Gomez Gorka, Baeza Montserrat, Mateos Juan Carlos, Rivas Jose Antonio, Simon Florencio Javier Luis, Ortega Diego Mesta, de Los Ángeles Flores Carrión María, Del Campo Eleonor Rivin, Gómez-Cía Tomas, Guerra Jose Luis Lopez
Biomedical Informatics, Biomedical Engineering and Health Economy, Institute of Biomedicine of Seville (IBIS)/Virgen del Rocío University Hospital/CSIC/University of Seville, Seville, Spain.
Radiation Physics, University Hospital Virgen del Rocio, Seville, Spain.
Rep Pract Oncol Radiother. 2021 Apr 14;26(2):211-217. doi: 10.5603/RPOR.a2021.0030. eCollection 2021.
The skin-sparing effect of megavoltage-photon beams in radiotherapy (RT) reduces the target coverage of superficial tumours. Consequently, a bolus is widely used to enhance the target coverage for superficial targets. This study evaluates a three-dimensional (3D)-printed customized bolus for a very irregular surface, the outer ear.
We fabricated a bolus using a computed tomography (CT) scanner and evaluated its efficacy. The head of an Alderson Rando phantom was scanned with a CT scanner. Two 3D boluses of 5- and 10-mm thickness were designed to fit on the surface of the ear. They were printed by the Stratasys Objet260 Connex3 using the malleable "rubber-like" photopolymer Agilus. CT simulations of the Rando phantom with and without the 3D and commercial high density boluses were performed to evaluate the dosimetric properties of the 3D bolus. The prescription dose to the outer ear was 50 Gy at 2 Gy/fraction.
We observed that the target coverage was slightly better with the 3D bolus of 10mm compared with the commercial one (D 98.2% . 97.6%).The maximum dose was reduced by 6.6% with the 3D bolus and the minimum dose increased by 5.2% when comparing with the commercial bolus. In addition, the homogeneity index was better for the 3D bolus (0.041 . 0.073).
We successfully fabricated a customized 3D bolus for a very irregular surface. The target coverage and dosimetric parameters were at least comparable with a commercial bolus. Thus, the use of malleable materials can be considered for the fabrication of customized boluses in cases with complex anatomy.
在放射治疗（RT）中，兆伏级光子束的皮肤保护效应会降低浅表肿瘤的靶区覆盖范围。因此，补偿物被广泛用于提高浅表靶区的靶区覆盖。本研究评估了一种用于非常不规则表面（外耳）的三维（3D）打印定制补偿物。
我们使用计算机断层扫描（CT）扫描仪制作了一个补偿物并评估其效果。使用CT扫描仪对Alderson Rando人体模型的头部进行扫描。设计了两个厚度分别为5毫米和10毫米的3D补偿物，以贴合耳朵表面。它们由Stratasys Objet260 Connex3使用可延展的“橡胶状”光聚合物Agilus打印而成。对带有和不带有3D及商业高密度补偿物的Rando人体模型进行CT模拟，以评估3D补偿物的剂量学特性。外耳的处方剂量为50 Gy，分2 Gy/次。
我们观察到，与商业补偿物相比，10毫米厚的3D补偿物的靶区覆盖略好（D98.2%. 97.6%）。与商业补偿物相比，3D补偿物使最大剂量降低了6.6%，最小剂量增加了5.2%。此外，3D补偿物的均匀性指数更好（0.041. 0.073）。
我们成功为非常不规则的表面制作了定制的3D补偿物。靶区覆盖和剂量学参数至少与商业补偿物相当。因此，在解剖结构复杂的情况下，可考虑使用可延展材料制作定制补偿物。
