Design and Feasibility of 3D Printed Tissue Compensators for Postmastectomy Radiation Therapy

Abstract

Postmastectomy radiation therapy (PMRT) is difficult to design and deliver due to heterogeneous tissue types and thickness in the chest wall area, as well as proximal organs at risk including the lungs and heart. A potential solution to simplify treatments and improve dose distributions is to use tissue compensators that effectively even out the desired treatment area, allowing the use of simple plans comprised of a single electron field. Design algorithms for such compensators are not generally available, and the fabrication of personalized compensators is difficult and expensive. In this work, we created and tested an algorithm that could calculate optimal compensator shapes, and then export those shapes to be 3D printed in-house and inexpensively. An algorithm was developed as a script in a commercial treatment planning system (Raystation, Raysearch, Stockholm, Sweden) for calculating patient specific compensator shapes. This algorithm can be adapted to design either surface compensators, or ones designed to fit into the electron cut out. The script uses the TPS to iteratively calculate the dose distribution in a patient, and then adjusts the shape of the compensator to account for any overdosed or underdosed regions. This process repeats until clinical goals are achieved. Additional steps smooth the compensator and shape it to be an easily 3D printed shape, then export it as a 3D model to be printed. To test the algorithm, a sample of eight PMRT patients previously treated at our institution was selected using consecutive sampling. The patients were selected to be representative of the body mass index range in our clinic. Dose distributions achieved using the algorithm-designed compensators were compared with the dose distributions in individual patients from conventional multi-field plans. In particular, we examined the CTV coverage, heart dose, and lung dose. Additionally, we analyzed the time and cost required to fabricate each patients’ compensator using 3D printing. The material cost for each compensator was less than $50, and each compensator could be printed in less than 20 hours. In general, the compensator plans reduced the size and extent of hot spots relative to the traditional multi-field plans, while improving overall CTV coverage. Lung and heart doses were within clinical targets for all plans. Specific metrics for one patient are shown in Table 1.Abstract 1051; Table 1CTVHeartLeft LungPlan TypeStandardComp.StandardComp.StandardComp.D98 (cGy)14500285132100Mean Dose (cGy)3576464324026116411634D2 (cGy)664660481058196655893910 Open table in a new tab Patient-specific 3D printed tissue compensators are feasible, and a clinically acceptable option for PMRT patients. This work solves a major hurdle in the usage of tissue compensators by automating and simplifying the design and fabrication process. In the future, a similar implementation of the algorithm described here could be additionally applied to other treatment site.