Inhomogeneity of rat vertebrae trabecular architecture by high-field 3D μ-magnetic resonance imaging and variable threshold image segmentation

Marcella Palombarini, Mirko Gombia, Paola Fantazzini, Roberto Giardino, Gianluca Giavaresi, Annapaola Parrilli, Franco Vittur, Genevieve Guillot

Research output: Contribution to journalArticle

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 x 20 x 20 μm3 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, EV) 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 EV = EV(T). Results: Quantitative 3D analysis of μ-MRI images revealed a higher connectivity in the peripheral regions (EV = -570 ± 70 mm-3) than in the central regions (EV = -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.

Original languageEnglish
Pages (from-to)825-833
Number of pages9
JournalJournal of Magnetic Resonance Imaging
Volume30
Issue number4
DOIs
Publication statusPublished - Oct 2009

Keywords

  • μ-MRI
  • Anisotropy
  • Bone architecture
  • Connectivity
  • Euler density
  • Euler number
  • Image segmentation
  • Rat vertebrae

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging

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