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Bennett LC, Hyer DE, Vu J, Patwardhan K, Erhart K, Gutierrez AN, Pons E, Jensen E, Ubau M, Zapata J, Wroe A, Wake K, Nelson NP, Culberson WS, Smith BR, Hill PM, Flynn RT. Patient-specific quality assurance of dynamically-collimated proton therapy treatment plans. Med Phys 2024; 51:5901-5910. [PMID: 38977285 DOI: 10.1002/mp.17295] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2024] [Revised: 05/16/2024] [Accepted: 06/10/2024] [Indexed: 07/10/2024] Open
Abstract
BACKGROUND The dynamic collimation system (DCS) provides energy layer-specific collimation for pencil beam scanning (PBS) proton therapy using two pairs of orthogonal nickel trimmer blades. While excellent measurement-to-calculation agreement has been demonstrated for simple cube-shaped DCS-trimmed dose distributions, no comparison of measurement and dose calculation has been made for patient-specific treatment plans. PURPOSE To validate a patient-specific quality assurance (PSQA) process for DCS-trimmed PBS treatment plans and evaluate the agreement between measured and calculated dose distributions. METHODS Three intracranial patient cases were considered. Standard uncollimated PBS and DCS-collimated treatment plans were generated for each patient using the Astroid treatment planning system (TPS). Plans were recalculated in a water phantom and delivered at the Miami Cancer Institute (MCI) using an Ion Beam Applications (IBA) dedicated nozzle system and prototype DCS. Planar dose measurements were acquired at two depths within low-gradient regions of the target volume using an IBA MatriXX ion chamber array. RESULTS Measured and calculated dose distributions were compared using 2D gamma analysis with 3%/3 mm criteria and low dose threshold of 10% of the maximum dose. Median gamma pass rates across all plans and measurement depths were 99.0% (PBS) and 98.3% (DCS), with a minimum gamma pass rate of 88.5% (PBS) and 91.2% (DCS). CONCLUSIONS The PSQA process has been validated and experimentally verified for DCS-collimated PBS. Dosimetric agreement between the measured and calculated doses was demonstrated to be similar for DCS-collimated PBS to that achievable with noncollimated PBS.
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Affiliation(s)
- Laura C Bennett
- Roy J. Carver Department of Biomedical Engineering, University of Iowa, 5601 Seamans Center for the Engineering Arts and Sciences, Iowa City, Iowa, USA
| | - Daniel E Hyer
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, Iowa City, Iowa, USA
| | - Justin Vu
- Roy J. Carver Department of Biomedical Engineering, University of Iowa, 5601 Seamans Center for the Engineering Arts and Sciences, Iowa City, Iowa, USA
| | - Kaustubh Patwardhan
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, Iowa City, Iowa, USA
| | | | - Alonso N Gutierrez
- Department of Radiation Oncology, Miami Cancer Institute, Baptist Health South Florida, Miami, Florida, USA
| | - Eduardo Pons
- Department of Radiation Oncology, Miami Cancer Institute, Baptist Health South Florida, Miami, Florida, USA
| | - Eric Jensen
- Ion Beam Applications S.A., R&D Proton Therapy, Louvain-La-Neuve, Belgium
| | - Manual Ubau
- Ion Beam Applications S.A., R&D Proton Therapy, Louvain-La-Neuve, Belgium
| | - Julio Zapata
- Ion Beam Applications S.A., R&D Proton Therapy, Louvain-La-Neuve, Belgium
| | - Andrew Wroe
- Department of Radiation Oncology, Miami Cancer Institute, Baptist Health South Florida, Miami, Florida, USA
| | - Karsten Wake
- Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin, USA
| | - Nicholas P Nelson
- Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin, USA
- Department of Radiation Oncology, Huntsman Cancer Institute, University of Utah, Salt Lake City, Utah, USA
| | - Wesley S Culberson
- Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin, USA
| | - Blake R Smith
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, Iowa City, Iowa, USA
| | - Patrick M Hill
- Department of Human Oncology, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin, USA
| | - Ryan T Flynn
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, Iowa City, Iowa, USA
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Feng H, Holmes JM, Vora SA, Stoker JB, Bues M, Wong WW, Sio TS, Foote RL, Patel SH, Shen J, Liu W. Modelling small block aperture in an in-house developed GPU-accelerated Monte Carlo-based dose engine for pencil beam scanning proton therapy. Phys Med Biol 2024; 69:10.1088/1361-6560/ad0b64. [PMID: 37944480 PMCID: PMC11009986 DOI: 10.1088/1361-6560/ad0b64] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Accepted: 11/09/2023] [Indexed: 11/12/2023]
Abstract
Purpose. To enhance an in-house graphic-processing-unit accelerated virtual particle (VP)-based Monte Carlo (MC) proton dose engine (VPMC) to model aperture blocks in both dose calculation and optimization for pencil beam scanning proton therapy (PBSPT)-based stereotactic radiosurgery (SRS).Methods and materials. A module to simulate VPs passing through patient-specific aperture blocks was developed and integrated in VPMC based on simulation results of realistic particles (primary protons and their secondaries). To validate the aperture block module, VPMC was first validated by an opensource MC code, MCsquare, in eight water phantom simulations with 3 cm thick brass apertures: four were with aperture openings of 1, 2, 3, and 4 cm without a range shifter, while the other four were with same aperture opening configurations with a range shifter of 45 mm water equivalent thickness. Then, VPMC was benchmarked with MCsquare and RayStation MC for 10 patients with small targets (average volume 8.4 c.c. with range of 0.4-43.3 c.c.). Finally, 3 typical patients were selected for robust optimization with aperture blocks using VPMC.Results. In the water phantoms, 3D gamma passing rate (2%/2 mm/10%) between VPMC and MCsquare was 99.71 ± 0.23%. In the patient geometries, 3D gamma passing rates (3%/2 mm/10%) between VPMC/MCsquare and RayStation MC were 97.79 ± 2.21%/97.78 ± 1.97%, respectively. Meanwhile, the calculation time was drastically decreased from 112.45 ± 114.08 s (MCsquare) to 8.20 ± 6.42 s (VPMC) with the same statistical uncertainties of ~0.5%. The robustly optimized plans met all the dose-volume-constraints (DVCs) for the targets and OARs per our institutional protocols. The mean calculation time for 13 influence matrices in robust optimization by VPMC was 41.6 s and the subsequent on-the-fly 'trial-and-error' optimization procedure took only 71.4 s on average for the selected three patients.Conclusion. VPMC has been successfully enhanced to model aperture blocks in dose calculation and optimization for the PBSPT-based SRS.
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Affiliation(s)
- Hongying Feng
- College of Mechanical and Power Engineering, China Three Gorges University, Yichang, Hubei 443002, People’s Republic of China
- Department of Radiation Oncology, Mayo Clinic, Phoenix, AZ 85054, United States of America
- Department of Radiation Oncology, Guangzhou Concord Cancer Center, Guangzhou, Guangdong, 510555, People’s Republic of China
| | - Jason M Holmes
- Department of Radiation Oncology, Mayo Clinic, Phoenix, AZ 85054, United States of America
| | - Sujay A Vora
- Department of Radiation Oncology, Mayo Clinic, Phoenix, AZ 85054, United States of America
| | - Joshua B Stoker
- Department of Radiation Oncology, Mayo Clinic, Phoenix, AZ 85054, United States of America
| | - Martin Bues
- Department of Radiation Oncology, Mayo Clinic, Phoenix, AZ 85054, United States of America
| | - William W Wong
- Department of Radiation Oncology, Mayo Clinic, Phoenix, AZ 85054, United States of America
| | - Terence S Sio
- Department of Radiation Oncology, Mayo Clinic, Phoenix, AZ 85054, United States of America
| | - Robert L Foote
- Department of Radiation Oncology, Mayo Clinic, Rochester, MN 55902, United States of America
| | - Samir H Patel
- Department of Radiation Oncology, Mayo Clinic, Phoenix, AZ 85054, United States of America
| | - Jiajian Shen
- Department of Radiation Oncology, Mayo Clinic, Phoenix, AZ 85054, United States of America
| | - Wei Liu
- Department of Radiation Oncology, Mayo Clinic, Phoenix, AZ 85054, United States of America
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Bennett LC, Hyer DE, Erhart K, Nelson NP, Culberson WS, Smith BR, Hill PM, Flynn RT. PETRA: A pencil beam trimming algorithm for analytical proton therapy dose calculations with the dynamic collimation system. Med Phys 2023; 50:7263-7280. [PMID: 37370239 PMCID: PMC10751389 DOI: 10.1002/mp.16559] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Revised: 05/28/2023] [Accepted: 05/30/2023] [Indexed: 06/29/2023] Open
Abstract
BACKGROUND The Dynamic Collimation System (DCS) has been shown to produce superior treatment plans to uncollimated pencil beam scanning (PBS) proton therapy using an in-house treatment planning system (TPS) designed for research. Clinical implementation of the DCS requires the development and benchmarking of a rigorous dose calculation algorithm that accounts for pencil beam trimming, performs monitor unit calculations to produce deliverable plans at all beam energies, and is ideally implemented with a commercially available TPS. PURPOSE To present an analytical Pencil bEam TRimming Algorithm (PETRA) for the DCS, with and without its range shifter, implemented in the Astroid TPS (.decimal, Sanford, Florida, USA). MATERIALS PETRA was derived by generalizing an existing pencil beam dose calculation model to account for the DCS-specific effects of lateral penumbra blurring due to the nickel trimmers in two different planes, integral depth dose variation due to the trimming process, and the presence and absence of the range shifter. Tuning parameters were introduced to enable agreement between PETRA and a measurement-validated Dynamic Collimation Monte Carlo (DCMC) model of the Miami Cancer Institute's IBA Proteus Plus system equipped with the DCS. Trimmer position, spot position, beam energy, and the presence or absence of a range shifter were all used as variables for the characterization of the model. The model was calibrated for pencil beam monitor unit calculations using procedures specified by International Atomic Energy Agency Technical Report Series 398 (IAEA TRS-398). RESULTS The integral depth dose curves (IDDs) for energies between 70 MeV and 160 MeV among all simulated trimmer combinations, with and without the ranger shifter, agreed between PETRA and DCMC at the 1%/1 mm 1-D gamma criteria for 99.99% of points. For lateral dose profiles, the median 2-D gamma pass rate for all profiles at 1.5%/1.5 mm was 99.99% at the water phantom surface, plateau, and Bragg peak depths without the range shifter and at the surface and Bragg peak depths with the range shifter. The minimum 1.5%/1.5 mm gamma pass rates for the 2-D profiles at the water phantom surface without and with the range shifter were 98.02% and 97.91%, respectively, and, at the Bragg peak, the minimum pass rates were 97.80% and 97.5%, respectively. CONCLUSION The PETRA model for DCS dose calculations was successfully defined and benchmarked for use in a commercially available TPS.
