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Oborn BM, Semioshkina E, van der Kraaij E, Hoffmann AL. Simulation and experimental benchmarking of a proton pencil beam scanning nozzle model for development of MR-integrated proton therapy. Med Phys 2024. [PMID: 38949569 DOI: 10.1002/mp.17279] [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: 12/19/2023] [Revised: 06/18/2024] [Accepted: 06/20/2024] [Indexed: 07/02/2024] Open
Abstract
BACKGROUND MR-integrated proton therapy is under development. It consists of the unique challenge of integrating a proton pencil beam scanning (PBS) beam line nozzle with an magnetic resonance imaging (MRI) scanner. The magnetic interaction between these two components is deemed high risk as the MR images can be degraded if there is cross-talk during beam delivery and image acquisition. PURPOSE To create and benchmark a self-consistent proton PBS nozzle model for empowering the next stages of MR-integrated proton therapy development, namely exploring and de-risking complete integrated prototype system designs including magnetic shielding of the PBS nozzle. MATERIALS AND METHODS Magnetic field (COMSOL Multiphysics ${\text{Multiphysics}}$ ) and radiation transport (Geant4) models of a proton PBS nozzle located at OncoRay (Dresden, Germany) were developed according to the manufacturers specifications. Geant4 simulations of the PBS process were performed by using magnetic field data generated by the COMSOL Multiphysics ${\text{Multiphysics}}$ simulations. In total 315 spots were simulated which consisted of a40 × 30 cm 2 $40\times 30\,{\text{cm}}^{2}$ scan pattern with 5 cm spot spacings and for proton energies of 70, 100, 150, 200, and 220 MeV. Analysis of the simulated deflection at the beam isocenter plane was performed to determine the self-consistency of the model. The magnetic fringe field from a sub selection of 24 of the 315 spot simulations were directly compared with high precision magnetometer measurements. These focused on the maximum scanning setting of ± $\pm$ 20 cm beam deflection as generated from the second scanning magnet in the PBS for a proton beam energy of 220 MeV. Locations along the beam line central axis (CAX) were measured at beam isocenter and downstream of 22, 47, 72, 97, and 122 cm. Horizontal off-axis positions were measured at 22 cm downstream of isocenter ( ± $\pm$ 50, ± $\pm$ 100, and ± $\pm$ 150 cm from CAX). RESULTS The proton PBS simulations had good spatial agreement to the theoretical values in all 315 spots examined at the beam line isocenter plane (0-2.9 mm differences or within 1.5 % of the local spot deflection amount). Careful analysis of the experimental measurements were able to isolate the changes in magnetic fields due solely to the scanning magnet contribution, and showed 1.9 ± $\pm$ 1.2μ T $\bf{\mu} {\text{T}}$ -9.4 ± $\pm$ 1.2μ T $\bf{\mu} {\text{T}}$ changes over the range of measurement locations. Direct comparison with the equivalent simulations matched within the measurement apparatus and setup uncertainty in all but one measurement point. CONCLUSIONS For the first time a robust, accurate and self-consistent model of a proton PBS nozzle assembly has been created and successfully benchmarked for the purposes of advancing MR-integrated proton therapy research. The model will enable confidence in further simulation based work on fully integrated designs including MRI scanners and PBS nozzle magnetic shielding in order to de-risk and realize the full potential of MR-integrated proton therapy.
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Affiliation(s)
- Bradley M Oborn
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiooncology-OncoRay, Dresden, Germany
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, New South Wales, Australia
- Illawarra Cancer Care Centre, Wollongong, New South Wales, Australia
| | - Ekaterina Semioshkina
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiooncology-OncoRay, Dresden, Germany
- OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus at the Technische Universität Dresden, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany
| | | | - Aswin L Hoffmann
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiooncology-OncoRay, Dresden, Germany
- OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus at the Technische Universität Dresden, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany
- Department of Radiotherapy and Radiation Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus at the Technische Universität Dresden, Dresden, Germany
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Duetschler A, Safai S, Weber DC, Lomax AJ, Zhang Y. The impact of motion on onboard MRI-guided pencil beam scanned proton therapy treatments. Phys Med Biol 2024; 69:095003. [PMID: 38537287 DOI: 10.1088/1361-6560/ad3885] [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: 10/09/2023] [Accepted: 03/26/2024] [Indexed: 04/16/2024]
Abstract
Objective.Online magnetic resonance imaging (MRI) guidance could be especially beneficial for pencil beam scanned (PBS) proton therapy of tumours affected by respiratory motion. For the first time to our knowledge, we investigate the dosimetric impact of respiratory motion on MRI-guided proton therapy compared to the scenario without magnetic field.Approach.A previously developed analytical proton dose calculation algorithm accounting for perpendicular magnetic fields was extended to enable 4D dose calculations. For two geometrical phantoms and three liver and two lung patient cases, static treatment plans were optimised with and without magnetic field (0, 0.5 and 1.5 T). Furthermore, plans were optimised using gantry angle corrections (0.5 T +5° and 1.5 T +15°) to reproduce similar beam trajectories compared to the 0 T reference plans. The effect of motion was then considered using 4D dose calculations without any motion mitigation and simulating 8-times volumetric rescanning, with motion for the patient cases provided by 4DCT(MRI) data sets. Each 4D dose calculation was performed for different starting phases and the CTV dose coverageV95%and homogeneityD5%-D95%were analysed.Main results.For the geometrical phantoms with rigid motion perpendicular to the beam and parallel to the magnetic field, a comparable dosimetric effect was observed independent of the magnetic field. Also for the five 4DCT(MRI) cases, the influence of motion was comparable for all magnetic field strengths with and without gantry angle correction. On average, the motion-induced decrease in CTVV95%from the static plan was 17.0% and 18.9% for 1.5 T and 0.5 T, respectively, and 19.9% without magnetic field.Significance.For the first time, this study investigates the combined impact of magnetic fields and respiratory motion on MR-guided proton therapy. The comparable dosimetric effects irrespective of magnetic field strength indicate that the effects of motion for future MR-guided proton therapy may not be worse than for conventional PBS proton therapy.
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Affiliation(s)
- Alisha Duetschler
- Center for Proton Therapy, Paul Scherrer Institute, 5232 Villigen PSI, CH, Switzerland
- Department of Physics, ETH Zürich, 8092 Zürich, CH, Switzerland
| | - Sairos Safai
- Center for Proton Therapy, Paul Scherrer Institute, 5232 Villigen PSI, CH, Switzerland
| | - Damien C Weber
- Center for Proton Therapy, Paul Scherrer Institute, 5232 Villigen PSI, CH, Switzerland
- Department of Radiation Oncology, University Hospital of Zürich, 8091 Zürich, CH, Switzerland
- Department of Radiation Oncology, Inselspital, Bern University Hospital, University of Bern, 3010 Bern, CH, Switzerland
| | - Antony J Lomax
- Center for Proton Therapy, Paul Scherrer Institute, 5232 Villigen PSI, CH, Switzerland
- Department of Physics, ETH Zürich, 8092 Zürich, CH, Switzerland
| | - Ye Zhang
- Center for Proton Therapy, Paul Scherrer Institute, 5232 Villigen PSI, CH, Switzerland
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Gebauer B, Baumann KS, Fuchs H, Georg D, Oborn BM, Looe HK, Lühr A. Proton dosimetry in a magnetic field: Measurement and calculation of magnetic field correction factors for a plane-parallel ionization chamber. Med Phys 2024; 51:2293-2305. [PMID: 37898105 DOI: 10.1002/mp.16797] [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: 03/22/2023] [Revised: 08/31/2023] [Accepted: 09/04/2023] [Indexed: 10/30/2023] Open
Abstract
BACKGROUND The combination of magnetic resonance imaging and proton therapy offers the potential to improve cancer treatment. The magnetic field (MF)-dependent change in the dosage of ionization chambers in magnetic resonance imaging-integrated proton therapy (MRiPT) is considered by the correction factork B ⃗ , M , Q $k_{\vec{B},M,Q}$ , which needs to be determined experimentally or computed via Monte Carlo (MC) simulations. PURPOSE In this study,k B ⃗ , M , Q $k_{\vec{B},M,Q}$ was both measured and simulated with high accuracy for a plane-parallel ionization chamber at different clinical relevant proton energies and MF strengths. MATERIAL AND METHODS The dose-response of the Advanced Markus chamber (TM34045, PTW, Freiburg, Germany) irradiated with homogeneous 10 × $\times$ 10 cm2 $^2$ quasi mono-energetic fields, using 103.3, 128.4, 153.1, 223.1, and 252.7 MeV proton beams was measured in a water phantom placed in the MF of an electromagnet with MF strengths of 0.32, 0.5, and 1 T. The detector was positioned at a depth of 2 g/cm2 $^2$ in water, with chamber electrodes parallel to the MF lines and perpendicular to the proton beam incidence direction. The measurements were compared with TOPAS MC simulations utilizing COMSOL-calculated 0.32, 0.5, and 1 T MF maps of the electromagnet.k B ⃗ , M , Q $k_{\vec{B},M,Q}$ was calculated for the measurements for all energies and MF strengths based on the equation:k B ⃗ , M , Q = M Q M Q B ⃗ $k_{\vec{B},M,Q}=\frac{M_\mathrm{Q}}{M_\mathrm{Q}^{\vec{B}}}$ , whereM Q B ⃗ $M_\mathrm{Q}^{\vec{B}}$ andM Q $M_\mathrm{Q}$ were the temperature and air-pressure corrected detector readings with and without the MF, respectively. MC-based correction factors were determined ask B ⃗ , M , Q = D det D det B ⃗ $k_{\vec{B},M,Q}=\frac{D_\mathrm{det}}{D_\mathrm{det}^{\vec{B}}}$ , whereD det B ⃗ $D_\mathrm{det}^{\vec{B}}$ andD det $D_\mathrm{det}$ were the doses deposited in the air cavity of the ionization chamber model with and without the MF, respectively. Furthermore, MF effects on the chamber dosimetry are studied using MC simulations, examining the impact on the absorbed dose-to-water (D W $D_{W}$ ) and the shift in depth of the Bragg peak. RESULTS The detector showed a reduced dose-response for all measured energies and MF strengths, resulting in experimentally determinedk B ⃗ , M , Q $k_{\vec{B},M,Q}$ values larger than unity. For all energies and MF strengths examined,k B ⃗ , M , Q $k_{\vec{B},M,Q}$ ranged between 1.0065 and 1.0205. The dependence on the energy and the MF strength was found to be non-linear with a maximum at 1 T and 252.7 MeV. The MC simulatedk B ⃗ , M , Q $k_{\vec{B},M,Q}$ values agreed with the experimentally determined correction factors within their standard deviations with a maximum difference of 0.6%. The MC calculated impact onD W $D_{W}$ was smaller 0.2 %. CONCLUSION For the first time, measurements and simulations were compared for proton dosimetry within MFs using an Advanced Markus chamber. Good agreement ofk B ⃗ , M , Q $k_{\vec{B},M,Q}$ was found between experimentally determined and MC calculated values. The performed benchmarking of the MC code allows for calculatingk B ⃗ , M , Q $k_{\vec{B},M,Q}$ for various ionization chamber models, MF strengths and proton energies to generate the data needed for a proton dosimetry protocol within MFs and is, therefore, a step towards MRiPT.
