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Psychophysical properties of a new F-speed intraoral film

¹ Department of Oral Diagnosis and Radiology, School of Dentistry, University of Athens, Greece; ² Department of Oral and Maxillofacial Radiology, Faculty of Dental Science, Kyushu University, Fukuoka, Japan; ³ Department of Oral Radiology, Karolinska Institutet, Stockholm, Sweden

*Correspondence to: M Mastoris, Department of Oral Diagnosis and Radiology, School of Dentistry, University of Athens, 143–145 Lomvardou Str., Ampelokipi, 114 75, Athens, Greece; Email: michaelmastoris{at}hotmail.com

Received 24 June 2002; revised 16 January 2004; accepted 29 February 2004

Objectives: To compare the psychophysical properties of the new Kodak InSight F-speed intraoral dental film with those for the E-speed Ektaspeed Plus film by means of the perceptibility curve (PC) test.

Methods: A specially designed test object was used. The test object was made of aluminium and was 10 mm thick. It contained ten holes, contrast details, with the same diameter of 1.5 mm but with different depths. The depths ranged from 0.03 mm to 0.30 mm in steps of 0.03 mm. The holes were placed randomly within a square area with a total of 16 possible positions. Radiographs of the test object were obtained over the full exposure ranges of the two films. A Combex DX-907 dental X-ray unit was used operating at 10 mA and two tube potentials, 70 kVp and 90 kVp. The focus-to-object distance was 50 cm. Ten observers evaluated the radiographs under uniform artificial lighting using a view box and stated the number of perceptible representations of contrast details. In order to construct perceptibility curves, absolute values of the reciprocal of the minimum perceptible logarithmic exposure differences, 1/(logE)_min, were plotted as functions of the logarithm of exposures, logE, registered by the tested films. Comparisons between the two films were made separately for the two tube potentials, 70 kVp and 90 kVp.

Results: The results are presented graphically. PCs for the InSight film had higher peaks than those for the Ektaspeed Plus film. This indicates that the viewers were able to perceive smaller exposure differences in the former compared with the latter. PCs for the InSight film were shifted towards the left along the exposure axis relative to the PCs for the Ektaspeed Plus film indicating that the former film is more sensitive than the latter. The integrals of the PCs for InSight film were larger than those for Ektaspeed film indicating superior psychophysical properties of the InSight film.

Conclusions: From the point of view of perception, the new InSight film has such psychophysical properties in comparison with Ektaspeed Plus film that it will be the more favourable of the two in clinical radiographic practice.

Keywords: radiography, intraoral; X-ray film; perception