Vessel Size Index and Cerebral Blood Volume Maps using Hypercapnic Contrast at 3 T

Introduction: Recent studies using respiratory challenges and MR BOLD-based contrast have shown the possibility to create cerebral blood volume (CBV) maps using 50% O2 gas at 3T [1] or the mean vessels radius (VSI) with carbogen (95% O2, 5% CO2) at 7.0T [2]. These measurements do not require intravenous injection of a contrast agent and could be useful to study pathologies such as stroke, trauma or tumor. In the present study, we used a carbogen challenge to compute both CBV and VSI maps at 3T. The use of a multiple spin and gradient echo (SAGE [3]) EPI sequence allowed the acquisition of VSI and CBV values simultaneously with a high temporal resolution. This was used to determine the period of time during which the carbogen gas induced enough difference of magnetic susceptibility between blood and tissue to allow accurate measurements.