Prog Med Phys.  2019 Mar;30(1):32-38. 10.14316/pmp.2019.30.1.32.

Geometric Evaluation of Patient-Specific 3D Bolus from 3D Printed Mold and Casting Method for Radiation Therapy

• An HJ
• Kim MS
• Kim J
• Son J
• Choi CH
• Park JM
• Kim JI

• KMID: 2442419
• DOI: http://doi.org/10.14316/pmp.2019.30.1.32

Abstract

PURPOSE
The objective of this study is to evaluate the geometrical accuracy of a patient-specific bolus based on a three-dimensional (3D) printed mold and casting method.
MATERIALS AND METHODS
Three breast cancer patients undergoing treatment for a superficial region were scanned using computed tomography (CT) and a designed bolus structure through a treatment planning system (TPS). For the fabrication of patient-specific bolus, we cast harmless certified silicone into 3D printed molds. The produced bolus was also imaged using CT under the same conditions as the patient CT to acquire its geometrical shape. We compared the shapes of the produced bolus with the planned bolus structure from the TPS by measuring the average distance between two structures after a surface registration.
RESULTS
AND CONCLUSIONS: The result of the average difference in distance was within 1 mm and, as the worst case, the absolute difference did not exceed ±2 mm. The result of the geometric difference in the cross-section profile of each bolus was approximately 1 mm, which is a similar property of the average difference in distance. This discrepancy was negligible in affecting the dose reduction. The proposed fabrication of patient-specific bolus is useful for radiation therapy in the treatment of superficial regions, particularly those with an irregular shape.

Keyword

Bolus; Patient specific bolus; 3D printing; Dose build up; Geometric analysis

MeSH Terms

Breast Neoplasms
Fungi*
Humans
Methods*
Printing, Three-Dimensional
Silicon
Silicones
Silicon
Silicones

Figure

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  Fig. 1 (a) Transaxial view of patient CT and designed bolus and (b) volume rendering of designed bolus.

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  Fig. 2 Overall fabrication process of bolus.

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  Fig. 3 (a) 3D printed bolus molds with body and lid part, and (b) produced patient-specific bolus.

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  Fig. 4 (a) Planned bolus structure from TPS, (b) measured fabricated bolus structure, (c) superimposed structures after registration, and (d) color map of difference in distance between two structures.

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  Fig. 5 Difference in distance of registered structure surface.

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  Fig. 6 Equal spacing interval cross-section profile map.

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