Journal article
Dosimetric delivery validation of dynamically collimated pencil beam scanning proton therapy
Physics in medicine & biology, Vol.68(5), 055003
02/20/2023
DOI: 10.1088/1361-6560/acb6cd
PMCID: PMC9940016
PMID: 36706460
Abstract
Pencil beam scanning (PBS) proton therapy target dose conformity can be improved with energy layer-specific collimation. One such collimator is the Dynamic Collimation System (DCS), which consists of four nickel trimmer blades that intercept the scanning beam as it approaches the lateral extent of the target. While the dosimetric benefits of the DCS have been demonstrated through computational treatment planning studies, there has yet to be experimental verification of these benefits for composite multi-energy layer fields. The objective of this work is to dosimetrically characterize and experimentally validate the delivery of dynamically collimated proton therapy with the DCS equipped to a clinical PBS system.
Optimized single field, uniform dose treatment plans for 3x3x3 cm3 target volumes were generated using Monte Carlo dose calculations with depths ranging from 5 to 15 cm, trimmer-to-surface distances ranging from 5 to 18.15 cm, with and without a 4 cm thick polyethylene range shifter. Treatment plans were then delivered to a water phantom using a prototype DCS and an IBA dedicated nozzle system and measured with a Zebra multilayer ionization chamber, a MatriXX PT ionization chamber array, and Gafchromic™ EBT3 film.
For measurements made within the SOBPs, average 2D gamma pass rates exceeded 98.5% for the MatriXX PT and 96.5% for film at the 2%/2mm criterion across all measured uncollimated and collimated plans, respectively. For verification of the penumbra width reduction with collimation, film agreed with Monte Carlo with differences within 0.3 mm on average compared to 0.9 mm for the MatriXX PT.
We have experimentally verified the delivery of DCS-collimated fields using a clinical PBS system and commonly available dosimeters and have also identified potential weaknesses for dosimeters subject to steep dose gradients.
Details
- Title: Subtitle
- Dosimetric delivery validation of dynamically collimated pencil beam scanning proton therapy
- Creators
- Nicholas P Nelson - University of Wisconsin–MadisonWesley S Culberson - University of Wisconsin–MadisonDaniel E Hyer - University of IowaTheodore J Geoghegan - University of Iowa Roy J and Lucille A Carver College of Medicine, 200 Hawkins Drive, Iowa City, Iowa, 52242-1101, UNITED STATESKaustubh A Patwardhan - University of IowaBlake R Smith - University of IowaRyan T Flynn - Department of Radiation Oncology, University of Iowa, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, Iowa, 52242, UNITED STATESJen Yu - Baptist Health South FloridaAlonso N Gutiérrez - Baptist Health South FloridaPatrick M Hill - University of Wisconsin–Madison
- Resource Type
- Journal article
- Publication Details
- Physics in medicine & biology, Vol.68(5), 055003
- DOI
- 10.1088/1361-6560/acb6cd
- PMID
- 36706460
- PMCID
- PMC9940016
- NLM abbreviation
- Phys Med Biol
- ISSN
- 0031-9155
- eISSN
- 1361-6560
- Grant note
- DOI: 10.13039/100000054, name: National Cancer Institute, award: R37CA226518
- Language
- English
- Electronic publication date
- 01/27/2023
- Date published
- 02/20/2023
- Academic Unit
- Roy J. Carver Department of Biomedical Engineering; Radiation Oncology
- Record Identifier
- 9984363380102771
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