Chapter 6 Panoramic Radiography: Clinical Technique
Carefully read the introductory information on panoramic techniques. Note that further information on digital panoramic radiography is included, although a separate chapter has been dedicated to digital panoramic imaging. The machines illustrated are several of the newest and most advanced that are available in our dental school. Several other excellent brands are available. Also, many older panoramic machines are in schools and practices, and all of them can be operated basically in the same way. Slight differences in technique exist from one brand or model to another; however, the errors remain the same. The principles for the recognition and correction of errors are pretty well universal. Having said that, some brands or models may be more prone to certain errors or artifacts and some may even produce unique errors. The information here is the basis for understanding, recognizing, and correcting problems for most machines, models, and situations. Once this basic information is mastered, unique problems can be identified and corrected. And… by the way, we often forget to refer to the owner’s operating manual where most of the answers to common problems can be found.
The panoramic machines illustrated in this and other chapters are the Morita Veraviewepocs in a film-based version and the Planmeca ProMax Pan-Ceph factory digital panoramic machine. Older film-based panoramic machine designs can be converted to digital in two ways: (1) by substituting the film and fluorescent screen and chemical film development for the PSP memory plates and laser scanner; or (2) by substituting the cassette assembly for a CCD sensor. In either case, software and a computer will be needed. The factory-assembled digital panoramic machines come with the CCD sensor and appropriate software; however, a computer may not always be included. Digital panoramic machines have menus of functions and settings that can be selected on the machine; however, the machine software must also be opened in the computer, patient data entered, and other menus selected before an exposure can be made. All machines (film-based machines, digitally converted machines, and factory digital machines) have the same type of exposure switch that must be continually depressed throughout the exposure; releasing the pressure on the exposure button will abort the exposure cycle.
Also, some new panoramic machines such as the Morita Veraviewepocs can automatically correct for some positioning errors. An example is the automatic patient distance to film/sensor adjustment (autofocus), whereby the layer is shifted to correct for a malpositioned patient. Another example is the auto exposure function, which adjusts for underexposure or overexposure settings or areas of increased or decreased density as a result of malpositioning.
The new panoramic machines are robotic in design and controlled by a computer chip. That is, each moving part can be programmed to move independently of other moving parts by a stepper motor. Thus projections that open the interproximal contacts such as found on the ProMax can eliminate the need for bitewings—a tremendous advantage when all of the extra time, cost of materials, and risk of disease transmission associated with intraoral radiography are considered. Because the ProMax boasts a resolution of nearly 10 lp/mm, the sharpness and detail now approach those of many intraoral machines, especially those that have been in use for a few years. There are no infection control considerations for the operator in panoramic radiology, and the contaminated bite-block or bite-block sleeve is removed by the patient. Typic/>