Dynamic three-dimensional blood vessel modeling for analyzing 4 dimensional phase contrast MRI of Stanford B type aortic dissection / 第二军医大学学报

ABSTRACT

Objective: To apply dynamic three-dimensional blood vessel modeling for analyzing the blood flow parameters obtained by 4 dimensional phase contrast MRI (4D PC-MRI) of Stanford B type aortċc dissection, so as to demonstrate the blood flow characteristics of both healthy controls and patients with Stanford B type aortic dissection. Methods: Dynamic 3D models of blood vessel were captured from 3D PC-MRI with temporal resolution. A reference vascular cross-sectional plane was defined, and the displacement contour information at the same plane was all used to determine the pulsatility of the target vascular cross-sectional planes at multiple time points. The pulsatility parameters of target vascular cross-sectional planes were obtained by temporal tracking. The hemodynamic differences between healthy adults (n=19) and patients (n=8) with Stanford B type aortic dissection were analyzed by comparing 4D PC-MRI data of the two groups. Results: Qualitative blood flow visualization showed laminar flow in the aorta of healthy volunteers, without turbulences or vortex formation, with slight helical flow pattern found in the ascending aorta; there were little changes in the wall shear stress in the entire thoracic aorta. The blood flow in the false lumen was multidirectional and complex, with a high incidence of reverse flow, and the true lumens were dominated by aortic flow direction. The peak velocity of blood flow arrived earlier in the false lumen, not in the true lumen. The stroke volume was greater in the true lumen (media [M]54.3 mL, interquartile range [IQR] 43. 2-64. 8 mL) compared with the false one (M 31.6 mL, IQR 19. 8-47. 6 mL, P < 0.01). The majority of the flow in the true lumen was forward flow (M 91. 4%,IQR 90. 0%-94.2%), whereas the false lumen had a high proportion of backward flow (M 40.3%, IQR 23. 2% 53.3%). The average velocity of blood flow in the false lumen (M 7.1 cm/s, IQR 4. 9-9. 8 cm/s) was lower than that in the true lumen (M 18.0 cm/s, IQR 13.9-20. 6 cm/s, P<0.01). The maximum velocity occurred earlier in the false lumen during the cardiac cycle 166.0 ms after the R-wave (IQR 132. 8-210. 0 ms) compared with that in the true lumen (M 215. 0 ms, IQR 196.3-249.0 ms,P<0. 01). Helical flow mainly occurred at early-systole stage, at 158 ms (IQR 145-249 ms) after the R-wave, and lasted for 310 ms (IQR 217-537 ms), with the maximum rotation being 820° per cardiac cycle. Conclusion: Dynamic 3D modeling method can effectively analyze the flow parameters obtained from 4D PC-MRI and can provide qualitative blood flow information. Flow direction, time to peak velocity, and development and changes of helical flow may be involved in the pathology of aortic dissection.