Functional Magnetic Resonance Imaging of the Spinal Cord: Current Status and Future Developments

Cohen‐Adad, Julien

doi:10.1053/j.sult.2016.07.007

Cited by 35 publications

(36 citation statements)

References 67 publications

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“…The horizontally concatenated matrix ½ MA ÀMA (dimensions ½N voi Â 2N s ) has the effect of penalizing differences in the resulting shim fields over the shim VOI between inspired and expired states: With a regularization parameter of l ¼ 0, the 2 vectors of shim currents (i sjin , i sjex ) become independent, as if J 1 were optimized separately; whereas in the limit of large l, difference in the inspired and expired field maps (RIRO) is ignored, and the corresponding shim fields become identical. On its own, the minimization of Equation [8] does not guarantee a practical current solution. Hence, the fmincon function of MatLab (MathWorks) was used to find a constrained minimum to [8]: limiting the minimum and maximum current for each of the N s ¼ 24 channels to 6 1 A (27).…”

Section: Shim Optimizationmentioning

confidence: 99%

“…On its own, the minimization of Equation [8] does not guarantee a practical current solution. Hence, the fmincon function of MatLab (MathWorks) was used to find a constrained minimum to [8]: limiting the minimum and maximum current for each of the N s ¼ 24 channels to 6 1 A (27). These optimal current distributions were used to solve for the shim field offset and coupling coefficients in Equations [6] and [7] via the relation Ai s ¼ b s .…”

Section: Shim Optimizationmentioning

confidence: 99%

“…4). Using the training field maps from the first subject, for which no regularization was applied in the optimization (l ¼ 0 in Equation [8]), the L-curve method was employed to empirically select a regularization parameter of l ¼ 0:1, which was adopted for all the subsequent subjects.…”

Section: In Vivo Experimentsmentioning

confidence: 99%

“…Given the extent of these artifacts, along with the inherent subtlety of the signal changes associated with BOLD activation (typically on the order of 1%), fMRI of the spinal cord remains technically challenging. As noted recently by Cohen-Adad (8): "respirationinduced change in B 0 is one of the main reasons very few people dare to venture into fMRI experiments below the cervical level (p. 180)."…”

Section: Introductionmentioning

confidence: 99%

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Real‐time correction of respiration‐induced distortions in the human spinal cord using a 24‐channel shim array

Topfer

Foias

Stikov

et al. 2018

Magnetic Resonance in Med

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Section: Shim Optimizationmentioning

confidence: 99%

Section: Shim Optimizationmentioning

confidence: 99%

Section: In Vivo Experimentsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Real‐time correction of respiration‐induced distortions in the human spinal cord using a 24‐channel shim array

Topfer

Foias

Stikov

et al. 2018

Magnetic Resonance in Med

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“…In neuroimaging, breathing‐related field fluctuations can be measured as far away as in the brain, but are particularly prominent in the spine because of the proximity to the lungs . Indeed, breathing‐induced fields have been identified as one of the major challenges to overcome to achieve robust fMRI of the spinal cord …”

Section: Introductionmentioning

confidence: 99%

A method for correcting breathing‐induced field fluctuations in T2*‐weighted spinal cord imaging using a respiratory trace

Vannesjo

Clare

Kasper

et al. 2019

Magnetic Resonance in Med

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Purpose Spinal cord MRI at ultrahigh field is hampered by time‐varying magnetic fields associated with the breathing cycle, giving rise to ghosting artifacts in multi‐shot acquisitions. Here, we suggest a correction approach based on linking the signal from a respiratory bellows to field changes inside the spinal cord. The information is used to correct the data at the image reconstruction level. Methods The correction was demonstrated in the context of multi‐shot T2*‐weighted imaging of the cervical spinal cord at 7T. A respiratory trace was acquired during a high‐resolution multi‐echo gradient‐echo sequence, used for structural imaging and quantitative T2* mapping, and a multi‐shot EPI time series, as would be suitable for fMRI. The coupling between the trace and the breathing‐induced fields was determined by a short calibration scan in each individual. Images were reconstructed with and without trace‐based correction. Results In the multi‐echo acquisition, breathing‐induced fields caused severe ghosting in images with long TE, which led to a systematic underestimation of T2* in the spinal cord. The trace‐based correction reduced the ghosting and increased the estimated T2* values. Breathing‐related ghosting was also observed in the multi‐shot EPI images. The correction largely removed the ghosting, thereby improving the temporal signal‐to‐noise ratio of the time series. Conclusions Trace‐based retrospective correction of breathing‐induced field variations can reduce ghosting and improve quantitative metrics in multi‐shot structural and functional T2*‐weighted imaging of the spinal cord. The method is straightforward to implement and does not rely on sequence modifications or additional hardware beyond a respiratory bellows.

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Functional Neuroimaging of Nociceptive and Pain‐Related Activity in the Spinal Cord and Brain: Insights From Neurovascular Coupling Studies

Paquette

Jeffrey-Gauthier

Leblond

et al. 2018

The Anatomical Record

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Spinal cord and brain processes underlie pain perception, which produces systemic cardiovascular changes. In turn, the autonomic nervous system regulates vascular function in the spinal cord and brain in order to adapt to these systemic changes, while neuronal activity induces local vascular changes. Thus, autonomic regulation and pain processes in the brain and spinal cord are tightly linked and interrelated. The objective of this topical review is to discuss work on neurovascular coupling during nociceptive processing in order to highlight supporting evidence and limitations for the use of cerebral and spinal fMRI to investigate pain mechanisms and spinal nociceptive processes. Work on functional neuroimaging of pain is presented and discussed in relation to available neurovascular coupling studies and related issues. Perspectives on future work are also discussed with an emphasis on differences between the brain and the spinal cord and on different approaches that may be useful to improve current methods, data analyses and interpretation. In summary, this review highlights the lack of data on neurovascular coupling during nociceptive stimulation and indicates that hemodynamic and BOLD responses measured with fMRI may be biased by nonspecific vascular changes. Future neuroimaging studies on nociceptive and pain-related processes would gain further understanding of neurovascular coupling in the brain and spinal cord and should take into account the effects of systemic vascular changes that may affect hemodynamic responses. Anat Rec, 301:1585-1595, 2018. © 2018 Wiley Periodicals, Inc.

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Functional Magnetic Resonance Imaging of the Spinal Cord: Current Status and Future Developments

Cited by 35 publications

References 67 publications

Real‐time correction of respiration‐induced distortions in the human spinal cord using a 24‐channel shim array

Real‐time correction of respiration‐induced distortions in the human spinal cord using a 24‐channel shim array

A method for correcting breathing‐induced field fluctuations in T2*‐weighted spinal cord imaging using a respiratory trace

Functional Neuroimaging of Nociceptive and Pain‐Related Activity in the Spinal Cord and Brain: Insights From Neurovascular Coupling Studies

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