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  • 151.
    Lilliesköld, Elina
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics. Umeå University, Faculty of Science and Technology, Department of Physics.
    Magnetfält i kuvöser för för tidigt födda barn2011Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    It has previously been observed that the magnetic fields in infant incubators can be relatively high, particularly due to the heating bed the child is lying on. In epidemiologic studies of childhood leukaemia in association with exposure to magnetic fields, an inclination to excess risk has been found amongst premature children that have been lying in infant incubators with high magnetic field levels. Influence on the heart rate variability has also been found in children that have been treated in incubators, where elevated magnetic field levels are seen as a possible explanation. The purpose of this study was to map the magnetic field exposure in two different infant incubators (Dräger 8000 IC and Giraffe OmniBed) and the peripheral equipment. Furthermore, the magnetic field was logged over time in both incubator models. In the older model, Dräger 8000 IC, magnetic field levels between 1.0 µT and 8.1 µT were measured during the mapping of the magnetic field distribution over the bed. The highest value was localized above the heater, a short distance from the centre of the bed. The magnetic field in the newer model, Giraffe OmniBed, varied between 0.2 µT and 5.8 µT during the mapping, where the highest value was localized towards one of the short ends of the incubator. The mean value from the long term registration was calculated to 1.9 µT for the Dräger incubator and 0.2 µT for the Giraffe incubator. The average magnetic field level from the long-term registrations was used to calculate a dose for the baby, expressed in microtesla hours. The average dose for seven weeks of full time treatment in an incubator was 2.9∙103 µT∙h for the head and 2.4∙103 µT∙h for the remaining body in the Dräger incubator. Corresponding values for the Giraffe incubator was 4.4∙102 µT∙h for the head and 2.7∙102 µT∙h for the body. Long-time registration in home environment was also conducted in an older house and in a newer apartment. The average dose for seven full weeks was then 10 – 60 µT∙h. The conclusion from all this is that the magnetic field levels in the newer incubator model (Giraffe OmniBed) was significantly lower than in the older model (Dräger 8000 IC) but still higher than in an average home environment.

  • 152. Lindberg, Frida
    et al.
    Mårtensson, Mattias
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Brodin, Lars-Åke
    Evaluation of ultrasound Tissue Velocity Imaging: a phantom study of velocity estimation in skeletal muscle low-level contractions2013In: BMC Medical Imaging, ISSN 1471-2342, E-ISSN 1471-2342, Vol. 13, no 16Article in journal (Refereed)
    Abstract [en]

    Background: Tissue Velocity Imaging (TVI) is an ultrasound based technique used for quantitative analysis of the cardiac function and has earlier been evaluated according to myocardial velocities. Recent years several studies have reported applying TVI in the analysis of skeletal muscles. Skeletal tissue velocities can be very low. In particular, when performing isometric contractions or contractions of low force level the velocities may be much lower compared to the myocardial tissue velocities. Methods: In this study TVI was evaluated for estimation of tissue velocities below the typical myocardial velocities. An in-house phantom was used to see how different PRF-settings affected the accuracy of the velocity estimations. Results: With phantom peak velocity at 0.03 cm/s the error ranged from 31% up to 313% with the different PRF-settings in this study. For the peak velocities at 0.17 cm/s and 0.26 cm/s there was no difference in error with tested PFR settings, it is kept approximately around 20%. Conclusions: The results from the present study showed that the PRF setting did not seem to affect the accuracy of the velocity estimation at tissue velocities above 0.17 cm/s. However at lower velocities (0.03 cm/s) the setting was crucial for the accuracy. The PRF should therefore preferable be reduced when the method is applied in low-level muscle contraction.

  • 153.
    Lindqvist, Per
    et al.
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Henein, Michael Y.
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Right ventricular function in pulmonary hypertension2012In: Imaging in Medicine, ISSN 1755-5191, Vol. 4, no 6, p. 657-665Article, review/survey (Refereed)
    Abstract [en]

    The right ventricle has recently attracted a lot of attention, having been shown to have a central function in overall cardiac performance in heart failure, cardiac surgery and congenital heart disease. Furthermore, in most of these cases the right ventricle has shown a strong prognostic value, irrespective of other cardiac disturbances. This has stimulated clinicians and researchers to identify noninvasive markers of right ventricular dysfunction using various technologies, for example, echocardiography and cardiac MRI. This review summarizes the role of right ventricular function in pulmonary hypertension and the most reliable markers of dysfunction, which should be routinely used in managing such cases.

  • 154.
    Lindström, Anton
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Andersson, C. David
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Johansson, Adam
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Karlsson, Mikael
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Nyholm, Tufve
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics. Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
    Bone contrast optimization in magnetic resonance imaging using experimental design of ultra-short echo-time parameters2013In: Chemometrics and Intelligent Laboratory Systems, ISSN 0169-7439, E-ISSN 1873-3239, Vol. 125, p. 33-39Article in journal (Refereed)
    Abstract [en]

    For the purpose of improved planning and treatment by radiation of tumours, we present work exploring the effect of controllable ultra-short echo-time (UTE) sequence settings on the bone contrast in magnetic resonance (MR) imaging, using design of experiments (DoE). Images were collected using UTE sequences from MR imaging and from standard computed tomography (CT). CT was used for determining the spatial position of the bony structures in an animal sample and co-registered with the MR images. The effect of the UTE sequence parameter flip angle (Flip), repetition time (T-R), echo time (T-E), image matrix size (Vox) and number of radial sampling spokes (Samp) were studied. The parameters were also investigated in a healthy voluntary and it was determined that the optimal UTE settings for high bone contrast in a clinically relevant set up were: Flip similar to 9 degrees and T-E = 0.07 ms, while T-R was kept at 8 ms, Vox at 192 and Samp at 30,000. The use of response surface maps, describing the modelled relation between bone contrast and UTE settings, founded in the DoE, may provide information and be a tool to more appropriately select suitable UTE sequence settings.

  • 155.
    Lisi, Matteo
    et al.
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology. Department of Cardiovascular Disease, University of Siena, Siena, Italy.
    Cameli, Matteo
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Righini, Francesca Maria
    Malandrino, Angela
    Tacchini, Damiana
    Focardi, Marta
    Tsioulpas, Charilaos
    Bemazzali, Sonia
    Tanganelli, Piero
    Maccherini, Massimo
    Mondillo, Sergio
    Henein, Michael Y
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    RV Longitudinal Deformation Correlates With Myocardial Fibrosis in Patients With End-Stage Heart Failure2015In: JACC Cardiovascular Imaging, ISSN 1936-878X, E-ISSN 1876-7591, Vol. 8, no 5, p. 514-522Article in journal (Refereed)
    Abstract [en]

    Objectives: This study was performed to determine the accuracy of right ventricular (RV) longitudinal strain (LS) in predicting myocardial fibrosis in patients with severe heart failure (HF) undergoing heart transplantation. Background: RVLS plays a key role in the evaluation of its systolic performance and clinical outcome in patients with refractory HF. Methods: We studied 27 patients with severe systolic HF (ejection fraction ≤25% and New York Heart Association functional class III to IV, despite full medical therapy and cardiac resynchronization therapy) using echocardiography before heart transplantation. RV free wall LS, right atrial LS, sphericity index (SI), and tricuspid annular plane systolic excursion (TAPSE) were all measured. Upon removal of the heart, from the myocardial histologic analysis, the ratio of the fibrotic to the total sample area determined the extent of fibrosis (%). Results: RV myocardial fibrosis correlated with RV free wall LS (r = 0.80; p < 0.0001), SI (r = 0.42; p = 0.01) and VO2 max (r = –0.41; p = 0.03), with a poor correlation with TAPSE (r = –0.34; p = 0.05) and right atrial LS (r = –0.37; p = 0.03). Stepwise multivariate analysis showed that RV free wall LS (β = 0.701, p < 0.0001) was independently associated with RV fibrosis (overall model R2 = 0.64, p < 0.0001). RV free wall LS was the main determinant of myocardial fibrosis. In the subgroup of patients with severe RV fibrosis, RV free wall LS had the highest diagnostic accuracy for detecting severe myocardial fibrosis (area under the curve = 0.87; 95% confidence interval: 0.80 to 0.94). Conclusions: In late-stage HF patients, the right ventricle is enlarged, with reduced systolic function due to significant myocardial fibrosis. RV free wall myocardial deformation is the most accurate functional measure that correlates with the extent of RV myocardial fibrosis and functional capacity.

  • 156.
    Lizana, Helena
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Johansson, L.
    Umeå University.
    Larsson, A.
    Umeå University.
    Axelsson, Jan
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Linder, J.
    Umeå University.
    Ögren, M.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Varrone, A.
    Halldin, C.
    Jakobson Mo, Susanna
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Dosimetry and whole body distribution of [F-18]PE2I in healthy volunteers2016In: European Journal of Nuclear Medicine and Molecular Imaging, ISSN 1619-7070, E-ISSN 1619-7089, Vol. 43, p. S533-S533Article in journal (Refereed)
  • 157.
    Lizana, Helena
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Johansson, Lennart
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Axelsson, Jan
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Larsson, Anne
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Ögren, Mattias
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology.
    Linder, Jan
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Halldin, Christer
    Varrone, Andrea
    Jakobson Mo, Susanna
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology.
    Whole-Body Biodistribution and Dosimetry of the Dopamine Transporter Radioligand 18F-FE-PE2I in Human Subjects2018In: Journal of Nuclear Medicine, ISSN 0161-5505, E-ISSN 1535-5667, Vol. 59, no 8, p. 1275-1280Article in journal (Refereed)
    Abstract [en]

    F-18-(E)-N-(3-iodoprop-2-enyl)-2 beta-carbofluoroethoxy-3 beta-(4'-methylphenyl) nortropane (F-18-FE-PE2I) was recently developed and has shown adequate affinity and high selectivity for the dopamine transporter (DAT). Previous studies have shown promising results for F-18-FE-PE2I as a suitable radioligand for DAT imaging. In this study, we investigated the whole-body biodistribution and dosimetry of F-18-FE-PE2I in healthy volunteers to support its utility as a suitable PET imaging agent for the DAT. Methods: Five healthy volunteers were given a mean activity of 2.5 MBq/kg, and 3 PET scans, head to thigh, were performed immediately after injection followed by 4 whole-body PET/CT scans between 0.5 and 6 h after injection. Blood samples were drawn in connection with the whole-body scans, and all urine was collected until 6 h after injection. Volumes of interest were delineated around 17 organs on all images, and the areas under the time-activity curves were calculated to obtain the total number of decays in the organs. The absorbed doses to organs and the effective dose were calculated using the software IDAC. Results: The highest activity concentration was observed in the liver (0.9%-1.2% injected activity/100 g) up to 30 min after injection. At later time points, the highest concentration was seen in the gallbladder (1.1%-0.1% injected activity/100 g). The activity excreted with urine ranged between 23% and 34%, with a mean of 28%. The urinary bladder received the highest absorbed dose (119 mu Gy/MBq), followed by the liver (46 mu Gy/MBq). The effective dose was 23 mu Sv/MBq (range, 19-28 mu Sv/MBq), resulting in an effective dose of 4.6 mSv for an administered activity of 200 MBq. Conclusion: The effective dose is within the same order of magnitude as other commonly used PET imaging agents as well as DAT agents. The reasonable effective dose, together with the previously reported favorable characteristics for DAT imaging and quantification, indicates that F-18-FE-PE2I is a suitable radioligand for DAT imaging.

