Proton beam deflection in MRI fields: Implications for MRI‐guided proton therapy

Oborn, Bradley M; Dowdell, S; Metcalfe, Peter E; Crozier, Stuart; Mohan, Radhe; Keall, Paul J.

doi:10.1118/1.4916661

Cited by 71 publications

(107 citation statements)

References 58 publications

(47 reference statements)

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“…We provide here an example of this process for the magnetic field of the Agilent 1 T splitbore design for the Sydney MRXT prototype. 22 Figure 2 demonstrates this concept for a simple case in the perpendicular orientation (see Section 4.A) using simple Monte Carlo simulations. In Fig.…”

Section: B1 Pencil Beam Scanning and Fringe Field Correction: An mentioning

confidence: 99%

“…It has been shown recently, however, that the fringe field of an MRI scanner has a complex and significant impact on how a proton beam transports towards the MRI isocenter. 22 A important implication of this work is that the most reliable method for proton beam delivery in real-time MR-guided proton therapy will be the pencil beam scanning method. Passively scattered broad beams, which also contain a broad energy range, will deflect and distort as they travel through the 3D spatially variant fringe field and deposit their Bragg peaks at locations different from the nonmagnetic field case.…”

Section: C Existing Literature In Mrptmentioning

confidence: 99%

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Future of medical physics: Real‐time MRI‐guided proton therapy

et al. 2017

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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; MRIguided 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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Section: B1 Pencil Beam Scanning and Fringe Field Correction: An mentioning

confidence: 99%

Section: C Existing Literature In Mrptmentioning

confidence: 99%

Future of medical physics: Real‐time MRI‐guided proton therapy

et al. 2017

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“…Most of the past work focused on prediction of proton beam deflection in magnetic fields, implications on dose distribution, and compensation strategies, with studies specific to both passively scattered and actively scanned clinical beams. Monte Carlo simulations suggested that the pencil beam scanning method will be the only choice for delivering a proton beam to the treatment zone inside a hypothetical split‐bore MRI‐guided proton therapy system due to the complexity of magnetic deflection and distortion . A recent review paper predicted the accelerated development of hardware and simple prototype systems within a few years and coupled systems integrated with gantries in a decade.…”

Section: Beyond Radiological Image Guidancementioning

confidence: 99%

Current state and future applications of radiological image guidance for particle therapy

Landry

Hua

2018

Medical Physics

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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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“…Pencil beam scanning, which is becoming more widely available, may provide superior conformality in a number of settings, for example [16], by reducing the proximal dose to the femoral heads and tissue lateral to the target by allowing for intensity modulated PT [17, 18]. Future improvements to proton beam delivery is anticipated with the implementation and availability of magnetic resonance imaging–guided approaches that incorporate magnetic modeling and Monte Carlo simulation [19]. …”

Section: Discussionmentioning

confidence: 99%

Proton Therapy for Vaginal Reirradiation

Kirk

Lin

2016

International Journal of Particle Therapy

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Primary or recurrent gynecologic cancers in operable patients with a history of prior pelvic radiation are typically treated with surgery based on the risk of late toxicities historically associated with reirradiation. A number of studies have demonstrated that, compared with conventional radiation therapy (RT) using photons, proton therapy (PT) offers dosimetric advantages for patients with gynecologic cancers by reducing radiation dose to healthy tissues. Thereby, we expect that, in appropriately selected cases, PT may reduce long-term treatment-related morbidities without compromising treatment efficacy. Herein, we describe the treatment planning, technique, and long-term follow-up of a patient who was treated with PT for a primary vaginal carcinoma nearly 30 years after a prior course of pelvic RT. Using this case, we illustrate the utility and advantages of PT in the treatment of cancers that occur at less favorable sites, adjacent to normal structures with low radiation tolerance, or in paients with a history of prior irradiation. Additionally, we provide a brief discussion and review of literature of prior case series of pelvic reirradiation, illustrating the value of identifying treatment approaches that can reduce treatment-related morbidities, particularly late treatment toxicities.

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Proton beam deflection in MRI fields: Implications for MRI‐guided proton therapy

Cited by 71 publications

References 58 publications

Future of medical physics: Real‐time MRI‐guided proton therapy

Future of medical physics: Real‐time MRI‐guided proton therapy

Current state and future applications of radiological image guidance for particle therapy

Proton Therapy for Vaginal Reirradiation

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