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Affiliation(s)
- Laura C. Bennett
- Roy J. Carver Department of Biomedical Engineering, University of Iowa, 5601 Seamans Center for the Engineering Arts and Sciences, Iowa City, IA, 52242, USA
| | - Daniel E. Hyer
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA, 52242, USA
| | - Kevin Erhart
- .decimal LLC, 121 Central Park Pl, Sanford, FL, 32771, USA
| | - Nicholas P. Nelson
- Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin, 1111 Highland Avenue, Madison, WI, 53705, USA
| | - Wesley S. Culberson
- Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin, 1111 Highland Avenue, Madison, WI, 53705, USA
| | - Blake R. Smith
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA, 52242, USA
| | - Patrick M. Hill
- Department of Human Oncology, School of Medicine and Public Health, University of Wisconsin, 600 Highland Avenue, Madison, WI, 53792, USA
| | - Ryan T. Flynn
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA, 52242, USA
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Nelson NP, Culberson WS, Hyer DE, Geoghegan TJ, Patwardhan KA, Smith BR, Flynn RT, Gutiérrez AN, Boland T, Hill PM. Integration and dosimetric validation of a dynamic collimation system for pencil beam scanning proton therapy. Biomed Phys Eng Express 2023; 9:10.1088/2057-1976/ad02ff. [PMID: 37832529 PMCID: PMC11128250 DOI: 10.1088/2057-1976/ad02ff] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Accepted: 10/13/2023] [Indexed: 10/15/2023]
Abstract
Objective.To integrate a Dynamic Collimation System (DCS) into a pencil beam scanning (PBS) proton therapy system and validate its dosimetric impact.Approach.Uncollimated and collimated treatment fields were developed for clinically relevant targets using an in-house treatment plan optimizer and an experimentally validated Monte Carlo model of the DCS and IBA dedicated nozzle (DN) system. The dose reduction induced by the DCS was quantified by calculating the mean dose in 10- and 30-mm two-dimensional rinds surrounding the target. A select number of plans were then used to experimentally validate the mechanical integration of the DCS and beam scanning controller system through measurements with the MatriXX-PT ionization chamber array and EBT3 film. Absolute doses were verified at the central axis at various depths using the IBA MatriXX-PT and PPC05 ionization chamber.Main results.Simulations demonstrated a maximum mean dose reduction of 12% for the 10 mm rind region and 45% for the 30 mm rind region when utilizing the DCS. Excellent agreement was observed between Monte Carlo simulations, EBT3 film, and MatriXX-PT measurements, with gamma pass rates exceeding 94.9% for all tested plans at the 3%/2 mm criterion. Absolute central axis doses showed an average verification difference of 1.4% between Monte Carlo and MatriXX-PT/PPC05 measurements.Significance.We have successfully dosimetrically validated the delivery of dynamically collimated proton therapy for clinically relevant delivery patterns and dose distributions with the DCS. Monte Carlo simulations were employed to assess dose reductions and treatment planning considerations associated with the DCS.
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Affiliation(s)
- Nicholas P Nelson
- Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin—Madison, 1111 Highland Avenue, Madison, WI, 53705, United States of America
| | - Wesley S Culberson
- Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin—Madison, 1111 Highland Avenue, Madison, WI, 53705, United States of America
| | - Daniel E Hyer
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA, 52242, United States of America
| | - Theodore J Geoghegan
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA, 52242, United States of America
| | - Kaustubh A Patwardhan
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA, 52242, United States of America
| | - Blake R Smith
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA, 52242, United States of America
| | - Ryan T Flynn
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA, 52242, United States of America
| | - Alonso N Gutiérrez
- Department of Radiation Oncology, Miami Cancer Institute, Baptist Health South Florida, 8900 N. Kendall Drive, Miami, FL, 331765, United States of America
| | | | - Patrick M Hill
- Department of Human Oncology, School of Medicine and Public Health, University of Wisconsin—Madison, 600 Highland Avenue, Madison, WI, 53792, United States of America
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5
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Geoghegan T, Patwardhan K, Ying Q, Nelson N, Yu J, Gutierrez A, Hill P, Flynn R, Hyer D. Design, testing and characterization of a proton central axis alignment device for the dynamic collimation system. Biomed Phys Eng Express 2023; 9:10.1088/2057-1976/acdad5. [PMID: 37267924 PMCID: PMC10330655 DOI: 10.1088/2057-1976/acdad5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Accepted: 06/02/2023] [Indexed: 06/04/2023]
Abstract
Objective. Proton therapy conformity has improved over the years by evolving from passive scattering to spot scanning delivery technologies with smaller proton beam spot sizes. Ancillary collimation devices, such the Dynamic Collimation System (DCS), further improves high dose conformity by sharpening the lateral penumbra. However, as spot sizes are reduced, collimator positional errors play a significant impact on the dose distributions and hence accurate collimator to radiation field alignment is critical.Approach. The purpose of this work was to develop a system to align and verify coincidence between the center of the DCS and the proton beam central axis. The Central Axis Alignment Device (CAAD) is composed of a camera and scintillating screen-based beam characterization system. Within a light-tight box, a 12.3-megapixel camera monitors a P43/Gadox scintillating screen via a 45° first-surface mirror. When a collimator trimmer of the DCS is placed in the uncalibrated center of the field, the proton radiation beam continuously scans a 7×7 cm2square field across the scintillator and collimator trimmer while a 7 s exposure is acquired. From the relative positioning of the trimmer to the radiation field, the true center of the radiation field can be calculated.Main results.The CAAD can calculate the offset between the proton beam radiation central axis and the DCS central axis within 0.054 mm accuracy and 0.075 mm reproducibility.Significance.Using the CAAD, the DCS is now able to be aligned accurately to the proton radiation beam central axis and no longer relies on an x-ray source in the gantry head which is only validated to within 1.0 mm of the proton beam.
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Affiliation(s)
- Theodore Geoghegan
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA, 52242, United States of America
| | - Kaustubh Patwardhan
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA, 52242, United States of America
| | - Qi Ying
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA, 52242, United States of America
| | - Nicholas Nelson
- Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin-Madison, 1111 Highland Avenue, Madison, WI, 53705, United States of America
| | - Jen Yu
- Department of Radiation Oncology, Miami Cancer Institute, Baptist Health South Florida, 8900 N. Kendall Drive, Miami, FL, 33176, United States of America
| | - Alonso Gutierrez
- Department of Radiation Oncology, Miami Cancer Institute, Baptist Health South Florida, 8900 N. Kendall Drive, Miami, FL, 33176, United States of America
| | - Patrick Hill
- Department of Human Oncology, School of Medicine and Public Health, University of Wisconsin-Madison, 600 Highland Avenue, Madison, WI, 53792, United States of America
| | - Ryan Flynn
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA, 52242, United States of America
| | - Daniel Hyer
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA, 52242, United States of America
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6
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Nelson NP, Culberson WS, Hyer DE, Geoghegan TJ, Patwardhan KA, Smith BR, Flynn RT, Yu J, Gutiérrez AN, Hill PM. Dosimetric delivery validation of dynamically collimated pencil beam scanning proton therapy. Phys Med Biol 2023; 68:055003. [PMID: 36706460 PMCID: PMC9940016 DOI: 10.1088/1361-6560/acb6cd] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Accepted: 01/27/2023] [Indexed: 01/28/2023]
Abstract
Objective. 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.Approach. Optimized single field, uniform dose treatment plans for 3 × 3 × 3 cm3target 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.Main results. 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%/2 mm 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.Significance. 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.
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Affiliation(s)
- Nicholas P Nelson
- Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin—Madison, 1111 Highland Avenue, Madison, WI, 53705, United States of America,Author to whom any correspondence should be addressed
| | - Wesley S Culberson
- Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin—Madison, 1111 Highland Avenue, Madison, WI, 53705, United States of America
| | - Daniel E Hyer
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA, 52242, United States of America
| | - Theodore J Geoghegan
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA, 52242, United States of America
| | - Kaustubh A Patwardhan
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA, 52242, United States of America
| | - Blake R Smith
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA, 52242, United States of America
| | - Ryan T Flynn
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA, 52242, United States of America
| | - Jen Yu
- Department of Radiation Oncology, Miami Cancer Institute, Baptist Health South Florida, 8900 N. Kendall Drive, Miami, FL, 33176, United States of America
| | - Alonso N Gutiérrez
- Department of Radiation Oncology, Miami Cancer Institute, Baptist Health South Florida, 8900 N. Kendall Drive, Miami, FL, 33176, United States of America
| | - Patrick M Hill
- Department of Human Oncology, School of Medicine and Public Health, University of Wisconsin—Madison, 600 Highland Avenue, Madison, WI, 53792, United States of America
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Behrends C, Bäumer C, Verbeek NG, Wulff J, Timmermann B. Optimization of proton pencil beam positioning in collimated fields. Med Phys 2023; 50:2540-2551. [PMID: 36609847 DOI: 10.1002/mp.16209] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Revised: 12/24/2022] [Accepted: 12/26/2022] [Indexed: 01/08/2023] Open
Abstract
BACKGROUND The addition of static or dynamic collimator systems to the pencil beam scanning delivery technique increases the number of options for lateral field shaping. The collimator shape needs to be optimized together with the intensity modulation of spots. PURPOSE To minimize the proton field's lateral penumbra by investigating the fundamental relations between spot and collimating aperture edge position. METHODS Analytical approaches describing the effect of spot position on the resulting spot profile are presented. The theoretical description is then compared with Monte Carlo simulations in TOPAS and in the RayStation treatment planning system, as well as with radiochromic film measurements at a clinical proton therapy facility. In the model, one single spot profile is analyzed for various spot positions in air. Further, irradiation setups in water with different energies, the combination with a range shifter, and two-dimensional proton fields were investigated in silico. RESULTS The further the single spot is placed beyond the collimating aperture edge ('overscanning'), the sharper the relative lateral dose fall-off and thus the lateral penumbra. Overscanning up to 5 mm $5\,\text{mm}$ reduced the lateral penumbra by about 20% on average after a propagation of 13 cm $13\,\text{cm}$ in air. This benefit from overscanning is first predicted by the analytical proofs and later verified by simulations and measurements. Corresponding analyses in water confirm the benefit in lateral penumbra with spot position optimization as observed theoretically and in air. The combination of spot overscanning with fluence modulation facilitated an additional improvement. CONCLUSIONS The lateral penumbra of single spots in collimated scanned proton fields can be improved by the method of spot overscanning. This suggests a better sparing of proximal organs at risk in smaller water depths at higher energies, especially in the plateau of the depth dose distribution. All in all, spot overscanning in collimated scanned proton fields offers particular potential in combination with techniques such as fluence modulation or dynamic collimation for optimizing the lateral penumbra to spare normal tissue.
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Affiliation(s)
- Carina Behrends
- West German Proton Therapy Centre Essen (WPE), Essen, Germany.,Department of Physics, TU Dortmund University, Dortmund, Germany.,West German Cancer Centre (WTZ), University Hospital Essen, Essen, Germany
| | - Christian Bäumer
- West German Proton Therapy Centre Essen (WPE), Essen, Germany.,Department of Physics, TU Dortmund University, Dortmund, Germany.,West German Cancer Centre (WTZ), University Hospital Essen, Essen, Germany.,German Cancer Consortium (DKTK), Heidelberg, Germany
| | - Nico Gerd Verbeek
- West German Proton Therapy Centre Essen (WPE), Essen, Germany.,West German Cancer Centre (WTZ), University Hospital Essen, Essen, Germany.,Faculty of Medicine, University of Duisburg-Essen, Essen, Germany
| | - Jörg Wulff
- West German Proton Therapy Centre Essen (WPE), Essen, Germany.,West German Cancer Centre (WTZ), University Hospital Essen, Essen, Germany
| | - Beate Timmermann
- West German Proton Therapy Centre Essen (WPE), Essen, Germany.,West German Cancer Centre (WTZ), University Hospital Essen, Essen, Germany.,German Cancer Consortium (DKTK), Heidelberg, Germany.,Faculty of Medicine, University of Duisburg-Essen, Essen, Germany.,Department of Particle Therapy, University Hospital Essen, Essen, Germany
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8
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Holmes J, Shen J, Patel SH, Wong WW, Foote RL, Bues M, Liu W. Collimating individual beamlets in pencil beam scanning proton therapy, a dosimetric investigation. Front Oncol 2022; 12:1031340. [PMID: 36439436 PMCID: PMC9692234 DOI: 10.3389/fonc.2022.1031340] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Accepted: 10/27/2022] [Indexed: 03/26/2024] Open
Abstract
The purpose of this work is to investigate collimating individual proton beamlets from a dosimetric perspective and to introduce a new device concept, the spot scanning aperture (SSA). The SSA consists of a thin aperture with a small cylindrical opening attached to a robotics system, which allows the aperture to follow and align with individual beamlets during spot delivery. Additionally, a range shifter is incorporated (source-side) for treating shallow depths. Since the SSA trims beamlets spot by spot, the patient-facing portion of the device only needs to be large enough to trim a single proton beamlet. The SSA has been modelled in an open-source Monte-Carlo-based dose engine (MCsquare) to characterize its dosimetric properties in water at depths between 0 and 10 cm while varying the following parameters: the aperture material, thickness, distance to the water phantom, distance between the aperture and attached range shifter, and the aperture opening radius. Overall, the SSA greatly reduced spot sizes for all the aperture opening radii that were tested (1 - 4 mm), especially in comparison with the extended range shifter (ranger shifter placed at 30 cm from patient); greater than 50% when placed less than 10 cm away from the patient at depths in water less than 50 mm. The peak to entrance dose ratio and linear energy transfer was found to depend on the thickness of the aperture and therefore the aperture material. Neutron production rates were also investigated and discussed.
