Dataset Information

Chronic multiple sclerosis lesions: characterization with high-field-strength MR imaging.

ABSTRACT:

Purpose

To elucidate the mechanism of magnetic resonance (MR) imaging contrast in multiple sclerosis (MS) lesion appearance by using susceptibility-weighted imaging and to assess with histologic correlation the role of iron and myelin in generating this MR imaging contrast.

Materials and methods

Each patient provided written consent to a human subject protocol approved by an institutional review board. High-spatial-resolution susceptibility-weighted 7.0-T MR images were obtained in 21 patients with MS. Contrast patterns in quantitative phase and R2* images, derived from 7.0-T data, were investigated in 220 areas defined as chronic MS lesions on conventional T2-weighted fluid-attenuated inversion recovery, T2-weighted, and T1-weighted spin-echo images. The presence of positive or negative phase shifts (ie, decreased or increased MR frequency, respectively) was assessed in each lesion. In addition, postmortem MR imaging was performed at 7.0 T and 11.7 T, and its results were correlated with those of immunohistochemical staining specific for myelin, iron, and ferritin.

Results

The majority (133 [60.5%] of 220) of the identified lesions had a normal phase and reduced R2*. A substantial fraction of the lesions (84 [38.2%] of 220) had negative phase shift, either uniformly or at their rim, and a variety of appearances on R2* maps. These two lesion contrast patterns were reproduced in the postmortem MR imaging study. Comparison with histologic findings showed that, while R2* reduction corresponded to severe loss of both iron and myelin, negative phase shift corresponded to focal iron deposits with myelin loss.

Conclusion

Combined analysis of 7.0-T R2* and phase data may help in characterizing the pathologic features of MS lesions. The observed R2* decreases suggest profound myelin loss, whereas negative phase shifts suggest a focal iron accumulation.

SUBMITTER: Yao B

PROVIDER: S-EPMC3244667 | biostudies-literature | 2012 Jan

REPOSITORIES: biostudies-literature

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Publications

Chronic multiple sclerosis lesions: characterization with high-field-strength MR imaging.

Yao Bing B Bagnato Francesca F Matsuura Eiji E Merkle Hellmut H van Gelderen Peter P Cantor Fredric K FK Duyn Jeff H JH

Radiology 20111114 1

<h4>Purpose</h4>To elucidate the mechanism of magnetic resonance (MR) imaging contrast in multiple sclerosis (MS) lesion appearance by using susceptibility-weighted imaging and to assess with histologic correlation the role of iron and myelin in generating this MR imaging contrast.<h4>Materials and methods</h4>Each patient provided written consent to a human subject protocol approved by an institutional review board. High-spatial-resolution susceptibility-weighted 7.0-T MR images were obtained i ...[more]

PMID: 22084205

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Project description:Purpose To evaluate the ability of high-gradient-diffusion magnetic resonance (MR) imaging by using gradient strengths of up to 300 mT/m to depict axonal disease in lesions and normal-appearing white matter (NAWM) in patients with multiple sclerosis (MS) and to compare high-gradient-diffusion MR findings in these patients with those in healthy control subjects. Materials and Methods In this HIPAA-compliant institutional review board-approved prospective study in which all subjects provided written informed consent, six patients with relapsing-remitting MS and six healthy control subjects underwent diffusion-weighted imaging with a range of diffusion weightings performed with a 3-T human MR imager by using gradient strengths of up to 300 mT/m. A model of intra-axonal, extra-axonal, and free water diffusion was fitted to obtain estimates of axon diameter and density. Differences in axon diameter and density between lesions and NAWM in patients with MS were assessed by using the nonparametric Wilcoxon matched-pairs signed rank test, and differences between NAWM in subjects with MS and white matter in healthy control subjects were assessed by using the Mann-Whitney U test. Results MS lesions showed increased mean axon diameter (10.3 vs 7.9 ?m in the genu, 10.4 vs 9.3 ?m in the body, and 10.6 vs 8.2 ?m in the splenium; P < .05) and decreased axon density ([0.48 vs 1.1] × 10(10)/m(2) in the genu, [0.40 vs 0.70] × 10(10)/m(2) in the body, and [0.35 vs 1.1] × 10(10)/m(2) in the splenium; P < .05) compared with adjacent NAWM. No significant difference in mean axon diameter or axon density was detected between NAWM in subjects with MS and white matter in healthy control subjects. Conclusion High-gradient-diffusion MR imaging using gradient strengths of up to 300 mT/m can be used to characterize axonal disease in patients with MS, with results that agree with known trends from neuropathologic data showing increased axon diameter and decreased axon density in MS lesions when compared with NAWM. (©) RSNA, 2016 Online supplemental material is available for this article.