  • 158.
    Ljungkvist, Anna
    Umeå University, Faculty of Medicine, Radiation Sciences.
    Imaging the tumor microenvironment: the dynamics and modification of hypoxia2003Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The tumor vasculature is poor and heterogeneous which may result in inadequate oxygenation and changed energy status. In addition the balance between cell proliferation and the rate of cell death is disturbed, which results in tumor growth.

    The aims of this study were 1) to gain more insight into the relation between tumor vascularity, hypoxia, and proliferation in solid tumors, and 2) to study the changes and dynamics of tumor oxygenation in relation to the vascular architecture within individual tumors. For this purpose a double hypoxic marker method was developed, which was subsequently used to 3) determine the turnover rate of hypoxic cells in three different tumor models and 4) to study the effect of cytotoxic drugs on tumor hypoxia and cell death.

    Solid tumor models grown in mice were used. The tumor microenvironment was investigated with exogenous cell markers for hypoxia (pimonidazole and CCI-103F), cell proliferation (BrdUrd) and blood perfusion (Hoechst 33342). The vasculature and the exogenous cell markers were visualized with immunohistochemical techniques. The tumor sections were scanned and quantified with an image analysis systemconsisting of a fluorescence microscope, CCD camera and image analysis software.

    The spatial organization of hypoxia, proliferation, and tumor vasculature was analyzed in several xenograft lines. The study revealed two main hypoxic patterns that seemed to be the consequence of complex relations between vasculature, oxygen delivery, proliferation, and cell loss. The novel double hypoxic cell marker method, with sequential injection of two hypoxic markers, was developed to study dynamic changes of the tumor oxygenation. Based on varying injection intervals between the markers the hypoxic cell half-life was determined in three tumor lines, and ranged from 17 to 49 hours. Intra-tumoral changes in oxygenation status upon oxygen modifying treatments were measured with the double hypoxic marker method. Both decreased levels of tumor hypoxia after carbogen breathing (95%O2 and 5% CO2) and increased levels of tumor hypoxia, as a result of reduced tumor perfusion after hydralazine treatment was detected. Finally the double hypoxic marker assay was used to analyze the effects of the hypoxic cytotoxin tirapazamine in relation to the hypoxic cell population, which caused a reversible decrease of the hypoxic fraction.

    The results presented in this thesis now form the basis for further studies to identify subpopulations of cells that represent specific targets for therapy, and to investigate the effects of different treatment modalities.

  • 159. Loizou, Louiza
    et al.
    Duran, Carlos Valls
    Axelsson, Elisabet
    Andersson, Mats
    Keussen, Inger
    Strinnholm, Jörgen
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology.
    Bartholomä, Wolf
    Del Chiaro, Marco
    Segersvärd, Ralf
    Lundell, Lars
    Kartalis, Nikolaos
    Radiological assessment of local resectability status in patients with pancreatic cancer: Interreader agreement and reader performance in two different classification systems2018In: European Journal of Radiology, ISSN 0720-048X, E-ISSN 1872-7727, Vol. 106, p. 69-76Article in journal (Refereed)
    Abstract [en]

    Objectives: To assess the interreader agreement and reader performance in the evaluation of patients with pancreatic cancer (PC) in two classification systems of local resectability status prior to initiation of therapy, namely the National Comprehensive Cancer Network (NCCN) and Karolinska classification system (KCS).

    Methods: In this ethics review board-approved retrospective study, six radiologists independently evaluated pancreatic CT-examinations of 30 patients randomly selected from a tertiary referral centre's multidisciplinary tumour board database. Based on well-defined criteria of tumour-vessel relationship, each patient was assigned to one of three NCCN and six KCS categories. We assessed the intraclass correlation coefficient (ICC) and compared the percentages of correct tumour classification of the six readers in both systems (Chi-square test; a P-value < 0.05 was considered significant). The standard of reference was a consensus evaluation of CT-examinations by three readers not involved in the image analysis.

    Results: The ICC for NCCN and KCS was 0.82 and 0.84, respectively (very strong agreement). The percentages of correct tumour classification at NCCN and KCS were 53-83% and 30-57%, respectively, with no statistically significant differences in the overall reader comparison per classification system. In pair-wise comparison between readers for NCCN/KCS, there were statistically significant differences between reader 5 vs. readers 4 (P = 0.012) and 3 (P = 0.045)/ reader 5 vs. reader 4 (P = 0.037).

    Conclusion: Interreader agreement in both PC classification systems is very strong. NCCN may be advantageous in terms of reader performance compared to KCS.

  • 160.
    Lundgren, Josefin
    et al.
    Umeå University, Faculty of Medicine, Department of Nursing.
    Hedlund, Matilda
    Umeå University, Faculty of Medicine, Department of Nursing.
    Alternativ till sedering och narkos av barn vid magnetisk resonanstomografi: En litteraturstudie2016Independent thesis Basic level (professional degree), 180 HE creditsStudent thesis
    Abstract [sv]

    Bakgrund: MR-undersökningar är mer eller mindre krävande för patienter i alla åldrar. Utöver de speciella rutinerna inför en MR-undersökning så krävs det att patienten ligger helt stilla under hela undersökningen för att undvika rörelseartefakter. För att barn ska klara av detta används oftast sedering eller narkos som hjälpmedel, men vid intag av farmaka medföljer alltid en risk för oönskade effekter och allergiska reaktioner.

    Syfte: Syftet med denna litteraturstudie var att beskriva strategier som kan användas för att minska behovet av sedering eller narkos av barn som genomgår en MR-undersökning.

    Metod: En systematisk litteraturstudie utfördes för att besvara syftet. Resultatet från elva kvantitativa artiklar har granskats, analyserats och sammanställts.

    Resultat: Resultatet är presenterat i tre huvudkategorier med fem underkategorier vilkas metoder på olika sätt gör det lättare för patienten att genomgå en MR-undersökning. Huvudkategorierna är att bli förberedd, att underlätta tiden i MR-kameran och en kombination av att bli förberedd och underlätta tiden i MR-kameran.

    Konklusion: Genom att använda metoder anpassade för barn kan behovet av sederingar och narkoser minskas. Icke-farmakologiska metoder som förbereder barnen, underlättar tiden för dem i MR-kameran samt en kombination av dessa har resulterat i att fler barn kan genomgå en MR-undersökning utan behov av sedering eller narkos.

  • 161.
    Lundman, Josef A.
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Johansson, Adam
    Umeå University, Faculty of Medicine, Department of Radiation Sciences. Department of Radiation Oncology, University of Michigan, Ann Arbor, MI, United States.
    Olofsson, Jörgen
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Axelsson, Jan
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Larsson, Anne
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Nyholm, Tufve
    Umeå University, Faculty of Medicine, Department of Radiation Sciences. Medical Radiation Physics, Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden.
    Effect of gradient field nonlinearity distortions in MRI-based attenuation maps for PET reconstruction2017In: Physica medica (Testo stampato), ISSN 1120-1797, E-ISSN 1724-191X, Vol. 35, p. 1-6Article in journal (Refereed)
    Abstract [en]

    Purpose: Attenuation correction is a requirement for quantification of the activity distribution in PET. The need to base attenuation correction on MRI instead of CT has arisen with the introduction of integrated PET/MRI systems. The aim was to describe the effect of residual gradient field nonlinearity distortions on PET attenuation correction.

    Methods: MRI distortions caused by gradient field nonlinearity were simulated in CT images used for attenuation correction in PET reconstructions. The simulations yielded radial distortion of up to  at 15 cm from the scanner isocentre for distortion corrected images. The mean radial distortion of uncorrected images were 6.3 mm at the same distance. Reconstructions of PET data were performed using the distortion corrected images as well as the images where no correction had been applied.

    Results: The mean relative difference in reconstructed PET uptake intensity due to incomplete distortion correction was less than ±5%. The magnitude of this difference varied between patients and the size of the distortions remaining after distortion correction.

    Conclusions: Radial distortions of 2 mm at 15 cm radius from the scanner isocentre lead to PET attenuation correction errors smaller than 5%. Keeping the gradient field nonlinearity distortions below this limit can be a reasonable goal for MRI systems used for attenuation correction in PET for quantification purposes. A higher geometrical accuracy may, however, be warranted for quantification of peripheral lesions. These distortions can, e.g., be controlled at acceptance testing and subsequent quality assurance intervals.

  • 162.
    Lundman, Josef Axel
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Bylund, Mikael
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Garpebring, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Thellenberg Karlsson, Camilla
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Nyholm, Tufve
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Patient-induced susceptibility effects simulation in magnetic resonance imaging2017In: Physics and Imaging in Radiation Oncology, ISSN 2405-6316, Vol. 1, p. 41-45Article in journal (Refereed)
    Abstract [en]

    Background and purpose A fundamental requirement for safe use of magnetic resonance imaging (MRI) in radiotherapy is geometrical accuracy. One factor that can introduce geometrical distortion is patient-induced susceptibility effects. This work aims at developing a method for simulating these distortions. The specific goal being to help objectively identifying a balanced acquisition bandwidth, keeping these distortions within acceptable limits for radiotherapy.

    Materials and methods A simulation algorithm was implemented in Medical Interactive Creative Environment (MICE). The algorithm was validated by comparison between simulations and analytical solutions for a cylinder and a sphere. Simulations were performed for four body regions; neck, lungs, thorax with the lungs excluded, and the pelvic region. This was done using digital phantoms created from patient CT images, after converting the CT Hounsfield units to magnetic susceptibility values through interpolation between known values.

    Results The simulations showed good agreement with analytical solutions, with only small discrepancies due to pixelation of the phantoms. The calculated distortions in digital phantoms based on patient CT data showed maximal 95th percentile distortions of 39%, 32%, 28%, and 25% of the fat-water shift for the neck, lungs, thorax with the lungs excluded, and pelvic region, respectively.

    Conclusions The presented results show the expected pixel distortions for various body parts, and how they scale with bandwidth and field strength. This information can be used to determine which bandwidth is required to keep the patient-induced susceptibility distortions within an acceptable range for a given field strength.

