Dose verification of a clinical intensity-modulated radiation therapy eye case by the magnetic resonance imaging of N-isopropylacrylamide gel dosimeters

• Published in: Radiation physics and chemistry (Oxford, England : 1993) Vol. 104; pp. 188 - 191
• Main Authors: Chen, Yen-Li, Hsieh, Bor-Tsung, Chiang, Chih-Ming, Shih, Cheng-Ting, Cheng, Kai-Yuan, Hsieh, Ling-Ling
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.11.2014
• Subjects: Dosage; Dosimeters; Gamma analysis; IMRT; Magnetic resonance imaging; MRI; NIPAM; Planes; Radiation therapy; Three dimensional; Gamma analysis; IMRT; NIPAM; MRI
• ISSN: 0969-806X; 1879-0895
• DOI: 10.1016/j.radphyschem.2013.12.037

In this study, N-isopropylacrylamide (NIPAM) polymer gel, together with magnetic resonance imaging (MRI), was used to measure the relative three-dimensional (3D) dose distribution of an intensity-modulated radiation therapy (IMRT) eye case. The gels were enclosed in cylindrical acrylic vessels with 10cm outer diameter and 10cm length. The gels were subsequently irradiated by delivering 5Gy of a prescribed dose with a 6MV linear accelerator using five fields. The 3D maps of the proton relaxation rate R2 were obtained using a 1.5T MRI system correlated with the dose. The treatment planning system (TPS) data and NIPAM gel dosimeter data were compared with the experimental results in the form of relative dose distributions, including isodose curves, dose profiles, and gamma index maps. Results indicated that the linear relationship of the R2—dose for NIPAM gel dosimeters reached 0.999 within the dose range of 0Gy to 12Gy. Comparison of planar dose distributions among the gel dosimeters and TPS showed that the isodose lines corresponded to selected planes in the axial plane. For the 50% to 110% dose analysis, the maximum dose differences varied from 4.04% to 13.53%. Gamma evaluation of the planar dose profile resulted in pass rates of 96.84%, 83.16%, and 53.42% when the acceptance criteria of 3%/3mm, 2%/2mm, and 1%/1mm, respectively, were used in the axial plane. Overall, the results showed that NIPAM polymer gel dosimeters can serve as a high-resolution, accurate, 3D tool for IMRT dose distribution verification. •3D dose distribution of irradiated NIPAM gels.•High-resolution, accurate, 3D tool for IMRT dose distribution verification.•Study the dosimetric characteristics of NIPAM gels in conjunction with MRI.