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Exploring the Dosimetric Advantage of a Novel Rotating Gamma Machine Equipped with Both MLC and Multiple Cone Colimators

A Eldib

A Eldib1,3*, I Veltchev1 , T Lin1 , R Price1 , G Mora2 , M Abdel Gawad3 , M Sherif4 , C Ma1 , (1) Fox Chase Cancer Center, Philadelphia, PA, (2) University of Lisbon, Lisbon, ,(3)Biophysics branch, department of physics, AlAzhar University, Cairo, Egypt, (4) kuwait cancer control center, Kuwait, kuwait


SU-I-GPD-T-618 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: Stereotactic radiosurgery with Gamma ray systems (GRS) has been very successful in treating many intracranial patients. However, the cone collimation utilized in those systems makes treatment of some lesions challenging owing to their complex irregular shapes. In this study we explore the dosimetric advantage of a novel rotating GRS equipped with MLC and multiple cone collimators.

Methods: A novel rotating GRS has been developed with a ring gantry supporting two collimation systems. The CybeRT system (OUR United RT Group, Xian, China) has a focusing head containing 16 Co-60 sources focusing at the isocenter, each having 4 different changeable cone collimators, and a MLC head containing a single cobalt source. The new machine is designed to treat both intra- and extra-cranial body sites. In this work, 22 previous patients treated using Varian VMAT and CyberKnife were replanned using the RT Pro planning system (version 1.00.4557, Prowess, Concord, CA). These treatment plans were evaluated based on the isodose distribution, dose volume histograms and the estimated treatment time.

Results: CybeRT plans were compared to previously treated CyberKnife plans and Eclipse plans. Comparable planes were achieved in most cases. Great reduction in treatment time was obtained with the MLC system. The treatment time for a lung case previously treated on the CyberKnife was 50 minutes while it would take 94 minutes using the focusing head with cone collimators alone to achieve the same plan quality. However, using the MLC head, a high-quality plan was generated with an estimated treatment time of <6 minutes. The cone collimators provided better plan quality for small and spherical targets while the MLC is more efficient and effective for large and irregularly shaped targets.

Conclusion: The GRS utilizing both cone collimator and MLC systems allows for more efficient and effective SRS/SRT for intra- and extra-cranial treatments.

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