Abstract #4380

Patterns of bold signal responses to progressive hypercapnia enhance the interpretation of underlying cerebrovascular pathologies

Joseph A Fisher^1,2,3, Olivia Sobczyk¹, Adrian P Crawley⁴, Julien Poublanc⁴, Paul Dufort¹, Lashmi Venkatraghavan⁵, David J Mikulis^1,4, and James Duffin^2,3

¹Institute of Medical Sciences, University of Toronto, Toronto, ON, Canada, ²Department of Physiology, University of Toronto, Toronto, ON, Canada, ³Departments of Anaesthesia, University Health Network, Toronto, ON, Canada, ⁴Joint Department of Medical Imaging and the Functional Neuroimaging Laboratory, University Health Network, Toronto, ON, Canada, ⁵Department of Anaesthesia, University Health Network, Toronto, ON, Canada

We surveyed the varied patterns of BOLD changes in response to a ramp CO₂ stimulus ranging from hypocapnia to hypercapnia in 10 healthy individuals and 10 patients with steno-occlusive disease. The patterns of response fell into 4 types, based on the two linear slopes fitted to each range. Maps of these types on a voxel by voxel basis were compared to cerebrovascular reactivity (CVR) calculated as the linear slope over the whole ramp. We suggest that for assessing cerebrovascular reactivity, CVR and type scoring enhance the interpretation of each other, and that modeling the possible underlying patho/physiologies to explain the type patterns is the portal to further work.

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