A comprehensive review of normal anatomic landmarks and artifacts as visualized on Panorex radiographs

The image of the hard palate/nasal fossa floor in panoramic radiography: the controversy is over

OBJECTIVE

The aim of this investigation was to obtain further information about the anatomic structures involved in the formation of the upper image of the hard palate/nasal fossa floor (HP/NFF).

STUDY DESIGN

Three dry human skulls underwent ostectomies along the HP midline (ie, the area of the junction of the nasal septum with the nasal fossa floor) and along posterior portions of the HP/NFF (ie, the horizontal plates of the palatine bones and part of the palatine processes of the maxillae). The radiographs were digitized and preostectomy and postostectomy optical densities were measured. Preostectomy and postostectomy optical densities were also measured.

RESULTS

Partial disappearance of the upper image occurred after ostectomy of the junction of the nasal septum with the NFF. Total disappearance occurred only after bilateral ostectomy of the posterior portions of the HP/NFF. The mean increases in regional optical density in terms of pixel gray level after the ostectomies were 70.44%, 72.27%, and 51.40%.

CONCLUSIONS

The junction of the nasal septum with the NFF and the posterior portions of the HP/NFF form the upper image of the HP/NFF. Most of the image is real, although a small part is a ghost image of the horizontal plates of the palatine bones and of the posterior region of the palatine processes of the maxillae.

Evaluation of off-axis projection geometry in dental panoramic radiography

New electronic imaging capabilities afforded by the use of linear charged-couple device arrays allow acquisition of three-dimensional information through simultaneous recordings from multiple sensors situated at different fixed angles. In theory, the resulting data can be processed to yield images tailored to specific diagnostic tasks that can be produced and manipulated on demand after exposure. The first step to determine the practical potential of such a system in panoramic radiography is to demonstrate the degree to which specific changes in projection geometry can be used to improve performance of selected diagnostic tasks of clinical interest in dentistry. Hence, the purpose of this investigation was to explore the potential to reduce proximal overlap that exist in current panoramic radiographs and also to displace the blurred image of the spine from areas of diagnostic interest through the use of off-axis projection geometry of the slit beam of radiation. As the off-axis angulation increased, more embrasures in the different areas of the dental arches of skull specimens were opened; the effects of beam angulation in the number of open embrasures was statistically significant (ANOVA, p < 0.05). A hypothetical multibeam system significantly improved the projection geometry toward the creation of images that contain little, if any, proximal overlap when compared with the conventional bilaterally symmetrical projection geometry system (t test, p < 0.001). At 6 degrees off-axis projection angle, the system was able to clear completely the anterior area from the superimposing shadow of the spinal column. The results show that multibeam alternatives to the single beam projection can significantly improve diagnostic quality in panoramic radiographs.

Redundant shadows in rotational panoramic radiographs. Estimating the imaging positions of objects by mathematical analysis

The sources of real, ghost, and double images in rotational panoramic radiographs generated by a machine with a continuous movement of the center of rotation are described. No assumptions are made with regard to the trajectory of the center of rotation; rather, an empirical approximation scheme is used to establish a regression from which measured positions of reference objects can be predicted.

Panoramic ghosts

The panoramic artifact of ghost images is discussed and explained. The three-dimensional area within which an object must be to produce a ghost image is depicted for three panoramic machines. The radiographic features of ghosts and the objects or anatomic structures that cause them are listed.

Medial sigmoid depression: a panoramic pseudoforamen in the upper ramus

A radiolucency resembling a foramen was observed on a number of panoramic radiographs in the upper ramus just below and slightly anterior to the sigmoid notch. The radiolucency may be unilateral or bilateral and does not correspond to the location of any known major foramina in this region. Eighty-eight skulls with mandibles were examined, and representative samples were photographed and radiographed in order to replicate this foramen-like radiolucency. The radiolucency corresponded to an osseous depression observable in some specimens in the medial portion of the ramus just below the sigmoid notch area. The incidence of this phenomenon in a study of 1,986 panoramic radiographs was also determined.

Clinical trial of pantomography for the evaluation of mandibular trauma

A trial study was conducted comparing the standard "four view" mandibular series and pantomography for th evaluation of mandibular trauma. During the six-month trial period a series of 17 patients with a total of 24 mandibular fractures was compiled. The pantomographs were more easily interpreted than the standard views because overlapping structures were blurred and spatial orientation was clear. In eight of the 17 patients the fractures were more clearly visualized by pantomography. Because the entire mandibule was seen so well on the pantomographs, no special views were required. Eleven patients had single fractures, which are in fact quite common.

Misdiagnosis of an impacted supernumerary tooth from a panographic radiograph

A panographic radiograph of a 31-year-old man revealed the presence of an impacted supernumerary paramolar. Periapical radiographs of the same area failed to confirm the existence of this supernumerary tooth. A review of the inherent distortion factors present in panographic radiography leading to the misdiagnosis is discussed.