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Accuracy of 3D/3D and 3D/2D Registration in Intracranial Radiosurgery Using 6DOF Robotic Couch

H Kuo1*, S Berry2 , A Ballangrud3 , P S Atwal4 , C Della Biancia5 , P Pathare6 , D Shasha7 , D Lovelock8 , M Hunt9 , (1) Memorial Sloan Kettering Cancer Center, Norwalk, CT, (2) Memorial Sloan Kettering Cancer Center, New York, NY, (3) Memorial Sloan-Kettering Cancer Center, New York, NY, (4)BC Cancer - Abbotsford, BC, CAN, (5) Memorial Sloan-Kettering Cancer Center, New York, NY, (6) Norwalk Hospital, Norwalk Hospial, CT, (7) Memorial Sloan Kettering Cancer Center, Nwe York, NY, (8) Mem Sloan-Kettering Cancer Ctr, New York, NY, (9) Memorial Sloan Kettering Cancer Center, New York, NY


(Monday, 7/30/2018) 3:45 PM - 4:15 PM

Room: Exhibit Hall | Forum 6

Purpose: To investigate the accuracy of two 3D/3D CT to CBCT registration platforms as well as a 3D/2D CT to X-ray projection registration method. These three technologies are available to perform 6D registrations for image-guided intracranial radiosurgery.

Methods: Eight fiducial markers were asymmetrically placed on the surface of a stereotactic head phantom. The solution for the transformation between the two image sets in rotation and translation was optimized through least-squares fitting of the fiducial positions using singular value decomposition (SVD). This was used as the gold standard to evaluate the rotational accuracy of 3D/3D registration in Varian’s platform, as well as 3D/3D and 3D/2D registration in the BrainLab ExacTrac system. The phantom was setup on a baseplate with all rotations 0 degrees, and 3 degrees in roll and pitch. Measurements of rotational shifts were made at four different intracranial isocenters using the SVD, the 3D/3D and 3D/2D registration methods. Wilcoxon signed-rank test was utilized to compare the difference of each registration method with SVD. A p-value<0.05 was considered significant.

Results: The setup difference between planning CT and CBCT using SVD for all 12 positions showed median and range values of -0.9° [1.0°,-2.8°], -0.3° [0.1°,-3.3°], -1.2° [2.8°, -2.7°] for yaw, pitch, and roll, respectively. Comparing to the SVD measurement, the rotational differences at yaw, pitch, and roll using Varian’s 3D/3D registration were 0.0° [0.2°, -0.5°] (p=0.182), 0.0° [0.3°,-0.2°] (p=0.09), and -0.1° [0.2°,-0.4°] (p=0.73). They were -0.1° [0.6°,-0.4°] (p=0.003), 0.1° [0.6°,-0.1°] (p=0.47), and 0.1° [0.5°,-0.2°] (p=0.52) for ExacTrac 3D/3D registration and -0.4° [-0.1°,-0.7°] (p<0.001), 0.3° [0.6°,0.0°] (p<0.001), and -0.2° [0°, -0.4°] (p<0.001) for ExacTrac 3D/2D registration.

Conclusion: Both 3D/3D rotational registrations were accurate. 3D/2D registration introduced 0.2°-0.4° rotational inaccuracy in intracranial cases.


Image Guidance, Radiosurgery, Registration


IM- Multi-modality imaging systems: Other

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