Purpose: Presence of metal stabilization devices causes several issues in radiotherapy including imaging artifacts, possible dosimetric discrepancy and beam energy limitation. Carbon-Fiber Reinforced Polyetherthrketone (CFR-PEEK) material has been a potential alternative fixation with its radiolucency, and strength comparable to commonly used titanium devices. Previous studies have only focused on the dosimetric comparison for the screws themselves which are only part of the fixations. In this study, we present the dosimetric comparisons between the plans and the measurements on radiochromic films using a bone phantom with the entire CFR-PEEK fixations.
Methods: CT scans were obtained with a specially designed bone phantom with CFR-PEEK fixations under water phantoms representing neck and abdomen. The bone phantom was designed to resemble the shape and the HU values of vertebrae and spinal cord inside. A bone density phantom was scanned with the bone phantom for calibration. The bone phantom consists of two pieces, between which a film was placed for dosimetry measurement. Three stereotactic radiation plans were generated with mock targets near the fixations (one for neck and two for abdomen) and delivered to the bone phantom and the fixations. Coronal dose profiles were acquired with radiochromic films to evaluate the dose differences.
Results: CFR-PEEK fixations did not determine any HU artifacts on CT images resulting in better image quality and easier delineation. The coronal profiles compared between the plans and measurements showed a reasonable agreement.
Conclusion: This work evaluated dosimetric profiles on plans and measurements on CFR-PEEK fixations with a bone phantom. It demonstrated that the fixations provide better image quality and reduced dose uncertainty in target near the fixations. Further comparison with metal fixations is warranted.