MR guidance in radiotherapy

Lagendijk, J J W; Raaymakers, B W; Berg, Cornelis A.T. van den; Moerland, Marinus A.; Philippens, M.E.P.; Vulpen, Marco van

doi:10.1088/0031-9155/59/21/r349

Cited by 187 publications

(178 citation statements)

References 124 publications

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“…Moreover, MRI can provide real-time feed-back, providing input for intra-treatment adaptations. This versatility of MRI opens many options for improving radiotherapy treatments (Lagendijk et al 2008(Lagendijk et al , 2014. Now the concept of MRI-Linac has successfully been proven in the first clinical setting and reveals an outstanding level of dosimetric and geometric accuracy of the radiation beam we will work towards real-time adaptive MRI guided radiotherapy using the MRI-Linac, for instance following the approach of Kontaxis et al (2017).…”

Section: Discussionmentioning

confidence: 99%

“…Image guided radiotherapy (IGRT) (Verellen et al 2007(Verellen et al , 2008) is the key to optimize this process as it allows the localization of the tumour and organs at risk (OAR) while the patient is on the treatment table. Of all available imaging modalities for IGRT, MRI is the most versatile and suitable candidate as it provides soft-tissue contrast to enable direct tumour visualization as well as OAR localization (Lagendijk et al 2014). Moreover, it provides real-time imaging to characterize and eventually track anatomical motion (Stemkens et al 2016, Dietz et al 2017 for MRI guided radiotherapy and for dose reconstruction (Glitzner et al 2015) and ultimately real-time plan adaptation (Kontaxis et al 2017).…”

Section: Introductionmentioning

confidence: 99%

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First patients treated with a 1.5 T MRI-Linac: clinical proof of concept of a high-precision, high-field MRI guided radiotherapy treatment

et al. 2017

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LETTER • OPEN ACCESSFirst patients treated with a 1.5 T MRI-Linac: clinical proof of concept of a high-precision, highfield MRI guided radiotherapy treatment AbstractThe integration of 1.5 T MRI functionality with a radiotherapy linear accelerator (linac) has been pursued since 1999 by the UMC Utrecht in close collaboration with Elekta and Philips. The idea behind this integrated device is to offer unrivalled, online and real-time, soft-tissue visualization of the tumour and the surroundings for more precise radiation delivery. The proof of concept of this device was given in 2009 by demonstrating simultaneous irradiation and MR imaging on phantoms, since then the device has been further developed and commercialized by Elekta. The aim of this work is to demonstrate the clinical feasibility of online, high-precision, high-field MRI guidance of radiotherapy using the first clinical prototype MRI-Linac.Four patients with lumbar spine bone metastases were treated with a 3 or 5 beam step-and-shoot IMRT plan. The IMRT plan was created while Letter Institute of Physics and Engineering in MedicineOriginal content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. 3 Author to whom any correspondence should be addressed. the patient was on the treatment table and based on the online 1.5 T MR images; pre-treatment CT was deformably registered to the online MRI to obtain Hounsfield values. Bone metastases were chosen as the first site as these tumors can be clearly visualized on MRI and the surrounding spine bone can be detected on the integrated portal imager. This way the portal images served as an independent verification of the MRI based guidance to quantify the geometric precision of radiation delivery. Dosimetric accuracy was assessed post-treatment from phantom measurements with an ionization chamber and film. Absolute doses were found to be highly accurate, with deviations ranging from 0.0% to 1.7% in the isocenter. The geometrical, MRI based targeting as confirmed using portal images was better than 0.5 mm, ranging from 0.2 mm to 0.4 mm.In conclusion, high precision, high-field, 1.5 T MRI guided radiotherapy is clinically feasible.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

First patients treated with a 1.5 T MRI-Linac: clinical proof of concept of a high-precision, high-field MRI guided radiotherapy treatment

et al. 2017

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“…An exciting development in radiation oncology that shows promise for HPBI is the emergence of MRI‐guided external beam solutions 9. Several ambitious efforts are in progress to integrate MRI into a real‐time or near‐real‐time solution for tumor targeting during or immediately prior to radiation delivery.…”

Section: Introductionmentioning

confidence: 99%

“…Finally, MRI‐Linac solutions are attractive for HPBI due to the ability for these advanced platforms to cut down on internal motion margins using MLC tracking or exception gating using guidance from real‐time MRI images or navigator signals. The MRI‐Linac has been suggested by many to be ideal for image‐guided ablative radiation therapy, a treatment paradigm that is expected to become increasingly prevalent in radiation oncology 9, 13, 16. For low‐risk breast cancer patients, the aforementioned technological advantages given by an MRI‐Linac may pave the way for enabling high precision ablative techniques to be employed for intact breast tumors.…”

Section: Introductionmentioning

confidence: 99%

Magnetic field dose effects on different radiation beam geometries for hypofractionated partial breast irradiation