Project description:Magnetic resonance imaging (MRI) is a fundamental tool in the diagnosis and management of neurological diseases such as multiple sclerosis (MS). New portable, low-field strength, MRI scanners could potentially lower financial and technical barriers to neuroimaging and reach underserved or disabled populations, but the sensitivity of these devices for MS lesions is unknown. We sought to determine if white matter lesions can be detected on a portable 64mT scanner, compare automated lesion segmentations and total lesion volume between paired 3T and 64mT scans, identify features that contribute to lesion detection accuracy, and explore super-resolution imaging at low-field. In this prospective, cross-sectional study, same-day brain MRI (FLAIR, T1w, and T2w) scans were collected from 36 adults (32 women; mean age, 50 ± 14 years) with known or suspected MS using Siemens 3T (FLAIR: 1 mm isotropic, T1w: 1 mm isotropic, and T2w: 0.34-0.5 × 0.34-0.5 × 3-5 mm) and Hyperfine 64mT (FLAIR: 1.6 × 1.6 × 5 mm, T1w: 1.5 × 1.5 × 5 mm, and T2w: 1.5 × 1.5 × 5 mm) scanners at two centers. Images were reviewed by neuroradiologists. MS lesions were measured manually and segmented using an automated algorithm. Statistical analyses assessed accuracy and variability of segmentations across scanners and systematic scanner biases in automated volumetric measurements. Lesions were identified on 64mT scans in 94% (31/33) of patients with confirmed MS. The average smallest lesions manually detected were 5.7 ± 1.3 mm in maximum diameter at 64mT vs 2.1 ± 0.6 mm at 3T, approaching the spatial resolution of the respective scanner sequences (3T: 1 mm, 64mT: 5 mm slice thickness). Automated lesion volume estimates were highly correlated between 3T and 64mT scans (r = 0.89, p < 0.001). Bland-Altman analysis identified bias in 64mT segmentations (mean = 1.6 ml, standard error = 5.2 ml, limits of agreement = -19.0-15.9 ml), which over-estimated low lesion volume and under-estimated high volume (r = 0.74, p < 0.001). Visual inspection revealed over-segmentation was driven venous hyperintensities on 64mT T2-FLAIR. Lesion size drove segmentation accuracy, with 93% of lesions > 1.0 ml and all lesions > 1.5 ml being detected. Using multi-acquisition volume averaging, we were able to generate 1.6 mm isotropic images on the 64mT device. Overall, our results demonstrate that in established MS, a portable 64mT MRI scanner can identify white matter lesions, and that automated estimates of total lesion volume correlate with measurements from 3T scans.

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Project description:The location and extent of white matter lesions on magnetic resonance imaging (MRI) are important criteria for diagnosis, follow-up and prognosis of multiple sclerosis (MS). Clinical trials have shown that quantitative values, such as lesion volumes, are meaningful in MS prognosis. Manual lesion delineation for the segmentation of lesions is, however, time-consuming and suffers from observer variability. In this paper, we propose MSmetrix, an accurate and reliable automatic method for lesion segmentation based on MRI, independent of scanner or acquisition protocol and without requiring any training data. In MSmetrix, 3D T1-weighted and FLAIR MR images are used in a probabilistic model to detect white matter (WM) lesions as an outlier to normal brain while segmenting the brain tissue into grey matter, WM and cerebrospinal fluid. The actual lesion segmentation is performed based on prior knowledge about the location (within WM) and the appearance (hyperintense on FLAIR) of lesions. The accuracy of MSmetrix is evaluated by comparing its output with expert reference segmentations of 20 MRI datasets of MS patients. Spatial overlap (Dice) between the MSmetrix and the expert lesion segmentation is 0.67 ± 0.11. The intraclass correlation coefficient (ICC) equals 0.8 indicating a good volumetric agreement between the MSmetrix and expert labelling. The reproducibility of MSmetrix' lesion volumes is evaluated based on 10 MS patients, scanned twice with a short interval on three different scanners. The agreement between the first and the second scan on each scanner is evaluated through the spatial overlap and absolute lesion volume difference between them. The spatial overlap was 0.69 ± 0.14 and absolute total lesion volume difference between the two scans was 0.54 ± 0.58 ml. Finally, the accuracy and reproducibility of MSmetrix compare favourably with other publicly available MS lesion segmentation algorithms, applied on the same data using default parameter settings.

Dataset Information

Chronic multiple sclerosis lesions: characterization with high-field-strength MR imaging.

Purpose

Materials and methods

Results

Conclusion

Publications

Chronic multiple sclerosis lesions: characterization with high-field-strength MR imaging.

Similar Datasets

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