Transmission Scanning Using a Continuous X-ray Source

A system of rectilinear scanning has been developed which senses the presence of particular elements by measuring the differential attenuation of x-ray photons about a specific absorption edge. A continuous x-ray spectrum generated from a side-window 50 kVcp tube is used and the transmitted beam is detected by an energy selective Ge(HP) semiconductor detector. Measurements on phantoms with absorbers up to 10 cm thick indicate sensitivity to middle Z elements such as iodine, down to the range of 1 mg/cm2 in reasonable scanning times. Little effect was seen by additional 1" absorbers, and the effects of in-line voids can be minimized. Scans were taken of rabbit kidneys and bileary tracts as an iodated contrast agent was infused, and of rabbit lungs while the animal breathed a xenon/oxygen mixture. Future directions for this technique of transmission scanning are discussed.