This technique takes advantage of partially-coherent x-rays and diffraction to enable clear …

• Abstract
• Background
• Results
• Discussion
• Conclusion
• Methods
• Abbreviations
• References
• Table 1
• Table 2
• Figures

Synchrotron x-ray phase contrast imaging shows great promise as a powerful new tool for internal visualization in biological and medical research. This is the only generally applicable technique that has the necessary spatial and temporal resolutions, penetrating power, and sensitivity to soft tissue that is required to visualize the internal physiology of small living animals on a scale from millimeters to microns. The impact of this technique is just beginning to be seen as it is applied to some of the more easily arranged experiments such as those on the respiratory systems of insects, where it has already had a major impact. The discovery of rhythmic tracheal compressive movements in taxa in which it was previously unknown [6] has opened whole new areas of research, for example those aimed at determining morphological mechanisms of compression and the role of associated convection in insect physiology and evolution. Another exciting possibility is the visualization of previously unknown, complex circulatory patterns within insects that have only been inferred before from changes in body surface temperature [34].

Current uses of the technique include the analysis of the rapidly moving internal mouthparts of biting insects and the visualization of fluid motion in the pumping organs of fluid feeding insects such as flies and butterflies. The ability to see inside the animal, including the internal workings of jaws, legs, and wing hinges, may be of significant utility in the exploration of functional diversity. Although more challenging due to lower density differences, this approach has also yielded impressive x-ray video of insect digestive (Figure 1e–l; see also Additional files 2 and 3) and circulatory system function, including the pumping of the tiny pulsatile organs that maintain the internal pressure of the antennae of ants. The first synchrotron research on living vertebrate musculoskeletal systems has recently begun with successful video of the interior bones of the pharynx and skull during fish respiratory pumping. The potential for investigation of model systems in genetics and medicine such as fly, zebrafish, and mouse is considerable, as the natural and normal mechanisms of heart, circulatory, digestive, and locomotor systems can be analyzed in new ways and compared to mutants or disease models that may be used to study human health concerns. Ultimately, the ability to clearly visualize internal functions in small animals will have a large impact in both biology and medicine.