Apparent diffusion coefficient and T2* mapping on 3T MRI in normal and degenerative lumbar intervertebral discs

Abstract

PurposeTo assess the utility of diffusion-weighted imaging (DWI) with apparent diffusion coefficient (ADC) maps and T2* mapping in quantitative analysis of nucleus pulposus (NP) and annulus fibrosus (AF) of lumbar intervertebral discs with its correlation with modified Pfirrmann grading (MPG) for lumbar degenerative disc disease (LDDD).Material and methodsOne hundred subjects (20-74 years of age) underwent T2-weighted, DWI with ADC and T2* magnetic resonance imaging. MPG was applied to L3-L4, L4-L5, and L5-S1 discs, and ADC and T2* values of NP and AF were calculated in the mid-sagittal plane by segmenting each disc into 5 regions of interest (ROI) (NP-3, AF-2). Mean ADC and T2* values, their correlation, and cut-offs among different grades were calculated at different ROIs across different levels.ResultsOut of total 300 discs analysed; 68 were normal (grade I) discs and 232 were degenerated (grade II to VIII) discs, based on MPG. T2* and ADC values in NP, AF, and the entire disc were significantly lower in degenerated discs than in normal discs. There was significant (p < 0.001) negative correlation between ADC and T2* values with MPG. ADC and T2* cut-off values were statistically significant across grades, with area under the curve (AUC) values in moderate to high accuracy range (0.8 to > 0.9) for assessing the degree of LDDD.ConclusionsT2* and ADC value-based grade scales are highly accurate in evaluating the degree of disc degeneration with a high degree of objectivity in comparison to visual assessment-based MPG. Reduced ADC and T2* values of NP could serve as markers of early LDDD.

Unveiling interactions between intervertebral disc morphologies and mechanical behavior through personalized finite element modeling

“…Another limitation of our study pertains to the NP-AF boundary transition zone (TZ), which, despite its relevance introduced in the Methods and noted by Ruiz et al (2013) , is difficult to define precisely in terms of material properties and size. Yet, the delineation of this region enhances the realism of the IVD model by providing a gradual material property transition from the NP to the AF, as opposed to an abrupt shift, as suggested by measurements of gradual shifts in cell phenotypes ( Bruehlmann et al, 2002 ), MRI signal ( Kapoor et al, 2023 ), and fiber structure ( Disney et al, 2023 ). Arguably, this region’s local properties and exact size are difficult to assess.…”

“…This zone, as defined in our FE meshes, emerged out of a need for computational stability to ensure the FE mesh convergence and cope with the negative effects of weak discontinuities between the nucleus pulposus and the annulus fibrosus elements ( Ruiz et al, 2013 ). Interestingly, though, a transition between the nucleus and the annulus exists, as revealed by several quantitative MRI, synchrotron imaging, cell phenotypes, and structural and composition measurements through the IVD ( Marchand and Ahmed, 1990 ; Bruehlmann et al, 2002 ; Disney et al, 2023 ; Kapoor et al, 2023 ). Hence, the definition of this region in the FEM results in a more realistic description of the IVD, in contrast to an abrupt change of material properties from the NP to the AF.…”