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Using Customized Headrest to Increase the Reproducibility of C-Spine Curvature in Spinal SBRT

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X Wang

X Wang*, H Wang , D Luo , T Briere , E Han , Z Wen , G Zhao , J Yang , J Li , M McAleer , A Bishop , A Ghia , MD Anderson Cancer Ctr., Houston, TX


SU-H3-GePD-T-1 (Sunday, July 30, 2017) 4:00 PM - 4:30 PM Room: Therapy ePoster Lounge

Purpose: To assess the reproducibility of C-spine curvature using a customized headrest, which is crucial for accurate and safe spinal SRS/SBRT treatment in this region.

Methods: A low-density thermoplastic-based cushion was molded to form a customized headrest, which encompassed the patient’s head to shoulder to provide circumferential support and comfort. For analysis of the reproducibility of curvature, the mid-sagittal plane of the simulation CT and treatment CBCT was used. Starting with treatment CBCT, the posterior-superior corner of each visible vertebral body was marked with a point. A spinal line (SL) was constructed by connecting the most superior and inferior points, and the length of SL was calculated. Then, the lengths of each orthogonal line (heights) from other points to the SL were calculated, and a vector of length was recorded. The same analysis was performed using the simulation CT images and the same vertebral levels evaluated on the CBCT. The difference in the length of SL and heights of each vertebra between CBCT and simulation CT provides a quantifiable measure of the reproducibility in C-spine curvature. Five patient cases were assessed in this pilot study.

Results: CBCT was able to cover at least 6 vertebrae in this study, including the whole C-spine region if the isocenter was located between C3 to C4. Using the customized headrest, four of the five cases (80%) showed the difference of SL length and vertebral heights between simulation CT and treatment CBCT to be within 1mm; the remaining case had a height difference of 1.2mm at C5. In contrast, use of the standard headrest had difficulty in achieving sub millimeter difference.

Conclusion: C-spine curvature is highly reproducible with the use of a customized headrest. Most cervical vertebrae can be aligned within 1mm with the use of 6-degree couch that correct the rotational difference of SL.

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