A problem solving environment for image-based computational hemodynamics

We introduce a complete problem solving environment designed for pulsatile flows in 3D complex geometries, especially arteries. Three-dimensional images from arteries, obtained from e.g. Magnetic Resonance Imaging, are segmented to obtain a geometrical description of the arteries of interest. This segmented artery is prepared for blood flow simulations in a 3D editing tool, allowing to define in- and outlets, to filter and crop part of the artery, to add certain structures ( e.g. a by-pass, or stents ), and to generate computational meshes as input to the blood flow simulators. Using dedicated fluid flow solvers the time dependent blood flow in the artery during one systole is computed. The resulting flow, pressure and shear stress fields are then analyzed using a number of visualization techniques. The whole environment can be operated from a desktop virtual reality system, and is embedded in a Grid computing environment

Improved viscosity modeling in patients with type 2 diabetes mellitus by accounting for enhanced red blood cell aggregation tendency

Aims: Distorted wall shear stress (WSS) in patients with type 2 diabetes mellitus (T2DM) may be partly explained by an altered red blood cell aggregation tendency (RAT) on viscosity at low shear rate (SR). The present study evaluates viscosity modeling by implementation of hematocrit and RAT in patients with and without T2DM (non-T2DM). Methods: A Couette viscometer and LORCA aggregometer provided viscosity and RAT on 6 shear rates in 55 patients (46-78 yrs, 66% male, T2DM: n = 28), following informed consent. Using a K-fold cross-validation, two linear mixed models predicted by SR and Hct and by SR, Hct and RAT were compared. Results: In non-T2DM modeling was improved in relatively low RATs (48%, p = 1.0 x 10(-11)) and became worse in relatively high RATs (-18%, p = 0.019). In T2DM the opposite was observed, as modeling became worse in relatively low RATs (-16%, p = 0.001) but was improved in relatively high RATs (22%, p = 0.022). Conclusions: In addition to confirming previous research, major differences in modeling improvement between T2DM and non-T2DM were found. Especially patients with T2DM, a high RAT and often high viscosity at low SR benefit from a more accurate viscosity modeling. Further studies should evaluate how these findings affect WSS in these patient

Guideline treatment results in regression of atherosclerosis in type 2 diabetes mellitus

Background: Efficacy of guideline cardiovascular disease prevention regimens may differ between patients with or without type II diabetes mellitus. We therefore compared change in carotid artery wall dimensions in type II diabetes mellitus and non-type II diabetes mellitus patients with a history of a major cardiovascular disease event, using magnetic resonance imaging. Methods: Thirty type II diabetes mellitus patients and 29 age- and sex-matched non-diabetes mellitus patients with a history of stroke or myocardial infarction and a carotid artery stenosis (15%70%) were included. In all patients, treatment was according to cardiovascular risk management guidelines. At baseline and follow-up, carotid artery vessel wall dimensions were measured using 1.5 T magnetic resonance imaging. Results: After 2 years of follow-up, total wall volume of the carotid artery in type II diabetes mellitus patients decreased by 9.6% (ρ = 0.016). In contrast, stabilization rather than regression of carotid artery wall dimensions was observed in nondiabetes mellitus patients over a 2-year period. Body mass index was identified as a predictor of total wall volume decrease. Conclusions: Guideline treatment arrests atherogenesis in non-diabetes mellitus patients and even decreases vessel wall dimensions in type II diabetes mellitus patients. Baseline body mass index predicts cardiovascular disease prevention efficacy expressed as decrease in total wall volume. These data emphasize the importance of optimal cardiovascularprevention, particularly in diabetes patients with a high body mass index

Reproducibility of wall shear stress assessment with the paraboloid method in the internal carotid artery with velocity encoded MRI in healthy young individuals

PURPOSE: To verify whether wall shear stress (WSS) can be assessed in a reproducible manner using automatic model-based segmentation of phase-contrast MR images by determination of flow volume and maximum flow velocity (Vmax) in cross-sections of these vessels. MATERIALS AND METHODS: The approach is based on fitting a 3D paraboloid to the actual velocity profiles and on determining Vmax. WSS was measured in the internal carotid arteries of two groups of healthy young volunteers. The reproducibility of rescanning and repositioning was studied in the first group. In the second group a 1-week and a 1-month interval was investigated. Reproducibility was calculated by the intraclass correlation (ICC). RESULTS: The flow volume, Vmax, and WSS averaged over the cardiac cycle were found to be 287.8 +/- 29.7 mL/min, 37.0 +/- 4.6 cm/s, and 1.13 +/- 0.16 Pa, respectively. The diastolic WSS varied between 1.00 +/- 0.21 Pa without averaging to 0.88 +/- 0.16 Pa with temporal and spatial averaging. Systolic WSS was 1.67 +/- 0.33 Pa without averaging and 1.67 +/- 0.25 Pa with averaging. ICC varied between 0.58 and 0.87 without averaging and between 0.75 and 0.90 with averaging for WSS. CONCLUSION: WSS in MR images of the internal carotid artery can be assessed semiautomatically with good to excellent reproducibility without inter- or intraobserver variability using model-based postprocessin