PubMed Health⌕ Search

Biomedical subjects

G J Randall

Publications and source records attributed to G J Randall.

7 recordsLinked to original sources
PubMed1983

High-yield radiography of the maxillofacial complex using the free focus and conventional imaging concepts. The resolution performance of nonscreen and screen-film combinations.

Free focus radiography with miniaturized dental x-ray machines may be a valuable source of "high-yield" diagnostic information in dentistry. This study evaluated the resolution performance of conventional image receptors, including nonscreen and screen-film combinations which were available in sizes suitable for panoramic free focus radiography or conventional extraoral radiography. Results with nonscreen films produced resolution performances ranging from about 10 lp/mm. to about 20 lp/mm. For each film tested, the performances in conventional radiography as well as in free focus radiography with the film in the buccal fold approached the maximum measurable of 20 lp/mm. In a mode of free focus radiography with the film positioned extraorally, there were significant variations in performance according to film brand. A significant reduction in resolution performance occurred when screen-film combinations were tested; resolution ranged between 4.0 lp/mm. and 7.4 lp/mm., with the better performance obtained with free focus radiography. The performance of a rare earth system was similar to other screen-film combinations tested in conventional radiography. In free focus radiography the performance of the rare earth system was slightly below the mean resolution for conventional screen-film combinations at 4.0 lp/mm. and 4.3 lp/mm. An example of a small cassette adapted for intraoral use was given.

Face↗
PubMed1981

Image resolution in dental and maxillofacial radiography with the conventional and "free focus" imaging concepts.

An investigation of the resolution capability of conventional and "free focus" dental radiography on non screen film was completed. The over-all imaging performance of conventional and "free focus" radiography exposed with three types of dental x-ray machines was comparable. Conventional "long-cone" radiography produced better resolution than "short-cone" radiography. "Short-cone" radiography exposed with conventional compact dental x-ray machines provided similar or better image resolution than those exposed with larger, high-energy machines. The miniaturized dental x-ray machines used in "free focus" radiography for periapical type exposures gave a resolution which was similar to or up to 100 percent higher than in conventional "long-cone" periapical radiographs. Differences in path length of the x-ray beam during clinical applications of conventional and "free focus" radiography indicated a higher potential for image noise and degradation in conventional films. A potential for segmental variation in image resolution in surveys of the dentition was seen only in the conventional techniques. These characteristics must be balanced against a tendency to variable segmental magnification in free focus radiography. Indications, however, are that applications of "free focus" radiography may be able to improve the early diagnosis of dental disease. Periapical type surveys of the dentition produced by "free focus" radiography may require only two exposures instead of the 14 to 20 required in conventional periapical surveys and may contain characteristics of periapical as well as bitewing films. "Free focus" radiography represents an attractive alternative that may be able to accomplish substantial time savings in the practice of dental radiography.

Face↗
PubMedDate not supplied

Free-focus radiography using conventional films--radiation exposures in a simulated clinical study.

This study compared air exposures during conventional dental and maxillofacial radiography and similar views using free-focus radiography with conventional image receptors. The results show that periapical type surveys on nonscreen film placed extraorally or in the buccal fold may be carried out with an exposure to the surface tissues, which is similar to or less than conventional dental radiography. Extraoral survey type radiographs of the jaws may be carried out with significantly less surface exposure than lateral oblique views of the jaws. The least exposure was required, when the film was placed in the buccla fold instead of against the face during free-focus radiography. The exposures with film screen combinations were reduced by an order of magnitude when compared to the nonscreen techniques. Proper filtration of the beam of the miniaturized x-ray machines radiography in dentistry may thus be desirable and applications in other parts of the body encouraged.

Cadaver↗