Detecting cortical lesions in multiple sclerosis at 7 T using white matter signal attenuation

Abstract

Cortical lesions have recently been a focus of multiple sclerosis (MS) MR research. In this study, we present a white matter signal attenuating sequence optimized for cortical lesion detection at 7 T. The feasibility of white matter attenuation (WHAT) for cortical lesion detection was determined by scanning eight patients (four relapsing/remitting MS, four secondary progressive MS) at 7 T. WHAT showed excellent gray matter–white matter contrast, and cortical lesions were hyperintense to the surrounding cortical gray matter, The sequence was then optimized for cortical lesion detection by determining the set of sequence parameters that produced the best gray matter–cortical lesion contrast in a 10-min scan. Despite the B1 inhomogeneities common at ultra-high field strengths, WHAT with an adiabatic inversion pulse showed good cortical lesion detection and would be a valuable component of clinical MS imaging protocols.

Multicontrast MR Imaging at 7T in Multiple Sclerosis: Highest Lesion Detection in Cortical Gray Matter with 3D-FLAIR

“…One of these studies by using T2*-weighted gradient-echo images even suggested that this sequence should be the new criterion standard for the detection of cortical lesions in patients with MS. 33 Another recent study reported that white matter signal attenuation at 7T is feasible and is able to detect cortical abnormalities at 7T. 35 To our knowledge, the value of the recommended sequences for clinical use at 7T has not yet been investigated nor has the use of DIR. Our results show that the highest total cortical lesion detection at 7T is gained with 3D-FLAIR.…”

Cortical imaging in multiple sclerosis

“…Bluestein et al [24] implemented a white matter signal attenuating sequence (WHAT) at 7T, by optimizing the gray matter-white matter and gray matter-cortical lesion contrast. Mainly mixed lesions were detected well, whereas the detection of subpial lesions proved to be more difficult.…”

Optimization of white-matter-nulled magnetization prepared rapid gradient echo (MP-RAGE) imaging

“…The inversion time is usually set to null or significantly attenuate cerebrospinal fluid (CSF) signal, which results in good white matter (WM) ‐ gray matter (GM) contrast. This sequence is routinely used in volumetric analysis, WM‐GM segmentation, epilepsy imaging as well as in the detection and characterization of lesions from multiple sclerosis (MS) and other WM degenerative diseases . We refer to this sequence, henceforth, as CSF‐nulled (CSFn) MP‐RAGE or conventional MP‐RAGE.…”

“…We refer to this sequence, henceforth, as CSF‐nulled (CSFn) MP‐RAGE or conventional MP‐RAGE. A variant of the MP‐RAGE method was recently reported by Bluestein et al at 7 Tesla (T) , where WM signal rather than CSF signal was nulled for better visualization of cortical MS lesions at 7T. We refer to this variant sequence as WM‐nulled (WMn) MP‐RAGE.…”

“…However, for WMn MP‐RAGE, the scan parameters have not yet been carefully optimized from a scan efficiency and blurring standpoint, to the best of our knowledge, especially at 7T. Bluestein et al who used the WMn MP‐RAGE sequence at 7T for cortical MS lesion characterization, did not optimize scan parameters like TS and TR for SNR efficiency but rather used the shortest possible TS (3.7s) that achieved tolerable SAR. Tourdias et al further optimized the WMn MP‐RAGE sequence for visualization of intra‐thalamic nuclei at 7T, taking into account SNR and contrast efficiency, and reported an optimum TS of 6 s, but did not consider the effect of other sequence parameters like N and BW.…”