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Affiliation(s)
- Benjamin Gebauer
- OncoRay National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany
- Institute of Radiooncology-OncoRay, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany
| | - Kilian-Simon Baumann
- Department of Radiotherapy and Radiooncology, University Medical Center Giessen-Marburg, Marburg, Germany
- University of Applied Sciences, Institute of Medical Physics and Radiation Protection, Giessen, Germany
- Ion-Beam Therapy Center, Marburg, Germany
| | - Hermann Fuchs
- Department of Radiation Oncology, Medical University of Vienna, Wien, Austria
- MedAustron Iontherapy centre, Wiener Neustadt, Austria
| | - Dietmar Georg
- Department of Radiation Oncology, Medical University of Vienna, Wien, Austria
- MedAustron Iontherapy centre, Wiener Neustadt, Austria
| | - Brad M Oborn
- Institute of Radiooncology-OncoRay, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, New South Wales, Australia
- Illawarra Cancer Care Centre, Wollongong, New South Wales, Australia
| | - Hui-Khee Looe
- Department for Radiotherapy and Radiooncology, Pius Hospital, Medical Campus Carl von Ossietzky University, Oldenburg, Germany
| | - Armin Lühr
- Department of Physics, TU Dortmund University, Dortmund, Germany
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Li S, Cheng B, Wang Y, Pei X, Xu XG. A GPU-based fast Monte Carlo code that supports proton transport in magnetic field for radiation therapy. J Appl Clin Med Phys 2024; 25:e14208. [PMID: 37987549 PMCID: PMC10795429 DOI: 10.1002/acm2.14208] [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: 06/04/2023] [Revised: 09/11/2023] [Accepted: 10/28/2023] [Indexed: 11/22/2023] Open
Abstract
This paper presents the effort to extend a previously reported code ARCHER, a GPU-based Monte Carlo (MC) code for coupled photon and electron transport, into protons including the consideration of magnetic fields. The proton transport is modeled using a Class-II condensed-history algorithm with continuous slowing-down approximation. The model includes ionization, multiple scattering, energy straggling, elastic and inelastic nuclear interactions, as well as deflection due to the Lorentz force in magnetic fields. An additional direction change is added for protons at the end of each step in the presence of the magnetic field. Secondary charge particles, except for protons, are terminated depositing kinetic energies locally, whereas secondary neutral particles are ignored. Each proton is transported step by step until its energy drops to below 0.5 MeV or when the proton leaves the phantom. The code is implemented using the compute unified device architecture (CUDA) platform for optimized GPU thread-level parallelism and efficiency. The code is validated by comparing it against TOPAS. Comparisons of dose distributions between our code and TOPAS for several exposure scenarios, ranging from single square beams in water to patient plan with magnetic fields, show good agreement. The 3D-gamma pass rate with a 2 mm/2% criterion in the region with dose greater than 10% of the maximum dose is computed to be over 99% for all tested cases. Using a single NVIDIA TITAN V GPU card, the computational time of ARCHER is found to range from 0.82 to 4.54 seconds for 1 × 107 proton histories. Compared to a few hours running on TOPAS, this speed improvement is significant. This work presents, for the first time, the performance of a GPU-based MC code to simulate proton transportation magnetic fields, demonstrating the feasibility of accurate and efficient dose calculations in potential magnetic resonance imaging (MRI)-guided proton therapy.
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Affiliation(s)
- Shijun Li
- School of Nuclear Science and TechnologyUniversity of Science and Technology of ChinaHefeiChina
| | - Bo Cheng
- School of Nuclear Science and TechnologyUniversity of Science and Technology of ChinaHefeiChina
| | - Yuxin Wang
- School of Nuclear Science and TechnologyUniversity of Science and Technology of ChinaHefeiChina
| | - Xi Pei
- Anhui Wisdom Technology Company LimitedHefeiAnhuiChina
| | - Xie George Xu
- School of Nuclear Science and TechnologyUniversity of Science and Technology of ChinaHefeiChina
- Department of Radiation OncologyThe First Affiliated Hospital of USTCUniversity of Science and Technology of ChinaHefeiChina
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Gebauer B, Pawelke J, Hoffmann A, Lühr A. Technical note: Experimental dosimetric characterization of proton pencil beam distortion in a perpendicular magnetic field of an in-beam MR scanner. Med Phys 2023; 50:7294-7303. [PMID: 37161832 DOI: 10.1002/mp.16448] [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: 10/28/2022] [Revised: 02/25/2023] [Accepted: 04/21/2023] [Indexed: 05/11/2023] Open
Abstract
BACKGROUND As it promises more precise and conformal radiation treatments, magnetic resonance imaging-integrated proton therapy (MRiPT) is seen as a next step in image guidance for proton therapy. The Lorentz force, which affects the course of the proton pencil beams, presents a problem for beam delivery in the presence of a magnetic field. PURPOSE To investigate the influence of the 0.32-T perpendicular magnetic field of an MR scanner on the delivery of proton pencil beams inside an MRiPT prototype system. METHODS An MRiPT prototype comprising of a horizontal pencil beam scanning beam line and an open 0.32-T MR scanner was used to evaluate the impact of the vertical magnetic field on proton beam deflection and dose spot pattern deformation. Three different proton energies (100, 150, and 220 MeV) and two spot map sizes (15 × 15 and 30 × 20 cm2 ) at four locations along the beam path without and with magnetic field were measured. Pencil-beam dose spots were measured using EBT3 films and a 2D scintillation detector. To study the magnetic field effects, a 2D Gaussian fit was applied to each individual dose spot to determine the central position( X , Y ) $(X,Y)$ , minimum and maximum lateral standard deviation (σ m i n $\sigma _{min}$ andσ m a x $\sigma _{max}$ ), orientation (θ), and the eccentricity (ε). RESULTS The dose spots were subjected to three simultaneous effects: (a) lateral horizontal beam deflection, (b) asymmetric trapezoidal deformation of the dose spot pattern, and (c) deformation and rotation of individual dose spots. The strongest effects were observed at a proton energy of 100 MeV with a horizontal beam deflection of 14-186 mm along the beam path. Within the central imaging field of the MR scanner, the maximum relative dose spot sizeσ m a x $\sigma _{max}$ decreased by up to 3.66%, whileσ m i n $\sigma _{min}$ increased by a maximum of 2.15%. The largest decrease and increase in the eccentricity of the dose spots were 0.08 and 0.02, respectively. The spot orientation θ was rotated by a maximum of 5.39°. At the higher proton energies, the same effects were still seen, although to a lesser degree. CONCLUSIONS The effect of an MRiPT prototype's magnetic field on the proton beam path, dose spot pattern, and dose spot form has been measured for the first time. The findings show that the impact of the MF must be appropriately recognized in a future MRiPT treatment planning system. The results emphasize the need for additional research (e.g., effect of magnetic field on proton beams with range shifters and impact of MR imaging sequences) before MRiPT applications can be employed to treat patients.
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Affiliation(s)
- Benjamin Gebauer
- OncoRay-National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany
- Institute of Radiooncology-OncoRay, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany
| | - Jörg Pawelke
- OncoRay-National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany
- Institute of Radiooncology-OncoRay, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany
| | - Aswin Hoffmann
- OncoRay-National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany
- Institute of Radiooncology-OncoRay, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany
- Department of Radiotherapy and Radiation Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | - Armin Lühr
- Department of Physics, TU Dortmund University, Dortmund, Germany
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Duetschler A, Winterhalter C, Meier G, Safai S, Weber DC, Lomax AJ, Zhang Y. A fast analytical dose calculation approach for MRI-guided proton therapy. Phys Med Biol 2023; 68:195020. [PMID: 37750045 DOI: 10.1088/1361-6560/acf90d] [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: 05/08/2023] [Accepted: 09/12/2023] [Indexed: 09/27/2023]
Abstract
Objective.Magnetic resonance (MR) is an innovative technology for online image guidance in conventional radiotherapy and is also starting to be considered for proton therapy as well. For MR-guided therapy, particularly for online plan adaptations, fast dose calculation is essential. Monte Carlo (MC) simulations, however, which are considered the gold standard for proton dose calculations, are very time-consuming. To address the need for an efficient dose calculation approach for MRI-guided proton therapy, we have developed a fast GPU-based modification of an analytical dose calculation algorithm incorporating beam deflections caused by magnetic fields.Approach.Proton beams (70-229 MeV) in orthogonal magnetic fields (0.5/1.5 T) were simulated using TOPAS-MC and central beam trajectories were extracted to generate look-up tables (LUTs) of incremental rotation angles as a function of water-equivalent depth. Beam trajectories are then reconstructed using these LUTs for the modified ray casting dose calculation. The algorithm was validated against MC in water, different materials and for four example patient cases, whereby it has also been fully incorporated into a treatment plan optimisation regime.Main results.Excellent agreement between analytical and MC dose distributions could be observed with sub-millimetre range deviations and differences in lateral shifts <2 mm even for high densities (1000 HU). 2%/2 mm gamma pass rates were comparable to the 0 T scenario and above 94.5% apart for the lung case. Further, comparable treatment plan quality could be achieved regardless of magnetic field strength.Significance.A new method for accurate and fast proton dose calculation in magnetic fields has been developed and successfully implemented for treatment plan optimisation.
