Quantitative Susceptibility Mapping and R2* Measured Changes during White Matter Lesion Development in Multiple Sclerosis: Myelin Breakdown, Myelin Debris Degradation and Removal, and Iron Accumulation.

Y Zhang,G.C.-Y Chiang,W Chen,J Comunale,W Zhu,A Gupta,D Pitt,G Askin,Y Wang,S.A Gauthier,D Zhou

doi:10.3174/ajnr.a4825

Abstract

Quantitative susceptibility mapping and R2* are sensitive to myelin and iron changes in multiple sclerosis lesions. This study was designed to characterize lesion changes on quantitative susceptibility mapping and R2* at various gadolinium-enhancement stages. This study included 64 patients with MS with different enhancing patterns in white matter lesions: nodular, shell-like, nonenhancing < 1 year old, and nonenhancing 1-3 years old. These represent acute, late acute, early chronic, and late chronic lesions, respectively. Susceptibility values measured on quantitative susceptibility mapping and R2* values were compared among the 4 lesion types. Their differences were assessed with a generalized estimating equation, controlling for Expanded Disability Status Scale score, age, and disease duration. We analyzed 203 lesions: 80 were nodular-enhancing, of which 77 (96.2%) were isointense on quantitative susceptibility mapping; 33 were shell-enhancing, of which 30 (90.9%) were hyperintense on quantitative susceptibility mapping; and 49 were nonenhancing lesions < 1 year old and 41 were nonenhancing lesions 1-3 years old, all of which were hyperintense on quantitative susceptibility mapping. Their relative susceptibility/R2* values were 0.5 ± 4.4 parts per billion/-5.6 ± 2.9 Hz, 10.2 ± 5.4 parts per billion/-8.0 ± 2.6 Hz, 20.2 ± 7.8 parts per billion/-3.1 ± 2.3 Hz, and 33.2 ± 8.2 parts per billion/-2.0 ± 2.6 Hz, respectively, and were significantly different (P < .005). Early active MS lesions with nodular enhancement show R2* decrease but no quantitative susceptibility mapping change, reflecting myelin breakdown; late active lesions with peripheral enhancement show R2* decrease and quantitative susceptibility mapping increase in the lesion center, reflecting further degradation and removal of myelin debris; and early or late chronic nonenhancing lesions show both quantitative susceptibility mapping and R2* increase, reflecting iron accumulation.

Highlights

BACKGROUND AND PURPOSEQuantitative susceptibility mapping and R2* are sensitive to myelin and iron changes in multiple sclerosis lesions
Lesion Analysis New white matter MS lesions were identified on the second MR imaging, which was performed at 0.77 Ϯ 0.37 year after the first MR imaging
Our results demonstrate the following QSM and R2* patterns for MS lesions: nodular-enhancing lesions on T1WI ϩ Gd that are isointense on QSM and hypointense on R2*; susceptibility increases and R2* decreases as lesions develop from nodular- to ring-enhancing; and increase in susceptibility and R2* in lesions that become nonenhancing

Summary

Methods

This study included 64 patients with MS with different enhancing patterns in white matter lesions: nodular, shell-like, nonenhancing Ͻ 1 year old, and nonenhancing 1–3 years old. These represent acute, late acute, early chronic, and late chronic lesions, respectively. The method of estimating lesion age referred to a previous study.[7] All these lesions were independently assessed by the 3 neuroradiologists to be hyperintense or isointense on QSM images. These 3 readings were combined, with all differences resolved by majority votes

Results

Discussion

Conclusion