Room: AAPM ePoster Library
Purpose: To design and fabricate patient-specific, surface HDR brachytherapy applicators for the treatment of multiple complex targets with a simple daily set up.
Methods: A patient presented with bilateral basal cell carcinoma on his shins – three lesions on the right shin, two on the left. The physician prescribed 40 Gy in 15 fractions with HDR surface brachytherapy. Using CT data, individual applicators for each shin were created as structures in the TPS. The structure set was imported into the brachytherapy module of 3D Bolus (Adaptiiv Medical Technologies) to design the catheter trajectories within the applicator using the software’s automatic tunneling feature. After the applicators were printed, flexible 6F catheters were inserted through the tunnels and fastened in place with buttons to allow the HDR source to travel reliably through the applicator. A second CT simulation of the patient with the completed applicators was required to ensure proper fit and print quality, to create reference marks for daily setup on the patient, and to enable catheter reconstruction for planning purposes.
Results: Each applicator required 13 catheter tunnels to encompass the CTVs in all directions. After minor adjustments during the second CT simulation, the applicator fit the patient’s body contour and matched the modelled applicator well. A 3 mm margin in the lateral and superior-inferior directions was added to the CTV to account for daily setup variations. The resulting plan was able to cover greater than 98% of the PTV with 100% of the prescription, as well as minimize the areas receiving greater than 150% of the dose.
Conclusion: 3D-printed surface brachytherapy applicators can be successfully used to treat patients with bilateral shin skin cancers. The 3D-printed applicator provided excellent fit to the patient’s contour and was easy to use for treatment.
Funding Support, Disclosures, and Conflict of Interest: James Robar is a co-founder of Adaptiiv Medical Technologies.