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Träfflista för sökning "AMNE:(MEDICAL AND HEALTH SCIENCES Clinical Medicine Radiology, Nuclear Medicine and Medical Imaging) "

Sökning: AMNE:(MEDICAL AND HEALTH SCIENCES Clinical Medicine Radiology, Nuclear Medicine and Medical Imaging)

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  • Petersson, Jesper, 1974- (författare)
  • Medicine At A Distance In Sweden: Spatiotemporal Matters In Accomplishing Working Telemedicine
  • 2011
  • Ingår i: Science Studies. - 0786-3012. ; 24:2, s. 43-62
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper examines the accomplishment of making technology work, using the discourse around telemedicine in Swedish healthcare during 1994-2003. The paper will compare four projects launched in the mid-1990s and policymakers’ visions of healthcare through telemedicine. I will employ a sociotechnical approach developed within Actor-Network Theory that understands functioning technology not as something intrinsic but as an outcome of an ongoing process of negotiations. In the paper, I will extend the sociotechnical approach of what constitutes working technology to include spatiotemporal matters. I will also approach the closely related issue of space that has become a concern of Actor-Network Theory scholars interested in the accomplishment and continued workings of technology as it travels. In this discussion, an emphasis on fixed relations (network space) has been challenged by investigations into changing relations (fluid space). This paper suggests that in order to travel well, technology must be both fixed and fluid.⁰
  • Forssell-Aronsson, Eva, 1961-, et al. (författare)
  • 2017
  • Ingår i: Radiation Protection Dosimetry. - 0144-8420. ; 173:1-3, s. 16-20
  • Tidskriftsartikel (refereegranskat)abstract
    • Daily rhythmic changes are found in cellular events in cell cycle, DNA repair, apoptosis and angiogenesis in both normal and tumour tissue, as well as in enzymatic activity and drug metabolism. In this paper, we hypothesize that circadian rhythms need to be considered in radiation protection and optimization in personalized medicine, especially for paediatric care. The sensitivity of the eye lens to ionizing radiation makes the case for limiting damage to the lens epithelium by planning medical radio-imaging procedures for the afternoon, rather than the morning. Equally, the tumour and normal tissue response to radiotherapy is also subject to diurnal variation enabling optimization of time of treatment.
  • Almén, Anja, et al. (författare)
  • Challenges assessing radiation risk in image-guided treatments-implications on optimisation of radiological protection
  • 2018
  • Ingår i: Journal of Radiological Protection. - 0952-4746. ; 38:3, s. 1064-1076
  • Tidskriftsartikel (refereegranskat)abstract
    • The present work explores challenges when assessing organ dose and effective dose concerning image-guided treatments. During these treatments considerable x-ray imaging is employed using technically advanced angiographic x-ray equipment. Thus, the radiation dose to organs and the related radiation risk are relatively difficult to assess. This has implications on the optimisation process, in which assessing radiation dose is one important part.
 In this study, endovascular aortic repair treatments (EVAR) were investigated. Organ dose and effective dose were assessed using Monte Carlo calculations together with detailed specification of the exposure situation and patient size. The resulting normalised organ dose and effective dose with respect to kerma-area product for patient sizes and radiation qualities representative for the patient group were evaluated. The variability and uncertainty were investigated and its possible impact on optimisation of radiation protection was discussed. 
 Exposure parameters, source to detector distances etc. varied between treatments and also varied between image acquisitions during one treatment. Thus the derived normalised organ dose and effective dose exhibited a large range of values depending greatly on used exposure parameters and patient configuration. The derived normalised values for effective dose varied approximately between 0.05 and 0.30 mSv per Gy·cm2 when taking patient sizes and exposure parameters into consideration, the values for organ doses exhibited even larger variation. The study shows a possible systematic error for derived organ doses and effective dose up to a factor of 7 if detailed exposure or patient characteristics are not known and/or not taken into consideration. The intra-treatment variability was also substantial and the normalised dose values varied up to a factor of 2 between image acquisitions during one treatment. 
 The study shows that the use of conversion factors that are not adapted to the clinic can cause the radiation dose to be exaggerated or underestimated considerably. A conclusion from the present study is that the systematic error could be large and should be estimated together with random errors. A large uncertainty makes it difficult to detect true differences in radiation dose between methods and technology - a prerequisite for optimising radiation protection for image-guided treatments.&#13.
  • Chakarova, Roumiana, et al. (författare)
  • A Monte Carlo evaluation of beam characteristics for total body irradiation at extended treatment distances
  • 2014
  • Ingår i: Journal of Applied Clinical Medical Physics. - 1526-9914. ; 15:3, s. 182-189
  • Tidskriftsartikel (refereegranskat)abstract
    • The aim is to study beam characteristics at large distances when focusing on the electron component. In particular, to investigate the utility of spoilers with various thicknesses as an electron source, as well as the effect of different spoiler-to-surface distances (STSD) on the beam characteristics and, consequently, on the dose in the superficial region. A MC model of a 15 MV Varian accelerator, validated earlier by experimental data at isocenter and extended distances used in large-field total body irradiation, is applied to evaluate beam characteristics at distances larger than 400 cm. Calculations are carried out using BEAMnrc/DOSXYZnrc code packages and phase space data are analyzed by the beam data processor BEAMdp. The electron component of the beam is analyzed at isocenter and extended distances, with and without spoilers as beam modifiers, assuming vacuum or air surrounding the accelerator head. Spoiler thickness of 1.6 cm is found to be optimal compared to thicknesses of 0.8 cm and 2.4 cm. The STSD variations should be taken into account when treating patients, in particular when the treatment protocols are based on a fixed distance to the patient central sagittal plane, and also, in order to maintain high dose in the superficial region.
