and mannose) are identified as significantly changed also by univariate statistics (p < 0.00132, Bonferroni corrected). Panels with all or a selected set of these metabolites were successfully used for discriminating between the two groups. In conclusion, NMR metabonomics can readily determine metabolite concentrations in CSF, identify putative biomarkers that distinguish between the PD patients and control subjects, and thus potentially become a tool for diagnostic purposes.

  • 276.
    Österholm, Karoline
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics. Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Effects of pollen and air pollution on small airway resistance - A panel study on asthmatics and controls in Umeå, Sweden2017Independent thesis Basic level (professional degree), 20 credits / 30 HE creditsStudent thesis
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