Tomoki Nomura

Computation of Temperature Elevation in a Fetus Exposed to Ambient Heat and Radio Frequency Fields

Temperature elevation in the fetus is of concern for excess heat load, including that from radio-frequency exposure. No previous study succeeded in simulating the temperature difference between the mother and fetus. This study develops a thermal model for a pregnant woman, and then applies it to simulate the temperature variations due to ambient heat exposure and RF exposure. When the pregnant woman model is exposed to ambient temperature of 35–45°C, the core temperature elevations in the mother and the fetus are almost identical. Contrarily, the fetal temperature elevation for radio-frequency exposure is higher than that in the mother.

Computation of temperature elevation in fetus due to radio-frequency exposure with a new thermal modeling

The temperature elevation in the fetus is of concern for radio-frequency exposure. According to the IEC standard, the temperature elevation in the fetus should be lower than 0.5°C for exposure in magnetic resonance equipment. However, no previous study succeeded to simulate the temperature difference between the fetus and mother in the thermoneutral condition. The present study proposes a new thermal modeling for the pregnant woman model. The thermal modeling is then applied to the temperature variation for plane wave exposure at 80 MHz. From computational results, the core temperature in the fetus at the themoneutral condition was 37.5°C, which is 0.35°C larger than that of the mother and coincident with measured data. When the pregnant woman model is irradiated by the plane wave with the whole-body averaged specific absorption rate of 2 W/kg for 1 hour, the temperature elevation in the fetus is 0.50°C, which is larger than that in the mother by 0.11°C.