X-ray tube voltage or tube voltage in short is applied across anode and cathode making a high electric field. This causes electrons to be emitted and move from cathode to anode.

The increase in tube voltage increases the average photon energy and affects the image contrast owing to x-ray blooming and the scatter. Appropriate tube voltage should be chosen according to the patient size.

Tube current, which is the electrical current that flows through the tube, determines radiation dose and image quality. Pulse x-ray is able to reduce the radiation exposure to a great extent producing a sequence of short x-ray pulses instead of continuous x-ray. However, the shorter the pulse, the quality of the image degrades accordingly.

X-ray pulse makes it possible for examination without exposing unnecessary radiation characterized by the term of frame per second (Fig. 7.2) and pulse width (Fig. 7.3). Reducing the number of frames per second above a standard level, the image lag will appear. On the other hand, reducing the pulse width above a level will degrade image granularity.