BS ISO 13304‑1:2020 Radiological protection — Minimum criteria for electron paramagnetic resonance (EPR) spectroscopy for retrospective dosimetry of ionizing radiation. 5 Laboratory safety requirements 5.1 Magnetic field With conventional EPR spectrometers, the magnetic field (for EPR signals with g-factor near 2,0, typically 350 mT for X-band and 1 200 mT for Q-hand) is restricted to the region between the pole caps of the magnets, and therefore, there is no associated health risk (can affect watches or credit cards if brought very close to the pole gap). Due to the open nature of some in vivo EPR spectrometers, the magnetic field (for EPR signals with g-factor near 2,0, 40 mT for L-band) combined with large gaps between the poles has the potential to project the 0,5 mT line beyond the confines of the room. This line needs to be determined and appropriate shielding placed for areas that exceed this limit and that are accessed by the general public. The establishment of the 0,5 mT limit is based on concerns about potential effects on pacemakers, which could pose a significant hazard from the magnetic fields that are employed with open in vivo EPR spectrometers. The conventional limit is 0,5 mT (which is very conservative) and surveys should be made to confirm that this field is not exceeded where a person with a pacemaker could be positionedlS3l. Effects of modulation fields on tissues or tooth restorations are not a significant hazard. 5.2 Electromagnetic frequency 5.2.1 in vitro measurement The configurations used for in vitro measurements have no hazard for exposure of operators, as the spectrometer usually fully constrains the microwave to the sample with no significant amount distributed out side of the resonator. 5.2.2 in vivo measurement Measurements in vivo have the potential hazard of local heating of tissue. The operative safety limit is that established for NMR in terms of permissible rates of energy absorption. In practice, this is a potential hazard only at high incident microwave power levels — typically >1 W, which is at least a factor of 3 greater than that in existing instruments. 5.3 Biohazards from samples Biological samples measured in vitro should be handled in conformance to the rules of the jurisdiction for routine practice for handling biological samples. Measurements of teeth in vivo should follow the routines practiced for ordinary dentistry in regard to potential contamination from subjects to operators or other subjects. 6 Collection/selection and...
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