Absolute measures of image quality for the Sens-A-Ray direct digital intraoral radiography system

Influence of tube potential setting and dose on the visibility of lesions in intraoral radiography

OBJECTIVES

The objectives were to determine the diagnostic accuracy of different image receptors when first, the tube potential setting was increased from 60 kV to 90 kV and second, when the milliampere setting was reduced at unchanged tube potential for storage phosphor plates.

METHODS

Intraoral radiographs (films of speed class F, storage phosphor plates) were taken of 12 dried human skulls prepared with lesions in both teeth and peri-implant bone, in ascending size. Five observers assessed the presence (response=1) or absence (response=0) of lesions. The digital intraoral radiograph was exposed at 60 kV and 90 kV with half and a quarter of the film exposure. Some of the radiographs were assessed a second time. In total, 6000 assessments were made. Intrarater agreement was expressed by Cohen's kappa coefficient.

RESULTS

The digital combinations showed the lowest diagnostic accuracy in all combinations, but the results demonstrated an equivalence of all combinations of films and storage phosphor plates. The differences in diagnostic accuracy were low (94-96.5%). The kappa coefficient for intrarater agreement was high (0.85).

CONCLUSIONS

Regarding peri-implant and decayed lesions, intraoral films and storage phosphor plates demonstrated equal quality in this in vitro study regardless of exposure at 60 kV or 90 kV.

Determination of the resolution of a digital system for panoramic radiography based on CCD technology

OBJECTIVES

To determine Line Spread Functions (LSFs) and Modulation Transfer Functions (MTFs) for a digital system for panoramic radiography: the Dimax I (Planmeca Oy, Helsinki, Finland) based on Charge-Coupled Device (CCD) technology.

STUDY DESIGN

A test object was specially designed having a gold foil positioned vertically. Images of the gold foil created edge functions that were used to determine LSFs and MTFs. The design of the test object made it possible to move the gold foil forward and backward relative to the central plane of the image layer by means of a micrometer screw. The experiment was carried out for different object depths in 5 different regions: the anterior, the canine, the premolar, the molar, and the TMJ regions. LSFs and MTFs were calculated using specially designed software.

RESULTS

The results are presented graphically. LSFs and MTFs for the central plane were essentially the same for all regions. The MTFs for different object depths in the 5 investigated regions exhibited typical characteristics of MTFs for panoramic radiography with the exception for the functions for the molar region.

CONCLUSIONS

The present findings indicate that the resolution of the Dimax I CCD system is comparable to that of film-based panoramic radiography.

Comparison of the diagnostic potential of direct digital and conventional intraoral radiography in the evaluation of peri-implant conditions

The aims of this study were to examine whether viewers agreed on details seen in direct (real time) digital and conventional film radiographs of implants, and whether there were differences in agreement between the systems. Intra-oral radiographs of implants were exposed both as direct digital and conventional film radiographs. Fifty pairs of radiographs with similar projection and exposure were selected, showing 59 implants. Ten viewers assessed the radiographs separately and noted eight different details. The viewers showed very high agreement in their assessments of radiographs of each technique separately, and there were no statistically significant differences. However, there was a tendency to stronger agreement in the direct digital radiographs in four assessed points out of eight. The patients' experience of having radiographs exposed with the two methods was also studied by questionnaire. The patients' opinions on the two techniques did not differ statistically. This study shows that digital radiography has at least equal diagnostic yield compared to film radiography.

Signal-to-noise ratios of 6 intraoral digital sensors

OBJECTIVE

The objective of this study was to compare the signal-to-noise ratios (SNRs) of 6 intraoral direct digital sensors. The sensors were Visualix 1, Visualix 2, DenOptix, Computed Dental Radiography (CDR), CDR APS, and Digora.

STUDY DESIGN

The sensors were exposed by using a dental x-ray machine operating at 50 kV, 8 mA and various exposure times. The phantom used was a hole measuring 1 mm in diameter and 1.25 mm in depth, drilled in a 10-mm-thick aluminum block. Digital images were transferred as 8-bit tagged image file format files and analyzed by using a personal computer.

RESULTS AND CONCLUSIONS

SNR values increased up to a maximum value at a certain exposure level and then, depending on the system, either decreased or maintained a high level with increased exposure. The Digora system produced the highest SNR values over a large exposure range, whereas the Visualix 2 and DenOptix systems produced the lowest SNR values. The 2 CDR sensors produced rather high SNRs but over a very small exposure range.

Film and digital radiography for detection of simulated root resorption cavities

OBJECTIVES

The purpose of this study was to evaluate observers' ability to detect simulated root resorption cavities in conventional radiographs and digital radiographs from a charge-coupled device system and a storage phosphor system and to determine whether the detectability was influenced by resorption size and exposure.

STUDY DESIGN

In teeth from dry mandibular jaw specimens, resorptive defects 1.2 mm in diameter and two different depths (0.6 and 0.9 mm) were prepared in the buccal root surface. Each tooth was radiographed at a number of different exposure settings. Observers were asked to rate their confidence that a resorption was or was not present using a five-graded confidence scale. Receiver operating characteristic analysis was used to evaluate the results.

RESULTS AND CONCLUSION

Given optimal exposures, all systems reached what might be considered clinically acceptable Az values (> 0.75). The storage phosphor system reached this value at considerably lower exposures than those required for both the film and charge-coupled device systems. There was a tendency to better detect the deeper lesions and to identify them at lower exposures.