a method and device for measuring blood flow through a blood vessel within human or animal bodies . it utilizes the principle of energy conversion to heat by myocardial activity , organ metabolism , and laminar frictional flow in blood vessels and measures the heat dissipation through the vessel wall with obstruction to flow . when the device of the invention is placed next to the vessel wall , the output signal correlates blood flow with temperature . with an obstruction to flow , the temperature drops . the device is placed in series proximal and distal to the repaired vessel to be studied . the leads are brought through the skin and attached to a temperature monitor .