  • 163.
    Lundmark, Martin
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Clinical evaluation of atlas-based segmentation for radiotherapy of head and neck tumours2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Background

    Semi-automated segmentation using deformable registration of atlases consisting of pre-segmented patient images can facilitate the tedious task of delineating structures and organs in patients subjected to radiotherapy planning. However, a generic atlas based on a single patient may not function well enough due to the anatomical variation between patients. Fusion of segmentation proposals from multiple atlases has the potential to provide a better segmentation due to a more complete representation of the anatomical variation.

    Purpose

    The main goal of the study was to investigate potential operator timesaving from editing of atlas-based segmentation compared to manual segmentation for head & neck cancer.

    Materials and Methods

    A commercial atlas-based segmentation software (VelocityAI from Nucletron AB) was used together with several expert generated and protocol-based atlases of delineated CT images to create multiple atlas segmentations through deformable registration. The atlas that was considered most universal was selected to construct single atlas segmentation proposals. For fusion of the multiple atlas segmentations an in-house developed algorithm, including information of local registration success was used in a MATLAB-environment1. The algorithm uses weighted distance map calculations where weights represent probabilities of improving the segmentation results. Based on previous results1 the probabilities were estimated using the cross correlation image similarity measure evaluated over a region within a certain distance from the segmentation. Ten patients were incorporated in the study. Each patient was delineated three times, (a) manually by the radiation oncologist, (b) with a single atlas segmentation and (c) with a fusion of multiple atlas segmentations. For the methods (b) and (c) the radiation oncologist corrected the proposed segmentations blindly without using the result from method (a) as reference. For case (c) a total number of 11 atlas segmentations were used. The time spent for segmenting or editing the segmentation proposals by the radiation oncologist was recorded separately for each method and each individual ROI. In addition a grading was used to score how helpful the candidate segmentation proposals were for the structure delineations. The Dice Similarity Coefficient, the Hausdorff distance and the volume were used to evaluate the similarity between the delineated structures.

    Results

    The results show a time reduction in the order of 40% when the radiation oncologist only has to correct the multiple atlas-based segmentation proposal compared to manual segmentation. When using single atlas the corresponding figure is 21%.

    Conclusions

    Using atlas-based segmentation can reduce the time needed for delineation in the head and neck area of patients admitted for radiotherapy.

    1C. Sjöberg and A. Ahnesjö, Evaluation of atlas-based segmentation using probabilistic weighted distance maps, Manuscript, Uppsala University, 2011

  • 164. Lynoe, N.
    et al.
    Olsson, D.
    Eriksson, Anders
    Umeå University, Faculty of Medicine, Department of Community Medicine and Rehabilitation, Forensic Medicine.
    Is Delayed Speech Development a Long-Term Sequela of Birth-Related Subdural Hematoma?2019In: American Journal of Neuroradiology, ISSN 0195-6108, E-ISSN 1936-959X, Vol. 40, no 2, p. E10-E10Article in journal (Refereed)
  • 165. Lynøe, Niels
    et al.
    Rosén, Måns
    Elinder, Göran
    Hallberg, Boubou
    Sundgren, Pia
    Eriksson, Anders
    Umeå University, Faculty of Medicine, Department of Community Medicine and Rehabilitation, Forensic Medicine.
    Pouring out the dirty bathwater without throwing away either the baby or its parents: commentary to Saunders et al.2018In: Pediatric Radiology, ISSN 0301-0449, E-ISSN 1432-1998, Vol. 48, no 2, p. 284-286Article in journal (Refereed)
  • 166.
    Mahmood, Sarwar S
    et al.
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences.
    Al-Amiry, Bariq
    Department of Radiology, Karolinska University Hospital-Huddinge, Stockholm, Sweden.
    Mukka, Sebastian S
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences. Sundsvall and Norrland University Hospitals.
    Baea, Saida
    Department of Radiology, Sundsvall Teaching Hospital, Sundsvall, Sweden.
    Sayed-Noor, Arkan S
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences. Department of Orthopaedics, Sundsvall Teaching Hospital, Sundsvall, Sweden .
    Validity, reliability and reproducibility of plain radiographic measurements after total hip arthroplasty2015In: Skeletal Radiology, ISSN 0364-2348, E-ISSN 1432-2161, Vol. 44, no 3, p. 345-351Article in journal (Refereed)
    Abstract [en]

    In total hip arthroplasty (THA), radiographic preoperative planning and postoperative evaluation of acetabular component, femoral offset (FO) and leg length discrepancy (LLD) require good validity, interobserver reliability and intraobserver reproducibility. In this study, we evaluated the validity of the Sundsvall method of FO measurement and the interobserver reliability and intraobserver reproducibility of measurement of FO, LLD, acetabular cup inclination and anteversion. Ninety patients with primary unilateral osteoarthritis (OA) were included in this prospective study. On postoperative radiographs FO by the Sundsvall method (femoral axis-pelvic midline), FO by a standard method (femoral axis-hip rotational centre-teardrop point), LLD (inter-teardrop line-lesser trochanter), acetabular cup inclination (on AP view the angle between the cup rim and transischial line) and anteversion (on lateral view the angle between the face of acetabulum and a line perpendicular to the horizontal plane) were measured. The interobserver reliability and intraobserver reproducibility were calculated for three independent observers. The concurrent validity and degree of prediction of the Sundsvall method are measured by comparing its results with the standard method. The interobserver reliability of all measurements was excellent (ICC > 0.80), except for LLD, which was substantial (ICC = 0.79). The intraobserver reproducibility of all measurements was excellent (ICC > 0.80). The concurrent validity of the Sundsvall method compared to the standard method was good with a positive correlation. The Sundsvall method is as reliable as the standard method. The evaluated radiographic measurement methods have the required validity and reliability to be used in clinical practice.

  • 167.
    Marklund, Sandra
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Feasibility Study of Phase Measurements of the Arterial Input Function in Dynamic Contrast Enhanced MRI2009Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

     

    Acquired data from dynamic contrast enhanced MRI measurements can be used to non-invasively assess tumour vascular characteristics through pharmacokinetic modelling. The modelling requires an arterial input function which is the concentration of contrast agent in the blood reaching the volume of interest as a function of time. The aim of this work is testing and optimizing a turboFLASH sequence to appraise its suitability for measuring the arterial input function by measuring phase.

    Contrast concentration measurements in a phantom were done with both phase and relaxivity techniques. The results were compared to simulations of the experiment conditions to compare the conformance. The results using the phase technique were promising, and the method was carried on to in-vivo testing. The in-vivo data displayed a large signal loss which motivated a new phantom experiment to examine the cause of this signal reduction. Dynamic measurements were made in a phantom with pulsatile flow to mimic a blood vessel with a somewhat modified turboFLASH sequence. The conclusions drawn from analyzing the data were used to further improve the sequence and this modified turboFLASH sequence was tested in an in-vivo experiment. The obtained concentration curve showed significant improvement and was deemed to be a good representation of the true blood concentration.

    The conclusion is that phase measurements can be recommended over relaxivity based measurements. This recommendation holds for using a slice selective saturation recovery turboFLASH sequence and measuring the arterial input function in the neck. Other areas of application need more thorough testing.

     

  • 168. Mattsson, Patrik
    et al.
    Forsberg, Anton
    Persson, Jonas
    Nyberg, Lars
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology.
    Nilsson, Lars-Göran
    Halldin, Christer
    Farde, Lars
    β-Amyloid binding in elderly subjects with declining or stable episodic memory function measured with PET and [11C]AZD21842015In: European Journal of Nuclear Medicine and Molecular Imaging, ISSN 1619-7070, E-ISSN 1619-7089, Vol. 42, no 10, p. 1507-1511Article in journal (Refereed)
    Abstract [en]

    Purpose: Cognitive decline has been suggested as an early marker for later onset of Alzheimer's disease. We therefore explored the relationship between decline in episodic memory and β-amyloid using positron emission tomography (PET) and [11C]AZD2184, a radioligand with potential to detect low levels of amyloid deposits. Methods: Healthy elderly subjects with declining (n = 10) or stable (n = 10) episodic memory over 15 years were recruited from the population-based Betula study and examined with PET. Brain radioactivity was measured after intravenous administration of [11C]AZD2184 The binding potential BP ND was calculated using linear graphical analysis with the cerebellum as reference region. Results: The binding of [11C]AZD2184 in total grey matter was generally low in the declining group, whereas some binding could be observed in the stable group. Mean BP ND was significantly higher in the stable group compared to the declining group (p = 0.019). An observation was that the three subjects with the highest BPND were ApoE ε4 allele carriers. Conclusions: We conclude that cognitive decline in the general population does not seem to stand by itself as an early predictor for amyloid deposits.

  • 169. McGale, Paul
    et al.
    Darby, Sarah C.
    Hall, Per
    Adolfsson, Jan
    Bengtsson, Nils-Olof
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
    Bennet, Anna M.
    Fornander, Tommy
    Gigante, Bruna
    Jensen, Maj-Britt
    Peto, Richard
    Rahimi, Kazem
    Taylor, Carolyn W.
    Ewertz, Marianne
    Incidence of heart disease in 35,000 women treated with radiotherapy for breast cancer in Denmark and Sweden2011In: Radiotherapy and Oncology, ISSN 0167-8140, E-ISSN 1879-0887, Vol. 100, no 2, p. 167-175Article in journal (Refereed)
    Abstract [en]

    Purpose: To study incidence of radiation-related heart disease in a large population of breast cancer patients followed for up to 30 years.

    Material and methods: 72,134 women diagnosed with breast cancer in Denmark or Sweden during 1976-2006 and followed prospectively. Radiation-related risk was studied by comparing women with left-sided and right-sided tumours.

    Results: 34,825 women (48%) received radiotherapy. Among unirradiated women tumour laterality had little relevance to heart disease. Among irradiated women mean dose to the whole heart was 6.3 Gy for left-sided tumours and 2.7 Gy for right-sided tumours. Mortality was similar in irradiated women with left-sided and right-sided tumours, but incidence ratios, left-sided versus right-sided, were raised: acute myocardial infarction 1.22 (95% CI 1.06-1.42), angina 1.25 (1.05-1.49), pericarditis 1.61 (1.06-2.43), valvular heart disease 1.54 (1.11-2.13). Incidence ratios for all heart disease were as high for women irradiated since 1990 (1.09 [1.00-1.19]) as for women irradiated during 1976-1989 (1.08 [0.99-1.17]), and were higher for women diagnosed with ischaemic heart disease prior to breast cancer than for other women (1.58 [1.19-2.10] versus 1.08 [1.01-1.15], p for difference = 0.01).

