title: Magnetic resonance imaging of the calcaneus: preliminary assessment of trabecular bone-dependent regional variations in marrow relaxation time compared with dual X-ray absorptiometry.
abstract: OBJECTIVE
  Marrow transverse relaxation time (T2*) in magnetic resonance (MR) imaging may be related to the density and structure of the surrounding trabecular network. We investigated regional variations of T2* in the human calcaneus and compared the findings with bone mineral density (BMD), as measured by dual X-ray absorpiometry (DXA). Short- and long-term precisions were evaluated first to determine whether MR imaging would be useful for the clinical assessment of disease status and progression in osteoporosis.
  
  
  METHODS
  Gradient-recalled echo MR images of the calcaneus were acquired at 1.5 T from six volunteers. Measurements of T2* were compared with BMD and (for one volunteer) conventional radiography.
  
  
  RESULTS
  T2* values showed significant regional variation; they typically were shortest in the superior region of the calcaneus. There was a linear correlation between MR and DXA measurements (r = .66 for 1/T2* versus BMD). Differences in T2* attributable to variations in analysis region-of-interest placement were not significant for five of the six volunteers. Sagittal MR images had short- and long-term precision errors of 4.2% and 3.3%, respectively. For DXA, the precision was 1.3% (coefficient of variation).
  
  
  CONCLUSIONS
  MR imaging may be useful for trabecular bone assessment in the calcaneus. However, given the large regional variations in bone density and structure, the choice of an ROI is likely to play a major role in the accuracy, precision, and overall clinical efficacy of T2* measurements.
authors.affiliation: Department of Radiology, Scientific institute CSS, San Giovanni Rotondo (FG), Italy.
authors.forename: G
authors.initials: G
authors.lastname: Guglielmi
authors.forename: K
authors.initials: K
authors.lastname: Selby
authors.forename: B A
authors.initials: BA
authors.lastname: Blunt
authors.forename: M
authors.initials: M
authors.lastname: Jergas
authors.forename: D C
authors.initials: DC
authors.lastname: Newitt
authors.forename: H K
authors.initials: HK
authors.lastname: Genant
authors.forename: S
authors.initials: S
authors.lastname: Majumdar
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D015519:Bone Density; D001853:Bone Marrow / Q000033:anatomy & histology*; D002111:Calcaneus / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D012016:Reference Values