Inhomogeneity of rat vertebrae trabecular architecture by high-field 3D μ-magnetic resonance imaging and variable threshold image segmentation
✍ Scribed by Marcella Palombarini; Mirko Gombia; Paola Fantazzini; Roberto Giardino; Gianluca Giavaresi; Annapaola Parrilli; Franco Vittur; Genevieve Guillot
- Publisher
- John Wiley and Sons
- Year
- 2009
- Tongue
- English
- Weight
- 872 KB
- Volume
- 30
- Category
- Article
- ISSN
- 1053-1807
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✦ Synopsis
Abstract
Purpose
To analyze the 3D microarchitecture of rat lumbar vertebrae by micro‐magnetic resonance imaging (μ‐MRI).
Materials and Methods
μ‐MR images (20 × 20 × 20 μm^3^ apparent voxel size) were acquired with a three‐dimensional spin‐echo pulse sequence on four lumbar vertebrae of two rats. Apparent microarchitectural parameters like trabecular bone fraction (BV/TV), specific bone surface (BS/TV), mean intercept length (MIL), and Euler number per unit volume (Euler density, E~V~) were calculated using a novel semiquantitative variable threshold segmentation technique. The threshold value T* was obtained as a point of minimum or maximum of the function E~V~ = E~V~(T).
Results
Quantitative 3D analysis of μ‐MRI images revealed a higher connectivity in the peripheral regions (E~V~ = −570 ± 70 mm^−3^) than in the central regions (E~V~ = −130 ± 50 mm^−3^) of the analyzed rat lumbar vertebrae. Smaller intertrabecular cavities and larger bone volume fractions were observed in peripheral regions as compared to central ones (MIL = 0.18 ± 0.01 mm and 0.26 ± 0.01 mm; BV/TV = 34 ± 3% and 29 ± 3%, respectively). The quantitative 3D study of MIL showed a structural anisotropy of the trabeculae along the longitudinal axis seen on the images. The inhomogeneity of the bone architecture was validated by micro‐computed tomography (μ‐CT) images at the same spatial resolution.
Conclusion
3D high‐field μ‐MRI is a suitable technique for the assessment of bone quality in experimental animal models. J. Magn. Reson. Imaging 2009;30:825–833. © 2009 Wiley‐Liss, Inc.