An image processing apparatus according to an embodiment includes an input extraction unit, and a parameter estimation unit. The input extraction unit configured to extract, from time sequence images of medical images obtained by performing a blood perfusion imaging scan on a tissue, a region where a main vessel supplying blood input to the tissue is located as an input part and obtain, based on the input part, a time-density sequence of the blood input as an input time sequence. The parameter estimation unit configured to estimate parameters in a model representing the change of the blood flow at each point in the tissue with the input time sequence, based on the input time sequence, the model and the time sequence images, wherein the parameters include a delay undergone by the blood when flowing from the input part to each point in the tissue.
