title: Direct Comparison of Unenhanced and Contrast-Enhanced CT for Opportunistic Proximal Femur Bone Mineral Density Measurement: Implications for Osteoporosis Screening.
abstract: OBJECTIVE
  For patients undergoing contrast-enhanced CT examinations that include the proximal femur, an opportunity exists for concurrent screening bone mineral density (BMD) measurement. We investigated the effect of IV contrast enhancement on CT-derived x-ray absorptiometry areal BMD measurement.
  
  
  METHODS
  Our cohort included 410 adults (mean age, 65.3 ± 10.0 years; range, 49-95 years) who underwent split-bolus CT urography at 120 kVp. Areal femoral neck BMD in g/cm(2) was measured on both unenhanced and contrast-enhanced CT series with asynchronous phantom calibration. Constant offset and multiplicative factor corrections for the contrast-enhanced series were derived from the Bland-Altman plot linear regression slopes.
  
  
  RESULTS
  Mean unenhanced and contrast-enhanced areal femoral neck BMD values were 0.681 ± 0.118 and 0.713 ± 0.123 g/cm(2), respectively. The SD of the distribution of residuals for the constant offset and multiplicative model corrections were 0.0232 and 0.0231, respectively. The constant offset correction associated with contrast enhancement was 0.032 ± 0.023 g/cm(2), which corresponds to 0.29 ± 0.21 T-score units using the CT-derived x-ray absorptiometry young normal areal femoral neck BMD reference SD of 0.111 g/cm(2).
  
  
  CONCLUSIONS
  For the purposes of opportunistic osteoporosis screening, contrast-enhanced abdominopelvic CT studies are equivalent to unenhanced CT and can therefore be used for femoral neck BMD assessment. This measure could greatly enhance osteoporosis screening.
authors: 1 Department of Radiology, University of Wisconsin School of Medicine & Public Health, E3/311 Clinical Science Center, 600 Highland Ave. Madison, WI 53792-3252.
authors: Timothy J
authors: TJ
authors: Ziemlewicz
authors: 1 Department of Radiology, University of Wisconsin School of Medicine & Public Health, E3/311 Clinical Science Center, 600 Highland Ave. Madison, WI 53792-3252.
authors: Alyssa
authors: A
authors: Maciejewski
authors: 2 Department of Medicine, School of Medicine and Public Health, University of Wisconsin Osteoporosis Clinical Research Program, Madison, WI.
authors: Neil
authors: N
authors: Binkley
authors: 3 Mindways Software, Inc., Austin, TX.
authors: Alan D
authors: AD
authors: Brett
authors: 3 Mindways Software, Inc., Austin, TX.
authors: J Keenan
authors: JK
authors: Brown
authors: 1 Department of Radiology, University of Wisconsin School of Medicine & Public Health, E3/311 Clinical Science Center, 600 Highland Ave. Madison, WI 53792-3252.
authors: Perry J
authors: PJ
authors: Pickhardt
mesh_terms: D015502:Absorptiometry, Photon; D000368:Aged; D000369:Aged, 80 and over; D015519:Bone Density; D002138:Calibration; D003287:Contrast Media; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D008403:Mass Screening; D008875:Middle Aged; D010024:Osteoporosis / Q000000981:diagnostic imaging*; D019047:Phantoms, Imaging; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media
keywords: bone mineral density; contrast-enhanced CT; musculoskeletal system; osteoporosis; quantitative CT; screening