Prospective Evaluation Of A Dedicated Spine Radiosurgery Program Using The Elekta Synergy S

Peter Gerszten1, Josef NOVOTNY2, Mubina Quader3, Valerie C. Dewald3, John C Flickinger3

1Pittsburgh, PA United States 2Hospital Na Homolce 3UPMC, Pittsburgh, USA

Keywords: spinal cord, spinal radiosurgery, spinal cord, outcome, cancer

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       Our center began a dedicated spine radiosurgery program using the ELEKTA Synergy S. Cone beam computed tomography (CBCT) image guidance has become more widely used for spine radiosurgery delivery. Concerns of intra-treatment patient movement have raised concerns regarding the utilization of CBCT image guidance for single fraction spine radiosurgery.  
     This study prospectively evaluated a Synergy S for spine radiosurgery program, including an evaluation of patient positioning accuracy using this technology.
      One hundred thirty spine and paraspinal lesions were treated.
     They were treated using the Synergy S 6 MV linear accelerator with a beam modulator and CBCT image guidance combined with a HexaPOD couch that allows patient positioning correction in 3 translational and 3 rotational directions. Lesion location included 23 cervical, 52 thoracic, 35 lumbar, and 20 sacral. Primary histologies for the metastatic lesions (108 cases) included 25 breast, 16 lung, 15 sarcomas, and 10 renal. Benign tumor histologies (22 cases) included 9 schwannomas, 3 neurofibromas, and 4 meningiomas. Twenty-one lesions (16%) were intradural. Eighty-three lesions (64%) had received prior conventional fractionated radiotherapy. Indications for radiosurgery included pain in 60 cases (46%), as a primary treatment modality in 35 cases (27%), and for radiographic progression after radiotherapy in 30 cases (23%). Thirty-nine lesions (30%) contained titanium instrumentation and/or methylmethacrylate bone cement. To measure intra-treatment patient movement, 3 quality assurance (QA) CBCTs were performed and recorded: immediately prior to, halfway, and at the end of the treatment. The positioning data and fused images of planning CT and CBCT were analyzed. From each of 3 QA CBCTs, 3 translational and 3 rotational coordinates were obtained.
      Prescribed single fraction GTV dose for the cohort was 11-19 Gy (mean 14 Gy); GTV volume 1.2 to 491.7 cm3 (mean 39.2 cm3); 7 to 14 beams utilized (median 9 beams). Mean treatment time including setup was 64 minutes. The magnitude of the 3D vector was found to be 1.3±1.0 mm at halfway and 1.5±0.7 mm at the end of treatment. No spinal cord toxicity has occurred (median follow-up 11 months).
     This is a retrospective study.
      Single fraction spine radiosurgery using the Synergy S was determined to be safe, feasible, and accurate. 
     This technique provides for a translational position accuracy of < 2.0 mm.


Project Roles:

P. Gerszten (), J. NOVOTNY (), M. Quader (), V. Dewald (), J. Flickinger ()