Subjective image quality of two differently processed digital cephalograms

Objectives: to evaluate the subjective diagnostic image quality of digital cephalograms processed with two image processing algorithms. Methods: Forty cephalograms were exposed with a CCD-based digital cephalostat Orthopantomograph®OC-100D (Instrumentarium Imaging, Tuusula, Finland) at four default exposure settings. A dry human skull covered with simulated soft tissue was employed to be the test object. The cephalograms were subsequently processed in two sets. In one set the cephalograms were processed by the default proprietary processing algorithms of the system while in the other the cephalograms were processed by two recently developed processing algorithms aiming at correction for exponential attenuation of an exposed object and correction for the response of the human visual system. Thus, a total of 80 cephalograms were created. These cephalograms were then evaluated by three radiologists and three orthodontists in a random order with respect to image quality of bone, image quality of soft tissue and also an overall evaluation of the image using a five digit scale from -2 to 2, in which -2 represents poor diagnostic image quality, 0 acceptable and 2 excellent diagnostic image quality. The cephalograms were observed under the same viewing condition. Results: No significant difference was found between the evaluations of the two sets of cephalogram but there was a significant difference between the evaluations by radiologists and by orthodontists (p<0.05). Conclusion: The subjective diagnostic image quality of cephalograms processed with correction for attenuation and visual response is comparable to those processed by the system default image processing algorithms.