title: Rapid in vivo whole body composition of rats using cone beam μCT.
abstract: Precise, noninvasive analysis and quantification of in vivo body composition is essential for research involving longitudinal, small-animal disease models. We investigated the feasibility and precision of a rapid, flat-panel μCT scanner to report whole body adipose tissue volume (ATV), lean tissue volume (LTV), skeletal tissue volume (STV), and bone mineral content (BMC) in 25 postmortem female and 52 live male Sprague-Dawley rats. μCT images, acquired in three 90-mm segments and reconstructed with 308 μm of isotropic voxel spacing, formed contiguous image volumes of each entire rat specimen. Three signal-intensity thresholds (determined to be -186, 5, and 155 HU) were used to classify each voxel as adipose, lean, or skeletal tissue, respectively. Tissue masses from the volume fractions of ATV, LTV, and STV were calculated from assumed tissue densities of 0.95, 1.05, and 1.92 g/cm(-3), respectively. A CT-derived total mass was calculated for each rat and compared with the gravimetrically measured mass, which differed on average for the postmortem female and the live male group by 2.5 and 1.1%, respectively. To evaluate the accuracy of the CT-derived body composition technique, following the live male study excised muscle tissue in the lower right leg of all rats in group B were compared with the image-derived LT measurement of the same regional compartment and found to differ on average by 2.2%. Through repeated CT measurements of postmortem specimens, the whole body ATV, LTV, STV, and BMC measurement analysis gave a precision value of ±0.6, 1.9, 1.7, and 0.5% of the average value, respectively.
authors.affiliation: Imaging Research Laboratories, Robarts Research Institute, University of Western Ontario, London, Ontario, Canada.
authors.forename: Patrick V
authors.initials: PV
authors.lastname: Granton
authors.forename: Chris J D
authors.initials: CJ
authors.lastname: Norley
authors.forename: Joseph
authors.initials: J
authors.lastname: Umoh
authors.forename: Eva A
authors.initials: EA
authors.lastname: Turley
authors.forename: Bruce C
authors.initials: BC
authors.lastname: Frier
authors.forename: Earl G
authors.initials: EG
authors.lastname: Noble
authors.forename: David W
authors.initials: DW
authors.lastname: Holdsworth
mesh_terms: D000273:Adipose Tissue / Q000000981:diagnostic imaging*; D050154:Adiposity; D000818:Animals; D001823:Body Composition; D015519:Bone Density; D001842:Bone and Bones / Q000000981:diagnostic imaging*; D005240:Feasibility Studies; D005260:Female; D008297:Male; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging*; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted; D051381:Rats; D017207:Rats, Sprague-Dawley; D015203:Reproducibility of Results; D055114:X-Ray Microtomography