Utilization of Neurosurgical Biopsy Navigation System for Permanent Ra-224 Intracranial Implant In Phantom and Patient Studies
Abstract
Purpose
Brachytherapy with short-ranged diffusing alpha emitters offers a novel therapeutic modality to treat recurrent glioblastoma in previously irradiated areas. A neurosurgical navigation system traditionally used for biopsies is used to localize and implant the sources with the manufacturer’s custom applicator. Positional accuracy of the implant and dosimetric coverage of targets was analyzed to determine its feasibility in phantom and early trial patients.
Methods
An anthropomorphic head phantom and trial patient received treatment planning MRIs, utilizing MIM Symphony intercranial targets were contoured. Scans were imported into the Medtronic StealthStation surgical navigation system to allow the neurosurgeon to plan the implant vector based on needle insertion and deep target locations. These planned points were used in the pre-operative plan to determine the positions and number of Ra-224 diffusing alpha-emitters radiation therapy (Alpha-DaRT) sources. Utilizing the navigation system coupled with the source vendor’s custom radial applicator, surface guidance is used to position the applicator and deliver the sources. Post-implant CT is performed for to determine source positions and dosimetry.
Results
For the three phantom based feasibility studies 28, 42 and 56 sources were placed and had maximum radial deviation to the pre-plan of 0.5, 1.3 and 2.0mm and depth deviations of 0.6, 1.0 and 1.5mm. Planned target coverage for each was 95.3%, 94.8% and 94.0% and actual coverage was 86.7%, 91.8% and 90.5% respectively. For the first trial patient 21seeds were implanted with planned CTV coverage of 97.7% post implant dosimetry showed 95.4% coverage was achieved.
Conclusion
Alpha-DaRT implantation with Medtronic surgical navigation can be achieved with sufficient spatial accuracy and reproducibility to achieve acceptable dosimetric target coverage.