Segmentation and Measurement of Fat Volumes in Murine Obesity Models Using X-ray Computed Tomography

Abstract

Obesity is associated with increased morbidity and mortality as well as reduced metrics in quality of life.1 Both environmental and genetic factors are associated with obesity, though the precise underlying mechanisms that contribute to the disease are currently being delineated. 2,3 Several small animal models of obesity have been developed and are employed in a variety of studies. 4 A critical component to these experiments involves the collection of regional and/or total animal fat content data under varied conditions.Traditional experimental methods available for measuring fat content in small animal models of obesity include invasive (e.g. ex vivo measurement of fat deposits) and non-invasive (e.g. Dual Energy X-ray Absorptiometry (DEXA), or Magnetic Resonance (MR)) protocols, each of which presents relative trade-offs. Current invasive methods for measuring fat content may provide details for organ and region specific fat distribution, but sacrificing the subjects will preclude longitudinal assessments. Conversely, current non-invasive strategies provide limited details for organ and region specific fat distribution, but enable valuable longitudinal assessment. With the advent of dedicated small animal Xray computed tomography (CT) systems and customized analytical procedures, both organ and region specific analysis of fat distribution and longitudinal profiling may be possible. Recent reports have validated the use of CT for in vivo longitudinal imaging of adiposity in living mice. 5,6Here we provide a modified method that allows for fat/total volume measurement, analysis and visualization utilizing the Carestream Molecular Imaging Albira CT system in conjunction with PMOD and Volview software packages. Video LinkThe 3. Mice were anesthetized by Isofluorane (2.5% flow rate) and kept under at 2.5% via a nose-cone setup for imaging. Animals were positioned prone in the standard rat bed (M2M Imaging Inc. Cleveland, OH) in supplied with the Albira image station. Limbs were positioned lateral from the torso for a uniform CT acquisition. 4. After image acquisition was completed, mice were removed from the nose cone and returned to a recovery cage until ambulatory. Image Acquisition and Reconstruction1. Image acquisitions are performed using the Albira CT system (Carestream Molecular Imaging, Woodbridge, CT). Mice were anesthetized by Isofluorane (2.5% flow rate) and kept under at 2.5% via a nose-cone setup for imaging. Acquisitions were performed to scan a bed of 115 mm

Correlation of X-Ray Computed Tomography with Quantitative Nuclear Magnetic Resonance Methods for Pre-Clinical Measurement of Adipose and Lean Tissues in Living Mice

“…Nevertheless, this bandwidth may be re-gained through the use of bed systems that simultaneously scan 2–4 animals. MicroCT differentiates itself in that it merges quantitative analysis with a 3D visualization of region-specific adiposity within the specimen [ 19 ], an output that is not provided by the QMR technique, and is cumbersome to achieve with classic MRI.…”

“…The in vitro microCT experiments were conducted on the Albira CT System (Bruker BioSpin Corporation, Billerica, MA, USA) based on published protocols [ 19 ]. Two scans of each oil and water mixture were acquired at 45 kVp, with currents of 0.4 (high dose) and 0.2 (low dose) mA, at a 155 mm field of view (FOV).…”

“…Analysis of the microCT scans of the mice was performed mostly as adapted from Sasser et al [ 19 ]. The method is described briefly here.…”

Brown and beige adipose tissue regulate systemic metabolism to resist diet-induced obesity through metabolite signals in an inter-organ signaling axis

“…PET and CT image data was analyzed in PMOD, version 3.807. The methods used to calculate adiposity have been described previously 58 .…”

In vivo X-Ray Computed Tomographic Imaging of Soft Tissue with Native, Intravenous, or Oral Contrast

“…Lung tissue is distinguishable owing to the presence of air within its cavity, thus yielding significantly lower densities than the surrounding soft tissue and bone [2]. Adipose is high in fatty acids and is slightly less dense than adjacent soft tissue, which enables its recognition via segmentation with the use of the proper software [11]. Finally, brain tissue is generally homogenous on a CT, but its location is circumscribed by cranial bone and the tissue may be directly observed for changes occurring during disease progression [12,13].…”