法洛氏四重症在經過肺動脈修復手術過後肺動脈倒流是常見的現象。根據臨床資料,可以得知左肺動脈的倒流率通常都比右肺動脈來的高,其可能與肺動脈中血液的流動型態有關係。因此,瞭解肺動脈中的血液動力學有助於理解其原因。本研究主要利用磁振造影影像重建成三維肺動脈模型,並且利用數值方法模擬於法洛氏四重症修復手術後肺動脈的血液流動變化,所使用的肺動脈模型外型由一位健康的人和三位經過法洛氏四重症修復手術後病人之磁振造影影像所獲得。為了探索肺動脈倒流的影響,考慮一個健康和三個經過法洛氏四重症修復手術後的肺動脈。
依據數值模擬結果,血流會受到分歧角度以及肺動脈幾何的影響,倒流現象會先發生於法洛氏四重症修復手術後的左肺動脈,由於左肺動脈與主肺動脈的夾角較小。在心臟收縮加速期,迴流區會發生於左肺動脈其會阻礙血液流至左肺,另外,主肺動脈腫大經常發生於法洛氏四重症修復手術之後,在一個心跳的舒張期間發現一些強烈的渦旋會在其腫大的區域產生。當心臟收縮或舒張結束時,會發生混亂的流場型態,由於主肺動脈的血流方向發生改變,在肺動脈倒流期間可以發現主肺動脈腫大區導致異常的血流型態。而在健康的肺動脈中並沒有發生這些流場型態。我們也對壓力的分布進行分析,激烈的壓力變化發生於主肺動脈腫大處。將數值模擬的主肺動脈、左肺動脈和右肺動脈的倒流與相位對比磁振造影量測的資料做比較,在數值結果和量測資料之間具有良好的一致性。

Pulmonary regurgitation (PR) is a common phenomenon in pulmonary arteries in patients after repair of tetralogy of Fallot (TOF). The regurgitation fraction of left pulmonary artery (LPA) is usually greater than right pulmonary artery (RPA) according to clinic data. It may be related to blood flow in pulmonary arteries. Therefore, understanding hemodynamics in pulmonary arteries helps to comprehend the reason. The aim of this study is to use 3-D reconstructed pulmonary artery models from magnetic resonance imaging (MRI) and to use numerical approaches for simulation of flow variations in pulmonary arteries after repair of TOF. The periphery of pulmonary artery is obtained from MRI of one healthy person and three patients after repair of TOF. To explore the effect of PR, one healthy and three pulmonary arteries after repair of TOF are considered.
From the numerical results, the blood flow is influence by the bifurcation anglesand geometry of pulmonary artery. The regurgitation happens first in LPA after repair of TOF due to the small angle between LPA and main pulmonary artery (MPA). The recirculation region which obstructs forward blood flow to the left lung is found in LPA during acceleration of systole. In addition, the dilation ofMPA usually appears after repair of TOF. Strong vortices are found in the dilation area of MPA during diastole of a cardiac cycle. The complex blood flow patterns occur in end of systole and diastole because the directions of blood flow in MPA changes. It is found that the dilation causes abnormal flow distribution in MPA during regurgitation period in a cardiac cycle. The healthy person does not have those flow patterns. We also analysis the pressure distribution, the extreme pressure variations is in dilation area of MPA. Numerical data including regurgitation in MPA, LPA and RPA are compared with phase contrast MR measured data. Good agreements are found between numerical results and measured data.

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