Non-Gaussian Diffusion-Weighted Imaging for Assessing Diurnal Changes in Intervertebral Disc Microstructure

Purpose: To investigate the use of non-Gaussian diffusion-weighted imaging (q-space imaging [QSI]) to estimate diurnal changes in intervertebral disc (IVD) microstructure. Materials and Methods: IVDs of 15 male subjects (mean age, 27.3 years; mean body mass index, 22.50 kg/m(2)) were investigated once in the morning, less than 30 min after rising, and a second time in the evening after at least 10 h of normal physical activity, using 3 Tesla (T) MR imaging. T2 mapping and QSI data values (apparent diffusion coefficient [ADC], root mean square displacement [RMSD], and apparent kurtosis coefficient [AKC]) were calculated and compared between the morning and evening imaging sessions. Results: The T2, ADC, and RMSD values showed a significant decrease in the evening (175.8 +/- 49.5 ms, 1.56 +/- 0.32 10(-3) mm(2)/s and 40.0 +/- 3.0 mu m, respectively; P < 0.05 for all values; paired t-test), when compared with the morning values (226.5 +/- 83.8 ms, 1.69 +/- 0.29 10(-3) mm(2)/s and 45.2 +/- 2.9 mm, respectively). The AKC value showed a significant increase in the evening (0.67 +/- 0.08), when compared with the morning value (0.58 +/- 0.04; P < 0.05). Conclusion: The RMSD and AKC values obtained from QSI analysis may be biomarkers for IVD diurnal microstructural changes.