title: Cross-sectional study of osteopenia with quantitative MR imaging and bone densitometry.
abstract: OBJECTIVE
  To evaluation the cancellous bone-induced intravoxel spin dephasing rate (R2') and its relationship to bone mineral density and marrow fat and to examine these parameters as predictors of vertebral fracture status.
  
  
  METHODS
  R2' and R2, the rate constants for reversible and irreversible spin dephasing, and marrow fat fraction were measured in the lumbar vertebrae and proximal femur. One hundred thirty-nine subjects (mean age, 62.4 years +/- 11.4 [SD]; 33 men, 106 women) had spinal dual-energy x-ray absorptiometric bone mineral density (BMD) T scores ranging from +3 to -5. R2', BMD, and bone marrow composition as determinants of vertebral fracture status were examined.
  
  
  RESULTS
  Strongest single predictors of fracture status for BMD and R2' were the Ward triangle (r(2) = 0.48) and trochanter (r(2) = 0.37), respectively. Combined, the two parameters and sites increased fracture prediction (r(2) = 0. 62), whereas the combination of multiple BMD sites did not. Multivariate regression involving marrow fat fraction further improved fracture status prediction. R2' was correlated with BMD at all sites, although slopes differed by a factor of up to 2.5, which reflected differences in trabecular orientation relative to the static field. R2, the true transverse relaxation rate, was negatively correlated with marrow fat fraction. A non-age-related increase in marrow fat fraction in osteoporosis parallels earlier findings in animal models.
  
  
  CONCLUSIONS
  Cancellous bone marrow R2' measured in the proximal femur provides information, which, with BMD, improves prediction of vertebral fracture status.
authors.affiliation: Department of Radiology, University of Pennsylvania Medical Center, 3400 Spruce St, 1 Founders, Philadelphia, PA 19104, USA. wehrli@oasis.rad.upenn.edu
authors.forename: F W
authors.initials: FW
authors.lastname: Wehrli
authors.forename: J A
authors.initials: JA
authors.lastname: Hopkins
authors.forename: S N
authors.initials: SN
authors.lastname: Hwang
authors.forename: H K
authors.initials: HK
authors.lastname: Song
authors.forename: P J
authors.initials: PJ
authors.lastname: Snyder
authors.forename: J G
authors.initials: JG
authors.lastname: Haddad
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015519:Bone Density; D001851:Bone Diseases, Metabolic / Q000175:diagnosis*; D001853:Bone Marrow / Q000473:pathology; D003430:Cross-Sectional Studies; D005260:Female; D005269:Femur / Q000473:pathology; D006801:Humans; D008159:Lumbar Vertebrae / Q000473:pathology; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D015663:Osteoporosis, Postmenopausal / Q000150:complications / Q000175:diagnosis; D016103:Spinal Fractures / Q000175:diagnosis / Q000209:etiology