    Conclusions: Breast cancer radiotherapy has, at least until recently, increased the risk of developing ischaemic heart disease, pericarditis and valvular disease. Women with ischaemic heart disease before breast cancer diagnosis may have incurred higher risks than others. (C) 2011 Elsevier Ireland Ltd. All rights reserved. Radiotherapy and Oncology 100 (2011) 167-175

  • 170. Mota de Almeida, F. J.
    et al.
    Knutsson, K.
    Flygare, Lennart
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology.
    The effect of cone beam CT (CBCT) on therapeutic decision-making in endodontics2014In: Dento-Maxillo-Facial Radiology, ISSN 0250-832X, E-ISSN 1476-542X, Vol. 43, no 4, article id 20130137Article in journal (Refereed)
    Abstract [en]

    Objectives: The aim was to assess to what extent cone beam CT (CBCT) used in accordance with current European Commission guidelines in a normal clinical setting has an impact on therapeutic decisions in a population referred for endodontic problems.

    Methods: The study includes data of consecutively examined patients collected from October 2011 to December 2012. From 2 different endodontic specialist clinics, 57 patients were referred for a CBCT examination using criteria in accordance with current European guidelines. The CBCT examinations were performed using similar equipment and standardized among clinics. After a thorough clinical examination, but before CBCT, the examiner made a preliminary therapy plan which was recorded. After the CBCT examination, the same examiner made a new therapy plan. Therapy plans both before and after the CBCT examination were plotted for 53 patients and 81 teeth. As four patients had incomplete protocols, they were not included in the final analysis.

    Results: 4% of the patients referred to endodontic clinics during the study period were examined with CBCT. The most frequent reason for referral to CBCT examination was to differentiate pathology from normal anatomy, this was the case in 24 patients (45% of the cases). The primary outcome was therapy plan changes that could be attributed to CBCT examination. There were changes in 28 patients (53%).

    Conclusions: CBCT has a significant impact on therapeutic decision efficacy in endodontics when used in concordance with the current European Commission guidelines.

  • 171. Murayama, Yoshinobu
    et al.
    Lindahl, Olof A
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Sensitivity improvements of a resonance-based tactile sensor.2017In: Journal of Medical Engineering & Technology, ISSN 0309-1902, E-ISSN 1464-522X, Vol. 41, no 2, p. 131-140Article in journal (Refereed)
    Abstract [en]

    Resonance-based contact-impedance measurement refers to the application of resonance sensors based on the measurement of the changes in the resonance curve of an ultrasonic resonator in contact with a surface. The advantage of the resonance sensor is that it is very sensitive to small changes in the contact impedance. A sensitive micro tactile sensor (MTS) was developed, which measured the elasticity of soft living tissues at the single-cell level. In the present paper, we studied the method of improving the touch and stiffness sensitivity of the MTS. First, the dependence of touch sensitivity in relation to the resonator length was studied by calculating the sensitivity coefficient at each length ranging from 9 to 40 mm. The highest touch sensitivity was obtained with a 30-mm-long glass needle driven at a resonance frequency of 100 kHz. Next, the numerical calculation of contact impedance showed that the highest stiffness sensitivity was achieved when the driving frequency was 100 kHz and the contact-tip diameter of the MTS was 10 μm. The theoretical model was then confirmed experimentally using a phase-locked-loop-based digital feedback oscillation circuit. It was found that the developed MTS, whose resonant frequency was 97.030 kHz, performed with the highest sensitivity of 53.2 × 10(6) Hz/N at the driving frequency of 97.986 kHz, i.e. the highest sensitivity was achieved at 956 Hz above the resonant frequency.

  • 172.
    Mäkelä, Olli
    et al.
    Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland.
    Lammi, Mikko
    Department of Anatomy, University of Kuopio, Kuopio, Finland.
    Uusitalo, Hannele
    Department of Medical Biochemistry and Molecular Biology, University of Turku, Turku, Finland.
    Viitanen, Minna
    Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland.
    Hyttinen, Mika
    Department of Anatomy, University of Kuopio, Kuopio, Finland.
    Jurvelin, Jukka
    Department of Applied Physics, University of Kuopio, Kuopio, Finland.
    Vuorio, Eero
    Department of Medical Biochemistry and Molecular Biology, University of Turku, Turku, Finland.
    Helminen, Heikki
    Department of Anatomy, University of Kuopio, Kuopio, Finland.
    Tulamo, Riitta-Mari
    Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland.
    Effect of radiosynovectomy with holmium-166 ferric hydroxide macroaggregate on adult equine cartilage.2004In: Journal of Rheumatology, ISSN 0315-162X, E-ISSN 1499-2752, Vol. 31, no 2, p. 321-328, article id 14760804Article in journal (Refereed)
    Abstract [en]

    OBJECTIVE: To analyze the effect of radiosynovectomy with holmium-166 ferric hydroxide macroaggregate (166Ho-FHMA) on articular cartilage in 6 adult horses.

    METHODS: Arthritic changes and mechanical properties of articular cartilage were evaluated with arthroscopy and postmortem microscopic analyses. Glycosaminoglycan content was measured by safranin-O staining combined with digital densitometry, uronic acid analyses, and dimethylene blue binding assay. 35S-sulfate labeling and autoradiography were used to localize proteoglycan synthesis and to characterize proteoglycan structures using SDS-agarose gel electrophoresis. Northern hybridizations were performed to measure the mRNA levels for aggrecan and pro-a1(II) collagen in cartilage samples.

    RESULTS: Histological signs of degeneration were present in the articular cartilage of both control and radiosynovectomized equine joints. Radiosynovectomy did not aggravate degenerative changes or significantly alter the matrix glycosaminoglycan content. A slightly decreased size of proteoglycan monomers was observed 2 months after 166Ho-FHMA radiosynovectomy. Tissue analysis of extracted proteoglycans revealed lower 35S incorporation after radiosynovectomy, but corresponding changes could not be observed in aggrecan mRNA levels. Transient downregulation of pro-a1(II) collagen mRNA transcription was observed 5 days after 166Ho-FHMA radiosynovectomy.

    CONCLUSION: 166Ho-FHMA treatment did not markedly affect the composition or morphology of adult articular cartilage showing mild degeneration. However, minor degradation of proteoglycan monomers and transient downregulation of pro-a1(II) collagen mRNA were observed.

  • 173. Ménard, Cynthia
    et al.
    Paulson, Eric
    Nyholm, Tufve
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    McLaughlin, Patrick
    Liney, Gary
    Dirix, Piet
    van der Heide, Uulke A.
    Role of Prostate MR Imaging in Radiation Oncology2018In: The Radiologic clinics of North America, ISSN 0033-8389, E-ISSN 1557-8275, Vol. 56, no 2, p. 319-325Article in journal (Refereed)
    Abstract [en]

    The use of prostate MR imaging in radiotherapy continues to evolve. This article describes its current application in the selection of treatment regimens, integration in treatment planning or simulation, and assessment of response. An expert consensus statement from the annual MR in RT symposium is presented, as a list of 21 key quality indicators for the practice of MR imaging simulation in prostate cancer. Although imaging requirements generally follow PIRADSv2 guidelines, additional requirements specific to radiotherapy planning are described. MR imaging-only workflows and MR imaging-guided treatment systems are expected to replace conventional computed tomography-based practice, further adding specific requirements for MR imaging in radiotherapy.

  • 174.
    Mörén, Lina
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Wibom, Carl
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
    Bergström, Per
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
    Johansson, Mikael
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
    Antti, Henrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Bergenheim, A. Tommy
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Characterization of the serum metabolome following radiation treatment in patients with high-grade gliomas2016In: Radiation Oncology, ISSN 1748-717X, E-ISSN 1748-717X, Vol. 11, article id 51Article in journal (Refereed)
    Abstract [en]

    Background: Glioblastomas progress rapidly making response evaluation using MRI insufficient since treatment effects are not detectable until months after initiation of treatment. Thus, there is a strong need for supplementary biomarkers that could provide reliable and early assessment of treatment efficacy. Analysis of alterations in the metabolome may be a source for identification of new biomarker patterns harboring predictive information. Ideally, the biomarkers should be found within an easily accessible compartment such as the blood. Method: Using gas-chromatographic-time-of-flight-mass spectroscopy we have analyzed serum samples from 11 patients with glioblastoma during the initial phase of radiotherapy. Fasting serum samples were collected at admittance, on the same day as, but before first treatment and in the morning after the second and fifth dose of radiation. The acquired data was analyzed and evaluated by chemometrics based bioinformatics methods. Our findings were compared and discussed in relation to previous data from microdialysis in tumor tissue, i.e. the extracellular compartment, from the same patients. Results: We found a significant change in metabolite pattern in serum comparing samples taken before radiotherapy to samples taken during early radiotherapy. In all, 68 metabolites were lowered in concentration following treatment while 16 metabolites were elevated in concentration. All detected and identified amino acids and fatty acids together with myo-inositol, creatinine, and urea were among the metabolites that decreased in concentration during treatment, while citric acid was among the metabolites that increased in concentration. Furthermore, when comparing results from the serum analysis with findings in tumor extracellular fluid we found a common change in metabolite patterns in both compartments on an individual patient level. On an individual metabolite level similar changes in ornithine, tyrosine and urea were detected. However, in serum, glutamine and glutamate were lowered after treatment while being elevated in the tumor extracellular fluid. Conclusion: Cross-validated multivariate statistical models verified that the serum metabolome was significantly changed in relation to radiation in a similar pattern to earlier findings in tumor tissue. However, all individual changes in tissue did not translate into changes in serum. Our study indicates that serum metabolomics could be of value to investigate as a potential marker for assessing early response to radiotherapy in malignant glioma.

  • 175. Møllerløkken, Ole J
    et al.
    Moen, Bente E
    Baste, Valborg
    Magerøy, Nils
    Oftedal, Gunnhild
    Neto, Emanuel
    Ersland, Lars
    Bjørge, Line
    Torjesen, Peter A
    Hansson Mild, Kjell
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    No effects of MRI scan on male reproduction hormones2012In: Reproductive Toxicology, ISSN 0890-6238, E-ISSN 1873-1708, Vol. 34, no 1, p. 133-139Article in journal (Refereed)
    Abstract [en]

    Magnetic resonance imaging (MRI) is increasing around the world and the possible adverse effects on reproductive health of electromagnetic fields (EMFs) in MRI are not previously studied. A prospective randomized balanced cross-over study using a head scan in real MRI with whole-body transmitting coil and sham MRI among 24 healthy male volunteers was conducted. Serum-blood samples of inhibin B, testosterone, prolactine, thyreotropine, luteinizing hormone, follicle stimulating hormone, sex-hormone binding globuline and estradiol were taken before and after the different scans. Neither immediately after, nor after 11 days were there seen any differences in the hormone levels comparing real and sham MRI. The lack of effects of EMF on male reproductive hormones should be reassuring to the public and especially for men examined in MRI. Adverse effects on other endpoints than male reproduction or possible chronic effect of multiple MRI scans have not been investigated in this study.

