Name: Magnetic Resonance Imaging of Multiple Sclerosis at 7.0 Tesla (Video) | JoVE Journal
Uploaded: 2021-02-19T14:00:00.000+00:00
Duration: 8 min 51 s
Description: Learn ultrahigh field MRI protocols for multiple sclerosis research at 7.0 Tesla. This method enables superior detection of MS-specific neuroimaging markers including central vein signs and hypointense rim structures.

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5 minutes

This project (T.N.) has received funding in part from the European Research Council (ERC) under the European Union&#39;s Horizon 2020 research and innovation program under grant agreement No 743077 (ThermalMR). The authors wish to thank the teams at the Berlin Ultrahigh Field Facility (B.U.F.F.), Max Delbrueck Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany; at the The Swedish National 7T Facility, Lund University Bioimaging Center, Lund University, Lund, Sweden and at the ECOTECH-COMPLEX, Maria Curie-Sk&#322;odowska University, Lublin, Poland for technical and other assistance.

There are no competing financial interests to be declared.

The protocol presented here describes a series of MRI sequences with different contrasts that are typically used when examining MS patients at 7.0 T. Together with emerging technological developments, they provide the basis for explorations into more advanced applications in metabolic or functional imaging.
Aside from brain lesions, lesions in the spinal cord frequently affect MS patients causing motor, sensory and autonomic dysfunction. However spinal cord imaging, particularly at 7.0 T, is t...

Multiple sclerosis (MS) is the most common chronic inflammatory and demyelinating disease of the central nervous system (CNS) that causes pronounced neurological disability in younger adults and leads to long term disability1,2. The pathological hallmark of MS is the accumulation of demyelinating lesions that occur in the gray and white matter of the brain and also diffuse neurodegeneration in the entire brain, even in normal-appearing white matter (NAWM)3,4. MS pathology suggests that inflammation drives tissue injury at all stages of the disease, even during the progressive stages of disease5. The first clinical manifestations of MS are commonly accompanied by reversible episodes of neurological deficits and referred to as a clinically isolated syndrome (CIS), when only suggestive of MS6,7. In the absence of a clear-cut CIS, caution should be exercised in making an MS diagnosis: the diagnosis should be confirmed by follow-up and initiation of long-term disease-modifying therapies should be postponed, pending additional evidence8.
Magnetic resonance imaging (MRI) is an indispensable tool in diagnosing MS and monitoring disease progression9,10,11. MRI at magnetic field strengths of 1.5 T and 3 T currently represents a crucial diagnostic tool in clinical practice to detect spin-spin relaxation time weighted (T2) hyperintense lesions and establish accurate diagnosis of MS based on the current version of the 2017 McDonald criteria8. Diagnostic criteria for MS emphasize the need to demonstrate dissemination of lesions in space and time, and to exclude alternative diagnoses8,12. Contrast enhanced MRI is the only method to assess acute disease and acute inflammation8but increasing concerns regarding potential long-term gadolinium brain deposition could potentially restrict contrast application as an important diagnostic tool13,14,17. Additionally, the differentiation of MS lesions from brain white matter lesions of other origins can sometimes be challenging due to their resembling morphology at lower magnetic field strengths.
While MRI is certainly the best diagnostic tool for MS patients, MR examinations and protocols should follow guidelines of the Magnetic Resonance Imaging in MS group (MAGNIMS) in Europe18,19 or the Consortium of Multiple Sclerosis Centers (CMSC) in North America20 for the diagnosis, prognosis and monitoring of MS patients. Standardized quality control studies in accordance with the latest guidelines across different hospitals and countries are also crucial21.
MRI protocols tailored for MS diagnosis and disease progression monitoring comprise multiple MRI contrasts including contrast governed by the longitudinal relaxation time T1, the spin-spin relaxation time T2, the effective spin-spin relaxation time T2*, and diffusion weighted imaging (DWI)22. Harmonization initiatives provided consensus reports for MRI in MS to move towards standardized protocols that facilitate clinical translation and comparison of data across sites23,24,25. T2-weighted imaging is well established and frequently used in clinical practice for identification of white matter (WM) lesions, which are characterized by hyperintense appearance26,27. While being an important diagnostic criterion for MS28, the WM lesion load correlates only weakly with clinical disability, due to its lack of specificity for lesion severity and the underlying pathophysiology26,27,29. This observation has triggered explorations into parametric mapping of the transverse relaxation time T2 30. T2*-weighted imaging has become increasingly important in imaging MS. The central vein sign in T2* weighted MRI is considered to be a specific imaging marker for MS lesions27,31,32,33. T2* is sensitive to iron deposition34,35, which may relate to disease duration, activity and severity36,37,38. T2* was also reported to reflect brain tissue changes in patients with minor deficits and early MS, and thus may become a tool to assess the development of MS already at an early stage39,40.
Improvements in MRI technology promise to better identify changes in the CNS of MS patients and to provide clinicians with a better guide to enhance the accuracy and speed of an MS diagnosis11. Ultrahigh &#64257;eld (UHF, B0&#8805;7.0 T) MRI benefits from an increase in signal-to-noise ratio (SNR) that can be invested in enhanced spatial or temporal resolutions, both key to superior imaging for more accurate and definitive diagnoses41,42. Transmission field (B1+) inhomogeneities that are an adverse attribute of the 1H radio-frequency used at ultrahigh magnetic fields43 would benefit from multichannel transmission using parallel transmit (pTx) RF coils and RF pulse design approaches that enhance B1+ homogeneity and thus facilitate uniform coverage of the brain44.
With the advent of 7.0 T MRI, we have achieved more insight into demyelinating diseases such as MS with respect to increased sensitivity and specificity of lesion detection, central vein sign identification, leptomeningeal enhancement, and even with respect to metabolic changes45. MS lesions have long been shown from histopathological studies to form around veins and venules46. The perivenous distribution of lesions (central vein sign) can be identified with T2* weighted MRI46,47,48 at 3.0 T or 1.5 T, but can be best identified with UHF-MRI at 7.0 T49,50,51,52. Other than the central vein sign, UHF-MRI at 7.0 T has improved or uncovered MS-specific markers such as hypointense rim structures and differentiation of MS grey matter lesions53,54,55,56. A better delineation of these markers with UHF-MRI promises to overcome some of the challenges of differentiating MS lesions from those occurring in other neuroinflammatory conditions such as Susac syndrome53 and neuromyelitis optica54, while also identifying common pathogenetic mechanisms in other conditions or variants of MS such as Bal&#243;&#39;s concentric sclerosis57,58.
Recognizing the challenges and opportunities of UHF-MRI for the detection and differentiation of MS lesions, this article describes our current technical approach to study cerebral white and grey matter lesions in MS patients at 7.0 T using different imaging techniques. The up-to-date protocol includes the preparation of the MR setup including the radiofrequency (RF) coils tailored to the UHF-MR, standardized screening, safety and interview procedures with MS patients, patient positioning in the MR scanner and acquisition of brain scans dedicated to MS. The article is meant to guide imaging experts, basic researchers, clinical scientists, translational researchers, and technologists with all levels of experience and expertise ranging from trainees to advanced users and applications experts into the field of UHF-MRI in MS patients, with the ultimate goal of synergistically connecting technology development and clinical application across disciplinary domains.

