3D star shot analysis using MAGAT gel dosimeter for integrated imaging and radiation isocenter verification of MR‐Linac system

Abstract

This study aims to investigate a star shot analysis using a threedimensional (3D) gel dosimeter for the imaging and radiation isocenter verification of a magnetic resonance linear accelerator (MR-Linac). Methods: A mixture of methacrylic acid, gelatin, and tetrakis (hydroxymethyl) phosphonium chloride, called MAGAT gel, was fabricated. One MAGAT gel for each Linac and MR-Linac was irradiated under six gantry angles. A 6 MV photon beam of Linac and a 6 MV flattening filter free beam of MR-Linac were delivered to two MAGAT gels and EBT3 films. MR images were acquired by MR-Linac with a clinical sequence (i.e., TrueFISP). The 3D star shot analysis for seven consecutive slices of the MR images with TrueFISP was performed. The 2D star shot analysis for the central plane of the gel was compared to the results from the EBT3 films. The radius of isocircle (IC r ) and the distance between the center of the circle and the center marked on the image (IC d ) were evaluated. Results: For MR-Linac with MAGAT gel measurements, IC d at the central plane was 0.46 mm for TrueFISP. Compared to EBT3 film measurements, the differences in IC d and IC r for both Linac and MR-Linac were within 0.11 and 0.13 mm, respectively. For the 3D analysis, seven consecutive slices of TrueFISP images were analyzed and the maximum radii of isocircles (IC r_max ) were 0.18 mm for Linac and 0.73 mm for MR-Linac. The tilting angles of radiation axis were 0.31 • for Linac and 0.10 • for MR-Linac. Conclusion:The accuracy of 3D star shot analysis using MAGAT gel was comparable to that of EBT3 film, having a capability for integrated analysis for imaging isocenter and radiation isocenter.3D star shot analysis using MAGAT gel can provide 3D information of radiation isocenter, suggesting a quantitative extent of gantry-tilting.

3D Polymer Gel Dosimeters with iCBCT 3D Reading and polyGeVero-CT Software Package for Quality Assurance in Radiotherapy

“…In this way, 3D dosimeters can now be scanned without moving them after irradiation. Therefore, recent studies have shown that the NIPAM 3D dosimeter can be used with CBCT for 3D scanning [ 72 , 73 ], and for the same purpose, a combination of a 3D gel dosimeter with MRI can be used to determine the radiation isocenter using the PAGAT and MAGAT dosimeters using the star-shot irradiation pattern [ 74 , 75 , 76 , 77 ]. The KI-PVA radiochromic gel dosimeter combined with the Winston–Lutz test was also used to determine the isocenter [ 78 ].…”

Development of a radiation detector using a silicon photomultiplier and large Ce-doped Gd-Al-Ga-grant scintillator for gamma spectroscopy observations of radioactivation in a linear accelerator

“…Radiation therapy is a treatment that uses high doses of radiation to target and kill cancer cells, as well as shrink tumors [1]. In the United States, approximately 50% of cancer patients receive radiation therapy [2].…”

Feasibility of SiPM and CsI(Tl) based radiation detector with light guide for measurement of radioactivation in a linear accelerator

“…The goal of radiation therapy is to treat cancer while minimizing radiation exposure to healthy tissues. Accordingly, various techniques such as intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) have been developed to achieve this objective [3]. These advanced techniques allow for more precise and targeted delivery of radiation, improving the therapeutic outcome and reducing potential side effects on surrounding normal tissues [2,3].…”

“…Accordingly, various techniques such as intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) have been developed to achieve this objective [3]. These advanced techniques allow for more precise and targeted delivery of radiation, improving the therapeutic outcome and reducing potential side effects on surrounding normal tissues [2,3]. Indeed, these advanced techniques typically require a higher number of Monitor Units (MUs) compared to the traditional three-dimensional conformal radiation therapy (3D-CRT) [2].…”