Multiple Energy Synchrotron Biomedical Imaging System- Preliminary Results

Abstract

The drive to improve and expand the amount of information extracted from various imaging modalities has led to the use of multiple (usually two) x-ray photon energies in computed tomography clinical systems. With the use of a single photon energy, the ability to differentiate soft from hard tissues is a problem which multiple energy imaging can solve. The continuous spectrum available from synchrotron light facilities provides a nearly an ideal source for multiple energy imaging. For living biological subjects a multiple energy system that can extract multiple endogenous or induced contrast materials as well as water and bone images would be ideal. A novel bent Laue single crystal monochromator that has a wide angularly dispersed energy range (polychromator) has been developed to explore the use of multiple energies simultaneously for biomedical imaging at the Biomedical Imaging and Therapy beamline at the Canadian Light Source. Using the 311 reflection from a 511 silicon crystal wafer bent to a radius of 95 cm, the system prepares a 0.5 mm wide focused polychromatic x-ray beam with a spectral range of 27 keV to 43 keV, covering both the iodine and barium K-edges of 33.17 keV and 37.44 keV, respectively. As an example use, test objects with iodine and barium (common contrast agents used in clinical imaging) along with water and bone were imaged and successfully extracted independent quantifiable images of these four materials. The biomedical imaging system is presented with emphasis on the polychromator used to prepare the imaging beam.