Room: Track 1
Purpose: Coherent scatter x-ray imagers are sensitive to molecular structure and consequently offer higher soft-material contrast than transmission-based imaging. We aim to develop practical projection scatter imaging systems with acceptable acquisition times. We report on configuring a benchtop x-ray tube-based system. Compared to our earlier synchrotron-based imager, such systems have the challenges of polychromaticity, tube thermal limits, and off-focal radiation.
Methods: X rays are furnished by a rotating anode tube (10 cm diameter anode, 1.2 mm focus) and single-phase generator at 110 kVp, 200 mA. Tungsten/copper collimation defines a 3x5 pencil beam array while minimizing off-focal radiation. Scattered photon patterns are acquired via step-and-shoot using a Perkin Elmer XRD 0840 AN13 flat-panel detector. The synchrotron-based system (Canadian Light Source) used a Hamamatsu C9252DK-14 detector, continuous object translation, and a line of five 33.2 keV beams.
Results: The shortest inter-exposure interval is ~0.67 s, for which repeated exposures =44 ms generate equilibrium anode stored heat below the allowed maximum of 185 kJ. Such exposures give a phantom incident air kerma ~10% that of our synchrotron acquisitions. Our Perkin Elmer detector, however, was measured to be ~100 times more sensitive than the Hamamatsu detector. The fastest synchrotron acquisition was 135 s for a 5x9 cm² image with 0.8 mm pixels. The x-ray tube-based system can acquire a 6x10 cm² image with 1.0 mm pixels in 278 s. Beam polychromaticity blurs the x-ray tube-based scatter patterns. Soft-material discrimination was tested with plastics. Polyethylene-polystyrene scatter image contrast is less than for the synchrotron system but still several times that of transmission imaging.
Conclusion: An x-ray tube-based scatter imager has reasonable acquisition times, on order of twice the time of a synchrotron system. It provides soft-material contrast superior to conventional imaging. While the synchrotron images have even higher contrast, the tube-based system is more practical.
Funding Support, Disclosures, and Conflict of Interest: This work was supported by the Natural Sciences and Engineering Research Council of Canada and by an Ontario Graduate Scholarship.