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Program Information

An On-Line Patient Specific Visual Implementation of Clear Zone Collision Detection Method for Varian Linac

W Feng

W Feng1*, A Chu2 , J Hu3 , (1) Bayhealth Medical Center, Tenafly, NJ, (2) St. Jude Children's Research Hospital, Memphis, TN, (3) Wayne State University, Detroit, MI


SU-I-GPD-T-228 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: To provide an on-line patient specific visual solution to detect collision between patient/couch and gantry for Varian Linacs.We consider this study to be innovative because it implements and validates gantry collision detection with not only couch but also specific patient. It support typical TPS with registration capability, and does not require additional software or look-up table. It can detect and adjust on-line during treatment planning process with visual assistance, and is especially useful for VMAT, non-coplanar plans.

Methods: A water phantom is created as CT imaging dataset to hold all the following contours. A cylindrical contours is generated with 82cm in diameter and 79cm in length, which define the clear zone of gantry rotation, a set of cylindrical contour is generated by rotate in left/right direction by every 5 or 10 degree to simulate couch rotation. Spherical contour of diameter of 10, 3, 0.8cm is designed as isocenter to help registration to patient isocenter. Thin cylindrical contour was used to denote clearzone sup-Inf direction, in case patient CT in unusual orientation or manually rotate by mistake.Import the phantom dataset with contours into specific patient, register phantom image with patient CT image with help of isocenter and SI direction contour, save the registration.Any contour stick out of side surface of clear zone cylinder is considered as potential collision.Also, we create another one with 2cm reduction in radius to accommodate patient positioning uncertainty.

Results: The technique is tested with clinical cases, it can detect couch collision on the side, lower rail, and superior head position. It can also detect collision with patient, as long as patient CT data is available from simulation.

Conclusion: Clear zone Collison detection method is clinical validated, it can detect not only couch but also patient collision with gantry head via visual assistance.

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