Histogram analysis of quantitative T₁ and MT maps from ultrahigh field MRI in clinically isolated syndrome and relapsing–remitting multiple sclerosis

Abstract

This study used quantitative MRI to study normal appearing white matter (NAWM) in patients with clinically isolated syndromes suggestive of multiple sclerosis and relapsing-remitting multiple sclerosis (RRMS). This was done at ultrahigh field (7 T) for greater spatial resolution and sensitivity. 17 CIS patients, 11 RRMS patients, and 20 age-matched healthy controls were recruited. They were scanned using a 3D inversion recovery turbo field echo sequence to measure the longitudinal relaxation time (T1). A 3D magnetization transfer prepared turbo field echo (MT-TFE) sequence was also acquired, first without a presaturation pulse and then with the MT presaturation pulse applied at -1.05 kHz and +1.05 kHz off resonance from water to produce two magnetization transfer ratio maps (MTR(-) and MTR(+)). Histogram analysis was performed on the signal from the voxels in the NAWM mask. The upper quartile cut-off of the T1 histogram was significantly higher in RRMS patients than in controls (p < 0.05), but there was no difference in CIS. In contrast, MTR was significantly different between CIS or RRMS patients and controls (p < 0.05) for most histogram measures considered. The difference between MTR(+) and MTR(-) signals showed that NOE contributions dominated the changes found. There was a weak negative correlation (r = -0.46, p < 0.05) between the mode of T1 distributions and healthy controls' age; this was not significant for MTR(+) (r = -0.34, p > 0.05) or MTR(-) (r = 0.13, p > 0.05). There was no significant correlation between the median of T1, MTR(-), or MTR(+) and the age of healthy controls. Furthermore, no significant correlation was observed between EDSS or disease duration and T1, MTR(-), or MTR(+) for either CIS or RRMS patients. In conclusion, MTR was found to be more sensitive to early changes in MS disease than T1.

Reduced Myelin Signal in Normal-appearing White Matter in Neuromyelitis Optica Measured by 7T Magnetic Resonance Imaging

“…Briefly, whole brain three-dimensional (3D) phase-sensitive inversion recovery (PSIR) images (spatial resolution = 0.6 × 0.6 × 0.6 mm 3 ) were acquired and segmented to obtain a WM mask 39 . Then, 3D magnetization-prepared rapid gradient echo (MPRAGE) sequences with seven inversion times were acquired (spatial resolution = 1.25 × 1.25 × 1.25 mm 3 ) and processed to produce quantitative measurements of T1 38 . In addition, MT images were acquired for quantitative measurement of MTRs derived from two raw images: MT nosat (proton- and T2*-weighted imaging with no presaturation), and MT sat (presaturation to water) (spatial resolution = 0.6 × 0.6 × 0.6 mm 3 ) 36,37 .…”

Magnetization Transfer MRI of Breast Cancer in the Community Setting: Reproducibility and Preliminary Results in Neoadjuvant Therapy

“…Voxel values were both averaged across the tumor and binned into histograms for the therapeutic response study. Voxel distributions quantified the Kolmogorov–Smirnov test, and histogram analysis, similar to methods previously used to characterize MTR distributions in the brain (22). The following histogram parameters were derived from the histograms of MTR values: standard deviation; kurtosis; and the 25th, 75th, and 95th percentiles of the tumor MTR, where the nth percentile is the point at which n% of the voxel values that form the histogram are found to the left.…”

Seven‐Tesla Magnetization Transfer Imaging to Detect Multiple Sclerosis White Matter Lesions

“…Patients participating in a 7T MT imaging MRI research study underwent 3T-FLAIR imaging, on the same day. 18 The hypothesis of the study was that the lesion detection rate of supratentorial white matter in patients with MS is similar between 7T MT w and 3T FLAIR.…”

“…As the ability to acquire optimized FLAIR imaging at 7T as described by Saranatan and colleagues to detect MS white matter lesions was lacking at the time of our study, and as 7T FLAIR images obtained without RF optimization provided unsatisfactory contrast for white matter lesion detection (see Results section), here we used 3T images instead. Patients participating in a 7T MT imaging MRI research study underwent 3T‐FLAIR imaging, on the same day . The hypothesis of the study was that the lesion detection rate of supratentorial white matter in patients with MS is similar between 7T MT w and 3T FLAIR.…”

“…At 7T, MT with submilliliter imaging resolution enables detection of MS cortical lesions and improves quantitative assessment of nonlesional “normal appearing” brain tissue . Therefore, 7T MT provides high‐resolution information on myelin integrity.…”