Apparent diffusion coefficients and T2 relaxation time measurements to evaluate disc degeneration - A quantitative MR study of young patients with previous vertebral fracture

Purpose: To assess the suitability of apparent diffusion coefficient (ADC) measurements to evaluate degeneration processes of the vertebral disc and t o compare the results with T2 relaxation time measurements in both degenera ted and normal intervertebral discs. Material and Methods: Fourteen young patients (8.8-20.8 years old) who had had a vertebral compression fracture at least 1 year earlier, underwent MR studies with diffusion imaging in three orthogonal directions and T2 relaxa tion time measurements. ADC values and T2 relaxation times of both degenera ted and normal intervertebral discs were compared to the values of 20 healt hy young asymptomatic control subjects. Results: In the degenerated discs of patients, the ADC(x) and ADC(y) values were decreased compared to earlier determined values of healthy controls. ADC values in the z-direction in degenerated discs did not differ significa ntly from the values of controls. T2 relaxation times were shorter in the d egenerated discs of patients compared to the values of controls. The greate st changes in both these values were observed in degenerated discs followed by discs with normal signal intensity adjacent to primary trauma area and secondary trauma area. Conclusion: We suggest that decreased ADC values reflect the lost integrity of the intervertebral disc. ADC measurements at MR may prove sensitive dep icting of early degenerative changes in vertebral discs.