Abstract
Introduction Fluid dynamics in the intervertebral disc plays an important role in the overall mechanical function as well as nutritional supply for both the annulus fibrosis (AF) and the nucleus pulposus (NP). The apparent diffusion coefficient of water in intervertebral discs has been suggested to be related to the matrix composition as well as the structural integrity of the disc.
Methods Lesions were created in two intervertebral lumbar discs in 18 in-bred Sprague Dawley rats (approved by Animal Ethics Committee) using a 14G hypodermic syringe to induce degenerative change as described by Sobajima et al (1). Regenerative treatment involved the injection of multipotent stem cells isolated from the olfactory mucosa. These cells were injected either at the time of creation of the lesion or six weeks after creation of the lesion.
MRI experiments were undertaken at 25.0 ± 0.1 °C on a Bruker Avance NMR spectrometer (Bruker Bio-Spin, Rheinstetten, Germany) using a 7.0T vertical bore magnet system, equipped with a 1.1 T m-1 (110 G cm-1) gradient set and 15 mm ‘birdcage’ RF resonator. Specimens for testing were immersed in physiological saline inside a 15 mm NMR. Both multi echo and diffusion weighted images were acquired with a recycle time TR = 2 s and 8 averages using a 0.7 mm slice thickness, a field of view (FOV) of ca. 15 × 15 mm and a 128 × 128 matrix. For multi echo experiments the echo time was 5 ms with 64 echoes and for DT imaging a diffusion gradient duration δ = 2 ms and diffusion delay Δ = 12 ms. The diffusion tensor was calculated from the seven requisite diffusion-weighted images using in-house Matlab® code (The Mathworks, Natick, MA) written for the purpose.
Results Preliminary results of the multi echo images indicate that intervertebral disc degradation results in observable differences in the T2 of the NP ((mean/SD (ms)) control disc (63.2/3.4), untreated (49.5/1.4) and treated (49.7/3.4)). Diffusion tensor results show isotropic diffusion in the NP with anisotropic diffusion in the AF and observable differences in magnitude.
Discussion The use of high resolution MRI has been shown to provide a useful tool for quantifying the effects of regenerative treatments for degenerative disc disease.
The abstracts were prepared by Assoc Prof Bruce McPhee. Correspondence should be addressed to him at the Division of Orthopaedics, The University of Queensland, Clinical Sciences Building, Royal Brisbane Hospital, Herston, Brisbane, 4029, Australia.
Reference
1 Sobajima S, Kompel JF, Kim JS, et al. Spine2004; 30:15–24. Google Scholar
