Technical note: Temporal and thermal stability of optical response for silicone-based 3D radiochromic dosimeters.

Abstract

Radiochromic silicone-based dosimeters are flexible 3D dosimeters, which at appropriate concentration of leucomalachite green (LMG) and curing agent are dose-rate independent for clinical photon beams. However, their dose response is based on chemical processes that can be influenced by temporal and thermal conditions, impacting measurement stability. The aim of this study was to investigate the temporal stability of the dose response of radiochromic dosimeters for different curing times and post-irradiation storage temperatures. Six cylindrical dosimeters (5cm diameter, 5cm length) were produced in a single batch and separated into two groups that were irradiated 72 and 118h after production. The same photon plan, consisting of two 10 × 1.6 cm2 opposing fields, was delivered to all dosimeters. After irradiation, the dosimeters were separated into three groups, stored at 5°C, 15°C, and 20°C, and read out for five consecutive days. Storage temperature influenced the measurement stability, and changes in the optical response with time differed between irradiated and non-irradiated parts of the dosimeters. The relative change between signal and background was greater than 10% for all measurements performed 24h or more after irradiation, except for dosimeters stored at 5°C, which changed by 2%-5% after 24h. The dosimeter temporal stability was not influenced by curing time. For room temperature storage (15°C and 20°C), readout should take place as soon as possible after irradiation since the background color increased rapidly for both curing times (72 and 118h), whereas the dosimeters are stored at 5°C, readout can be performed up to 24h after.