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MR identification of white matter abnormalities in multiple sclerosis: a comparison between 1.5 T and 4 T
M D Keiper1, R I Grossman, J A Hirsch
1Department of Radiology, University of Pennsylvania Medical Center, Philadelphia 19104, USA.
Background And Purpose:
Although MR spectroscopy and functional MR imaging of the brain have been successful at 4 T, conventional fast spin-echo imaging of the brain at 4 T has not been adequately evaluated. The purpose of this study was to compare the detection of white matter abnormalities in multiple sclerosis (MS) at 1.5 T and 4 T.
Methods:
Fifteen patients with clinically definite MS were imaged at both 1.5 T and 4 T within a 1-week period. Comparison was made between fast spin-echo long-TR images at both field strengths. Pulse sequences were tailored to maximize resolution and signal-to-noise ratio in clinically relevant imaging times (< 7 min). Four interpreters independently reviewed the images obtained at both field strengths in separate sessions and evaluated them for lesion identification, size, characterization, and subjective resolution. Differences in interpretations at 1.5 T and 4 T were subsequently recorded.
Results:
Images obtained at 4 T showed a mean of 88 more lesions as compared with images obtained at 1.5 T. All the lesions measured less than 5 mm and were typically aligned along perivascular spaces. Twenty-five consensually identified lesions on 4-T images were not seen at all on 1.5-T images. Moreover, 4-T images showed 56 additional consensually identified lesions, which were indistinct and seen only in retrospect on 1.5-T images. These lesions were frequently (n = 48) identified in large confluent areas of white matter signal intensity abnormality at 1.5 T. All observers also agreed that 4-T images subjectively enhanced the perception of normal perivascular spaces and small perivascular lesions.
Conclusion:
MR imaging at 4 T can depict white matter abnormalities in MS patients not detectable at 1.5 T through higher resolution with comparable signal-to-noise ratio and imaging times.
Insights
Higher magnetic field strength (4 T) MRI detects significantly more white matter lesions in multiple sclerosis (MS) patients than standard 1.5 T MRI. This advanced imaging technique improves lesion detection and characterization in MS.
Area of Science:
- Radiology
- Neuroimaging
- Magnetic Resonance Imaging
Background:
- Conventional fast spin-echo (FSE) brain imaging at 4 Tesla (T) remains inadequately evaluated despite successful applications of other MRI techniques at this field strength.
- Previous studies have demonstrated the efficacy of MR spectroscopy and functional MRI at 4 T.
Purpose of the Study:
- To compare the efficacy of 4 T versus 1.5 T MRI in detecting white matter abnormalities in patients with multiple sclerosis (MS).
Main Methods:
- Fifteen patients with definite MS underwent brain MRI at both 1.5 T and 4 T within one week.
- Fast spin-echo, long-TR sequences were optimized for resolution and signal-to-noise ratio within clinically feasible imaging times (< 7 minutes).
- Four independent interpreters evaluated images for lesion identification, size, characterization, and subjective resolution, comparing findings between the two field strengths.
Main Results:
- MRI at 4 T detected an average of 88 more white matter lesions per patient compared to 1.5 T.
- Twenty-five lesions identified at 4 T were completely missed at 1.5 T, and 56 additional lesions were better visualized at 4 T.
- 4 T imaging enhanced the visualization of normal perivascular spaces and small perivascular lesions, improving lesion characterization.
Conclusions:
- 4 T MRI offers superior detection of white matter abnormalities in MS patients compared to 1.5 T.
- The enhanced resolution at 4 T allows for visualization of lesions not detectable at lower field strengths, with comparable signal-to-noise ratio and imaging times.