Evaluation of a magnetic resonance guided linear accelerator for stereotactic radiosurgery treatment

Wen, Ning; Kim, Joshua; Doemer, Anthony; Glide-Hurst, Carri K; Chetty, Indrin J.; Liu, Chang; Laugeman, Eric; Xhaferllari, Ilma; Kumarasiri, Akila; Victoria, J.R.; Bellon, M; Kalkanis, Steve; Siddiqui, M. Salim; Movsas, Benjamin

doi:10.1016/j.radonc.2018.04.034

Cited by 49 publications

(64 citation statements)

References 30 publications

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“…In 2014, the first patient was treated with ViewRay’s MRIdian integrated 60 Co 0.35 T magnetic resonance imaging (MRI) guided radiotherapy (MR‐IGRT) system . Since 2017, commercial MRI linear accelerators (MRI‐Linacs) with magnetic fields of 0.35 T (ViewRay MRIdian) and 1.5 T (Elekta Unity) have been treating patients …”

Section: Introductionmentioning

confidence: 99%

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MRI quality control for low‐field MR‐IGRT systems: Lessons learned

Gach

Curcuru

Wittland

et al. 2019

J Applied Clin Med Phys

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Purpose: To present lessons learned from magnetic resonance imaging (MRI) quality control (QC) tests for low-field MRI-guided radiation therapy (MR-IGRT) systems.Methods: MRI QC programs were established for low-field MRI-60 Co and MRI-Linac systems. A retrospective analysis of MRI subsystem performance covered system commissioning, operations, maintenance, and quality control. Performance issues were classified into three groups: (a) Image noise and artifact; (b) Magnetic field homogeneity and linearity; and (c) System reliability and stability.Results: Image noise and artifacts were attributed to room noise sources, unsatisfactory system cabling, and broken RF receiver coils. Gantry angle-dependent magnetic field inhomogeneities were more prominent on the MRI-Linac due to the high volume of steel shielding in the gantry. B 0 inhomogeneities measured in a 24-cm spherical phantom were <5 ppm for both MR-IGRT systems after using MRI gradient offset (MRI-GO) compensation on the MRI-Linac. However, significant signal dephasing occurred on the MRI-Linac while the gantry was rotating. Spatial integrity measurements were sensitive to gradient calibration and vulnerable to shimming.The most common causes of MR-IGRT system interruptions were software disconnects between the MRI and radiation therapy delivery subsystems caused by patient table, gantry, and multi-leaf collimator (MLC) faults. The standard deviation (SD) of the receiver coil signal-to-noise ratio was 1.83 for the MRI-60 Co and 1.53 for the MRI-Linac. The SD of the deviation from the mean for the Larmor frequency was 1.41 ppm for the MRI-60 Co and 1.54 ppm for the MRI-Linac. The SD of the deviation from the mean for the transmitter reference amplitude was 0.90% for the MRI-60 Co and 1.68% for the MRI-Linac. High SDs in image stability data corresponded to reports of spike noise.Conclusions: There are significant technological challenges associated with implementing and maintaining MR-IGRT systems. Most of the performance issues were identified and resolved during commissioning.

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Section: Introductionmentioning

confidence: 99%

“…QC results for MR‐IGRT were reported for the ViewRay 0.35 T MRI‐ 60 Co [Ref. ] and MRI‐Linac, and the 1.5 T Elekta Unity …”

Section: Introductionmentioning

confidence: 99%

MRI quality control for low‐field MR‐IGRT systems: Lessons learned

Gach

Curcuru

Wittland

et al. 2019

J Applied Clin Med Phys

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“…Also, the use of MR‐IGRT can avoid the additional radiation exposure that is inherent to CBCT and therefore, can enable daily monitoring of intra‐fractional motion as well as treatment plan adjustments based on changes in anatomy . Recently, MRI has been coupled with a linear accelerator (MR‐linac) offering possibilities such as treatment of small brain metastases in an MR‐guided stereotactic radiosurgery (MRgSRS) setting . However, as with any MR imaging system, one of the challenges in MR‐IGRT is dealing with distortions that are intrinsic to MRI .…”

Section: Introductionmentioning

confidence: 99%

“…3 Recently, MRI has been coupled with a linear accelerator (MR-linac) offering possibilities such as treatment of small brain metastases in an MR-guided stereotactic radiosurgery (MRgSRS) setting. [4][5][6][7] However, as with any MR imaging system, one of the challenges in MR-IGRT is dealing with distortions that are intrinsic to MRI. 8 Geometric distortions can lead to target localization uncertainties, which can lead to missing or underdosing the target during treatment.…”

