DO DIURNAL CHANGES IN LOADING AFFECT THE INTERPRETATION OF MRI SCANS OF THE LUMBAR SPINE

We tested the hypothesis that the visual interpretation of magnetic re sonance imaging (MRI) scans of the asymptomatic lumbar spine are affec ted by diurnal changes in fluid exchange in the intervertebral discs. Ten male subjects carried a 20-kg backpack in the intervening 3-h peri od between two MRI scans of the lumbar spine. After the subjects arriv ed at the MRI center (within 45 min of awakening), they lay on a bed f or 45 min. The first set of MRI scans were obtained. Each subject was then fitted with a 20-kg backpack. After they walked for 3 h, the pack was removed, and a second set of MRI scans were obtained immediately. The sets of MRI scans were reviewed by three radiologists: none of th e three radiologists found differences in the interpretation of the MR I scans. On the basis of these results, diurnal changes in fluid excha nge in the asymptomatic intervertebral disc (exaggerated in our case b y the backpack) are undetectable by visual reading of MRI scans.