The ESR dosimetric features of strontium sulfate and temperature effects on radiation-induced signals

ESR investigation on the potential use of potassium citrate as a dosimeter material

Un-irradiated potassium citrate exhibited a weak ESR singlet at g = 2.0045 ± 0.0003 with peak-to-peak line-width of ΔH_pp = 0.16 mT. However, multi-resonance signals spreading over a magnetic field range of ~5 mT were observed in gamma irradiated potassium citrate. A linear function of absorbed radiation dose was found to describe well the dose-response curves of the resonance signals A, B and C in a dose range of 5-5000 Gy. Room temperature fading study showed that radiation-induced radicals in potassium citrate are highly stable but less stable when exposed to the sunlight. Three different radical species were found to describe well experimental room temperature ESR spectrum of irradiated potassium citrate. The resonance signal B can be used in measuring the accidental radiation doses and the radiation doses used in food industry, at least up to a dose of 5 kGy. Further studies were needed in order to increase the sensitivity of potassium citrate at low radiation doses.

Characterization of phenolic pellets for ESR dosimetry in photon beam radiotherapy

This work deals with the dosimetric features of a particular phenolic compound (IRGANOX 1076^®) for dosimetry of clinical photon beams by using electron spin resonance (ESR) spectroscopy. After the optimization of the ESR readout parameters (namely modulation amplitude and microwave power) to maximise the signal without excessive spectrum distortions, basic dosimetric properties of laboratory-made phenolic dosimeters in pellet form, such as reproducibility, dose-response, sensitivity, linearity and dose rate dependence were investigated. The dosimeters were tested by measuring the depth dose profile of a 6 MV photon beam. A satisfactory intra-batch reproducibility of the ESR signal of the manufactured dosimeters was obtained. The ESR signal proved to increase linearly with increasing dose in the investigated dose range 1-13 Gy. The presence of an intrinsic background signal limits the minimum detectable dose to a value of approximately 0.6 Gy. Reliable and accurate assessment of the dose was achieved, independently of the dose rate. Such characteristics, together with the fact that IRGANOX 1076^® is almost tissue-equivalent, and the stability of the ESR signal, make these dosimeters promising materials for ESR dosimetric applications in radiotherapy.