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Background Client‐owned dogs presenting clinically with intervertebral disc disease (IVDD) are a potential comparative animal model to help advance the understanding of disc degeneration and its treatment. To utilize dog patients as a model, noninvasive imaging techniques are needed that can characterize subtle and progressive changes in disc health in longitudinal and treatment efficacy studies. The purpose of this study was to assess the sensitivity of quantitative MRI techniques in detecting disc degeneration in client‐owned, nonchondrodystrophic‐breed dogs. Methods Thoracolumbar vertebral columns from the donated bodies of 15 dogs without a history of IVDD were imaged at 3T MRI. Quantitative MRI maps (T2, T2*, T1ρ, adiabatic T1ρ, adiabatic T2ρ, and ADC) were acquired axially for 10 discs (T11‐T12 to L7‐S1), and median values were measured in the nucleus pulposus and annulus fibrosus. Four disc health measures (Pfirrmann grade, histology score, water content, and glycosaminoglycan content) were evaluated for each disc. The quantitative MRI and disc health measures were compared using linear models, and partial correlations (Rpartial) were calculated. Results Most dogs had both relatively healthy and degenerated discs as assessed by Pfirrmann grade and histology score. Quantitative MRI values in relatively healthy discs varied greatly between dogs but were similar across disc levels. In the nucleus pulposus, T2 relaxation times were moderately correlated with Pfirrmann grade (Rpartial = −0.62; p < 0.0001), histology score (Rpartial = −0.63; p < 0.0001), and water content (Rpartial = +0.45; p < 0.0001), and weakly correlated with glycosaminoglycan content (Rpartial = +0.31; p = 0.0047). T2, T2*, T1ρ, adiabatic T1ρ, and adiabatic T2ρ had similar relationships to the disc health measures in the nucleus pulposus. No notable relationships were observed with ADC or in the annulus fibrosus. Conclusions Quantitative T2, T2*, T1ρ, adiabatic T1ρ, and adiabatic T2ρ relaxation time mapping techniques are similarly related to radiological and histological measures of disc health and water and glycosaminoglycan content in nonchondrodystrophic‐breed dogs. The purpose of this study was to assess the sensitivity of quantitative MRI techniques in detecting disc degeneration in client‐owned, nonchondrodystrophic‐breed dogs. Thoracolumbar vertebral columns from the donated bodies of 15 dogs without a history of IVDD were imaged ex vivo at 3T MRI, and quantitative MRI values of the discs were compared to radiological Pfirrmann grade, histology score, water content, and glycosaminoglycan content. We found that quantitative T2, T2*, T1ρ, adiabatic T1ρ, and adiabatic T2ρ relaxation time mapping techniques are similarly related to radiological and histological measures of disc health and water and glycosaminoglycan content.

Background Intervertebral disc (IVD) degeneration contributes significantly to chronic low back pain and represents a major clinical challenge. Quantitative MRI (qMRI) techniques offer the potential to assess biochemical and structural disc changes noninvasively, but its use has been slow to be incorporated into studies utilizing spontaneous large animal models. This study characterizes qMRI‐derived biomarkers of IVD degeneration across the lifespan in a clinically relevant ovine model. Methods Ex vivo thoracolumbar spine segments from 10 sheep (13–130 months old) were assessed using 3T MRI, including T2, T2*, T1ρ, adiabatic T1ρ, adiabatic T2ρ, and ADC mapping. Relaxation times were compared with Pfirrmann grade, disc height index, biomechanical testing, GAG/water content, and histological scores. Results T2 and T2* values in the nucleus pulposus (NP) were negatively correlated with age, Pfirrmann grade, and histological degeneration, and positively correlated with GAG and water content. T2 relaxation times in the annulus fibrosus (AF) were inversely related to biomechanical stiffness, whereas T2* relaxation times in the NP were positively associated. Strong inter‐metric correlations were observed between most qMRI measures, but aT1ρ and ADC showed more distinct profiles. Conclusion These findings support the sensitivity of qMRI in detecting regional and age‐related IVD changes and reinforce its utility for noninvasive disc assessment in translational models of degeneration. Quantitative MRI reveals age‐related degeneration of lumbar intervertebral discs. Axial T2 and T2* relaxation time maps from representative young (15‐month) and old (130‐month) sheep demonstrate substantially higher relaxation times in young discs, particularly within the nucleus pulposus, indicating a well‐hydrated and proteoglycan‐rich matrix. In contrast, older discs exhibit markedly reduced relaxation times consistent with dehydration and matrix degeneration. These imaging biomarkers highlight the sensitivity of T2 and T2* mapping for detecting age‐related changes in disc composition.