Abstract
During the procedure of radiotherapy for superficial tumors, the key to treatment is to ensure that the skin surface receives an adequate radiation dose. However, due to the presence of the built-up effect of high-energy rays, equivalent tissue compensators (boluses) with appropriate thickness should be placed on the skin surface to increase the target radiation dose. Traditional boluses do not usually fit the skin perfectly. Wet gauze is variable in thickness day to day which results in air gaps between the skin and the bolus. These unwanted but avoidable air gaps lead to a decrease of the radiation dose in the target area and can have a poor effect on the outcome. Three-dimensional (3D) printing, a new rising technology named “additive manufacturing” (AM), could create physical models with specific shapes from digital information by using special materials. It has been favored in many fields because of its advantages, including less waste, low-cost, and individualized design. It is not an exception in the field of radiotherapy, personalized boluses made through 3D printing technology also make up for a number of shortcomings of the traditional commercial bolus. Therefore, an increasing number of researchers have tried to use 3D-printed boluses for clinical applications rather than commercial boluses. Here, we review the 3D-printed bolus’s material selection and production process, its clinical applications, and potential radioactive dermatitis. Finally, we discuss some of the challenges that still need to be addressed with the 3D-printed boluses.
Highlights
The maximum radiation dose of high-energy external X-ray beams can be reached only after they enter the human tissue with a certain depth, which is known as the built-up effect or skin-sparing effect [1,2,3]
Maximum dose of the target volume; Dmin, minimum dose of the target volume; Dmean, mean dose of the target volume; D90%, the dose that covers 90% of the target volume; V90%, the target volume that receives over the 90% of the prescribed dose; HI, dose homogeneity index; GTV, gross tumor volume; CTV, clinical target volume; PTV, planning target volume; OAR, organs at risk; %diff(the percentage difference), differences between calculated and measured doses at the surface were acquired to investigate the uncertainty of bolus structures. %diff=100x(measured dose-calculated dose)/calculated dose
Another application of the 3D-printed bolus in head and neck disease found that the maximum subcutaneous air gap was only 4 mm and the actual irradiation dose on the skin surface was only ±10 cGy different from the planned dose [23, 37]
Summary
Three-dimensional (3D) printing, a new rising technology named “additive manufacturing” (AM), could create physical models with specific shapes from digital information by using special materials. It has been favored in many fields because of its advantages, including less waste, low-cost, and individualized design. It is not an exception in the field of radiotherapy, personalized boluses made through 3D printing technology make up for a number of shortcomings of the traditional commercial bolus.
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