Computational flow modeling of the left ventricle based on in vivo MRI data: initial experience.

A combined computational fluid dynamics (CFD) and magnetic resonance imaging (MRI) methodology has been developed to simulate blood flow in heart chambers, with specific application in the present study to the human left ventricle. The proposed framework employs MRI scans of a human heart to obtain geometric data, which are then used for the CFD simulations. These latter are accomplished by geometrical modeling of the ventricle using time-resolved anatomical slices of the ventricular geometry and imposition of inflow/outflow conditions at orifices notionally representing the mitral and aortic valves. The predicted flow structure evolution and physiologically relevant flow characteristics were examined and compared to existing information. The CFD model convincingly captures the three-dimensional contraction and expansion phases of endocardial motion in the left ventricle, allowing simulation of dominant flow features, such as the vortices and swirling structures. These results were qualitatively consistent with previous physiological and clinical experiments on in vivo ventricular chambers, but the accuracy of the simulated velocities was limited largely by the anatomical shortcomings in the valve region. The study also indicated areas in which the methodology requires improvement and extension.

Evaluation of patients undergoing lung volume reduction surgery: ancillary information available from computed tomography.

AIM: A number of imaging techniques have been used for the pre-operative assessment of patients for lung volume reduction surgery (LVRS). We evaluated whether data currently acquired from perfusion scintigrams and cine MR of the diaphragm are obtainable from high resolution CT (HRCT) of the thorax. MATERIALS AND METHODS: Thirty patients taking part in a randomized controlled trial of LVRS against maximal medical therapy were evaluated. HRCT examinations (n= 30) were scored for (i) the extent and distribution of emphysema; (ii) the extent of normal pulmonary vasculature; and (iii) diaphragmatic contour, apparent defects and herniation. On scintigraphy, (n= 28), perfusion of the lower thirds of both lungs, as a proportion of total lung perfusion (LZ/T(PERF)), was expressed as a percentage of predicted values (derived from 10 normal control subjects). On cine MR (n= 25) hemidiaphragmatic excursion and coordination were recorded. RESULTS: Extensive emphysema was present on HRCT (60% +/- 13.2%). There was strong correlation between the extent of normal pulmonary vasculature on HRCT and on perfusion scanning (r(s)= 0.85, P< 0.00005). Hemidiaphragmatic incoordination on MR was weakly associated with hemidiaphragmatic eventration on HRCT (P= 0.04). CONCLUSION: The strong correlation between lung perfusion assessed by HRCT and lung perfusion on scintigraphy suggests that perfusion scintigraphy is superfluous in the pre-operative evaluation of patients with emphysema for LVRS.