The radiation therapy is applied on around 50% of the cancer patients. As we know, before implementing a radiation treatment planning system in the clinic, the dose-calculation measurement must be validated using rigorous, clinically relevant criteria [1]. Percent Depth Doses (PDD), Dose Profile (DP), Open Collimator Factor (OCF) etc., are measured for all numbers of square fields for Treatment Planning System XiO, version 4.7, for 6 and 15 MV photons energies and for 15˚, 30˚, 45˚, 60˚ wedge, which were employed to obtain the profiles in any depth. The measurements were conducted also for different energies of electron beam and TPS calculation algorithms.
One of the major challenges to the more widespread use of individualized, dosimetry-based radioiodine treatment of Graves' disease is the development of a reasonably fast, simple, and cost-effective method to measure thyroidal 131I kinetics in patients. Even though the fixed activity administration method does not optimize the therapy, giving often too high or too low a dose to the gland, it provides effective treatment for almost 80% of patients without consuming excessive time and resources. In this article two simple methods for the evaluation of the kinetics of 131I in the thyroid gland are presented and discussed. The first is based on two measurements 4 and 24 h after a diagnostic 131I administration and the second on one measurement 4 h after such an administration and a linear correlation between this measurement and the maximum uptake in the thyroid. The thyroid absorbed dose calculated by each of the two methods is compared to that calculated by a more complete 131I kinetics evaluation, based on seven thyroid uptake measurements for 35 patients at various times after the therapy administration. There are differences in the thyroid absorbed doses between those derived by each of the two simpler methods and the "reference" value (derived by more complete uptake measurements following the therapeutic 131I administration), with 20% median and 40% 90-percentile differences for the first method (i.e., based on two thyroid uptake measurements at 4 and 24 h after 131I administration) and 25% median and 45% 90-percentile differences for the second method (i.e., based on one measurement at 4 h post-administration). Predictably, although relatively fast and convenient, neither of these simpler methods appears to be as accurate as thyroid dose estimates based on more complete kinetic data.
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