Prog Med Phys.  2021 Dec;32(4):99-106. 10.14316/pmp.2021.32.4.99.

Dosimetric Study Using Patient-Specific ThreeDimensional-Printed Head Phantom with Polymer Gel in Radiation Therapy

• Choi Y
• Chun KJ
• Kim ES
• Jang YJ
• Park JA
• Kim KB
• Kim GH
• Choi SH

• KMID: 2524155
• DOI: http://doi.org/10.14316/pmp.2021.32.4.99

Abstract

Purpose
In this study, we aimed to manufacture a patient-specific gel phantom combining threedimensional (3D) printing and polymer gel and evaluate the radiation dose and dose profile using gel dosimetry.
Methods
The patient-specific head phantom was manufactured based on the patient’s computed tomography (CT) scan data to create an anatomically replicated phantom; this was then produced using a ColorJet 3D printer. A 3D polymer gel dosimeter called RTgel-100 is contained inside the 3D printing head phantom, and irradiation was performed using a 6 MV LINAC (Varian Clinac) X-ray beam, a linear accelerator for treatment. The irradiated phantom was scanned using magnetic resonance imaging (Siemens) with a magnetic field of 3 Tesla (3T) of the Korea Institute of Nuclear Medicine, and then compared the irradiated head phantom with the dose calculated by the patient's treatment planning system (TPS).
Results
The comparison between the Hounsfield unit (HU) values of the CT image of the patient and those of the phantom revealed that they were almost similar. The electron density value of the patient’s bone and brain was 996±167 HU and 58±15 HU, respectively, and that of the head phantom bone and brain material was 986±25 HU and 45±17 HU, respectively. The comparison of the data of TPS and 3D gel revealed that the difference in gamma index was 2%/2 mm and the passing rate was within 95%.
Conclusions
3D printing allows us to manufacture variable density phantoms for patient-specific dosimetric quality assurance (DQA), develop a customized body phantom of the patient in the future, and perform a patient-specific dosimetry with film, ion chamber, gel, and so on.

Keyword

Polymer gel; Computed tomography; Magnetic resonance imaging; Treatment planning system; 3D printing

Figure

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  Fig. 1 (a, b) Manufacture of head phantom filled with a polymer gel.

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  Fig. 2 (a) Computed tomography (CT) scan of the actual patient. (b) CT scan of the three-dimensional-printed head phantom.

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  Fig. 3 Position alignment for magnetic resonance imaging (MRI) scans. Gel phantom scan image of the patient using MRI.

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  Fig. 4 (a) MRI image and treatment plan for high dose. (b) MRI image and treatment plan for low dose. MRI, magnetic resonance imaging; TPS, treatment planning system.

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  Fig. 5 (a) Dose profile in the x-axis direction of the coronal plane (T2 maps of the investigated phantom). The high-dose area is the dark area. (b) Dose profile in the y-direction of the coronal plane. (c) Dose profile in the x-direction of the transverse plane. (d) Dose profile in the y-axis direction of the transverse plane.

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  Fig. 6 Comparisons between one-dimensional (1D) profile and 1D gamma index values of the calculated (TPS) and measured doses: (a) x-axis direction of the coronal plane; (b) y-axis direction of the coronal plane; (c) x-axis direction of the transverse plane; (d) y-axis direction of the transverse plane. TPS, treatment planning system.

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  Fig. 7 Dose-volume histograms in (a) GTV and (b) PTV. GTV, gross tumor volume; PTV, planning target volume; TPS, treatment planning system.

Reference

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