Prog Med Phys.  2022 Dec;33(4):108-113. 10.14316/pmp.2022.33.4.108.

Feasibility Test of Flat-Type Faraday Cup for UltrahighDose-Rate Transmission Proton Beam Therapy

• Pak Si
• Cho S
• An S
• Jeong S
• Shin D
• Lim Y
• Jeong JH
• Kim H
• Lee SB

• KMID: 2537878
• DOI: http://doi.org/10.14316/pmp.2022.33.4.108

Abstract

Purpose
Proton therapy has been used for optimal cancer treatment by adapting its Bragg-peak characteristics. Recently, a tissue-sparing effect was introduced in ultrahigh-dose-rate (FLASH) radiation; the high-energy transmission proton beam is considered in proton FLASH therapy. In measuring high-energy/ultrahigh-dose-rate proton beam, Faraday Cup is considered as a doserate-independent measurement device, which has been widely studied. In this paper, the feasibility of the simply designed Faraday Cup (Poor Man’s Faraday Cup, PMFC) for transmission proton FLASH therapy is investigated.
Methods
In general, Faraday cups were used in the measurement of charged particles. The simply designed Faraday Cup and Advanced Markus ion chamber were used for high-energy proton beam measurement in this study.
Results
The PMFC shows an acceptable performance, including accuracy in general dosimetric tests. The PMFC has a linear response to the dose and dose rate. The proton fluence was decreased with the increase of depth until the depth was near the proton beam range. Regarding secondary particles backscatter from PMFC, the effect was negligible.
Conclusions
In this study, we performed an experiment to investigate the feasibility of PMFC for measuring high-energy proton beams. The PMFC can be used as a beam stopper and secondary monitoring system for transmission proton beam FLASH therapy.

Keyword

Proton beam therapy; Faraday cup; FLASH

Figure

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  Fig. 1 Concept drawing of (a) conventional proton therapy and (b) transmission proton FLASH therapy. The image is adapted from the website (https://www.floridaproton.org/what-is-proton-therapy) and modified. PMFC, Poor Man’s Faraday Cup.

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  Fig. 2 Setup for Poor Man’s Faraday Cup (PMFC) and Advanced Markus ionization chamber.

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  Fig. 3 Geant4 Monte–Carlo simulation: proton energy deposit (a) and track length (b) in Poor Man’s Faraday Cup (PMFC).

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  Fig. 4 Poor Man’s Faraday Cup (PMFC) signal linearity check for proton beam dose (a) and dose rate (b).

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  Fig. 5 Range measurement using Poor Man’s Faraday Cup (PMFC) and Advanced Markus ion chamber.

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  Fig. 6 Relative signal based on the gaps between Poor Man’s Faraday Cup (PMFC) and Advanced Markus.

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  Fig. 7 Full-width-half-maximum (FWHM) of the proton beam as a function of depth.

Reference

References

1. Particle Therapy Co-Operative Group. Facilities in operation [Internet]. Particle Therapy Co-Operative Group,;[place unknown]: Available from: https://www.ptcog.ch/. cited 2022 Jul 20.

2. Lee SB. 2020; Proton therapy review: proton therapy from a medical. Prog Med Phys. 31:99–110. DOI: 10.14316/pmp.2020.31.3.99.

3. Citrin DE, Mitchell JB. 2017; Mechanisms of normal tissue injury from irradiation. Semin Radiat Oncol. 27:316–324. DOI: 10.1016/j.semradonc.2017.04.001. PMID: 28865514. PMCID: PMC5653270.

4. Wei S, Lin H, Choi JI, Press RH, Lazarev S, Kabarriti R, et al. 2022; FLASH radiotherapy using single-energy proton PBS transmission beams for hypofractionation liver cancer: dose and dose rate quantification. Front Oncol. 11:813063. DOI: 10.3389/fonc.2021.813063. PMID: 35096620. PMCID: PMC8794777.

5. Ashraf MR, Rahman M, Zhang R, Williams BB, Gladstone DJ, Pogue BW, et al. 2020; Dosimetry for FLASH radiotherapy: a review of tools and the role of radioluminescence and Cherenkov emission. Front Phys. 8:328. DOI: 10.3389/fphy.2020.00328.

6. Cascio EW, Gottschalk B. 2009. A simplified vacuumless Faraday cup for the experimental beamline at the Francis H. Burr proton therapy center. Paper presented at: 2009 IEEE Radiation Effects Data Workshop; 2009 Jul 20-24; Quebec, Canada. DOI: 10.1109/REDW.2009.5336294.

7. International Atomic Energy Agency (IAEA). 2000. Absorbed dose determination in external beam radiotherapy. IAEA;Vienna: p. 398. DOI: 10.3389/fphy.2020.00328.

8. Vadrucci M, Esposito G, Ronsivalle C, Cherubini R, Marracino F, Montereali RM, et al. 2015; Calibration of GafChromic EBT3 for absorbed dose measurements in 5 MeV proton beam and (60)Co γ-rays. Med Phys. 42:4678–4684. DOI: 10.1118/1.4926558. PMID: 26233195.