Quantitative analysis of intervertebral disc structure

A reduction in signal intensity from the nucleus can be a feature of intervertebral disc disease. It has been established that T1 and T2 relaxation times of the nucleus decrease with age and that evidence of disc degeneration can be determined before classical clinical features are apparent. A robust multiple point algorithm has been developed which now enables proton density and T1 and T2 values to be computed for each pixel, providing images which are effectively spatial maps of these parameters. Such high resolution maps have provided quantitative data from volunteers, patients and cadavers. These studies have been carried out with specially constructed coils and the cadaveric information compared with cut sections. The spatial maps revealed detailed anatomic structures including the laminae of the annulus and relative levels of hydration. These levels, which are known to be related to the ability of the disc to withstand compressive loads, can now be measured in vivo. Analysis of the proton density and relaxation times in vivo has demonstrated that both water content and the chemical environment in the nucleus change during aging. The results are consistent with changes in the glycosaminoglycan content and fixed charged density measured by other chemical and physical techniques. Such detailed methods can be used to investigate the effects of aging and disease on disc structure and have enabled observations to be made of the effects of stress on the normal disc.