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Affiliation(s)
- Jason Holmes
- Department of Radiation Oncology, Mayo Clinic, Phoenix, AZ, United States
| | - Jiajian Shen
- Department of Radiation Oncology, Mayo Clinic, Phoenix, AZ, United States
| | - Samir H. Patel
- Department of Radiation Oncology, Mayo Clinic, Phoenix, AZ, United States
| | - William W. Wong
- Department of Radiation Oncology, Mayo Clinic, Phoenix, AZ, United States
| | - Robert L. Foote
- Department of Radiation Oncology, Mayo Clinic, Rochester, MN, United States
| | - Martin Bues
- Department of Radiation Oncology, Mayo Clinic, Phoenix, AZ, United States
| | - Wei Liu
- Department of Radiation Oncology, Mayo Clinic, Phoenix, AZ, United States
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Deraniyagala R, Ding X, Alonso-Basanta M, Li T, Rong Y. It is beneficial to invest resources to implement proton intracranial SRS. J Appl Clin Med Phys 2022; 23:e13701. [PMID: 35713887 PMCID: PMC9278676 DOI: 10.1002/acm2.13701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Accepted: 06/02/2022] [Indexed: 11/06/2022] Open
Affiliation(s)
- Rohan Deraniyagala
- Department of Radiation Oncology, William Beaumont Hospital, Royal Oak, Michigan, USA
| | - Xuanfeng Ding
- Department of Radiation Oncology, William Beaumont Hospital, Royal Oak, Michigan, USA
| | - Michelle Alonso-Basanta
- Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Taoran Li
- Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Yi Rong
- Department of Radiation Oncology, Mayo Clinic Arizona, Phoenix, Arizona, USA
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10
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Chang S, Liu G, Zhao L, Zheng W, Yan D, Chen P, Li X, Yang K, Deraniyagala R, Stevens C, Grills I, Chinnaiyan P, Li X, Ding X. Redefine the Role of Spot-Scanning Proton Beam Therapy for the Single Brain Metastasis Stereotactic Radiosurgery. Front Oncol 2022; 12:804036. [PMID: 35664795 PMCID: PMC9160604 DOI: 10.3389/fonc.2022.804036] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Accepted: 04/14/2022] [Indexed: 12/30/2022] Open
Abstract
Purpose To explore the role of using Pencil Beam Scanning (PBS) proton beam therapy in single lesion brain stereotactic radiosurgery (SRS), we developed and validated a dosimetric in silico model to assist in the selection of an optimal treatment approach among the conventional Volumetric Modulated Arc Therapy (VMAT), Intensity Modulated Proton Therapy (IMPT) and Spot-scanning Proton Arc (SPArc). Material and Methods A patient’s head CT data set was used as an in silico model. A series of targets (volume range from 0.3 cc to 33.03 cc) were inserted in the deep central and peripheral region, simulating targets with different sizes and locations. Three planning groups: IMPT, VMAT, and SPArc were created for dosimetric comparison purposes and a decision tree was built based on this in silico model. Nine patients with single brain metastases were retrospectively selected for validation. Multiple dosimetric metrics were analyzed to assess the plan quality, such as dose Conformity Index (CI) (ratio of the target volume to 100% prescription isodose volume); R50 (ratio of 50% prescription isodose volume to the target volume); V12Gy (volume of brain tissue minus GTV receiving 12 Gy), and mean dose of the normal brain. Normal tissue complication probability (NTCP) of brain radionecrosis (RN) was calculated using the Lyman-Kutcher-Burman (LKB) model and total treatment delivery time was calculated. Six physicians from different institutions participated in the blind survey to evaluate the plan quality and rank their choices. Results The study showed that SPArc has a dosimetric advantage in the V12Gy and R50 with target volumes > 9.00 cc compared to VMAT and IMPT. A significant clinical benefit can be found in deep centrally located lesions larger than 20.00 cc using SPArc because of the superior dose conformity and mean dose reduction in healthy brain tissue. Nine retrospective clinical cases and the blind survey showed good agreement with the in silico dosimetric model and decision tree. Additionally, SPArc significantly reduced the treatment delivery time compared to VMAT (SPArc 184.46 ± 59.51s vs. VMAT: 1574.78 ± 213.65s). Conclusion The study demonstrated the feasibility of using Proton beam therapy for single brain metastasis patients utilizing the SPArc technique. At the current stage of technological development, VMAT remains the current standard modality of choice for single lesion brain SRS. The in silico dosimetric model and decision tree presented here could be used as a practical clinical decision tool to assist the selection of the optimal treatment modality among VMAT, IMPT, and SPArc in centers that have both photon and proton capabilities.
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Affiliation(s)
- Sheng Chang
- Department of Radiation Oncology, Renmin Hospital, Wuhan University, Wuhan, China
- Department of Radiation Oncology, Beaumont Health System, Royal Oak, MI, United States
| | - Gang Liu
- Department of Radiation Oncology, Beaumont Health System, Royal Oak, MI, United States
- Cancer Center, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Lewei Zhao
- Department of Radiation Oncology, Beaumont Health System, Royal Oak, MI, United States
| | - Weili Zheng
- Department of Radiation Oncology, Beaumont Health System, Royal Oak, MI, United States
| | - Di Yan
- Department of Radiation Oncology, Beaumont Health System, Royal Oak, MI, United States
| | - Peter Chen
- Department of Radiation Oncology, Beaumont Health System, Royal Oak, MI, United States
| | - Xiangpan Li
- Department of Radiation Oncology, Renmin Hospital, Wuhan University, Wuhan, China
| | - Kunyu Yang
- Cancer Center, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Rohan Deraniyagala
- Department of Radiation Oncology, Beaumont Health System, Royal Oak, MI, United States
| | - Craig Stevens
- Department of Radiation Oncology, Beaumont Health System, Royal Oak, MI, United States
| | - Inga Grills
- Department of Radiation Oncology, Beaumont Health System, Royal Oak, MI, United States
| | - Prakash Chinnaiyan
- Department of Radiation Oncology, Beaumont Health System, Royal Oak, MI, United States
| | - Xiaoqiang Li
- Department of Radiation Oncology, Beaumont Health System, Royal Oak, MI, United States
| | - Xuanfeng Ding
- Department of Radiation Oncology, Beaumont Health System, Royal Oak, MI, United States
- *Correspondence: Xuanfeng Ding,
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11
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Holmes J, Shen J, Shan J, Patrick CL, Wong WW, Foote RL, Patel SH, Bues M, Liu W. Technical Note: Evaluation and 2nd check of a commercial Monte Carlo dose engine for small-field apertures in pencil beam scanning proton therapy. Med Phys 2022; 49:3497-3506. [PMID: 35305269 DOI: 10.1002/mp.15604] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Revised: 02/19/2022] [Accepted: 03/02/2022] [Indexed: 11/10/2022] Open
Abstract
PURPOSE To evaluate the accuracy of the RayStation Monte Carlo dose engine (RayStation MC) in modeling small-field block apertures in proton pencil beam scanning. Furthermore, we evaluate the suitability of MCsquare as a 2nd check for RayStation MC. METHODS We have enhanced MCsquare to model block apertures. To test the accuracy of both RayStation MC and the newly enhanced MCsquare, we compare the dose predictions of each to in-water dose measurements obtained using diode detectors and radiochromic film. Nine brass apertures with openings of 1, 2, 3, 4, and 5 cm and either 2 cm or 4 cm thickness were used in the irradiation of a water phantom. Two measurement setups were used, one with a range shifter and 119.7 MeV proton beam energy and the other with no range shifter and 147 MeV proton beam energy. To further test the validity of RayStation MC and MCsquare in modeling block apertures and to evaluate MCsquare as a 2nd check tool, ten small-field (average target volume 8.3 cm3 ) patient treatment plans were calculated by each dose engine followed by a statistical comparison. RESULTS Comparing to the absolute dose measurements in water, RayStation MC differed by 1.2% ± 1.0% while MCsquare differed by -1.8% ± 3.7% in the plateau region of a pristine Bragg peak. Compared to the in-water film measurements, RayStation MC and MCsquare both performed well with an average 2D-3D gamma passing rate of 99.4% and 99.7% (3%/3mm) respectively. A t-test comparing the agreement with the film measurements between RayStation MC and MCsquare suggested that the relative spatial dose distributions calculated by MCsquare and RayStation MC were statistically indistinguishable. Directly comparing the dose calculations between MCsquare and RayStation MC over ten patients resulted in an average 3D-3D gamma passing rates of 98.5% (3%/3mm) and 94.1% (2%/2mm) respectively. CONCLUSION The validity of RayStation MC algorithm for use with patient-specific apertures has been expanded to include small apertures. MCsquare has been enhanced to model apertures and was found to be an adequate 2nd check of RayStation MC in this scenario. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Jason Holmes
- Department of Radiation Oncology, Mayo Clinic, Phoenix, AZ, 85054, USA
| | - Jiajian Shen
- Department of Radiation Oncology, Mayo Clinic, Phoenix, AZ, 85054, USA
| | - Jie Shan
- Department of Radiation Oncology, Mayo Clinic, Phoenix, AZ, 85054, USA
| | | | - William W Wong
- Department of Radiation Oncology, Mayo Clinic, Phoenix, AZ, 85054, USA
| | - Robert L Foote
- Department of Radiation Oncology, Mayo Clinic, Rochester, MN, 55902, USA
| | - Samir H Patel
- Department of Radiation Oncology, Mayo Clinic, Phoenix, AZ, 85054, USA
| | - Martin Bues
- Department of Radiation Oncology, Mayo Clinic, Phoenix, AZ, 85054, USA
| | - Wei Liu
- Department of Radiation Oncology, Mayo Clinic, Phoenix, AZ, 85054, USA
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Nelson NP, Culberson WS, Hyer DE, Smith BR, Flynn RT, Hill PM. Investigating aperture-based approximations to model a focused dynamic collimation system for pencil beam scanning proton therapy. Biomed Phys Eng Express 2022; 8:10.1088/2057-1976/ac525f. [PMID: 35130520 PMCID: PMC8917788 DOI: 10.1088/2057-1976/ac525f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Accepted: 02/07/2022] [Indexed: 11/12/2022]
Abstract
Purpose. The Dynamic Collimation System (DCS) is an energy layer-specific collimation device designed to reduce the lateral penumbra in pencil beam scanning proton therapy. The DCS consists of two pairs of nickel trimmers that rapidly and independently move and rotate to intercept the scanning proton beam and an integrated range shifter to treat targets less than 4 cm deep. This work examines the validity of a single aperture approximation to model the DCS, a commonly used approximation in commercial treatment planning systems, as well as higher-order aperture-based approximations for modeling DCS-collimated dose distributions.Methods. An experimentally validated TOPAS/Geant4-based Monte Carlo model of the DCS integrated with a beam model of the IBA pencil beam scanning dedicated nozzle was used to simulate DCS- and aperture-collimated 100 MeV beamlets and composite treatment plans. The DCS was represented by three different aperture approximations: a single aperture placed halfway between the upper and lower trimmer planes, two apertures located at the upper and lower trimmer planes, and four apertures, located at both the upstream and downstream faces of each pair of trimmers. Line profiles and three-dimensional regions of interest were used to evaluate the validity and limitations of the aperture approximations investigated.Results. For pencil beams without a range shifter, minimal differences were observed between the DCS and single aperture approximation. For range shifted beamlets, the single aperture approximation yielded wider penumbra widths (up to 18%) in the X-direction and sharper widths (up to 9.4%) in the Y-direction. For the example treatment plan, the root-mean-square errors (RMSEs) in an overall three-dimensional region of interest were 1.7%, 1.3%, and 1.7% for the single aperture, two aperture, and four aperture models, respectively. If the region of interest only encompasses the lateral edges outside of the target, the resulting RMSEs were 1.7%, 1.1%, and 0.5% single aperture, two aperture, and four aperture models, respectively.Conclusions. Monte Carlo simulations of the DCS demonstrated that a single aperture approximation is sufficient for modeling pristine fields at the Bragg depth while range shifted fields require a higher-order aperture approximation. For the treatment plan considered, the double aperture model performed the best overall, however, the four-aperture model most accurately modeled the lateral field edges at the expense of increased dose differences proximal to and within the target.
