應用盲壓縮感知加速多激發角度T1圖譜的可行性研究

Feasibility of Accelerated Variable Flip Angle T1 Mapping Using Blind Compressed Sensing

石書輔(Shu-Fu Shih)

指導教授 ： 鍾孝文

國立臺灣大學/電機資訊學院/生醫電子與資訊學研究所/碩士(2017年)

https://doi.org/10.6342/NTU201702362

摘要

多激發角度T1圖譜是一種基於非平衡梯度回訊序列的T1定量方法，此方法利用多組來自不同激發角度的影像以準確估計T1，因此常需要在掃描時間及不同激發角度的數量上作權衡。本論文探討了利用盲壓縮感知以加速多激發角度T1圖譜的可行性，這種技術可以在不預先假設一組固定的基底函數之下，使用稀疏限制重建影像。我們使用真實大腦影像，運用後處理的方式比較不同取樣方式的結果並討論演算法參數的選擇。我們在初步的結果中展示了5倍加速後的定量T1圖譜，希望能提供此更快速的多激發角度T1圖譜實際應用時的參考。

關鍵字

多激發角度T1圖譜 ； T1圖譜 ； 壓縮感知 ； 盲壓縮感知 ； 取樣方式

並列摘要

Variable flip angle T1 mapping is a T1 quantification technique based on spoiled gradient echo (SPGR) sequence. This method requires multiple images at different flip angles for accurate T1 estimations, so a trade-off is often made between acquisition time and the number of flip angles. This thesis aims to investigate the feasibility of faster variable flip angle T1 mapping by incorporating blind compressed sensing. This technique used sparsity constraint to reconstruct images without the assumption of a fixed dictionary. We retrospectively subsample in vivo brain images and compare the results of quantitative T1 maps with a 5-fold acceleration and provide a reference for practical implementation of a faster variable flip angle T1 mapping.

並列關鍵字

variable flip angle T1 mapping ； T1 mapping ； compressed sensing ； blind compressed sensing ； sampling pattern

參考文獻

[1] Hahn EL. An accurate nuclear magnetic resonance method for measuring spin-lattice relaxation times. Phys Rev 1949; 76:145–146.

[2] Messroghli DR, Radjenovic A, Kozerke S, Higgins DM, Sivananthan MU, Ridgway JP. Modified Look-Locker inversion recovery (MOLLI) for high-resolution T1 mapping of the heart. Magn Reson Med 2004; 52: 141–146.

[3] Homer J, Beevers MS. Driven-equilibrium single-pulse observation of T1relaxation. A re-evaluation of a rapid 'new' method for determining NMR spin-lattice relaxation times. J Magn Reson 1985; 63: 287–297.

[4] Deoni SCL, Rutt BK, Peters TM. Rapid combined T1 and T2 mapping using gradient acquisition in the steady state. Magn Reson Med 2003; 49: 515–526.

[5] Lingala SG, Jacob M. Blind compressive sensing dynamic MRI. IEEE Trans Med Imaging 2013; 32:1132.