Crystals of natural quartz for luminescence in vivo dosimetry in nuclear medicine: experimental investigation of the dosimetric properties

As a result of investigation of dosimetric properties of natural quartz crystals of the silica sand of the Bryansk oblast carried out by measuring intensity of luminescence caused by annealing the crystals after their exposure to ionizing radiation the following was obtained: a) in a range of radiation doses from 1 to 15 Gy linear relationship between dose and luminescence intensity was found, this shows potential use of natural quartz crystals as ionizing radiation dosimeters in the specified range of absorbed doses; b) to guaranty the reproducibility and stability of the TL signal the temperature of annealing the crystals should not exceed 450 °С, at higher temperatures the TL response as a function of the absorbed dose will depend on the temperature; c) a heating rate of 1 °C/s is optimal for natural quartz crystals, increase in heating rate up to 10 °C/s causes reduction of fluorescence intensity to 32% of its initial level; d) comparison of maximum luminescence intensity of natural quartz crystals and standard Al 2O 3:C detector at the same annealing temperature (450 °С) and luminescence peak (~ 210 °С), as well as the same heating rate (1 °C/s), radiation sensitivity of Al 2O 3:C crystals is 6.7 times higher than the sensitivity of the natural quartz crystals. However, the cost of Al 2O 3:C detectors is hundreds times higher than the potential cost of natural quartz crystals, this is the basis for further research into the possibility of using natural quartz crystals for in vivo dosimetry in nuclear medicine; e) preferential use of luminescent natural quartz crystal-based detectors as accumulating dosimeters is determined not only by their lower price, but also by convenience of their use, i.e. placement on a patient's body, due to their small size (up to microscopic) and absence of wired connection to a recording system; f) absorbed dose from gamma component of 131I cumulated for 24 hours of irradiation of an adult physical phantom with account of radioiodine activity in the thyroid gland of 3.7´10 7 Bq ranges from 27±2 µGy to 89±4 µGy, depending on the localization of luminescent dosimeters on a body (forehead, maxillofacial joints, neck); g) according to data of clinical measurements the individual rate of accumulation of 131I in the thyroid and the correspondent individual cumulated dose in the organ can vary significantly, therefore the use of individual in vivo dosimetry in a course radioiodine therapy of thyroid cancer is very important.