The accuracy of single emulsion radiographic film in linear measurement of spiral tomography

BACKGROUND Conventional tomography used for evaluation of the small areas of the jaws provides acceptable information. It has some advantages of availability, less radiation dose and cost in comparison to computed tomography (CT) and cone beam CT. Double emulsion film usually used for taking tomograms requires less exposure than single emulsion film; on the other hand, the latter provides more sharpness and spatial resolution. The aim of this study was to compare diagnostic accuracy of these two kinds of films in the spiral tomography. MATERIALS AND METHODS In an experimental study, 20 lines (10 lines anterior and 10 lines posterior to the mental foramen) were selected on two dry human mandibles and tomographic images were taken from each line with and without metal marker by single and double emulsion films. For quantitative assessment, the mandibular width and length was identified and measured on 80obtained tomograms. Afterwards, the mandibles were sectioned on each line and their actual width and height were measured. For each line, the data of tomograms were subtracted from gold standard as measurement error. These errors were divided into three groups: Greater than +1 mm, between +1 mm and -1 mm and less than -1 mm. Obtained data were analyzed by Pearson Chi-square test (α=0/05). RESULTS There was no significant difference between the single and double emulsion films, with and without markers in the measurement of both height and width of mandible (P > 0.05). CONCLUSION The single emulsion film is not recommended to be used for taking the spiral tomogram.