MRI-Linear Accelerator Radiotherapy Systems

Liney, Gary; Whelan, Brendan; Oborn, Bradley M; Bartoň, Michael; Keall, Paul J.

doi:10.1016/j.clon.2018.08.003

Cited by 95 publications

(88 citation statements)

References 30 publications

(32 reference statements)

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“…Typically, an RGD is inserted into a holder made of the ABS resin. The density and thickness of the ABS holder are 1.05 g/cm 3 diameter is 0.18 cm, which is 0.03 cm larger than the RGD diameter of 0.15 cm (Fig. 1); thus, an air-gap was created between the holder and the RGD.…”

Section: B2 Effect Of the Air-gap On The Rgd Relative Responsementioning

confidence: 99%

“…Furthermore, functional information specific to MR images, for example, diffusion-weighted imaging and blood-oxygenlevel-dependent (BOLD) contrast imaging, can be used for radiation therapy, enabling novel approaches that utilize functional changes during irradiation. 3 However, the presence of the magnetic field affects the dosimetry by distortion of the dose distribution, owing to the secondary electrons deflected by the Lorentz force. The effect depends on the magnetic field strength and direction with respect to the irradiation beam.…”

Section: Introductionmentioning

confidence: 99%

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Impact of transverse magnetic fields on dose response of a radiophotoluminescent glass dosimeter in megavoltage photon beams

2020

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Purpose: The purpose of this study was to investigate the impact of transverse magnetic fields on the dose response of a radiophotoluminescent glass dosimeter (RGD) in megavoltage photon beams. Methods: The RGD relative response (i.e., RGD dose per absorbed dose to water at the midpoint of the detector in the absence of the detector) was calculated using Monte Carlo (MC) simulations. Note that the Monte Carlo calculations do not account for changes of the signal production per unit dose to the RGD caused by the magnetic field strength. The relative energy response R Q , the relative magnetic response R B , and the relative overall response R Q,B with the transverse magnetic fields of 0-3 T were analyzed as a function of depth, for a 10 cm 9 10 cm field in a solid water phantom, for 4-18 MV photons. Although magnetic resonance (MR) linacs with flattening filter free beams are commercially available, flattening filter beams were used to investigate the RGD response in this study. R Q is the response in beam quality Q relative to that in the reference beam with quality 6 MV, R B is the response in beam quality Q with the magnetic field relative to that in beam quality Q without the magnetic field, and the R Q,B is the response in beam quality Q with the magnetic field relative to that in the reference beam with quality 6 MV without the magnetic field. Two RGD orientations were considered: RGD long axis is parallel (direction A) and perpendicular (direction B) to the magnetic field. The reference irradiation conditions were at the depth of 10 cm for a 10 cm 9 10 cm field for 6 MV, without the magnetic field. In addition, the influence of a small air-gap between the holder inner wall and the RGD on the dose response in the magnetic field, R gap , was analyzed in detail. R gap is the response in beam quality Q without/with the air-gap. Results: R Q decreased by up to 2.7% as the energy increased in the range of 4-18 MV, except in the buildup region. In direction A, the variation of R B owing to the magnetic field strength was below 1.0%, regardless of the photon energy. In contrast, in direction B, R B decreased with increasing magnetic field strength and decreased up to 4.0% at 3 T for 10 MV. The R gap for 0.03 and 0.05 cm airgap models in direction A decreased up to 2.3% and up to 4.0%, respectively. Conclusions: The variation of R Q,B changed with the direction of the RGD relative to the magnetic field. For dose measurements, RGDs should be positioned with the long axis parallel to the magnetic field, without air-gaps.

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Section: B2 Effect Of the Air-gap On The Rgd Relative Responsementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Impact of transverse magnetic fields on dose response of a radiophotoluminescent glass dosimeter in megavoltage photon beams

2020

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“…Another key feature is the capacity to monitor the response of the tumor to the treatment and to detect changes in tumor characteristics with functional MRI. These techniques are now in development and hold the prospect of further personalizing the treatment to each individual patient (Liney et al, 2018).…”

Section: Outlook For Technology-driven Research On Image Guidancementioning

confidence: 99%

Technology‐driven research for radiotherapy innovation

et al. 2020

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Technology has a pivotal role in the continuous development of radiotherapy. The long road toward modern ‘high‐tech’ radiation oncology has been studded with discoveries and technological innovations that resulted from the interaction of various disciplines. In the last decades, a dramatic technology‐driven revolution has hugely improved the capability of accurately and safely delivering complex‐shaped dose distributions. This has contributed to many clinical improvements, such as the successful management of lung cancer and oligometastatic disease through stereotactic body radiotherapy. Technology‐driven research is an active and lively field with promising potential in several domains, including image guidance, adaptive radiotherapy, integration of artificial intelligence, heavy‐particle therapy, and ‘flash’ ultra‐high dose‐rate radiotherapy. The evolution toward personalized Oncology will deeply influence technology‐driven research, aiming to integrate predictive models and omics analyses into fast and efficient solutions to deliver the best treatment for each single patient. Personalized radiation oncology will need affordable technological solutions for middle‐/low‐income countries, as these are expected to experience the highest increase of cancer incidence and mortality. Moreover, technology solutions for automation of commissioning, quality assurance, safety tests, image segmentation, and plan optimization will be required. Although a large fraction of cancer patients receive radiotherapy, this is certainly not reflected in the worldwide budget for radiotherapy research. Differently from the pharmaceutical companies‐driven research, resources for research in radiotherapy are highly limited to equipment vendors, who can, in turn, initiate a limited number of collaborations with academic research centers. Thus, enhancement of investments in technology‐driven radiotherapy research via public funds, national governments, and the European Union would have a crucial societal impact. It would allow for radiotherapy to further strengthen its role as a highly effective and cost‐efficient cancer treatment modality, and it could facilitate a rapid and equalitarian large‐scale transfer of technology to clinic, with direct impact on patient care.

