Evaluation of multi-institutional end-to-end testing for post-operative spine stereotactic body radiation therapy

Abstract

Background and purpose: Post-operative spine stereotactic body radiation therapy (SBRT) represents a significant challenge as there are many restrictions on beam geometry to avoid metal hardware as it surrounds the target volume. In this study, an international multi-institutional end-to-end test using an in-house spine phantom was developed and executed. The aim was to evaluate the impact of titanium spine hardware on planned and delivered dose for post-operative spine SBRT. Materials and methods: Five centers performed simulation, planning and irradiation of the spine phantom, with/ without titanium metal hardware (MB/B), following our pre-specified protocol. The doses were calculated using the centers' treatment planning system (TPS) and measured with radiophotoluminescent glass dosimeters (RPLDs) embedded within each phantom. Results: The dose differences between the RPLD measured and calculated doses in the target region were within ± 5% for both phantoms studied. Differences greater than 5% were observed for the spinal cord and the out-of-the target regions due to steeper dose gradient regions that are created in these plans. Dose measurements within ± 3% were observed between RPLDs that were embedded in MB and B inserts. For the spinal cord and the out-of-target regions surrounded by metal hardware, the dose measured using RPLDs was within 3% different near the titanium screws compared to the dose measured near only the metal rods. Conclusion: We have successfully performed the first multi-institutional end-to-end dose analysis using an inhouse phantom built specifically for post-operative spine SBRT. The differences observed between the measured and planned doses in the presence of metal hardware were clinically insignificant.

Stereotactic Radiosurgery for Postoperative Spine Malignancy: A Systematic Review and International Stereotactic Radiosurgery Society Practice Guidelines

“…In a multi-institutional analysis, Furuya et al evaluated the dosimetric impact of spine SBRT with an in-house spine phantom assessed with and without metal hardware in place. 45 Dose differences introduced by the presence of metal was within 3% in both the target and spinal cord between the two phantoms as measured by radiophotoluminescent glass dosimeters, thus implying that the impact of titanium hardware on dose delivery is clinically acceptable. Additionally, dose calculation with the metal hardware density assigned impacted the calculated maximum point dose (Dmax) of the spinal cord especially in the area close to the screws, affirming the importance of delineating the metal hardware prior to dose calculation.…”

Accuracy of the doses computed by the Eclipse treatment planning system near and inside metal elements

“…Several studies show that both algorithms (AAA and AXB) could accurately calculate the doses near the metal 25 – 27 . However, these studies focus specifically on spine SBRT (stereotactic body radiation therapy) treatment in the presence of titanium screws.…”

Evaluation of computed tomography artefacts of carbon-fiber and titanium implants in patients with spinal oligometastatic disease undergoing stereotactic ablative radiotherapy

“…Consequently, these implants pose problems with respect to (time-consuming) radiation planning and accurate delivery of the calculated dose 22 . This could lead to complications such as spinal cord radio necrosis, progressive myelopathy, spinal hemorrhage, and fractures 23 , 24 . Tedesco et al reported that scattering of radiotherapy from titanium spine implants can compromise the therapeutic effect and lead to unwanted radiation to adjacent healthy tissue 25 .…”