Exposure reduction in cephalometric radiology: a comprehensive approach.

Various methods have been proposed and investigated for the purpose of reducing radiation exposures in cephalometric radiography. The purpose of this investigation was to use various dose-reducing methods from four major categories--(1) rare-earth intensifying screens, (2) rare-earth filtration, (3) prepatient soft-tissue enhancement methods, and (4) films varying in speed and latitude--to determine optimal combinations on the basis of exposure reduction and image quality achieved. In laboratory tests and clinical trials, radiation doses were compared along with various tests of image quality for the standard system currently used at this institution and for experimental systems. Image quality was assessed by standard panel-of-expert methods and more quantitative methods involving optical densitometry, contrast indices, and landmark envelopes of error. Results demonstrated that significant exposure reductions were achievable, often with improved image quality. The degree of exposure reduction was dependent largely upon the type of intensifying screen and to a lesser extent on beam filtration or film types. The greatest reduction in exposures were achieved with techniques using rare-earth beam filtration. Image quality was highest with a new wide-latitude type film. Because such significant reduction in radiation exposure for cephalometrics is possible with new techniques, we conclude that a change from the previous standard should occur. In establishing a new technique, orthodontists should consider adopting rare-earth screens and beam filters, flat-grained films, prepatient soft-tissue enhancement methods, and the elimination of grids.