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Affiliation(s)
- Alisha Duetschler
- Center for Proton Therapy, Paul Scherrer Institute, 5232 Villigen PSI, CH, Switzerland
- Department of Physics, ETH Zürich, 8092 Zürich, CH, Switzerland
| | - Carla Winterhalter
- Center for Proton Therapy, Paul Scherrer Institute, 5232 Villigen PSI, CH, Switzerland
| | - Gabriel Meier
- Center for Proton Therapy, Paul Scherrer Institute, 5232 Villigen PSI, CH, Switzerland
| | - Sairos Safai
- Center for Proton Therapy, Paul Scherrer Institute, 5232 Villigen PSI, CH, Switzerland
| | - Damien C Weber
- Center for Proton Therapy, Paul Scherrer Institute, 5232 Villigen PSI, CH, Switzerland
- Department of Radiation Oncology, University Hospital of Zürich, 8091 Zürich, CH, Switzerland
- Department of Radiation Oncology, Inselspital, Bern University Hospital, University of Bern, 3010 Bern, CH, Switzerland
| | - Antony J Lomax
- Center for Proton Therapy, Paul Scherrer Institute, 5232 Villigen PSI, CH, Switzerland
- Department of Physics, ETH Zürich, 8092 Zürich, CH, Switzerland
| | - Ye Zhang
- Center for Proton Therapy, Paul Scherrer Institute, 5232 Villigen PSI, CH, Switzerland
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Burigo LN, Oborn BM. Integrated MRI-guided proton therapy planning: accounting for the full MRI field in a perpendicular system. Med Phys 2021; 49:1853-1873. [PMID: 34908170 DOI: 10.1002/mp.15398] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2021] [Revised: 11/09/2021] [Accepted: 11/18/2021] [Indexed: 11/10/2022] Open
Abstract
PURPOSE To present a first study on the treatment planning feasibility in perpendicular field MRI-integrated proton therapy which considers the full transport of protons from the pencil beam scanning assembly to the patient inside the MRI scanner. METHODS A generic proton pencil beam scanning (PBS) gantry was modelled as being integrated with a realistic split-bore MRI system in the perpendicular orientation. MRI field strengths were modeled as 0.5 T, 1 T, and 1.5 T. The PBS beam delivery and dose calculation was modeled using the TOPAS Monte Carlo toolkit coupled with matRad as the optimizer engine. A water phantom, liver and prostate plans were evaluated and optimized in the presence of the full MRI field distribution. A simple combination of gantry angle offset and small PBS nozzle skew was used to direct the proton beams along a path that closely follows the reference planning scenario, i.e. without magnetic field. RESULTS All planning metrics could be successfully achieved with the inclusion of gantry angle offsets in the range of 8°-29° when coupled with a PBS nozzle skew of 1.6°-4.4°. These two hardware based corrections were selected to minimize the average Euclidean distance (AED) in the beam path enabling the proton beams to travel inside the patient in a path that is close to the original path (AED smaller than 3 mm at 1.5 T). Final dose optimization, performed through further changes in the pencil beam scanning delivery, was then shown to be feasible for our selection of plans studied yielding comparable plan quality metrics to reference conditions. CONCLUSIONS For the first time, we have shown a robust method to account for the full proton beam deflection in a perpendicular orientation MRI-integrated proton therapy. These results support the ongoing development of the current prototype systems. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Lucas N Burigo
- German Cancer Research Center (DKFZ), Heidelberg, 69120, Germany.,National Center for Radiation Research in Oncology (NCRO), Heidelberg Institute for Radiation Oncology (HIRO), Heidelberg, 69120, Germany
| | - Bradley M Oborn
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiooncology - OncoRay, Dresden, 01309, Germany.,Centre for Medical Radiation Physics (CMRP), University of Wollongong, Wollongong, NSW 2500, Australia.,Illawarra Cancer Care Centre (ICCC), Wollongong, NSW 2500, Australia
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Moteabbed M, Smeets J, Hong TS, Janssens G, Labarbe R, Wolfgang JA, Bortfeld TR. Toward MR-integrated proton therapy: modeling the potential benefits for liver tumors. Phys Med Biol 2021; 66. [PMID: 34407528 DOI: 10.1088/1361-6560/ac1ef2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2021] [Accepted: 08/18/2021] [Indexed: 12/25/2022]
Abstract
Magnetic resonance imaging (MRI)-integrated proton therapy (MRiPT) is envisioned to improve treatment quality for many cancer patients. However, given the availability of alternative image-guided strategies, its clinical need is yet to be justified. This study aims to compare the expected clinical outcomes of MRiPT with standard of practice cone-beam CT (CBCT)-guided PT, and other MR-guided methods, i.e. offline MR-guided PT and MR-linac, for treatment of liver tumors. Clinical outcomes were assessed by quantifying the dosimetric and biological impact of target margin reduction enabled by each image-guided approach. Planning target volume (PTV) margins were calculated using random and systematic setup, delineation and motion uncertainties, which were quantified by analyzing longitudinal MRI data for 10 patients with liver tumors. Proton treatment plans were created using appropriate PTV margins for each image-guided PT method. Photon plans with margins equivalent to MRiPT were generated to represent MR-linac. Normal tissue complication probabilities (NTCP) of the uninvolved liver were compared. We found that PTV margin can be reduced by 20% and 40% for offline MR-guided PT and MRiPT, respectively, compared with CBCT-guided PT. Furthermore, clinical target volume expansion could be largely alleviated when delineating on MRI rather than CT. Dosimetric implications included decreased equivalent mean dose of the uninvolved liver, i.e. up to 24.4 Gy and 27.3 Gy for offline MR-guided PT and MRiPT compared to CBCT-guided PT, respectively. Considering Child-Pugh score increase as endpoint, NTCP of the uninvolved liver was significantly decreased for MRiPT compared to CBCT-guided PT (up to 48.4%,p < 0.01), offline MR-guided PT (up to 12.9%,p < 0.01) and MR-linac (up to 30.8%,p < 0.05). Target underdose was possible in the absence of MRI-guidance (D90 reduction up to 4.2 Gy in 20% of cases). In conclusion, MRiPT has the potential to significantly reduce healthy liver toxicities in patients with liver tumors. It is superior to other image-guided techniques currently available.
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Affiliation(s)
- Maryam Moteabbed
- Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, United States of America
| | | | - Theodore S Hong
- Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, United States of America
| | | | - Rudi Labarbe
- Ion Beam Applications, Louvain-La-Neuve, Belguim
| | - John A Wolfgang
- Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, United States of America
| | - Thomas R Bortfeld
- Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, United States of America
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Wang X, Pan H, Cheng Q, Wang X, Xu W. Dosimetric Deviations of Bragg-Peak Position Shifts in Uniform Magnetic Fields for Magnetic Resonance Imaging-Guiding Proton Radiotherapy: A Monte Carlo Study. Front Public Health 2021; 9:641915. [PMID: 34414150 PMCID: PMC8369236 DOI: 10.3389/fpubh.2021.641915] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Accepted: 06/02/2021] [Indexed: 11/15/2022] Open
Abstract
Objective: To investigate dosimetric deviations in scanning protons for Bragg-peak position shifts, which were caused by proton spiral tracks in an ideal uniform field of magnetic resonance (MRI) imaging-guided proton radiotherapy (MRI-IGPRT). Methods: The FLUKA Monte-Carlo (MC) code was used to simulate the spiral tracks of protons penetrating water with initial energies of 70–270 MeV under the influence of field strength of 0.0–3.0 Tesla in commercial MRI systems. Two indexes, lateral shift (marked as WD) perpendicular to the field and a penetration-depth shift (marked as ΔDD) along the beam path, were employed for the Bragg-peak position of spiral proton track analysis. A comparison was performed between MC and classical analytical model to check the simulation results. The shape of the 2D/3D dose distribution of proton spots at the depth of Bragg-Peak was also investigated. The ratio of Gaussian-fit value between longitudinal and transverse major axes was used to indicate the asymmetric index. The skewness of asymmetry was evaluated at various dose levels by the radius ratio of circumscribed and inscribed circles by fitting a semi-ellipse circle of 2D distribution. Results: The maximum of WD deflection is 2.82 cm while the maximum of shortening ΔDD is 0.44 cm for proton at 270 MeV/u under a magnetic field of 3.0 Tesla. The trend of WD and ΔDD from MC simulation was consistent with the analytical model, which means the reverse equation of the analytical model can be applied to determine the proper field strength of the magnet and the initial energy of the proton for the planned dose. The asymmetry of 2D/3D dose distribution under the influence of a magnetic field was increased with higher energy, and the skewness of asymmetry for one proton energy at various dose levels was also increased with a larger radius, i.e., a lower dose level. Conclusions: The trend of the spiral proton track under a uniform magnetic field was obtained in this study using either MC simulation or the analytical model, which can provide an optimized and planned dose of the proton beam in the clinical application of MRI-IGPRT.
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Affiliation(s)
- Xiaowa Wang
- Department of Nulcear Science and Technology, Institute of Modern Physics, Fudan University, Shanghai, China.,Key Laboratory of Nuclear Physics and Ion-Beam Application (MOE), Fudan University, Shanghai, China.,Shanghai Proton and Heavy Ion Center, Shanghai, China.,Shanghai Engineering Research Center of Proton and Heavy Ion Radiation Therapy, Shanghai, China
| | - Hailun Pan
- Department of Nulcear Science and Technology, Institute of Modern Physics, Fudan University, Shanghai, China.,Key Laboratory of Nuclear Physics and Ion-Beam Application (MOE), Fudan University, Shanghai, China
| | - Qinqin Cheng
- Department of Nulcear Science and Technology, Institute of Modern Physics, Fudan University, Shanghai, China.,Key Laboratory of Nuclear Physics and Ion-Beam Application (MOE), Fudan University, Shanghai, China
| | - Xufei Wang
- Department of Nulcear Science and Technology, Institute of Modern Physics, Fudan University, Shanghai, China.,Key Laboratory of Nuclear Physics and Ion-Beam Application (MOE), Fudan University, Shanghai, China
| | - Wenzhen Xu
- Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai, China
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10
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Guerreiro F, Svensson S, Seravalli E, Traneus E, Raaymakers BW. Intra-fractional per-beam adaptive workflow to mitigate the need for a rotating gantry during MRI-guided proton therapy. Phys Med Biol 2021; 66. [PMID: 34298523 DOI: 10.1088/1361-6560/ac176f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Accepted: 07/23/2021] [Indexed: 11/12/2022]
Abstract
The integration of real-time magnetic resonance imaging (MRI)-guidance and proton therapy would potentially improve the proton dose steering capability by reducing daily uncertainties due to anatomical variations. The use of a fixed beamline coupled with an axial patient couch rotation would greatly simplify the proton delivery with MRI-guidance. Nonetheless, it is mandatory to assure that the plan quality is not deteriorated by the anatomical deformations due to patient rotation. In this work, an in-house tool allowing for intra-fractional per-beam adaptation of intensity-modulated proton plans (BeamAdapt) was implemented through features available in RayStation. A set of three MRIs was acquired for two healthy volunteers (V1, V2): (1) no rotation/static, (2) rotation to the right and (3) left. V1 was rotated by 15º, to simulate a clinical pediatric abdominal case and V2 by 45º, to simulate an extreme patient rotation case. For each volunteer, a total of four intensity-modulated pencil beam scanning plans were optimized on the static MRI using virtual abdominal targets and 2-3 posterior-oblique beams. Beam angles were defined according to the angulations on the rotated MRIs. With BeamAdapt, each original plan was first converted into separate plans with one beam per plan. In an iterative order, individual beam doses were non-rigidly deformed to the rotated anatomies and re-optimized accounting for the consequent deformations and the beam doses delivered so far. For evaluation, the final adapted dose distribution was propagated back to the static MRI. Planned and adapted dose distributions were compared by computing relative differences between dose-volume histogram (DVH) metrics. Absolute target dose differences were on average below 1% and mean dose organs-at-risk differences were below 3%. With BeamAdapt, not only intra-fractional per-beam proton plan adaptation coupled with axial patient rotation is possible but also the need for a rotating gantry during MRI-guidance might be mitigated.
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Affiliation(s)
- Filipa Guerreiro
- Department of Radiotherapy, University Medical Center Utrecht Imaging Division, Utrecht, NETHERLANDS
| | | | - Enrica Seravalli
- Department of Radiotherapy, University Medical Center Utrecht Imaging Division, Utrecht, NETHERLANDS
| | - Erik Traneus
- RaySearch Laboratories AB, Stockholm, Stockholm, SWEDEN
| | - Bas W Raaymakers
- Department of Radiotherapy, University Medical Center Utrecht Imaging Division, Utrecht, NETHERLANDS
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11
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Gantz S, Hietschold V, Hoffmann AL. Characterization of magnetic interference and image artefacts during simultaneous in-beam MR imaging and proton pencil beam scanning. Phys Med Biol 2020; 65:215014. [PMID: 33151908 DOI: 10.1088/1361-6560/abb16f] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
For the first time, a low-field open magnetic resonance (MR) scanner was combined with a proton pencil beam scanning (PBS) research beamline. The aim of this study was to characterize the magnetic fringe fields produced by the PBS system and measure their effects on MR image quality during simultaneous PBS irradiation and image acquisition. A magnetic field camera measured the change in central resonance frequency (Δf res) and magnetic field homogeneity (ΔMFH) of the B0 field of the MR scanner during operation of the beam transport and scanning magnets. The beam energy was varied between 70 - 220 MeV and beam scanning was performed along the central horizontal and vertical axis of a 48 × 24 cm2 radiation field. The time structure of the scanning magnets' fringe fields was simultaneously recorded by a tri-axial Hall probe. MR imaging experiments were conducted using the ACR (American College of Radiology) Small MRI Phantom and a spoiled gradient echo pulse sequence during simultaneous volumetric irradiation. Computer simulations were performed to predict the effects of B 0 field perturbations due to PBS irradiation on MR image formation in k-space. Setting the beam transport magnets, horizontal and vertical scanning magnets resulted in a maximum Δf res of 50, 235 and 4 Hz, respectively. The ΔMFH was less than 3 parts per million for all measurements. MR images acquired during beam energy variation and vertical beam scanning showed no visual loss in image quality. However, MR images acquired during horizontal beam scanning showed severe coherent ghosting artefacts in phase encoding direction. Both simulated and measured k-space phase maps prove that these artefacts are caused by phase-offsets. This study shows first experimental evidence that simultaneous in-beam MR imaging during proton PBS irradiation is subject to severe loss of image quality in the absence of magnetic decoupling between the PBS and MR system.
