SU-E-T-722: Technical and Clinical Experience with the 1st Single Room Proton Therapy System

Authors


Abstract

Purpose:

In December, 2013 we treated our first patient with the Mevion S250 Proton Therapy System. This followed seven months of acceptance testing and commissioning, including; dosimetric data acquisition, safety checks, establishment of QA programs, mechanical and imaging checks, modeling validation, etc.

Methods:

The Mevion S250 possesses a compact synchrocyclotron attached to a gantry due to its small size (1.8m diameter) and light weight (22 tons). The system includes a 6D robotic couch allowing for any beam trajectory. The system provides 3D-2D imaging via fixed x-rays. Our TPS is Varian Eclipse, for which modeling and validation comprised most of the commissioning. The electronic medical record system is Elekta's MOSIAQ 2.5, which provides connectivity for setup, imaging and treatment.

Results:

The modeling and validation met gamma of 3%/1mm for 98% of points. The imaging quality is superior than our other existing systems. Neutron dose was <1.0mSv/Gy for most clinical fields. The isocentricity of gantry and couch was measured to be ±0.5 and ±0.6mm, respectively. Daily QA is a 30 minute procedure, including; couch isocentricity, interlocks, warning indicators, imaging, and dosimetric checks for options. Output, modulation flatness, range, field symmetry are measured with a single exposure for 3 options. We currently treat 20–24 patients per day and uptime for most months has been >95%. Over the first 14 months, for our first 150 cases, were predominantly; adult CNS, pediatrics (including CSI), lung, and liver. Thorax patients receive weekly scans for adaptive planning.

Conclusion:

The Mevion S250 has added a vital option to compliment our other modalities within our NCI Comprehensive Cancer Center.

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