May fast screen-film combinations be used for cephalometry?

Exposure reduction in cephalography with a digital photostimulable phosphor imaging system

The effect on the determination of the cephalometric landmarks of exposure reduction using computed radiography with a photostimulable storage phosphor was evaluated. Forty patients attending for regular review were divided into four groups of 10. The first group was exposed to the same amount of radiation as that required for a conventional calcium tungstate screen-film combination. The other three groups were exposed to approximately 50, 20 and 10% respectively of the radiation dose of the first group. Ten dentists determined the landmarks. The coordinates of the points were recorded to measure the consistency of landmark identification. It was found that in comparison with the conventional screen-film system, a substantial reduction of exposure could be achieved with computed radiography for cephalography without clinical detriment.

Comparison of soft-tissue enhanced and conventional cephalometric radiographs

Pretreatment evaluation of the orthognathic surgery patient includes hard-tissue and soft-tissue analysis. Although the soft-tissue analysis can be made easier by the use of a Quint intensifying screen (Quint X-Ray Co, Inc, Los Angeles) which enhances the soft-tissue image, when the enhanced cephalometric radiograph was compared with a standard, nonenhanced radiograph, it was found to have the same level of diagnostic accuracy.

Exposure reduction and image quality in orthodontic radiology: a review of the literature

This article summarizes the use of rare earth screen technology to achieve high-quality panoramic and cephalometric radiographs with sizable reductions in patient radiation dosage. Collimation, shielding, quality control, and darkroom procedures are reviewed to further reduce patient risk and improve image quality.

The evaluation of high-speed screen/film combinations in cephalometric radiography

Cephalometric radiographs of a tissue equivalent plastic encased dry skull, each made with eight different screen/film combinations, were compared for usefulness in making orthodontic analyses. The eight screen/film combinations chosen ranged in relative speed from 80 to 600. Only one grid cassette was used, and it was a Par speed screen/film combination. Ten orthodontists identified 13 selected anatomic landmarks and rated the adequacy of their radiographic images. The density of each cephalometric radiograph was analyzed for each anatomic landmark. The results showed a difference in density readings for the various landmarks visualized. The optical density preferences of the 13 anatomic landmarks ranged between 0.87 and 2.09. The study leads to the conclusion that cephalometric radiographs can be taken with screen/film combinations that provide maximum useful information with a minimum dose level to the patient.

Landmark identification in computerized posteroanterior cephalometrics

A lack of cognition regarding the reliability of landmark identification in posteroanterior cephalometrics keeps the extracted data questionable. The present study was designed to analyze this problem for the purpose of providing certain insights. An interactive computer graphic package was developed. This package was called EA-PAX (Error Analysis of Postero-Anterior cephalometric X-ray films). A random sample of 40 clear posteroanterior cephalometric head plates was studied. The reliability of landmark identification was established. The skeletal landmarks seemed more reliable than the dental landmarks. The variation in the direction and magnitude of the error was determined for each landmark. Most landmarks had their own characteristic noncircular envelope of error. It is not the philosophy of the present authors to tell the orthodontists what to use. Rather, the philosophy is to be aware of the amount and direction of variation for a particular landmark. Taking this into consideration will enable the orthodontists to look on their cephalometric numbers with a mental awareness of the possible variations. Several clinical and research studies are suggested in the article.

Adaptation of the Panorex II for use with rare earth screen-film combinations

A series of radiographs of a tissue-equivalent phantom was taken in order to arrive at satisfactory radiographic techniques for the use of rare earth screens with the Panorex II. The radiation reduction needed for use of the rare earth screens was made with various filters. There was a 40% to 60% reduction in patient exposure for all of the rare earth exposures. Raters agreed that all films that were ranked were diagnostically acceptable, although differences were noted.

Kodak T-Mat G film in rotational panoramic radiography

Panoramic radiographs were taken of a tissue-equivalent phantom to evaluate T-Mat G and Ortho G films in combination with rare earth screens. The radiographs were compared to radiographs made with high-speed calcium tungstate screens and Kodak XRP film. The reduction in the amount of radiation necessary for the use of rare earth screens (50% to 70%) was accomplished by lowering the mA and adding filtration. All evaluated films were diagnostically acceptable. There was a marked preference of the T-Mat radiographs over the Ortho G radiographs and a slight preference over radiographs made with the standard calcium-tungstate screen-film system.

Diagnostic quality versus patient exposure with five panoramic screen-film combinations

Five film-screen combinations were used to make five density-matched panoramic radiographs of a tissue-equivalent phantom skull using the Midwest/Morita Panoral x-ray machine. The radiographs were evaluated as to their diagnostic quality by twenty dental radiologists. The results demonstrate that proper screen-film selection can significantly reduce patient exposure without compromising diagnostic quality.

Assessment of screen/film combinations for cephalometric radiography

Six different intensifying screen/film combinations were used to produce cephalometric radiographs of a tissue equivalent phantom skull. The adequacy of the films was assessed by seven orthodontists on two occasions. There was a low intra- and interobserver correlation. A more objective and reproducible method is required to evaluate intensifying screen/film combinations for cephalometric radiography.

The analysis of errors in orthodontic measurements

The sources of error in cephalometric measurement and their analyses are discussed. The importance of distinguishing bias and random errors is emphasized, and methods of control are discussed. Randomization of record measurement is one of the most important methods of avoiding bias, but it is rarely undertaken in cephalometric studies. Random errors are particularly important in the evaluation of individual radiographs, and a measurement that has a high error in relation to its total variability will be of little value in clinical assessment. In serial studies of facial change, the error variance is always a major part of the total variance and thus results have to be interpreted with caution. In cross-sectional studies it is not possible to specify exactly the acceptable limits of random errors, because this will depend on the difference between groups that would be of interest and on the number of cases. The judicious replication of measurements can be important in the control of random errors. In many papers, adequate error evaluation and control is lacking. In these circumstances, the results are of limited value because it is not possible to tell whether an apparent effect is the result of bias in measurement or whether a real effect is being obscured by random errors. It is incumbent on authors to consider how their measurement errors should affect the interpretation of results.

Clinical comparison of conventional and rare earth screen-film systems for cephalometric radiographs

This study compared cephalometric and P-A skull films taken with conventional (CaWO4) screens and rare earth screens. Patient exposure was reduced by 17 to 55 percent on two different x-ray machines by the use of rare earth screens. Results from 130 clinical evaluations showed that the diagnostic quality of radiographs taken with either system was roughly comparable. This presents a persuasive argument for the use of rare earth screens since the diagnostic quality of the films can be maintained while significantly reducing the patient's exposure to radiation.