The effect on radiographic definition of X-ray tube movement

This study was designed to measure the vibration of three X-ray tubes in simulated clinical conditions and the effect of this on image quality. Vibration was measured by exposing film to an X-ray beam collimated by a lead diaphragm with a pin-hole. Exposures were made of a test specimen with the X-ray tubes stationary and while oscillating after positioning by vertical, lateral and forward movements. The damping time for the X-ray tube to stop oscillating varied with the machine from 3 s to 102 s. The radiographic patterns caused by tube oscillation varied from closed loops to figure of eight movements with periodicities of between 0.5 and 1.0 s. Amplitudes of up to 5.9 mm were recorded; they were greater in a horizontal direction and affected by arm extension. Images of bone trabeculae and of small holes drilled in the proximal surfaces of two teeth were little affected by tube movement. Only under magnification was the definition of a ball-bearing seen to be slightly less distinct, with less than 1% variation in size. These effects are likely to be of little clinical significance.