Common Errors on Panoramic Radiographs Taken in a Dental School

Akarslan ZZ, ErtenH, GungorK, et. al. J Contemp Dent Pract 2003 May;(4) 2:024-034

Review: Rafi Romano D.M.D., M.Sc Israel

 www.lingualnews.com, Volume 1, Number 4 - November 2003

Panoramic radiography is a radiographic technique for producing an image of the facial structures that includes both maxillary and mandibular arches and their supporting structures such as the maxillary antrum, nasal fossa, temporomandibular joint, styloid process, and hyoid bone on a single film.

1 The image is obtained by rotation of the X-ray source and the film, at the same speed in the opposite direction around the head. 
2. With this technique, the X-ray beam passes through the jaws of from lingual to buccal and is directed at a slight upward angulation with respect to the occlusal plane. In order to make a radiograph with a high diagnostic value, the operator must pay careful attention to: 

1. Patient positoning
2. Film processing
3. Film handling procedures.

Proper patient positioning requires the patient's back and spine to be erect with the neck extended, the Frankfurt plane parallel to the floor, and the dental arches and sagital plane positioned within the focal trough of the X-ray unit.

Materials and Methods
A total of 460 panoramic radiographs taken in the Radiology Department with an Orthopantomograph (OP100 Instrumentarium Corporation, Imaging Division, Finland) and developed in a roller transport automatic processor machine (Velopex, England) were evaluated by an experienced radiologist with 13 years experience. The radiographs were evaluated according to the following 20 categories of common errors modified from the Brezden et al. study Results From the evaluated 460 panoramic radiographs taken in the Radiology Department of a dental school in Turkey, 173 (37.61%) were found to have no errors according to the 20 criteria.

The most common positioning error on the radiographs taken by trained asisstants was found to be a radiolucent area palatoglossal airspace  over the roots of the maxillary teeth (46.30%) due to the patient's tongue not being raised against the palate during exposure time. (Fig. 1)

Superimpositon of the hyoid bone with the body of the mandible (26.30%) and superimposition of the vertebral column on to the anterior teeth (22.17%) were the next most common errors. (Figs. 2 & 3) The least seen positioning errors were the widening of the anterior teeth due to the patient biting the bite-block too far back (1.30%) and the vertical overlap of the anterior teeth due to the patient's not biting the bite-block, or not using a bite-block during the exposure (2.39%). On the evaluated radiographs, the most frequent technical errors were too high density (16.52%) and too low density (15.65%), respectively. (Figs. 4 & 5) The least common error was found to be the presence of dirty or  bent films (0.21%). (Fig. 6).

Fig. 1: Palatoglossal airspace over the roots of the maxillary teeth

Fig. 2: Superimposition of the hyoid bone on the body of the mandible

Fig. 3: Vertebral column superimposed over the anterior teeth

Fig. 4: Film density too high

 Fig.  5. Film density too low

Fig. 6. Bent film

Fig. 7: Narrowed anterior teeth, blurred image and occlusal plane is
tipped upward

Discussion

The focal trough of the panoramic X-ray unit is a three dimensional curved zone in which structures are reasonably well defined on the panoramic radiographs, and it is important for obtaining high quality images of the structures of interest.1 The limited dimension of the focal trough, carelessness of operator, and age of the machine affects the occurrence of some errors. The image seen on a panoramic radiograph consists largely of the anatomic structures located within the focal trough. Objects in front or behind it are blurred, magnified or reduced in size, and are sometimes distorted to the extent of being unrecognizable.1,2 (Figure 7) The limited dimensions of the focal trough makes minor errors in positioning to manifest as distortions due to unequal vertical and horizontal magnification, overlapping of teeth, and loss of image sharpness.

Conclusion
From the results of the study, the percentage of error-free radiographs taken by trained radiology assistants was found to be 37.61%. The most common error seen on the radiographs was the palatoglossal airspace. Training of dental personnel and a discussion of technical measures to be taken if errors occur are essential to maximize the quality of panoramic radiographs.