A method of detecting cellular damage within a subject comprises transmitting low frequency ultrasound (20 MHz or below) into a selected site within the subject wherein the selected site has been exposed to a stress capable of causing cellular death at the selected site. At least a portion of ultrasound backscattered from the ultrasound transmitted into the selected site is received. The received backscattered ultrasound is compared to a control backscatter measurement. An increase or a decrease in intensity or spectral slope of the received backscattered ultrasound when compared to the control backscatter measurement indicates cellular death or damage at the selected site within the subject.