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Affiliation(s)
- Sebastian Gantz
- OncoRay-National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany. Institute of Radiooncology-OncoRay, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany
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12
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Implementation of a dose calculation algorithm based on Monte Carlo simulations for treatment planning towards MRI guided ion beam therapy. Phys Med 2020; 74:155-165. [DOI: 10.1016/j.ejmp.2020.04.027] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 04/17/2020] [Accepted: 04/26/2020] [Indexed: 12/30/2022] Open
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13
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Hoffmann A, Oborn B, Moteabbed M, Yan S, Bortfeld T, Knopf A, Fuchs H, Georg D, Seco J, Spadea MF, Jäkel O, Kurz C, Parodi K. MR-guided proton therapy: a review and a preview. Radiat Oncol 2020; 15:129. [PMID: 32471500 PMCID: PMC7260752 DOI: 10.1186/s13014-020-01571-x] [Citation(s) in RCA: 73] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Accepted: 05/17/2020] [Indexed: 02/14/2023] Open
Abstract
Background The targeting accuracy of proton therapy (PT) for moving soft-tissue tumours is expected to greatly improve by real-time magnetic resonance imaging (MRI) guidance. The integration of MRI and PT at the treatment isocenter would offer the opportunity of combining the unparalleled soft-tissue contrast and real-time imaging capabilities of MRI with the most conformal dose distribution and best dose steering capability provided by modern PT. However, hybrid systems for MR-integrated PT (MRiPT) have not been realized so far due to a number of hitherto open technological challenges. In recent years, various research groups have started addressing these challenges and exploring the technical feasibility and clinical potential of MRiPT. The aim of this contribution is to review the different aspects of MRiPT, to report on the status quo and to identify important future research topics. Methods Four aspects currently under study and their future directions are discussed: modelling and experimental investigations of electromagnetic interactions between the MRI and PT systems, integration of MRiPT workflows in clinical facilities, proton dose calculation algorithms in magnetic fields, and MRI-only based proton treatment planning approaches. Conclusions Although MRiPT is still in its infancy, significant progress on all four aspects has been made, showing promising results that justify further efforts for research and development to be undertaken. First non-clinical research solutions have recently been realized and are being thoroughly characterized. The prospect that first prototype MRiPT systems for clinical use will likely exist within the next 5 to 10 years seems realistic, but requires significant work to be performed by collaborative efforts of research groups and industrial partners.
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Affiliation(s)
- Aswin Hoffmann
- OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany.,Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiooncology-OncoRay, Dresden, Germany.,Department of Radiotherapy and Radiation Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | - Bradley Oborn
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, Australia.,Illawarra Cancer Care Centre, Wollongong Hospital, Wollongong, Australia
| | - Maryam Moteabbed
- Division of Radiation Biophysics, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, USA
| | - Susu Yan
- Division of Radiation Biophysics, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, USA
| | - Thomas Bortfeld
- Division of Radiation Biophysics, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, USA
| | - Antje Knopf
- Department of Radiation Oncology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Herman Fuchs
- Department of Radiation Oncology, Medical University of Vienna/AKH, Vienna, Austria.,Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna, Vienna, Austria
| | - Dietmar Georg
- Department of Radiation Oncology, Medical University of Vienna/AKH, Vienna, Austria.,Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna, Vienna, Austria
| | - Joao Seco
- Biomedical Physics in Radiation Oncology, Deutsches Krebsforschungszentrum DKFZ, Heidelberg, Germany.,Department of Physics and Astronomy, Heidelberg University, Heidelberg, Germany
| | - Maria Francesca Spadea
- Biomedical Physics in Radiation Oncology, Deutsches Krebsforschungszentrum DKFZ, Heidelberg, Germany.,Department of Experimental and Clinical Medicine, Magna Graecia University, Catanzaro, Italy
| | - Oliver Jäkel
- Medical Physics in Radiation Oncology, Deutsches Krebsforschungszentrum DKFZ and Heidelberg Ion-Beam Therapy Center at the University Medical Center, Heidelberg, Germany
| | - Christopher Kurz
- Department of Radiation Oncology, University Hospital, LMU Munich, Munich, Germany.,Department of Medical Physics, Faculty of Physics, Ludwig-Maximilians-Universität München, Garching, Germany
| | - Katia Parodi
- Department of Medical Physics, Faculty of Physics, Ludwig-Maximilians-Universität München, Garching, Germany.
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14
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Faddegon B, Ramos-Méndez J, Schuemann J, McNamara A, Shin J, Perl J, Paganetti H. The TOPAS tool for particle simulation, a Monte Carlo simulation tool for physics, biology and clinical research. Phys Med 2020; 72:114-121. [PMID: 32247964 DOI: 10.1016/j.ejmp.2020.03.019] [Citation(s) in RCA: 97] [Impact Index Per Article: 24.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Revised: 02/06/2020] [Accepted: 03/19/2020] [Indexed: 01/02/2023] Open
Abstract
PURPOSE This paper covers recent developments and applications of the TOPAS TOol for PArticle Simulation and presents the approaches used to disseminate TOPAS. MATERIALS AND METHODS Fundamental understanding of radiotherapy and imaging is greatly facilitated through accurate and detailed simulation of the passage of ionizing radiation through apparatus and into a patient using Monte Carlo (MC). TOPAS brings Geant4, a reliable, experimentally validated MC tool mainly developed for high energy physics, within easy reach of medical physicists, radiobiologists and clinicians. Requiring no programming knowledge, TOPAS provides all of the flexibility of Geant4. RESULTS After 5 years of development followed by its initial release, TOPAS was subsequently expanded from its focus on proton therapy physics to incorporate radiobiology modeling. Next, in 2018, the developers expanded their user support and code maintenance as well as the scope of TOPAS towards supporting X-ray and electron therapy and medical imaging. Improvements have been achieved in user enhancement through software engineering and a graphical user interface, calculational efficiency, validation through experimental benchmarks and QA measurements, and either newly available or recently published applications. A large and rapidly increasing user base demonstrates success in our approach to dissemination of this uniquely accessible and flexible MC research tool. CONCLUSIONS The TOPAS developers continue to make strides in addressing the needs of the medical community in applications of ionizing radiation to medicine, creating the only fully integrated platform for four-dimensional simulation of all forms of radiotherapy and imaging with ionizing radiation, with a design that promotes inter-institutional collaboration.
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Affiliation(s)
- Bruce Faddegon
- Department of Radiation Oncology, University of California San Francisco, San Francisco, CA, USA.
| | - José Ramos-Méndez
- Department of Radiation Oncology, University of California San Francisco, San Francisco, CA, USA
| | - Jan Schuemann
- Massachusetts General Hospital and Harvard Medical School, Boston, USA
| | - Aimee McNamara
- Massachusetts General Hospital and Harvard Medical School, Boston, USA
| | - Jungwook Shin
- Massachusetts General Hospital and Harvard Medical School, Boston, USA
| | - Joseph Perl
- SLAC National Accelerator Laboratory, Menlo Park, USA
| | - Harald Paganetti
- Massachusetts General Hospital and Harvard Medical School, Boston, USA
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15
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Padilla-Cabal F, Alejandro Fragoso J, Franz Resch A, Georg D, Fuchs H. Benchmarking a GATE/Geant4 Monte Carlo model for proton beams in magnetic fields. Med Phys 2019; 47:223-233. [PMID: 31661559 PMCID: PMC7003833 DOI: 10.1002/mp.13883] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Revised: 10/23/2019] [Accepted: 10/24/2019] [Indexed: 12/16/2022] Open
Abstract
Purpose Magnetic resonance guidance in proton therapy (MRPT) is expected to improve its current performance. The combination of magnetic fields with clinical proton beam lines poses several challenges for dosimetry, treatment planning and dose delivery. Proton beams are deflected by magnetic fields causing considerable changes in beam trajectories and also a retraction of the Bragg peak positions. A proper prediction and compensation of these effects is essential to ensure accurate dose calculations. This work aims to develop and benchmark a Monte Carlo (MC) beam model for dose calculation of MRPT for static magnetic fields up to 1 T. Methods Proton beam interactions with magnetic fields were simulated using the GATE/Geant4 toolkit. The transport of charged particle in custom 3D magnetic field maps was implemented for the first time in GATE. Validation experiments were done using a horizontal proton pencil beam scanning system with energies between 62.4 and 252.7 MeV and a large gap dipole magnet (B = 0–1 T), positioned at the isocenter and creating magnetic fields transverse to the beam direction. Dose was measured with Gafchromic EBT3 films within a homogeneous PMMA phantom without and with bone and tissue equivalent material slab inserts. Linear energy transfer (LET) quenching of EBT3 films was corrected using a linear model on dose‐averaged LET method to ensure a realistic dosimetric comparison between simulations and experiments. Planar dose distributions were measured with the films in two different configurations: parallel and transverse to the beam direction using single energy fields and spread‐out Bragg peaks. The MC model was benchmarked against lateral deflections and spot sizes in air of single beams measured with a Lynx PT detector, as well as dose distributions using EBT3 films. Experimental and calculated dose distributions were compared to test the accuracy of the model. Results Measured proton beam deflections in air at distances of 465, 665, and 1155 mm behind the isocenter after passing the magnetic field region agreed with MC‐predicted values within 4 mm. Differences between calculated and measured beam full width at half maximum (FWHM) were lower than 2 mm. For the homogeneous phantom, measured and simulated in‐depth dose profiles showed range and average dose differences below 0.2 mm and 1.2%, respectively. Simulated central beam positions and widths differed <1 mm to the measurements with films. For both heterogenous phantoms, differences within 1 mm between measured and simulated central beam positions and widths were obtained, confirming a good agreement of the MC model. Conclusions A GATE/Geant4 beam model for protons interacting with magnetic fields up to 1 T was developed and benchmarked to experimental data. For the first time, the GATE/Geant4 model was successfully validated not only for single energy beams, but for SOBP, in homogeneous and heterogeneous phantoms. EBT3 film dosimetry demonstrated to be a powerful dosimetric tool, once the film response function is LET corrected, for measurements in‐line and transverse to the beam direction in magnetic fields. The proposed MC beam model is foreseen to support treatment planning and quality assurance (QA) activities toward MRPT.
