In vivo measurement of radius calcium/phosphorus ratio by X-ray absorptiometry.
We describe a new method for assessing the skeletal Ca/P ratio in vivo using X-ray absorptiometry. By placing cerium (Ce) and samarium (Sm) filters in the X-ray beam from a commercial X-ray source (Norland), mean photon energies of 39 and 89 keV were obtained. The instrument was designed to take measurements of the forearm, at a site located at the distal 1/3 of the radius. The system was calibrated with three bone phantoms: Ca10(PO4)6(OH)2, Ca(HPO4)(H2O)2 and Ca(HPO4)2(H2O)). The precision for measuring the Ca/P ratio in the human radius was 2.3% CV for a skin dose to the forearm ranging from 0.3 to 0.4 mGy, depending on the width of the arm. The Ca/P ratio of the radius was significantly lower in patients with postmenopausal osteoporosis than in premenopausal controls.
Medical Physics Laboratory, Medical School, Ioannina University, Greece.
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G
Fountos
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Tzaphlidou
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Kounadi
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D
Glaros
D015502:Absorptiometry, Photon; D000328:Adult; D000368:Aged; D001842:Bone and Bones / Q000737:chemistry* / Q000166:cytology / Q000473:pathology; D002118:Calcium / Q000032:analysis*; D002130:Calcium Phosphates; D002563:Cerium; D004867:Equipment Design; D006801:Humans; D008875:Middle Aged; D010024:Osteoporosis / Q000473:pathology; D019047:Phantoms, Imaging; D010758:Phosphorus / Q000032:analysis*; D012044:Regression Analysis; D012493:Samarium
D002130:Calcium Phosphates; D010758:Phosphorus; D002563:Cerium; D012493:Samarium; D002118:Calcium