PubMed Health⌕ Search

Biomedical subjects

T W Jensen

Publications and source records attributed to T W Jensen.

18 recordsLinked to original sources
PubMed1990

Fine-detail panoramic radiography by free-focus radiography. A clinical demonstration of diagnostic radiographs.

Previous comprehensive clinical studies have shown that free-focus radiography (FFR) may be used to improve image detail and diagnostic value in panoramic radiography of the teeth and jaws. This study demonstrated the clinical image quality in fine-detail panoramic FFR surveys relative to conventional surveys made by rotational panoramic or intraoral radiography. Cases of particular diagnostic interest with respect to common dental disease and changes in the jaws were included. The radiographic area of diagnostic interest depicted in FFR surveys generally resembled that of conventional dental radiographic surveys with the use of intraoral films rather then those of conventional rotational panoramic surveys.

Adolescent↗
PubMed1988

A clinical opinion survey of new fine detail panoramic radiographs.

An opinion survey was conducted to judge the diagnostic potential of panoramic surveys with image detail similar to periapical radiographs exposed by free-focus radiography. Fifty dentists evaluated four free-focus radiographic surveys of the maxillofacial complex made on nonscreen film, which were selected to illustrate most categories of common dental disease. Conventional rotational panoramic radiographs were available for comparison. Fifty-four percent to 70% selected positive responses to questions on film size, image detail, anatomic area of coverage, and potential value in dental practice. Relatively high percentages of reviewers preferred smaller anatomic coverage and film size. About one third thought that the level of image detail ought to be even better. The overall interest in a nonpanoramic free-focus radiography exposure mode was guarded. Seventy-six percent of all respondents believed that the free-focus radiography films were "experimental."

Attitude of Health Personnel↗
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↗
PubMed1983

Free focus radiography with miniaturized dental x-ray machines: a comparison of "midline" and "lateral" techniques.

The use of free focus radiography (FFR) employing miniaturized dental x-ray machines with radiation probes has never been generally accepted in dentistry despite its recognized radiographic potential. The present investigation studied ways to improve imaging and lower radiation burdens in dental free focus radiography. Relatively high air exposures ranging from 42,050 mR per film for high-resolution images to 3,214 mR per film for lower-resolution images using a current midline radiographic technique for panoramic FFR were found. In a proposed lateral FFR panoramic technique, reduced exposures ranged from 420 mR per film for high-resolution images to 14 mR per film for lower-resolution images. In each technique the lower exposure was obtained with a rare earth imaging system. A proposed modification of the current midline FFR technique using a rare earth imaging system and heavy added copper filtration was found to produce exposures in the range normally used in dentistry (207 mr), and the resultant image was high in contrast with relatively low detail. A comparison of essential characteristics of midline and lateral FFR techniques failed to identify specific advantages for the midline technique in current use. Lateral exposure modes in dental FFR should receive increased attention in the interest of good imaging and radiation control. It was noted that existing miniaturized dental x-ray machines may have been designed specifically for use of the midline FFR exposure technique, and modification of this equipment to support reliable lateral exposure modes was recommended.

Miniaturization↗
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↗
PubMed1979

The free focus concept in dental and maxillofacial radiography. The present status of the miniaturized dental x-ray machines.

"Free focus" radiography has shown promise in the examination of complex anatomy in many parts of the body, where conventional and tomographic exposures provide limited information. The approach was introduced in dentistry three decades ago and applied clinically from the time the miniaturized x-ray machines with rod anodes became available in the early 1960's. Yet it has received little attention in the international literature. Recent generations of the unique machines allow free focus surveys of the dentition in two exposures with a film quality comparable to or better than conventional periapical surveys and with a fraction of the radiation load. There is a need for evaluation of such procedures for use in dental practice. Additional applications of free focus radiography promise unusual flexibility in the use x-ray examinations in endodontics, pedodontics, periodontics, and oral surgery, which may justify further development of the miniaturized equipment for such new approaches. Specific suggestions for technical improvements are discussed.

Dental Equipment↗
PubMed1979

[A general roentgenographic procedure with high reliability and minimum radiation exposure].

Needs for exposure procedures in dental radiography with improved reliability and radiation hygiene, that can be applied with a minimum of time, have been documented. This publication presents a systematic approach to reliable dental radiography using beam guiding instruments which may meet such requirements. It can provide accurate radiographs in endodontic, periodontic and general practice and is adaptable to more time consuming special purpose radiography, including "serial identical" exposures and exposures of handicapped or anaesthetized patients.

Humans↗
PubMed1978

Beam-guiding instruments for simplified dental radiography, with a training device.

Needs for exposure procedures in dental radiography with improved reliability and radiation hygiene, which can be applied with a minimum expenditure of time, have been documented. This article presents dental instruments designed for use in recently published general purpose x-ray procedures which may meet such requirements. They can provide accurate radiographs in endodontic, periodontic, and general practice and are adaptable to more time-consuming special-purpose procedures, including "serial identical" exposures and exposures of handicapped or anesthetized patients.

Adult↗
PubMed1978

Improved reliability of dental radiography by application of x-ray beam-guiding instruments: a two-year report.

Demands on dental practitioners for documentation of patient needs plus evidence of high rates of inadequate radiographs in teaching and practice reveal a need for accurate, simplified radiographic techniques. New procedures using X-ray beam-guiding instruments were used for all periapical films in a clinical teaching program. Data collected over two years showed a high procedural reliability with these instruments. The film quality and low retake rate may have been due to the beam-guiding effect that also assures minimum patient exposure to radiation. Since beam-guiding instruments may also reduce the time expenditure in teaching and practice, the proposed procedures may be able to provide better radiography for less expense.

Dental Records↗
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↗