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Affiliation(s)
- Fatima Padilla-Cabal
- Department of Radiotherapy, Medical University of Vienna/AKH, Vienna, Austria.,Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna, Vienna, Austria
| | - Jose Alejandro Fragoso
- Department of Nuclear Physics, Higher Institute of Technologies and Applied Science, Havana, Cuba
| | - Andreas Franz Resch
- Department of Radiotherapy, Medical University of Vienna/AKH, Vienna, Austria.,Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna, Vienna, Austria
| | - Dietmar Georg
- Department of Radiotherapy, Medical University of Vienna/AKH, Vienna, Austria.,Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna, Vienna, Austria
| | - Hermann Fuchs
- Department of Radiotherapy, Medical University of Vienna/AKH, Vienna, Austria.,Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna, Vienna, Austria
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16
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Burigo LN, Oborn BM. MRI-guided proton therapy planning: accounting for an inline MRI fringe field. Phys Med Biol 2019; 64:215015. [PMID: 31509819 DOI: 10.1088/1361-6560/ab436a] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
MRI-guided proton therapy is being pursued for its promise to provide a more conformal, accurate proton therapy. However, the presence of the magnetic field imposes a challenge for the beam delivery as protons are deflected due to the Lorenz force. In this study, the impact of realistic inline MRI fringe field on IMPT plan delivery is investigated for a water phantom, liver tumor and prostate cancer differing in target volume, shape, and field configuration using Monte Carlo simulations. A method to correct for the shift of the beam spot positions in the presence of the inline magnetic field is presented. Results show that when not accounting for the effect of the magnetic field on the pencil beam delivery, the spot positions are substantially shifted and the quality of delivered plans is significantly deteriorated leading to dose inhomogeneities and creation of hot and cold spots. However, by correcting the pencil beam delivery, the dose quality of the IMPT plans is restored to a high degree. Nevertheless, adaptation of beam delivery alone is not robust regarding different treatment sites. By fully accounting during plan optimization for the dose distortions caused by the fringe and imaging fields, highly conformal IMPT plans are achieved. These results demonstrate proton pencil beam scanning and treatment planning can be adapted for precise delivery of state-of-the-art IMPT plans in MR-guided proton therapy in the presence of an inline MRI fringe field.
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Affiliation(s)
- Lucas N Burigo
- German Cancer Research Center (DKFZ), Heidelberg, Germany. National Center for Radiation Research in Oncology (NCRO), Heidelberg Institute for Radiation Oncology (HIRO) Heidelberg, Germany
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17
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Causer TJ, Schellhammer SM, Gantz S, Lühr A, Hoffmann AL, Metcalfe PE, Rosenfeld AB, Guatelli S, Petasecca M, Oborn BM. First application of a high-resolution silicon detector for proton beam Bragg peak detection in a 0.95 T magnetic field. Med Phys 2019; 47:181-189. [PMID: 31621914 DOI: 10.1002/mp.13871] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Revised: 10/09/2019] [Accepted: 10/10/2019] [Indexed: 11/12/2022] Open
Abstract
PURPOSE To report on experimental results of a high spatial resolution silicon-based detector exposed to therapeutic quality proton beams in a 0.95 T transverse magnetic field. These experimental results are important for the development of accurate and novel dosimetry methods in future potential real-time MRI-guided proton therapy systems. METHODS A permanent magnet device was utilized to generate a 0.95 T magnetic field over a 4 × 20 × 15 cm3 volume. Within this volume, a high-resolution silicon diode array detector was positioned inside a PMMA phantom of 4 × 15 × 12 cm3 . This detector contains two orthogonal strips containing 505 sensitive volumes spaced at 0.2 mm apart. Proton beams collimated to a circle of 10 mm diameter with nominal energies of 90 MeV, 110 MeV, and 125 MeV were incident on the detector from an edge-on orientation. This allows for a measurement of the Bragg peak at 0.2 mm spatial resolution in both the depth and lateral profile directions. The impact of the magnetic field on the proton beams, that is, a small deflection was also investigated. A Geant4 Monte Carlo simulation was performed of the experimental setup to aid in interpretation of the results. RESULTS The nominal Bragg peak for each proton energy was successfully observed with a 0.2 mm spatial resolution in the 0.95 T transverse magnetic field in both a depth and lateral profiles. The proton beam deflection (at 0.95 T) was a consistent 2 ±0.5 mm at the center of the magnetic volume for each beam energy. However, a pristine Bragg peak was not observed for each energy. This was caused by the detector packaging having small air gaps between layers of the phantom material surrounding the diode array. These air gaps act to degrade the shape of the Bragg peak, and further to this, the nonwater equivalent silicon chip acts to separate the Bragg peak into multiple peaks depending on the proton path taken. Overall, a promising performance of the silicon detector array was observed, however, with a qualitative assessment rather than a robust quantitative dosimetric evaluation at this stage of development. CONCLUSIONS For the first time, a high-resolution silicon-based radiation detector has been used to measure proton beam Bragg peak deflections in a phantom due to a strong magnetic field. Future efforts are required to optimize the detector packaging to strengthen the robustness of the dosimetric quantities obtained from the detector. Such high-resolution silicon diode arrays may be useful in future efforts in MRI-guided proton therapy research.
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Affiliation(s)
- Trent J Causer
- Illawarra Cancer Care Centre, Wollongong, NSW, 2500, Australia.,Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, 2500, Australia
| | - Sonja M Schellhammer
- Helmholtz-Zentrum Dresden - Rossendorf, Institute of Radiooncology, Dresden, Germany.,OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universitt Dresden, Helmholtz-Zentrum Dresden - Rossendorf, Dresden, Germany
| | - Sebastian Gantz
- Helmholtz-Zentrum Dresden - Rossendorf, Institute of Radiooncology, Dresden, Germany.,OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universitt Dresden, Helmholtz-Zentrum Dresden - Rossendorf, Dresden, Germany
| | - Armin Lühr
- Helmholtz-Zentrum Dresden - Rossendorf, Institute of Radiooncology, Dresden, Germany.,OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universitt Dresden, Helmholtz-Zentrum Dresden - Rossendorf, Dresden, Germany.,German Cancer Consortium DKTK, Partner Site Dresden, Dresden, Germany
| | - Aswin L Hoffmann
- Helmholtz-Zentrum Dresden - Rossendorf, Institute of Radiooncology, Dresden, Germany.,OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universitt Dresden, Helmholtz-Zentrum Dresden - Rossendorf, Dresden, Germany.,Dept. of Radiotherapy and Radiation Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus at the Technische Universitat Dresden, Dresden, Germany
| | - Peter E Metcalfe
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, 2500, Australia.,Ingham Institute for Applied Medical Research, Liverpool, NSW, 2170, Australia
| | - Anatoly B Rosenfeld
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, 2500, Australia
| | - Susanna Guatelli
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, 2500, Australia
| | - Marco Petasecca
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, 2500, Australia
| | - Bradley M Oborn
- Illawarra Cancer Care Centre, Wollongong, NSW, 2500, Australia.,Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, 2500, Australia
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18
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Bertholet J, Knopf A, Eiben B, McClelland J, Grimwood A, Harris E, Menten M, Poulsen P, Nguyen DT, Keall P, Oelfke U. Real-time intrafraction motion monitoring in external beam radiotherapy. Phys Med Biol 2019; 64:15TR01. [PMID: 31226704 PMCID: PMC7655120 DOI: 10.1088/1361-6560/ab2ba8] [Citation(s) in RCA: 113] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Revised: 05/10/2019] [Accepted: 06/21/2019] [Indexed: 12/25/2022]
Abstract
Radiotherapy (RT) aims to deliver a spatially conformal dose of radiation to tumours while maximizing the dose sparing to healthy tissues. However, the internal patient anatomy is constantly moving due to respiratory, cardiac, gastrointestinal and urinary activity. The long term goal of the RT community to 'see what we treat, as we treat' and to act on this information instantaneously has resulted in rapid technological innovation. Specialized treatment machines, such as robotic or gimbal-steered linear accelerators (linac) with in-room imaging suites, have been developed specifically for real-time treatment adaptation. Additional equipment, such as stereoscopic kilovoltage (kV) imaging, ultrasound transducers and electromagnetic transponders, has been developed for intrafraction motion monitoring on conventional linacs. Magnetic resonance imaging (MRI) has been integrated with cobalt treatment units and more recently with linacs. In addition to hardware innovation, software development has played a substantial role in the development of motion monitoring methods based on respiratory motion surrogates and planar kV or Megavoltage (MV) imaging that is available on standard equipped linacs. In this paper, we review and compare the different intrafraction motion monitoring methods proposed in the literature and demonstrated in real-time on clinical data as well as their possible future developments. We then discuss general considerations on validation and quality assurance for clinical implementation. Besides photon RT, particle therapy is increasingly used to treat moving targets. However, transferring motion monitoring technologies from linacs to particle beam lines presents substantial challenges. Lessons learned from the implementation of real-time intrafraction monitoring for photon RT will be used as a basis to discuss the implementation of these methods for particle RT.
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Affiliation(s)
- Jenny Bertholet
- Joint Department of Physics, Institute of Cancer Research and Royal Marsden NHS
Foundation Trust, London, United
Kingdom
- Author to whom any correspondence should be
addressed
| | - Antje Knopf
- Department of Radiation Oncology,
University Medical Center
Groningen, University of Groningen, The
Netherlands
| | - Björn Eiben
- Department of Medical Physics and Biomedical
Engineering, Centre for Medical Image Computing, University College London, London,
United Kingdom
| | - Jamie McClelland
- Department of Medical Physics and Biomedical
Engineering, Centre for Medical Image Computing, University College London, London,
United Kingdom
| | - Alexander Grimwood
- Joint Department of Physics, Institute of Cancer Research and Royal Marsden NHS
Foundation Trust, London, United
Kingdom
| | - Emma Harris
- Joint Department of Physics, Institute of Cancer Research and Royal Marsden NHS
Foundation Trust, London, United
Kingdom
| | - Martin Menten
- Joint Department of Physics, Institute of Cancer Research and Royal Marsden NHS
Foundation Trust, London, United
Kingdom
| | - Per Poulsen
- Department of Oncology, Aarhus University Hospital, Aarhus,
Denmark
| | - Doan Trang Nguyen
- ACRF Image X Institute, University of Sydney, Sydney,
Australia
- School of Biomedical Engineering,
University of Technology
Sydney, Sydney, Australia
| | - Paul Keall
- ACRF Image X Institute, University of Sydney, Sydney,
Australia
| | - Uwe Oelfke
- Joint Department of Physics, Institute of Cancer Research and Royal Marsden NHS
Foundation Trust, London, United
Kingdom
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19
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Padilla-Cabal F, Kuess P, Georg D, Palmans H, Fetty L, Fuchs H. Characterization of EBT3 radiochromic films for dosimetry of proton beams in the presence of magnetic fields. Med Phys 2019; 46:3278-3284. [PMID: 31055847 PMCID: PMC6852248 DOI: 10.1002/mp.13567] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 04/04/2019] [Accepted: 04/20/2019] [Indexed: 11/05/2022] Open
Abstract
PURPOSE Radiochromic film dosimetry is extensively used for quality assurance in photon and proton beam therapy. So far, GafchromicTM EBT3 film appears as a strong candidate to be used in future magnetic resonance (MR) based therapy systems. The response of Gafchromic EBT3 films in the presence of magnetic fields has already been addressed for different MR-linacs systems. However, a detailed evaluation of the influence of external magnetic fields on the film response and calibration curves for proton therapy has not yet been reported. This study aims to determine the dose responses of EBT3 films for clinical proton beams exposed to magnetic field strengths up to 1 T in order to investigate the feasibility of EBT3 film as an accurate dosimetric tool for a future MR particle therapy system (MRPT). METHODS The dosimetric characteristics of EBT3 films were studied for a proton beam passing through magnetic field strengths of B = 0, 0.5, and 1 T. Absorbed dose calibration and measurements were performed using clinical proton beams in the nominal energy range of 62.4-252.6 MeV. Irradiations were done using an in-house developed PMMA slab phantom placed in the center of a dipole research magnet. Monte Carlo (MC) simulations using the GATE/Geant4 toolkit were performed to predict the effect of magnetic fields on the energy deposited by proton beams in the phantom. Planned and measured doses from 3D box cube irradiations were compared to assess the accuracy of the dosimetric method using EBT3 films with/without the external magnetic field. RESULTS Neither for the mean pixel value nor for the net optical density, any significant deviations were observed due to the presence of an external magnetic field (B ≤ 1T) for doses up to 10 Gy. Dose-response curves for the red channel were fitted by a three-parameter function for the field-free case and for B = 1T, showing for both cases an R-square coefficient of unity and almost identical fitting parameters. Independently of the magnetic field, EBT3 films showed an under-response as high as 8% in the Bragg peak region, similarly to previously reported effects for particle therapy. No noticeable influence of the magnetic field strength was observed on the quenching effect of the EBT3 films. CONCLUSIONS For the first time detailed absorbed dose calibrations of EBT3 films for proton beams in magnetic field regions were performed. Results showed that EBT3 films represent an attractive solution for the dosimetry of a future MRPT system. As film response functions for protons are not affected by the magnetic field strenght, they can be used for further investigations to evaluate the dosimetric effects induced due to particle beams bending in magnetic fields regions.
