Assessment of lumbar disc herniaton using fractional anisotropy in diffusion tensor imaging along with conventional T2-weighted imaging.

Abstract

To assess the usefulness of diffusion tensor imaging and its fractional anisotropy map along with conventional T2-weighted imaging in evaluating the anisotropic water diffusion variations of annulus fibres involved in herniation disc pathology. Seventy-five patients with previous medical ethics committee approval and informed consent experiencing low back pain were selected for this prospective randomised blinded trial. Lumbar disc fractional anisotropy maps were obtained acquiring diffusion tensor sequences on a 3T machine. The matrix of nucleus pulposus and structures of annulus fibres were analysed using fractional anisotropy textural features to highlight any presence of lumbar disc herniation. Observer variability and reliability between two neuroradiologists were evaluated. The χ2 test, two-tailed t test and linear regression analysis were used to focus differences in patients' demographic data and magnetic resonance imaging findings. Annular fissures with extrusions were identified using diffusion tensor imaging in 10 out of 17 discs (study group) previously assessed as bulging discs using conventional magnetic resonance imaging. Eighteen extrusions out of 39 (study group) disc levels were identified on diffusion tensor imaging compared to eight extrusions highlighted on T2-weighted imaging (P < 0.01). All eight (study group) disc extrusions evaluated on T2-weighted imaging showed annular fissures on diffusion tensor imaging. Seven out of 14 (study group) protrusions highlighted on T2-weighted imaging had no annular fissures on diffusion tensor imaging; thirty-six disc levels in the control group had no evidence of annular fissures on diffusion tensor imaging (P > 0.01). The addition of diffusion tensor imaging sequences and fractional anisotropy mapping to a conventional magnetic resonance imaging protocol could be useful in detecting annular fissures and lumbar disc herniation.