MRI's in MS

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This paper discusses the question which has plagued many on the

board. Are MRI's useful?. The answer is that T2 lesion changes

greater than 0.65 ml in volume (size) are significant and not due to

technical error.

A

Mult Scler. 2004 Aug;10(4):402-6.

Has your patient's multiple sclerosis lesion burden or brain atrophy

actually changed?

Wei X, Guttmann CR, Warfield SK, Eliasziw M, JR.

Seaman Family MR Research Center, Departments of Radiology and

Clinical Neurosciences, University of Calgary, Calgary, AB, Canada.

Changes in mean magnetic resonance imaging (MRI)-derived

measurements between patient groups are often used to determine

outcomes in therapeutic trials and other longitudinal studies of

multiple sclerosis (MS). However, in day-to-day clinical practice

the changes within individual patients may also be of interest In

this paper, we estimated the measurement error of an automated brain

tissue quantification algorithm and determined the thresholds for

statistically significant change of MRI-derived T2 lesion volume and

brain atrophy in individual patients. Twenty patients with MS were

scanned twice within 30 min. Brain tissue volumes were measured

using the computer algorithm. Brain atrophy was estimated by

calculation of brain parenchymal fraction. The threshold of change

between repeated scans that represented statistically significant

change beyond measurement error with 95% certainty was 0.65 mL for

T2 lesion burden and 0.0056 for brain parenchymal fraction. Changes

in lesion burden and brain atrophy below these thresholds can be

safely (with 95% certainty) explained by measurement variability

alone. These values provide clinical neurologists with a useful

reference to interpret MRI-derived measures in individual patients.