Does Pulsed Arterial Spin-Labeling Selectively Underestimate Responses to Global Challenges?

Felipe B. Tancredi^1,2, Claudine J. Gauthier, ^2,3, Ccile J. Madjar², Richard D. Hoge^1,2

ASL is a technique of particular interest for studies in which hypercapnia challenge is employed. We sought to test whether the shortening in blood transit time that vasodilation by moderate hypercapnia may cause was leading to a systematic underestimation of perfusion responses measured with ASL. We measured flow responses in three different moments: at hypercapnia, during visual stimulus and when both were simultaneously present. We found that the response to the combined stimulus was a linear combination of the responses the individual stimulus alone, thats to say, the focal response to a visual stimulus during hypercapnia challenge was not underestimated. ASL is a technique of particular interest for studies in which hypercapnia challenge is employed. We sought to test whether the shortening in blood transit time that vasodilation by moderate hypercapnia may cause was leading to a systematic underestimation of perfusion responses measured with ASL. We measured flow responses in three different moments: at hypercapnia, during visual stimulus and when both were simultaneously present. We found that the response to the combined stimulus was a linear combination of the responses the individual stimulus alone, thats to say, the focal response to a visual stimulus during hypercapnia challenge was not underestimated.