A Comparison Study of Readout Segmentation of Long Variable Echo-Trains (RESOLVE) and Single-Shot Echo Planar Imaging Techniques: An Animal Model

可變長回訊序列分段讀出回訊平面與單次激發回訊平面造影技術之比較研究：動物模型

蕭佳吉(Chia-Chi Hsiao) ； 陳博洲(Po-Chou Chen) ； 張瓊勻(Chiung-Yun Chang) ； 郭佩綺(Pei-Chi Guo) ； 饒若琪(Jo-Chi Jao)

《臺灣醫事放射期刊》 6卷1期 (2018/06) Pp. 25-34

https://doi.org/10.6717/JTMRT.201806_6(1).0004

摘要

Recently, echo-planar imaging (EPI) technique has been widely used in clinical routine diagnosis due to it’s fast scanning feature. However, geometric distortion is often encountered in single-shot EPI (SS-EPI) scanning. How to alleviate the EPI geometry distortion to improve the diagnostic accuracy needs to be concerned. Readout segmentation of long variable echo-trains echo planar image (RESOLVE-EPI) relevant study is an emerging research field and rapidly becomes a hot research issue. However, establishing an animal model for research is still at early stage. Since animal size is small, it is often to have severe image distortion due to strong susceptibility effect. This study aimed to evaluate and compare single-shot echo planar imaging (SS-DW-EPI) and RESOLVE-DW-EPI implemented with parallel imaging technique on normal New Zealand rabbits brain using Siemens Magnetom Skyra 3T whole body magnetic resonance imaging (MRI) scanner. Distortion of images obtained using SS-DW-EPI and RESOLVE-DW-EPI with or without generalized autocalibrating partial parallel acquisition (GRAPPA) was evaluated. Regions of interest (ROIs) measurement included mean signal intensity (T1W, T2W, TraceW images) and apparent diffusion coefficient (ADC). Image fusion was performed. It was found that geometry distortions on RESOLVE-DW-EPI images were significantly smaller than the traditional SS-DW-EPI images. RESOLVE-DWI provides better image quality compared with SS-DW-EPI. Traditional SS-DW-EPI images with higher generalized autocalibrating partially parallel acquisitions (GRAPPA) accelerating factor and RESOLVE-DWI can be effectively reduce image distortions. The higher the GRAPPA accelerating factor was, the larger the mean signal intensity was on both traditional SS-DW-EPI and RESOLVE-DW-EPI images. On the contrary, the mean ADC value obtained using both traditional SS-DW-EPI and RESOLVE-DW-EPI decreased with increasing GRAPPA accelerating factor. The results demonstrated that to establish an animal model for studying DWI features with minimum distortion is feasible and has significant clinical values.

關鍵字

Diffusion-Weighted Imaging ； RESOLVE Echo Planar Imaging ； GRAPPA ； Animal model

並列摘要

近年來，回訊平面造影(EPI)技術由於其快速掃描特性，被廣泛地應用在臨床例行性診斷上。然而，單次激發回訊平面造影(SS-EPI)掃描影像產生的幾何形變為一待解決的問題。如何減少SS-EPI之 幾何形變，提高確診率成為研究主流之一。可變長回訊序列分段讀出回訊平面造影(RESOLVE-EPI) 技術的相關研究為一新興的研究領域，並迅速成為研究的熱門議題。然而，建立一個研究動物模型仍處於起步階段。由於動物體型小，易受強烈的感磁效應影響，預期會誘發嚴重的影像形變。因此，本研究旨在於西門子Magnetom Skyra 3T全身磁振掃描儀上使用單次激發擴散加權回訊平面造影(SS-DW-EPI)和可變長回訊序列分段讀出擴散加權回訊平面造影(RESOLVE-DW-EPI)結合平行造影技術進行評估並比較紐西蘭大白兔腦部影像。本研究比較廣義有無結合自動校準部分並行採集技術(GRAPPA)的SS-DW-EPI和RESOLVE-DW-EPI間之幾何形變，並評估兩種技術之正常紐西蘭大白兔腦部影像特徵。紐西蘭大白兔腦部影像的感興趣區量測包括平均訊號強度(T1加權、T2加權、示蹤加權影像)及表觀擴散係數(ADC)和進行影像融合。實驗發現RESOLVE-DW-EPI影像的幾何形變明顯小於傳統的 SS-DW-EPI影像。RESOLVE-DWI可提供優於SS-DW-EPI的影像品質。隨著GRAPPA的加速因子增加，傳統的SS-DW-EPI和RESOLVE-DW-EPI影像的平均訊號強度均變大。相反地，傳統的SS-DWI-EPI和RESOLVE-DW-EPI表觀擴散係數圖像的平均ADC值隨著GRAPPA加速因子增加而變小。結果證實建立一個用於研究最小幾何形變擴散加權影像(DWI)特徵的動物模型是可行且具臨床價值的。

並列關鍵字

擴散加權造影 ； 可變長回訊序列分段讀出回訊平面造影 ； 廣義有無結合自動校準部分並行採集 ； 動物模式