Thulborn K R, Chang S Y, Shen G X, Voyvodic J T
Department of Radiology, MR Research Center, University of Pittsburgh Medical Center, PA 15213, USA.
NMR Biomed. 1997 Jun-Aug;10(4-5):183-90. doi: 10.1002/(sici)1099-1492(199706/08)10:4/5<183::aid-nbm469>3.0.co;2-w.
Known specialized properties of the human visual cortex have been used to investigate the role of spatial resolution on fMRI using blood oxygenation level dependent (BOLD) echo-planar MRI at 3.0 tesla. The magnitude of BOLD signal changes has been examined at low (3.1 x 3.1 x 3.0 mm3) and high (0.8 x 1.6 x 3.0 mm3) resolution using both gradient-echo and spin-echo EPI. Paradigms were designed to activate primary visual cortex (V1/V2) and more specialized areas associated with detection of color (V4) and motion (V5). Sensitivity of activation maps increased at higher resolution despite the decreased total signal intensity at the smaller voxel size, presumably from reduced partial volume averaging. The greater microvascular selectivity of high-resolution spin-echo imaging enabled distinct activation patterns sensitive to motion to be detected in V1/V2 that were not apparent with gradient-echo imaging. The spatial resolution at 3.0 tesla was constrained by the size of physiological head motion relative to the voxel dimensions rather than SNR or the hemodynamic response of BOLD contrast. The higher spatial resolution at 3.0 tesla with more selective spin-echo EPI can further refine functional mapping within the cerebral cortex.
人类视觉皮层已知的特殊属性已被用于在3.0特斯拉的场强下，利用血氧水平依赖（BOLD）回波平面磁共振成像（MRI）来研究空间分辨率在功能磁共振成像（fMRI）中的作用。使用梯度回波和自旋回波EPI技术，分别在低分辨率（3.1×3.1×3.0立方毫米）和高分辨率（0.8×1.6×3.0立方毫米）下，检测了BOLD信号变化的幅度。设计了相关范式来激活初级视觉皮层（V1/V2）以及与颜色检测（V4）和运动检测（V5）相关的更特殊区域。尽管在较小体素尺寸下总信号强度降低，但激活图的灵敏度在高分辨率下有所提高，这可能是由于部分容积平均效应的减少。高分辨率自旋回波成像具有更高的微血管选择性，能够在V1/V2中检测到对运动敏感的独特激活模式，而梯度回波成像则未显示出这种明显的激活模式。3.0特斯拉下的空间分辨率受到相对于体素尺寸的生理性头部运动大小的限制，而非信噪比或BOLD对比的血液动力学响应。3.0特斯拉下更高的空间分辨率以及更具选择性的自旋回波EPI能够进一步优化大脑皮层内的功能图谱。