Section: Introductionmentioning

confidence: 99%

Large field of view distortion assessment in a low‐field MR‐linac

Nejad-Davarani

Kim

et al. 2019

Medical Physics

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Purpose MR‐guided radiation therapy (RT) offers unparalleled soft tissue contrast for localization and target tracking. However, MRI distortions may be detrimental to high precision RT. This work characterizes the gradient nonlinearity (GNL) and total distortions over the first year of clinical operation of a 0.35T MR‐linac. Methods For GNL characterization, an in‐house large field of view (FOV) phantom (60 × 42.5 × 55 cm3, >6000 spherical landmarks) was configured and scanned at four timepoints with forward/reverse read polarities (Gradient Echo sequence, FA/TR/TE = 28°/30 ms/6 ms). GNL was measured in Anterior‐Posterior (AP), Left‐Right (LR), and Superior‐Inferior (SI) frequency‐encoding directions based on deviation of the auto‐segmented landmark centroids between rigidly registered MR and CT images and assessed based on radial distance from magnet isocenter. Total distortion was assessed using a 30 × 30 cm2 grid phantom oriented along the cardinal axes over >1 year of operation. Results The scanner's spatial integrity within the first ~10 months was stable (maximum total distortion variation = 10/6/8%, maximum distortion = 1.41/0.99/1.56 mm in Axial/Coronal/Sagittal planes, respectively). GNL distortions measured during this time period <10 cm from isocenter were (−0.74, 0.45), (−0.67, 0.53), and (−0.86, 0.70) mm in AP/LR/SI directions. In the 10‐20 cm range, <1.5% of the distortions exceeded 2 mm in the AP and LR axes while <4% of the distortions exceeded 2 mm for SI. After major repairs and magnet re‐shim, detectable changes were observed in total and GNL distortions (20% reduction in AP and 36% increase in SI direction in the 20–25 cm range). Across all timepoints and axes, 38–53% of landmarks in the 20–25 cm range were displaced by >1 mm. Conclusions GNL distortions were negligible within a 10 cm radius from isocenter. However, in the periphery, non‐negligible distortions of up to ~7 mm were observed, which may necessitate GNL corrections for MR‐IGRT for treatment sites distant from magnet isocenter.

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“…Tabela 1: Profundidades de máxima dose (zmax) para os feixes de fótons e elétrons mostrados nas figuras 2(a) e (b). Atualmente, os aparelhos mais utilizados em tratamentos de radioterapia são os aceleradores lineares, uma vez que possuem uma variedade maior de energia, tanto de feixe de elétrons bem como de feixe de fótons, tornando possível o tratamento em diversas profundidades (MERNA et al, 2016;MATZENAUER et al, 2016;YAHYA et al, 2017;GIGLIOTTI et al, 2018;WEN et al, 2018).…”

Section: Teleterapia (Fótons E Elétrons)unclassified

Dosimetria gel polimérica usando imagem de ressonância magnética para aplicação em radioterapia

Silva¹

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AgradecimentosPrimeiramente, agradeço à Deus por tudo. Chegar até aqui não foi fácil: desde a graduação foram mais de 10 anos. Foram vários os momentos de lutas, mas a persistência e a fé foram maiores. A vontade de vencer e graças a Sua ajuda, essa luta foi vencida.Muito obrigada! À minha orientadora Profa. Dra. Patrícia Nicolucci. Não posso dizer que você foi "só" uma orientadora. Me lembro perfeitamente da nossa primeira conversa e a amizade foi recíproca desde o primeiro momento. Obrigada pelos ensinamentos, pelas discussões pela parceria, por confiar em mim. Foi uma honra ter sido sua aluna desde o mestrado. Agradeço, diariamente, por ter você no meu caminho e quero ter sua amizade para sempre. Você será, para sempre, o meu espelho e o meu exemplo. Muito obrigada por tudo! Aos meus pais e meu irmão que sempre estiveram ao meu lado, nos momentos de alegria e nos nem tão alegres também. Que foram a minha base, o meu alicerce desde sempre. Essa vitória também é de vocês. Ao Prof Dr John C Gore que me aceitou desde o primeiro momento como aluna em Nashville (EUA), para a realização do meu sonhado doutorado sanduíche na Vanderbilt University, Garrido, obrigada por todas as discussões que tivemos ao longo de todo o trabalho. A ajuda de vocês foi fundamental. Aos meus avós que sempre estiveram me apoiando em cada retorno para casa, muito obrigada. Aos dois avôs e a tia que não estão mais presentes fisicamente aqui, tenho certeza que lá de cima estão felizes por mais essa conquista. Vô Ricardo, vô Avelino e tia Tânia, vocês foram exemplos para mim. Essa conquista também é de vocês. Aos meus tios e primos que carinhosamente me recebiam em todas as voltas para casa, muito obrigada. O carinho e o apoio de vocês fazem a diferença na minha vida. vi À Sandra Andrade que tantas vezes foi meu porto seguro quando diariamente conversava comigo. Obrigada pela sua amizade, pelo apoio que mesmo a distância, fez e faz toda diferença na minha vida. Essa vitória também é sua! Aos amigos que o CIDRA me deu ao longo desses anos: Dra Cassiana, Laurinha, Franciely, Eduardo, Gislaine, Cristiano, Thatiane, Mirko, as duas Fernandas, Camila, Vinicius, Miriã, Matheus, Danny. A batalha foi mais leve, graças ao apoio de vocês. Muito obrigada pela amizade de cada um. Vocês são especiais! À Alice Sancinetti e Mariana Carballeda, que graças a tecnologia que nos aproxima sempre, permite que não perdêssemos o contato. Nós podíamos passar tempo sem nos encontrarmos, mas todas as vezes que nos víamos, era como se revivêssemos os bons tempos que nos encontrávamos diariamente. A amizade e o carinho de vocês são coisas raras! Obrigada por tudo, sempre. Ao Setor de Radioterapia do Hospital das Clínicas da Faculdade de Medicina de Ribeirão Preto, em especial ao Físico Leandro Federiche Borges que desde a época do meu mestrado, se prontamente se dispôs a realizar todas as minhas irradiações. Muito obrigada! À Guozhen Luo pelas irradiações na Vanderbilt Clinic e ao Dr. Edvaldo Galhardo pelas irradiações na Medicina de Ribeirão Preto, pela atenção e disponi...

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Evaluation of a magnetic resonance guided linear accelerator for stereotactic radiosurgery treatment

Cited by 49 publications

References 30 publications

MRI quality control for low‐field MR‐IGRT systems: Lessons learned

MRI quality control for low‐field MR‐IGRT systems: Lessons learned

Large field of view distortion assessment in a low‐field MR‐linac

Dosimetria gel polimérica usando imagem de ressonância magnética para aplicação em radioterapia

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