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Affiliation(s)
- Nicholas P. Nelson
- Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin—Madison, 1111 Highland Avenue, Madison, WI, 53705
| | - Wesley S. Culberson
- Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin—Madison, 1111 Highland Avenue, Madison, WI, 53705
| | - Daniel E. Hyer
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA, 52242
| | - Blake R. Smith
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA, 52242
| | - Ryan T. Flynn
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA, 52242
| | - Patrick M. Hill
- Department of Human Oncology, School of Medicine and Public Health, University of Wisconsin—Madison, 600 Highland Avenue, Madison, WI, 53792
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13
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Smith BR, M S NPN, M S TJG, M S KAP, Hill PM, Yu J, Gutiérrez AN, Md BGA, Hyer DE. The dosimetric enhancement of GRID profiles using an external collimator in pencil beam scanning proton therapy. Med Phys 2022; 49:2684-2698. [PMID: 35120278 PMCID: PMC9007854 DOI: 10.1002/mp.15523] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Revised: 11/22/2021] [Accepted: 01/23/2022] [Indexed: 11/09/2022] Open
Abstract
PURPOSE The radiobiological benefits afforded by spatially fractionated (GRID) radiation therapy pairs well with the dosimetric advantages of proton therapy. Inspired by the emergence of energy-layer specific collimators in pencil beam scanning (PBS), this work investigates how the spot spacing and collimation can be optimized to maximize the therapeutic gains of a GRID treatment while demonstrating the integration of a dynamic collimation system (DCS) within a commercial beam line to deliver GRID treatments and experimentally benchmark Monte Carlo calculation methods. METHODS GRID profiles were experimentally benchmarked using a clinical DCS prototype that was mounted to the nozzle of the IBA Dedicated Nozzle system. Integral depth dose (IDD) curves and lateral profiles were measured for uncollimated and GRID-collimated beamlets. A library of collimated GRID dose distributions were simulated by placing beamlets within a specified uniform grid and weighting the beamlets to achieve a volume-averaged tumor cell survival equivalent to an open field delivery. The healthy tissue sparing afforded by the GRID distribution was then estimated across a range of spot spacings and collimation widths, which were later optimized based on the radiosensitivity of the tumor cell line and the nominal spot size of the PBS system. This was accomplished by using validated models of the IBA Universal and Dedicated nozzles. RESULTS Excellent agreement was observed between the measured and simulated profiles. The IDDs matched above 98.7% when analyzed using a 1%/1 mm gamma criteria with some minor deviation observed near the Bragg peak for higher beamlet energies. Lateral profile distributions predicted using Monte Carlo methods agreed well with the measured profiles; a gamma passing rate of 95% or higher was observed for all in-depth profiles examined using a 3%/2 mm criteria. Additional collimation was shown to improve PBS GRID treatments by sharpening the lateral penumbra of the beamlets but creates a tradeoff between enhancing the valley-to-peak ratio of the GRID delivery and the dose-volume effect. The optimal collimation width and spot spacing changed as a function of the tumor cell radiosensitivity, dose, and spot size. In general, a spot spacing below 2.0 cm with a collimation less than 1.0 cm provided a superior dose distribution among the specific cases studied. CONCLUSIONS The ability to customize a GRID dose distribution using different collimation sizes and spot spacings is a useful advantage, especially to maximize the overall therapeutic benefit. In this regard, the capabilities of the DCS, and perhaps alternative dynamic collimators, can be used to enhance GRID treatments. Physical dose models calculated using Monte Carlo methods were experimentally benchmarked in water and were found to accurately predict the respective dose distributions of uncollimated and DCS-collimated GRID profiles. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Blake R Smith
- Department of Radiation Oncology, University of Iowa, 200 Hawkins Drive, Iowa City, 52242 Iowa
| | - Nicholas P Nelson M S
- Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin-Madison, 1111 Highland Avenue, Madison, WI, 53705
| | | | | | - Patrick M Hill
- Department of Human Oncology, School of Medicine and Public Health, University of Wisconsin-Madison, 600 Highland Avenue, Madison, WI, 53792
| | - Jen Yu
- Department of Radiation Oncology, Miami Cancer Institute, Baptist Health South Florida, 8900 N. Kendall Drive, Miami, FL, 33176
| | - Alonso N Gutiérrez
- Department of Radiation Oncology, Miami Cancer Institute, Baptist Health South Florida, 8900 N. Kendall Drive, Miami, FL, 33176
| | - Bryan G Allen Md
- Department of Radiation Oncology, University of Iowa, 200 Hawkins Drive, Iowa City, 52242 Iowa
| | - Daniel E Hyer
- Department of Radiation Oncology, University of Iowa, 200 Hawkins Drive, Iowa City, 52242 Iowa
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14
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ur Rehman M, Zeidan OA, Willoughby T, Meeks SL, Kelly P, Erhart K. Dosimetric Comparison of Various Spot Placement Techniques in Proton Pencil Beam Scanning. Int J Part Ther 2022; 9:54-63. [PMID: 35774494 PMCID: PMC9238129 DOI: 10.14338/ijpt-21-00022.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Accepted: 11/30/2021] [Indexed: 11/30/2022] Open
Abstract
Purpose To present quantitative dosimetric evaluations of five proton pencil beam spot placement techniques. Materials and Methods The spot placement techniques that were investigated include two grid-based (rectilinear grid and hexagonal grid, both commonly available in commercial planning systems) and three boundary-contoured (concentric contours, hybrid, and optimized) techniques. Treatment plans were created for two different target volumes, one spherical and one conical. An optimal set of planning parameters was defined for all treatment plans and the impact of spot placement techniques on the plan quality was evaluated in terms of lateral/distal dose falloff, normal tissue sparing, conformity and homogeneity of dose distributions, as well as total number of spots used. Results The results of this work highlight that for grid-based spot placement techniques, the dose conformity is dependent on target cross-sectional shape perpendicular to beam direction, which changes for each energy layer. This variable conformity problem is mitigated by using boundary contoured spot placement techniques. However, in the case of concentric contours, the conformity is improved but at the cost of decreased homogeneity inside the target. Hybrid and optimized spot placement techniques, which use contoured spots at the boundary and gridlike interior spot patterns, provide more uniform dose distributions inside the target volume while maintaining the improved dose conformity. The optimized spot placement technique improved target coverage, homogeneity of dose, and minimal number of spots. The dependence of these results on spot size is also presented for both target shapes. Conclusion This work illustrates that boundary-contoured spot placement techniques offer marked improvement in dosimetry metrics when compared to commercially available grid-based techniques for a range of proton scanned beam spot sizes.
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Normal Tissue Complication Probability Modelling for Toxicity Prediction and Patient Selection in Proton Beam Therapy to the Central Nervous System: A Literature Review. Clin Oncol (R Coll Radiol) 2022; 34:e225-e237. [DOI: 10.1016/j.clon.2021.12.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Revised: 11/22/2021] [Accepted: 12/21/2021] [Indexed: 11/22/2022]
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Hyer DE, Ding X, Rong Y. Proton therapy needs further technological development to fulfill the promise of becoming a superior treatment modality (compared to photon therapy). J Appl Clin Med Phys 2021; 22:4-11. [PMID: 34730268 PMCID: PMC8598137 DOI: 10.1002/acm2.13450] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2021] [Accepted: 01/10/2021] [Indexed: 12/25/2022] Open
Affiliation(s)
- Daniel E. Hyer
- Department of Radiation OncologyUniversity of IowaIowa CityIowaUSA
| | - Xuanfeng Ding
- Department of Radiation OncologyWilliam Beaumont HospitalRoyal ParkMichiganUSA
| | - Yi Rong
- Department of Radiation OncologyMayo Clinic ArizonaPhoenixArizonaUSA
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17
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Lin H, Shi C, Huang S, Shen J, Kang M, Chen Q, Zhai H, McDonough J, Tochner Z, Deville C, Simone CB, Both S. Applications of various range shifters for proton pencil beam scanning radiotherapy. Radiat Oncol 2021; 16:146. [PMID: 34362396 PMCID: PMC8344212 DOI: 10.1186/s13014-021-01873-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Accepted: 07/29/2021] [Indexed: 11/24/2022] Open
Abstract
Background A range pull-back device, such as a machine-related range shifter (MRS) or a universal patient-related range shifter (UPRS), is needed in pencil beam scanning technique to treat shallow tumors. Methods Three UPRS made by QFix (Avondale, PA, USA) allow treating targets across the body: U-shaped bolus (UB), anterior lateral bolus (ALB), and couch top bolus. Head-and-neck (HN) patients who used the UPRS were tested. The in-air spot sizes were measured and compared in this study at air gaps: 6 cm, 16 cm, and 26 cm. Measurements were performed in a solid water phantom using a single-field optimization pencil beam scanning field with the ALB placed at 0, 10, and 20 cm air gaps. The two-dimensional dose maps at the middle of the spread-out Bragg peak were measured using ion chamber array MatriXX PT (IBA-Dosimetry, Schwarzenbruck, Germany) located at isocenter and compared with the treatment planning system. Results A UPRS can be consistently placed close to the patient and maintains a relatively small spot size resulting in improved dose distributions. However, when a UPRS is non-removable (e.g. thick couch top), the quality of volumetric imaging is degraded due to their high Z material construction, hindering the value of Image-Guided Radiation Therapy (IGRT). Limitations of using UPRS with small air gaps include reduced couch weight limit, potential collision with patient or immobilization devices, and challenges using non-coplanar fields with certain UPRS. Our experience showed the combination of a U-shaped bolus exclusively for an HN target and an MRS as the complimentary device for head-and-neck targets as well as for all other treatment sites may be ideal to preserve the dosimetric advantages of pencil beam scanning proton treatments across the body. Conclusion We have described how to implement UPRS and MRS for various clinical indications using the PBS technique, and comprehensively reviewed the advantage and disadvantages of UPRS and MRS. We recommend the removable UB only to be employed for the brain and HN treatments while an automated MRS is used for all proton beams that require RS but not convenient or feasible to use UB.
