Adipose Tissue Quantification in Rats with the Use of Computed Tomography

Background: Obesity studies involving animal models require a method for adipose tissue (AT) amount assessment. This paper focuses on the application of clinical computed tomography (CT) for abdominal obesity assessment in rats as an alternative to dedicated micro-tomographic systems. Additionally, the authors propose L1-L6 instead of L1-L5 region of interest (ROI) usually used for the intra-abdominal adipose tissue (IAAT) assessment and they check if the applied X-ray energy influences results. Methods: 16 Wistar rats with different body mass (BM) were involved in the study. The animals were scanned by CT to achieve three-dimensional images which were subsequently analyzed for AT amount. AT was identified on the basis of fixed Hounsfield unit scale. Two X-ray tube voltages were tested: 80 kVp and 120 kVp. The results were compared to the fat pads mass (FPM) extracted after animal sacrifice. FPM was also correlated to BM. Result: The correlation between FPM and BM was statistically non-significant (r=0.3131, p=0.2376). AT amounts obtained for different CT X-ray tube voltages (80 kVp vs. 120 kVp) were practically the same (r=0.9996, p < 0.001). There was significant correlation between FPM and AT mass based on CT images, regardless of the ROI choice. Correlation coefficients amount to r=0.932, p < 0.001 and 0.945, p < 0.001 for L1-L6 and L1-L5, respectively. Conclusion: BM is not a good descriptor of abdominal obesity. The X-ray beam energy and the choice of ROI do not influence the results considerably. CT allows for fast and reliable IAAT amount assessment in rats.