  • 176.
    Nicoll, Rachel
    et al.
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine. Ctr Heart, Umea, Sweden.
    Wiklund, Urban
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Zhao, Y.
    Diederichsen, A.
    Mickley, H.
    Ovrehus, K.
    Zamorano, P.
    Gueret, P.
    Schmermund, A.
    Maffei, E.
    Cademartiri, F.
    Budoff, M.
    Henein, M.
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    The coronary calcium score is a more accurate predictor of significant coronary stenosis than conventional risk factors in symptomatic patients: Euro-CCAD study2016In: International Journal of Cardiology, ISSN 0167-5273, E-ISSN 1874-1754, Vol. 207, p. 13-19Article in journal (Refereed)
    Abstract [en]

    Aims: In this retrospective study we assessed the predictive value of the coronary calcium score for significant (>50%) stenosis relative to conventional risk factors. Methods and Results: We investigated 5515 symptomatic patients from Denmark, France, Germany, Italy, Spain and the USA. All had risk factor assessment, computed tomographic coronary angiogram (CTCA) or conventional angiography and a CT scan for coronary artery calcium (CAC) scoring. 1539 (27.9%) patients had significant stenosis, 5.50 of whom had zero CAC. In 5074 patients, multiple binary regression showed the most important predictor of significant stenosis to be male gender (B = 1.07) followed by diabetes mellitus (B = 0.70) smoking, hypercholesterolaemia, hypertension, family history of CAD and age but not obesity. When the log transformed CAC score was included, it became the most powerful predictor (B = 1.25), followed by male gender (B = 0.48), diabetes, smoking, family history and age but hypercholesterolaemia and hypertension lost significance. The CAC score is a more accurate predictor of >50% stenosis than risk factors regardless of the means of assessment of stenosis. The sensitivity of risk factors, CAC score and the combination for prediction of >50% stenosis when measured by conventional angiogram was considerably higher than when assessed by CTCA but the specificity was considerably higher when assessed by CTCA. The accuracy of CTCA for predicting >50% stenosis using the CAC score alone was higher (AUC 0.85) than using a combination of the CAC score and risk factors with conventional angiography (AUC 0.81). Conclusion: In symptomatic patients, the CAC score is a more accurate predictor of significant coronary stenosis than conventional risk factors.

  • 177.
    Nilsson, Tore
    Umeå University, Faculty of Medicine, Odontology.
    Simulation supported training in oral radiology: methods and impact on interpretative skill2007Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Simulation is an important tool when training is hazardous, time consuming, or expensive. Simulation can also be used to enhance reality by adding features normally not available in the real world. The aim with this work has been to develop and evaluate methods that could improve learning in oral radiology utilising a radiation-free simulator environment.

    Virtual reality software for radiographic examinations was developed. The virtual environment consisted of a model of a patient, an x-ray machine, and a film. Simulated radiographic images of the patient model could be rendered as perspective projections based on the relative position between the individual models. The software was incorporated in an oral radiology simulator with a training program for interpretation of spatial relations in radiographs. Projection geometry was validated by comparing length dimensions in simulated radiographs with the corresponding theoretically calculated distances. The results showed that projection error in the simulated images never exceeded 0.5 mm.

    Dental students participated in studies on skill in interpreting spatial information in radiographs utilising parallax. Conventional and simulator based training methods were used. Training lasted for 90 minutes. Skill in interpreting spatial information was assessed with a proficiency test before training, immediately after training, and eight months after training. Visual-spatial ability was assessed with mental rotations test, version A (MRT-A). Regression analysis revealed a significant (P<0.01) association between visual-spatial ability and proficiency test results after training. At simulator training, proficiency test results immediately after training were significantly higher than before training (P<0.01). Among students with low MTR-A scores, improvement after simulator training was higher than after conventional training. Eight months after simulator training proficiency test results were lower than immediately after training. The test results were, however, still higher than before training.

    In conclusion, the simulation software produces simulated radiographs of high geometric accuracy. Acquisition of skill to interpret spatial relations in radiographs is facilitated for individuals with high visual-spatial ability. Simulator training improves acquisition of interpretative skill and is especially beneficial for individuals with low visual-spatial ability. The results indicate that radiology simulation can be an effective training method.

  • 178.
    Nordmark, Lars
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Angiografi av arteria testicularis1979Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In addition all patients examined by means of using testicular angiography before the first of November 1978» have been included. 123 patients were intended for angiography, 13 of them bilaterally.

    The intention with the investigation was to determine whether selective angiography of the testicular artery might be a useful examination in cases of a non-palpable testis and in patients with different intrascrotal lesions.

    There is a description of a useful method of investigation. The normal angiographic anatomy of the testicular artery is also de­scribed, both retroperitoneally and in the scrotum. In cases with a non-palpable testis it is shown that it is easy to distinguish between agenesis and cryptorchism.

    The normal magnification angiography of the testis is shown and how various intrascrotal lesions alter the picture.

    Finally some cases with retroperitoneal lesions are presented in which the testicular artery is committed.

  • 179.
    Nyberg, Lars
    et al.
    Umeå University, Faculty of Medicine, Umeå Centre for Functional Brain Imaging (UFBI). Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology. Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Lövdén, Martin
    Aging Research Center, Karolinska Institutet, Stockholm, Sweden.
    Riklund, Katrine
    Umeå University, Faculty of Medicine, Umeå Centre for Functional Brain Imaging (UFBI). Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology.
    Lindenberger, Ulman
    Center for Lifespan Psychology, Max Planck Institute for Human Development, Berlin, Germany.
    Bäckman, Lars
    Aging Research Center, Karolinska Institutet, Stockholm, Sweden.
    Memory aging and brain maintenance2012In: Trends in cognitive sciences, ISSN 1364-6613, E-ISSN 1879-307X, Vol. 16, no 5, p. 292-305Article in journal (Refereed)
    Abstract [en]

    Episodic memory and working memory decline with advancing age. Nevertheless, large-scale population-based studies document well-preserved memory functioning in some older individuals. The influential 'reserve' notion holds that individual differences in brain characteristics or in the manner people process tasks allow some individuals to cope better than others with brain pathology and hence show preserved memory performance. Here, we discuss a complementary concept, that of brain maintenance (or relative lack of brain pathology), and argue that it constitutes the primary determinant of successful memory aging. We discuss evidence for brain maintenance at different levels: cellular, neurochemical, gray- and white-matter integrity, and systems-level activation patterns. Various genetic and lifestyle factors support brain maintenance in aging and interventions may be designed to promote maintenance of brain structure and function in late life.

  • 180.
    Nyholm, Tufve
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Verification of dose calculations in radiotherapy2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    External radiotherapy is a common treatment technique for cancer. It has been shown that radiation therapy is a both clinically and economically effective treatment for many types of cancer, even though the equipment is expensive. The technology is in constant evolution and more and more sophisticated and complex techniques are introduced. One of the main tasks for physicists at a radiotherapy department is quality control, i.e. making sure that the treatments are delivered in accordance with the dosimetric intentions. Over dosage of radiation can lead to severe side effects, while under dosage reduces the probability for patient cure.

    The present thesis is mainly focused on the verification of the calculated dose. Requirements for independent dose calculation software are identified and the procedures using such software are described. In the publications included in the thesis an algorithm specially developed for verification of dose calculations is described and tested. The calculation uncertainties connected with the described algorithm are investigated and modeled. A brief analysis of the quality assurance procedures available and used in external radiotherapy is also included in the thesis.

    The main conclusion of the thesis is that independent verification of the dose calculations is feasible in an efficient and cost effective quality control system. The independent calculations do not only serve as a protection against accidents, but can also be the basis for comparisons of the dose calculation performance at different clinics.

  • 181.
    Nyholm, Tufve
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics. Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
    Jonsson, Joakim
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Söderström, Karin
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
    Bergström, Per
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
    Carlberg, Andreas
    Frykholm, Gunilla
    Behrens, Claus F.
    Geertsen, Poul Flemming
    Trepiakas, Redas
    Hanvey, Scott
    Sadozye, Azmat
    Ansari, Jawaher
    McCallum, Hazel
    Frew, John
    McMenemin, Rhona
    Zackrisson, Björn
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
    Variability in prostate and seminal vesicle delineations defined on magnetic resonance images, a multi-observer, -center and -sequence study2013In: Radiation Oncology, ISSN 1748-717X, E-ISSN 1748-717X, Vol. 8, p. 126-Article in journal (Refereed)
    Abstract [en]

    Background: The use of magnetic resonance (MR) imaging as a part of preparation for radiotherapy is increasing. For delineation of the prostate several publications have shown decreased delineation variability using MR compared to computed tomography (CT). The purpose of the present work was to investigate the intra- and inter-physician delineation variability for prostate and seminal vesicles, and to investigate the influence of different MR sequence settings used clinically at the five centers participating in the study.

    Methods: MR series from five centers, each providing five patients, were used. Two physicians from each center delineated the prostate and the seminal vesicles on each of the 25 image sets. The variability between the delineations was analyzed with respect to overall, intra-and inter-physician variability, and dependence between variability and origin of the MR images, i.e. the MR sequence used to acquire the data.

    Results: The intra-physician variability in different directions was between 1.3 - 1.9 mm and 3 - 4 mm for the prostate and seminal vesicles respectively (1 std). The inter-physician variability for different directions were between 0.7 - 1.7 mm and approximately equal for the prostate and seminal vesicles. Large differences in variability were observed for individual patients, and also for individual imaging sequences used at the different centers. There was however no indication of decreased variability with higher field strength.

    Conclusion: The overall delineation variability is larger for the seminal vesicles compared to the prostate, due to a larger intra-physician variability. The imaging sequence appears to have a large influence on the variability, even for different variants of the T2-weighted spin-echo based sequences, which were used by all centers in the study.

  • 182.
    Nyholm, Tufve
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Karlsson, Magnus
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Karlsson, Mikael
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    MR based treatment workflow for external radiotherapy of prostate cancer2009In: World Congress on Medical Physics and Biomedical Engineering, September 7 - 12, 2009, Munich, Germany, Berlin: Springer , 2009, p. 60-63Conference paper (Refereed)
    Abstract [en]

    The requirements on spatial accuracy are high in external radiotherapy of prostate cancer. The technical achievements in image guided radiotherapy (IGRT) during the recent years have lead to a significant improvement of teh daily positioning accuracy. Improved accuracy has made it possible to reduce the margin between the clinical target volume and the planning target volume, thus reduce the risk for normal tissue complications.MRI is to prefer to CT for delineation of the prostate target because of superior soft tissue contrast. Recent studies have shown that the dosimetric accuracy of dose calculations on MR material is acceptable. In the present work we analyze the spatial uncertainties that are connected to workflows where the CT has been excluded.We found that accuracy increase with a fully MR based workflow. The main reason is that the MR based workflow does not require any registration between MR and CT to enable target delineation on the MR series. Two different methodologies for patient positioning with MR as baseline were identified: A. Implanted fiducial markers with portal imaging at each treatment session. B. Imaging of the patient in the MR at every treatment session to localize the prostate. We found that the two positioning methods give equivalent spatial accuracy. The estimated required margins for the MR based workflows was around 8 mm, corresponding numbers for a CT based workflow using the same assessment methods was around 10 mm.

