T2- and diffusion-maps reveal diurnal changes of intervertebral disc composition: an in vivo MRI study at 1.5 Tesla

To investigate the lumbar intervertebral discs (IVDs) by MRI in the morning and evening after a diurnal load cycle. Changes in MR characteristics (T2-weighted imaging, T2- and apparent diffusion coefficient [ADC] -mapping) during the course of the day were visualized and analyzed visually and quantitatively. The length of the lumbar spine was measured in between the lower anterior edge of Th12 and the upper anterior edge of S1. T2 changes and diffusion characteristics of the vertebral disc tissue were investigated with a higher spatial resolution than in former studies.

In six males, lumbar IVDs were investigated in the morning and evening. T2-maps and ADC maps were generated. Data were analyzed by selecting regions of interest (ROI) in the annulus fibrosus (AF), nucleus pulposus (NP), and an intermediate area.

From morning to evening, T2 decreased in the center of the NP (-7.9%; P = 0.001) and the intermediate voxels (-6.4%; P < 0.0005). T2 increased (8.5%; P < 0.048) in the AF. ADC decreased in the AF (-5.2%; P = 0.007) and the intermediate ROIs (-2.2%; P = 0.004). There was no significant change of ADC in the NP (-1.6%; P = 0.242).

T2 and diffusion (ADC) changes of IVDs in humans were investigated with a spatial differentiation between NP and AF. T2 and ADC turned out to be sensitive parameters in investigating changes in the MR characteristics of the IVD matrix during a day. Highly resolved MR imaging and parameter mapping is expected to be an interesting tool in characterizing structural changes in the vertebral disc architecture in an early stage of degeneration.