Digital assessment of MRI for lumbar disc desiccation. A comparison of digital versus subjective assessments and digital intensity profiles versus discogram and macroanatomic findings.

During magnetic resonance imaging, a vast amount of digital data on anatomic structures is translated into images, which are then assessed subjectively. The development of an objective, sensitive method to directly assess the digital data would have clear benefits, particularly for clinical research on disc degeneration. The study goals were to develop a method of digital assessment of disc desiccation and to compare digital signal intensity profiles with discographic patterns and macroanatomic findings. Proton density-weighted MRIs were obtained from 45 males (9-77 years) and digital analysis was done with a freely selectable region of interest facility. The adjacent cerebrospinal fluid (CSF) was used as a reference for disc signal-intensity scores, and the disc to CSF-intensity ratio provided "adjusted digital scores." The CSF-adjusted digital method yielded reproducible scores that correlated with the subjective assessments. However, the CSF-adjusted digital scores were more sensitive than the subjective assessments, identifying findings that otherwise were undetected in younger subjects. Additionally, 10 cadaveric spines were evaluated using MRI with T2 and proton density-weighted sequences, discography, and macroanatomic dissection. MRI disc-intensity profiles were determined along a midsagittal line drawn through the disc. The profile of the digital scores along this line was then compared with discograms and macroanatomic sections. In all cases of disc degeneration on discograms, changes were present in the intensity profile. Based on both the living subjects and the cadaveric specimens, the digital assessments and disc intensity profiles appear to demonstrate disc degeneration, particularly in early stages.