Quality assurance of magnetic resonance imaging for a polymer gel dosimeter using a 3D-printed phantom

Quality assurance (QA) of magnetic resonance imaging (MRI) for gel dosimetry using an in-house phantom was established to ensure consistent dosimetric performance. A normoxic N-vinylpyrrolidone-based gel dosimeter sensitized with an inorganic salt was used. Each individual gel dosimeter, in addition to a specially designed image QA phantom, was imaged at three institutions with different MRI systems. Both the gel dosimeter and QA phantom had linear dose–response curves at all institutions, with correlation coefficients = 1.00 and ≥ 0.99, respectively. Minor inter-institutional variations in the sensitivity (gel dosimeter, 0.096 ± 0.010 s−1Gy−1; QA phantom, 0.140 ± 0.003 s−1Gy−1) and offset value (gel dosimeter, 2.188 ± 0.222 s−1; QA phantom, 3.318 ± 0.081 s−1) were found. Dose uncertainties for the gel dosimeter ranged from 3.2% to 3.5% at 10 Gy and 1.7%–2.1% at 20 Gy, and these were comparable with the corresponding QA phantom uncertainties. Dose resolutions were 0.8–1.2 Gy for the gel dosimeter and 0.6–1.4 Gy for the QA phantom. Uniformity factors were ≥98% at all institutions. Spatial linearity had a geometric distortion ≤1.0%, Gamma passing rates of 95%–100% met recommended QA guidelines; strong correlations between the QA phantom and gel dosimeter were also obtained for each of these measures. Our study demonstrates the viability of applying MRI acquisition parameters validated using a QA phantom to polymer gel dosimetry across diverse MRI systems. This approach enables robust QA measures, focusing on effective management of uniformity and dose uncertainty. •Developed a novel QA method for MR imaging of gel dosimeters.•Designed and produced an in-house 3D-printed QA phantom for imaging tests.•Conducted gel dosimeter scans at three different institutions using various MRI systems.•Established a strong correlation between the image quality measures of the QA phantom and the gel dosimeter.•Emphasized the critical need to control image uniformity and dose uncertainty for accurate dosimetry.