Author: Timothy J Allen, David A. Sterling 👨🔬
Affiliation: University of Minnesota Physicians, Department of Radiation Oncology, University of Minnesota, Minneapolis 🌍
Purpose: Treatment planning for the Venezia HDR brachytherapy applicator is often performed using inverse planning tools such as IPSA or HIPO. However, there are planners who are either unfamiliar with or lack access to these tools. This work presents a Venezia forward-planning method and uses tandem and ring (T&R) planning as its foundation.
Methods: Planning was performed in Oncentra v4.6 to an HRCTV dose of 550 cGy. First, conventional T&R plans were generated using point optimization (i.e., no needle dwells). The normalization and optimization were then switched to graphical mode to prevent dwell time changes after interstitial needle dwells are added. Needle dwell times were manually adjusted and kept uniform (within and among all needles) to improve HRCTV dose coverage while minimizing OAR dose. An example case is presented and compared to IPSA/HIPO plans.
Results: The uniform needle loading had a weight of 0.08. The example forward plan had HRCTV D90 of 670.58 cGy compared to 671.88 cGy and 647.23 cGy for IPSA and HIPO plans, respectively. HRCTV V100% was 97.63%, 98.31%, and 97.25% for forward planned, IPSA, and HIPO respectively. OAR D2cc was similar among the three plans (Bladder: 525.65, 551.05, 498.15 cGy; Rectum: 221.77, 285.99, 216.54 cGy; Sigmoid: 339.13, 343.10, 332.17 cGy; forward planned, IPSA, and HIPO respectively.)
Conclusion: This work introduces a new method of planning using Venezia applicators without the use of inverse planning tools. The plan produced was similar to IPSA and HIPO derived plans in terms of HRCTV coverage and OAR dose metrics. As some planners are unfamiliar with, or lack access to, inverse planning tools, this method provides an attractive alternative that is both simple to implement and leverages well-understood T&R planning.