  • Khoshnood, Ardavan (författare)
  • Prehospital Diagnosis and Oxygen Treatment in ST Elevation Myocardial Infarction
  • 2017
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • IntroductionPaper I: An Artificial Neural Network (ANN) was constructed to identify ST Elevation Myocardial Infarction (STEMI) and predict the need for Percutaneous Coronary Intervention (PCI). Paper II, III and IV: Studies suggest that O2 therapy may be harmful in STEMI patients. We therefore conducted the SOCCER study to evaluate the effects of O2 therapy in STEMI patients.MethodsPaper I: 560 ambulance ECGs sent to the Cardiac Care Unit (CCU), was together with the CCU physicians interpretation and decision of conducting an acute PCI or not collected, and compared with the interpretation and PCI decision of the ANN. Paper II, III, IV: Normoxic (≥94%) STEMI patients accepted for acute PCI were in the ambulance randomized to standard care with 10 L/min O2 or room air. A subset of the patients underwent echocardiography for determination of the Left Ventricular Ejection Fraction (LVEF) and the Wall Motion Score Index (WMSI). All patients had a Cardiac Magnetic Resonance Imaging (CMRI) to evaluate Myocardial area at Risk (MaR), Infarct Size (IS) and Myocardial Salvage Index (MSI).ResultsPaper I: The area under the ANN’s receiver operating characteristics curve for STEMI detection as well as predicting the need of acute PCI were very good.Paper II, III, IV: No significant differences could be shown in discussing MaR, MSI or IS between the O2 group (n=46) and the air group (n=49). Neither could any differences be shown for LVEF and WMSI at the index visit as well after six months between the O2 group (n=46) and the air group (n=41)ConclusionsPaper I: The results indicate that the number of ECGs sent to the CCU could be reduced with 2/3 as the ANN would safely identify ECGs not being STEMI.Paper II, III, IV: The results suggest that it is safe to withhold O2 therapy in normoxic, stable STEMI patients.
  • Norrman, Eva, et al. (författare)
  • Optimization of image process parameters through factorial experiments using a flat panel detector
  • 2007
  • Ingår i: Physics in Medicine and Biology. - Bristol : IOP publishing. - 0031-9155 .- 1361-6560. ; 52:17, s. 5263-5276
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>In the optimization process of lumbar spine examinations, factorial experiments were performed addressing the question of whether the effective dose can be reduced and the image quality maintained by adjusting the image processing parameters. A 2(k)-factorial design was used which is a systematic and effective method of investigating the influence of many parameters on a result variable. Radiographic images of a Contrast Detail phantom were exposed using the default settings of the process parameters for lumbar spine examinations. The image was processed using different settings of the process parameters. The parameters studied were ROI density, gamma, detail contrast enhancement (DCE), noise compensation, unsharp masking and unsharp masking kernel (UMK). The images were computer analysed and an image quality figure (IQF) was calculated and used as a measurement of the image quality. The parameters with the largest influence on image quality were noise compensation, unsharp masking, unsharp masking kernel and detail contrast enhancement. There was an interaction between unsharp masking and kernel indicating that increasing the unsharp masking improved the image quality when combined with a large kernel size. Combined with a small kernel size however the unsharp masking had a deteriorating effect. Performing a factorial experiment gave an overview of how the image quality was influenced by image processing. By adjusting the level of noise compensation, unsharp masking and kernel, the IQF was improved to a 30% lower effective dose.</p>
  • Ge, Chenjie, et al. (författare)
  • Enlarged Training Dataset by Pairwise GANs for Molecular-Based Brain Tumor Classification
  • 2020
  • Ingår i: IEEE Access. - 2169-3536. ; 8:1, s. 22560-22570
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper addresses issues of brain tumor subtype classification using Magnetic Resonance Images (MRIs) from different scanner modalities like T1 weighted, T1 weighted with contrast-enhanced, T2 weighted and FLAIR images. Currently most available glioma datasets are relatively moderate in size, and often accompanied with incomplete MRIs in different modalities. To tackle the commonly encountered problems of insufficiently large brain tumor datasets and incomplete modality of image for deep learning, we propose to add augmented brain MR images to enlarge the training dataset by employing a pairwise Generative Adversarial Network (GAN) model. The pairwise GAN is able to generate synthetic MRIs across different modalities. To achieve the patient-level diagnostic result, we propose a post-processing strategy to combine the slice-level glioma subtype classification results by majority voting. A two-stage course-to-fine training strategy is proposed to learn the glioma feature using GAN-augmented MRIs followed by real MRIs. To evaluate the effectiveness of the proposed scheme, experiments have been conducted on a brain tumor dataset for classifying glioma molecular subtypes: isocitrate dehydrogenase 1 (IDH1) mutation and IDH1 wild-type. Our results on the dataset have shown good performance (with test accuracy 88.82%). Comparisons with several state-of-the-art methods are also included.
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