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Evaluation of Intrafraction Motion During Spine Stereotactic Body Radiotherapy Using Pre and Post Treatment Cone Beam Computed Tomography

A Magnelli*, P Qi , S Balik , T Zhuang , S Chao , J Suh , P Xia , The Cleveland Clinic Foundation, Cleveland, OH


(Tuesday, 7/16/2019) 10:30 AM - 11:00 AM

Room: Exhibit Hall | Forum 3

Purpose: Spine stereotactic body radiotherapy (SBRT) requires accurate patient positioning and immobilization to protect the spinal cord or thecal sac. The purpose of this study is to evaluate intrafraction motion in patients receiving spine SBRT by analyzing pre- and post-treatment cone beam computed tomography (CBCT).

Methods: Fifty-two patients treated with SBRT to one or more adjacent vertebral bodies were selected. Patients with tumors at T5 or above were immobilized using a five-point thermoplastic mask. For tumors located at T6 and below, a full-body vacuum cushion along with an evacuated plastic wrap was used. For each patient, CBCT was acquired both prior to and following treatment. The pre- and post-treatment CBCT scans were registered using rigid alignment of the pertinent vertebral body. The translational and rotational shifts from these alignments represent intrafraction motion. Patients were stratified according to the spine level treated (C1-C7, T1-T5, T6-T12, L1-Sacrum) and patient motion for each group was evaluated.

Results: The average magnitude of intrafraction translation was (1.7 ± 0.8) mm for C1-C7, (1.8 ± 0.8) mm for T1-T5, (0.9 ± 0.3) mm for T6-T12 and (1.0 ± 0.5) mm for L5-Sacrum. The average intrafraction rotation for C1-C7 were (0.8 ± 0.5), (0.7 ± 1.2) and (0.4 ± 0.4) degrees in axial, sagittal and coronal planes, respectively. For T1-T5, rotations were (0.3 ± 0.2), (0.3 ± 0.2) and (0.4 ± 0.8) degrees. For T6-T12, rotations were (0.2 ± 0.2), (0.4 ± 0.5) and (0.3 ± 0.4) degrees. For L1-sacrum, rotations were (0.2 ± 0.3), (0.3 ± 0.3) and (0.2 ± 0.4) degrees.

Conclusion: Intrafraction motion for patients treated with spine SBRT was anatomically dependent. Patients treated to T5 and above had the largest intrafraction motion. To further reduce intrafraction motion, real-time motion monitoring or intrafraction imaging may be considered.


Stereotactic Radiosurgery, Immobilization


Not Applicable / None Entered.

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