Dual energy rapid switching imaging system

Abstract

For hybrid digital subtraction angiography mask x-ray images are made at low and high x-ray tube anode kVp. Both exposures are terminated by AEC and the exposure times are calculated and stored and used to govern the times of a subsequent run sequence of alternate low and high energy pre-contrast and post-contrast exposure images. The data for the mask and subsequent images are stored individually on magnetic disk. A TV camera receives optical versions of the images. Its target is scanned or read out during a TV frame time between the end of a low energy exposure and the start of a high energy exposure. After the low energy mask exposure time is determined an anticipation or delay time is calculated and the low energy exposures in the run sequence are shifted from the vertical blank pulse preceding the frame in which the exposure starts by the delay time so all low energy exposures terminate coincident with the blanking pulse that precedes the read out frame. Since the high energy exposures are started at the end of the readout, minimum time between low and high exposures is achieved. High kVp is fixed. Low kVp and tube MA are selectable. High MA that the tube target can withstand thermally is calculated and adjusted so it will not result in excessive tube target bulk or focal spot temperature.