Reproducible MRI measurement of adipose tissue volumes in genetic and dietary rodent obesity models.
OBJECTIVE
To develop ratio MRI [lipid/(lipid+water)] methods for assessing lipid depots and compare measurement variability with biological differences among lean controls (spontaneously hypertensive rats [SHRs]), dietary obese rats (SHR-DOs), and genetic/dietary obese rats (SHROBs).


METHODS
Images with and without chemical shift-selective (CHESS) water suppression were processed using a semiautomatic method that accounts for relaxometry, chemical shift, receive coil sensitivity, and partial volume.


RESULTS
Partial volume correction improved results by 10% to 15%. Over six operators, volume variation was reduced to 1.9 mL from 30.6 mL for single-image-analysis with intensity inhomogeneity. For three acquisitions on the same animal, volume reproducibility was <1%. SHROBs had six times more visceral and eight times more subcutaneous adipose tissue than SHRs. SHR-DOs had enlarged visceral depots (three times larger than those in SHRs). SHROBs had significantly more subcutaneous adipose tissue, indicating a strong genetic component to this fat depot. Liver ratios in SHR-DO and SHROB were higher than in SHR, indicating elevated fat content. Among SHROBs, evidence suggested a phenotype SHROB* having elevated liver ratios and visceral adipose tissue volumes.


CONCLUSIONS
Effects of diet and genetics on obesity were significantly larger than variations due to image acquisition and analysis, indicating that these methods can be used to assess accumulation/depletion of lipid depots in animal models of obesity.
Johnson
David H
DH
Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio 44106, USA.
Flask
Chris A
CA
Ernsberger
Paul R
PR
Wong
Wilbur C K
WC
Wilson
David L
DL
D000273:Adipose Tissue / Q000033:anatomy & histology*; D000465:Algorithms; D000818:Animals; D001823:Body Composition; D004032:Diet; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009765:Obesity / Q000235:genetics / Q000473:pathology*; D019047:Phantoms, Imaging; D010641:Phenotype; D051381:Rats; D011918:Rats, Inbred SHR; D015203:Reproducibility of Results