Scanned Proton Beam Performance and Calibration of the Shanghai Advanced Proton Therapy Facility

Hang Shu,Chongxian Yin,Haiyang Zhang,Ming Liu,Manzhou Zhang,Liying Zhao,Kecheng Chu,Xiaolei Dai,Michael F Moyers

doi:10.1016/j.mex.2019.08.001

Abstract

The Shanghai Advanced Proton Therapy facility (SAPT) is a hospital-based facility that began construction in December of 2014 with commissioning of the first scanned proton beam line starting in October of 2017. Proton beams are extracted from a synchrotron accelerator with energies between 70 and 235 MeV. Beam delivery uses the modulated scanning and energy stacking techniques to produce a maximal scanning area of 40 × 30 cm2 at the iso-center. Prior to clinical use, the beam delivery system was characterized and calibrated following the guidelines of the IEC 62667 medical electronic equipment standard including the spot size in air, spot position, depth dose distributions, and lateral dose profiles, as well as the beam monitor calibrations following the IAEA TRS-398 recommendations with small differences.•The measured dosimetric results showed that the full width at half maximum (FWHM) for the beam spot size in air varied approximately from 6 mm to 13 mm. The dose fall-off (DDF) derived from the measured depth dose in water varied from 4.7 mm at 235 MeV to 0.7 mm at 70 MeV. The homogeneity of the scanned field was better than 2% for various energies as expected.•Furthermore, the beam reproducibility and proportionality delivery accuracy was also stable with the results better than 0.1% and 1% respectively. Finally, the dose monitor calibration factor, its reproducibility and stability were tested. Reproducibility tests exhibited a standard deviation (SD) result of less than 1% during the test period.•All the measured dosimetric parameters showed that the design specifications were well achieved and the results are suitable for being used as a part of the clinical commissioning and quality assurance program for treating patients.

Highlights

IntroductionProton therapy is an excellent tool for radiation therapy, especially for those tumors located close to critical organs [1,2,3]
Interest in tumor therapy with protons has been increasing over recent years because the depth of the high-dose Bragg peak of the proton beam is well-defined and little dose is delivered distal to the Bragg Peak
The measured dosimetric results showed that the full width at half maximum (FWHM) for the beam spot size in air varied approximately from 6 mm to 13 mm

Summary

Introduction

Proton therapy is an excellent tool for radiation therapy, especially for those tumors located close to critical organs [1,2,3] With this in mind, a hospital-based irradiation facility was designed and built for the treatment of deep-seated tumors using energies up to 235 MeV [4]. A variety of tools were used to study the beam performance qualities according to the IEC 62667 light ion beam medical equipment performance characteristics standard [5]. This manuscript describes these tools and tests

Methods

Results

Conclusion