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almost any part of the skeleton. X-rays at 2 energy levels are differentially impeded by bone and soft tissue; therefore, the type and amount of tissue scanned can be distinguished by use of DEXA. 1 By use of human protocols adapted according to the size
if height and weight be known . Arch Intern Med 1916 ; 17 : 863 – 871 . 59. Brommage R. Validation and calibration of DEXA body composition in mice . Am J Physiol Endocrinol Metab 2003 ; 285 : 454 – 459 . 60. Rozylowicz L Dobre M
be masked by a concurrent increase in body fat. A study 6 in humans found considerable loss of LBM despite maintenance of body weight. Tests that have been used to investigate LBM in elderly humans include regional CT, DEXA, urinary creatinine
Abstract
Objective—To compare bone mineral measurements obtained by use of dual-energy x-ray absorptiometry (DEXA), peripheral quantitative computed tomography (pQCT), and chemical-physical analyses and determine effects of age and femur size on values obtained for the various techniques.
Sample Population—Femurs obtained from 15 juvenile and 15 adult large-breed dogs.
Procedure—In each femur, 7 regions of interest were examined by use of DEXA to measure the bone mineral content (BMC) and bone mineral density (BMD), and 5 were examined by use of pQCT to measure BMD. Among these, 1 region was examined by both noninvasive methods and an invasive method. Volume of the femur was determined by water displacement. Volumetric bone density (VBD) was calculated. Calcium (Ca), phosphorus (P), total Ca, and total P contents were determined.
Results—DEXA- and pQCT-derived results revealed that all values increased with age in juvenile dogs. In adults, VBD and pQCT-derived BMD decreased significantly and DEXA-derived BMD increased with increasing femur length. The pQCT-derived BMD correlated well with VBD and Ca content, whereas DEXA-derived BMC was strongly correlated with Ca content. In juveniles, values correlated regardless of the technique used, whereas in adult dogs, DEXA-derived BMD did not correlate with pQCT-derived BMD, Ca concentration, or VBD unless data were adjusted on the basis of femur length.
Conclusions and Clinical Relevance—DEXA-derived BMD adjusted for femur length yields approximately the same percentage variability in VBD as for pQCT-derived BMD. However, pQCT-derived BMD is still more sensitive for determining variability in Ca concentration, compared with DEXA-derived BMD adjusted for femur length. (Am J Vet Res 2004;65:891–900)
with reasonable precision and accuracy include total body water measurement and DEXA. 1 Dual-energy x-ray absorptiometry estimates body composition by use of photons of 2 energy levels (70 and 140 kVp), which are impeded differently by bone mineral
characteristics of fragmented coronoid processes differ from those of unaffected MCPs. The purpose of the study reported here was to objectively quantify BMD in MCPs of dogs with and without FMCPs by use of DEXA and to establish how previously reported regional
Abstract
Objective
To compare percentage of body fat (%BF) estimates from dual-energy x-ray absorptiometry (DEXA) with those derived from total body water (TBW) determination by deuterium oxide (D2O) dilution.
Animals
31 healthy, adult, purebred dogs of various ages and breeds (body weight, 15 to 39 kg).
Procedure
The TBW was measured by D2O dilution and subsequent analysis via nuclear magnetic resonance (NMR). Blood was collected before and 2 hours after IV administration of 275 mg of D2O/kg of body weight. Plasma was separated and stored at −30 C until analysis by deuterium NMR. The DEXA scans were obtained immediately after blood collection from dogs under general anesthesia.
Results
Measurements of %BF by DEXA averaged 15.8% higher than calculated estimates of TBW content by D2O dilution. The linear regression of %BF by TBW content on %BF by DEXA had a slope of 1.04 and a correlation coefficient of 0.84, indicating excellent relative agreement between methods despite the significant difference in absolute agreement between the 2 methods. The average difference between methods did not differ by breed, sex, body condition score, body weight, or %BF, as measured by DEXA.
Conclusion
Comparability of our data with those of previous studies suggest that DEXA is useful for in vivo estimation of body composition in healthy dogs. Body fat estimated by D2O dilution will be less than that determined by DEXA, despite excellent relative agreement between methods. (Am J Vet Res 1998;59:529–532)
well as in animals with experimentally induced osteoarthritis. 7 In the preceding 2 decades, the use of various techniques such as DEXA, peripheral QCT, micro-CT, and conventional QCT for image-based quantitative assessment of trabecular bone density
Abstract
Objective—To document effects of cisplatin on regenerate bone formation during the distraction and consolidation phases of bone transport osteogenesis.
Animals—10 skeletally mature hounds.
Procedure—Bone transport osteogenesis was performed to reconstruct a 3-cm defect in the radius of each dog. Five dogs were randomly selected to receive cisplatin (70 mg/m2, IV, q 21 d for 4 cycles), and 5 were administered saline (0.9% NaCl) solution. Bone mineral density was measured by use of dual-energy x-ray absorptiometry (DEXA) on days 24, 55, and 90 after surgery. Dogs were euthanatized 90 days after surgery. Histomorphometry was performed on nondecalcified sections of regenerate bone. Bone mineral density and histomorphometric indices of newly formed bone were compared between groups.
Results—Densitometric differences in regenerate bone mineral density were not detected between groups at any time period. Cisplatin-treated dogs had decreased mineralized bone volume, decreased percentage of woven bone volume, decreased percentage of osteoblast-covered bone, increased porosity, and increased percentage of osteoblast-covered surfaces, compared with values for control dogs. Lamellar bone volume and osteoid volume did not differ significantly between groups.
Conclusions and Clinical Relevance—Regenerate bone will form and remodel during administration of cisplatin. Results of histomorphometric analysis suggest that bone formation and resorption may be uncoupled in cisplatin-treated regenerate bone as a result of increased osteoclast activity or delayed secondary bone formation during remodeling. These histomorphometric differences were modest in magnitude and did not result in clinically observable complications or decreased bone mineral density as measured by use of DEXA. (Am J Vet Res 2002;63:703–711)
frozen at −70°C for future assays by means of a previously validated method. 26 Cortisol concentration was measured by use of a commercially available radioimmunoassay. n DEXA scans —Eight hypothyroid dogs and 8 euthyroid dogs underwent a DEXA scan to