Chin-Cheng Chen1, Chang Chang1, Michael F Moyers2, Mingcheng Gao3, Dennis Mah1. 1. ProCure Treatment Center, Somerset, New Jersey 08873. 2. ProCure Treatment Center, Somerset, New Jersey 08873 and Shanghai Proton and Heavy Ion Center, Shanghai 201321, China. 3. CDH Proton Center, Warrenville, Illinois 60555.
Abstract
PURPOSE: The spot characteristics for proton pencil beam scanning (PBS) were measured and analyzed over a 16 month period, which included one major site configuration update and six cyclotron interventions. The results provide a reference to establish the quality assurance (QA) frequency and tolerance for proton pencil beam scanning. METHODS: A simple treatment plan was generated to produce an asymmetric 9-spot pattern distributed throughout a field of 16 × 18 cm for each of 18 proton energies (100.0-226.0 MeV). The delivered fluence distribution in air was measured using a phosphor screen based CCD camera at three planes perpendicular to the beam line axis (x-ray imaging isocenter and up/down stream 15.0 cm). The measured fluence distributions for each energy were analyzed using in-house programs which calculated the spot sizes and positional deviations of the Gaussian shaped spots. RESULTS: Compared to the spot characteristic data installed into the treatment planning system, the 16-month averaged deviations of the measured spot sizes at the isocenter plane were 2.30% and 1.38% in the IEC gantry x and y directions, respectively. The maximum deviation was 12.87% while the minimum deviation was 0.003%, both at the upstream plane. After the collinearity of the proton and x-ray imaging system isocenters was optimized, the positional deviations of the spots were all within 1.5 mm for all three planes. During the site configuration update, spot positions were found to deviate by 6 mm until the tuning parameters file was properly restored. CONCLUSIONS: For this beam delivery system, it is recommended to perform a spot size and position check at least monthly and any time after a database update or cyclotron intervention occurs. A spot size deviation tolerance of <15% can be easily met with this delivery system. Deviations of spot positions were <2 mm at any plane up/down stream 15 cm from the isocenter.
PURPOSE: The spot characteristics for proton pencil beam scanning (PBS) were measured and analyzed over a 16 month period, which included one major site configuration update and six cyclotron interventions. The results provide a reference to establish the quality assurance (QA) frequency and tolerance for proton pencil beam scanning. METHODS: A simple treatment plan was generated to produce an asymmetric 9-spot pattern distributed throughout a field of 16 × 18 cm for each of 18 proton energies (100.0-226.0 MeV). The delivered fluence distribution in air was measured using a phosphor screen based CCD camera at three planes perpendicular to the beam line axis (x-ray imaging isocenter and up/down stream 15.0 cm). The measured fluence distributions for each energy were analyzed using in-house programs which calculated the spot sizes and positional deviations of the Gaussian shaped spots. RESULTS: Compared to the spot characteristic data installed into the treatment planning system, the 16-month averaged deviations of the measured spot sizes at the isocenter plane were 2.30% and 1.38% in the IEC gantry x and y directions, respectively. The maximum deviation was 12.87% while the minimum deviation was 0.003%, both at the upstream plane. After the collinearity of the proton and x-ray imaging system isocenters was optimized, the positional deviations of the spots were all within 1.5 mm for all three planes. During the site configuration update, spot positions were found to deviate by 6 mm until the tuning parameters file was properly restored. CONCLUSIONS: For this beam delivery system, it is recommended to perform a spot size and position check at least monthly and any time after a database update or cyclotron intervention occurs. A spot size deviation tolerance of <15% can be easily met with this delivery system. Deviations of spot positions were <2 mm at any plane up/down stream 15 cm from the isocenter.
Authors: Maria F Chan; Chin-Cheng Chen; Chengyu Shi; Jingdong Li; Xiaoli Tang; Xiang Li; Dennis Mah Journal: Int J Med Phys Clin Eng Radiat Oncol Date: 2017-05-16
Authors: Brandon S Imber; Brian Neal; Dana L Casey; Heba Darwish; Andrew L Lin; Oren Cahlon; Brian Chon; Henry Tsai; Eugen Hug; Yoshiya Yamada; T Jonathan Yang Journal: Int J Part Ther Date: 2019-05-01
Authors: Liyong Lin; Sheng Huang; Minglei Kang; Petri Hiltunen; Reynald Vanderstraeten; Jari Lindberg; Sami Siljamaki; Todd Wareing; Ian Davis; Allen Barnett; John McGhee; Charles B Simone; Timothy D Solberg; James E McDonough; Christopher Ainsley Journal: J Appl Clin Med Phys Date: 2017-02-02 Impact factor: 2.102