Abstract: A system for detecting an abnormality in a subject's cerebrovascular response to a vasoactive stimulus in at least one region of interest (ROI) of the subject's brain The system comprises a system for generating the vasoactive stimulus (SVS), the SVS including a gas delivery device and a control system operable to deliver controlled amounts of carbon dioxide effective to attain at least one of a series of targeted increments or decrements in the subject's PetCO2, for a series of respective intervals; an imaging system comprising an MRI scanner for generating response signals corresponding to the subject's vasoactive response to the vasoactive stimulus; and a computer for analyzing the response signals, the computer including program code for computing at least one value representing a quantitative measure of the subject's cerebrovascular reactivity for the ROI, wherein the at least one value is obtained for a specific portion of the subject's vasoactive response in the ROI, the specific portion of the subject

Abstract: An algorithm including program code for analyzing a specific portion of the vasoactive response to the vasoactive stimulus corresponding to a to sub-range of increments and/or decrements of stimuli within the full range of the vasoactive stimulus, the sub-range characterized in that is more sensitive to identifying reductions in vascular reactivity in the ROI.