Three-dimensional Winston–Lutz test using reusable polyvinyl alcohol-iodide (PVA-I) radiochromic gel dosimeter

Abstract

Medical linear-accelerator-based stereotactic radiosurgery (SRS) using a stereotactic apparatus or image-guided radiotherapy system for intracranial lesions is performed widely in clinical practice. In general, Winston–Lutz (WL) tests using films or electric portal imaging devices (EPIDs) have been performed as pre-treatment and routine quality assurance (QA) for the abovementioned treatment. Two-dimensional displacements between the radiation isocentre and mechanical isocentre are analysed from the test; therefore, it is difficult to identify the three-dimensional (3D) isocentre position intuitively. In this study, we developed an innovative 3D WL test for SRS-QA using a novel radiochromic gel dosimeter based on a polyvinyl alcohol-iodide (PVA-I) complex that can be reused after annealing. A WL gel phantom that was consisted of the PVA-I gel dosimeter poured into a tall acrylic container and an embedded small tungsten sphere was used as a position detector. A flatbed scanner was used to analyse the isocentre position. The measured 3D isocentre accuracy from the gel-based WL test was within 0.1 mm compared with that obtained from the EPID-based WL test. Furthermore, excellent reusability of the WL gel phantom was observed in long-term SRS isocentre verification, in which clinical SRS cases involving repeated irradiation and annealing were analysed. These results demonstrate the high accuracy and reliable evaluation of the isocentre position using an innovative test. In addition, the clinical-based routine SRS-QA using the PVA-I gel dosimeter demonstrates a highly convenience while affording an easy and fast analysis process.

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

“…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]. Recent work has demonstrated the use of PABIG nx [18] and VIPAR nd (VIP) [79] for radiation isocenter determination with CBCT and iCBCT reading and data In the case of 3D dosimeter measurements using NMR, MRI, CT, OCT, or USG, they should be moved to another room after irradiation.…”

An Optical Reusable 2D Radiochromic Gel-Based System for Ionising Radiation Measurements in Radiotherapy

“…The data are processed using various software packages; for instance, for 2D calculations, myQA Machines (IBA, Schwarzenbruck, Germany), DoseLab (Varian, Palo Alto, CA, USA), FilmQA Pro™ (Ashland, Westmont, IL, USA), Mephisto (PTW, Freiburg, Germany), and polyGeVero-CT (v. 1.2, GeVero Co., Lodz, Poland), and for 3D calculations, polyGeVero-CT (v. 1.2, GeVero Co., Lodz, Poland) (Table 1). [25] All 2D and 3D dosimeters, such as film and gel dosimeters, rely on the radiationinduced responses of components sensitive to ionizing radiation. For instance, thin, flat 2D dosimeters (pos.…”

Whole Three-Dimensional Dosimetry of Carbon Ion Beams with an MRI-Based Nanocomposite Fricke Gel Dosimeter Using Rapid T1 Mapping Method

“…In recent years, gel dosimeters, which are chemical dosimeters, have been attracting significant attention as promising tools for measuring 3D dose distributions [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ]. Various forms of chemical dosimeters are used, such as the Fricke gel dosimeter [ 22 , 23 , 24 ], which uses the oxidation reaction of iron ions, and the polymer gel dosimeter [ 25 , 26 , 27 ], which uses radiation-induced polymerization in a monomer solution.…”