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REVIEW ARTICLE

3D Printing Polymer-based Bolus Used for

Radiotherapy

Ying Lu , Jianbo Song , Xiaohong Yao , Meiwen An *, Qinying Shi , Xiaobo Huang *
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1 Laboratory of Biomaterial Surface and Interface, School of Materials Science and Engineering, Taiyuan University of
Technology, Taiyuan 030024, Shanxi Province, China
2 Shanxi Bethune Hospital, Shanxi Academy of Medical Sciences, Taiyuan 030032, Shanxi Province, China
3 Institute of Applied Mechanics and Biomedical Engineering, Taiyuan University of Technology, Taiyuan 030024, Shanxi
Province, China
Abstract: Bolus is a kind of auxiliary device used in radiotherapy for the treatment of superficial lesions such as skin cancer.
It is commonly used to increase skin dose and overcome the skin-sparing effect. Despite the availability of various commercial
boluses, there is currently no bolus that can form full contact with irregular surface of patients’ skin, and incomplete contact
would result in air gaps. The resulting air gaps can reduce the surface radiation dose, leading to a discrepancy between the
delivered dose and planned dose. To avoid this limitation, the customized bolus processed by three-dimensional (3D) printing
holds tremendous potential for making radiotherapy more efficient than ever before. This review mainly summarized the recent
development of polymers used for processing bolus, 3D printing technologies suitable for polymers, and customization of 3D
printing bolus. An ideal material for customizing bolus should not only have the feature of 3D printability for customization, but
also possess radiotherapy adjuvant performance as well as other multiple compound properties, including tissue equivalence,
biocompatibility, antibacterial activity, and antiphlogosis.
Keywords: Radiotherapy; Bolus; 3D printing; Soft polymers; Hydrogel

*Correspondence to: Xiaobo, Huang, Laboratory of Biomaterial Surface and Interface, School of Materials Science and Engineering, Taiyuan
University of Technology, Taiyuan 030024, Shanxi Province, China; huangtyut@163.com
Received: June 15, 2021; Accepted: July 21, 2021; Published Online: September 22, 2021

Citation: Lu Y, Song J, Yao X, et al., 2021, 3D Printing Polymer-based Bolus Used for Radiotherapy. Int J Bioprint, 7(4):414.
http://doi.org/10.18063/ijb.v7i4.414

1. Introduction receive a sufficient dose. To solve this problem, a build-
up material called bolus, is often placed on the surface of
Radiotherapy is an effective way used for the treatment of the skin to maximize the radiation dose of subcutaneous
tumors, especially in areas where surgery is not possible. tissues so as to achieve the desired dose at target position
Almost half of cancer patients receive radiotherapy while reducing the dose in deep tissues . Bolus acts as a
[3]
at certain point of treatment . To provide a sufficient layer of skin tissues to provide a more effective treatment
[1]
radiation dose to the tumor, the types of radiation that to the superficial lesions (Figure 1).
[4]
target tumor location should be selected. Conventionally, Despite the availability of commercial bolus, there
electron is used to kill tumors of superficial lesions, such are still some problems with bolus during radiotherapy.
as breast cancer, skin cancer, and nasopharyngeal cancer; Most commercial boluses are in a flaky structure that
however, the dose distribution is inhomogeneous and the does not form adequate contact with the irregular surface
target coverage is inadequate. It is widely recommended of patients’ skin, such as the ear, nose, and scalp, resulting
that the target area should receive at least 95% of the in air gaps between the bolus and the irregular skin . The
[5]
predesigned dose when administering radiotherapy . resulting air gap is very harmful to obtaining the expected
[2]
However, because of the skin sparing effect of high- distribution of radiation dose at planning target volume
energy photon beams, the superficial lesions cannot (PTV) for achieving a desired therapeutic outcome . The
[6]
© 2021 Lu, et al., This is an Open Access article distributed under the terms of the Creative Commons Attribution License, permitting distribution and
reproduction in any medium, provided the original work is cited.
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