Brief Description
Metabolic imaging refers to the use of non-invasive and minimally-invasive imaging and spectroscopic methods to characterize the structural, physiological, and biochemical properties of tissues, as well as the relationships among them. Because of the central role of energy metabolism in all cellular processes, many of these techniques focus on the localized quantification of metabolite concentrations and metabolic flux rates. Methods also exist for quantifying related processes such as blood flow. Other physiological imaging methods exist for the determination of tissue microstructure, material properties, and mechanical behavior.
There are many compelling reasons to use metabolic imaging approaches, including a number of unique measurement capabilities, the minimal disruption of normal physiology, and the ability to appreciate temporal and spatial variations in tissue physiology. The methods and projects described below are highly integrative in nature and broad in scope, and we therefore interact significantly with the other scientific programs of the VUIIS.
The VUIIS has a large number of technical resources for metabolic imaging and spectroscopy. These include:
- Magnetic resonance imaging and spectroscopy (MRI and MRS, respectively): Major capabilities exist for these studies, including 4.7, 7.0, and 9.4 T horizontal-bore animal scanners; a 4.7 vertical-bore scanner suitable for non-human primates; and two 3.0T and one 7.0T whole-body imagers for humans. MRI can produce highly detailed structural characterizations of animals and humans, on spatial scales of 10’s of um in animal studies and 100’s of um in human studies. In addition, a large number of physiological variables can be imaged using MRI, including large vessel structure and flow, microvascular function, diffusion of water and metabolites, activation of skeletal muscles during exercise, blood oxygenation levels, fat and water contents of tissues, mechanical strain development during cardiac and skeletal muscle contraction, and arterial wall motion. MRS methods can quantify the concentrations of many 1H, 31P, and 13C-containing metabolites and rates of flux through the creatine kinase, glycolytic, and oxidative phosphorylation pathways. The combination of MRI and MRS methods allows MR spectroscopic imaging, allowing maps of metabolite concentrations to be developed.
- X-Ray Computed Tomography (CT) methods also provide for high resolution anatomical imaging, but unlike MRI, which offers outstanding soft tissue contrast, CT excels in the imaging of hard tissues. Through the injection of CT contrast agents, physiological variables such as perfusion, flow, and vessel structure can be imaged.
- Nuclear Imaging methods, such as positron emission tomography (PET) and single photon emission computed tomography (SPECT), use injected radio-tracers to measure biochemical and physiological variables at lower resolution (millimeters) but with high specificity. Methods are available for quantification of glucose uptake, perfusion, receptors distributions, apoptosis, bone growth, and blood oxygenation. As for CT, the VUIIS’s nuclear imaging methods are dedicated to the study of small animals.
- Optical and Ultrasound Imaging offer lower-resolution measurements of a number of physiological parameters. For instance, near-infrared spectroscopy capabilities exist for both human and animal studies of blood flow, volume, and oxygenation. Ultrasound imaging capabilities exist for imaging macro- and microvascular flow; specific examples of the latter are given on the Cancer Imaging/Microbubble Contrast Enhanced Ultrasound page.
If you are interested in learning more about metabolic imaging and spectroscopy, consider joining one of our journal clubs:
Current Projects
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Metabolic Imaging & Spectroscopy
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