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Affiliation(s)
- Fatima Padilla-Cabal
- Department of Radiotherapy, Medical University of Vienna/AKH, Vienna, Austria.,Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna, Vienna, Austria
| | - Peter Kuess
- Department of Radiotherapy, Medical University of Vienna/AKH, Vienna, Austria.,Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna, Vienna, Austria
| | - Dietmar Georg
- Department of Radiotherapy, Medical University of Vienna/AKH, Vienna, Austria.,Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna, Vienna, Austria
| | - Hugo Palmans
- EBG MedAustron GmbH, Wiener Neustadt, Austria.,National Physical Laboratory, Teddington, TW 11 0LW, UK
| | - Lukas Fetty
- Department of Radiotherapy, Medical University of Vienna/AKH, Vienna, Austria.,Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna, Vienna, Austria
| | - Hermann Fuchs
- Department of Radiotherapy, Medical University of Vienna/AKH, Vienna, Austria.,Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna, Vienna, Austria
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20
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Monte Carlo assessment of beam deflection and depth dose equivalent variation of a carbon-ion beam in a perpendicular magnetic field. Phys Med 2019; 61:33-43. [DOI: 10.1016/j.ejmp.2019.04.016] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/05/2018] [Revised: 04/13/2019] [Accepted: 04/19/2019] [Indexed: 11/22/2022] Open
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21
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Santos DM, Wachowicz K, Burke B, Fallone BG. Proton beam behavior in a parallel configured
MRI
‐proton therapy hybrid: Effects of time‐varying gradient magnetic fields. Med Phys 2018; 46:822-838. [DOI: 10.1002/mp.13309] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Revised: 11/18/2018] [Accepted: 11/19/2018] [Indexed: 01/01/2023] Open
Affiliation(s)
- D. M. Santos
- Department of Medical Physics Cross Cancer Institute 11560 University Avenue AB T6G 1Z2 Canada
| | - K. Wachowicz
- Department of Medical Physics Cross Cancer Institute 11560 University Avenue AB T6G 1Z2 Canada
- Department of Oncology Medical Physics Division University of Alberta 11560 University Avenue Edmonton AB T6G 1Z2 Canada
| | - B. Burke
- Department of Oncology Medical Physics Division University of Alberta 11560 University Avenue Edmonton AB T6G 1Z2 Canada
| | - B. G. Fallone
- Department of Medical Physics Cross Cancer Institute 11560 University Avenue AB T6G 1Z2 Canada
- Department of Oncology Medical Physics Division University of Alberta 11560 University Avenue Edmonton AB T6G 1Z2 Canada
- Department of Physics University of Alberta 11322 – 89 Avenue Edmonton AB T6G 2G7 Canada
- MagnetTx Oncology Solutions, Ltd. PO Box 52112 Edmonton AB Canada
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22
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Landry G, Hua CH. Current state and future applications of radiological image guidance for particle therapy. Med Phys 2018; 45:e1086-e1095. [PMID: 30421805 DOI: 10.1002/mp.12744] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Revised: 10/25/2017] [Accepted: 11/30/2017] [Indexed: 12/27/2022] Open
Abstract
In this review paper, we first give a short overview of radiological image guidance in photon radiotherapy, placing emphasis on the fact that linac based radiotherapy has outpaced particle therapy in the adoption of volumetric image guidance. While cone beam computed tomography (CBCT) has been an established technique in linac treatment rooms for almost two decades, the widespread adoption of volumetric image guidance in particle therapy, whether by means of CBCT or in-room CT imaging, is recent. This lag may be attributable to the bespoke nature and lower number of particle therapy installations, as well as the differences in geometry between those installations and linac treatment rooms. In addition, for particle therapy the so called shift invariance of the dose distribution rarely applies. An overview of the different volumetric image guidance solutions found at modern particle therapy facilities is provided, covering gantry, nozzle, C-arm, and couch-mounted CBCT as well different in-room CT configurations. A summary of the use of in-room volumetric imaging data beyond anatomy-based positioning is also presented as well as the necessary corrections to CBCT images for accurate water equivalent thickness calculation. Finally, the use of non-ionizing imaging modalities is discussed.
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Affiliation(s)
- Guillaume Landry
- Faculty of Physics, Department of Medical Physics, Ludwig-Maximilians-Universität München (LMU Munich), 85748, Garching b. München, Germany
| | - Chia-Ho Hua
- Department of Radiation Oncology, St. Jude Children's Research Hospital, Memphis, TN, 38105, USA
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23
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Schellhammer SM, Hoffmann AL, Gantz S, Smeets J, van der Kraaij E, Quets S, Pieck S, Karsch L, Pawelke J. Integrating a low-field open MR scanner with a static proton research beam line: proof of concept. Phys Med Biol 2018; 63:23LT01. [PMID: 30465549 DOI: 10.1088/1361-6560/aaece8] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
On-line image guidance using magnetic resonance (MR) imaging is expected to improve the targeting accuracy of proton therapy. However, to date no combined system exists. In this study, for the first time a low-field open MR scanner was integrated with a static proton research beam line to test the feasibility of simultaneous irradiation and imaging. The field-of-view of the MR scanner was aligned with the beam by taking into account the Lorentz force induced beam deflection. Various imaging sequences for extremities were performed on a healthy volunteer and on a patient with a soft-tissue sarcoma of the upper arm, both with the proton beam line switched off. T 1-weighted spin echo images of a tissue-mimicking phantom were acquired without beam, with energised beam line magnets and during proton irradiation. Beam profiles were acquired for the MR scanner's static magnetic field alone and in combination with the dynamic gradient fields during the acquisition of different imaging sequences. It was shown that MR imaging is feasible in the electromagnetically contaminated environment of a proton therapy facility. The observed quality of the anatomical MR images was rated to be sufficient for target volume definition and positioning. The tissue-mimicking phantom showed no visible beam-induced image degradation. The beam profiles depicted no influence due to the dynamic gradient fields of the imaging sequences. This study proves that simultaneous irradiation and in-beam MR imaging is technically feasible with a low-field MR scanner integrated with a static proton research beam line.
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Affiliation(s)
- Sonja M Schellhammer
- OncoRay-National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany. Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiooncology-OncoRay, Dresden, Germany. Both authors contributed equally to this work
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24
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Paganelli C, Whelan B, Peroni M, Summers P, Fast M, van de Lindt T, McClelland J, Eiben B, Keall P, Lomax T, Riboldi M, Baroni G. MRI-guidance for motion management in external beam radiotherapy: current status and future challenges. Phys Med Biol 2018; 63:22TR03. [PMID: 30457121 DOI: 10.1088/1361-6560/aaebcf] [Citation(s) in RCA: 83] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
High precision conformal radiotherapy requires sophisticated imaging techniques to aid in target localisation for planning and treatment, particularly when organ motion due to respiration is involved. X-ray based imaging is a well-established standard for radiotherapy treatments. Over the last few years, the ability of magnetic resonance imaging (MRI) to provide radiation-free images with high-resolution and superb soft tissue contrast has highlighted the potential of this imaging modality for radiotherapy treatment planning and motion management. In addition, these advantageous properties motivated several recent developments towards combined MRI radiation therapy treatment units, enabling in-room MRI-guidance and treatment adaptation. The aim of this review is to provide an overview of the state-of-the-art in MRI-based image guidance for organ motion management in external beam radiotherapy. Methodological aspects of MRI for organ motion management are reviewed and their application in treatment planning, in-room guidance and adaptive radiotherapy described. Finally, a roadmap for an optimal use of MRI-guidance is highlighted and future challenges are discussed.
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Affiliation(s)
- C Paganelli
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milano, Italy. Author to whom any correspondence should be addressed. www.cartcas.polimi.it
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25
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Mori S, Knopf A, Umegaki K. Motion management in particle therapy. Med Phys 2018; 45:e994-e1010. [DOI: 10.1002/mp.12679] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Revised: 10/24/2017] [Accepted: 11/07/2017] [Indexed: 11/08/2022] Open
Affiliation(s)
- Shinichiro Mori
- Research Center for Charged Particle Therapy National Institute of Radiological Sciences Chiba 263‐8555Japan
| | - Antje‐Christin Knopf
- Department of Radiation Oncology University of Groningen University Medical Center Groningen Groningen 9713 GZ The Netherlands
| | - Kikuo Umegaki
- Faculty of Engineering Division of Quantum Science and Engineering Hokkaido University Sapporo 060‐8628 Japan
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26
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Trnková P, Knäusl B, Actis O, Bert C, Biegun AK, Boehlen TT, Furtado H, McClelland J, Mori S, Rinaldi I, Rucinski A, Knopf AC. Clinical implementations of 4D pencil beam scanned particle therapy: Report on the 4D treatment planning workshop 2016 and 2017. Phys Med 2018; 54:121-130. [PMID: 30337001 DOI: 10.1016/j.ejmp.2018.10.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Revised: 09/18/2018] [Accepted: 10/02/2018] [Indexed: 12/14/2022] Open
Abstract
In 2016 and 2017, the 8th and 9th 4D treatment planning workshop took place in Groningen (the Netherlands) and Vienna (Austria), respectively. This annual workshop brings together international experts to discuss research, advances in clinical implementation as well as problems and challenges in 4D treatment planning, mainly in spot scanned proton therapy. In the last two years several aspects like treatment planning, beam delivery, Monte Carlo simulations, motion modeling and monitoring, QA phantoms as well as 4D imaging were thoroughly discussed. This report provides an overview of discussed topics, recent findings and literature review from the last two years. Its main focus is to highlight translation of 4D research into clinical practice and to discuss remaining challenges and pitfalls that still need to be addressed and to be overcome.
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Affiliation(s)
- Petra Trnková
- HollandPTC, P.O. Box 5046, 2600 GA Delft, the Netherlands; Erasmus MC, P.O. Box 5201, 3008 AE Rotterdam, the Netherlands
| | - Barbara Knäusl
- Department of Radiation Oncology, Division of Medical Radiation Physics, Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna/AKH Vienna, Austria
| | - Oxana Actis
- Paul Scherrer Institute (PSI), 5232 Villigen, Switzerland
| | - Christoph Bert
- Department of Radiation Oncology, Universitätsklinikum Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany
| | - Aleksandra K Biegun
- KVI-Center for Advanced Radiation Technology, University of Groningen, Groningen, the Netherlands
| | - Till T Boehlen
- Paul Scherrer Institute (PSI), 5232 Villigen, Switzerland
| | - Hugo Furtado
- Department of Radiation Oncology, Division of Medical Radiation Physics, Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna/AKH Vienna, Austria
| | - Jamie McClelland
- Centre for Medical Image Computing, Dept. Medical Physics and Biomedical, University College London, London, UK
| | - Shinichiro Mori
- National Institute of Radiological Sciences for Charged Particle Therapy, Chiba, Japan
| | - Ilaria Rinaldi
- Lyon 1 University and CNRS/IN2P3, UMR 5822, 69622 Villeurbanne, France; MAASTRO Clinic, P.O. Box 3035, 6202 NA Maastricht, the Netherlands
| | | | - Antje C Knopf
- University of Groningen, University Medical Center Groningen, Department of Radiation Oncology, Groningen, the Netherlands.
