PURPOSE: To compare online image registrations of TrueBeam cone-beam CT (CBCT) and BrainLab ExacTrac x- @entity16039 imaging systems for cranial radiotherapy. METHOD: Phantom and @entity1 studies were performed on a Varian TrueBeam STx linear accelerator (Version 2.5), which is integrated with a BrainLab ExacTrac imaging system (Version 6.1.1). The phantom study was based on a Rando head phantom, which was designed to evaluate isocenter-location dependence of the image registrations. Ten isocenters were selected at various locations in the phantom, which represented clinical treatment sites. CBCT and ExacTrac x- @entity16039 images were taken when the phantom was located at each isocenter. The @entity1 study included thirteen @entity1 . CBCT and ExacTrac x- @entity16039 images were taken at each @entity1 's treatment position. Six-dimensional image registrations were performed on CBCT and ExacTrac, and residual errors calculated from CBCT and ExacTrac were compared. RESULTS: In the phantom study, the average residual-error differences between CBCT and ExacTrac image registrations were: 0.16  0.10 mm, 0.35  0.20 mm, and 0.21  0.15 mm, in the vertical, longitudinal, and lateral directions, respectively. The average residual-error differences in the rotation, roll, and pitch were: 0.36  0.11 degree, 0.14  0.10 degree, and 0.12  0.10 degree, respectively. In the @entity1 study, the average residual-error differences in the vertical, longitudinal, and lateral directions were: 0.13  0.13 mm, 0.37  0.21 mm, 0.22  0.17 mm, respectively. The average residual-error differences in the rotation, roll, and pitch were: 0.30  0.10 degree, 0.18  0.11 degree, and 0.22  0.13 degree, respectively. Larger residual-error differences (up to 0.79 mm) were observed in the longitudinal direction in the phantom and @entity1 studies where isocenters were located in or close to frontal lobes, i.e., located superficially. CONCLUSION: Overall, the average residual-error differences were within 0.4 mm in the translational directions and were within 0.4 degree in the rotational directions.

SU-F-J-42: Comparison of Varian TrueBeam Cone-Beam CT and BrainLab ExacTrac X- XXXX for Cranial Radiotherapy.

@entity1 :: ('9606', 'Species') :: ['patients', 'patient'] @entity16039 :: ('255564', 'Species') :: ['ray']
@entity16039 :: (255564,Species) :: ['Ray']
