Current delivery limitations of proton PBS for FLASH

Wei Zou; Eric S. Diffenderfer; Keith A. Cengel; Michele M. Kim; Steve Avery; Joshua Konzer; Yongliang Cai; Paul Boisseu; Kan Ota; Lingshu Yin; Rodney Wiersma; David J. Carlson; Yi Fan; Theresa M. Busch; Costas Koumenis; Alexander Lin; James M. Metz; Boon Keng K. Teo; Lei Dong

doi:10.1016/j.radonc.2020.11.002

Current delivery limitations of proton PBS for FLASH

Wei Zou, Eric S. Diffenderfer, Keith A. Cengel, Michele M. Kim, Steve Avery, Joshua Konzer, Yongliang Cai, Paul Boisseu, Kan Ota, Lingshu Yin, Rodney Wiersma, David J. Carlson, Yi Fan, Theresa M. Busch, Costas Koumenis, Alexander Lin, James M. Metz, Boon Keng K. Teo, Lei Dong

Research output: Contribution to journal › Article › peer-review

Abstract

Purpose: Proton Pencil Beam Scanning (PBS) is an attractive solution to realize the advantageous normal tissue sparing elucidated from FLASH high dose rates. The mechanics of PBS spot delivery will impose limitations on the effective field dose rate for PBS. Methods: This study incorporates measurements from clinical and FLASH research beams on uniform single energy and the spread-out Bragg Peak PBS fields to extrapolate the PBS dose rate to high cyclotron beam currents 350, 500, and 800 nA. The impact of the effective field dose rate from cyclotron current, spot spacing, slew time and field size were studied. Results: When scanning magnet slew time and energy switching time are not considered, single energy effective field FLASH dose rate (≥40 Gy/s) can only be achieved with less than 4 × 4 cm² fields when the cyclotron output current is above 500 nA. Slew time and energy switching time remain the limiting factors for achieving high effective dose rate of the field. The dose rate-time structures were obtained. The amount of the total dose delivered at the FLASH dose rate in single energy layer and volumetric field was also studied. Conclusion: It is demonstrated that while it is difficult to achieve FLASH dose rate for a large field or in a volume, local FLASH delivery to certain percentage of the total dose is possible. With further understanding of the FLASH radiobiological mechanism, this study could provide guidance to adapt current clinical multi-field proton PBS delivery practice for FLASH proton radiotherapy.

Original language	English (US)
Pages (from-to)	212-218
Number of pages	7
Journal	Radiotherapy and Oncology
Volume	155
DOIs	https://doi.org/10.1016/j.radonc.2020.11.002
State	Published - Feb 2021
Externally published	Yes

Keywords

Dose rate
FLASH
Proton PBS

ASJC Scopus subject areas

Hematology
Oncology
Radiology Nuclear Medicine and imaging

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10.1016/j.radonc.2020.11.002

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Zou, W., Diffenderfer, E. S., Cengel, K. A., Kim, M. M., Avery, S., Konzer, J., Cai, Y., Boisseu, P., Ota, K., Yin, L., Wiersma, R., Carlson, D. J., Fan, Y., Busch, T. M., Koumenis, C., Lin, A., Metz, J. M., Teo, B. K. K., & Dong, L. (2021). Current delivery limitations of proton PBS for FLASH. Radiotherapy and Oncology, 155, 212-218. https://doi.org/10.1016/j.radonc.2020.11.002

@article{12e48fc3cc394e86a734985770d9b688,

title = "Current delivery limitations of proton PBS for FLASH",

abstract = "Purpose: Proton Pencil Beam Scanning (PBS) is an attractive solution to realize the advantageous normal tissue sparing elucidated from FLASH high dose rates. The mechanics of PBS spot delivery will impose limitations on the effective field dose rate for PBS. Methods: This study incorporates measurements from clinical and FLASH research beams on uniform single energy and the spread-out Bragg Peak PBS fields to extrapolate the PBS dose rate to high cyclotron beam currents 350, 500, and 800 nA. The impact of the effective field dose rate from cyclotron current, spot spacing, slew time and field size were studied. Results: When scanning magnet slew time and energy switching time are not considered, single energy effective field FLASH dose rate (≥40 Gy/s) can only be achieved with less than 4 × 4 cm2 fields when the cyclotron output current is above 500 nA. Slew time and energy switching time remain the limiting factors for achieving high effective dose rate of the field. The dose rate-time structures were obtained. The amount of the total dose delivered at the FLASH dose rate in single energy layer and volumetric field was also studied. Conclusion: It is demonstrated that while it is difficult to achieve FLASH dose rate for a large field or in a volume, local FLASH delivery to certain percentage of the total dose is possible. With further understanding of the FLASH radiobiological mechanism, this study could provide guidance to adapt current clinical multi-field proton PBS delivery practice for FLASH proton radiotherapy.",