  • 183.
    Nyholm, Tufve
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics. Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
    Mullaney, Tara
    Umeå University, Faculty of Science and Technology, Umeå Institute of Design.
    Olsson, L. E.
    Finnilä, Kristina
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
    Zackrisson, Björn
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
    MRI in radiotherapy - Is it time to rethink the current radiotherapy fixation solutions?2014In: Journal of Applied Clinical Medical Physics, ISSN 1526-9914, E-ISSN 1526-9914, Vol. 15, no 6, p. 360-361Article in journal (Refereed)
  • 184.
    Nyholm, Tufve
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Olsson, C.
    Skönevik, Johan
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Gunnlaugsson, A.
    Valdman, A.
    Johnsson, S.
    Zackrisson, Björn
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Nationwide Collection of Structured RT Data in Sweden2017In: Medical physics (Lancaster), ISSN 0094-2405, Vol. 44, no 6, p. 3241-3241Article in journal (Other academic)
  • 185.
    Nyholm, Tufve
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences. Medical Radiation Physics, Department of Immunology, Genetics and Pathology, Uppsala University.
    Olsson, Caroline
    Agrup, Måns
    Björk, Peter
    Björk-Eriksson, Thomas
    Gagliardi, Giovanna
    Grinaker, Hanne
    Gunnlaugsson, Adalsteinn
    Gustafsson, Anders
    Gustafsson, Magnus
    Johansson, Bengt
    Johnsson, Stefan
    Karlsson, Magnus
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Kristensen, Ingrid
    Nilsson, Per
    Nyström, Leif
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Onjukka, Eva
    Reizenstein, Johan
    Skönevik, Johan
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Söderström, Karin
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Valdman, Alexander
    Zackrisson, Björn
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Montelius, Anders
    A national approach for automated collection of standardized and population-based radiation therapy data in Sweden2016In: Radiotherapy and Oncology, ISSN 0167-8140, E-ISSN 1879-0887, Vol. 119, no 2, p. 344-350Article in journal (Refereed)
    Abstract [en]

    Purpose: To develop an infrastructure for structured and automated collection of interoperable radiation therapy (RT) data into a national clinical quality registry.

    Materials and methods: The present study was initiated in 2012 with the participation of seven of the 15 hospital departments delivering RT in Sweden. A national RT nomenclature and a database for structured unified storage of RT data at each site (Medical Information Quality Archive, MIQA) have been developed. Aggregated data from the MIQA databases are sent to a national RT registry located on the same IT platform (INCA) as the national clinical cancer registries.

    Results: The suggested naming convention has to date been integrated into the clinical workflow at 12 of 15 sites, and MIQA is installed at six of these. Involvement of the remaining 3/15 RT departments is ongoing, and they are expected to be part of the infrastructure by 2016. RT data collection from ARIA (R), Mosaiq (R), Eclipse (TM), and Oncentra (R) is supported. Manual curation of RT-structure information is needed for approximately 10% of target volumes, but rarely for normal tissue structures, demonstrating a good compliance to the RT nomenclature. Aggregated dose/volume descriptors are calculated based on the information in MIQA and sent to INCA using a dedicated service (MIQA2INCA). Correct linkage of data for each patient to the clinical cancer registries on the INCA platform is assured by the unique Swedish personal identity number.

    Conclusions: An infrastructure for structured and automated prospective collection of syntactically inter operable RT data into a national clinical quality registry for RT data is under implementation. Future developments include adapting MIQA to other treatment modalities (e.g. proton therapy and brachytherapy) and finding strategies to harmonize structure delineations. How the RT registry should comply with domain-specific ontologies such as the Radiation Oncology Ontology (ROO) is under discussion. 

  • 186.
    Nyman, Emma
    et al.
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Lindqvist, Per
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Näslund, Ulf
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Risk marker variability in subclinical carotid plaques based on ultrasound is influenced by cardiac phase, echogenicity and size2018In: Ultrasound in Medicine and Biology, ISSN 0301-5629, E-ISSN 1879-291X, Vol. 44, no 8, p. 1742-1750Article in journal (Refereed)
    Abstract [en]

    Identification of risk markers based on quantitative ultrasound texture analysis of carotid plaques has the ability to define vulnerable components that correlate with increased cardiovascular risk. However, data describing factors with the potential to influence the measurement variability of risk markers are limited. The aim of this study was to evaluate the influence of electrocardiogram-guided image selection, plaque echogenicity and area on carotid plaque risk markers and their variability in asymptomatic carotid plaques. Plaque risk markers were measured in 57 plaques during three consecutive heartbeats at two cardiac cycle time instants corresponding to the electrocardiogram R-wave (end diastole) and end of T-wave (end systole), resulting in six measurements for each plaque. Risk marker variability was quantified by computing the coefficient of variation (CV) across the three heartbeats. The CV was significantly higher for small plaques (area <15 mm2, 10%) than for large plaques (area >15 mm2, 6%) (p <0.001) in measurements of area, and the CV for measurements of gray-scale median were higher for echolucent plaques (<40, 15%) than for echogenic plaques (>40, 9%) (p <0.001). No significant differences were found between systole and diastole for the mean of any risk marker or the corresponding CV value. However, in a sub-analysis, the echolucent plaques were found to have a higher CV during systole compared with diastole. The variability also caused plaque type reclassification in 16% to 25% of the plaques depending on cutoff value. The results of this study indicate that echolucent and small plaques each contribute to increased risk marker variability. Based on these results, we recommend that measurements in diastole arc preferred to reduce variation, although we found that it may not be possible to characterize small plaques accurately using contemporary applied risk markers. 

  • 187.
    Nyström, Lennarth
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Epidemiology and Global Health.
    The Swedish randomised controlled trial on mammography screening has been properly designed, conducted and analysed2015In: Journal of the Royal Society of Medicine, ISSN 0141-0768, E-ISSN 1758-1095, Vol. 108, no 11, p. 429-430Article in journal (Refereed)
  • 188. Ohman, A
    et al.
    Kivijärvi, K
    Blombäck, U
    Flygare, Lennart
    Department of Radiology, Sunderby Hospital, SE-971 80, Luleå, Sweden.
    Pre-operative radiographic evaluation of lower third molars with computed tomography2006In: Dento-Maxillo-Facial Radiology, ISSN 0250-832X, E-ISSN 1476-542X, Vol. 35, no 1, p. 30-35Article in journal (Refereed)
    Abstract [en]

    OBJECTIVES: To report radiographic findings of examinations with computed tomography (CT) of impacted lower third molars with an intimate relation to the mandibular canal and to investigate how findings of a dark band across the roots of the lower third molar on panoramic views correspond to the CT findings.

    METHODS: CT images of 90 lower third molars (64 patients, mean age 34.6 years) in which plain radiography was insufficient to allow determination of the precise anatomical relations were reviewed retrospectively. Panoramic views of 88 teeth existed; these images were interpreted independent of the CT examinations with respect to presence of a dark band across the roots.

    RESULTS: In 31% of the CT images, the course of the mandibular canal was buccal, in 33% lingual, in 26% inferior, and in 10% inter-radicular. The tooth was in contact with the mandibular canal in 94% and with the lingual cortex in 86%. In 23%, grooving of the root by the canal was judged to be present. In 63% of the cases where a dark band across the roots was observed on panoramic radiographs, CT revealed grooving of the root.

    CONCLUSIONS: Pre-operative CT of lower third molars is motivated in selected cases when plain radiography is inconclusive. The finding of a dark band across the roots on panoramic radiographs is an indicator of grooving of the tooth by the canal and justifies a pre-operative CT examination. The absence of dark bands on panoramic views does not exclude grooving of the roots.

  • 189.
    Olofsson, Jörgen
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Developing and evaluating dose calculation models for verification of advanced radiotherapy2006Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    A prerequisite for modern radiotherapy is the ability to accurately determine the absorbed dose (D) that is given to the patient. The subject of this thesis has been to develop and evaluate efficient dose calculation models for high-energy photon beams delivered by linear accelerators. Even though the considered calculation models are general, the work has been focused on quality assurance (QA) tools used to independently verify the dose for individual treatment plans. The purpose of this verification is to guarantee patient safety and to improve the treatment outcome. Furthermore, a vital part of this work has been to explore the prospect of estimating the dose calculation uncertainties associated with individual treatment setups. A discussion on how such uncertainty estimations can facilitate improved clinical QA procedures by providing appropriate action levels has also been included within the scope of this thesis.

    In order to enable efficient modelling of the physical phenomena that are involved in dose output calculations it is convenient to divide them into two main categories; the first one dealing with the radiation exiting the accelerator’s treatment head and a second one associated with the subsequent energy deposition processes. A multi-source model describing the distribution of energy fluence emitted from the treatment head per delivered monitor unit (MU) is presented and evaluated through comparisons with measurements in multiple photon beams and collimator settings. The calculations show close agreement with the extensive set of experimental data, generally within +/-1% of corresponding measurements.

    The energy (dose) deposition in the irradiated object has been modelled through a photon pencil kernel solely based on a beam quality index (TPR20,10). This model was evaluated in a similar manner as the multi-source model at three different treatment depths. A separate study was focused on the specific difficulties associated with dose calculations in points located at a distance from the central beam axis. Despite the minimal input data required to characterize individual photon beams, the accuracy proved to be very good when comparing the calculated results with experimental data.

    The evaluated calculation models were finally used to analyse how well the lateral dose distributions from typical megavoltage photon beams are optimized with respect to the resulting beam flatness characteristics. The results did not reveal any obvious reasons why different manufacturers should provide different lateral dose distributions. Furthermore, the performed lateral optimizations indicate that there is room for improved flatness performance for the investigated linear accelerators.

  • 190.
    Olofsson, Lennart
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Energy and intensity modulated radiation therapy with electrons2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In recent years intensity modulated radiation therapy with photons (xIMRT) has gained attention due to its ability to reduce the dose in the tissues close to the tumour volume. However, this technique also results in a large low dose volume. Electron IMRT (eIMRT) has the potential to reduce the integral dose to the patient due to the dose fall off in the electron depth dose curves. This dose fall off makes it possible to modulate the dose distribution in the direction of the beam by selecting appropriate electron energies. The use of a computer based energy selection method was examined in combination with the IMRT technique to optimise the electron dose distribution. It is clearly illustrated that the energy optimisation procedure reduces the dose to lung and heart in a breast cancer treatment.

