Clinical assessment of geometric distortion for a 0.35T MR‐guided radiotherapy system

Neylon, John; Cook, Kiri; Yang, Yingli; Du, D.; Sheng, Ke; Chin, Robert; Kishan, Amar U.; Lamb, James; Low, Daniel A.; Cao, Minsong

doi:10.1002/acm2.13340

Cited by 4 publications

(3 citation statements)

References 25 publications

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“…However, significant image artifacts were observed during gantry rotation using bSSFP MRI (Crijns andRaaymakers 2014, Gach et al 2019). Off-resonances from magnetic field inhomogeneities, central frequency offsets, gradient nonlinearities, and B 0 eddy currents cause geometric distortion, imaging isocenter shift, signal heterogeneity, and image blurring (Dharmakumar et al 2007, Torfeh et al 2016, Ginn et al 2017, Neylon et al 2021. Geometric distortion and isocenter variation in 3D bSSFP imaging for radiotherapy planning and daily setup and their several correction parameters have been investigated previously (Torfeh et al 2016, Shan et al 2020, Marasini et al 2022, Lotey et al 2023.…”

Section: Introductionmentioning

confidence: 99%

Characterization of real-time cine MR imaging distortion on 0.35 T MRgRT with concentric cine imaging QA phantom

Marasini,

Cole,

Curcuru

et al. 2024

Phys. Med. Biol.

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Objective: Real-time MRgRT uses 2D-cine imaging for target tracking and motion evaluation. Rotation of gantry induced B0 off-resonance, resulting in image artifacts and imaging isocenter-shift precluding MR-guided arc therapy. This work aimed to examine the spatial accuracy including geometric distortion and isocenter shift in real-time during gantry rotation on a 0.35T MR-Linac using the concentric Cine imaging QA phantom and its associated image analysis software. Approach: The Cine imaging QA phantom consists of two concentric shells of low-T1 mineral oil and a central alignment structure. The phantom was scanned on three different MRI systems; 0.55T Siemens Free.Max, 1.5T Philips Ingenia, and 0.35T ViewRay MRIdian MR-Linac using 2D balanced steady-state free precession (bSSFP) imaging sequence. In addition, bSSFP cine MRI with the banding artifact correction was tested on 0.35T ViewRay MR-Linac. Images from the MR-Linac were acquired with the Linac gantry stationary and rotating from gantry 300° 0° and vice versa. Three orthogonal image planes were scanned excluding the 1.5T Philips Ingenia, where only the axial plane was scanned. The image analysis software calculated the distortion values as well as the isocenter position for each cine frame.Main results: The geometric distortion on MRIs and MR-Linac at gantry stationary are within 1 mm while the substantial geometric distortion of 2 mm and 2.9 mm were observed on 0.35 T MR-Linac while rotating the gantry clockwise (300 0°) and counterclockwise 0 300° respectively, The average imaging isocenter shift was 0.1 mm for both MRIs and the static gantry and isocenter shift of ≤1.5 mm observed during the gantry rotation. The imaging isocenter shift decreased by 1±0.2 mm clockwise and counterclockwise with B0 compensation.Significance: The concentric Cine imaging QA phantom and its associated software effectively demonstrate the image distortion on real-time cine imaging on regular MRIs and 0.35T MR-Linac. 

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Section: Introductionmentioning

confidence: 99%

Characterization of real-time cine MR imaging distortion on 0.35 T MRgRT with concentric cine imaging QA phantom

Marasini,

Cole,

Curcuru

et al. 2024

Phys. Med. Biol.

View full text Add to dashboard Cite

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“…Machine‐specific distortions originate from the field inhomogeneity and gradient non‐linearity. In state‐of‐the‐art MRI scanners, those distortions are negligible, especially for brain imaging with small volume close to the MRI scanner isocenter 5,6 . On the other hand, patient‐specific geometrical distortions (PSD) are due to the susceptibility changes at the air‐tissue boundaries and water/fat frequency shift resulting from the chemical shift artifact.…”

Section: Introductionmentioning

confidence: 99%

“…In state‐of‐the‐art MRI scanners, those distortions are negligible, especially for brain imaging with small volume close to the MRI scanner isocenter. 5 , 6 On the other hand, patient‐specific geometrical distortions (PSD) are due to the susceptibility changes at the air‐tissue boundaries and water/fat frequency shift resulting from the chemical shift artifact. The magnetic susceptibility changes are not negligible at the air‐tissue interfaces, even when MRI sequences with a modified high bandwidth (BW) are utilized.…”

Section: Introductionmentioning

confidence: 99%

Patient‐specific geometrical distortion corrections of MRI images improve dosimetric planning accuracy of vestibular schwannoma treated with gamma knife stereotactic radiosurgery

Safari,

Fatemi,

Afkham

et al. 2023

J Applied Clin Med Phys

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PurposeTo investigate the impact of MRI patient‐specific geometrical distortion (PSD) on the quality of Gamma Knife stereotactic radiosurgery (GK‐SRS) plans of the vestibular schwannoma (VS) tumors.Methods and materialsThree open access datasets including the MPI‐Leipzig Mind‐Brain‐Body (318 patients), the slow event‐related fMRI designs dataset (62 patients), and the VS dataset (242 patients) were used. We used first two datasets to train a 3D convolution network to predict the distortion map of third dataset that were then used to calculate and correct the PSD. GK‐SRS plans of VS dataset were used to evaluate dose distribution of PSD‐corrected MRI images. GK‐SRS prescription dose of VS cases was 12 Gy. Geometric and dosimetric discrepancies were assessed between the dose distributions and contours before and after the PSD corrections. Geometry indices were center of the contours, Dice coefficient (DC), Hausdorff distance (HD), and dosimetric indices were , , , and doses, target coverage (TC), Paddick's conformity index (PCI), Paddick's gradient index (GI), and homogeneity index (HI).ResultsGeometric distortions of about 1.2 mm were observed at the air‐tissue interfaces at the air canal and nasal cavity borders. Average center of the targets was significantly distorted along the frequency encoding direction after the PSD‐correction. Average DC and HD metrics were 0.90 and 2.13 mm. Average , and in Gy significantly increased after PSD correction from 16.85 to 17.25, 12.30 to 12.77, and from 8.98 to 9.92. did not significantly change after the correction. Average TC and PCI significantly increased from 0.97 to 0.98, and 0.94 to 0.96. Average GI decreased significantly from 2.24 to 2.15 after PSD correction. However, HI did not significantly change after the correction.ConclusionThe proposed method could predict and correct the PSD that indicates the importance of PSD correction before GK‐SRS plans of the VS patients.

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Characterization of spatial integrity with active and passive implants in a low-field magnetic resonance linear accelerator scanner

Pouymayou,

Perez-Haas,

Allemann

et al. 2024

Physics and Imaging in Radiation Oncology

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Clinical assessment of geometric distortion for a 0.35T MR‐guided radiotherapy system

Abstract: This is an open access article under the terms of the Creat ive Commo ns Attri bution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Cited by 4 publications

References 25 publications

Characterization of real-time cine MR imaging distortion on 0.35 T MRgRT with concentric cine imaging QA phantom

Characterization of real-time cine MR imaging distortion on 0.35 T MRgRT with concentric cine imaging QA phantom

Patient‐specific geometrical distortion corrections of MRI images improve dosimetric planning accuracy of vestibular schwannoma treated with gamma knife stereotactic radiosurgery

Characterization of spatial integrity with active and passive implants in a low-field magnetic resonance linear accelerator scanner

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