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Radiation Survey Results and Workload Recommendations for a New Self-Shielded Stereotactic Radiosurgery (SRS) System

S Sorensen1*, S Srivastava1 , D Pinnaduwage1 , S Jani1 , X Yan1 , J Velez1, G Weidlich2 , M Bodduluri2 (1) Barrow Neurological Institute (BNI), St. Joseph's Hospital and Medical Center, Phoenix, AZ (2) Zap Surgical Systems, Inc, San Carlos, CA


(Sunday, 7/14/2019) 1:00 PM - 2:00 PM

Room: Stars at Night Ballroom 4

Purpose: To evaluate staff and public safety exposure and determine an acceptable workload to support state licensure for the Zap-X (Zap Surgical Systems Inc, San Carlos, CA) self-shielded SRS system.

Methods: Independent exposure readings were taken by the vendor, site physicist, and state inspection team. All groups used their own independent equipment (Fluke Radiation Survey Meters). Each team took 15 measurements, 14 evenly spaced around the system at approximately 1 meter away, and at the treatment console (TC). Nine additional areas outside the room including a viewing area, public walkway, treatment planning area (TPA), and roof were measured by the state and onsite physicist. Exposure readings, with the beam pointing in 5 unique orientations were measured for each location. For the first eight treatment fractions, integrated exposure was measured from the time the patient entered the room until they left (~1hr) using survey meters (SM) and pocket dosimeters (PD) at two locations (TC & TPA). Six optically stimulated luminescence (OSL) area monitors were placed inside the treatment room on the four walls, at the treatment console, and in the hallway for three months (one quarter) by the site and state.

Results: The max exposure readings for all groups was <3mR/hr at any of the 14 measurement locations and ≤0.5mR/hr at the TC. The other 9 areas were <0.6 mR/hr. For all eight fractions, the max reading was <35µR for both SM and PD with an average of ~15µR. The max reading across the six area monitors was 9mrem (average: 3mrem) and there was good agreement (±2mrem) between the state and site.

Conclusion: The ZAP-X self-shielding is sufficient to meet staff and public radiation limits and supports a workload of at least 40 hours a week, or >2000 treatment fractions a year.


Stereotactic Radiosurgery, Shielding, Radiation Protection


TH- External beam- photons: protection and shielding

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