A framework for the accurate and noninvasive determination of perfusion in a mammal is provided, including a novel scaling law of a form-function relationship between the number of capillaries in a vascular network as compared to the perfusion of such network. Methods are disclosed that apply such scaling laws in connection with the steps of determining a capillary density of a targeted tissue comprising at least a portion of a capillary network, and calculating perfusion of the targeted tissue based on the determined capillary density of the targeted tissue. Additional methods for determining a therapeutic drug dosage for a biological subject are also provided based on the scaling-laws hereof, as well as methods of identifying a deviation in perfusion rates in a mammal noninvasively.
