Magnetic Resonance Imaging Group, Singapore Bioimaging Consortium, Agency for Science Technology and Research, Singapore.
NMR Biomed. 2012 Nov;25(11):1209-16. doi: 10.1002/nbm.2790. Epub 2012 Mar 26.
Arterial spin labeling (ASL) MRI provides a noninvasive method to image perfusion, and has been applied to map neural activation in the brain. Although pulsed labeling methods have been widely used in humans, continuous ASL with a dedicated neck labeling coil is still the preferred method in rodent brain functional MRI (fMRI) to maximize the sensitivity and allow multislice acquisition. However, the additional hardware is not readily available and hence its application is limited. In this study, flow-sensitive alternating inversion recovery (FAIR) pulsed ASL was optimized for fMRI of rat brain. A practical challenge of FAIR is the suboptimal global inversion by the transmit coil of limited dimensions, which results in low effective labeling. By using a large volume transmit coil and proper positioning to optimize the body coverage, the perfusion signal was increased by 38.3% compared with positioning the brain at the isocenter. An additional 53.3% gain in signal was achieved using optimized repetition and inversion times compared with a long TR. Under electrical stimulation to the forepaws, a perfusion activation signal change of 63.7 ± 6.3% can be reliably detected in the primary somatosensory cortices using single slice or multislice echo planar imaging at 9.4 T. This demonstrates the potential of using pulsed ASL for multislice perfusion fMRI in functional and pharmacological applications in rat brain.
动脉自旋标记 (ASL) MRI 提供了一种无创的灌注成像方法，并已应用于大脑神经激活的映射。虽然脉冲标记方法已在人类中得到广泛应用，但在啮齿动物脑功能 MRI (fMRI) 中，专用颈部标记线圈的连续 ASL 仍然是首选方法，以最大限度地提高灵敏度并允许进行多切片采集。然而，额外的硬件不容易获得，因此其应用受到限制。在这项研究中，针对大鼠脑 fMRI 对流动敏感交替反转恢复 (FAIR) 脉冲 ASL 进行了优化。FAIR 的一个实际挑战是传输线圈的尺寸有限导致全局反转不理想，从而导致有效标记降低。通过使用大体积传输线圈和适当的定位来优化身体覆盖范围，与将大脑定位在等中心相比，灌注信号增加了 38.3%。与长 TR 相比，通过优化重复和反转时间，信号增益额外增加了 53.3%。在前爪电刺激下，在 9.4T 下使用单切片或多切片 echo 平面成像，可以可靠地检测到初级体感皮层中的 63.7 ± 6.3%的灌注激活信号变化。这表明，在功能和药理学应用中，使用脉冲 ASL 进行多切片灌注 fMRI 具有潜力。
