Interscanner variation in brain MRI lesion load measurements in MS: Implications for clinical trials

Abstract

We evaluated the effect of interscanner variation on brain MRI-measured lesion volumes and measurement reproducibility in MS. Twenty clinically definite MS patients were each scanned on two or three scanners (a total of 14 scanners were used). In addition, a formalin-fixed MS brain was studied on eight scanners from different manufacturers and with different field strengths. For the formalin-fixed MS brain, on each machine we obtained two scans with slice thicknesses of 5 and 3 mm. Only 5-mm-thick slices were obtained from patients. The lesion volume present on each scan was evaluated three times by a single observer in random order, using a local thresholding technique. In two groups of eight patients scanned on machines with different field strengths, the mean lesion volumes present on scans obtained at 1.5 T were significantly higher than those measured on scans obtained with machines operating at 0.5 and 1.0 T (p < 0.01). When a single observer repeatedly evaluated the same scan, a median introbserver agreement of 98.7% (95% CI, 97.9 to 99.1) was achieved. However, when the observer evaluated the scans from different MRI scanners, the agreement (an interscanner agreement) fell to 91.1% (CI, 90.2 to 94.1). When only scanners operating at 1.5 T were considered, the median interscanner agreement was 96.7% (CI, 95 to 97.5). Also, for the formalin-fixed MS brain, the intraobserver agreements obtained with both slice thicknesses were significantly higher than the corresponding interscanner agreements. The interscanner agreement, but not the intraobserver agreement, obtained with a slice thickness of 3 mm was higher than that obtained with a slice thickness of 5 mm. Our results indicate that lesion volume measurements in MS are influenced significantly by the use of different MR scanners and that a patient included in a serial study should be always scanned with the same MR machine using 3-mm thick slices.

Predicting Outcome after Pediatric Traumatic Brain Injury by Early Magnetic Resonance Imaging Lesion Location and Volume

“…75,76 Interscanner agreement for quantitative assessments of FLAIR lesion volumes, using quantitative semiautomated thresholding techniques similar to those employed in our study, was 96.7% (95% CI, 95-97.5) for scanners operating at 1.5T field strength and 91.1% (95% CI, 90.2-94.1) for scanners of different field strengths. 77 The effect of such variances on cross-sectional studies such as the one presented here is likely to be small. Every effort was made to assure unbiased measurements; however, lesion thresholds were set manually to detect the subtlest lesion present; thus, there is some subjective interpretations inherent in the thresholding method used for quantification.…”

A Longitudinal Study of Abnormalities on MRI and Disability from Multiple Sclerosis

“…Although there was a change in scanner and slice thickness during the study, this had little influence 40,41 on the large increases seen in the lesion volumes, which included an increase in the median volume by a factor of 11 over a 14-year period. Furthermore, none of these patients were treated with disease-modifying drugs during the first 10 years; three patients received interferon beta after year 10.…”

High field MRI in the diagnosis of multiple sclerosis: high field–high yield?

“…Two studies showed significantly higher lesion load measurements at 1.5 T when compared to lower field strengths especially in the infratentorial region [21,22], however, without any implications on this diagnosis of MS according to the Poser criteria [24]. These results could not be confirmed by the following study including a larger cohort of 132 patients with suspected or definite MS [23].…”

“…The first studies comparing magnetic field strengths of 0.5 and 1.5 T can be considered as inconclusive [21][22][23]. Two studies showed significantly higher lesion load measurements at 1.5 T when compared to lower field strengths especially in the infratentorial region [21,22], however, without any implications on this diagnosis of MS according to the Poser criteria [24].…”