Room: AAPM ePoster Library
To examine the feasibility of MRI guided pre-plan using advanced gynecological applicator Venezia for high-dose-rate (HDR) interstitial brachytherapy.
A potential Venezia interstitial implant patient was identified in our department. In order to understand the geometry of the applicator set including possible needle positions in relation to the tumor location, an MRI scan was performed with the appropriate Venezia applicator combination inserted in the patient’s cervix for a pre-plan evaluation. Additionally, a CT of the same applicator was taken without the patient to provide clear visualization of the applicator itself. The MRI and CT were registered based on the applicator geometry using MIM. In the brachytherapy treatment planning system (TPS), the applicator library was used for catheter reconstruction purpose. The high-risk clinical target volume (HRCTV) was defined based on the MRI. In the TPS, we reconstructed the needles by projecting straight needle pathways cephalically from the Venezia perineal template. The usable needle positions were determined based on their relative position to the tumor.
Eleven needles were determined as valuable in the final pre-plan, with desirable dosimetric results (HRCTV D90 = 100.2%, V100 = 90.1%). A needle map based on this pre-plan was also generated, which could be utilized on the day of actual implantation as an anatomy-based starting point reference. While the location of the tumor was subsequently determined via MRI to be too close to the uterine vessels for safe treatment, the exercise was extremely useful for characterizing the performance and treatment potential of the device.
This case study demonstrated that MRI guided pre-plan for Venezia interstitial implants is feasible, and that pre-plan MRI can be valuable for clinical evaluation of implant suitability.