In the occurrence of damage to the hemodynamic system of the brain, a response is elicited by changes in the supply of blood and oxygen to the tissue. Depending on these different changes, the severity of the hemodynamic impairment can be defined. In this study, we propose a method of accurately measuring quantitative cerebrovascular reserve. This is achieved by applying water correction factors to multiple contrast-agent injection cerebral blood flow measurements. In multiple studies involving volunteers, animal model, and patients, we confirm the correction factors and compare against microsphere perfusion.