Purpose: High-dose-rate-brachytherapy (HDR-BT) for malignant skin diseases is an important treatment option especially for complex target areas. To standardize and improve the quality and efficacy a novel planning approach with fully automated treatment planning based on 3D surface scanning, a 3D printable applicator holder (3D-AH), and augmented reality for verification is implemented.Materials and
Methods: For treatment preparation the target area is outlined and a 3D surface scan is performed. Our inhouse developed treatment planning system virtually places a model of a multi-channel flexible flap-applicator on the target area and optimizes the treatment plan including generation of a 3D-AH. The 3D-AH preserves the topology of flap applicator and guarantees a reproducible immobilization.The methodology was implemented and tested under IRB approval. Dosimetric comparison was performed by comparing dwell-times and achieved metrics of the conventional planning (CP) against the fully automated planning (AP). The quality of the 3D print is verified with a CT of the flap applicator latched into the holder followed by a registration onto the designed plan.
Results: The methodology was successfully implemented, and the results of representative patients are summarized. Automated treatment planning and 3D-AH model took less than five minutes. The plans covered a target area from 61cm2 to 142cm2 which corresponds to 60 to 142 used dwell-positions. Comparing AP and CP, the total treatment time and coverage in terms of D90 and the maximum dose showed no clinical significant difference. The registration showed that a sub mm setup accuracy was achieved.
Conclusion: The presented workflow automates treatment planning. Compared to printing full applicators the use of 3D-AH reduces the complexity of the 3D print and allows treatments on the same day when the 3D-scan is performed. The proposed methodology improves the overall treatment quality in complex HDR-BT and reduced the overall dose to the patient.