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Bone densitometry.

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Bone and Bones↗

Densitometry of single-emulsion film.

The measured optical density of single-emulsion films depends on the film orientation. The orientation of the emulsion influences the amount of scattered light entering the detector. It is suggested that this measurement be done with the emulsion side facing the light detector.

Absorptiometry, Photon↗

Cross-sectional study of osteopenia with quantitative MR imaging and bone densitometry.

PURPOSE: 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. MATERIALS AND 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. CONCLUSION: Cancellous bone marrow R2' measured in the proximal femur provides information, which, with BMD, improves prediction of vertebral fracture status.

Absorptiometry, Photon↗

Cortical bone dynamics, strength, and densitometry after induction of emphysema in hamsters.

Recent evidence suggests that patients suffering from chronic obstructive pulmonary disease are also at an increased risk of developing osteoporosis. The pathophysiological mechanism(s) linking these progressive diseases is unknown. The goal of this investigation was to determine whether there were alterations in bone mineral density and content, cortical bone structure and strength, and indexes of bone formation and resorption in the elastase-induced emphysematous hamster. At 3 wk after induction of emphysema, the femoral bone mineral content was 8% less (P = 0.026) and the femoral fracture strength was 6% less (P = 0.032) in the emphysematous hamster than in controls. The cortical area was 8.4% less (P = 0.013) and the periosteal mineral appositional rate was 27% less (P = 0.05) than in controls. Additionally, the endocortical eroded surface in the emphysematous group was about twice that in the control group (P = 0.003). Differences in some indexes of bone formation and resorption, paralleled by differences in bone structure and strength, were observed 3 wk after induction of emphysema. These differences in skeletal metabolism and strength may help explain some of the skeletal changes associated with chronic obstructive pulmonary disease in humans.

Animals↗