磁振造影(Magnetic Resonance Imaging, MRI)是一種提供了非侵入式技術的實用技術，在臨床上經常被使用。法洛氏四重症的患者在經由手術矯正之後，其肺動脈血液流動仍有可能產生紊流及逆流現象。在本研究中，我們使用相位對比磁振影像來觀察患者血液流動情形，並提出一種方法來分析其肺動脈血液中的渦流現象。本文主要分為兩個部分，首先我們撰寫一程式來產生模擬的渦流，包括基本的三種樣式star、focus以及saddle。然後設計quadrant index方法來分析這些渦流樣式。第二部分我們將設計出來的參數套用到實際患者的資料上作分析，並將結果與其他參數例如旋轉強度(Vorticity)、變異係數(Coefficient of Variance, CV)以及逆流程度(Regurgitant Fraction)作比較。

結果顯示速度的CV mean值和旋轉強度的CV mean值在右肺動脈(RPA)及主肺動脈(PT)的線性關係比在左肺動脈(LPA)要來得強。我們所做出來的結果顯示Vorticity在渦流的分析上提供了一些有用的資訊，對於醫師在臨床上的診斷能夠有所幫助。

Magnetic resonance imaging (MRI) is an useful technique that provides a noninvasive method in clinical applications. For the patient of tetralogy of Fallot (TOF) after repaired, turbulence and regurgitation in blood flow may appear in pulmonary arteries. In this study, phase contrast MR imaging was applied and vortical flow patterns in the pulmonary arteries of patients after repair of TOF has been investigated. There are two major part of this study. Firstly we simulated vortical flow patterns of star, focus, and saddle which are most frequently appeared in blood flow. Quadrant index has been proposed for pattern analysis. In the second part we applied these parameters to in vivo data of repaired TOF patients, and compared with other parameters such as vorticity, coefficient of variance (CV), and regurgitant fraction (RF).

Our result shows that the linear correlation between the mean of CV of velocity and mean of CV of vorticity in right pulmonary artery (RPA) as well as pulmonary trunk (PT) is larger than that in left pulmonary artery (LPA). This study shows that vorticity may provide some useful information of flow patterns and therefore helps doctors in clinical diagnosis

Illustrations 5
Tables 6
Chapter 1 Introduction 7
1.1 Background and literatures 7
1.1.1 Magnetic Resonance Imaging 7
1.1.2 Phase Contrast Imaging 7
1.1.3 Tetralogy of Fallot (TOF) 9
1.1.4 Vortical Flow Patterns 10
1.2 Motivation 10
1.3 Outline 10
Chapter 2 Materials and Data Pre-processing 14
2.1 Phase Contrast MR Images 14
2.2 Data pre-processing 15
2.2.1 Region of interest (ROI) 15
2.2.2 Vector projection 15
Chapter 3 Simulation of the Vortical Flow Patterns 18
3.1 Vector fields 18
3.2 Generating flow patterns 18
3.3 Quadrant index 18
3.4 Global variance 19
3.5 Simulation results 20
Chapter 4 In vivo Data of Repaired TOF Patients 24
4.1 Vorticity 24
4.2 Results 25
4.2.1 Mean CV of velocity and Mean CV of vorticity 25
4.2.2 Maximum of CV of Velocity and Maximum of CV of Vorticity 27
4.2.3 Regurgitant Fraction and CV of Vorticity 28
4.3.3 Quadrant index 30
Chapter 5 Discussions and Conclusions 47
5.1 Discussions 47
5.2 Conclusions 47
References 50

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