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Lesion load quantification on fast-FLAIR, rapid acquisition relaxation-enhanced, and gradient spin echo brain MRI
M Rovaris1, M A Rocca, I Yousry
1Department of Neuroscience, Scientific Institute Ospedale San Raffaele, Milan, Italy.
Abstract:
Previous studies have addressed the issue of the usefullness of fast fluid-attenuated (fast-FLAIR), rapid acquisition relaxation-enhanced (RARE), and gradient spin echo (GRASE) sequences in small groups of patients with multiple sclerosis (MS). The aim of this study was to assess and compare the lesion volumes and the intra-rater reproducibility of such measurements using fast-FLAIR, dual echo RARE, and dual echo GRASE brain scans from a large sample of MS patients. Using a 1.5 Tesla scanner, fast-FLAIR, dual echo RARE, and dual echo GRASE scans (24 axial, 5-mm thick contiguous interleaved slices) of the brain were obtained from 50 MS patients. Total lesion loads (TLL) were assessed twice using a semi-automated local thresholding segmentation technique by the same rater from the scans obtained with the three techniques. Mean TLL were 20.3 mL for fast-FLAIR, 16.6 mL for RARE, and 17.6 mL for GRASE sequences. Mean TLL detected by the three techniques were significantly heterogeneous (p < 0.001); at post-hoc analysis, the mean lesion volume detected on fast-FLAIR images was significantly higher than that on both RARE and GRASE images (p < 0.001) and the mean TLL on GRASE scans was significantly higher than that on RARE scans (p = 0.001). The mean values of intra-observer coefficient of variation for TLL measurements were similar for the three techniques (2.69% for fast-FLAIR, 2.33% for RARE, and 2.65% for GRASE). Our results confirm that fast-FLAIR sequences detect higher lesion volumes than those detected by other magnetic resonance imaging (MRI) sequences with shorter acquisition times. However, the reproducibility of TLL measurements is comparable among fast-FLAIR, RARE, and GRASE. This suggests that when assessing MS disease burden with MRI, the choice of the pulse sequence to be used should be dictated by the clinical setting.
Insights
Fast-FLAIR MRI sequences detect larger multiple sclerosis (MS) lesion volumes than RARE and GRASE. However, all three MRI techniques offer similar reproducibility for lesion load measurements in MS patients.
Area of Science:
- Neurology
- Radiology
- Medical Imaging
Background:
- Multiple Sclerosis (MS) diagnosis and monitoring rely on Magnetic Resonance Imaging (MRI) to quantify lesion burden.
- Different MRI pulse sequences, including fast-FLAIR, RARE, and GRASE, are used, but their comparative effectiveness in lesion volume assessment is debated.
- Previous studies often involved small patient cohorts, necessitating larger-scale investigations.
Purpose of the Study:
- To compare lesion volumes and intra-rater reproducibility of measurements using fast-FLAIR, dual echo RARE, and dual echo GRASE sequences in a large sample of MS patients.
- To evaluate the impact of different MRI pulse sequences on the assessment of total lesion load (TLL) in multiple sclerosis.
Main Methods:
- Fifty patients with MS underwent brain MRI using a 1.5 Tesla scanner, acquiring fast-FLAIR, dual echo RARE, and dual echo GRASE sequences.
- Total lesion loads (TLL) were measured twice by the same rater using a semi-automated local thresholding segmentation technique for each sequence.
- Intra-observer reproducibility was assessed by calculating the coefficient of variation for TLL measurements.
Main Results:
- Mean TLL varied significantly across sequences: 20.3 mL (fast-FLAIR), 16.6 mL (RARE), and 17.6 mL (GRASE) (p < 0.001).
- Fast-FLAIR detected significantly higher lesion volumes compared to both RARE (p < 0.001) and GRASE (p < 0.001).
- Mean TLL on GRASE scans was significantly higher than on RARE scans (p = 0.001). Intra-observer variability was comparable across all techniques (2.33%–2.69%).
Conclusions:
- Fast-FLAIR sequences identify larger lesion volumes in MS patients compared to RARE and GRASE sequences.
- Despite volume differences, the reproducibility of TLL measurements is similar across fast-FLAIR, RARE, and GRASE.
- The choice of MRI pulse sequence for assessing MS disease burden should be guided by clinical context and imaging time constraints.