Panoramic radiography using an intraoral tube. Method, anatomy, radiography and dosimetry

BACKGROUND: There are two techniques giving a panoramic view of the dental arch: orthopantomography and intraoral tube panoramic radiography. The last one is not very well known because images, with a characteristic and variable deformity if compared with orthopantomography are not useful for routinary use in dentistry. The poor radiographic and pathologic anatomy knowledge of intraoral tube panoramic radiography, and the slight improvements brought to the method particularly in order to reduce the dose, partly depend on the scant attention given to the method by investigators, and partly on the dyshomogeneous anatomic sites enlargement and overlapping with consequent deformity of all of them. With intraoral tube panoramic radiography, X-ray exposition is emitted using a miniaturized cylindrical source placed inside the oral cavity and the radiographic film is in contact with the skin of the face. Based on the orientation of the collimator and the inclination of the tube major axis in the oral cavity, a central technique (exposition of either superior or inferior dental arch) and a lateral technique (simultaneous exposition of the two hemiarches of the same side) are recognized. The aim of this study is to give a significative contribution to maxillo-facial characteristic appearance and dosimetry knowledge in intraoral tube panoramic radiography. METHODS: It consists of: a) a "laboratory" part concerning the evaluation of the enlargement, deformation and visibility of different structures, obtained by positioning about fifty different markers in different maxillary and mandibular anatomic sites, and b) an in vivo dosimetry part obtained with intraoral and extraoral termoluminiscent dosimeters. An original dispositive allowed the right positioning of the film and its adherence to the screen. Deformity characteristics are analitically described and discussed in relation with the different sites. RESULTS AND CONCLUSIONS: The use of intensifying screens allowed a good reduction of dose, (mean absorbed doses ranging from 25 microGy in the intraoral sites to 1936 microGy in the extraoral sites) without reducing the image quality thanks to the device performed "ad hoc".