Evaluating dose distributions of normal organs for patients undergoing VMAT therapy of nasopharyngeal carcinoma using Rando phantom and TLD-100H

BACKGROUND: The routine radiation therapy treatment planning does not include secondary radiation and peripheral doses resulting from radiotherapy exposure in patients with nasopharyngeal carcinoma (NPC) undergoing Volumetric Modulated Arc Therapy (VMAT) using an linear accelerator (linac) of Axesse (Elekta 2538). OBJECTIVE: VMAT has a better dose conformity of the tumor and is also operated by adjusting the shapes of mulileaf collimator. However, such treatment is potentially important to improve the accuracy of estimated health risks. METHODS: This study aimed to evaluate the equivalent dose of organ or tissue ([Formula: see text]) and effective dose ([Formula: see text]) for normal organs using the Alderson Rando phantom as an equivalent of the human body. Thermoluminescent dosimeters (TLD-100H) were calibrated by 6 MV X-ray originated by the linac. A total of 252 TLDs were used. These TLDs were inserted into phantom organ or tissue which closely approximated to these places. RESULTS: The thyroid dose ([Formula: see text]) had the highest dose, 1840 [Formula: see text] 202 mSv/treatment. The [Formula: see text] of the Rando was 7.11 [Formula: see text] 0.61 mSv/treatment, as estimated using ICRP 103. The skin doses ([Formula: see text]) varied significantly outside the treatment field and decreased as the distance from the treatment field increased. CONCLUSIONS: This study can be referred to practical guidance regarding radiation protections of the public.