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27
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Schellhammer SM, Gantz S, Lühr A, Oborn BM, Bussmann M, Hoffmann AL. Technical Note: Experimental verification of magnetic field-induced beam deflection and Bragg peak displacement for MR-integrated proton therapy. Med Phys 2018; 45:3429-3434. [PMID: 29763970 DOI: 10.1002/mp.12961] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Revised: 03/26/2018] [Accepted: 04/16/2018] [Indexed: 11/10/2022] Open
Abstract
PURPOSE Given its sensitivity to anatomical variations, proton therapy is expected to benefit greatly from integration with magnetic resonance imaging for online anatomy monitoring during irradiation. Such an integration raises several challenges, as both systems mutually interact. The proton beam will experience quasi-continuous energy loss and energy-dependent electromagnetic deflection at the same time, giving rise to a deflected beam trajectory and an altered dose distribution with a displaced Bragg peak. So far, these effects have only been predicted using Monte Carlo and analytical models, but no clear consensus has been reached and experimental benchmark data are lacking. We measured proton beam trajectories and Bragg peak displacement in a homogeneous phantom placed inside a magnetic field and compared them to simulations. METHODS Planar dose distributions of proton pencil beams (80-180 MeV) traversing the field of a 0.95 T NdFeB permanent magnet while depositing energy in a PMMA slab phantom were measured using EBT3 radiochromic films and simulated using the Geant4 toolkit. Deflected beam trajectories and the Bragg peak displacement were extracted from the measured planar dose distributions and compared against the simulations. RESULTS The lateral beam deflection was clearly visible on the EBT3 films and ranged from 1 to 10 mm for 80 to 180 MeV, respectively. Simulated and measured beam trajectories and Bragg peak displacement agreed within 0.8 mm for all studied proton energies. CONCLUSIONS These results prove that the magnetic field-induced Bragg peak displacement is both measurable and accurately predictable in a homogeneous phantom at 0.95 T, and allows Monte Carlo simulations to be used as gold standard for proton beam trajectory prediction in similar frameworks for MR-integrated proton therapy.
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Affiliation(s)
- Sonja M Schellhammer
- OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden - Rossendorf, Dresden, 01307, Germany.,Institute of Radiooncology - OncoRay, Helmholtz-Zentrum Dresden - Rossendorf, Dresden, 01328, Germany
| | - Sebastian Gantz
- OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden - Rossendorf, Dresden, 01307, Germany.,Institute of Radiooncology - OncoRay, Helmholtz-Zentrum Dresden - Rossendorf, Dresden, 01328, Germany
| | - Armin Lühr
- OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden - Rossendorf, Dresden, 01307, Germany.,Institute of Radiooncology - OncoRay, Helmholtz-Zentrum Dresden - Rossendorf, Dresden, 01328, Germany.,German Cancer Consortium (DKTK), Partner Site Dresden, and German Cancer Research Center (DKFZ), Heidelberg, 69120, Germany
| | - Bradley M Oborn
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, 2522, Australia.,Illawarra Cancer Care Centre, Wollongong Hospital, Wollongong, 2522, Australia
| | - Michael Bussmann
- Institute of Radiation Physics, Helmholtz-Zentrum Dresden - Rossendorf, Dresden, 01328, Germany
| | - Aswin L Hoffmann
- OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden - Rossendorf, Dresden, 01307, Germany.,Institute of Radiooncology - OncoRay, Helmholtz-Zentrum Dresden - Rossendorf, Dresden, 01328, Germany.,Department of Radiotherapy and Radiation Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, 01307, Germany
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28
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Padilla-Cabal F, Georg D, Fuchs H. A pencil beam algorithm for magnetic resonance image-guided proton therapy. Med Phys 2018. [PMID: 29532490 PMCID: PMC5969113 DOI: 10.1002/mp.12854] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Purpose The feasibility of magnetic resonance image (MRI)‐based proton therapy is based, among several other factors, on the implementation of appropriate extensions on current dose calculation methods. This work aims to develop a pencil beam algorithm (PBA) for dose calculation of proton beams within magnetic field regions of up to 3 T. Methods Monte Carlo (MC) simulations using the GATE 7.1/GEANT4.9.4p02 toolkit were performed to generate calibration and benchmarking data for the PBA. Dose distributions from proton beams in the clinical required energy range 60–250 MeV impinging on a 400 × 400 × 400 mm3 water phantom and transverse magnetic fields ranging from 0 to 3 T were considered. Energy depositions in homogeneous and heterogeneous phantoms filled with water, adipose, bone, and air were evaluated for proton energies of 80, 150, and 240 MeV, combining a trajectory calculation method and look‐up tables (LUT). A novel parametrization model, using independent tailed Gauss fitting functions, was employed to describe the nonsymmetric shape of lateral beam profiles. Integrated depth‐dose curves (IDD), lateral dose profiles, and two‐dimensional dose distributions calculated with the PBA were compared with results from MC simulations to assess the performance of the algorithm. A gamma index criterion of 2%/2 mm was used for analysis. Results A close to perfect agreement was observed for PB‐based dose calculations in water in magnetic fields of 0.5, 1.5, and 3 T. IDD functions showed differences between the PBA and MC of less than 0.1% before the Bragg peak, and deviations of 2–8% in the distal energy falloff region. Gamma index pass rates higher than 99% and mean values lower than 0.1 were encountered for all analyzed configurations. For homogeneous phantoms, only the full bone configuration offered deviations in the Bragg peak position of up to 1.7% and overestimations of the lateral beam spot width for high‐energy protons and magnetic field intensities. An excellent agreement between PBA and MC dose calculation was also achieved using slab‐like and lateral heterogeneous phantoms, with gamma index passing rates above 98% and mean values between 0.1 and 0.2. As expected, agreement reduced for high‐energy protons and high‐intensity magnetic fields, although results remained good enough to be considered for future implementation in clinical practice. Conclusions The proposed pencil beam algorithm for protons can accurately account for dose distortion effects induced by external magnetic fields. The application of an analytical model for dose estimation and corrections reduces the calculation times considerably, making the presented PBA a suitable candidate for integration in a treatment planning system.
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Affiliation(s)
- Fatima Padilla-Cabal
- Department of Radiotherapy, Medical University of Vienna/AKH, Vienna, Austria.,Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna, Vienna, Austria
| | - Dietmar Georg
- Department of Radiotherapy, Medical University of Vienna/AKH, Vienna, Austria.,Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna, Vienna, Austria
| | - Hermann Fuchs
- Department of Radiotherapy, Medical University of Vienna/AKH, Vienna, Austria.,Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna, Vienna, Austria
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29
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Hartman J, Zhang X, Zhu XR, Frank SJ, Lagendijk JJW, Raaymakers BW. TOPAS Monte Carlo model of MD anderson scanning proton beam for simulation studies in proton therapy. Biomed Phys Eng Express 2018. [DOI: 10.1088/2057-1976/aab191] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
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30
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Maspero M, van den Berg CAT, Landry G, Belka C, Parodi K, Seevinck PR, Raaymakers BW, Kurz C. Feasibility of MR-only proton dose calculations for prostate cancer radiotherapy using a commercial pseudo-CT generation method. Phys Med Biol 2017; 62:9159-9176. [PMID: 29076458 DOI: 10.1088/1361-6560/aa9677] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
A magnetic resonance (MR)-only radiotherapy workflow can reduce cost, radiation exposure and uncertainties introduced by CT-MRI registration. A crucial prerequisite is generating the so called pseudo-CT (pCT) images for accurate dose calculation and planning. Many pCT generation methods have been proposed in the scope of photon radiotherapy. This work aims at verifying for the first time whether a commercially available photon-oriented pCT generation method can be employed for accurate intensity-modulated proton therapy (IMPT) dose calculation. A retrospective study was conducted on ten prostate cancer patients. For pCT generation from MR images, a commercial solution for creating bulk-assigned pCTs, called MR for Attenuation Correction (MRCAT), was employed. The assigned pseudo-Hounsfield Unit (HU) values were adapted to yield an increased agreement to the reference CT in terms of proton range. Internal air cavities were copied from the CT to minimise inter-scan differences. CT- and MRCAT-based dose calculations for opposing beam IMPT plans were compared by gamma analysis and evaluation of clinically relevant target and organ at risk dose volume histogram (DVH) parameters. The proton range in beam's eye view (BEV) was compared using single field uniform dose (SFUD) plans. On average, a [Formula: see text] mm) gamma pass rate of 98.4% was obtained using a [Formula: see text] dose threshold after adaptation of the pseudo-HU values. Mean differences between CT- and MRCAT-based dose in the DVH parameters were below 1 Gy ([Formula: see text]). The median proton range difference was [Formula: see text] mm, with on average 96% of all BEV dose profiles showing a range agreement better than 3 mm. Results suggest that accurate MR-based proton dose calculation using an automatic commercial bulk-assignment pCT generation method, originally designed for photon radiotherapy, is feasible following adaptation of the assigned pseudo-HU values.
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Affiliation(s)
- Matteo Maspero
- Center for Image Sciences, Universitair Medisch Centrum Utrecht, Utrecht, Netherlands
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31
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Shao W, Tang X, Bai Y, Geng C, Shu D, Gong C, Chen D. Modulation of lateral positions of Bragg peaks via magnetic fields inside cancer patients: Toward magnetic field modulated proton therapy. Med Phys 2017; 44:5325-5338. [DOI: 10.1002/mp.12468] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Revised: 06/29/2017] [Accepted: 07/02/2017] [Indexed: 11/10/2022] Open
Affiliation(s)
- Wencheng Shao
- Department of Nuclear Science and Engineering; Nanjing University of Aeronautics and Astronautics; Nanjing 210016 China
- Department of Radiation Physics; Harbin Medical University Cancer Hospital; Harbin 150081 China
| | - Xiaobin Tang
- Department of Nuclear Science and Engineering; Nanjing University of Aeronautics and Astronautics; Nanjing 210016 China
- Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions; Nanjing 210016 China
| | - Yanling Bai
- Department of Radiation Physics; Harbin Medical University Cancer Hospital; Harbin 150081 China
| | - Changran Geng
- Department of Nuclear Science and Engineering; Nanjing University of Aeronautics and Astronautics; Nanjing 210016 China
| | - Diyun Shu
- Department of Nuclear Science and Engineering; Nanjing University of Aeronautics and Astronautics; Nanjing 210016 China
| | - Chunhui Gong
- Department of Nuclear Science and Engineering; Nanjing University of Aeronautics and Astronautics; Nanjing 210016 China
| | - Da Chen
- Department of Nuclear Science and Engineering; Nanjing University of Aeronautics and Astronautics; Nanjing 210016 China
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Oborn BM, Dowdell S, Metcalfe PE, Crozier S, Mohan R, Keall PJ. Future of medical physics: Real-time MRI-guided proton therapy. Med Phys 2017; 44:e77-e90. [PMID: 28547820 DOI: 10.1002/mp.12371] [Citation(s) in RCA: 90] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2016] [Revised: 03/12/2017] [Accepted: 05/15/2017] [Indexed: 12/20/2022] Open
Abstract
With the recent clinical implementation of real-time MRI-guided x-ray beam therapy (MRXT), attention is turning to the concept of combining real-time MRI guidance with proton beam therapy; MRI-guided proton beam therapy (MRPT). MRI guidance for proton beam therapy is expected to offer a compelling improvement to the current treatment workflow which is warranted arguably more than for x-ray beam therapy. This argument is born out of the fact that proton therapy toxicity outcomes are similar to that of the most advanced IMRT treatments, despite being a fundamentally superior particle for cancer treatment. In this Future of Medical Physics article, we describe the various software and hardware aspects of potential MRPT systems and the corresponding treatment workflow. Significant software developments, particularly focused around adaptive MRI-based planning will be required. The magnetic interaction between the MRI and the proton beamline components will be a key area of focus. For example, the modeling and potential redesign of a magnetically compatible gantry to allow for beam delivery from multiple angles towards a patient located within the bore of an MRI scanner. Further to this, the accuracy of pencil beam scanning and beam monitoring in the presence of an MRI fringe field will require modeling, testing, and potential further development to ensure that the highly targeted radiotherapy is maintained. Looking forward we envisage a clear and accelerated path for hardware development, leveraging from lessons learnt from MRXT development. Within few years, simple prototype systems will likely exist, and in a decade, we could envisage coupled systems with integrated gantries. Such milestones will be key in the development of a more efficient, more accurate, and more successful form of proton beam therapy for many common cancer sites.
