ID Number		1711
Study Type		In Vivo
Model		Studies of RF exposure to humans at thermal levels and thermal/non-thermal RF exposure of human cancer cells.
Details		Thermoregulatory mechanisms are reviewed to assess the ability of humans to dissipate heat and maintain core temperature in response to RF energy absorption. The authors report core temperature is meticulously regulated (37-37.5 degrees C). Further, organ systems (skin, digestive system, muscles) can regulate perfusion levels as well as metabolic activity to help maintain temperature. Numerical models to predict tissue temperature are getting better, but difficult as perfusion rates can be different among people and within different tissues. Human tolerance to temperature excursions is generally significant. The temperature required for significant tissue damamge in animal studies when applied for a few minutes of application is 50 degrees or more, and requires several hundred W/kg SAR. Diathermy treatment for cancer routinely produces local hyperthermia of 40-45 degrees C for 30-60 minutes, with corresponding SAR values of 100-200 W/kg. This does not normally result in significant damage to normal tissues (muscel, skin), but can lead to increases in blood perfusion to 20-40 mL/100 g/min. The human thermoregulatory potential seems to be limited by the cardiac output, which can be increased from 5 L/min to 10 L/min and the abilty to locally increase blood perfusion rates, which for example in the muscle can increase 5-10-fold from a resting level of 2-4 mL/100 g/min. A report from the authors comparing a numerical (FDTD) model with MR (proton resonance frequency shift method) correlated well (within +/- 2-3 W/kg SAR, less than 10% variation). One of the difficult issues reported by the autors is modeling hot spots at tissue boundaries (where 1cm cubic voxels do not completely capture the tissue differences).
Findings		Not Applicable to Bioeffects
Status		Completed With Publication
Principal Investigator		Charite University, Berlin, Germany
Funding Agency		Private/Instit.
Country		GERMANY
References		Wust, P et al. Health Physics, (2007) 92:565-573 Gellermann, J et al. Med Phys, (2006) 33:3912-3920 Wust, P et al. Sci Rep., (2020) 10:13488- Wust, P et al. Cancers., (2022) 14:5349-
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