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Fredriksson A.G.,Center for Medical Image Science and Visualization | Zajac J.,Center for Medical Image Science and Visualization | Eriksson J.,Center for Medical Image Science and Visualization | Dyverfeldt P.,Center for Medical Image Science and Visualization | And 6 more authors.
American Journal of Physiology - Heart and Circulatory Physiology | Year: 2011

Right ventricular (RV) function is a powerful prognostic indicator in many forms of heart disease, but its assessment remains challenging and inexact. RV dysfunction may alter the normal patterns of RV blood flow, but those patterns have been incompletely characterized. We hypothesized that, based on anatomic differences, the proportions and energetics of RV flow components would differ from those identified in the left ventricle (LV) and that the portion of the RV inflow passing directly to outflow (Direct Flow) would be prepared for effective systolic ejection as a result of preserved kinetic energy (KE) compared with other RV flow components. Three-dimensional, time-resolved phase-contrast velocity, and balanced steady-state free precession morphological data were acquired in 10 healthy subjects using MRI. A previously validated method was used to separate the RV and LV end-diastolic volumes into four flow components and measure their volume and KE over the cardiac cycle. The RV Direct Flow: 1) followed a smoothly curving route that did not extend into the apical region of the ventricle; 2) had a larger volume and possessed a larger presystolic KE (0.4 ± 0.3 mJ) than the other flow components (P < 0.001 and P < 0.01, respectively); and 3) represented a larger part of the end-diastolic blood volume compared with the LV Direct Flow (P < 0.01). These findings suggest that diastolic flow patterns distinct to the normal RV create favorable conditions for ensuing systolic ejection of the Direct Flow component. These flow specific aspects of RV diastolic-systolic coupling provide novel perspectives on RV physiology and may add to the understanding of RV pathophysiology. © 2011 the American Physiological Society.

Persson P.,Biomedical Center | Fasching A.,Biomedical Center | Teerlink T.,VU University Amsterdam | Hansell P.,Biomedical Center | And 3 more authors.
Hypertension | Year: 2014

Diabetes mellitus-induced oxidative stress causes increased renal oxygen consumption and intrarenal tissue hypoxia. Nitric oxide is an important determinant of renal oxygen consumption and electrolyte transport efficiency. The present study investigates whether L-arginine or L-citrulline to promote nitric oxide production prevents the diabetes mellitus-induced kidney dysfunction. Glomerular filtration rate, renal blood flow, in vivo oxygen consumption, tissue oxygen tension, and proteinuria were investigated in control and streptozotocin-diabetic rats with and without chronic L-arginine or L-citrulline treatment for 3 weeks. Untreated and L-arginine-treated diabetic rats displayed increased glomerular filtration rate (2600±162 versus 1599±127 and 2290±171 versus 1739±138 μL/min per kidney), whereas L-citrulline prevented the increase (1227±126 versus 1375±88 μL/min per kidney). Filtration fraction was increased in untreated diabetic rats because of the increase in glomerular filtration rate but not in L-arginine-or L-citrulline-treated diabetic rats. Urinary protein excretion was increased in untreated and L-arginine-treated diabetic rats (142±25 versus 75±7 and 128±7 versus 89±7 μg/min per kidney) but not in diabetic rats administered L-citrulline (67±7 versus 61±5 μg/min per kidney). The diabetes mellitus-induced tissue hypoxia, because of elevated oxygen consumption, was unaltered by any of the treatments. L-citrulline administered to diabetic rats increases plasma L-arginine concentration, which prevents the diabetes mellitus-induced glomerular hyperfiltration, filtration fraction, and proteinuria, possibly by a vascular effect. © 2014 American Heart Association, Inc.

