Abstract
Background
In vivo evaluation of IVD strains is crucial to better understand normal and pathological IVD mechanics, and to evaluate the effectiveness of treatments. This study aimed to 1) develop a novel in vivo technique based on 3T MRI and digital volume correlation (DVC) to measure strains within IVDs and 2) to use this technique to resolve 3D strains within IVDs of healthy volunteers during extension.
Methods
This study included 40 lumbar IVDs from eight healthy subjects. The optimal MR sequence to minimise DVC uncertainties was identified by scanning one subject with four different sequences: CISS, T1VIBE, T2SPACE, and T2TSE. To assess the repeatability of the strain measurements in spines with different anatomical and morphological variations four subjects were scanned with the optimal sequence, and uncertainties of the strain measurements were quantified. Additionally, to calculate 3D strains during extension, MRIs were acquired from six subjects in both the neutral position and after full extension.
Results
Measurement errors were lowest when using the T2TSE sequence (precision=0.33 ± 0.10%, accuracy=0.48 ± 0.11%). The largest average maximum tensile and shear strains were seen at the L2-L3 level in all volunteers (7.2 ± 1.5% and 6.8 ± 1.1%, respectively), while the L5-S1 level experienced the lowest average tensile and shear strains (3.5 ± 1.0% and 3.9 ± 0.7%, respectively).
Conclusion
The findings of this study establish clinical MRI-based DVC (MRI-DVC) as a new tool for in vivo strain measurement within human IVDs. MRI-DVC successfully provided internal strain distributions within IVDs and has great potential to be used for a wide range of clinical applications.
Conflict of interest: No conflicts of interest.
Source of funding: This work was supported by the EPSRC, New Investigator Award, EP/V029452/1.