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Affiliation(s)
- Haibo Lin
- New York Proton Center, New York, 10035, USA.
| | - Chengyu Shi
- New York Proton Center, New York, 10035, USA
| | - Sheng Huang
- New York Proton Center, New York, 10035, USA
| | | | | | - Qing Chen
- New York Proton Center, New York, 10035, USA
| | | | - James McDonough
- Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Zelig Tochner
- Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Curtiland Deville
- Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University, Baltimore, MD, 21231, USA
| | | | - Stefan Both
- Department of Radiation Oncology, University Medical Center Groningen, Groningen, 9713 GZ, Netherlands
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18
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Hyer DE, Bennett LC, Geoghegan TJ, Bues M, Smith BR. Innovations and the Use of Collimators in the Delivery of Pencil Beam Scanning Proton Therapy. Int J Part Ther 2021; 8:73-83. [PMID: 34285937 PMCID: PMC8270095 DOI: 10.14338/ijpt-20-00039.1] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Accepted: 10/19/2020] [Indexed: 12/29/2022] Open
Abstract
Purpose The development of collimating technologies has become a recent focus in pencil beam scanning (PBS) proton therapy to improve the target conformity and healthy tissue sparing through field-specific or energy-layer–specific collimation. Given the growing popularity of collimators for low-energy treatments, the purpose of this work was to summarize the recent literature that has focused on the efficacy of collimators for PBS and highlight the development of clinical and preclinical collimators. Materials and Methods The collimators presented in this work were organized into 3 categories: per-field apertures, multileaf collimators (MLCs), and sliding-bar collimators. For each case, the system design and planning methodologies are summarized and intercompared from their existing literature. Energy-specific collimation is still a new paradigm in PBS and the 2 specific collimators tailored toward PBS are presented including the dynamic collimation system (DCS) and the Mevion Adaptive Aperture. Results Collimation during PBS can improve the target conformity and associated healthy tissue and critical structure avoidance. Between energy-specific collimators and static apertures, static apertures have the poorest dose conformity owing to collimating only the largest projection of a target in the beam's eye view but still provide an improvement over uncollimated treatments. While an external collimator increases secondary neutron production, the benefit of collimating the primary beam appears to outweigh the risk. The greatest benefit has been observed for low- energy treatment sites. Conclusion The consensus from current literature supports the use of external collimators in PBS under certain conditions, namely low-energy treatments or where the nominal spot size is large. While many recent studies paint a supportive picture, it is also important to understand the limitations of collimation in PBS that are specific to each collimator type. The emergence and paradigm of energy-specific collimation holds many promises for PBS proton therapy.
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Affiliation(s)
- Daniel E Hyer
- Department of Radiation Oncology, University of Iowa, Iowa City, IA, USA
| | - Laura C Bennett
- Department of Radiation Oncology, University of Iowa, Iowa City, IA, USA
| | | | - Martin Bues
- Department of Radiation Oncology, Mayo Clinic Arizona, Phoenix, AZ, USA
| | - Blake R Smith
- Department of Radiation Oncology, University of Iowa, Iowa City, IA, USA
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Willoughby TR, Boczkowski A, Meeks SL, Bova FJ, Zeidan OA, Erhart K, Kelly P. Design and characterization of a prototype tertiary device for proton beam stereotactic radiosurgery. Biomed Phys Eng Express 2021; 7. [PMID: 34087816 DOI: 10.1088/2057-1976/ac086b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Accepted: 06/04/2021] [Indexed: 11/12/2022]
Abstract
Though potentially beneficial, proton beam stereotactic radiosurgery has not been adopted widely secondary to the technical challenge of safely delivering multiple focused beams of proton radiation. In this study, we describe the design and characterization of a proton beam stereotactic radiosurgery system that can be adopted by existing passive scattering systems. This system utilizes a helmet-like device in which patient-specific brass apertures required for final beam collimation are positioned on a scaffold that is separate from the treatment gantry. The proton snout is then fitted with a generic aperture to focus the primary proton beam onto the patient specific apertures that are in the helmet-like device. The patient-specific apertures can all be placed at the start of the treatment, thus treatment with multiple beams can be accomplished without the delay of switching the apertures. In this report we describe a prototype design of this collimation system and dosimetric testing to verify efficacy. Subsequently, we describe a custom 3D printing of a prototype device and report on overall localization accuracy using Winston-Lutz tests. Our results show that it is possible to develop an add-on device for proton beam radiosurgery that is safe and efficient and capable of wide adoption on existing proton delivery systems.
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Affiliation(s)
- T R Willoughby
- Department of Radiation Oncology, Orlando Health Cancer Institute, Orlando, FL, United States of America
| | - A Boczkowski
- Department of Neurosurgery, University of Florida, Gainesville, FL, United States of America
| | - S L Meeks
- Department of Radiation Oncology, Orlando Health Cancer Institute, Orlando, FL, United States of America
| | - F J Bova
- Department of Neurosurgery, University of Florida, Gainesville, FL, United States of America
| | - O A Zeidan
- Department of Radiation Oncology, Orlando Health Cancer Institute, Orlando, FL, United States of America
| | - K Erhart
- DotDecimal, Sanford, FL, United States of America
| | - P Kelly
- Department of Radiation Oncology, Orlando Health Cancer Institute, Orlando, FL, United States of America
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Nelson NP, Culberson WS, Hyer DE, Geoghegan TJ, Patwardhan KA, Smith BR, Flynn RT, Yu J, Rana S, Gutiérrez AN, Hill PM. Development and validation of the Dynamic Collimation Monte Carlo simulation package for pencil beam scanning proton therapy. Med Phys 2021; 48:3172-3185. [PMID: 33740253 DOI: 10.1002/mp.14846] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Revised: 03/11/2021] [Accepted: 03/11/2021] [Indexed: 11/10/2022] Open
Abstract
PURPOSE The aim of this work was to develop and experimentally validate a Dynamic Collimation Monte Carlo (DCMC) simulation package specifically designed for the simulation of collimators in pencil beam scanning proton therapy (PBS-PT). The DCMC package was developed using the TOPAS Monte Carlo platform and consists of a generalized PBS source model and collimator component extensions. METHODS A divergent point-source model of the IBA dedicated nozzle (DN) at the Miami Cancer Institute (MCI) was created and validated against on-axis commissioning measurements taken at MCI. The beamline optics were mathematically incorporated into the source to model beamlet deflections in the X and Y directions at the respective magnet planes. Off-axis measurements taken at multiple planes in air were used to validate both the off-axis spot size and divergence of the source model. The DCS trimmers were modeled and incorporated as TOPAS geometry extensions that linearly translate and rotate about the bending magnets. To validate the collimator model, a series of integral depth dose (IDD) and lateral profile measurements were acquired at MCI and used to benchmark the DCMC performance for modeling both pristine and range shifted beamlets. The water equivalent thickness (WET) of the range shifter was determined by quantifying the shift in the depth of the 80% dose point distal to the Bragg peak between the range shifted and pristine uncollimated beams. RESULTS A source model of the IBA DN system was successfully commissioned against on- and off-axis IDD and lateral profile measurements performed at MCI. The divergence of the source model was matched through an optimization of the source-to-axis distance and comparison against in-air spot profiles. The DCS model was then benchmarked against collimated IDD and in-air and in-phantom lateral profile measurements. Gamma analysis was used to evaluate the agreement between measured and simulated lateral profiles and IDDs with 1%/1 mm criteria and a 1% dose threshold. For the pristine collimated beams, the average 1%/1 mm gamma pass rates across all collimator configurations investigated were 99.8% for IDDs and 97.6% and 95.2% for in-air and in-phantom lateral profiles. All range shifted collimated IDDs passed at 100% while in-air and in-phantom lateral profiles had average pass rates of 99.1% and 99.8%, respectively. The measured and simulated WET of the polyethylene range shifter was determined to be 40.9 and 41.0 mm, respectively. CONCLUSIONS We have developed a TOPAS-based Monte Carlo package for modeling collimators in PBS-PT. This package was then commissioned to model the IBA DN system and DCS located at MCI using both uncollimated and collimated measurements. Validation results demonstrate that the DCMC package can be used to accurately model other aspects of a DCS implementation via simulation.
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Affiliation(s)
- Nicholas P Nelson
- Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin-Madison, 1111 Highland Avenue, Madison, WI, 53705, USA
| | - Wesley S Culberson
- Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin-Madison, 1111 Highland Avenue, Madison, WI, 53705, USA
| | - Daniel E Hyer
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA, 52242, USA
| | - Theodore J Geoghegan
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA, 52242, USA
| | - Kaustubh A Patwardhan
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA, 52242, USA
| | - Blake R Smith
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA, 52242, USA
| | - Ryan T Flynn
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA, 52242, USA
| | - Jen Yu
- Department of Radiation Oncology, Miami Cancer Institute, Baptist Health South Florida, 8900 N. Kendall Drive, Miami, FL, 33176, USA
| | - Suresh Rana
- Department of Radiation Oncology, Miami Cancer Institute, Baptist Health South Florida, 8900 N. Kendall Drive, Miami, FL, 33176, USA
| | - Alonso N Gutiérrez
- Department of Radiation Oncology, Miami Cancer Institute, Baptist Health South Florida, 8900 N. Kendall Drive, Miami, FL, 33176, USA
| | - Patrick M Hill
- Department of Human Oncology, School of Medicine and Public Health, University of Wisconsin-Madison, 600 Highland Avenue, Madison, WI, 53792, USA
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Boczkowski A, Kelly P, Meeks SL, Erhart K, Bova FJ, Willoughby TR. Proton vs Hyperarc™ radiosurgery: A planning comparison. J Appl Clin Med Phys 2020; 21:96-108. [PMID: 33151014 PMCID: PMC7769415 DOI: 10.1002/acm2.13075] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 09/24/2020] [Accepted: 09/29/2020] [Indexed: 11/29/2022] Open
Abstract
For many patients, stereotactic radiosurgery (SRS) offers a minimally invasive, curative option when surgical techniques are not possible. To date, the literature supporting the efficacy and safety of SRS treatment techniques uses photon beams. However, with the number of proton therapy facilities exponentially growing and the favorable physical properties of proton beam radiation therapy, there is an opportunity to develop proton therapy techniques for SRS. The goal of this paper is to determine the ability of clinical proton treatment planning systems to model small field dosimetry accurately and to compare various planning metrics used to evaluate photon SRS to determine the optimum beam configurations and settings for proton SRS (PSRS) treatment plans. Once established, these plan settings were used to perform a planning comparison on a variety of different SRS cases and compare SRS metrics between the PSRS plans and HyperArc™ (VMAT) SRS plans.
