Middle Cerebral Artery Blood Flow Velocity Changes in Response to Precise Targeting of End-Tidal CO2 & O2: A Comparative Study between Transcranial Doppler Ultrasound & Phase Contrast Magnetic Resonance Angiography

Jackie Leung¹, Arun Mohanta¹, Amir Behpour^1,2, Neil Sokol², Andrea Kassner^1,2

Transcranial Doppler ultrasonography (TCD) and phase contrast MR angiography (PCMRA) are both capable of assessing cerebral blood flow velocity changes in response to a vasoactive stimulus. TCD is widely used because it is inexpensive and accessible, despite concerns about measurement variability. PCMRA does not have such limitations. However, previous attempts to correlate TCD and PCMRA readings in the brain have produced inconsistent results. We propose to utilize a reproducible CO2 stimulus with precise end-tidal PCO2 and PO2 targeting to compare blood flow velocities changes in the middle cerebral artery using both modalities.