Comparison of MRI T1, T2, and T2* mapping with histology for assessment of intervertebral disc degeneration in an ovine model

Abstract

An easy, reliable, and time-efficient standardized approach for assessing lumbar intervertebral disc (IVD) degeneration with relaxation times measurements in pre-clinical and clinical studies is lacking. This prospective study aims to determine the most appropriate method for lumbar IVD degeneration (IDD) assessment in sheep by comparing three quantitative MRI sequences (variable-flip-angle T1 mapping, and multi-echo T2 and T2* mapping), correlating them with Pfirrmann grading and histology. Strong intra- and interrater agreements were found for Nucleus pulposus (NP) regions-of-interest (ROI). T1, T2, and T2* mapping correlated with Pfirrmann grading and histological scoring (p < 0.05) except for the most ventral rectangular ROI on T2 maps. Correlations were excellent for all of the T1 ROIs and the T2* NP ROIs. Highly significant differences in T1 values were found between all Pfirrmann grades except between grades I/II and between grades III/IV. Significant differences were identified in the T2 and the T2* values between all grades except between grades I/III. T1, T2, and T2* relaxation times measurements of the NP are an accurate and time-efficient tool to assess lumbar IDD in sheep. Variable-flip-angle T1 mapping may be further considered as a valuable method to investigate IDD and to assess the efficacy of regenerative treatments in longitudinal studies.

T1ρ, T2 and T2* mapping of lumbar intervertebral disc degeneration: a comparison study

“…Our present finding is consistent with previous studies that T1ρ, T2 and T2* relaxation times of NP decreased linearly with increasing Pfirrmann grades [ 11 – 13 , 21 – 23 ]. Histologically, T1ρ is strong affinity with proteoglycan content in the disc matrix [ 13 ], T2 relaxation time has strong positive correlations with water and glycosaminoglycans content [ 19 ], and T2* relaxation time is highly correlated with glycosaminoglycan content [ 20 ].…”

“…T1ρ mapping probes slow interactions between extracellular matrix macromolecules and bulk water by applying a “spin lock” pulse [ 19 ], while T2 and T2* relaxation times reflect the content and spatial distribution of macromolecule and water [ 19 , 20 ]. It has been demonstrated that T1ρ, T2 and T2* relaxation times are associated with glycosaminoglycan and water content [ 13 , 19 , 20 ], Pfirrmann grading [ 11 – 13 , 21 – 23 ], histological scores [ 17 , 20 , 21 ] and clinical symptom [ 24 , 25 ] of IVDD. T1ρ is reported to be strong affinity with proteoglycan content in the disc matrix [ 13 ], and its main relaxation induced by chemical exchange [ 14 ].…”

Quantitative Analysis of Electrical Current Effect on Magnetic Resonance Image Tissue Intensity

“…The paramagnetic effect of Gd in contrast enhancement of MRI images is by decreasing the relaxation times of T2 and T1 on protons. With the use of iron oxide, the dephasing rate of T2 * increases as well as T2 and T1 in the protons [7,8,9].…”

Variable flip angle T1 mapping and multi‐echo T2 and T2* mapping magnetic resonance imaging sequences allow quantitative assessment of canine lumbar disc degeneration

“…14 As for humans and sheep, the T2 relaxation time decreased with IVD degeneration. 14,15 In parallel, one study established the T2 relaxation times for healthy NP in twelve beagles. 16 On the other hand, T2* mapping evaluates the mobility of the water molecules and the spatial architecture of the macromolecules in the IVD.…”

“…T2 mapping has been studied in various animal models but, in the canine model, only one experimental study to date has assessed canine IVD degeneration using T2 mapping after induction of IVD degeneration in NC dogs 14 . As for humans and sheep, the T2 relaxation time decreased with IVD degeneration 14,15 . In parallel, one study established the T2 relaxation times for healthy NP in twelve beagles 16 .…”