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Affiliation(s)
- A. Boczkowski
- Department of NeurosurgeryUniversity of FloridaGainesvilleFLUSA
| | - P. Kelly
- UF Health Cancer Center–Orlando HealthOrlandoFLUSA
| | - S. L. Meeks
- UF Health Cancer Center–Orlando HealthOrlandoFLUSA
| | | | - F. J. Bova
- Department of NeurosurgeryUniversity of FloridaGainesvilleFLUSA
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Geoghegan TJ, Nelson NP, Flynn RT, Hill PM, Rana S, Hyer DE. Design of a focused collimator for proton therapy spot scanning using Monte Carlo methods. Med Phys 2020; 47:2725-2734. [PMID: 32170750 DOI: 10.1002/mp.14139] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Revised: 02/20/2020] [Accepted: 03/03/2020] [Indexed: 11/09/2022] Open
Abstract
PURPOSE When designing a collimation system for pencil beam spot scanning proton therapy, a decision must be made whether or not to rotate, or focus, the collimator to match beamlet deflection as a function of off-axis distance. If the collimator is not focused, the beamlet shape and fluence will vary as a function of off-axis distance due to partial transmission through the collimator. In this work, we quantify the magnitude of these effects and propose a focused dynamic collimation system (DCS) for use in proton therapy spot scanning. METHODS This study was done in silico using a model of the Miami Cancer Institute's (MCI) IBA Proteus Plus system created in Geant4-based TOPAS. The DCS utilizes rectangular nickel trimmers mounted on rotating sliders that move in synchrony with the pencil beam to provide focused collimation at the edge of the target. Using a simplified setup of the DCS, simulations were performed at various off-axis locations corresponding to beam deflection angles ranging from 0° to 2.5°. At each off-axis location, focused (trimmer rotated) and unfocused (trimmer not rotated) simulations were performed. In all simulations, a 4 cm water equivalent thickness range shifter was placed upstream of the collimator, and a voxelized water phantom that scored dose was placed downstream, each with 4 cm airgaps. RESULTS Increasing the beam deflection angle for an unfocused trimmer caused the collimated edge of the beamlet profile to shift 0.08-0.61 mm from the baseline 0° simulation. There was also an increase in low-dose regions on the collimated edge ranging from 14.6% to 192.4%. Lastly, the maximum dose, D max , was 0-5% higher for the unfocused simulations. With a focused trimmer design, the profile shift and dose increases were all eliminated. CONCLUSIONS We have shown that focusing a collimator in spot scanning proton therapy reduces dose at the collimated edge compared to conventional, unfocused collimation devices and presented a simple, mechanical design for achieving focusing for a range of source-to-collimator distances.
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Affiliation(s)
- Theodore J Geoghegan
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA, 52242, USA
| | - Nicholas P Nelson
- Department of Medical Physics, University of Wisconsin, 1111 Highland Avenue, Madison, WI, 53705, USA
| | - Ryan T Flynn
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA, 52242, USA
| | - Patrick M Hill
- Department of Human Oncology, University of Wisconsin, 600 Highland Avenue, Madison, WI, 53792, USA
| | - Suresh Rana
- Department of Radiation Oncology, Miami Cancer Institute, Baptist Health South Florida, 8900 N. Kendall Drive, Miami, FL, 33176, USA
| | - Daniel E Hyer
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA, 52242, USA
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Liu G, Li X, Qin A, Zheng W, Yan D, Zhang S, Stevens C, Kabolizadeh P, Ding X. Improve the dosimetric outcome in bilateral head and neck cancer (HNC) treatment using spot-scanning proton arc (SPArc) therapy: a feasibility study. Radiat Oncol 2020; 15:21. [PMID: 32000817 PMCID: PMC6990547 DOI: 10.1186/s13014-020-1476-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Accepted: 01/20/2020] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND To explore the dosimetric improvement, delivery efficiency, and plan robustness for bilateral head and neck cancer (HNC) treatment utilizing a novel proton therapy technique - the spot-scanning proton arc (SPArc) therapy. METHODS We evaluated fourteen bilateral HNC patients retrospectively. Both SPArc and 3-field Intensity Modulated Proton Therapy (IMPT) plans were generated for each patient using the same robust optimization parameters. The prescription doses were 70Gy (relative biological effectiveness (RBE) for CTV_high and 60Gy[RBE] for CTV_low. Clinically significant dosimetric parameters were extracted and compared. Root-mean-square deviation dose (RMSDs) Volume Histogram(RVH) was used to evaluate the plan robustness. Total treatment delivery time was estimated based on the machine parameters. RESULTS The SPArc plan was able to provide equivalent or better robust target coverage while showed significant dosimetric improvements over IMPT in most of the organs at risk (OARs). More specifically, it reduced the mean dose of the ipsilateral parotid, contralateral parotid, and oral cavity by 25.8%(p = 0.001), 20.8%(p = 0.001) and 20.3%(p = 0.001) respectively compared to IMPT. This technique reduced D1 (the maximum dose covering 1% volume of a structure) of cord and brain stem by 20.8% (p = 0.009) and 10.7% (p = 0.048), respectively. SPArc also reduced the average integral dose by 17.2%(p = 0.001) and external V3Gy (the volume received 3Gy[RBE]) by 8.3%(p = 0.008) as well. RVH analysis showed that the SPArc plans reduced the dose uncertainties in most OARs compared to IMPT, such as cord: 1.1 ± 0.4Gy[RBE] vs 0.7 ± 0.3Gy[RBE](p = 0.001), brain stem: 0.9 ± 0.7Gy[RBE] vs 0.7 ± 0.7Gy[RBE](p = 0.019), contralateral parotid: 2.5 ± 0.5Gy[RBE] vs 2.2 ± 0.6Gy[RBE](p = 0.022) and ipsilateral parotid: 3.1 ± 0.7Gy[RBE] vs 2.8 ± 0.6Gy[RBE](p = 0.004) respectively. The average total estimated treatment delivery time were 283.4 ± 56.2 s, 469.2 ± 62.0 s and 1294.9 ± 106.7 s based on energy-layer-switching-time (ELST) of 0.1 s, 1 s, and 5 s respectively for SPArc plans, compared to the respective values of 328.0 ± 47.6 s(p = 0.002), 434.1 ± 52.0 s(p = 0.002), and 901.7 ± 74.8 s(p = 0.001) for 3-field IMPT plans. The potential clinical benefit of utilizing SPArc will lead to a decrease in the mean probability of salivary flow dysfunction by 31.3%(p = 0.001) compared with IMPT. CONCLUSIONS SPArc could significantly spare OARs while providing a similar or better robust target coverage compared with IMPT in the treatment of bilateral HNC. In the modern proton system with ELST less than 0.5 s, SPArc could potentially be implemented in the routine clinic with a practical, achievable treatment delivery efficiency.
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Affiliation(s)
- Gang Liu
- Cancer Center, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430023 China
- Department of Radiation Oncology, Beaumont Health System, Royal Oak, MI 48074 USA
- School of Physics and Technology, Wuhan University, Hubei, Wuhan, 430072 China
| | - Xiaoqiang Li
- Department of Radiation Oncology, Beaumont Health System, Royal Oak, MI 48074 USA
| | - An Qin
- Department of Radiation Oncology, Beaumont Health System, Royal Oak, MI 48074 USA
| | - Weili Zheng
- Department of Radiation Oncology, Beaumont Health System, Royal Oak, MI 48074 USA
| | - Di Yan
- Department of Radiation Oncology, Beaumont Health System, Royal Oak, MI 48074 USA
| | - Sheng Zhang
- Cancer Center, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430023 China
| | - Craig Stevens
- Department of Radiation Oncology, Beaumont Health System, Royal Oak, MI 48074 USA
| | - Peyman Kabolizadeh
- Department of Radiation Oncology, Beaumont Health System, Royal Oak, MI 48074 USA
| | - Xuanfeng Ding
- Department of Radiation Oncology, Beaumont Health System, Royal Oak, MI 48074 USA
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Ur Rehman M, Erhart K, Kielbasa J, Meeks SL, Li Z, Willoughby T, Ramakrishna N, Stephenson K, Rahman TS, Kelly P, Zeidan O. An optimized approach for robust spot placement in proton pencil beam scanning. Phys Med Biol 2019; 64:235016. [PMID: 31618722 DOI: 10.1088/1361-6560/ab4e78] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Maintaining a sharp lateral dose falloff in pencil beam scanning (PBS) proton therapy is crucial for sparing organs at risk (OARs), especially when they are in close proximity to the target volume. The most common approach to improve lateral dose falloff is through the use of physical beam shaping devices, such as brass apertures or collimator based systems. A recently proposed approach focuses on proton beam spot placements, moving away from traditional grid-based placements to concentric-contours based schemes. This improves lateral dose falloff in two ways: (1) by better conforming all spots to the tumor boundary and (2) allowing for 'edge enhancement', where boundary spots deliver higher fluence than more central spots, thereby creating a steeper lateral dose falloff. However, these benefits come at the expense of maintaining uniformity of spot distribution inside the target volume. In this work we have developed a new optimized spot placement scheme that provides robust spot distributions inside the target. This approach achieves the boundary conformity of a concentric-contours based approach and uses a fast-iterative method to distribute the interior spots in a highly uniform fashion in an attempt to improve both the lateral dose falloff and uniformity. Furthermore, we quantified the impact of this new approach through direct comparison with grid, contour, and hybrid spot placements schemes, showing improvements for this new approach. The results were validated in homogeneous medium for two different target shapes having concave and convex geometry.
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Affiliation(s)
- Mahboob Ur Rehman
- University of Central Florida, Orlando, FL, United States of America
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25
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Smith BR, Hyer DE, Flynn RT, Hill PM, Culberson WS. Trimmer sequencing time minimization during dynamically collimated proton therapy using a colony of cooperating agents. Phys Med Biol 2019; 64:205025. [PMID: 31484170 DOI: 10.1088/1361-6560/ab416d] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The dynamic collimation system (DCS) can be combined with pencil beam scanning proton therapy to deliver highly conformal treatment plans with unique collimation at each energy layer. This energy layer-specific collimation is accomplished through the synchronized motion of four trimmer blades that intercept the proton beam near the target boundary in the beam's eye view. However, the corresponding treatment deliveries come at the cost of additional treatment time since the translational speed of the trimmer is slower than the scanning speed of the proton pencil beam. In an attempt to minimize the additional trimmer sequencing time of each field while still maintaining a high degree of conformity, a novel process utilizing ant colony optimization (ACO) methods was created to determine the most efficient route of trimmer sequencing and beamlet scanning patterns for a collective set of collimated proton beamlets. The ACO process was integrated within an in-house treatment planning system optimizer to determine the beam scanning and DCS trimmer sequencing patterns and compared against an analytical approximation of the trimmer sequencing time should a contour-like scanning approach be assumed instead. Due to the stochastic nature of ACO, parameters where determined so that they could ensure good convergence and an efficient optimization of trimmer sequencing that was faster than an analytical contour-like trimmer sequencing. The optimization process was tested using a set of three intracranial treatment plans which were planned using a custom research treatment planning system and were successfully optimized to reduce the additional trimmer sequencing time to approximately 60 s per treatment field while maintaining a high degree of target conformity. Thus, the novel use of ACO techniques within a treatment planning algorithm has been demonstrated to effectively determine collimation sequencing patterns for a DCS in order to minimize the additional treatment time required for trimmer movement during treatment.
