Fan Audrey P, Guo Jia, Khalighi Mohammad M, Gulaka Praveen K, Shen Bin, Park Jun Hyung, Gandhi Harsh, Holley Dawn, Rutledge Omar, Singh Prachi, Haywood Tom, Steinberg Gary K, Chin Frederick T, Zaharchuk Greg
From the Departments of Radiology (A.P.F., J.G., P.K.G., B.S., J.H.P., H.G., D.H., O.R., P.S., T.H., F.T.C., G.Z.) and Neurosurgery (G.K.S.), Stanford University, CA; and Global Applied Science Lab, GE Healthcare, Menlo Park, CA (M.M.K.).
Stroke. 2017 Sep;48(9):2441-2449. doi: 10.1161/STROKEAHA.117.017773. Epub 2017 Aug 1.
Arterial spin labeling (ASL) MRI is a promising, noninvasive technique to image cerebral blood flow (CBF) but is difficult to use in cerebrovascular patients with abnormal, long arterial transit times through collateral pathways. To be clinically adopted, ASL must first be optimized and validated against a reference standard in these challenging patient cases.
We compared standard-delay ASL (post-label delay=2.025 seconds), multidelay ASL (post-label delay=0.7-3.0 seconds), and long-label long-delay ASL acquisitions (post-label delay=4.0 seconds) against simultaneous [O]-positron emission tomography (PET) CBF maps in 15 Moyamoya patients on a hybrid PET/MRI scanner. Dynamic susceptibility contrast was performed in each patient to identify areas of mild, moderate, and severe time-to-maximum (Tmax) delays. Relative CBF measurements by each ASL scan in 20 cortical regions were compared with the PET reference standard, and correlations were calculated for areas with moderate and severe Tmax delays.
Standard-delay ASL underestimated relative CBF by 20% in areas of severe Tmax delays, particularly in anterior and middle territories commonly affected by Moyamoya disease (<0.001). Arterial transit times correction by multidelay acquisitions led to improved consistency with PET, but still underestimated CBF in the presence of long transit delays (=0.02). Long-label long-delay ASL scans showed the strongest correlation relative to PET, and there was no difference in mean relative CBF between the modalities, even in areas of severe delays.
Post-label delay times of ≥4 seconds are needed and may be combined with multidelay strategies for robust ASL assessment of CBF in Moyamoya disease.
动脉自旋标记（ASL）磁共振成像（MRI）是一种很有前景的无创性脑血流（CBF）成像技术，但对于存在经侧支循环途径的动脉转运时间异常延长的脑血管疾病患者而言，该技术难以应用。要在临床上得到应用，ASL必须首先在这些具有挑战性的患者病例中针对参考标准进行优化和验证。
我们在一台PET/MRI混合扫描仪上，将标准延迟ASL（标记后延迟 = 2.025秒）、多延迟ASL（标记后延迟 = 0.7 - 3.0秒）以及长标记长延迟ASL采集（标记后延迟 = 4.0秒）与15例烟雾病患者的同步[O] - 正电子发射断层扫描（PET）CBF图进行了比较。对每位患者进行了动态磁敏感对比成像，以识别轻度、中度和重度达峰时间（Tmax）延迟区域。将每次ASL扫描在20个皮质区域的相对CBF测量值与PET参考标准进行比较，并计算中度和重度Tmax延迟区域的相关性。
在重度Tmax延迟区域，标准延迟ASL低估相对CBF达20%，尤其是在烟雾病常见受累的前循环和中循环区域（<0.001）。多延迟采集的动脉转运时间校正使得与PET的一致性得到改善，但在存在长转运延迟的情况下仍低估了CBF（=0.02）。长标记长延迟ASL扫描显示与PET的相关性最强，即使在重度延迟区域，两种方法之间的平均相对CBF也没有差异。
需要标记后延迟时间≥4秒，并且可与多延迟策略相结合，以对烟雾病患者的CBF进行可靠的ASL评估。
