While computed tomography (CT) imaging is by far the most predominant anatomical imaging device used to evaluate non-neurological malignancies in humans, its role in imaging small animal malignancies (especially rodent models of human tumors) has been much more limited due to the unacceptably high radiation dose levels necessary to image at the needed spatial resolution. These doses can interfere with tumor growth and metabolism and thus may compromise the actual scientific studies the scans were intended to evaluate. The development of phase-contrast imaging, however, offers one potential mechanism for improving soft tissue tumor detectability in small animals with potentially lower radiation doses. ? ? Phase-contrast imaging utilizes the diffraction of x-rays as they pass through tissue interfaces to obtain additional information not available to traditional absorption radiography. In addition, these images have a characteristic edge-enhancement effect that tends to increase lesion conspicuity. Because the technique depends upon the diffraction, rather than absorption, of x-rays, these images can be obtained at radiation doses potentially much lower than conventional absorption radiographs. ? ? Our laboratory has been investigating phase-contrast radiography (PC-R) for several years, and recently we have partnered with the x-ray source development group of the Free Electron Laser (PEL) Laboratory (located on the Vanderbilt University Campus) to investigate the feasibility of incorporating a newly- developed high-intensity x-ray production device into our existing PC-R system. The x-ray source is completely independent of the Free Electron Laser itself and has been designed specifically to function as a """"""""table-top"""""""" source that could be generally available to medical facilities. The x-ray beam produced by this source is largely monochromatic and has an extremely high spatial coherence (the central requirement of phase-contrast imaging). In addition, it has been designed to provide a high x-ray flux. We now propose to extend that work into the development of a phase-contrast computed tomography scanner (PC-CT). In this study, we will optimize the imaging parameters and CT reconstruction algorithms for PC-CT and we will determine whether a small-animal PC-CT scanner is feasible by comparing PC-CT to a commercial, state-of- the-art small-animal microCT scanner using quantifiable data from images of a custom phantom and radiation dose measurements. ? ?
