Ultrashort (millisecond) timing and a rapid film changer in pediatric radiography; evaluation of dynapulse and impulse timing.

Abstract

During the past 20 months an x-ray timer capable of exposures as short as 1/1000 second has been used to determine whether ultrashort exposures are more advantageous than those obtained with conventional timers, including the impulse timer.* The average impulse timer does not function faster than 1/60 second, but specially built ones produce exposures as short as 1/120 second, and, for practical purposes, the usable portion of this interval is probably 1/200 second. The Dynapulse timer is five times faster than the shortest possible exposure with an impulse timer.* Dynapulse exposures are produced by a controlled-electron-flow vacuum tube placed in the high-tension, or secondary, circuit of an ordinary rectified x-ray generator with a filter condenser across its output. This differs from conventional timers, which operate in the primary, or low-tension, circuit. Power from the condenser is released to the x-ray tube by the timer. It has been claimed that ultrashort