A method for characterizing body tissue, comprising:a) transmitting ultrasound into tissue of a body, heating the body tissue by less than 3 degrees Celsiusb) measuring temperature of the tissue, at one or more locations at one or more times during the ultrasound transmission, following the ultrasound transmission, or both andc) using the temperature measurement to determine at least one property of the body tissue, based on differences in absorption of ultrasound, differences in cooling rate of the tissue following the ultrasound transmission, or both.
