Dosimetric characteristics of a reusable 3D radiochromic dosimetry material.

Jong Min Park,Ji Hye Han,Jung-In Kim,So-Yeon Park,Chang Heon Choi,Minsoo Chun,Jin Dong Cho

doi:10.1371/journal.pone.0180970

Jong Min Park, Ji Hye Han + Show 5 more

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https://doi.org/10.1371/journal.pone.0180970

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Abstract

PurposeTo investigate the dosimetric characteristics of PRESAGEREU dosimeters.MethodsCommercially available PRESAGEREU dosimeters (size of 10 mm × 10 mm × 45 mm) were divided into two groups, with one of the groups placed at room temperature of 22°C (RT group) and another group placed at low temperature of 10°C (LT group). A total of 3 dosimeters (set of dosimeters) were irradiated at a time, with doses of 1 Gy, 2 Gy, 4 Gy, 8 Gy, 12 Gy, 16 Gy, and 20 Gy, at a nominal dose rate of 400 MU/min at temperature of 22°C. The dosimeters were irradiated three additional times by delivering the same doses as those during the initial irradiations (4 irradiation cycles). Optical density (OD) was assessed using optical CT scanning.ResultsConsidering both linearity and sensitivity of the OD curves, R2 above 0.95 and sensitivity above 0.04 ΔOD/Gy were observed at the 1st irradiation (reading time ≤ 6 h) and 2nd irradiation (reading time = 0.5 h) for the RT group. For the LT group, those values were observed at the 1st irradiation (reading time ≤ 2 h), and the 3rd and 4th irradiations (both reading times = 0.5 h). Considering the reproducibility of signals in response to the same dose, dosimeters in the RT group showed average deviations among dosimeters less than 5% (the 1st and 2nd irradiations at the reading time of 0.5 h), while for dosimeters in the LT group showed average deviations among dosimeters less than 6% (the 3rd and 4th irradiations at the reading time of 0.5 h). For the rest, the OD curves were not linear, sensitivities of the dosimeters were lower than 0.04 ΔOD/Gy, and OD deviations at the same dose were larger than 6%.ConclusionsAt room temperature, PRESAGEREU dosimeters could be used for dose measurement only for up to two dose measurement sessions. At low temperatures, usage of PRESAGEREU dosimeters for dose measurement seems to be possible from the 3rd irradiation. When reusing PRESAGEREU dosimeters, the OD curve should be re-defined for every measurement session because the shape of this curve depends on the irradiation history.

Highlights

Intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) can deliver prescription doses to target volumes while minimizing doses to radiosensitive organs at risk (OARs) located near the target volumes [1, 2]
Optical density (OD) was assessed using optical computed tomography (CT) scanning. Considering both linearity and sensitivity of the optical density (OD) curves, R2 above 0.95 and sensitivity above 0.04 ΔOD/Gy were observed at the 1st irradiation and 2nd irradiation for the RT group
Considering the reproducibility of signals in response to the same dose, dosimeters in the RT group showed average deviations among dosimeters less than 5%, while for dosimeters in the LT group showed average deviations among dosimeters less than 6%

Summary

Introduction

Intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) can deliver prescription doses to target volumes while minimizing doses to radiosensitive organs at risk (OARs) located near the target volumes [1, 2]. IMRT and VMAT are more susceptible to errors because those techniques generally generate steep dose gradients near the target volumes [3, 4]. In this respect, pre-treatment patient-specific quality assurance (QA) for both IMRT and VMAT is highly recommended and routinely performed in the clinical setting [3, 4]. Pre-treatment QA typically involves the measurement of a planar dose map of some kind, followed by twodimensional (2D) gamma evaluation [5]

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