In Situ Real-Time Dosimetric Studies for Spine Stereotactic Body Radiation Therapy in a Cadaver Implanted with Carbon-Fiber and Titanium Instrumentation

Objective: We sought to compare the dosimetric accuracy of postoperative stereotactic body radiation therapy in a carbon-fiber (CF) versus titanium instrumented spine using a cadaveric model.

Methods: In situ cadaveric implantation of titanium and CF instrumentation and dosimeter chips in a thoracic spine. The cadaver underwent stereotactic body radiation therapy, and a dose of radiation therapy was calculated, measured, and compared. The sensors were placed in positions to provide data on dosimetry near the screws (within 1 cm) and between the screws. The differences between calculated and measured doses were reported as percentages.

Results: There was a significant difference in the dosimetry from calculated versus measured values near the screws of CF compared with titanium (P = 0.0057) with a mean percentage difference of only 2.93 for CF and a much higher value of 19.32 for titanium near the screws. There was also greater variability in the percent difference for the 2 screw types, with differences ranging from -16.54% to 35.20% near titanium screws and -3.37% to 1.66% near CF screws.

Conclusion: More accurate dosimetry and radiation therapy delivery with CF screws compared with traditional titanium screws may have implications on optimal radiation delivery, as well as complication avoidance. This may be due to reduced scatter and thus lower variability in radiation delivery with the volumetric modulated arc therapy technique.