Kim

Lim‐Reinders

McCann

et al. 2017

J Applied Clin Med Phys

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PurposeHypofractionated partial breast irradiation (HPBI) involves treatment to the breast tumor using high doses per fraction. Recent advances in MRI‐Linac solutions have potential in being applied to HPBI due to gains in the soft tissue contrast of MRI; however, there are potentially deleterious effects of the magnetic field on the dose distribution. The purpose of this work is to determine the effects of the magnetic field on the dose distribution for HPBI tumors using a tangential beam arrangement (TAN), 5‐beam intensity‐modulated radiation therapy (IMRT), and volumetric modulated arc therapy (VMAT).MethodsFive patients who have received HPBI were selected with two patients having bilateral disease resulting in a total of two tumors in this study. Six planning configurations were created using a treatment planning system capable of modeling magnetic field dose effects: TAN, IMRT and VMAT beam geometries, each of these optimized with and without a transverse magnetic field of 1.5 T.ResultsThe heart and lung doses were not statistically significant when comparing plan configurations. The magnetic field had a demonstrated effect on skin dose: for VMAT plans, the skin (defined to a depth of 3 mm) D1cc was elevated by +11% and the V30 by +146%; for IMRT plans, the skin D1cc was increased by +18% and the V30 by +149%. Increasing the number of beam angles (e.g., going from IMRT to VMAT) with the magnetic field on reduced the skin dose.ConclusionThe impact of a magnetic field on HPBI dose distributions was analyzed. The heart and lung doses had clinically negligible effects caused by the magnetic field. The magnetic field increases the skin dose; however, this can be mitigated by increasing the number of beam angles.

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“…The primary advantages of MR‐IGRT over existing image‐guided radiotherapy systems based on planar X‐ray imaging or cone‐beam computed tomography (CBCT) are superior soft‐tissue contrast, no radiation dose, capability of tracking tissue during radiation delivery, and multiplanar imaging. Several MR‐IGRT systems that are being investigated include MR/linac systems, 2 , 3 , 4 , 5 a MR/Co‐60 system, 6 , 7 and systems with either mobile patient or magnet (1) . Among those, the MR/Co‐60 system from the ViewRay Inc. is commercially available and already started treating patients clinically (8) …”

Section: Introductionmentioning

confidence: 99%

A comparative study of automatic image segmentation algorithms for target tracking in MR‐IGRT

Feng

Kawrakow

Olsen

et al. 2016

J Applied Clin Med Phys

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On‐board magnetic resonance (MR) image guidance during radiation therapy offers the potential for more accurate treatment delivery. To utilize the real‐time image information, a crucial prerequisite is the ability to successfully segment and track regions of interest (ROI). The purpose of this work is to evaluate the performance of different segmentation algorithms using motion images (4 frames per second) acquired using a MR image‐guided radiotherapy (MR‐IGRT) system. Manual contours of the kidney, bladder, duodenum, and a liver tumor by an experienced radiation oncologist were used as the ground truth for performance evaluation. Besides the manual segmentation, images were automatically segmented using thresholding, fuzzy k‐means (FKM), k‐harmonic means (KHM), and reaction‐diffusion level set evolution (RD‐LSE) algorithms, as well as the tissue tracking algorithm provided by the ViewRay treatment planning and delivery system (VR‐TPDS). The performance of the five algorithms was evaluated quantitatively by comparing with the manual segmentation using the Dice coefficient and target registration error (TRE) measured as the distance between the centroid of the manual ROI and the centroid of the automatically segmented ROI. All methods were able to successfully segment the bladder and the kidney, but only FKM, KHM, and VR‐TPDS were able to segment the liver tumor and the duodenum. The performance of the thresholding, FKM, KHM, and RD‐LSE algorithms degraded as the local image contrast decreased, whereas the performance of the VP‐TPDS method was nearly independent of local image contrast due to the reference registration algorithm. For segmenting high‐contrast images (i.e., kidney), the thresholding method provided the best speed (<1 ms) with a satisfying accuracy (Dice=0.95). When the image contrast was low, the VR‐TPDS method had the best automatic contour. Results suggest an image quality determination procedure before segmentation and a combination of different methods for optimal segmentation with the on‐board MR‐IGRT system.PACS number(s): 87.57.nm, 87.57.N‐, 87.61.Tg

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MR guidance in radiotherapy

Cited by 187 publications

References 124 publications

First patients treated with a 1.5 T MRI-Linac: clinical proof of concept of a high-precision, high-field MRI guided radiotherapy treatment

First patients treated with a 1.5 T MRI-Linac: clinical proof of concept of a high-precision, high-field MRI guided radiotherapy treatment

Magnetic field dose effects on different radiation beam geometries for hypofractionated partial breast irradiation

A comparative study of automatic image segmentation algorithms for target tracking in MR‐IGRT

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