VALIDITY OF THE PARALLAX METHOD WITH A COMBINATION OF IMAGING RECEPTORS – A REVISIT

To determine the amount of displacement of a structure noticed on an image when the tube of a dental X-ray machine was shifted vertically and horizontally. In addition, various intraoral images were combined with dental panoramic images to determine the location of structures. Our research is based on the parallax technique which requires manipulation of horizontal and vertical angulations of the X-ray tube. A metal object is positioned on the buccal and palatal side of the maxilla on the canine area of a skull. The X-ray tube is shifted incrementally to obtain images on phosphor plates. Subsequently, panaromic and occlusal images were taken to assist in localization of the metal object. To obtain a clear image shift of 2-3mm using the parallax method, there must be an adequate horizontal tube shift of approximately 30-35 degrees. When images were used in combination of dental panoramic images, it was found that the buccally placed structures can be accurately located with the periapical or occlusal images. However, the displacement of images in the palatally placed structures in panoramic imaging is not fully appreciated with the principle of parallax method. Tube movement of 30-35 degrees horizontally is needed for a 2-3 mm image shift. To successfully localize a buccal structure, a combination of either periapical or occlusal images with a dental panoramic imaging can be employed. However, this combination with panoramic imaging is limited when looking at palatally placed structures.