Objective: The magnification factor of panoramic radiography varies, so this approach is not suitable for measurement of distance, angle, and area. The purpose of the present study was to develop a semi-anatomical phantom that provides the magnification factor for the evaluation of digital panoramic X-ray images.
Materials and Methods: The CT image data from a full-scale plaster model of the skull were used with the rapid prototyping technique using the binder jet method. A sheet-type metal mesh with a 1-mm scale was embedded in the plaster model. A 10 × 10-mm copper plate was bound to the upper and lower anterior and molar tooth areas and the buccolingual bone surface of the mandibular ramus to complete the phantom. A semiconductor detector-type and an imaging plate (IP)-type digital panoramic system was used. The standard positioning based on the canine, midline, and horizontal light beam was applied for the first image, and the phantom was moved anteroposteriorly by 5 mm and horizontally by 10 mm, tilted vertically by 5 and 10 degrees, and rotated by 5 and 10 degrees to take another image. The sizes of the mesh and the copper plate were measured using image software (Osiri X), and the vertical and horizontal magnification factors were calculated on the basis of the actual size.
Results: Regarding the effects of the positional change of the patient's head on the linear measurement, it was revealed that the horizontal dimension had greater effects than the vertical dimension. Changes of the magnification factor of the copper plates attached to the bone surface were larger than those of the mesh embedded in the upper and lower jaws. There were no major differences in the magnification factor among different panoramic machines.
Conclusion: A special semi-anatomical phantom that could be used to evaluate the magnification profile of a panoramic image using the anatomical structure and area in the dentition was developed.
