A Novel Approach for Real-Time, Personalized Breast HDR Brachytherapy Treatment Using 3D Printing Technology

Abstract

In breast interstitial high-dose-rate (HDR) brachytherapy, the number and positions of the catheters are usually chosen manually using a preimplant CT scan or fixed using 2D ultrasound, since real-time methodologies are non-existent. In this work, we present an innovative approach for real-time and personalized 3D ultrasound (3DUS) planning in breast HDR brachytherapy. Two different end-to-end procedures were tested for real-time planning. Both methods are using a computer controlled robotic 3DUS system for breast brachytherapy and a freehand catheter optimization algorithm; based on the open source Centroidal Voronoi Tessellations (CVT) algorithm and IPSA. The scanner is mounted on the Kuske template (Nucletron, an Elekta Company, Stockholm, Sweden) so that the scan direction is longitudinal to the catheter axis. The first method is using the Kuske template, meaning that the optimize catheter positions are snap to the available position within the template. The second method makes use of personalized templates built from a 3D printer using the results of the catheter optimization process. The new template fits on the Kuske assembly, however a new concept has emerged where personalized plates can be inserted in the middle of the template (Fig. 1a and 1b). This allows the user to keep the template in place and insert 3D printed personalized plates. The procedures were tested with 12, 14 and 16 catheters, three times each, in an agarose-based phantom with a hypo-echoic mass. The 3DUS acquisition time is less than 7s and the catheter optimization algorithm can obtain 10 complete treatments plans, with the corresponding dosimetric indices, in 90s. The catheter optimization algorithm was shown to enable reduction of the number of catheters to 12 without breaking ABS recommendations. It was also shown to be robust up to 3 mm implantation errors. The printing time of the two plates was approximately two hours. After the insertion procedure, dosimetric indices were still within RTOG guidelines down to 14 catheters for the Kuske method and down to 12 for the personalized template method. The method with the personalized template was significantly better (student t-test; p < 0.05) in terms of the cost function and PTV V100 as well as PTV D90. Fig. 1c and 1d are showing PTV V100 results compared to the optimal CVT optimization algorithm for the Kuske method (c) and for the personalized method (d). We have devised a simple, fast and efficient method for real-time and personalized 3DUS breast HDR brachytherapy treatment using inverse planning and 3D printing technology. This novel personalized approach could be easily extended to prostate and other sites.