A comparison of the response of storage phosphor and film radiography to small variations in X-ray exposure.

OBJECTIVES: To determine the response to small repeated variations in X-ray exposure of storage phosphor (SP) plates compared with Ektaspeed Plus dental film. METHODS: Exposure of SP plates and Ektaspeed Plus dental film was varied within a small range [8.62 microC kg-1 to 9.03 microC kg-1, (5%)]. Radiographs were digitized and SP plates read with a laser-based scanner. Nested analysis of variance, analysis of covariance, and regression analysis were used to test the relationship between exposure and the resulting signal. RESULTS: The relationship between exposure and signal for digital images of film radiographs was not significant whereas the corresponding relationship for SP images was highly significant (P < 0.001, R2 = 0.44). CONCLUSIONS: Over the narrow range of X-ray exposures studied there was a significant direct linear relationship between exposure and digital gray-scale values for SP images but not for digital images of Ektaspeed Plus films.

Comparison of linear measurements made from storage phosphor and dental radiographs.

OBJECTIVES: To compare linear measurements made from storage phosphor and dental radiographs. METHODS: Five dry hemimandibles were imaged with an 8 x 10-inch (20.3/25.4 cm) high-resolution storage phosphor plate and Ektaspeed Plus occlusal-size dental film. Optimal exposure was empirically determined for the dental films. Reductions in exposure of 50 and 75% were used for the storage phosphor. Three observers made linear measurements between end-points of lines and center-points of fiducials on clinical specimens, dental radiographs, digitized dental radiographs and storage phosphor images. Data were analysed with repeated-measures and nested analysis of variance. RESULTS: Measurements obtained from optimally exposed dental films and reduced-exposure storage phosphor images were equivalent to clinical measurements recorded from dry hemimandibles. Less than 2% of variation among measurements was attributable to the five modalities. CONCLUSION: No substantive difference was detected between linear measurements obtained from the storage phosphor or dental radiographis. Because storage phosphor images require no chemical processing, can be used at reduced exposure and are inherently digital, they are a viable alternative to dental film for making linear measurements.

Histogram-matching and histogram-flattening contrast correction methods: a comparison.

OBJECTIVES: To compare the results or two methods of histogram matching and two methods of histogram flattening for their ability to correct for contrast variations in digital dental images. METHODS: A custom-built, aluminium stepwedge with 0.1, 0.5 and 1.0 mm steps was placed over Ektaspeed films and exposed for 0.06, 0.12 and 0.25 s, respectively. Radiographs were digitized at 50 microns spatial resolution and 12-bit contrast resolution. Contrast corrections were performed using Rüttimann et al.'s algorithm (1986) for one method of matching (RM) and flattening (RF) and Castleman's algorithm (1979) for the other method of matching (CM) and flattening (CF). Mean pixel grey-scale values were determined for each step. The 0.12 s exposure was considered to be the target image exposure. Absolute differences in pixel grey-scale values between the target images and the modified images were determined. RESULTS: The median values of the absolute differences in pixel grey-scale values between the target images and the contrast corrected images were: CM = 4.3; RM = 4.1; CF = 70.2 and RF = 70.2. CONCLUSION: Castleman's and Rüttimann's matching algorithms perform equally well in correcting digital image contrast. Histogram flattening was less effective.

A comparison of six intra-oral X-ray films.

OBJECTIVES: To compare objectively and subjectively national-brand dental X-ray films with widely available and less costly brands. METHODS: A range of dental films, including the recently released Kodak Ektaspeed Plus, was purchased from mail-order suppliers at the lowest published price. Objective measurements (film speed, contrast, fog levels, costs, physical characteristics) and subjective evaluations (ease of use, film graininess, overall appearance) were made. RESULTS: Private-label films were obtained at less cost than those of major vendors. Not all film speeds, sizes and wrapping materials were available from individual manufacturers. Objective measures and subjective appraisals showed that Ektaspeed Plus was the fastest film and had good contrast with the clinically useful density ranges. Agfa Dentus was the next fastest film, but it had rather low contrast and was grainier than the other films. The non-proprietary brands were difficult to open with primary glove barriers, making effective infection control practices arduous. All films were relatively stable over a 16-week period regardless of storage location. CONCLUSIONS: The major manufacturers offered more choices of film sizes and speeds than did private label suppliers. The films from the major manufacturers, although more expensive, were more conducive to effective infection control practices. Ektaspeed Plus had a performance comparable with or better than the other available films. Based on this preliminary study, it is recommended that this new film is considered as an alternative to D-speed films.

Objective and subjective evaluations of Kodak Ektaspeed Plus dental x-ray film.

A new dental x-ray film, Kodak Ektaspeed Plus (Eastman Kodak Co., Rochester, N.Y.), was compared with Kodak Ektaspeed and Ultraspeed films. The comparison was based on objective measures (film contrast, speed, and fog levels) and subjective appraisals (film graininess and appearance). Ektaspeed Plus had higher contrast than Ektaspeed and in general similar contrast to Ultraspeed. Ektaspeed Plus was faster than Ektaspeed. Films were stored in various locations and base + fog determinations were made during a 16-week period. Ektaspeed Plus and Ultraspeed films were generally stable within this period. There were no meaningful differences in fog buildup based on storage location. Ektaspeed Plus had the least rate of buildup. Ektaspeed demonstrated the greatest rate of buildup and the greatest sensitivity to environmental factors. Periapical exposures were made of the molars of a manikin. These radiographs were subjectively assessed by three observers. The Ektaspeed Plus film was judged to appear less grainy than the Ektaspeed and to have a pleasing appearance. On the basis of the evaluations performed in this initial investigation, it was concluded that Ektaspeed Plus was superior to Ektaspeed film and was superior or equivalent to Ultraspeed film for dental radiography.

Tympanic plate fracture from mandibular trauma.

A case in which trauma to the mandibular midline resulting in posterior displacement of the left condyle and subsequent fracture of the tympanic plate is presented. Use of computed tomography was helpful in confirming the presence of the injury.