    To shape the multiple electron subfields (beamlets) that are used in eIMRT, an electron multi leaf collimator (eMLC) is needed. However, photons produced in a conventional electron treatment head could penetrate such an added eMLC, thus producing an undesirable dose contribution. The leakage levels normally achieved are acceptable for standard single electron field treatments but could become unacceptably high in eIMRT treatments where a lot of small subfields are combined. To limit this photon contribution, the photon MLC (xMLC) was used to shield off large parts of the photon leakage.

    The effect of this xMLC shielding on the reduction of photon leakage, the electron beam penumbras, and electron output (dose level), was studied using Monte Carlo methods for different electron treatment head designs. The use of helium as a mean to reduce the electron scatter in the treatment head, and thus the perturbating effect of the xMLC on electron beam penumbra and output, was also investigated.

    This thesis shows that the effect of the xMLC shielding on the electron beam penumbra and output can be made negligible while still obtaining a significantly reduced x-ray leakage dose contribution. The result is a large gain in radiation protection of the patient and a better dynamic range for the eIMRT dose optimisation. For this optimisation a computer based electron energy selection method was developed and tested on two clinical cases.

  • 191.
    Parkkinen, Jyrki
    et al.
    Departmen of Anatomy,University of Kuopio, Kuopio, Finland.
    Paukkonen, Kari
    Departmen of Anatomy, University of Kuopio, Kuopio, Finland.
    Pesonen, Erkki
    Departmen of Computer Science and Applied Mathematics, University of Kuopio, Kuopio, Finland.
    Lammi, Mikko
    Departmen of Anatomy, University of Kuopio, Kuopio, Finland.
    Markkanen, Seppo
    Departmen of Anatomy, University of Kuopio, Kuopio, Finland.
    Helminen, Heikki
    Departmen of Anatomy, University of Kuopio, Kuopio, Finland.
    Tammi, Markku
    Departmen of Anatomy, University of Kuopio, Kuopio, Finland.
    Quantitation of autoradiographic grains in different zones of articular cartilage with image analyzer.1990In: Histochemistry, ISSN 0301-5564, Vol. 93, no 3, p. 241-245, article id 2312351Article in journal (Refereed)
    Abstract [en]

    A novel method is introduced for the estimation of grain numbers in autoradiographic sections of articular cartilage with an image analyzer. It is based on separation of grains from the underlying structures by gray level thresholding and determination of the percentage of total area occupied by grains in a relatively large measuring field. The mean grain size is used as a reference to calculate grain numbers per cell profile and per unit area of tissue in various zones of bovine articular cartilage labelled with 35S-sulphate in tissue culture. The results demonstrate considerable zonal differences as well as site related topographic variation in the rate of 35S-sulphate incorporation. The largest site-related variation in the grain counts was observed in the superficial zone, suggesting a delicate control of proteoglycan synthesis in this zone.

  • 192. Persson, Emilia
    et al.
    Gustafsson, Christian
    Nordström, Fredrik
    Sohlin, Maja
    Gunnlaugsson, Adalsteinn
    Petruson, Karin
    Rintelä, Niina
    Hed, Kristoffer
    Blomqvist, Lennart
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Zackrisson, Björn
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Nyholm, Tufve
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Olsson, Lars E.
    Siversson, Carl
    Jonsson, Joakim
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    MR-OPERA: a multicenter/multivendor validation of magnetic resonance imaging–only prostate treatment planning using synthetic computed tomography images2017In: International Journal of Radiation Oncology, Biology, Physics, ISSN 0360-3016, E-ISSN 1879-355X, Vol. 99, no 3, p. 692-700Article in journal (Refereed)
    Abstract [en]

    Purpose: To validate the dosimetric accuracy and clinical robustness of a commercially available software for magnetic resonance (MR) to synthetic computed tomography (sCT) conversion, in an MR imaging–only workflow for 170 prostate cancer patients.

    Methods and Materials: The 4 participating centers had MriPlanner (Spectronic Medical), an atlas-based sCT generation software, installed as a cloud-based service. A T2-weighted MR sequence, covering the body contour, was added to the clinical protocol. The MR images were sent from the MR scanner workstation to the MriPlanner platform. The sCT was automatically returned to the treatment planning system. Four MR scanners and 2 magnetic field strengths were included in the study. For each patient, a CT-treatment plan was created and approved according to clinical practice. The sCT was rigidly registered to the CT, and the clinical treatment plan was recalculated on the sCT. The dose distributions from the CT plan and the sCT plan were compared according to a set of dose-volume histogram parameters and gamma evaluation. Treatment techniques included volumetric modulated arc therapy, intensity modulated radiation therapy, and conventional treatment using 2 treatment planning systems and different dose calculation algorithms.

    Results: The overall (multicenter/multivendor) mean dose differences between sCT and CT dose distributions were below 0.3% for all evaluated organs and targets. Gamma evaluation showed a mean pass rate of 99.12% (0.63%, 1 SD) in the complete body volume and 99.97% (0.13%, 1 SD) in the planning target volume using a 2%/2-mm global gamma criteria.

    Conclusions: Results of the study show that the sCT conversion method can be used clinically, with minimal differences between sCT and CT dose distributions for target and relevant organs at risk. The small differences seen are consistent between centers, indicating that an MR imaging–only workflow using MriPlanner is robust for a variety of field strengths, vendors, and treatment techniques.

  • 193. Persson, Mats
    et al.
    Bujila, Robert
    Nowik, Patrik
    Andersson, Henrik
    Kull, Love
    Andersson, Jonas
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Bornefalk, Hans
    Danielsson, Mats
    Upper limits of the photon fluence rate on CT detectors: case study on a commercial scanner2016In: Medical physics (Lancaster), ISSN 0094-2405, Vol. 43, no 7, p. 4398-4411Article in journal (Refereed)
    Abstract [en]

    Purpose: The highest photon fluence rate that a computed tomography (CT) detector must be able to measure is an important parameter. The authors calculate the maximum transmitted fluence rate in a commercial CT scanner as a function of patient size for standard head, chest, and abdomen protocols.

    Methods: The authors scanned an anthropomorphic phantom (Kyoto Kagaku PBU-60) with the reference CT protocols provided by AAPM on a GE LightSpeed VCT scanner and noted the tube current applied with the tube current modulation (TCM) system. By rescaling this tube current using published measurements on the tube current modulation of a GE scanner [N. Keat, “CT scanner automatic exposure control systems,” MHRA Evaluation Report 05016, ImPACT, London, UK, 2005], the authors could estimate the tube current that these protocols would have resulted in for other patient sizes. An ECG gated chest protocol was also simulated. Using measured dose rate profiles along the bowtie filters, the authors simulated imaging of anonymized patient images with a range of sizes on a GE VCT scanner and calculated the maximum transmitted fluence rate. In addition, the 99th and the 95th percentiles of the transmitted fluence rate distribution behind the patient are calculated and the effect of omitting projection lines passing just below the skin line is investigated.

    Results: The highest transmitted fluence rates on the detector for the AAPM reference protocols with centered patients are found for head images and for intermediate-sized chest images, both with a maximum of 3.4 ⋅ 108 mm−2 s−1, at 949 mm distance from the source. Miscentering the head by 50 mm downward increases the maximum transmitted fluence rate to 5.7 ⋅ 108 mm−2 s−1. The ECG gated chest protocol gives fluence rates up to 2.3 ⋅ 108 − 3.6 ⋅ 108 mm−2 s−1 depending on miscentering.

    Conclusions: The fluence rate on a CT detector reaches 3 ⋅ 108 − 6 ⋅ 108 mm−2 s−1 in standard imaging protocols, with the highest rates occurring for ECG gated chest and miscentered head scans. These results will be useful to developers of CT detectors, in particular photon counting detectors.

  • 194.
    Persson, My
    Umeå University, Faculty of Medicine, Department of Nursing.
    "Den värsta tiden i mitt liv...": En litteraturstudie om kvinnors upplevelser i samband med trippeldiagnostik vid misstänkt bröstcancer2014Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Background: Breast cancer is one of the most common cancer diseases for women. With the help of regular participation of mammography screening there is a high rate of finding breast cancer in an early state. Another way to find breast cancer is when women feel something abnormal in their breast, for example a lump. To diagnose breast cancer you use examinations such as mammography and ultrasound with possible biopsy sample, these examinations are called triple diagnosis. Through the experience of suspecting breast cancer, during the breast examinations until the moment women get their diagnosis different feelings arise. Aim: The aim of this literature study was to elucidate women's lived experience during the triple diagnosis of suspected breast cancer disease. Method: Eight scientific articles were found through database searching on the databases CINAHL and Scopus. Manual search were also made. The search and analyzing were made to fulfill the purpose of this literature study. Results: The eight analyzed articles were summed up to three categories and six subcategories. These categories were “Communication at the time of the examination”, “Examination-experience” and “In the process of waiting for results”. Conclusions: Women who suspect having breast cancer experienced the feelings of fear, worry and anxiety throughout the whole process until diagnosis. The literature study “The worst time of my life…” gives X-ray nurses an insight of women‘s lived experiences of the examinations through their time of suspected breast cancer. With this insight x-ray nurses learn to inform, examine and meet their patients professionally and with respect.

  • 195.
    Peters, Bjorn
    et al.
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Andersson, Yvonne
    Stegmayr, Bernd
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Mölne, Johan
    Jensen, Gert
    Dahlberg, Per
    Holm-Gunnarsson, Inger
    Ekberg, Jana
    Bjurström, Karl
    Haux, Stina-Britta
    Hadimeri, Henrik
    A study of clinical complications and risk factors in 1001 native and transplant kidney biopsies in Sweden2014In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 55, no 7, p. 890-896Article in journal (Refereed)
    Abstract [en]

    Background: In Sweden, native and transplant kidney biopsies are usually performed in major renal medical centers. Purpose: To clarify risk factors in native and transplant kidney biopsies to improve patient safety. Material and Methods: A total of 1001 biopsies (in 352 women and 565 men) were included. The median age was 54 years (range, 16-90 years). Data were derived from 826 native kidney biopsies (640 prospective and 186 retrospective) and 175 transplant kidney biopsies (170 prospective and 5 retrospective). Various factors and complications were registered while performing native and transplant kidney biopsies, focusing on major (e. g. blood transfusions, invasive procedures) and minor complications. The prospective protocol was used at six centers and at one center data were obtained retrospectively. Results: Women were at greater risk of overall complications than men (12.2% vs. 6.5%; P = 0.003; odds ratio [OR], 2.0; confidence interval [CI], 1.3-3.1) as well as of major complications (9.6% vs. 4.5%; P = 0.002; OR, 2.2, CI 1.3-3.7). Major complications occurred more commonly after biopsies from the right kidney, in women than in men (10.8% vs. 3.1%; P = 0.005; OR, 3.7; CI, 1.5-9.5), and in patients with lower BMI (25.5 vs. 27.3, P = 0.016) and of younger age (45 years vs. 52.5 years; P = 0.001). Lower mean arterial pressure in transplant kidney biopsies indicated a risk of major complications (90 mmHg vs. 98 mmHg; P = 0.039). Factors such as needle size, number of passes, serum creatinine, and eGFR did not influence complication rates. Conclusion: The present findings motivate greater attention being paid to the risk of major side-effects after right-side biopsies from women's kidneys, as well as after biopsies from younger patients and patients with lower BMI.

