Fast Isocenter Determination Using 3D Polymer Gel Dosimetry with Kilovoltage Cone-Beam CT Reading and the PolyGeVero-CT Software Package for Linac Quality Assurance in Radiotherapy

Abstract

This work presents an approach to the fast determination of a medical accelerator irradiation isocenter as a quality assurance (QA) procedure in radiotherapy. The isocenter determination tool is the tissue equivalent high-resolution 3D polymer gel dosimeter (PABIGnx) in a dedicated container combined with kilovoltage imaging systems and the polyGeVero-CT software package (v. 1.2, GeVero Co., Poland). Two accelerators were employed: Halcyon and TrueBeam (Varian, USA), both equipped with cone beam computed tomography (CBCT) and iterative reconstruction CBCT (iCBCT) algorithms. The scope of this work includes: (i) the examination of factors influencing image quality (reconstruction algorithms and modes), radiation field parameters (dose and multi-leaf collimator (MLC) gaps), fiducial markers, signal averaging for reconstruction algorithms and the scanning time interval between consecutive scans, (ii) the examination of factors influencing the isocenter determination, image processing (signal averaging, background subtraction, image filtering) and (iii) an isocenter determination report using a 2D and 3D approach. An optimized protocol and isocenter determination conditions were found. The time and effort required to determine the isocenter are discussed.

Validation of complex radiotherapy techniques using polymer gel dosimetry

“…For this, De Deene (2010) provided detailed descriptions and recommendations on the MR-scanning procedure of polymer gels. As further examples, Elter et al (2021a) and Maras and Kozicki (2022) have provided detailed protocols for the PAGAT and PABIG nx dosimetry gels, respectively. In addition, several commercial (Kozicki et al 2014, Kozicki andMaras 2015), freely available (Elter et al 2021a) and open source-based (Alexander et al 2015) software packages for the evaluation of PG measurements have been developed and validated for different evaluation methods (Alexander et al 2015, Gharehaghaji and Dadgar 2018, Tajaldeen and Alghamdi 2019, Elter et al 2019b, Elter et al 2021b.…”

“…BAREX TM , VELOX GmbH, Hamburg, Germany), which have been shown to be compatible with the PG (Haraldsson et al 2000, Mann et al 2017b. As an alternative, PMMA may be used (Maras and Kozicki 2022), which can be easily processed. For PMMA, however, the container wall has to be thick enough to seal the PG against oxygen from the outside, and even if this is assured, small amounts of oxygen dissolved within the PMMA may still alter the PG response in regions close to the container wall.…”

“…It was further shown that the NIPAM gel may be evaluated with onboard kV-CBCT (figure2) within a time frame suitable for clinical applications (<30 min)(Adamson et al 2019), and thus may be used for a radiation and imaging isocenter verification with a geometric accuracy in the submilimeter range(Pant et al 2020). The mean displacement of each beam from the imaging isocenter was below 0.6 ± 0.3 mm Maras and Kozicki (2022). developed and optimized a method to determine the isocenter at two linacs with a PABIG nx gel in 2D and 3D by means of a kV-CBCT.…”

First Combined, Double‐Density LCV‐Pluronic F‐127 Radiochromic Dosimeter Mimicking Lungs and Muscles

“…[ 1 ] Further research concerned both Fricke‐gel dosimeters and other systems, such as polymer gel dosimeters, radiochromic gel and plastic dosimeters, and flexible dosimeters. [ 2–59 ] Many dosimetric compositions have been proposed. As a general rule, each new 3D dosimeter has a specific acronym, usually derived from its components.…”

“…As a general rule, each new 3D dosimeter has a specific acronym, usually derived from its components. Examples of 3D polymer gel dosimeters are as follows (the acronyms are associated with example references): BANG, [16] PAG, [17] PAGAT, [18] nMAG, nPAG, [19] MAGIC, [17,20] MAGIC-f, [21] NIPAM, [22,23] VIPAR, [24] VIP (VIPAR nd ), [25] VIC, [26] VIC-T, [26] VIP3-Pluronic F-127, [27,28] PAGAT2-Pluronic F-127, [29] PAB-IG nx , [14,30,31] NHMAGAT, [32] MAGADIT, [33] NMPAGAT. [34] Examples of 3D radiochromic dosimeters are as follows: PVA-GTA-XO-Fricke, [35,36] PVA-GTA-MTB-Fricke, [37] Fricke-XOgelatine, [38] Fricke-XO-Pluronic F-127, [10,13,39] TTC-Pluronic F-127, [40] NBT-Pluronic F-127, [41,42] KI-PVA, [43] KI-Pluronic F-127, [12] LCV-gelatine; [44] and 3D plastic radiochromic dosimeter: PRESAGE.…”