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“…Integrated magnetic resonance imaging (MRI) and radiotherapy systems are clinically established in image‐guided radiotherapy (IGRT) . Furthermore, there are several systems with unique configurations such as inline orientation with biplanar magnet and inline/perpendicular orientation with open magnet under development . The integrated MRI and radiotherapy systems can provide real‐time tumor tracking, inclusive of changes in tumor position and shape, since MRI produces superior soft tissue contrast of patient anatomy without ionizing radiation.…”

Section: Introductionmentioning

confidence: 99%

“…[1][2][3][4] Furthermore, there are several systems with unique configurations such as inline orientation with biplanar magnet and inline/perpendicular orientation with open magnet under development. [5][6][7][8] The integrated MRI and radiotherapy systems can provide real-time tumor tracking, inclusive of changes in tumor position and shape, 2,9,10 since MRI produces superior soft tissue contrast of patient anatomy without ionizing radiation. MRI-guided radiotherapy (MRgRT) gives excellent local control with little toxicity.…”

Section: Introductionmentioning

confidence: 99%

Technical Note: Real‐time 3D MRI in the presence of motion for MRI‐guided radiotherapy: 3D Dynamic keyhole imaging with super‐resolution

et al. 2019

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Purpose The purpose of this study was to present real‐time three‐dimensional (3D) magnetic resonance imaging (MRI) in the presence of motion for MRI‐guided radiotherapy (MRgRT) using dynamic keyhole imaging for high‐temporal acquisition and super‐resolution generative (SRG) model for high‐spatial reconstruction. Method We propose a unique real‐time 3D MRI technique by combining a data sharing technique (3D dynamic keyhole imaging) with a SRG model using cascaded deep learning technique. 3D dynamic keyhole imaging utilizes the data sharing mechanism by combining keyhole central k‐space data acquired in real‐time with high‐spatial, high‐temporal resolution prior peripheral k‐space data at various motion positions prepared by the SRG model. The efficacy of the 3D dynamic keyhole imaging with super‐resolution (SR_dKeyhole) was compared to the ground‐truth super‐resolution images with the original full k‐space data. It was also compared with the zero‐filling reconstruction (zero‐filling), conventional keyhole reconstruction with low‐spatial high‐temporal prior data (LR_cKeyhole), and conventional keyhole reconstruction with super‐resolution prior data (SR_cKeyhole). Results High‐spatial, high‐temporal resolution 3D MRI datasets (1.5 × 1.5 × 6 mm3) were generated from low‐spatial, high‐temporal resolution 3D MRI datasets (6 × 6 × 6 mm3) using the cascaded deep learning SRG framework (<100 ms/volume). 3D dynamic keyhole imaging with the SRG model provided high‐spatial, high‐temporal resolution images (1.5 × 1.5 × 6 mm3, 455 ms) with the highest similarity to the ground‐truth SR images without any noticeable artifacts. Structural similarity indices (SSIM) of the reconstructed 3D MRI to the original SR 3D MRI were 0.65, 0.66, 0.86, and 0.89 for zero‐filling, LR_cKeyhole, SR_cKeyhole, and SR_dKeyhole, respectively (1 for identical image). In addition, average value of image relative error (IRE) of the reconstructed 3D MRI to the original SR 3D MRI were 0.169, 0.191, 0.079, and 0.067 for zero‐filling, LR_cKeyhole, SR_cKeyhole, and SR_dKeyhole, respectively (0 for identical image). Conclusions We demonstrated that high‐spatial, high‐temporal resolution 3D MRI was feasible by combing 3D dynamic keyhole imaging with a SRG model in terms of image quality and imaging time. The proposed technique can be utilized for real‐time 3D MRgRT.

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MRI-Linear Accelerator Radiotherapy Systems

Cited by 95 publications

References 30 publications

Impact of transverse magnetic fields on dose response of a radiophotoluminescent glass dosimeter in megavoltage photon beams

Impact of transverse magnetic fields on dose response of a radiophotoluminescent glass dosimeter in megavoltage photon beams

Technology‐driven research for radiotherapy innovation

Technical Note: Real‐time 3D MRI in the presence of motion for MRI‐guided radiotherapy: 3D Dynamic keyhole imaging with super‐resolution

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