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Affiliation(s)
- Bradley M Oborn
- Illawarra Cancer Care Centre (ICCC), Wollongong, NSW, 2500, Australia.,Centre for Medical Radiation Physics (CMRP), University of Wollongong, Wollongong, NSW, 2500, Australia
| | | | - Peter E Metcalfe
- Centre for Medical Radiation Physics (CMRP), University of Wollongong, Wollongong, NSW, 2500, Australia.,Ingham Institute for Applied Medical Research, Liverpool, NSW, 2170, Australia
| | - Stuart Crozier
- School of Information Technology and Electric Engineering, University of Queensland, QLD, 4072, Australia
| | - Radhe Mohan
- Department of Radiation Oncology, MD Anderson, Houston, TX, 77030, USA
| | - Paul J Keall
- Ingham Institute for Applied Medical Research, Liverpool, NSW, 2170, Australia.,Sydney Medical School, University of Sydney, NSW, 2006, Australia
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Pollard JM, Wen Z, Sadagopan R, Wang J, Ibbott GS. The future of image-guided radiotherapy will be MR guided. Br J Radiol 2017; 90:20160667. [PMID: 28256898 DOI: 10.1259/bjr.20160667] [Citation(s) in RCA: 135] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Advances in image-guided radiotherapy (RT) have allowed for dose escalation and more precise radiation treatment delivery. Each decade brings new imaging technologies to help improve RT patient setup. Currently, the most frequently used method of three-dimensional pre-treatment image verification is performed with cone beam CT. However, more recent developments have provided RT with the ability to have on-board MRI coupled to the teleradiotherapy unit. This latest tool for treating cancer is known as MR-guided RT. Several varieties of these units have been designed and installed in centres across the globe. Their prevalence, history, advantages and disadvantages are discussed in this review article. In preparation for the next generation of image-guided RT, this review also covers where MR-guided RT might be heading in the near future.
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Affiliation(s)
| | - Zhifei Wen
- UT MD Anderson Cancer Center, Houston, TX, USA
| | | | - Jihong Wang
- UT MD Anderson Cancer Center, Houston, TX, USA
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Koivula L, Wee L, Korhonen J. Feasibility of MRI-only treatment planning for proton therapy in brain and prostate cancers: Dose calculation accuracy in substitute CT images. Med Phys 2017; 43:4634. [PMID: 27487880 DOI: 10.1118/1.4958677] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
PURPOSE Magnetic resonance imaging (MRI) is increasingly used for radiotherapy target delineation, image guidance, and treatment response monitoring. Recent studies have shown that an entire external x-ray radiotherapy treatment planning (RTP) workflow for brain tumor or prostate cancer patients based only on MRI reference images is feasible. This study aims to show that a MRI-only based RTP workflow is also feasible for proton beam therapy plans generated in MRI-based substitute computed tomography (sCT) images of the head and the pelvis. METHODS The sCTs were constructed for ten prostate cancer and ten brain tumor patients primarily by transforming the intensity values of in-phase MR images to Hounsfield units (HUs) with a dual model HU conversion technique to enable heterogeneous tissue representation. HU conversion models for the pelvis were adopted from previous studies, further extended in this study also for head MRI by generating anatomical site-specific conversion models (a new training data set of ten other brain patients). This study also evaluated two other types of simplified sCT: dual bulk density (for bone and water) and homogeneous (water only). For every clinical case, intensity modulated proton therapy (IMPT) plans robustly optimized in standard planning CTs were calculated in sCT for evaluation, and vice versa. Overall dose agreement was evaluated using dose-volume histogram parameters and 3D gamma criteria. RESULTS In heterogeneous sCTs, the mean absolute errors in HUs were 34 (soft tissues: 13, bones: 92) and 42 (soft tissues: 9, bones: 97) in the head and in the pelvis, respectively. The maximum absolute dose differences relative to CT in the brain tumor clinical target volume (CTV) were 1.4% for heterogeneous sCT, 1.8% for dual bulk sCT, and 8.9% for homogenous sCT. The corresponding maximum differences in the prostate CTV were 0.6%, 1.2%, and 3.6%, respectively. The percentages of dose points in the head and pelvis passing 1% and 1 mm gamma index criteria were over 91%, 85%, and 38% with heterogeneous, dual bulk, and homogeneous sCTs, respectively. There were no significant changes to gamma index pass rates for IMPT plans first optimized in CT and then calculated in heterogeneous sCT versus IMPT plans first optimized in heterogeneous sCT and then calculated on standard CT. CONCLUSIONS This study demonstrates that proton therapy dose calculations on heterogeneous sCTs are in good agreement with plans generated with standard planning CT. An MRI-only based RTP workflow is feasible in IMPT for brain tumors and prostate cancers.
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Affiliation(s)
- Lauri Koivula
- Department of Radiation Oncology, Comprehensive Cancer Center, Helsinki University Central Hospital, P.O. Box 180, Helsinki 00029 HUS, Finland and Department of Medical Physics, Oncology Services, Vejle Hospital, Kabbeltoft 25, Vejle DK-7100, Denmark
| | - Leonard Wee
- Department of Medical Physics, Oncology Services, Vejle Hospital, Kabbeltoft 25, Vejle DK-7100, Denmark and Danish Colorectal Cancer Centre South, Vejle Hospital, Kabbeltoft 25, Vejle DK-7100, Denmark
| | - Juha Korhonen
- Department of Radiation Oncology, Comprehensive Cancer Center, Helsinki University Central Hospital, P.O. Box 180, Helsinki 00029 HUS, Finland; Danish Colorectal Cancer Centre South, Vejle Hospital, Kabbeltoft 25, Vejle DK-7100, Denmark; and Department of Radiology, Helsinki University Central Hospital, P.O. Box 180, Helsinki 00029 HUS, Finland
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Fuchs H, Moser P, Gröschl M, Georg D. Magnetic field effects on particle beams and their implications for dose calculation in MR-guided particle therapy. Med Phys 2017; 44:1149-1156. [DOI: 10.1002/mp.12105] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Revised: 01/05/2017] [Accepted: 01/06/2017] [Indexed: 11/05/2022] Open
Affiliation(s)
- Hermann Fuchs
- Department of Radiation Oncology; Medical University of Vienna/AKH; Vienna Austria
- Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology; Medical University of Vienna; Vienna Austria
| | - Philipp Moser
- Department of Radiation Oncology; Medical University of Vienna/AKH; Vienna Austria
- Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology; Medical University of Vienna; Vienna Austria
- Institute of Applied Physics; Vienna University of Technology; Vienna Austria
| | - Martin Gröschl
- Institute of Applied Physics; Vienna University of Technology; Vienna Austria
| | - Dietmar Georg
- Department of Radiation Oncology; Medical University of Vienna/AKH; Vienna Austria
- Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology; Medical University of Vienna; Vienna Austria
- Comprehensive Cancer Center; Medical University of Vienna/AKH; Vienna Austria
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Schellhammer SM, Hoffmann AL. Prediction and compensation of magnetic beam deflection in MR-integrated proton therapy: a method optimized regarding accuracy, versatility and speed. Phys Med Biol 2017; 62:1548-1564. [DOI: 10.1088/1361-6560/62/4/1548] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Lagendijk JJW, van Vulpen M, Raaymakers BW. The development of the MRI linac system for online MRI-guided radiotherapy: a clinical update. J Intern Med 2016; 280:203-8. [PMID: 27197553 DOI: 10.1111/joim.12516] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- J J W Lagendijk
- Department of Radiotherapy, Centre for Image Sciences, UMC Utrecht, Utrecht, the Netherlands
| | - M van Vulpen
- Department of Radiotherapy, Centre for Image Sciences, UMC Utrecht, Utrecht, the Netherlands
| | - B W Raaymakers
- Department of Radiotherapy, Centre for Image Sciences, UMC Utrecht, Utrecht, the Netherlands
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Required transition from research to clinical application: Report on the 4D treatment planning workshops 2014 and 2015. Phys Med 2016; 32:874-82. [DOI: 10.1016/j.ejmp.2016.05.064] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Revised: 05/28/2016] [Accepted: 05/31/2016] [Indexed: 12/25/2022] Open
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Combs SE, Nüsslin F, Wilkens JJ. Individualized radiotherapy by combining high-end irradiation and magnetic resonance imaging. Strahlenther Onkol 2016; 192:209-15. [PMID: 26852244 DOI: 10.1007/s00066-016-0944-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Accepted: 01/14/2016] [Indexed: 01/22/2023]
Abstract
Image-guided radiotherapy (IGRT) has been integrated into daily clinical routine and can today be considered the standard especially with high-dose radiotherapy. Currently imaging is based on MV- or kV-CT, which has clear limitations especially in soft-tissue contrast. Thus, combination of magnetic resonance (MR) imaging and high-end radiotherapy opens a new horizon. The intricate technical properties of MR imagers pose a challenge to technology when combined with radiation technology. Several solutions that are almost ready for routine clinical application have been developed. The clinical questions include dose-escalation strategies, monitoring of changes during treatment as well as imaging without additional radiation exposure during treatment.
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Affiliation(s)
- Stephanie E Combs
- Department of Radiation Oncology, Klinikum rechts der Isar, Technische Universität München, Ismaninger Straße 22, 81675, München, Germany. .,Institute of Innovative Radiotherapy (iRT), Department of Radiation Sciences (DRS), Helmholtz Zentrum München, Ingolstädter Landstraße 1, 85764, Neuherberg, Germany.
| | - Fridtjof Nüsslin
- Department of Radiation Oncology, Klinikum rechts der Isar, Technische Universität München, Ismaninger Straße 22, 81675, München, Germany
| | - Jan J Wilkens
- Department of Radiation Oncology, Klinikum rechts der Isar, Technische Universität München, Ismaninger Straße 22, 81675, München, Germany.,Institute of Innovative Radiotherapy (iRT), Department of Radiation Sciences (DRS), Helmholtz Zentrum München, Ingolstädter Landstraße 1, 85764, Neuherberg, Germany
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