This report describes our initial experiences in the medical profession with real-time digital processing of X-ray transmission information taken from the video output of a conventional X-ray fluoroscopy and ciné fluoroscopy system. X-rays are produced with an X-ray tube operated between 45 and 100 kVp, 1 to 300 mA, and filtered by a variety of materials, the choice depending on the type of information which is to be isolated during the imaging process. The transmitted beam is detected by a cesium iodide image intensifier viewed by a television system with a lead-oxide vidicon tube.

The video signal is digitized to 8-bit accuracy every 100 ns and stored in any of three identical 256 by 256 random-access memories. Data may be temporally integrated to 13-bit gray-scale resolution. Several algorithms may be employed to process the data. All algorithms are presently dedicated hardware-based functions which were assembled in our laboratories. Although analog data may be processed from video tape, best results are achieved when image processing is performed on the original data. In the latter case the desired fully processed images appear during, or immediately after, the X-ray exposure.

Present imaging modes include (1) three-spectrum K-edge imaging of iodine, (2) time-dependent subtraction angiography using intravenous injections of iodinated contrast agents, (3) time-dependent subtraction mask mode imaging of nonopacified hearts, (4) time-derivative displays of opacified and nonopacified hearts, and (5) cardiac phase displays of nonopacified hearts. K-edge subtraction imaging of opacified hearts at rates of 30 to 60 per second is also being investigated.