Purpose: To develop a novel high-dose-rate (HDR) interstitial spine brachytherapy technique using an intraoperative mobile CT guided navigation system.
Methods: Clinical target volume (CTV) and organs at risk (OAR) were contoured on CT with PET/CT and MR fusion. Pre-implant plan was created by virtually implanting catheters into the CTV and optimizing target coverage while maintaining OAR doses under AAPM TG-101 constraints. CT images, contours, and needle trajectories were transferred from the planning system (Elekta Oncentra Brachy) to a surgical navigation system (Brainlab Curveâ„¢). A reference reflective marker array was attached to the patient. The reference array and the intraoperative mobile CT (Brainlab AIRO) were registered with the navigation system. A CT scan was obtained and fused with the pre-implant CT. A Jamshidi needle was placed into the target while the system displayed the needle position in relation to patient anatomy and needle trajectories. Catheter was placed into the needle, and needle was removed. An intraoperative CT scan was performed, and a post-implant plan was made to deliver single fraction median dose of 18Gy (10-21Gy).
Results: 5 patients have been treated for thoracolumbar tumors. Median 2 catheters (1-4) were placed percutaneously in 3 patients and intraoperatively in 2 patients. Pre-implant plans showed median CTV D90 of 117% (110-148%), V100 of 96% (96-100%), and Dmax of 12-14Gy/16Gy to cord/cauda equina. Post-implant plans provided median CTV D90 of 114% (94-118%), V100 of 96% (87-99%), and Dmax of 11.7-13.7Gy/15.7Gy to cord/cauda equina. Our DVH data show improved target coverage when compared to the published series (GTV D90= 75% (31-94%) and V100=67% (35-83%)) by Yamada, et al without using a navigation system.
Conclusion: We demonstrate a novel treatment approach for spine tumors with HDR interstitial brachytherapy using an intraoperative CT guided navigation system, with improvements in target coverage and safe doses to OARs.