Abstract Background and purpose To assess the feasibility of postoperative stereotactic body radiation therapy (SBRT) for patients with hybrid implants consisting of carbon fiber Boxers reinforced polyetheretherketone and titanium (CFP-T) using CyberKnife.Materials and methods All essential steps within a radiation therapy (RT) workflow were evaluated.First, the contouring process of target volumes and organs at risk (OAR) was done for patients with CFP-T implants.
Second, after RT-planning, the accuracy of the calculated dose distributions was tested in a slab phantom and an anthropomorphic phantom using film dosimetry.As a third step, the accuracy of the mandatory image guided radiation therapy (IGRT) including automatic matching was assessed using the anthropomorphic phantom.For this goal, a standard quality assurance (QA) test was modified to carry out its IGRT part in presence of CFP-T implants.
Results Using CFP-T implants, target volumes could precisely delineated.There was no need for compromising the contours to overcome artifact obstacles.Differences between measured and calculated dose values were below 11% for the slab phantom, and at least 95% of the voxels were within 5% dose difference.
The comparisons for the anthropomorphic phantom showed a gamma-passing rate (5%, 1 mm) of at least 97%.Additionally the test results with and without CFP-T BMX Bikes implants were comparable.No issues concerning the IGRT were detected.
The modified machine QA test resulted in a targeting error of 0.71 mm, which corresponds to the results of the unmodified standard tests.Conclusion Dose calculation and delivery of postoperative spine SBRT is feasible in proximity of CFP-T implants using a CyberKnife system.