Orthogonal image pairs coupled with OSMS for noncoplanar beam angle, intracranial, single-isocenter, SRS treatments with multiple targets on the Varian Edge radiosurgery system.

ABSTRACT: Purpose:To characterize the accuracy of noncoplanar image guided radiation therapy with the Varian Edge radiosurgery system for intracranial stereotactic radiosurgery (SRS) treatments by assessing the accuracy of kV/kV orthogonal pair registration with Optical Surface Monitoring System (OSMS) monitoring relative to cone beam computed tomography (CT). Methods and materials:A Computerized Imaging Reference System head phantom and Encompass SRS Immobilization System were used to determine collision-free space for orthogonal image pairs (kV/kV) for couch rotations (CRs) of 45°, 30°, 15°, 345°, 330°, and 315°. Couch-induced shifts were measured using kV/kV orthogonal image pairs, OSMS, and cone beam CT. The kV/kV image pairs and OSMS localization accuracy was also assessed with respect to cone beam CT. Results:Mean orthogonal image pair differences for 315°, 330°, 345°, 15°, 30°, and 45° CRs were ?±0.60 mm and ±0.37°. OSMS localization accuracy was ?±0.25 mm and ±0.20°. Correspondingly, kV/kV localization accuracy was ?±0.30 mm and ±0.5°. Shift differences for various image pairs at all CRs were ?±1.10 mm and ±0.7°. Cone beam CT deviation was 0.10 mm and 0.00° without patient motion or CR. Conclusion:Based on our study, CR-induced shifts with the Varian Edge radiosurgery system will not produce noticeable dosimetric effects for SRS treatments. Thus, replacing cone beam CT with orthogonal kV/kV pairs coupled with OSMS at the treatment couch angle could reduce the number of cone beam CT scans that are acquired during a standard SRS treatment while providing an accurate and safe treatment with negligible dosimetric effects on the treatment plan.

SUBMITTER: Oliver JA 

PROVIDER: S-EPMC5605313 | biostudies-literature | 2017 Jul-Sep

REPOSITORIES: biostudies-literature