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Design Study of Static and Dynamic Ridge Filters for FLASH-IMPT

G Zhang1*, W Gao2, M Jia3, H PENG1,4, (1) School of Physics and Technology, Wuhan University, China, (2) Cancer Radiation Therapy Center, Fifth Medical Center of Chinese PLA General Hospital, China, (3) College of Precision Instrument and Optoelectronics Engineering, Tianjin, China, (4) ProtonSmart Inc., Wuhan, China

Presentations

SU-H400-IePD-F4-6 (Sunday, 7/10/2022) 4:00 PM - 4:30 PM [Eastern Time (GMT-4)]

Exhibit Hall | Forum 4

Purpose: This paper focused on the designs of ridge filter (static and dynamic) for intensity-modulated proton therapy (IMPT), and its potential applications for FLASH-IMPT. Differing from pencil beam scanning (PBS), no energy/layer switching is required and the treatment time duration can be thus shortened.

Methods: Dose calculation within ridge filters and the medium was obtained using Monte-Carlo simulation. The design process was first verified in a water phantom and then tested in a patient case. Two designs of ridge filters (static: model A, dynamic: model B) were evaluated. The dynamic design is similar to the working principle of multiple leaf collimators in photon therapy. A conventional IMPT plan was selected as the reference for comparison, with regard to plan quality, dose-averaged dose rate (DADR) and total duration of treatment.

Results: For the water phantom, the dose distributions of two models show no significant difference relative to the reference plan. For the patient case, the dose rate volume histogram (DRVH) suggests that in order to achieve a dose rate of 40 Gy/s over 90% PTV, the beam intensity needs to be 2.51011 protons/s. For a fraction dose of 10 Gy, the total duration of treatment (irradiation time + dead time) can be shortened by a factor of 4.9 (model A) and 6.5 (model B), in comparison with the reference.

Conclusion: Two proposed designs may be used as alternatives to PBS-IMPT. They are promising candidates for the implementation of FLASH-IMPT, capable of achieving high dose rates while simultaneously maintaining dose conformity.

Keywords

Dosimetry

Taxonomy

TH- External Beam- Particle/high LET therapy: Proton therapy – computational dosimetry-Monte Carlo

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