Introduction

Radiation dose escalation to the dorsal vertebral body (DVB) and pedicles is often limited by the proximity of spinal cord and cauda equina, resulting in sub-optimal target coverage. Directional low-dose-rate (LDR) palladium-103 (¹⁰³Pd) membrane brachytherapy devices (MBDs) incorporate gold-shielded sources that enable anisotropic radiation delivery and facilitate selective dose escalation. This study evaluated the feasibility and dosimetric characteristics of anterior epidural placement of a directional ¹⁰³Pd MBD in a cadaveric spine model.

Material and methods

Custom-contoured ¹⁰³Pd MBDs were implanted within the ventral epidural space at thoracic and lumbar levels in a human cadaver under fluoroscopic guidance. Device orientation, source geometry, and
0.8 cm source spacing were maintained to preserve directional dose emission. Post-implant CT and MRI were performed to assess device visualization and imaging artifact. Dosimetric analysis was conducted using Eclipse™ BrachyVision™ with AAPM TG-43 formalism to evaluate dose distributions to the DVB, pedicles, spinal cord, and cauda equina.

Results

Implantation was successfully performed at both spinal levels, with stable positioning and appropriate orientation of the gold-shielded surface to adjacent neural structures. CT and MRI demonstrated excellent device visualization, accurate source reconstruction, and minimal imaging artifact. A prescription dose of 47 Gy at 5 mm achieved ≥ 90% isodose coverage of the DVB and pedicles. Maximum doses to the spinal cord and cauda equina were limited to 9.2 Gy and 3.5 Gy, respectively. Directional shielding produced > 60% attenuation across the shielded plane, resulting in substantial neural sparing while maintaining target coverage.

Conclusions

Anterior epidural placement of a directional ¹⁰³Pd MBD is technically feasible, providing highly conformal irradiation of posterior vertebral structures while maintaining low doses to adjacent neural tissues. This approach may represent a novel strategy for overcoming spinal cord dose constraints and facilitating selective dose escalation in the management of spinal tumors.