The Assessment of Structural Changes in MS Plaques and Normal Appearing White Matter Using Quantitative Magnetization Transfer Imaging (MTI)

Document Type: Original Paper

Authors

1 M.Sc. in Medical Physics, Medical Physics and Biomedical Engineering Dept., Tehran University of Medical Sciences, Tehran, Iran

2 Associate Professor, Medical Physics and Biomedical Engineering Dept., Tehran University of Medical Sciences, Tehran, Iran

3 Associate Professor, Neurology Dept., Tehran University of Medical Sciences, Tehran, Iran

4 Associate Professor, Radiology Dept., Tehran University of Medical Sciences, Tehran, Iran

5 Researcher, Medical Imaging Research Center, Imam Khomeini Hospital, Tehran University of Medical Sciences, Tehran, Iran

6 M.Sc. in Medical Physics, Center of Medical Imaging, Imam Khomeini Hospital, Tehran University of Medical Sciences, Tehran, Iran

7 M.Sc. in Medical Physics, Medical Imaging Research Center, Imam Khomeini Hospital, Tehran University of Medical Sciences, Tehran, Iran

Abstract

Introduction: Multiple sclerosis (MS) is a demyelinating disease of the central nervous system (CNS), affecting mostly young people at a mean age of 30 years. Magnetic resonance imaging (MRI) is one of the most specific and sensitive methods in diagnosing and detecting the evolution of multiple sclerosis disease. But it does not have the ability to differentiate between distinct histopathological heterogeneities that occur in MS lesions and brain tissue.Quantitative magnetization transfer imaging (qMTI) is a relatively new MRI technique which can be used to examine the pathological processes of the brain parenchyma which occur in MS patients.This quantitative MRI technique can provide more complete information about the extent and nature of the brain tissue destruction in multiple sclerosis, which cannot be detected by conventional MRI.
Material and Methods: In this study, twelve patients with relapsing-remitting MS and twelve healthy control subjects underwent conventional MR imaging including: T2-FSE, T1-SE and FLAIR sequences as well as quantitative magnetization transfer imaging. All the focal lesions were identified on T2-weighted images and were classified according to their signal hypointensity on T1-weighted scans. The white matter and MS lesions were segmented using a semi-automated system. MT ratio (MTR) histogram analysis was performed for the brain white matter and the average MTR value was calculated for the classified MS lesions.
Results: A significant reduction was found in MTR value of the normal appearing white matter (NAWM) in patients with relapsing-remitting MS, suggesting that MS is a more diffuse disease, affecting the whole brain tissue. A wide range changes in MTR values can be observed in MS lesions. MTR reduction is correlated with the degree of lesion hypointensity on T1-weighted scans. The lower MTR values of lesions that appear progressively more hypointense on T1-weigted images reflect varying degrees of demyelination and breakdown in the macromolecular structure of MS lesions. There was also a significant difference in MTR histogram parameters between the patients and control groups, accompanied by a total shift of NAWM-MTR histogram to the left.
Discussion and Conclusion: Based on theobtained result itcan be stated that MS has a diffused nature and the white matter abnormalities occurring outside T2-visible lesions affect the whole brain tissue. Quantitative magnetization transfer imaging can be used as a reliable method to assess both the overall disease burden and the intrinsic nature of the individual lesions in MS patients

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