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Investigating Beneficial Capabilities Achievable by a Rotating Gamma Ray System in Stereotactic Body Radiation Therapy

A Eldib

A Eldib1,4*, M Fareed1 , J Fan1 , J Li2 , L Chen1 , M Sherif3 , M Abdel Gawad4 , C Ma1 , (1) Fox Chase Cancer Center, Philadelphia, PA, (2) OUR United RT Group, Xian, (3) kuwait cancer control center, Kuwait, kuwait, (4) Biophysics branch, department of physics, AlAzhar University, Cairo, cairo


SU-I-GPD-T-617 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: Gamma Ray Stereotactic Radiosurgery Systems available commercially have either stationary or rotational source configurations. It is expected that rotational systems not only reduce the number of sources utilized but also have beneficial dosimetric abilities in the treatment planning process. In this work, we investigate new optimization options achievable with a novel rotating gamma system (RGS).

Methods: We used the CybeRay system (OUR United RT Group, Xian, China), which is an RGS that rotates 360° along the axial direction and swings 35° in the superior direction. It includes 16 Co-60 sources focusing at the isocenter. The RT Pro planning system (version 1.00.4557, Prowess, Concord, CA) was used for treatment planning. An in-house Monte Carlo based system was used for final dose computation. We utilized non-coplanar beam arrangements in 10 cranial cases and 12 other body sites. We investigated the use of hybrid shots with variable weighing at different gantry angles through the arc delivery.

Results: Treatment plans were generated utilizing 25° swing angle in the superior direction for 9 cranial cases and utilizing swing angles from 10 to 25° mostly in the inferior direction for 10 other body sites. By weighing the beams, a better control was obtained over the isodose lines wrapping more conformable around the target. This methodology was further tested in different patient geometries and target shapes using Monte Carlo simulations and an in-house developed graphical user interface program. It was also shown that one shot with weighted sectors could achieve the same coverage/conformity index as that obtained with multiple shots. This also resulted in much reduced delivery time (>30%) based on our preliminary results.

Conclusion: The novel rotational system extended the gamma systems capabilities in searching for the best treatment plans and more efficient dose delivery.

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