Multisequence-imaging protocols to detect cortical lesions of patients with multiple sclerosis: observations from a post-mortem 3 Tesla imaging study

Abstract

Neocortical lesions (NLs) are an important component of multiple sclerosis (MS) pathology and may account for part of the physical and cognitive disability. Visualizing NLs of patients with MS using magnetic resonance imaging (MRI) poses several significant challenges. We optimized the inversion time (TI) of T(1)-based magnetization-prepared rapid acquisition gradient-echo (MPRAGE) images by suppressing the signal of the lesions and enhancing their appearance as hypointensities, on the basis of the derived quantitative T(1) measurements. The latter were achieved by the means of 2D inversion recovery fast spin echo (IR-FSE), repeated using different inversion times (TI). Comparisons of detection of NLs by MPRAGE and dual echo T(2) weighted (T(2)W) and proton density (PD) W. Four coronal brain slices from a deceased MS patient and two coronal brain slices from two formerly healthy donors were imaged using a 3 Tesla magnet (3 T) equipped with a multi-channel coil. Based upon the averaged T1 values computed from the MS specimen as well as visual inspection, an optimal TI of 380 ms was selected for the MPRAGE image. No NLs were seen in the specimens of the two healthy donors. Of the 40 total NLs observed, 8 (20%) were visible in all three sequences employed. Three (7.5%) NLs were visible only in the PDW image and 5 (12.5%) were seen only in the T(2)W image. Four NLs (10%) had clearly unique conspicuity in the MPRAGE image. Of those, 3 were retrospectively scored in the PDW image (1 NL) or in the T2W image (2 NLs). We conclude that for the detection of MS-related NLs, high-resolution T(1)-based MPRAGE and T(2)-W images offer complementary information and the combination of the two image sequences is crucial for increasing the sensitivity of detecting MS-induced NLs.

Figure 1. Cylindrical home-made tissue containers

The base ring of the container was manufactured from 140 mm inner diameter clear PVC sewer pipe of 28 (figure 1a) or 22 mm (figure 1b) height.

Figure 2. MPAGE (figure 2a) PDW (figure 2b) and T₂W (figure 2c) Images

The white dashed arrow points to a type-I NL visible only in the MPRAGE image, not visible in the PDW image and barely visible in the T₂W images.

Figure 3. PDW (figure 3a) and T₂W (figure 3b) Images

The white dashed arrow points to a type-I NL visible in both PD and T₂W images. The white solid arrow points to a type-II NL. As one can see, PDW images offered better visibility of both lesions. Additionally, the intracortical portion of the type-II NLs was not visible on the T₂W image. None of the NLs was identified on the MPRAGE image.