Flash Energy Subtraction Technique Using a Thin Metal Filter

The flash energy subtraction technique, its principle of operation, and the control methods concerning the FX spectrum distribution are described. This technique was performed by using a high intensity soft flash x-ray (FX) generator having spectrum control functions, Fuji computed radiography (FCR) achieved with a subtraction function, a thin metal filter of copper, and two or three imaging plates. The FX generator was a single exposure type and consisted of the following components: a high voltage generator, a simple low impedance coaxial transmission line with a high voltage coaxial condenser (0.2μF, 100kV), a gas gap switch having a high energy trigger device, a turbo molecular pump, and two types of demountable FX tubes, each of a different type. The FX distribution was controlled to the wide energy latitude from very soft to slightly hard in order to perform the single exposure (flash) energy subtraction radiography. The peak intensity of the FX spectrum rapidly shifted the high photon energy region according to insertion of metal filters. Various single exposure subtraction images were obtained by the subtraction between the soft image (no filter) and the hard image (after filtering).