MEASURING DIFFUSION OF SOLUTES INTO INTERVERTEBRAL DISKS WITH MR-IMAGING AND PARAMAGNETIC CONTRAST-MEDIUM

BACKGROUND AND PURPOSE: Experimental studies have shown that solutes d iffuse more slowly into degenerated intervertebral disks than into nor mal disks. A noninvasive clinical study of diffusion in intervertebral disks is not generally available. Our purpose was to evaluate contras t-enhanced MR images to study diffusion in normal and degenerated lumb ar intervertebral disks. METHODS: The change in signal intensity (as a proportion of baseline signal intensity) was calculated in lumbar int ervertebral disks on MR images obtained before and after injection of intravenous contrast medium in 15 patients with low back pain. The int ervertebral disks were classified as normal or degenerated on the basi s of the MR appearance. Postoperative disks and degenerative intervert ebral disks with a ''high-intensity zone'' were excluded. The changes in signal intensity as a proportion of baseline signal intensity were compared in degenerated disks and normal disks and the differences tes ted for statistical significance. RESULTS: After intravenous administr ation of a gadolinium complex, signal intensity in normal intervertebr al disks increased an average of 36% of baseline. In intervertebral di sks,vith signs of degeneration, it increased an average of 21% of base line. The difference was significant. CONCLUSION: The study shows that diffusion into normal human lumbar intervertebral disks can be evalua ted with MR imaging combined,vith intravenous contrast medium. With su itable MR techniques, the relationship between diffusion and disk dege neration, and the effect of trauma, drugs, and nutrition on disk degen eration can be studied noninvasively.