Study of dose distribution using Anthropomorphic Phantoms and TL Dosimeters

Abstract

This study evaluated dose distribution in radiotherapy protocols using cone beam (100 kVp) and 6 MV beams in two anthropomorphic phantoms: a three-dimensionally (3D) printed skull and the Alderson phantom, with thermoluminescent dosimeters (TL) MTS-N (LiF:Mg,Ti). In the first experiment, 27 TL dosimeters were placed in internal and external regions of the skull, irradiated with a planned dose of 2 Gy in bilateral beams and preceded by a cone beam sequence. Internal dose measurements ranged from 845.92 ± 7.87 mGy to 1041.58 ± 9.69 mGy, representing 40–55% of the planned dose, with the highest absorption in the posterior brain region. Externally, doses corresponded to about 60% of the internal values in the same lateral regions, reflecting the complexity of energy distribution in heterogeneous tissues. In the second experiment, 260 TL dosimeters were distributed in simulated organs of the Alderson phantom, irradiated with a 137Cs beam focused on the spinal cord (166.67 mGy). Organs closest to the beam, such as lungs and heart, received doses significantly higher than the spinal cord (153.21% and 155.61%, respectively), while deeper tissues, such as the spleen and iliacs, presented lower percentages (109.06% and 106.84%). Measurement uncertainties varied, being higher in large organs like the large intestine (24.79%) and superficial tissues like soft tissue (49.96%). The results highlight the efficiency of TL dosimeters in dose validation and underscore the importance of protocol adjustments to address individual patient characteristics, minimizing healthy tissue exposure. The use of anthropomorphic phantoms proved essential for investigating dose distribution heterogeneity, contributing to advancements in radiotherapy precision and safety, with direct impact on treatment efficacy and cancer patients' quality of life.