High-resolution magnetic resonance imaging tracks changes in organ and tissue mass in obese and aging rats

Abstract

Tang, Haiying, Joseph R. Vasselli, Ed X. Wu, Carol N. Boozer, and Dympna Gallagher. High-resolution magnetic resonance imaging tracks changes in organ and tissue mass in obese and aging rats. Am J Physiol Regulatory Integrative Comp Physiol 282: R890-R899, 2002. First published November 8, 2001 10.1152/ajpregu.0527.2001.-Magnetic resonance imaging (MRI) has the ability to discriminate between various soft tissues in vivo. Whole body, specific organ, total adipose tissue (TAT), intra-abdominal adipose tissue (IAAT), and skeletal muscle (SM) weights determined by MRI were compared with weights determined by dissection and chemical analysis in two studies with male SpragueDawley rats. A 4.2-T MRI machine acquired high-resolution, in vivo, longitudinal whole body images of rats as they developed obesity or aged. Weights of the whole body and specific tissues were determined using computer image analysis software, including semiautomatic segmentation algorithms for volume calculations. High correlations were found for body weight (r ϭ 0.98), TAT (r ϭ 0.99), and IAAT (r ϭ 0.98) between MRI and dissection and chemical analyses. MRI estimated the weight of the brain, kidneys, and spleen with high accuracy (r Ͼ 0.9), but overestimated IAAT, SM, and liver volumes. No differences were detected in organ weights using MRI and dissection measurements. Longitudinal MRI measurements made during the development of obesity and aging accurately represented changes in organ and tissue mass.longitudinal body composition; in vivo; obesity; high-fat diet; small animal THE ACCURATE MEASUREMENT OF body compartments is important in the study of obesity and other diseases. There are many techniques available for body composition measurement, including hydrodensitometry, anthropometry, computerized tomography (CT), and dual-energy X-ray absorptiometry (14). Magnetic resonance imaging (MRI) and CT have been applied in the measurement of total and regional human and animal body composition (10,22,25). However, limitations associated with ionizing radiation in CT have made MRI a more desirable method for human body composition assessment, since it provides a safe, noninvasive, in vivo measurement approach (3).To evaluate the accuracy and validate the viability of MRI as a means of measuring body composition in rodents, Ross et al. (22) tested a model using MRI to measure adipose tissue (AT) and skeletal muscle (SM) volumes in rats. MRI-derived AT volumes were compared with those obtained by CT and chemical analysis in rats. The results (22) showed highly significant correlation coefficients among these methods without systematic differences, thereby demonstrating that MRI and CT assess AT volume with a comparable level of accuracy compared with chemical analysis in rats. Fowler et al. (10) reported that MRI accurately measured AT in lean and obese pigs in vivo, and Ishikawa and Koga (13) proposed an animal model of non-insulin-dependent diabetes mellitus for the accurate measurement of abdominal fat in Otsuka Long-Evans Tokushima fatty rats ...

Altered Upper Airway and Soft Tissue Structures in the New Zealand Obese Mouse

“…Previous studies in rodents have used physical methods, such as whole-body and regional dissection and analysis of fat deposits (42-44), or histological (microscopic) analysis of tissues (45). Whereas chemical analysis and dissection methods have been used for determining fat content in rodents, recent studies indicate that quantitative MRI provides more reliable measurements of fat content in rats and mice (43,46). Particularly in smaller animals, where dissection cannot easily separate organs and regional boundaries, noninvasive MRI techniques for measuring fat volume and distribution are preferable (46).…”

In vivo MRI quantification of individual muscle and organ volumes for assessment of anabolic steroid growth effects

“…It was a general-purpose software toolkit that runs on standard PCs or Unix workstations with IDL version 5.2 platform (ITT Visual Information Solutions, CO, USA) that provides all standard graphic functions required for the analysis in the current study [8,25]. To facilitate the rapid tissue segmentation and quantification, several functions were incorporated into a graphical user interface.…”

“…To facilitate the rapid tissue segmentation and quantification, several functions were incorporated into a graphical user interface. They included (i) multislice and multi-planar visualization of MRI data in standard formats including DICOM format; (ii) coarse histogram-based semi-automatic segmentation of local structures (muscle, fat and organs) by selecting specific range of image intensities within the image intensity histogram [8]; (iii) fine segmentation by 2D and 3D region growing from the initial histogram-based segmentation results to take advantage of tissue connectivity and structural similarity within the same or adjacent image slices [26]; (iv) manual segmentation and correction of segmentation errors; (v) labeling of various segmented structures by different colors; and (vi) volume and mass estimation of segmented structures by voxel sizes, numbers and densities assumed; (vii) data output to the standardized EXCEL files for statistical analysis. The integration of these seven functions into a single graphical interface led to minimal operator interaction and much improved segmentation efficiency, with flexibility to accommodate certain level of image quality variations that were slight but expected in high throughput MRI experiments.…”

“…Earlier MRI studies have demonstrated the high accuracy in measuring body adipose tissue in animal models when compared with chemical analysis [4,5], leading to MRI quantification of adipose tissue in humans [6,7]. High-resolution MRI was also shown to be capable of accurately tracking the individual organs (such as brain, liver, kidney and spleens), total skeletal muscle and adipose tissue mass longitudinally during aging and obesity development [8]. High-resolution MRI was also evaluated recently for its ability to measure individual muscles in human cadaver forearms [9].…”

Automatic segmentation of intra‐abdominal and subcutaneous adipose tissue in 3D whole mouse MRI

“…ADIPOSE TISSUE DISTRIBUTION is an important parameter when studying obesity and evaluating the efficacy of anti-obesity compounds (1,2) and MRI is a suitable methods to measure adipose compartments in both patients and animal models (3,4). MRI has the advantage that animals can be imaged on multiple occasions and studies can be designed so that each animal serves as its own control, increasing the statistical power of experiments and allowing group sizes to be reduced.…”