A system and method of determining hemodynamic parameters of a patient is described. A background image data set is obtained prior to the administration of a contrast agent. A series of image data sets is obtained during the first passage of the bolus through a parenchymal volume. The pre-contrast-agent image is subtracted from image data sets obtained during the first passage of the contrast agent bolus, so that the amount of contrast agent in the volume may be determined. The time series of the amount of contrast agent is computed to determine the arterial input function (AIF) which may be used to determine a tissue impulse response, and hemodynamic parameters such as cerebral blood flow (CBF), cerebral blood volume (CBV) and mean transit time (MTT).