Borgen L.,Drammen and Buskerud University College | Kalra M.K.,Harvard University | Laerum F.,Akershus University Hospital | Hachette I.W.,ContextVision | And 5 more authors.
Acta Radiologica | Year: 2012

Background: Abdominal computed tomography (CT) is a frequently performed imaging procedure, resulting in considerable radiation doses to the patient population. Postprocessing filters are one of several dose reduction measures that might help to reduce radiation doses without loss of image quality. Purpose: To assess and compare the effect of two- and three-dimensional (2D, 3D) non-linear adaptive filters on reduced dose abdominal CT images. Material and Methods: Two baseline abdominal CT image series with a volume computer tomography dose index (CTDI vol) of 12 mGy and 6 mGy were acquired for 12 patients. Reduced dose images were postprocessed with 2D and 3D filters. Six radiologists performed blinded randomized, side-by-side image quality assessments. Objective noise was measured. Data were analyzed using visual grading regression and mixed linear models. Results: All image quality criteria were rated as superior for 3D filtered images compared to reduced dose baseline and 2D filtered images (P < 0.01). Standard dose images had better image quality than reduced dose 3D filtered images (P < 0.01), but similar image noise. For patients with body mass index (BMI) < 30 kg/m 2 however, 3D filtered images were rated significantly better than normal dose images for two image criteria (P < 0.05), while no significant difference was found for the remaining three image criteria (P > 0.05). There were no significant variations of objective noise between standard dose and 2D or 3D filtered images. Conclusion: The quality of 3D filtered reduced dose abdominal CT images is superior compared to reduced dose unfiltered and 2D filtered images. For patients with BMI < 30 kg/m 2, 3D filtered images are comparable to standard dose images.

Knutsson H.,Linköping University | Knutsson H.,Center for Medical Image Science and Visualization | Westin C.-F.,Linköping University | Westin C.-F.,Harvard University | And 2 more authors.
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2011

Estimation of local spatial structure has a long history and numerous analysis tools have been developed. A concept that is widely recognized as fundamental in the analysis is the structure tensor. However, precisely what it is taken to mean varies within the research community. We present a new method for structure tensor estimation which is a generalization of many of it's predecessors. The method uses filter sets having Fourier directional responses being monomials of the normalized frequency vector, one odd order sub-set and one even order sub-set. It is shown that such filter sets allow for a particularly simple way of attaining phase invariant, positive semi-definite, local structure tensor estimates. We continue to compare a number of known structure tensor algorithms by formulating them in monomial filter set terms. In conclusion we show how higher order tensors can be estimated using a generalization of the same simple formulation. © 2011 Springer-Verlag.

Lundin M.,Örebro University | Liden M.,Örebro University | Magnuson A.,Örebro University | Mohammed A.A.,Linköping University | And 3 more authors.
Acta Radiologica | Year: 2012

Background: Dual-energy computed tomography (DECT) has been shown to be useful for subtracting bone or calcium in CT angiography and gives an opportunity to produce a virtual non-contrast-enhanced (VNC) image from a series where contrast agents have been given intravenously. High noise levels and low resolution have previously limited the diagnostic value of the VNC images created with the first generation of DECT. With the recent introduction of a second generation of DECT, there is a possibility of obtaining VNC images with better image quality at hopefully lower radiation dose compared to the previous generation. Purpose: To compare the image quality of the single-energy series to a VNC series obtained with a two generations of DECT scanners. CT of the urinary tract was used as a model. Material and Methods: Thirty patients referred for evaluation of hematuria were examined with an older system (Somatom Definition) and another 30 patients with a new generation (Somatom Definition Flash). One single-energy series was obtained before and one dual-energy series after administration of intravenous contrast media. We created a VNC series from the contrast-enhanced images. Images were assessed concerning image quality with a visual grading scale evaluation of the VNC series with the single-energy series as gold standard. Results: The image quality of the VNC images was rated inferior to the single-energy variant for both scanners, OR 11.5-67.3 for the Definition and OR 2.1-2.8 for the Definition Flash. Visual noise and overall quality were regarded as better with Flash than Definition. Conclusion: Image quality of VNC images obtained with the new generation of DECT is still slightly inferior compared to native images. However, the difference is smaller with the new compared to the older system.

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