Blood flow and heat sources in forearm measured with acoustothermography

The values of the blood flow and heat sources in the human forearm under the physical load were obtained with acoustothermometry. The probe of the multichannel acoustothermograph developed in IAP of RAS was used to measure the thermal acoustic radiation. The frequency band of the acoustothermograph was 1.2-2.7 МГц, the threshold sensitivity was 0.3 K at the integration time 10 s. Human volunteers clenched - unclenched the fists during 100 s. They made 120  5 movements for this time. To decrease the blood flow in the forearm a tourniquet was applied on the volunteer's shoulder. The experimental results showed that the forearm temperature increased and reached the maximum value after 100 s of work without the tourniquet and after 200 s of work with the tourniquet and thereafter decreased. The acoustobrightness temperature increased on about 1.5 К without the tourniquet and on about 0.7 К with the tourniquet. The results allowed to estimate the blood flow: 0.023 1/min. This value is confirmed with literature data 0.02-0.07 1/min. The blood flow was increased 7.5-fold under the physical load. The heat source was 0.0043 K/s. The heat equation with the blood flow (Pennes equation) was used to calculate the temperature in the depth of the forearm. The calculation showed that the forearm temperature maximum was 36°С in the rest. Under the physical load the additional heat sources increased the temperature up to 37°С and the blood flow increased the temperature up to 38°С.