The use of 3D printing within radiation therapy to improve bolus conformity: a literature review

Background and purpose In radiotherapy (RT) bolus material is used to increase skin dose and eliminate the ‘skin-sparing’ effect. Bolus fabrication is limited to the expertise of the practitioner and is time and resource intensive for both patients and staff to construct bolus. In addition, prefabricated bolus does not always conform to irregular surfaces resulting in variations to dose distribution at the skin surface. The purpose of this paper is to ascertain whether it is feasible to improve bolus conformity within radiation therapy by using a 3D printer to fabricate bolus. Method A literature review was conducted that utilised Boolean terminology and included keywords; (‘3d’ OR ‘3-dimensional’ OR ‘three dimensional’) ‘bolus’ OR ‘boli’ conform*, (‘Radiation therapy’ OR ‘radiotherapy’) Printing. Results Several key papers were identified and critically evaluated based of the title of the feasibility of improving bolus conformity with the used of 3D printing. Several fabrication material devices were explored. Findings The literature advocates that fused deposition modelling fabrication device clear polylactic acid material to be an adequate product to construct 3D printed bolus and conform to irregular surfaces. 3D bolus would prove advantageous for volumetric arc therapy/intensity modulated radiation therapy techniques as literature has shown the presence of air gaps, small field sizes and large beam obliquity can result in a >10% dose reduction at skin surface.