X-ray generation and control.

This article has focused on those aspects of X-ray generation that are of immediate concern to clinicians. Generators and tubes result from more than a century of basic technology, engineering design, and manufacturing know-how. How are the rotating anode bearings lubricated? Most tubes use ball bearings. They are exposed to temperatures ranging up to several hundred degrees Centigrade. They are expected to provide a reasonable lifetime while supporting the static and gyroscopic loads imposed by a heavy anode running at 10,000 rpm. This all happens in a vacuum. The answer is the use of silver alloy balls. Modern systems use many feedback circuits for precise control of X-ray output. Spatial, spectral, and temporal beam shaping are all active development areas. The goal is image optimization with minimum radiation risk to the patient. In exchange, the operator needs to tell the system something about the clinical requirements needed to manage the patient on the table. Other examples of the interaction of technical means and clinical requirements will be discussed in future articles.