Effect of head motion on <scp>MRI B</scp><sub>0</sub> field distribution

Liu, Jiaen; Zwart, Jacco A. de; Gelderen, Peter van; Murphy‐Boesch, Joseph; Duyn, Jeff H.

doi:10.1002/mrm.27339

Cited by 47 publications

(62 citation statements)

References 43 publications

(76 reference statements)

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“…The field perturbations contained both slow‐drift and faster oscillatory patterns, which have been previously observed as well . The oscillatory contributions can be clearly attributed to the breathing cycle; the slower contributions could have diverse origins, including other physiological and metabolic sources, but may have been strongly driven by drifts in head position/orientation, as these have been found to generate important perturbations in the measured field at a similar order of magnitude . From these perturbations resulted diverse image artifacts (eg, Figure B), also consistent with previous reports .…”

Section: Discussionsupporting

confidence: 88%

Improved susceptibility‐weighted imaging for high contrast and resolution thalamic nuclei mapping at 7T

Jorge

Gretsch

Najdenovska

et al. 2020

Magnetic Resonance in Med

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Purpose:The thalamus is an important brain structure and neurosurgical target, but its constituting nuclei are challenging to image non-invasively. Recently, susceptibility-weighted imaging (SWI) at ultra-high field has shown promising capabilities for thalamic nuclei mapping. In this work, several methodological improvements were explored to enhance SWI quality and contrast, and specifically its ability for thalamic imaging. Methods: High-resolution SWI was performed at 7T in healthy participants, and the following techniques were applied: (a) monitoring and retrospective correction of head motion and B 0 perturbations using integrated MR navigators, (b) segmentation and removal of venous vessels on the SWI data using vessel enhancement filtering, and (c) contrast enhancement by tuning the parameters of the SWI phase-magnitude combination. The resulting improvements were evaluated with quantitative metrics of image quality, and by comparison to anatomo-histological thalamic atlases. Results: Even with sub-millimeter motion and natural breathing, motion and field correction produced clear improvements in both magnitude and phase data quality (76% and 41%, respectively). The improvements were stronger in cases of larger motion/field deviations, mitigating the dependence of image quality on subject performance. Optimizing the SWI phase-magnitude combination yielded substantial improvements in image contrast, particularly in the thalamus, well beyond previously reported SWI results. The atlas comparisons provided compelling evidence of anatomical correspondence between SWI features and several thalamic nuclei, for | 1219 JORGE Et al.

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Section: Discussionsupporting

confidence: 88%

Improved susceptibility‐weighted imaging for high contrast and resolution thalamic nuclei mapping at 7T

Jorge

Gretsch

Najdenovska

et al. 2020

Magnetic Resonance in Med

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“…At low saturation powers (<1 μT), the CrCESTw peak was sharper (Figure E) but not consistent between the contralateral regions. This is because the sharp CEST line‐shapes obtained with lower saturation powers not only are prone to the B 0 field inhomogeneity, but also can be easily disturbed by the B 0 fluctuation caused by animal respiration, motion and heating of the MRI shimming unit, which will lead to larger standard deviation as shown in Figure E. The above‐mentioned issue can be addressed by applying a higher saturation power, as shown in Figure F.…”

Section: Discussionmentioning

confidence: 99%

High‐resolution creatine mapping of mouse brain at 11.7 T using non‐steady‐state chemical exchange saturation transfer

et al. 2019

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The current study aims to optimize the acquisition scheme for the creatine chemical exchange saturation transfer weighted (CrCESTw) signal on mouse brain at 11.7 T, in which a strong magnetization transfer contrast (MTC) is present, and to further develop the polynomial and Lorentzian line‐shape fitting (PLOF) method for quantifying CrCESTw signal with a non‐steady‐state (NSS) acquisition scheme. Studies on a Cr phantom with cross‐linked bovine serum albumin (BSA) as well as on mouse brain demonstrated that the maximum CrCESTw signal was reached with a short saturation time determined by the rotating frame relaxation time of the MTC pool instead of the steady‐state saturation. The saturation power for the maximal signal was around 1–1.5 μT for Cr with 20% cross‐linked BSA and in vivo applications, but 2 μT was found to be most practical for signal stability. For the CrCEST acquisition with strong MTC interference, the optimal saturation power and length are completely different from those on Cr solution alone. This observation could be explained well using R1ρ theory by incorporating the strong MTC pool. Finally, a high‐resolution Cr map was obtained on mouse brain using the PLOF method with the NSS CEST acquisition and a cryogenic coil. The Cr map obtained by CEST showed homogenous intensity across the mouse brain except for regions with cerebrospinal fluid.

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“…Despite anesthesia, the influence of motion on the phase turned out to be high in some regions. 7 As a result, reliable estimate of small temperature rises everywhere in the brain was rendered difficult. Based on simulation, the strategy used here was to focus on a sagittal slice to possibly observe a temperature hotspot as measured in phantom studies with the same coil 20 and attempt detecting a horizontal temperature plateau in a zone relatively robust to head motion.…”

Section: Discussionmentioning

confidence: 99%

RF heating measurement using MR thermometry and field monitoring: Methodological considerations and first in vivo results

Ster

Mauconduit

Mirkes³

et al. 2020

Magnetic Resonance in Med

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Purpose: A MR thermometry (MRT) method with field monitoring is proposed to improve the measurement of small temperature variations induced in brain MRI exams. Methods: MR thermometry experiments were performed at 7 Tesla with concurrent field monitoring and RF heating. Images were reconstructed with nominal k-space trajectories and with first-order spherical harmonics correction. Experiments were performed in vitro with deliberate field disturbances and on an anesthetized macaque in 2 different specific absorption rate regimes, that is, at 50% and 100% of the maximal specific absorption rate level allowed in the International Electrotechnical Commission normal mode of operation. Repeatability was assessed by running a second separate session on the same animal. Results: Inclusion of magnetic field fluctuations in the reconstruction improved temperature measurement accuracy in vitro down to 0.02°C. Measurement precision in vivo was on the order of 0.15°C in areas little affected by motion. In the same region, temperature increase reached 0.5 to 0.8°C after 20 min of heating at 100% specific absorption rates and followed a rough factor of 2 with the 50% specific absorption rate scans. A horizontal temperature plateau, as predicted by Pennes bioheat model with thermal constants from the literature and constant blood temperature assumption, was not observed. Conclusion: Inclusion of field fluctuations in image reconstruction was beneficial for the measurement of small temperature rises encountered in standard brain exams. More work is needed to correct for motion-induced field disturbances to extract reliable temperature maps.

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Effect of head motion on MRI B₀ field distribution

Cited by 47 publications

References 43 publications

Improved susceptibility‐weighted imaging for high contrast and resolution thalamic nuclei mapping at 7T

Improved susceptibility‐weighted imaging for high contrast and resolution thalamic nuclei mapping at 7T

High‐resolution creatine mapping of mouse brain at 11.7 T using non‐steady‐state chemical exchange saturation transfer

RF heating measurement using MR thermometry and field monitoring: Methodological considerations and first in vivo results

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Effect of head motion on MRI B0 field distribution

Cited by 47 publications

References 43 publications

Improved susceptibility‐weighted imaging for high contrast and resolution thalamic nuclei mapping at 7T

Improved susceptibility‐weighted imaging for high contrast and resolution thalamic nuclei mapping at 7T

High‐resolution creatine mapping of mouse brain at 11.7 T using non‐steady‐state chemical exchange saturation transfer

RF heating measurement using MR thermometry and field monitoring: Methodological considerations and first in vivo results

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Effect of head motion on MRI B₀ field distribution