An anthropomorphic abdominal phantom for deformable image registration accuracy validation in adaptive radiation therapy

Liao, Yun; Wang, Linjing; Xu, Xiangdong; Chen, Haibin; Chen, Jiawei; Zhang, Guoqian; Lei, Huaiyu; Wang, Ruihao; Zhang, Shuxu; Gu, Xuejun; Zhen, Xin; Zhou, Linghong

doi:10.1002/mp.12229

Cited by 29 publications

(26 citation statements)

References 44 publications

(91 reference statements)

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Section: Discussionmentioning

confidence: 99%

“…Various studies have used PVC‐based materials for phantoms construction . A PVC‐based abdominal deformable phantom was made to evaluate the accuracy of deformable registration and dose accumulation in radiotherapy . One deformable prostate phantom based on different ratios of PVC‐softener mixtures was constructed for multimodal imaging, such as ultrasound, CT, and MRI .…”

Section: Discussionmentioning

confidence: 99%

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Characterizing mechanical and medical imaging properties of polyvinyl chloride‐based tissue‐mimicking materials

Qin

Dyer

et al. 2019

J Applied Clin Med Phys

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Polyvinyl chloride (PVC) is a commonly used tissue‐mimicking material (TMM) for phantom construction using 3D printing technology. PVC‐based TMMs consist of a mixture of PVC powder and dioctyl terephthalate as a softener. In order to allow the clinical use of a PVC‐based phantom use across CT and magnetic resonance imaging (MRI) imaging platforms, we evaluated the mechanical and physical imaging characteristics of ten PVC samples. The samples were made with different PVC‐softener ratios to optimize phantom bioequivalence with physiologic human tissue. Phantom imaging characteristics, including computed tomography (CT) number, MRI relaxation time, and mechanical properties (e.g., Poisson’s ratio and elastic modulus) were quantified. CT number varied over a range of approximately −10 to 110 HU. The relaxation times of the T1‐weighted and T2‐weighted images were 206.81 ± 17.50 and 20.22 ± 5.74 ms, respectively. Tensile testing was performed to evaluate mechanical properties on the three PVC samples that were closest to human tissue. The elastic moduli for these samples ranged 7.000–12.376 MPa, and Poisson’s ratios were 0.604–0.644. After physical and imaging characterization of the various PVC‐based phantoms, we successfully produced a bioequivalent phantom compatible with multimodal imaging platforms for machine calibration and image optimization/benchmarking. By combining PVC with 3D printing technologies, it is possible to construct imaging phantoms simulating human anatomies with tissue equivalency.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Characterizing mechanical and medical imaging properties of polyvinyl chloride‐based tissue‐mimicking materials

Qin

Dyer

et al. 2019

J Applied Clin Med Phys

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“…Also, no dosimetry systems are included to the phantom. Another abdominal phantom presented by Liao et al . features multiple deformable abdominal organs made of polyvinyl chloride and rigid vertebras.…”

Section: Discussionmentioning

confidence: 99%

“…Also, no dosimetry systems are included to the phantom. Another abdominal phantom presented by Liao et al 33 features multiple deformable abdominal organs made of polyvinyl chloride and rigid vertebras. This phantom is able to accommodate the inclusion of a pair of ionization chambers for point dose measurements as an embedded dosimetry system.…”

Section: Discussionmentioning

confidence: 99%

ELPHA: Dynamically deformable liver phantom for real‐time motion‐adaptive radiotherapy treatments

et al. 2019

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Purpose Real‐time motion‐adaptive radiotherapy of intrahepatic tumors needs to account for motion and deformations of the liver and the target location within. Phantoms representative of anatomical deformations are required to investigate and improve dynamic treatments. A deformable phantom capable of testing motion detection and motion mitigation techniques is presented here. Methods The dynamically dEformable Liver PHAntom (ELPHA) was designed to fulfill three main constraints: First, a reproducibly deformable anatomy is required. Second, the phantom should provide multimodality imaging contrast for motion detection. Third, a time‐resolved dosimetry system to measure temporal effects should be provided. An artificial liver with vasculature was casted from soft silicone mixtures. The silicones allow for deformation and radiographic image contrast, while added cellulose provides ultrasonic contrast. An actuator was used for compressing the liver in the inferior direction according to a prescribed respiratory motion trace. Electromagnetic (EM) transponders integrated in ELPHA help provide ground truth motion traces. They were used to quantify the motion reproducibility of the phantom and to validate motion detection based on ultrasound imaging. A two‐dimensional ultrasound probe was used to follow the position of the vessels with a template‐matching algorithm. This detected vessel motion was compared to the EM transponder signal by calculating the root‐mean‐square error (RMSE). ELPHA was then used to investigate the dose deposition of dynamic treatment deliveries. Two dosimetry systems, radio‐chromic film and plastic scintillation dosimeters (PSD), were integrated in ELPHA. The PSD allow for time‐resolved measurement of the delivered dose, which was compared to a time‐resolved dose of the treatment planning system. Film and PSD were used to investigate dose delivery to the deforming phantom without motion compensation and with treatment‐couch tracking for motion compensation. Results ELPHA showed densities of 66 and 45 HU in the liver and the surrounding tissues. A high motion reproducibility with a submillimeter RMSE (<0.32 mm) was measured. The motion of the vasculature detected with ultrasound agreed well with the EM transponder position (RMSE < 1 mm). A time‐resolved dosimetry system with a 1 Hz time resolution was achieved with the PSD. The agreement of the planned and measured dose to the PSD decreased with increasing motion amplitude: A dosimetric RMSE of 1.2, 2.1, and 2.7 cGy/s was measured for motion amplitudes of 8, 16, and 24 mm, respectively. With couch tracking as motion compensation, these values decreased to 1.1, 1.4, and 1.4 cGy/s. This is closer to the static situation with 0.7 cGy/s. Film measurements showed that couch tracking was able to compensate for motion with a mean target dose within 5% of the static situation (−5% to +1%), which was higher than in the uncompensated cases (−41% to −1%). Conclusions ELPHA is a deformable liver phantom with high motion reproducibility. It was demonstrated t...

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“…PVCP has been used in previously published work as a material for developing deformable multimodal anthropomorphic phantoms, and has been shown to have mechanical properties similar to those of porcine abdominal organs. [27][28][29][30] During the heating of the liquid PVCP, additives were used to change the physical properties of the material. The addition of a hardener or softener increased or decreased the density of the PVCP, which modified the computed tomography (CT) and MRI properties of the material.…”

Section: A | Deformable Abdominal Phantom Developmentmentioning

confidence: 99%

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

Matrosic

Hull

Palmer

et al. 2019

J Applied Clin Med Phys

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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.

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An anthropomorphic abdominal phantom for deformable image registration accuracy validation in adaptive radiation therapy

Abstract: We have designed and constructed an anthropomorphic abdominal deformable phantom with satisfactory elastic property, realistic organ density, and anatomy. This physical phantom can be used for routine validations of DIR geometric accuracy and dose accumulation accuracy in ART.

Cited by 29 publications

References 44 publications

Characterizing mechanical and medical imaging properties of polyvinyl chloride‐based tissue‐mimicking materials

Characterizing mechanical and medical imaging properties of polyvinyl chloride‐based tissue‐mimicking materials

ELPHA: Dynamically deformable liver phantom for real‐time motion‐adaptive radiotherapy treatments

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

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