数値流体力学解析による頸動脈分岐部における心位相に対応した壁面剪断応力評価

摘要

Purpose: Detailed strategy for regional hemodynamics is significant for knowledge of plaque development on vascular diseases such as atherosclerosis. The aim of this study was to derive relation between atherosclerosis and hemodynamics at human carotid bifurcation by the use of computational fluid dynamics (CFD), and to provide more accurate hemodynamic information. Methods: Blood velocity datasets at common carotid artery were obtained by phase-contrast cine magnetic resonance imaging (PC cine MRI). Carotid bifurcation model was computed for systolic, mid-diastolic, and end-diastolic phase. Comparison of wall shear stress (WSS) was performed for each cardiac phase. Results: PC cine MRI provided velocity measurement for common carotid artery with various cardiac phases. The blood velocity had acute variation from 0.21 m/s to 1.07 m/s at systolic phase. The variation of WSS during cardiac phase was presented at carotid bifurcation model. High shear stress area was observed at dividing wall for all cardiac phases. The systole-diastole WSS ratio was 10.15 at internal carotid side of bifurcation. And low shear stress (＜ 0.5 Pa) was observed at internal carotid side of bifurcation. Conclusion: Bifurcation area represented low shear stress and changed significantly WSS. The specific area with significant change in shear stress and low shear stress had good agreement with predilection sites of atherosclerosis. The result suggested that hemodynamics was related to atherosclerosis, and CFD analysis with various cardiac phases that were provided by PC cine MRI was allowed to determine an accurate analysis condition. This led to the representation of hemodynamics in vivo.%動脈硬化性疾患は，血液が血管を流れることによって生じる血行力学的作用と関連があることが以前より知られている.血流によって生じる壁面剪断応力(wall shear stress: WSS)が血管壁に与える影響についての報告は，1980年代より多く散見されている.近年，血流などの数値流体力学解析(computational fluid dynamics:CFD)はコンピュータハードウェアの進歩によって，より正確なシミュレーションを行うことが可能になっている.更に体内の血流は造影剤や超音波，磁場を用いて画像化され，医療現場において血流を観察する一般的な手法として普及している.こういった背景を元に，医用画像と数値流体力学シミュレーションを融合した血流解析が行われるようになってきた.