ID Number		2559
Study Type		Engineering & Physics
Model		Verification of exposure guidelines for humans by determining the association between the electromagnetic and thermal dose in the eyes with the reported ocular effects due to treatment of cancer in the head and neck by RF hyperthermia (434 MHz, 60 min) that causes the eyes to receive a considerable RF exposure.
Details		AUTHORS' ABSTRACT: Adibzadeh et al. 2016 (IEEE #6305): The eye is considered to be a critical organ when determining safety standards for radio frequency (RF) radiation. Experimental data obtained using animals showed that RF heating of the eye, particularly over a specific threshold, can induce cataracts. During the treatment of cancer in the head and neck by hyperthermia, the eyes receive a considerable dose of RF radiation due to stray radiation from the prolonged (60 min) and intense exposure at 434 MHz of this region. In the current study, we verified the exposure guidelines for humans by determining the association between the electromagnetic and thermal dose in the eyes with the reported ocular effects. We performed a simulation study to retrospectively assess the specific absorption rate (SAR) and temperature increase in the eyes of 16 selected patients (encompassing a total of 74 treatment sessions) whose treatment involved high power delivery as well as a minimal distance between the tumor site and the eye. Our results show that the basic restrictions on the peak 10 g spatial-averaged SAR (10 W kg(-1)) and peak tissue temperature increase (1 °C) are exceeded by up to 10.4 and 4.6 times, on average, and by at least 6.2 and 1.8 times when considering the lower limit of the 95% confidence interval. Evaluation of the acute effects according to patients' feedback (all patients), the common toxicity criteria scores (all patients) and an ophthalmology investigation (one patient with the highest exposure) revealed no indication of any serious acute ocular effect, even though the eyes were exposed to high electromagnetic fields, leading to a high thermal dose. We also found that, although there is a strong correlation (R (2) = 0.88) between the predicted induced SAR and temperature in the eye, there are large uncertainties regarding the temperature-SAR relationship. Given this large uncertainty (129%) compared with the uncertainty of 3D temperature simulations (61%), we recommend using temperature simulations as a dosimetric measure in electromagnetic exposure risk assessments. AUTHORS' ABSTRACT: Adibzadeh, Paulides, van Rhoon (2018): Background and purpose: To protect against any potential adverse effects to human health from localised exposure to radio frequency (100 kHz3 GHz) electromagnetic fields (RF EMF), international health organisations have defined basic restrictions on specific absorption rate (SAR) in tissues. These exposure restrictions incorporate safety factors which are generally conservative so that exposures that exceed the basic restrictions are not necessarily harmful. The magnitude of safety margin for various exposure scenarios is unknown. This shortcoming becomes more critical for medical applications where the safety guidelines are required to be relaxed. The purpose of this study was to quantify the magnitude of the safety factor included in the current basic restrictions for various exposure scenarios under localised exposure to RF EMF. Materials and methods: For each exposure scenario, we used the lowest thermal dose (TD) required to induce acute local tissue damage reported in literature, calculated the corresponding TD-functional SAR limits (SARTDFL) and related these limits to the existing basic restrictions, thereby estimating the respective safety factor. Results: The margin of safety factor in the current basic restrictions on 10 g peak spatial average SAR (psSAR10g) for muscle is large and can reach up to 31.2. Conclusions: Our analysis provides clear instructions for calculation of SARTDFL and consequently quantification of the incorporated safety factor in the current basic restrictions. This research can form the basis for further discussion on establishing the guidelines dedicated to a specific exposure scenario, i.e. exposure-specific SAR limits, rather than the current generic guidelines.
Findings		Effects (only at thermal levels)
Status		Completed With Publication
Principal Investigator		Erasmus MC, Rotterdam, The Netherlands
Funding Agency		?????
Country		NETHERLANDS
References		Adibzadeh, F et al. Phys Med Biol., (2016) 61:488-503 Adibzadeh, F et al. INTERNATIONAL JOURNAL OF HYPERTHERMIA., (2018) 34:1248-1254
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