Work

Characterization of Fricke–xylenol orange–Pluronic gel dosimeters for end-to-end three-dimensional radiotherapy dosimetric quality assurance

Year: 2026

Type: article

Abstract: Objective. Fricke–xylenol orange (XO)–Pluronic F-127 (FXP) gels have demonstrated favourable dosimetric properties, but their investigation has hitherto been limited to small sample volumes. This study characterized large-volume FXP gel dosimeters combined with optical computed tomography (OCT) readout for three-dimensional (3D) 6 MV radiotherapy dosimetry measurements. Approach. An FXP gel formulation proposed in the literature (25% w/w Pluronic F-127, 0.165 mM XO, 0.5 mM FAS, 50 mM H 2 SO 4 ) and two reduced XO formulations (0.08 mM and 0.04 mM) were investigated using OCT readout at 589 nm and 633 nm. The effects of XO concentration and scanning wavelength on dose sensitivity, dose resolution, and [XO–Fe] 3+ ion diffusion were evaluated. Main results. All FXP formulations exhibited linear dose–response behaviour over the studied dose range of 0.2–4.15 Gy. OCT readout at 589 nm provided higher dose sensitivity but was associated with increased optical attenuation and ring artefacts. Reducing the XO concentration to 0.08 mM preserved dose sensitivity, whereas further reduction to 0.04 mM resulted in reduced sensitivity without a noticeable impact on imaging artefacts. OCT readout at 633 nm mitigated imaging artefacts at the expense of dose sensitivity, while achieving dose resolutions below 5% at doses above 1.5 Gy (95% confidence level). The diffusion of [XO–Fe] 3+ ions was found to decrease with increasing XO concentration and to be anisotropic with respect to gravity, supporting a post-irradiation readout time window of 60–120 min to limit spatial blurring. An optimized FXP–OCT configuration employing 0.08 mM XO, a 633 nm scanning wavelength, and readout at 60 min post irradiation, was applied to an end-to-end (E2E) radiotherapy quality assurance (QA) protocol. Results exhibited good agreement with treatment planning system calculations for an intracranial stereotactic radiotherapy plan, with a 3D global gamma index passing rate of 96% (3%/2 mm criteria). Significance . These findings support the feasibility of large-volume FXP gel dosimetry for E2E dosimetric QA in complex radiotherapy applications.

Source: Physics in Medicine and Biology

DOI: 10.1088/1361-6560/ae7ec5