  • 196. Pixberg, Caroline
    et al.
    Koch, Raphael
    Eich, Hans Theodor
    Martinsson, Ulla
    Kristensen, Ingrid
    Matuschek, Christiane
    Kortmann, Rolf-Dieter
    Pohl, Fabian
    Elsayad, Khaled
    Christiansen, Hans
    Willich, Normann
    Lindh, Jack
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Steinmann, Diana
    Acute Toxicity Grade 3 and 4 After Irradiation in Children and Adolescents: Results From the IPPARCA Collaboration2016In: International Journal of Radiation Oncology, Biology, Physics, ISSN 0360-3016, E-ISSN 1879-355X, Vol. 94, no 4, p. 792-799Article in journal (Refereed)
    Abstract [en]

    Purpose: In the context of oncologic therapy for children, radiation therapy is frequently indicated. This study identified the frequency of and reasons for the development of high-grade acute toxicity and possible sequelae.

    Materials and Methods: Irradiated children have been prospectively documented since 2001 in the Registry for the Evaluation of Side Effects After Radiation in Childhood and Adolescence (RiSK) database in Germany and since 2008 in the registry for radiation therapy toxicity (RADTOX) in Sweden. Data were collected using standardized, published forms. Toxicity classification was based on Radiation Therapy Oncology Group/European Organization for Research and Treatment of Cancer criteria.

    Results: As of June 2013, 1500 children have been recruited into the RiSK database and 485 into the RADTOX registry leading to an analysis population of 1359 patients (age range 0-18). A total of 18.9% (n=257) of all investigated patients developed high-grade acute toxicity (grades 3/4). High-grade toxicity of the bone marrow was documented for 63.8% (n=201) of those patients, oral mucositis for 7.6% (n=24), and dermatitis for 7.6% (n=24). Patients with high-grade acute toxicity received concomitant chemotherapy more frequently (56%) than patients with no or lower acute toxicity (31.5%). In multivariate analyses, concomitant chemotherapy, diagnosis of Ewing sarcoma, and total radiation dose showed a statistically noticeable effect (P <=.05) on acute toxicity, whereas age, concomitant chemotherapy, Hodgkin lymphoma, Ewing sarcoma, total radiation dose, and acute toxicity influenced the time until maximal late toxicity.

    Conclusions: Generally, high-grade acute toxicity after irradiation in children and adolescence occurs in a moderate proportion of patients (18.9%). As anticipated, the probability of acute toxicity appeared to depend on the prescribed dose as well as concomitant chemotherapy. The occurrence of chronic toxicity correlates with the prior acute toxicity grade. Age seems to influence the time until maximal late toxicity but not the development of acute toxicity.

  • 197.
    Puhakka, Pia
    et al.
    Department of Applied Physics, University of Eastern Finland, Kuopio, Finland.
    Ylärinne, Janne
    Department of Applied Physics, University of Eastern Finland, Kuopio, Finland.
    Lammi, Mikko
    Department of Applied Physics, University of Eastern Finland, Kuopio, Finland.
    Saarakkala, Simo
    Department of Medical Technology, Institute of Biomedicine, University of Oulu, Oulu, Finland.
    Tiitu, Virpi
    School of Medicine, Institute of Biomedicine, Anatomy, University of Eastern Finland, Kuopio, Finland.
    Kröger, Heikki
    Department of Orthopaedics, Traumatology and Hand Surgery, Kuopio University Hospital, Kuopio, Finland.
    Tuomas, Virén
    Cancer Center, Kuopio University Hospital, Kuopio, Finland.
    Jurvelin, Jukka
    Department of Applied Physics, University of Eastern Finland, Kuopio, Finland.
    Töyräs, Juha
    Department of Applied Physics, University of Eastern Finland, Kuopio, Finland.
    Dependence of light attenuation and backscattering on collagen concentration and chondrocyte density in agarose scaffolds2014In: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 59, no 21, p. 6537-6548Article in journal (Refereed)
    Abstract [en]

    Optical coherence tomography (OCT) has been applied for high resolution imaging of articular cartilage. However, the contribution of individual structural elements of cartilage on OCT signal has not been thoroughly studied. We hypothesize that both collagen and chondrocytes, essential structural components of cartilage, act as important light scatterers and that variation in their concentrations can be detected by OCT through changes in backscattering and attenuation. To evaluate this hypothesis, we established a controlled model system using agarose scaffolds embedded with variable collagen concentrations and chondrocyte densities. Using OCT, we measured the backscattering coefficient (µb) and total attenuation coefficient (µt) in these scaffolds. Along our hypothesis, light backscattering and attenuation in agarose were dependent on collagen concentration and chondrocyte density. Significant correlations were found between µt and chondrocyte density (ρ = 0.853, p < 0.001) and between µt and collagen concentration (ρ = 0.694, p < 0.001). µb correlated significantly with chondrocyte density (ρ = 0.504, p < 0.001) but not with collagen concentration (ρ = 0.103, p = 0.422) of the scaffold. Thus, quantitation of light backscattering and, especially, attenuation could be valuable when evaluating the integrity of soft tissues, such as articular cartilage with OCT.

  • 198.
    Qvarlander, Sara
    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).
    Lundkvist, Bo
    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.
    Malm, Jan
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    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.
    Pulsatility in CSF dynamics: pathophysiology of idiopathic normal pressure hydrocephalus2013In: Journal of Neurology, Neurosurgery and Psychiatry, ISSN 0022-3050, E-ISSN 1468-330X, Vol. 84, no 7, p. 735-741Article in journal (Refereed)
    Abstract [en]

    Background: It is suggested that disturbed CSF dynamics are involved in the pathophysiology of idiopathic normal pressure hydrocephalus (INPH). The pulsatility curve describes the relationship between intracranial pressure (ICP) and the amplitude of cardiac related ICP pulsations. The position of baseline ICP on the curve provides information about the physiological state of the CSF dynamic system. The objective of the study was to investigate if shunt surgery modifies the pulsatility curve and the baseline position on the curve, and how this relates to gait improvement in INPH.

    Methods: 51 INPH patients were investigated with lumbar CSF dynamic investigations preoperatively and 5 months after shunt surgery. During the investigation, ICP was measured at baseline, and then a CSF sample was removed, resulting in pressure reduction. After this, ICP was regulated with an automated infusion protocol, with a maximum increase of 24 mm Hg above baseline. The pulsatility curve was thus determined in a wide range of ICP values. Gait improvement was defined as a gait speed increase >= 0.1 m/s.

    Results: The pulsatility curve was unaltered by shunting. Baseline ICP and amplitude were reduced (-3.0 +/- 2.9 mm Hg; -1.1 +/- 1.5 mm Hg; p < 0.05, n = 51). Amplitude reduction was larger for gait improvers (-1.2 +/- 1.6 mm Hg, n = 42) than non-improvers (-0.2 +/- 0.5 mm Hg, n = 9) (p < 0.05) although mean ICP reduction did not differ.

    Conclusions: The pulsatility curve was not modified by shunt surgery, while the baseline position was shifted along the curve. Observed differences between gait improvers and non-improvers support cardiac related ICP pulsations as a component of INPH pathophysiology.

  • 199.
    Rieckmann, Anna
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology. Umeå University, Faculty of Medicine, Umeå Centre for Functional Brain Imaging (UFBI).
    Johnson, Keith A.
    Sperling, Reisa A.
    Buckner, Randy L.
    Hedden, Trey
    Dedifferentiation of caudate functional connectivity and striatal dopamine transporter density predict memory change in normal aging2018In: Proceedings of the National Academy of Sciences, Vol. 115, no 40, p. 10160-10165Article in journal (Refereed)
    Abstract [en]

    Age-related changes in striatel function are potentially important for predicting declining memory performance over the adult life span. Here, we used fMRI to measure functional connectivity of caudate subfields with large-scale association networks and positron emission tomography to measure striatal dopamine transporter (DAT) density in 51 older adults (age 65-86 years) who received annual cognitive testing for up to 7 years (mean = 5.59, range 2-7 years). Analyses showed that cortical-caudate functional connectivity was less differentiated in older compared with younger adults (n = 63, age 18-32 years). Unlike in younger adults, the central lateral caudate was less strongly coupled with the frontal parietal control network in older adults. Older adults also showed less "decoupling" of the caudate from other networks, including areas of the default network (DN) and the hippocampal complex. Contrary to expectations, less decoupling between caudate and the DN was not associated with an age-related reduction of striatal DAT, suggesting that neurobiological changes in the cortex may drive dedifferentiation of cortical-caudate connectivity. Reduction of specificity in functional coupling between caudate and regions of the DN predicted memory decline over subsequent years at older ages. The age-related reduction in striatal DAT density also predicted memory decline, suggesting that a relation between striatal functions and memory decline in aging is multifaceted. Collectively, the study provides evidence highlighting the association of age-related differences in striatal function to memory decline in normal aging.

  • 200.
    Rottke, Dennis
    et al.
    Umeå University, Faculty of Medicine, Department of Odontology. Digital Diagnostic Center, Freiburg im Breisgau, Germany.
    Dreger, Julia
    Sawada, Kunihiko
    Honda, Kazuya
    Schulze, Dirk
    Comparison of manual and dose reduction modes of a MORITA R100 CBCT2019In: Dento-Maxillo-Facial Radiology, ISSN 0250-832X, E-ISSN 1476-542X, Vol. 48, no 2, article id 20180009Article in journal (Refereed)
    Abstract [en]

    OBJECTIVE:: To compare effective dose differences when acquiring (1) dose reduction mode and (2) manual mode in a MORITA R100 CBCT.

    METHODS:: 24 exposure protocols with different technique factors were performed in both the dose reduction mode and the manual mode in a Veraviewepocs 3D R100 cone beam CT device. 48 TLD were placed in a RANDO head phantom at 24 different sites. Effective doses were calculated according to the formalism published in the 103rd ICRP report.

    RESULTS:: Effective doses for the dose reduction mode protocols ranged from 14 to 156 µSv [mean = 57 µSv, standard deviation (SD) = 37 µSv], whereas effective doses for the manual mode protocols ranged from 22 to 267 µSv (mean = 94 µSv, SD = 65 µSv). Thus, across all protocols, the dose reduction mode leads to a drop of the effective dose by 38 % (SD = 6 %).

    CONCLUSIONS:: The estimated effective doses are significantly lower if dose reduction protocols are acquired.

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