Deformable abdominal phantom for the validation of real‐time image guidance and deformable dose accumulation

Abstract

Purpose End‐to‐end testing with quality assurance (QA) phantoms for deformable dose accumulation and real‐time image‐guided radiotherapy (IGRT) has recently been recommended by American Association of Physicists in Medicine (AAPM) Task Groups 132 and 76. The goal of this work was to develop a deformable abdominal phantom containing a deformable three‐dimensional dosimeter that could provide robust testing of these systems. Methods The deformable abdominal phantom was fabricated from polyvinyl chloride plastisol and phantom motion was simulated with a programmable motion stage and plunger. A deformable normoxic polyacrylamide gel (nPAG) dosimeter was incorporated into the phantom apparatus to represent a liver tumor. Dosimeter data were acquired using magnetic resonance imaging (MRI). Static measurements were compared to planned dose distributions. Static and dynamic deformations were used to simulate inter‐ and intrafractional motion in the phantom and measurements were compared to baseline measurements. Results The statically irradiated dosimeters matched the planned dose distribution with an average γ pass rates of 97.0 ± 0.5% and 97.5 ± 0.2% for 3%/5 mm and 5%/5 mm criteria, respectively. Static deformations caused measured dose distribution shifts toward the phantom plunger. During the dynamic deformation experiment, the dosimeter that utilized beam gating showed an improvement in the γ pass rate compared to the dosimeter that did not. Conclusions A deformable abdominal phantom apparatus which incorporates a deformable nPAG dosimeter was developed to test real‐time IGRT systems and deformable dose accumulation algorithms. This apparatus was used to benchmark simple static irradiations in which it was found that measurements match well to the planned distributions. Deformable dose accumulation could be tested by directly measuring the shifts and blurring of the target dose due to interfractional organ deformation and motion. Dosimetric improvements were achieved from the motion management during intrafractional motion.

Evaluation of a commercial deformable image registration algorithm for dual‐energy CT processing

“…1). 12 The phantom was deformed using a programmable motion stage with a piston attached to contact the inferior end of the phantom using a rectangular block of acrylic [Fig. 1(a)].…”

Dosimetric characterization of double network Fricke hydrogel based on PVA-GTA and phenylalanine peptide derivative

“…Imageguided radiation therapy may significantly improve the precision of such treatments by using different imaging systems to reduce inter-fractional and intra-fractional motion uncertainties. The clinical implementation of motion management systems requires that they first be validated through robust tests and measurements [10,11]. To this aim, phantoms containing dosimetric materials able not only to accurately measure 3D dose distributions, but also to mimic the deformation and motion of organs are required [12,13].…”

Deformable scintillation dosimeter: II. Real-time simultaneous measurements of dose and tracking of deformation vector fields

“…Deformable dosimetric gels have shown potential in measuring three-dimensional dose distributions delivered to deformable targets (Niu et al 2012, Deene et al 2015, Matrosic et al 2019. These water-equivalent gels demonstrated robust reproducibility and spatial resolution up to 1 mm (Juang et al 2013).…”