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Affiliation(s)
- Blake R Smith
- Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin 53705. Author to whom correspondence should be addressed
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26
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Bäumer C, Fuentes C, Janson M, Matic A, Timmermann B, Wulff J. Stereotactical fields applied in proton spot scanning mode with range shifter and collimating aperture. ACTA ACUST UNITED AC 2019; 64:155003. [DOI: 10.1088/1361-6560/ab2ae7] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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Smith BR, Hyer DE, Hill PM, Culberson WS. Secondary Neutron Dose From a Dynamic Collimation System During Intracranial Pencil Beam Scanning Proton Therapy: A Monte Carlo Investigation. Int J Radiat Oncol Biol Phys 2018; 103:241-250. [PMID: 30114462 DOI: 10.1016/j.ijrobp.2018.08.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Revised: 07/25/2018] [Accepted: 08/04/2018] [Indexed: 01/01/2023]
Abstract
PURPOSE Patients receiving pencil beam scanning (PBS) proton therapy with the addition of a dynamic collimation system (DCS) are potentially subject to an additional neutron dose from interactions between the incident proton beam and the trimmer blades. This study investigates the secondary neutron dose rates for both single-field uniform dose (SFUD) and intensity modulated proton therapy treatments. METHODS AND MATERIALS Secondary neutron dose distributions were calculated for both a dynamically collimated and an uncollimated, dual-field chordoma treatment plan and compared with previously published neutron dose rates from other contemporary scanning treatment modalities. Monte Carlo N-Particle transport code was used to track all primary and secondary particles generated from nuclear reactions within the DCS during treatment through a model of the patient geometry acquired from the computed tomography planning data set. Secondary neutron ambient dose equivalent distributions were calculated throughout the patient using a meshgrid with a tally resolution equivalent to that of the treatment planning computed tomography. RESULTS The median healthy-brain neutron ambient dose equivalent for a dynamically collimated intracranial chordoma treatment plan using a DCS was found to be 0.97 mSv/Gy for the right lateral SFUD field, 1.37 mSv/Gy for the apex SFUD field, and 1.24 mSv/Gy for the composite intensity modulated proton therapy distribution from 2 fields. CONCLUSIONS These results were at least 55% lower than what has been reported for uniform scanning modalities with brass apertures. However, they still reflect an increase in the excess relative risk of secondary cancer incidence compared with an uncollimated PBS treatment using only a graphite range shifter. Regardless, the secondary neutron dose expected from the DCS for these PBS proton therapy treatments appears to be on the order of, or below, what is expected for alternative collimated proton therapy techniques.
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Affiliation(s)
- Blake R Smith
- Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin.
| | - Daniel E Hyer
- Department of Radiation Oncology, University of Iowa, Iowa City, Iowa
| | - Patrick M Hill
- Department of Human Oncology, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin
| | - Wesley S Culberson
- Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin
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Farr JB, Moskvin V, Lukose RC, Tuomanen S, Tsiamas P, Yao W. Development, commissioning, and evaluation of a new intensity modulated minibeam proton therapy system. Med Phys 2018; 45:4227-4237. [PMID: 30009481 DOI: 10.1002/mp.13093] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Revised: 07/02/2018] [Accepted: 07/10/2018] [Indexed: 11/10/2022] Open
Abstract
PURPOSE To invent, design, construct, and commission an intensity modulated minibeam proton therapy system (IMMPT) without the need for physical collimation and to compare its resulting conformity to a conventional IMPT system. METHODS A proton therapy system (Hitachi, Ltd, Hitachi City, Japan; Model: Probeat-V) was specially modified to produce scanned minibeams without collimation. We performed integral depth dose acquisitions and calibrations using a large diameter parallel-plate ionization chamber in a scanning water phantom (PTW, Freiburg, Germany; Models: Bragg Peak ionization chamber, MP3-P). Spot size and shape was measured using radiochromic film (Ashland Advanced Materials, Bridgewater NJ; Type: EBT3), and a synthetic diamond diode type scanned point by point in air (PTW Models: MicroDiamond, MP3-P). The measured data were used as inputs to generate a Monte Carlo-based model for a commercial radiotherapy planning system (TPS) (Varian Medical Systems, Inc., Palo Alto, CA; Model: Eclipse v13.7.15). The regular ProBeat-V system (sigma ~2.5 mm) TPS model was available for comparison. A simulated base of skull case with small and medium targets proximal to brainstem was planned for both systems and compared. RESULTS The spot sigma is determined to be 1.4 mm at 221 MeV at the isocenter and below 1 mm at proximal distances. Integral depth doses were indistinguishable from the standard spot commissioning data. The TPS fit the spot profiles closely, giving a residual error maximum of 2.5% in the spot penumbra tails (below 5% of maximum) from the commissioned energies 69.4 to 221.3 MeV. The resulting IMMPT plans were more conformal than the IMPT plans due to a sharper dose gradient (90-10%) 1.5 mm smaller for the small target, and 1.3 mm for the large target, at a representative central axial water equivalent depth of 7 cm. CONCLUSIONS We developed, implemented, and tested a new IMMPT system. The initial results look promising in cases where treatments can benefit from additional dose sparing to neighboring sensitive structures.
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Affiliation(s)
- J B Farr
- Department of Radiation Oncology, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN, 38105-2794, USA
| | - V Moskvin
- Department of Radiation Oncology, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN, 38105-2794, USA
| | - R C Lukose
- Department of Radiation Oncology, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN, 38105-2794, USA
| | - S Tuomanen
- Department of Radiation Oncology, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN, 38105-2794, USA
| | - P Tsiamas
- Department of Radiation Oncology, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN, 38105-2794, USA
| | - W Yao
- Department of Radiation Oncology, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN, 38105-2794, USA
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Kraan AC, Depauw N, Clasie B, Giunta M, Madden T, Kooy HM. Effects of spot parameters in pencil beam scanning treatment planning. Med Phys 2017; 45:60-73. [DOI: 10.1002/mp.12675] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Revised: 11/07/2017] [Accepted: 11/07/2017] [Indexed: 11/10/2022] Open
Affiliation(s)
- Aafke Christine Kraan
- Applications of Detectors and Accelerators to Medicine (ADAM) SA; Geneva Switzerland
- Istituto Nazionale di Fisica Nucleare; Sezione di Pisa Italy
| | - Nicolas Depauw
- Department of Physics; Massachusetts General Hospital; Boston USA
| | - Ben Clasie
- Department of Physics; Massachusetts General Hospital; Boston USA
| | - Marina Giunta
- Applications of Detectors and Accelerators to Medicine (ADAM) SA; Geneva Switzerland
| | - Tom Madden
- Department of Physics; Massachusetts General Hospital; Boston USA
| | - Hanne M. Kooy
- Department of Physics; Massachusetts General Hospital; Boston USA
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Mohan R, Das IJ, Ling CC. Empowering Intensity Modulated Proton Therapy Through Physics and Technology: An Overview. Int J Radiat Oncol Biol Phys 2017; 99:304-316. [PMID: 28871980 PMCID: PMC5651132 DOI: 10.1016/j.ijrobp.2017.05.005] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Revised: 04/11/2017] [Accepted: 05/02/2017] [Indexed: 01/15/2023]
Abstract
Considering the clinical potential of protons attributable to their physical characteristics, interest in proton therapy has increased greatly in this century, as has the number of proton therapy installations. Until recently, passively scattered proton therapy was used almost entirely. Notably, the overall clinical results to date have not shown a convincing benefit of protons over photons. A rapid transition is now occurring with the implementation of the most advanced form of proton therapy, intensity modulated proton therapy (IMPT). IMPT is superior to passively scattered proton therapy and intensity modulated radiation therapy (IMRT) dosimetrically. However, numerous limitations exist in the present IMPT methods. In particular, compared with IMRT, IMPT is highly vulnerable to various uncertainties. In this overview we identify three major areas of current limitations of IMPT: treatment planning, treatment delivery, and motion management, and discuss current and future efforts for improvement. For treatment planning, we need to reduce uncertainties in proton range and in computed dose distributions, improve robust planning and optimization, enhance adaptive treatment planning and delivery, and consider how to exploit the variability in the relative biological effectiveness of protons for clinical benefit. The quality of proton therapy also depends on the characteristics of the IMPT delivery systems and image guidance. Efforts are needed to optimize the beamlet spot size for both improved dose conformality and faster delivery. For the latter, faster energy switching time and increased dose rate are also needed. Real-time in-room volumetric imaging for guiding IMPT is in its early stages with cone beam computed tomography (CT) and CT-on-rails, and continued improvements are anticipated. In addition, imaging of the proton beams themselves, using, for instance, prompt γ emissions, is being developed to determine the proton range and to reduce range uncertainty. With the realization of the advances described above, we posit that IMPT, thus empowered, will lead to substantially improved clinical results.
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Affiliation(s)
- Radhe Mohan
- Department of Radiation Physics, MD Anderson Cancer Center, Houston, Texas.
| | - Indra J Das
- Department of Radiation Oncology, New York University Langone Medical Center, New York, New York
| | - Clifton C Ling
- Varian Medical Systems and Department of Radiation Oncology, Stanford University, Stanford, California
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Smith B, Gelover E, Moignier A, Wang D, Flynn RT, Lin L, Kirk M, Solberg T, Hyer DE. Technical Note: A treatment plan comparison between dynamic collimation and a fixed aperture during spot scanning proton therapy for brain treatment. Med Phys 2017; 43:4693. [PMID: 27487886 DOI: 10.1118/1.4955117] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE To quantitatively assess the advantages of energy-layer specific dynamic collimation system (DCS) versus a per-field fixed aperture for spot scanning proton therapy (SSPT). METHODS Five brain cancer patients previously planned and treated with SSPT were replanned using an in-house treatment planning system capable of modeling collimated and uncollimated proton beamlets. The uncollimated plans, which served as a baseline for comparison, reproduced the target coverage and organ-at-risk sparing of the clinically delivered plans. The collimator opening for the fixed aperture-based plans was determined from the combined cross sections of the target in the beam's eye view over all energy layers which included an additional margin equivalent to the maximum beamlet displacement for the respective energy of that energy layer. The DCS-based plans were created by selecting appropriate collimator positions for each row of beam spots during a Raster-style scanning pattern which were optimized to maximize the dose contributions to the target and limited the dose delivered to adjacent normal tissue. RESULTS The reduction of mean dose to normal tissue adjacent to the target, as defined by a 10 mm ring surrounding the target, averaged 13.65% (range: 11.8%-16.9%) and 5.18% (2.9%-7.1%) for the DCS and fixed aperture plans, respectively. The conformity index, as defined by the ratio of the volume of the 50% isodose line to the target volume, yielded an average improvement of 21.35% (19.4%-22.6%) and 8.38% (4.7%-12.0%) for the DCS and fixed aperture plans, respectively. CONCLUSIONS The ability of the DCS to provide collimation to each energy layer yielded better conformity in comparison to fixed aperture plans.
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Affiliation(s)
- Blake Smith
- Department of Radiation Oncology, University of Iowa, 200 Hawkins Drive, Iowa City, Iowa 52242
| | - Edgar Gelover
- Department of Radiation Oncology, University of Iowa, 200 Hawkins Drive, Iowa City, Iowa 52242
| | - Alexandra Moignier
- Department of Radiation Oncology, University of Iowa, 200 Hawkins Drive, Iowa City, Iowa 52242
| | - Dongxu Wang
- Department of Radiation Oncology, University of Iowa, 200 Hawkins Drive, Iowa City, Iowa 52242
| | - Ryan T Flynn
- Department of Radiation Oncology, University of Iowa, 200 Hawkins Drive, Iowa City, Iowa 52242
| | - Liyong Lin
- Department of Radiation Oncology, University of Pennsylvania, TRC 2 West, 3400 Civic Center Boulevard, Philadelphia, Pennsylvania 19104
| | - Maura Kirk
- Department of Radiation Oncology, University of Pennsylvania, TRC 2 West, 3400 Civic Center Boulevard, Philadelphia, Pennsylvania 19104
| | - Tim Solberg
- Department of Radiation Oncology, University of Pennsylvania, TRC 2 West, 3400 Civic Center Boulevard, Philadelphia, Pennsylvania 19104
| | - Daniel E Hyer
- Department of Radiation Oncology, University of Iowa, 200 Hawkins Drive, Iowa City, Iowa 52242
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Moignier A, Gelover E, Smith BR, Wang D, Flynn RT, Kirk ML, Lin L, Solberg TD, Lin A, Hyer DE. Toward improved target conformity for two spot scanning proton therapy delivery systems using dynamic collimation. Med Phys 2016; 43:1421-7. [PMID: 26936726 DOI: 10.1118/1.4942375] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE To quantify improvement in target conformity in brain and head and neck tumor treatments resulting from the use of a dynamic collimation system (DCS) with two spot scanning proton therapy delivery systems (universal nozzle, UN, and dedicated nozzle, DN) with median spot sizes of 5.2 and 3.2 mm over a range of energies from 100 to 230 MeV. METHODS Uncollimated and collimated plans were calculated with both UN and DN beam models implemented within our in-house treatment planning system for five brain and ten head and neck datasets in patients previously treated with spot scanning proton therapy. The prescription dose and beam angles from the clinical plans were used for both the UN and DN plans. The average reduction of the mean dose to the 10-mm ring surrounding the target between the uncollimated and collimated plans was calculated for the UN and the DN. Target conformity was analyzed using the mean dose to 1-mm thickness rings surrounding the target at increasing distances ranging from 1 to 10 mm. RESULTS The average reductions of the 10-mm ring mean dose for the UN and DN plans were 13.7% (95% CI: 11.6%-15.7%; p < 0.0001) and 11.5% (95% CI: 9.5%-13.5%; p < 0.0001) across all brain cases and 7.1% (95% CI: 4.4%-9.8%; p < 0.001) and 6.3% (95% CI: 3.7%-9.0%; p < 0.001), respectively, across all head and neck cases. The collimated UN plans were either more conformal (all brain cases and 60% of the head and neck cases) than or equivalent (40% of the head and neck cases) to the uncollimated DN plans. The collimated DN plans offered the highest conformity. CONCLUSIONS The DCS added either to the UN or DN improved the target conformity. The DCS may be of particular interest for sites with UN systems looking for a more economical solution than upgrading the nozzle to improve the target conformity of their spot scanning proton therapy system.
