A modified quantitative MRI analysis method to identify the direction of shift in lumbar disc hydration over the axial MRI in response to side-bending.

Abstract

The direction of loading to disc tissue in response to postural changes has been investigated. However, the reported original method may not adequately represent the disc hydration profile. To investigate the reliability of a modified method to measure the direction of shift of disc hydration in response to side-bending. Each lumbar disc of 10 healthy subjects was scanned with T2-weighted magnetic resonance imaging in supine (neutral) position and left side-bending position in lying. A mid-point over the pixel intensity profile line was obtained. The differences in mid-point values between the neutral and side-bending positions were plotted in each direction on a X-Y coordinates plane and the angle (θ) of each plotted point from the X-axis was calculated. The Intraclass Correlation Coefficients (ICC) of the mid-point values during left side-bending along the sagittal and coronal directions of the disc ranged between 0.72-0.98 and 0.80-0.96, respectively. It was estimated that calculating θ values twice yielded an ICC of 0.8 at each disc level. The modified method was reliable in capturing gross disc hydration profiles. The direction of shift in disc hydration in response to side-bending can be identified using averaged values of θ that was calculated twice.