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

Purpose Quality assurance (QA) of magnetic resonance imaging (MRI) for gel dosimetry using an in-house phantom was established to ensure consistent dosimetric performance. Methods 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. Results 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(-1)Gy(-1); QA phantom, 0.140 +/- 0.003 s(-1)Gy(-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. Conclusion 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.