以擴散張量造影建立大腦連結網路:單次激發式與螺旋槳式平面回訊造影比較

Construction of brain connectivity network using diffusion tensor imaging:A comparison between single-shot EPI and PROPELLER EPI

林雅琳(Ya-Lin Lin)

指導教授 ： 周銘鐘

高雄醫學大學/健康科學院/醫學影像暨放射科學系碩士班/碩士(2014年)

https://doi.org/10.6832/KMU.2014.00001

摘要

一直以來有許多研究探討大腦內部的結構與功能，所追求的就是能夠更深入洞悉整個大腦的結構組織與功能的關聯性，其中包括使用擴散張量造影技術建構出大腦連結網路。擴散張量造影技術在近幾來被廣泛應用，但是由於使用單次激發平面回訊技術所收取的影像在空氣與組織的交界處會有影像扭曲的缺點，將有可能造成纖維追蹤上的錯誤。在本實驗中將使用periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER)回音平面造影(EPI)技術收取影像，降低影像扭曲的問題，減少錯誤纖維的產生，因此，本研究的目的就是利用螺旋槳式擴散張量影像(PROPELLER DTI)建立準確且可靠的大腦連結網路。
本實驗包含40位受試者(男：20，女：20)，所有受試者都經過3 T磁振造影儀做掃描，收取3D T1-WI、T2-WI以及使用PROPELLER EPI的DTI影像，另外多收取單次激發 EPI的DTI影像做為比較。影像收取完成之後經過擴散權重影像的纖維追蹤產生白質纖維，並藉由Automated Anatomical Labeling (AAL)將大腦分成116區域，最後將白質纖維對位到116個區域，完成大腦網路連結。
結果顯示影像扭曲的問題在PROPELLER DTI中獲得改善，而在大腦網路連結圖也顯示PROPELLER DTI所產生的網路連結在額葉及小腦是有較弱的連結性，而其餘區域是有較強的連結性。此外，本研究也比較了男性與女性的腦部纖維連結差異，發現男性在半腦內有較強的連結，而女性在半腦間有較強的連結。在未來我們可以進一步利用PROPELLER DTI建立之大腦連結網路所提供之訊息，幫助我們更了解大腦的特殊疾病。

關鍵字

擴散張量影像 ； 大腦連結網路 ； 纖維追蹤 ； PROPELLER

並列摘要

The brain is the most important organ with complex system to our body. Creating a global architecture of the anatomical connectivity network could help us more understanding how brain organizes and how brain was altered by disorders. Previous studies showed that DTI can successfully trace neuronal fiber tracts in vivo; however, DTI with single shot echo-planar imaging (EPI) has geometric distortion problem which might cause false fiber tracts in tractography. One way to achieving less distortion in DTI images is to use a periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) EPI technique. Therefore, the purpose of this study is to construct the anatomical connectivity network of human brain using DTI with PROPELLER EPI acquisition in order to reduce the distortion problem and improve the accuracy of connectivity analysis. In this study, we compare the connectivity network between DTI datasets with PROPELLER and single shot EPI, and we also attempt to observe sex differences in connectivity network between both techniques. The study enrolled 40 healthy subjects. All subjects underwent MRI scan using a 3T MR System. After acquiring 3D T1WI and distortion-free T2WI, PROPELLER DTI (pDTI) and single-shot DTI (ssDTI) data were acquired for comparison. After data acquisition, DTI tractography was performed to reconstruct all of white matter fiber tracts. Finally, the mean fiber tracts of every pair of regions were calculated as the connectivity indices of the network. The results showed that the PROPELLER DTI images exhibit substantially reduced geometric distortions as compared with single-shot DTI, and the anatomical connectivity network with PROPELLER DTI exhibited stronger connectivity between two brain regions. In addition, the results also found sex differences that the male subjects exhibited stronger connectivity mostly within hemispheres, but the female subjects had stronger connectivity mostly between hemispheres. Moreover, since DTI with PROPELLER EPI acquisition has less susceptibility distortions and more accurate fiber tracts. We concluded that the connectivity network with PROPELLER DTI would be more suitable for investigating the connectivity alterations of human brain in the future.

並列關鍵字

PROPELLER ； tractography ； DTI ； connectivity network ； geometric distortion

參考文獻

1.Le Bihan D, Mangin JF, Poupon C, et al. Diffusion tensor imaging: Concepts and applications. J Magn Reson Imaging. 2001;13(4):534-46.

2.Sporns O, Pegors TK. Information-theoretical aspects of embodied artificial intelligence. Lect Notes Artif Int. 2004;3139:74-85.

3.Le Bihan D, Poupon C, Amadon A, Lethimonnier F. Artifacts and pitfalls in diffusion MRI. J Magn Reson Imaging. 2006;24(3):478-88.

4.Jezzard P, Balaban RS. Correction for Geometric Distortion in Echo-Planar Images from B-0 Field Variations. Magnet Reson Med. 1995;34(1):65-73.

5.van Pul C, Roos FG, Derksen OS, et al. A comparison study of multishot vs. single-shot DWI-EPI in the neonatal brain: reduced effects of ghosting compared to adults. Magn Reson Imaging. 2004;22(9):1169-80.