Magnetic Resonance Imaging of Multiple Sclerosis at 7.0 Tesla

Summary

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.

Abstract

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.

Introduction

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 disability^1,2. 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, eve....

Protocol

This protocol is for studies that are approved by the ethics committee of the Charité - Universitätsmedizin Berlin (approval number: EA1/222/17, 2018/01/08) and the Data Protection Division and Corporate Governance of the Charité - Universitätsmedizin Berlin. Informed consent has been obtained from all subjects prior of being included in the study.

1. Subjects

NOTE: Recruitment of MS patients usually takes place at few days up to some weeks prior to the MR investigations at 7.0 T.

1. Recruit MS patients by neurologists from the outpatient clinic on the basis of inclusion criteria (dep....

Results

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 interferences^105,106. To.......

Discussion

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.......

Materials

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