keywords = "Dose rate, FLASH, Proton PBS",

author = "Wei Zou and Diffenderfer, {Eric S.} and Cengel, {Keith A.} and Kim, {Michele M.} and Steve Avery and Joshua Konzer and Yongliang Cai and Paul Boisseu and Kan Ota and Lingshu Yin and Rodney Wiersma and Carlson, {David J.} and Yi Fan and Busch, {Theresa M.} and Costas Koumenis and Alexander Lin and Metz, {James M.} and Teo, {Boon Keng K.} and Lei Dong",

note = "Publisher Copyright: {\textcopyright} 2020 Elsevier B.V.",

year = "2021",

month = feb,

doi = "10.1016/j.radonc.2020.11.002",

language = "English (US)",

volume = "155",

pages = "212--218",

journal = "Radiotherapy and Oncology",

issn = "0167-8140",

publisher = "Elsevier Ireland Ltd",

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TY - JOUR

T1 - Current delivery limitations of proton PBS for FLASH

AU - Zou, Wei

AU - Diffenderfer, Eric S.

AU - Cengel, Keith A.

AU - Kim, Michele M.

AU - Avery, Steve

AU - Konzer, Joshua

AU - Cai, Yongliang

AU - Boisseu, Paul

AU - Ota, Kan

AU - Yin, Lingshu

AU - Wiersma, Rodney

AU - Carlson, David J.

AU - Fan, Yi

AU - Busch, Theresa M.

AU - Koumenis, Costas

AU - Lin, Alexander

AU - Metz, James M.

AU - Teo, Boon Keng K.

AU - Dong, Lei

PY - 2021/2

Y1 - 2021/2

N2 - Purpose: Proton Pencil Beam Scanning (PBS) is an attractive solution to realize the advantageous normal tissue sparing elucidated from FLASH high dose rates. The mechanics of PBS spot delivery will impose limitations on the effective field dose rate for PBS. Methods: This study incorporates measurements from clinical and FLASH research beams on uniform single energy and the spread-out Bragg Peak PBS fields to extrapolate the PBS dose rate to high cyclotron beam currents 350, 500, and 800 nA. The impact of the effective field dose rate from cyclotron current, spot spacing, slew time and field size were studied. Results: When scanning magnet slew time and energy switching time are not considered, single energy effective field FLASH dose rate (≥40 Gy/s) can only be achieved with less than 4 × 4 cm2 fields when the cyclotron output current is above 500 nA. Slew time and energy switching time remain the limiting factors for achieving high effective dose rate of the field. The dose rate-time structures were obtained. The amount of the total dose delivered at the FLASH dose rate in single energy layer and volumetric field was also studied. Conclusion: It is demonstrated that while it is difficult to achieve FLASH dose rate for a large field or in a volume, local FLASH delivery to certain percentage of the total dose is possible. With further understanding of the FLASH radiobiological mechanism, this study could provide guidance to adapt current clinical multi-field proton PBS delivery practice for FLASH proton radiotherapy.

AB - Purpose: Proton Pencil Beam Scanning (PBS) is an attractive solution to realize the advantageous normal tissue sparing elucidated from FLASH high dose rates. The mechanics of PBS spot delivery will impose limitations on the effective field dose rate for PBS. Methods: This study incorporates measurements from clinical and FLASH research beams on uniform single energy and the spread-out Bragg Peak PBS fields to extrapolate the PBS dose rate to high cyclotron beam currents 350, 500, and 800 nA. The impact of the effective field dose rate from cyclotron current, spot spacing, slew time and field size were studied. Results: When scanning magnet slew time and energy switching time are not considered, single energy effective field FLASH dose rate (≥40 Gy/s) can only be achieved with less than 4 × 4 cm2 fields when the cyclotron output current is above 500 nA. Slew time and energy switching time remain the limiting factors for achieving high effective dose rate of the field. The dose rate-time structures were obtained. The amount of the total dose delivered at the FLASH dose rate in single energy layer and volumetric field was also studied. Conclusion: It is demonstrated that while it is difficult to achieve FLASH dose rate for a large field or in a volume, local FLASH delivery to certain percentage of the total dose is possible. With further understanding of the FLASH radiobiological mechanism, this study could provide guidance to adapt current clinical multi-field proton PBS delivery practice for FLASH proton radiotherapy.

KW - Dose rate

KW - FLASH

KW - Proton PBS

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UR - http://www.scopus.com/inward/citedby.url?scp=85096852828&partnerID=8YFLogxK

U2 - 10.1016/j.radonc.2020.11.002

DO - 10.1016/j.radonc.2020.11.002

M3 - Article

C2 - 33186682

AN - SCOPUS:85096852828

SN - 0167-8140

VL - 155

SP - 212

EP - 218

JO - Radiotherapy and Oncology

JF - Radiotherapy and Oncology

ER -

Current delivery limitations of proton PBS for FLASH

Abstract

Keywords

ASJC Scopus subject areas

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