Quantitation of T2′ anisotropic effects on magnetic resonance bone mineral density measurement

✍ Scribed by Dmitriy A. Yablonskiy; William R. Reinus; Helmut Stark; E. Mark Haacke

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 883 KB
• Volume: 37
• Category: Article
• ISSN: 0740-3194
• DOI: 10.1002/mrm.1910370213

✦ Synopsis

Abstract

In this paper, the authors quantitate the anisotropy of susceptibility effects in an uniaxial trabecular bone model and show its relevance to clinical MR bone mineral density measurements. A physical model is described that quantitates the anisotropic MR behavior of uniaxial trabecular bone. To test the model, a phantom of parallel polyethylene filaments was scanned every 15° between 0° and 90° with respect to the system's main magnetic field (B~0~). The distal radial metaphysis of a healthy female volunteer was scanned in orthogonal projections. The signal from each phantom image and each radial image was separated in a pixel‐wise fashion into R~2~ and R~2~′ maps. As predicted, R~2~′ relaxation showed anisotropic behavior and changed according to sin^2^ (ϕ), confirming that columnar structures parallel with B~0~ will cause no MR susceptibility effects. Scans of the distal radius showed that R~2~′ relaxation was twice as great with the forearm perpendicular to B~0~ as when it was parallel to it, demonstrating different contributions from struts and columns. For both phantom and radial bone scans, R~2~ relaxation was isotropic and did not change with object orientation.