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Affiliation(s)
- Alexandra Moignier
- Department of Radiation Oncology, University of Iowa, 200 Hawkins Drive, Iowa City, Iowa 52242
| | - Edgar Gelover
- Department of Radiation Oncology, University of Iowa, 200 Hawkins Drive, Iowa City, Iowa 52242
| | - Blake R Smith
- Department of Radiation Oncology, University of Iowa, 200 Hawkins Drive, Iowa City, Iowa 52242
| | - Dongxu Wang
- Department of Radiation Oncology, University of Iowa, 200 Hawkins Drive, Iowa City, Iowa 52242
| | - Ryan T Flynn
- Department of Radiation Oncology, University of Iowa, 200 Hawkins Drive, Iowa City, Iowa 52242
| | - Maura L Kirk
- Department of Radiation Oncology, University of Pennsylvania, TRC 2 West, 3400 Civic Center Boulevard, Philadelphia, Pennsylvania 19104
| | - Liyong Lin
- Department of Radiation Oncology, University of Pennsylvania, TRC 2 West, 3400 Civic Center Boulevard, Philadelphia, Pennsylvania 19104
| | - Timothy D Solberg
- Department of Radiation Oncology, University of Pennsylvania, TRC 2 West, 3400 Civic Center Boulevard, Philadelphia, Pennsylvania 19104
| | - Alexander Lin
- Department of Radiation Oncology, University of Pennsylvania, TRC 2 West, 3400 Civic Center Boulevard, Philadelphia, Pennsylvania 19104
| | - Daniel E Hyer
- Department of Radiation Oncology, University of Iowa, 200 Hawkins Drive, Iowa City, Iowa 52242
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Yao W, Merchant TE, Farr JB. A correction scheme for a simplified analytical random walk model algorithm of proton dose calculation in distal Bragg peak regions. Phys Med Biol 2016; 61:7397-7411. [PMID: 27694715 DOI: 10.1088/0031-9155/61/20/7397] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The lateral homogeneity assumption is used in most analytical algorithms for proton dose, such as the pencil-beam algorithms and our simplified analytical random walk model. To improve the dose calculation in the distal fall-off region in heterogeneous media, we analyzed primary proton fluence near heterogeneous media and propose to calculate the lateral fluence with voxel-specific Gaussian distributions. The lateral fluence from a beamlet is no longer expressed by a single Gaussian for all the lateral voxels, but by a specific Gaussian for each lateral voxel. The voxel-specific Gaussian for the beamlet of interest is calculated by re-initializing the fluence deviation on an effective surface where the proton energies of the beamlet of interest and the beamlet passing the voxel are the same. The dose improvement from the correction scheme was demonstrated by the dose distributions in two sets of heterogeneous phantoms consisting of cortical bone, lung, and water and by evaluating distributions in example patients with a head-and-neck tumor and metal spinal implants. The dose distributions from Monte Carlo simulations were used as the reference. The correction scheme effectively improved the dose calculation accuracy in the distal fall-off region and increased the gamma test pass rate. The extra computation for the correction was about 20% of that for the original algorithm but is dependent upon patient geometry.
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Affiliation(s)
- Weiguang Yao
- Department of Radiation Oncology, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA
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Moignier A, Gelover E, Wang D, Smith B, Flynn R, Kirk M, Lin L, Solberg T, Lin A, Hyer D. Theoretical Benefits of Dynamic Collimation in Pencil Beam Scanning Proton Therapy for Brain Tumors: Dosimetric and Radiobiological Metrics. Int J Radiat Oncol Biol Phys 2016; 95:171-180. [DOI: 10.1016/j.ijrobp.2015.08.030] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Revised: 07/01/2015] [Accepted: 08/17/2015] [Indexed: 10/22/2022]
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Moignier A, Gelover E, Wang D, Smith B, Flynn R, Kirk M, Lin L, Solberg T, Lin A, Hyer D. Improving Head and Neck Cancer Treatments Using Dynamic Collimation in Spot Scanning Proton Therapy. Int J Part Ther 2016; 2:544-554. [PMID: 31772966 DOI: 10.14338/ijpt-15-00026.1] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Accepted: 01/11/2016] [Indexed: 12/12/2022] Open
Abstract
Purpose Interest in using collimation for spot scanning proton therapy has recently increased in an attempt to improve the lateral penumbra. To investigate the advantages of such an approach for complex targets, a plan comparison between uncollimated and collimated beam spots was performed for patients with head and neck cancer. Patients and Methods For 10 patients with head and neck cancer, previously treated with spot scanning proton therapy, uncollimated and collimated treatment plans were created using an in-house treatment-planning system capable of modeling asymmetric-beamlet dose distributions resulting from the use of a dynamic collimation system. Both uncollimated and collimated plans reproduced clinically delivered plans in terms of target coverage. A relative plan comparison was performed using both physical and radiobiological metrics on the organs at risk. Results The dynamic collimation system improved dose-distribution conformity while preserving target coverage. The median reduction of the mean dose to the esophagus, uninvolved larynx, and uninvolved parotids were -11.9% (minimum to maximum, -6.4% to -24.1%), -7.2% (-0.8% to -60.1%), and -5.2% (-0.2% to -21.5%), respectively, and depended on the organ location relative to the target and radiation beam angle. The collimation did not improve dose to some organs at risk surrounded by the target or located upstream of Bragg peaks because of the priority on the target coverage. Conclusion In spot scanning proton therapy, the dynamic collimation system generally affords better target conformity, which results in improvement in organ-at-risk sparing in the head and neck region while preserving target coverage. However, the benefits of collimation and the increased complexity should be considered for each patient. Patients with large bilateral targets or organs at risk surrounded by the target showed the least benefit.
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Affiliation(s)
- Alexandra Moignier
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, Iowa City, IA, USA
| | - Edgar Gelover
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, Iowa City, IA, USA
| | - Dongxu Wang
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, Iowa City, IA, USA
| | - Blake Smith
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, Iowa City, IA, USA
| | - Ryan Flynn
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, Iowa City, IA, USA
| | - Maura Kirk
- Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA, USA
| | - Liyong Lin
- Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA, USA
| | - Timothy Solberg
- Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA, USA
| | - Alexander Lin
- Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA, USA
| | - Daniel Hyer
- Department of Radiation Oncology, University of Iowa Hospitals and Clinics, Iowa City, IA, USA
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Moteabbed M, Yock TI, Depauw N, Madden TM, Kooy HM, Paganetti H. Impact of Spot Size and Beam-Shaping Devices on the Treatment Plan Quality for Pencil Beam Scanning Proton Therapy. Int J Radiat Oncol Biol Phys 2015; 95:190-198. [PMID: 27084640 DOI: 10.1016/j.ijrobp.2015.12.368] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Revised: 12/17/2015] [Accepted: 12/21/2015] [Indexed: 01/13/2023]
Abstract
PURPOSE This study aimed to assess the clinical impact of spot size and the addition of apertures and range compensators on the treatment quality of pencil beam scanning (PBS) proton therapy and to define when PBS could improve on passive scattering proton therapy (PSPT). METHODS AND MATERIALS The patient cohort included 14 pediatric patients treated with PSPT. Six PBS plans were created and optimized for each patient using 3 spot sizes (∼12-, 5.4-, and 2.5-mm median sigma at isocenter for 90- to 230-MeV range) and adding apertures and compensators to plans with the 2 larger spots. Conformity and homogeneity indices, dose-volume histogram parameters, equivalent uniform dose (EUD), normal tissue complication probability (NTCP), and integral dose were quantified and compared with the respective PSPT plans. RESULTS The results clearly indicated that PBS with the largest spots does not necessarily offer a dosimetric or clinical advantage over PSPT. With comparable target coverage, the mean dose (Dmean) to healthy organs was on average 6.3% larger than PSPT when using this spot size. However, adding apertures to plans with large spots improved the treatment quality by decreasing the average Dmean and EUD by up to 8.6% and 3.2% of the prescribed dose, respectively. Decreasing the spot size further improved all plans, lowering the average Dmean and EUD by up to 11.6% and 10.9% compared with PSPT, respectively, and eliminated the need for beam-shaping devices. The NTCP decreased with spot size and addition of apertures, with maximum reduction of 5.4% relative to PSPT. CONCLUSIONS The added benefit of using PBS strongly depends on the delivery configurations. Facilities limited to large spot sizes (>∼8 mm median sigma at isocenter) are recommended to use apertures to reduce treatment-related toxicities, at least for complex and/or small tumors.
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Affiliation(s)
- Maryam Moteabbed
- Radiation Oncology Department, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts.
| | - Torunn I Yock
- Radiation Oncology Department, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Nicolas Depauw
- Radiation Oncology Department, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Thomas M Madden
- Radiation Oncology Department, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Hanne M Kooy
- Radiation Oncology Department, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Harald Paganetti
- Radiation Oncology Department, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
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Wang D, Smith BR, Gelover E, Flynn RT, Hyer DE. A method to select aperture margin in collimated spot scanning proton therapy. Phys Med Biol 2015; 60:N109-19. [PMID: 25776926 DOI: 10.1088/0031-9155/60/7/n109] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The use of collimator or aperture may sharpen the lateral dose gradient for spot scanning proton therapy. However, to date, there has not been a standard method to determine the aperture margin for a single field in collimated spot scanning proton therapy. This study describes a theoretical framework to select the optimal aperture margin for a single field, and also presents the spot spacing limit required such that the optimal aperture margin exists. Since, for a proton pencil beam partially intercepted by collimator, the maximum point dose (spot center) shifts away from the original pencil beam central axis, we propose that the optimal margin should be equal to the maximum pencil beam center shift under the condition that spot spacing is small with respect to the maximum pencil beam center shift, which can be numerically determined based on beam modeling data. A test case is presented which demonstrates agreement with the prediction made based on the proposed methods. When apertures are applied in a commercial treatment planning system this method may be implemented.
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Affiliation(s)
- Dongxu Wang
- Department of Radiation Oncology, University of Iowa, 200 Hawkins Drive, Iowa City, IA 52242, USA
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