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journal article 
Bauer, JS; Henning, TD; Müeller, D; Lu, Y; Majumdar, S; Link, TM 
Volumetric quantitative CT of the spine and hip derived from contrast-enhanced MDCT: conversion factors. 
OBJECTIVE: The purposes of this study were to perform volumetric quantitative CT (QCT) of the spine and hip using nondedicated contrast-enhanced standard MDCT data sets and to derive a conversion factor for bone mineral density (BMD) assessment based on dedicated volumetric QCT data sets. SUBJECTS AND METHODS: Forty postmenopausal women with a mean +/- SD age of 71 +/- 9 years underwent routine contrast-enhanced abdominal and pelvic MDCT. Before this imaging examination, standard volumetric QCT of the spine (L1-L3, n = 40) and hip (n = 21) was performed. Relations between QCT and contrast-enhanced MDCT findings were assessed with linear regression analysis. RESULTS: Mean lumbar BMD was 84.1 +/- 35.8 mg/mL, and mean femoral BMD was 0.62 +/- 0.12 g/cm2, as determined with QCT. Contrast-enhancement values with MDCT were on average 30.3% higher than those of QCT in the spine and 2.3% higher in the proximal femur (p< 0.05). Based on linear regression, a correlation coefficient of r = 0.98 was calculated for lumbar BMD with the equation BMD(QCT) = 0.96xBMD(MDCT) - 20.9 mg/mL. A coefficient of r = 0.99 was calculated for the proximal femur with the equation BMD(QCT) = 0.99xBMD(MDCT) - 12 mg/cm2 (p< 0.01). In 17 of 40 patients, 33 vertebral fractures were found. The dedicated QCT and enhanced MDCT data sets did not show a significant difference (p> 0.05) between patients with fractures and those without fractures. CONCLUSION: With the conversion factors, reliable volumetric BMD measurements can be calculated for the hip and the spine from routine abdominal and pelvic MDCT data sets. 
Journal title abbreviation:
AJR Am J Roentgenol 
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