Phantoms for Cross-Calibration of Dual Energy X-ray Absorptiometry Measurements in Infants
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OBJECTIVE: To test the suitability of phantoms to cross-calibrate body composition measurements in small subjects among different dual energy X-ray absorptiometry (DXA) instruments. METHODS: A set of four phantoms with total weights 1520g, 3140g, 4650g and 7490g were made with low cost and easily available materials. Each phantom was made from assembling polyethylene bottles (100 to 1000 mL) filled with either pure olive oil or electrolyte solution in different combinations, and borosilicate tubes (3 and 5 mL) and flexible polypropylene tubing filled with calcium carbonate. Triplicate measurements of each of the four phantoms were performed with three pencil beam densitometers made by the same manufacturer (Hologic Inc., Waltham, MA): two QDR 2000 (University of Liege, Liege, Belgium, and Wayne State University, Detroit, Michigan) and a QDR1500 (University Children's Hospital, Greifswald, Germany) using infant whole body-scanning mode and analyzed with software V5.73P. RESULTS: DXA measured total weight, or bone, lean and fat masses, from one center were highly predictive of DXA measurements from the other centers with an adjusted r2 of 0.94 to 1.00, p < 0.001. This was the case whether the measurements from single scan or from average of triplicate scans were used in the analysis. CONCLUSIONS: Systematic corrections, in the form of linear transformations, are possible to allow comparison of clinical data generated from different centers. Different size phantoms can be made to accommodate the varying range of weights and body composition of study subjects.
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