title: Influence of IV Contrast Administration on CT Measures of Muscle and Bone Attenuation: Implications for Sarcopenia and Osteoporosis Evaluation.
abstract: OBJECTIVE
  The objective of our study was to characterize enhancement of muscle and bone that occurs on standardized four-phase contrast-enhanced CT.
  
  
  METHODS
  Two musculoskeletal radiologists reviewed standardized four-phase abdominal CT scans obtained with IV contrast material. The psoas area was measured, and the mean attenuation (in Hounsfield units) was recorded for the aorta, psoas muscles, posterior paraspinal muscles, and L4 vertebral body. CT attenuation measures were compared between anatomic regions and imaging phases with the paired t test; associations between measures were examined with the Pearson correlation coefficient (R).
  
  
  RESULTS
  The study included 201 patients (97 men, 104 women; mean age, 57.7 ± 12.5 [SD] years). Subject age was inversely correlated with unenhanced attenuation in the psoas muscles, posterior paraspinal muscles, and L4 (p < 0.001). The psoas muscles, posterior paraspinal muscles, and L4 enhanced significantly (p < 0.001) at all three contrast-enhanced phases. The greatest muscle enhancement was observed on delayed phase scans, whereas the greatest enhancement in L4 was seen on portal phase imaging. The unenhanced attenuation of the psoas muscles was significantly and negatively correlated with enhancement of the psoas muscles at the portal and delayed phases (p < 0.05 and p < 0.01, respectively), but these correlations were not seen for the posterior paraspinal muscles. Age was positively correlated with posterior paraspinal muscle enhancement at the portal and delayed phases in men (p < 0.05 and p < 0.01, respectively) but not in women.
  
  
  CONCLUSIONS
  Contrast enhancement of commonly measured muscle and bone regions is routinely observed and should be considered when using CT attenuation values as biomarkers of sarcopenia and osteoporosis. Furthermore, CT enhancement may be significantly influenced by age, sex, and unenhanced tissue attenuation.
authors.affiliation: 1 Department of Radiology, University of California Davis School of Medicine, 4860 Y St, Ste 3100, Sacramento, CA 95817.
authors.forename: Robert D
authors.initials: RD
authors.lastname: Boutin
authors.affiliation: 1 Department of Radiology, University of California Davis School of Medicine, 4860 Y St, Ste 3100, Sacramento, CA 95817.
authors.forename: Justin M
authors.initials: JM
authors.lastname: Kaptuch
authors.affiliation: 1 Department of Radiology, University of California Davis School of Medicine, 4860 Y St, Ste 3100, Sacramento, CA 95817.
authors.forename: Cyrus P
authors.initials: CP
authors.lastname: Bateni
authors.affiliation: 1 Department of Radiology, University of California Davis School of Medicine, 4860 Y St, Ste 3100, Sacramento, CA 95817.
authors.forename: James S
authors.initials: JS
authors.lastname: Chalfant
authors.affiliation: 2 Department of Radiology and Imaging Sciences, National Institutes of Health, Bethesda, MD.
authors.forename: Lawrence
authors.initials: L
authors.lastname: Yao
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001012:Aorta, Abdominal / Q000000981:diagnostic imaging*; D003287:Contrast Media; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D010024:Osteoporosis / Q000000981:diagnostic imaging; D064170:Paraspinal Muscles / Q000000981:diagnostic imaging*; D016658:Psoas Muscles / Q000000981:diagnostic imaging*; D012189:Retrospective Studies; D055948:Sarcopenia / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media
keywords: CT; contrast media; osteoporosis; sarcopenia; skeletal muscle