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Patient Adapted, Image Guided Intraoperative Radiotherapy for Spinal Metastases

Y Chen

Y Chen1*, A Latefi2 , Y Cao1 , S Souri1 , L Potters1 , E Klein1 , A Riegel1 , M Ghaly1 , (1) Northwell Health, Lake Success, NY, (2) Northwell Health, Manhasset, New York


WE-RAM2-GePD-T-4 (Wednesday, August 2, 2017) 10:00 AM - 10:30 AM Room: Therapy ePoster Lounge

Purpose: To implement a novel clinical approach for combination of intraoperative radiotherapy and kyphoplasty (kypho-IORT) for localized spinal metastases using a Zeiss Intrabeam 50 kV x-ray system.

Methods: The PTV and OAR (spinal cord or cauda equina) were contoured for selected patients based on fusion of MRI and CT images acquired prior to the kypho-IORT procedure. A 180° rotatable isocentric C-arm imaging system in operating room (OR), capable for fluoroscopy, radiography, and 3D CBCT, was used for precise guidance of positioning the needle applicator of the Intrabeam system. The 3D CBCT image with the applicator position in vivo was then taken and registered to the previous CT or MRI image for drawing the applicator tip or the x-ray source isocenter. The 10 Gy dose (RBE dose of 14 Gy) was prescribed to the mean distance from the source isocenter to the distal boundary of the PTV. The prescription was limited by asserting a maximum dose limit to the OAR of 8 Gy.

Results: Total 7 patients have been treated by this kypho-IORT procedure in our institute since November of 2016, among whom 2 patients were each treated for 2 sites. The patients’ ages ranged from 38–87 years old. The treated vertebrae ranged from T9–L5. The actual treatment depths (10 Gy isodose depth) varied from 6.5–15 mm with the treatment time of 1–8 min. The calculated BED doses (using RBE=1.4 and α/β=2 Gy) to OAR were 6–75 Gy. Two treatments among total 7 delivered IORT treatments were compromised because the applicator tip was closer to the OAR.

Conclusion: The novel kypho-IORT protocol, guided by real-time 3D CBCT imaging and featuring a patient adapted prescription depth and live treatment planning in OR, is capable to achieve greater local disease control and avoid damage to spinal cord or cauda equina.

Funding Support, Disclosures, and Conflict of Interest: This work is supported in part by Carl Zeiss Meditec AG, ZEISS Group, Germany.

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