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Mapping of the ghost envelope for an Orth Oralix panoramic x-ray unit (Philips Medical Systems) was carried out with a lead sphere suspended at various locations around a dry mandible. The ghost envelope is a three-dimensional zone within which an object or anatomic structure must lie to produce a ghost image on panoramic radiographs. If the three-dimensional shape of the ghost envelope for a particular panoramic unit is known, information can be gained about the clinical location of objects appearing on radiographs produced with that machine. Objects outside the envelope will not result in ghost image formation. Objects within the envelope will result in characteristic ghost images depending on their position. This article analyzes ghost image characteristics in relation to object position and discusses the limitations of the method. A series of ready reference diagrams is provided, which may aid in the localization of soft tissue calcifications and foreign objects observed on panoramic radiographs.

This article deals with the incidence of anatomic variations in the styloid process and stylohyoid ligament as found in panoramic radiographs. Also, the accuracy was determined for measuring the length of styloid processes from panoramic radiographs, the variation in length of the styloid process with age, and the relationship of elongated styloid processes and ossified stylohyoid ligaments to symptoms of styloid-stylohyoid syndrome. Variations in styloid process and stylohyoid ligaments are not uncommon, especially segmentation of the process in young subjects. The apparent length of the styloid process was magnified approximately 1.37 times and was never diminished by panoramic radiographs. A steady increase in styloid process length was observed to age 30 years, with another slight increase starting at age 60 years. Subjects with elongated styloid processes (greater than 40 mm) had the highest incidence of discomfort on swallowing, whereas subjects with ossification of the stylohyoid ligament had the highest incidence of discomfort on turning the head from side to side.

A modification of the standard bisecting-angle technique for periapical views of incisor teeth is presented. The technique involves a constant x-ray cone position, which is perpendicular to the floor for maxillary incisors and parallel to the floor for mandibular incisors. The periapical film is held between the incisor teeth as if it were an occlusal film for all anterior periapical radiographs. Tracings from lateral skull radiographs, taken of dried skulls of various ages, were used to determine the optimal angle between the periapical film and the floor to produce a dimensionally accurate periapical view of the incisors. The technique is suggested as an alternative to the standard bisecting-angle technique and the parallel technique. It is intended for anterior periapical radiographs when clinical conditions make conventional techniques difficult. For example, it can be used in very young children, patients with gagging problems, and patients with narrow lower jaws or large muscular tongues.