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Simard M, Robertson DG, Fullarton R, Royle G, Beddar S, Collins-Fekete CA. Integrated-mode proton radiography with 2D lateral projections. Phys Med Biol 2024; 69:054001. [PMID: 38241716 DOI: 10.1088/1361-6560/ad209d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Accepted: 01/19/2024] [Indexed: 01/21/2024]
Abstract
Integrated-mode proton radiography leading to water equivalent thickness (WET) maps is an avenue of interest for motion management, patient positioning, andin vivorange verification. Radiographs can be obtained using a pencil beam scanning setup with a large 3D monolithic scintillator coupled with optical cameras. Established reconstruction methods either (1) involve a camera at the distal end of the scintillator, or (2) use a lateral view camera as a range telescope. Both approaches lead to limited image quality. The purpose of this work is to propose a third, novel reconstruction framework that exploits the 2D information provided by two lateral view cameras, to improve image quality achievable using lateral views. The three methods are first compared in a simulated Geant4 Monte Carlo framework using an extended cardiac torso (XCAT) phantom and a slanted edge. The proposed method with 2D lateral views is also compared with the range telescope approach using experimental data acquired with a plastic volumetric scintillator. Scanned phantoms include a Las Vegas (contrast), 9 tissue-substitute inserts (WET accuracy), and a paediatric head phantom. Resolution increases from 0.24 (distal) to 0.33 lp mm-1(proposed method) on the simulated slanted edge phantom, and the mean absolute error on WET maps of the XCAT phantom is reduced from 3.4 to 2.7 mm with the same methods. Experimental data from the proposed 2D lateral views indicate a 36% increase in contrast relative to the range telescope method. High WET accuracy is obtained, with a mean absolute error of 0.4 mm over 9 inserts. Results are presented for various pencil beam spacing ranging from 2 to 6 mm. This work illustrates that high quality proton radiographs can be obtained with clinical beam settings and the proposed reconstruction framework with 2D lateral views, with potential applications in adaptive proton therapy.
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Affiliation(s)
- Mikaël Simard
- Department of Medical Physics and Biomedical Engineering, University College London, London, United Kingdom
| | - Daniel G Robertson
- Division of Medical Physics, Department of Radiation Oncology, Mayo Clinic Arizona, 5881 E Mayo Blvd, Phoenix, AZ, United States of America
| | - Ryan Fullarton
- Department of Medical Physics and Biomedical Engineering, University College London, London, United Kingdom
| | - Gary Royle
- Department of Medical Physics and Biomedical Engineering, University College London, London, United Kingdom
| | - Sam Beddar
- The University of Texas MD Anderson UTHealth Graduate School of Biomedical Sciences, Houston, TX, 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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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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Bäumer C, Janson M, Timmermann B, Wulff J. Collimated proton pencil-beam scanning for superficial targets: impact of the order of range shifter and aperture. ACTA ACUST UNITED AC 2018; 63:085020. [DOI: 10.1088/1361-6560/aab79c] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Affiliation(s)
- Christoph Börgers
- Tufts University, Department of Mathematics, Medford, Massachusetts 02155
| | - Edward W. Larsen
- University of Michigan, Department of Nuclear Engineering, Ann Arbor, Michigan 48109
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Schippers JM. Beam Delivery Systems for Particle Radiation Therapy: Current Status and Recent Developments. ACTA ACUST UNITED AC 2012. [DOI: 10.1142/s1793626809000211] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
An overview is given of different techniques of dose delivery applied in currently operating and planned particle therapy systems. Their advantages and disadvantages will be compared and consequences of the methods for the rest of the instrumentation will be discussed. The interrelationship between beam delivery at the patient and the accelerator system is shown by means of several concrete examples. Apart from a description of several subsystems in a particle therapy facility, design rules for optimizing the reliability of an accelerator and beam delivery system will be discussed, as well as some remarks concerning how to deal with future developments.
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Safai S, Bortfeld T, Engelsman M. Comparison between the lateral penumbra of a collimated double-scattered beam and uncollimated scanning beam in proton radiotherapy. Phys Med Biol 2008; 53:1729-50. [DOI: 10.1088/0031-9155/53/6/016] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Sjögren R, Karlsson MG, Karlsson M. Methods for the determination of effective monitor chamber thickness. Med Phys 1999; 26:1871-3. [PMID: 10505875 DOI: 10.1118/1.598692] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
There are a number of models, both analytical and Monte Carlo, which are used to describe the fluence from the treatment head of accelerators. One common problem in these simulations is to find relevant information about details in the treatment head. A complex unit in the treatment head for which reliable data is seldom given is the monitor chamber. In this work two methods are described for obtaining this information by analyzing the increased scattering of an electron beam when the monitor chamber is introduced in the beam. It was found that the effective thickness of the electrodes in a monitor chamber can be determined with sufficient accuracy by using experimental results combined with Fermi-Eyges theory or Monte Carlo simulations.
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Affiliation(s)
- R Sjögren
- Department of Radiation Physics, Umeå University, Sweden
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