Purpose: To assess regional variations of T1rho (T1ρ) and T2 rates within lumbar intervertebral discs and to evaluate the correlation of T1ρ and T2 rates in different disc regions with Pfirrmann grades of degeneration and morphologic changes.
Materials and methods: We retrospectively evaluated 105 lumbar discs in 22 subjects who were examined at 3.0-T MRI. T1ρ and T2 relaxation rates (1/T1ρ and 1/T2) were measured in five segmented regions of discs: anterior annulus fibrosus (AF), anterior junction, nucleus pulposus (NP), posterior junction, and posterior AF. Disc degeneration was graded using 5-level Pfirrmann grading system and morphologic change was categorized into five groups (normal, bulging, annular fissure, protrusion, and extrusion). Regional differences of T1ρ and T2 rates and correlation with degeneration and morphologic changes were statistically analyzed.
Results: Most of the five segmented regions showed statistically different T1ρ and T2 rates from each other. T1ρ and T2 relaxation rates were positively associated with Pfirrmann grades of degeneration and morphologic changes, with different strength of relation in each region. T2 rates in the posterior junction showed the strongest correlation with degeneration (r=0.810) and T2 rates in the anterior junction showed the highest association with morphologic changes (r=0.621).
Conclusions: Regional variations of T1ρ and T2 rates within discs and different strength of relation with degeneration and morphologic changes should be taken into account when evaluating lumbar discs.
Keywords: Disc degeneration; Intervertebral disc; Magnetic resonance imaging; T1rho; T2.
Copyright © 2016 Elsevier Inc. All rights reserved.