<table><tbody><tr><td>7T TX/RX 24 Ch Head Coil</td><td>Nova Medical, Inc., Wilmington, USA</td><td>NM008-24-7S-013</td><td>1-channel circular polarized (CP) transmit (Tx), 24-channel receive (Rx) RF head coil</td></tr><tr><td>Magnetom 7T System</td><td>Siemens Healthineers, Erlangen, Germany</td><td>MRB1076</td><td>7.0 T whole body research scanner</td></tr><tr><td>syngoMR B17 Software</td><td>Siemens Healthineers, Erlangen, Germany</td><td>B17A</td><td>image processing software for the Magnetom 7T system</td></tr></tbody></table>

magnetic resonance imaging of multiple sclerosis at 7.0 tesla

Magnetic Resonance Imaging of Multiple Sclerosis at 7.0 Tesla

The overall goal of this article is to demonstrate a state-of-the-art ultrahigh field (UHF) magnetic resonance (MR) protocol of the brain at 7.0 Tesla in multiple sclerosis (MS) patients. MS is a chronic inflammatory, demyelinating, neurodegenerative disease that is characterized by white and gray matter lesions. Detection of spatially and temporally disseminated T2-hyperintense lesions by the use of MRI at 1.5 T and 3 T represents a crucial diagnostic tool in clinical practice to establish accurate diagnosis of MS based on the current version of the 2017 McDonald criteria. However, the differentiation of MS lesions from brain white matter lesions of other origins can sometimes be challenging due to their resembling morphology at lower magnetic field strengths (typically 3 T). Ultrahigh field MR (UHF-MR) benefits from increased signal-to-noise ratio and enhanced spatial resolution, both key to superior imaging for more accurate and definitive diagnoses of subtle lesions. Hence, MRI at 7.0 T has shown encouraging results to overcome the challenges of MS differential diagnosis by providing MS-specific neuroimaging markers (e.g., central vein sign, hypointense rim structures and differentiation of MS grey matter lesions). These markers and others can be identified by other MR contrasts other than T1 and T2 (T2*, phase, diffusion) and substantially improve the differentiation of MS lesions from those occurring in other neuroinflammatory conditions such as neuromyelitis optica and Susac syndrome. In this article, we describe our current technical approach to study cerebral white and grey matter lesions in MS patients at 7.0 T using different MR acquisition methods. The up-to-date protocol includes the preparation of the MR setup including the radio-frequency coils customized for UHF-MR, standardized screening, safety and interview procedures with MS patients, patient positioning in the MR scanner and acquisition of dedicated brain scans tailored for examining MS.

A 26-year-old woman diagnosed with relapsing remitting MS (RRMS) was examined at 7.0 T using the above protocols (Figure 11). Some distortions in the B1+ profile can be observed in the MR images. This is anticipated when moving to higher resonance frequencies43; the shorter wavelengths increase destructive and constructive interferences105,106. To...

Here, we present a protocol to acquire magnetic resonance (MR) images of multiple sclerosis (MS) patient brains at 7.0 Tesla. The protocol includes preparation of the setup including the radio-frequency coils, standardized interview procedures with MS patients, subject positioning in the MR scanner and MR data acquisition.

The overall goal of this article is to demonstrate a state-of-the-art ultrahigh field (UHF) magnetic resonance (MR) protocol of the brain at 7.0 Tesla in ...

magnetic-resonance-imaging-of-multiple-sclerosis-at-70-tesla

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Learn ultrahigh field MRI protocols for multiple sclerosis research at 7.0 Tesla. This method enables superior detection of MS-specific neuroimaging markers including central vein signs and hypointense rim structures.

Magnetic Resonance Imaging of Multiple Sclerosis at 7.0 Tesla

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