Simulated field maps for susceptibility artefact correction in interventional MRI

Kochan, Martin; Daga, Pankaj; Burgos, Ninon; White, Mark; Cardoso, M. Jorge; Mancini, Laura; Winston, Gavin P.; McEvoy, Andrew W.; Thornton, John S.; Yousry, Tarek; Duncan, John S.; Stoyanov, Danail; Ourselin, Sébastien

doi:10.1007/s11548-015-1253-7

Cited by 4 publications

(6 citation statements)

References 23 publications

(42 reference statements)

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“…The subtraction images demonstrate the contrast‐enhancing, abnormal tissue nicely, with only minor obscuring artifacts, and it has been proven useful in clinical practice (Fig. ) . This technique avoids additional artifacts caused by fat suppression techniques, but one needs to be aware of the fact that it does not eliminate geometric distortion artifacts occurring on the original images.…”

Section: Hardware and Pulse Sequencesmentioning

confidence: 99%

“…Several other dedicated MARS techniques have been developed, which however, have not yet been shown to be clinically feasible and feature a low spatial resolution or long acquisition times. These include prepolarized MRI (PMRI), single‐point imaging (SPI), field mapping, sweep imaging with Fourier transformation (SWIFT), bSSFP banding artifact correction, dual‐reversed‐gradient acquisitions, and short echo‐time projection reconstruction acquisitions …”

Section: Hardware and Pulse Sequencesmentioning

confidence: 99%

“…Besides orthopedic implants, other applications of MARS sequences in the presence of metal implants include radiotherapy planning close to implants, cerebral MRI in the presence of intracranial aneurysm clips, cardiac imaging, odontics, and breast imaging . However, these fields are not covered in this review.…”

Section: Clinical Applicationmentioning

confidence: 99%

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Advances in MRI around metal

Jungmann

Agten

Pfirrmann

et al. 2017

Magnetic Resonance Imaging

161

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Section: Hardware and Pulse Sequencesmentioning

confidence: 99%

Section: Hardware and Pulse Sequencesmentioning

confidence: 99%

See 1 more Smart Citation

Advances in MRI around metal

Jungmann

Agten

Pfirrmann

et al. 2017

Magnetic Resonance Imaging

161

166

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“…This makes diffusion acquisitions sensitive to artifacts produced by Nyquist ghosting, chemical shift and local susceptibility effects, among others [13, 62]. When considering acquisition orientation, EPI has a limited signal bandwidth in the phase-encoding direction, with local inhomogeneities producing geometric distortion along that direction [63, 64]. …”

Section: Discussionmentioning

confidence: 99%

“…These eddy current effects are only detectable in the phase-encoding direction [2]. All these artifacts can be reduced during acquisition [68, 69] and with post-processing techniques [64, 70–72], but these corrections could also affect diffusion tensor estimation [73]. …”

Section: Discussionmentioning

confidence: 99%

Effects of Orientation and Anisometry of Magnetic Resonance Imaging Acquisitions on Diffusion Tensor Imaging and Structural Connectomes

et al. 2017

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Diffusion-weighted imaging (DWI) quantifies water molecule diffusion within tissues and is becoming an increasingly used technique. However, it is very challenging as correct quantification depends on many different factors, ranging from acquisition parameters to a long pipeline of image processing. In this work, we investigated the influence of voxel geometry on diffusion analysis, comparing different acquisition orientations as well as isometric and anisometric voxels. Diffusion-weighted images of one rat brain were acquired with four different voxel geometries (one isometric and three anisometric in different directions) and three different encoding orientations (coronal, axial and sagittal). Diffusion tensor scalar measurements, tractography and the brain structural connectome were analyzed for each of the 12 acquisitions. The acquisition direction with respect to the main magnetic field orientation affected the diffusion results. When the acquisition slice-encoding direction was not aligned with the main magnetic field, there were more artifacts and a lower signal-to-noise ratio that led to less anisotropic tensors (lower fractional anisotropic values), producing poorer quality results. The use of anisometric voxels generated statistically significant differences in the values of diffusion metrics in specific regions. It also elicited differences in tract reconstruction and in different graph metric values describing the brain networks. Our results highlight the importance of taking into account the geometric aspects of acquisitions, especially when comparing diffusion data acquired using different geometries.

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Physical limits to human brain B0 shimming with spherical harmonics, engineering implications thereof

Meneses

Amadon

2022

Magn Reson Mater Phy

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Objective As the MRI main magnetic field rises for improved Signalto-Noise Ratio, susceptibility-induced B0-inhomogeneity increases proportionally, aggravating related artifacts. Considering only susceptibility disparities between air and biological tissue, we explore the topological conditions for which perfect shimming could be performed in a Region of Interest (ROI) such as the human brain or part thereof. Materials and Methods After theoretical considerations for perfect shimming, spherical harmonic (SH) shimming simulations of very high degree are performed, based on a 100-subject database of 1.7-mmresolved brain fieldmaps acquired at 3 T . In addition to the whole brain, shimmed ROIs include slabs targeting the prefrontal cortex, both or single temporal lobes, or spheres in the frontal brain above the nasal sinus. Results and DiscussionWe show "perfect" SH shimming is possible only if the ROI can be contained in a sphere that does not enclose sources of magnetic field inhomogeneity, which are gathered at the air-tissue interface. We establish a 13Hz inhomogeneity hard shim limit at 7 T for whole brain SH shimming, that can only be attained at shimming degree higher than 90. On the other hand, under limited power and SH degree resources, 3D regionspecific shimming is shown to greatly improve homogeneity in critical zones such as the prefrontal cortex and around ear canals.

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Simulated field maps for susceptibility artefact correction in interventional MRI

Abstract: The proposed simulated field maps facilitate susceptibility artefact reduction near the resection. Accurate air-tissue segmentation is key to achieving accurate simulation. The proposed simulation approach is adaptable to different iMRI and neurosurgical applications.

Cited by 4 publications

References 23 publications

Advances in MRI around metal

Advances in MRI around metal

Effects of Orientation and Anisometry of Magnetic Resonance Imaging Acquisitions on Diffusion Tensor Imaging and Structural Connectomes

Physical limits to human brain B0 shimming with spherical harmonics, engineering implications thereof

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