Wan Si-hai, Zhang Xue-lin, Xiao Xin-lan, Sun Xin, Xing Hai-fang, Qiu Shi-jun
Diagnostic Imaging Center, Nanfang Hospital, Southern Medical University, Guangzhou 510515, China.
Nan Fang Yi Ke Da Xue Xue Bao. 2008 Mar;28(3):396-8.
To study the fractional anisotropy (FA) and the architecture of the optic radiation fiber tracts of normal adults with magnetic resonance (MR) diffusion tensor imaging (DTI).
Diffusion tensor images were obtained from 30 healthy volunteers without any cerebral abnormalities on conventional MRI. FA and the mean diffusivity (MD) of the optic radiation were measured in the directional encoded color (DEC) maps. The architecture of the optic radiation fiber tracts were displayed with the software of diffusion tensor fiber tracking.
In all subjects, the optic radiation could be readily identified in the DEC maps. The FA value was 0.509-/+0.029 in the left and 0.502-/+0.026 in the right, with the MD value of (0.763-/+0.050) x10(-3) and 0.748-/+0.052)x10(-3) mm2/s, respectively. No significant differences were found in the FA or MD value of the bilateral optic radiation (P>0.05). Diffusion tensor tractography (DTT) demonstrated that the 3 bundles of the optic radiation fibers were located in the lateral sagittal stratum, passing from the lateral geniculate body of the thalamus to the primary visual cortex. The dorsal and lateral bundles passed posteriorly to the superior bank of the calcarine cortex, while the ventral bundle passed anteriorly before making a sharp turn, known as the Meyer loop, and subsequently coursed posteriorly to terminate in the inferior margin of the calcarine cortex, which was consistent with the results of classic anatomical studies.
As a novel method to study the relationship between visual function and optic pathway, DTI and DTT can show the FA and architecture of the optic radiation.
采用磁共振（MR）扩散张量成像（DTI）研究正常成年人视辐射纤维束的各向异性分数（FA）及纤维束结构。
对30名常规MRI检查无任何脑异常的健康志愿者进行扩散张量成像。在方向编码彩色（DEC）图中测量视辐射的FA及平均扩散率（MD）。应用扩散张量纤维束示踪软件显示视辐射纤维束的结构。
所有受试者在DEC图中均可清晰识别出视辐射。左侧FA值为0.509±0.029，右侧为0.502±0.026，MD值分别为（0.763±0.050）×10⁻³和（0.748±0.052）×10⁻³mm²/s。双侧视辐射的FA或MD值差异无统计学意义（P>0.05）。扩散张量纤维束示踪（DTT）显示，视辐射纤维束的3束纤维位于外侧矢状层，从丘脑外侧膝状体延伸至初级视觉皮层。背侧束和外侧束向后走行至距状沟皮质上缘，而腹侧束向前走行后急转弯形成迈耶袢，随后向后走行终止于距状沟皮质下缘，这与经典解剖学研究结果一致。
作为研究视觉功能与视路关系的一种新方法，DTI和DTT可显示视辐射的FA及结构。
