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.


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.


CONCLUSIONS
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.
Bauer
Jan S
JS
Department of Radiology, Technische Univerität München, Klinikum rechts der Isar, Institut für Roentgendiagnostik, Ismaninger Str. 22, München, Germany 81675. jsb@roe.med.tum.de
Henning
Tobias D
TD
Müeller
Dirk
D
Lu
Ying
Y
Majumdar
Sharmila
S
Link
Thomas M
TM
D000368:Aged; D000369:Aged, 80 and over; D015519:Bone Density; D003287:Contrast Media; D005260:Female; D006615:Hip / Q000000981:diagnostic imaging*; D006801:Humans; D008875:Middle Aged; D017698:Postmenopause; D011446:Prospective Studies; D016103:Spinal Fractures / Q000000981:diagnostic imaging*; D013131:Spine / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods*
D003287:Contrast Media