臺灣博碩士論文加值系統

本論文的研究目的是探討血液流入效應是否會影響血氧濃度相關對比之功能性磁振造影訊號改變的時間反應於典型的事件相關模式。流入效應的貢獻在血流動力反應對重覆之短視覺刺激重複單次試驗於梯度回音面迴訊造影波序中藉由改變偏折角從300 到 900且重複時間為1 秒的方式被評估。 對於每個偏折角(Flip angle)的實驗 (300、 600 及 900)， 執行30 個試驗於1.5T 和3T 的磁振造影掃描儀。比較血氧濃度相關對比百分比，發現到顯著的血液流入效應在3T的實驗同時有統計上顯著差異。使用偏折角900血氧濃度相關可以看到潛沉時間顯著的比使用偏折角900 晚。落下時間於偏折角300的反應比偏折角900的還要早，但沒有統計上的差異。使用像素間分析，潛沉時間變異性決定於視覺活化區的不同對比雜訊比水平。在相同對比雜訊比水平下，使用偏折角900血氧濃度相關可以觀察顯著較大的潛沉時間變異性的比起使用偏折角300 。本篇論文建議如下:血液流入效應貢獻對血氧濃度相關反應會造成較短的潛沉時間並且增加潛沉時間變異性在所觀察的功能性腦區內。

The purpose of this study is to determine whether blood inflow impacts the temporal behavior of BOLD-contrast fMRI signal changes in a typical event-related paradigm. The inflow contributions in the hemodynamic response to repeated single-trials of short visual stimulation were assessed with a gradient-echo EPI sequence by altering the flip angle (FA) from 300 to 900 at a repetition time of 1 s. For each FA condition (300, 600 and 900), 30 trials were performed on both 1.5 T and 3 T MRI scanners. Comparing the percent BOLD contrast, prominent inflow effects were found at 3 T with marginal significance between the 900- and 300-FA conditions (0.73 ± 0.15 vs. 0.67 ± 0.12 %, p = 0.028). BOLD responses with FA = 300 exhibited latencies significantly slower than those with FA = 900 (3.69 ± 0.39 s vs. 3.37 ± 0.28 s, p = 0.001). The falling time of the 300-FA responses was earlier but not statistically different from that of the 900-FA (8.17 ± 1.04 s vs. 8.03± 1.15 s, p = 0.3). Using a voxelwise analysis, the latency variations of the activated visual areas were determined at several contrast-to-noise ratio (CNR) levels (controlled by averaging different numbers of randomly selected trials). The 900-FA responses demonstrated greater latency variations than the 300-FA ones when comparing at the same CNR levels. This study suggests that inflow effects contribute to the BOLD response, resulting in shorter latency and increased variability within a functional region.

國家圖書館授權書 iii
長庚大學圖書館授權書 iv
致謝 v
摘要 vi
ABSTRACT vii
TABLE OF CONTENTS viii
LIST OF FIGURES x
Chapter I INTRODUCTION - 1 -
1.1 Background - 1 -
1.2 Purpose of the study - 3 -
Chapter II MATERIALS AND METHODS - 4 -
2.1 Subjects - 4 -
2.2 Experimental design - 4 -
2.3 MRI acquisition - 5 -
2.4 Data analysis - 5 -
Chapter III RESULTS - 9 -
Chapter IV DISCUSSION and CONCLUSION - 13 -
REFERENCES - 17 -

LIST OF TABLES
Table 1 - 22 -
Table 2 - 23 -
Table 3 - 24 -

LIST OF FIGURES
Figure 1 - 25 -
Figure 2 - 26 -
Figure 3 - 27 -
Figure 4 - 28 -

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