Abstract: Method and apparatus for monitoring a patient having a tumor to determine perfusion tumor heterogeneity wherein a solution containing a tracer, preferably a 2H-saline solution is infused into the patient's bloodstream at a predetermined slow rate to effect perfusion into the tumor. An MRI machine is adjusted to acquire a set of dynamic 2H magnetic resonance images of the tumor. The 2H-images are obtained before infusion, during infusion and post infusion. First, the obtained images are processed to quantitatively determine perfusion per voxel of the images. Next, maps of perfusion parameters are generated to indicate spatial distribution of tumor perfusion. The maps are displayed in color code and analyzed.