Fast and accurate position verification algorithms for dose delivery system in proton therapy scanning nozzle system

• Published in: Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment Accelerators, spectrometers, detectors and associated equipment, 2021-01, Vol.986, p.164719, Article 164719
• Main Authors: Lin, Yinjie, Tan, Ping, Guo, Huidong, Zhang, Lige, Lei, Hao, Yu, Yecheng, Li, Xingyu
• Format: Article
• Language: English
• Subjects: Fitting algorithm; Ionization chamber; Proton therapy
• ISSN: 0168-9002; 1872-9576
• DOI: 10.1016/j.nima.2020.164719

The spot position and size of a proton beam are critical parameters in the scanning dose delivery system. They need to be validated efficiently and accurately. But the traditional methods work poorly in some non-ideal cases. In this study, we develop effective means for the position verification algorithm, including the student’s t distribution fitting algorithm, the Slope method, as well as the improved Gaussian fitting algorithm. And we verify the accuracy of them experimentally. That is several times higher than the one of the traditional fitting algorithms. The root mean square error (RMSE) of the improved Gaussian fitting algorithm is less than 0.2 mm as the signal-to-noise ratio (SNR) is higher than 30 dB even when a damaged strip exists around the beam spot. Furthermore, we implement the proposed Gaussian fitting arithmetic and the Slope method in Field Programmable Gate Arrays (FPGA) to test their efficiency. If the clock frequency of the chip with enough calculation resources is higher than 10 MHz, the computing time can be less than 6μs and 4μs, respectively. Finally, we conduct a simulation experiment. The result shows that RMSE of the proposed three methods are all less than 0.3 mm as the SNR is around 25 dB.