功能性磁共振頻譜在3T系統下的可行性:以視覺實驗驗證

Abstract

核磁共振頻譜技術提供了非侵入式方法檢測大腦代謝物濃度的變化，功能性磁振頻譜(functional Magnetic Resonance Spectroscopy，fMRS)為在接受外在刺激下大腦活動時所量測的頻譜訊號(非一般的影像)。此研究在約21分鐘的視覺刺激模式下進行，代謝物量測的時間序列頻譜由LCModel(Linear Combination of Model)計算出每張掃描的濃度、擬合(fitting)及CRLB(Cramér–Rao lower bound)。\n\n近年來，有文獻指出在7T的磁場下利用功能性磁振頻譜技術在腦部視覺皮質區(Visual cortex)在接收視覺刺激下，代謝物濃度有改變的現象，其中包含谷氨酸(Glutamate)、乳酸(Lactate)的濃度在視覺刺激當下會有所增加；葡萄糖(Glucose)有減少的傾向但不明顯。\n\n本研究的目的為在3T的磁場下，當受試者在接受視覺刺激時，探討大腦在視覺區的代謝物濃度變化，並比較有使用相位循環(Phase Cycling, PC)與無相位循環(NO_Phase Cycling, NO_PC)兩種結果有哪些差異。其後我們發現在幾次的實驗裡部分代謝物間出現濃度在某時刻下有相同的跳躍或相同趨勢的現象，尤其是在無相位循環的時候，該現象也比較常出現，為此我們也做了代謝物濃度的相關係數分析，計算不同的代謝物之間的關聯性以及平均結果。

Functional magnetic resonance spectroscopy (fMRS) provides a non-invasive technique to investigate brain metabolism during brain activation. Concentration, fitting and CRLB of the measurements were evaluated from LCModel analysis of time series of spectra measured during 21 mins visual stimulation paradigm\n\nRecently, several researches indicated that using functional magnetic resonance spectroscopy at 7T magnetic field brain metabolism concentration in visual cortex will change during visual stimulation. Glutamate(Glu), Lactate(Lac) increased during periods of stimulation; Glucose (Glc) showed a tendency to decrease, but not significantly.\n\nThe purpose of this study is to investigate metabolism concentration changes at 3T field in MRS during visual stimulation, and compare what kind of difference of phase cycling and not-phase cycling. Then we found a few experiments in concentration between parts of metabolites appear to have the same or the same tendency to jump at a certain time of the phenomenon, especially no_phase cycling.We also calculated correlation coefficient of metabolite and the result of average.