Validity Of The Parallax Method With A Combination Of Imaging Receptors ' A Revisit

ABSTRACT

To determine the amount of displacement of a structurenoticed on an image when the tube of a dental X-raymachine was shifted vertically and horizontally. Inaddition, various intraoral images were combined withdental panoramic images to determine the location ofstructures. Our research is based on the parallaxtechnique which requires manipulation of horizontaland vertical angulations of the X-ray tube. A metalobject is positioned on the buccal and palatal side ofthe maxilla on the canine area of a skull. The X-raytube is shifted incrementally to obtain images onphosphor plates. Subsequently, panaromic and occlusalimages were taken to assist in localization of the metalobject. To obtain a clear image shift of 2-3mm usingthe parallax method, there must be an adequatehorizontal tube shift of approximately 30-35 degrees.When images were used in combination of dentalpanoramic images, it was found that the buccallyplaced structures can be accurately located with theperiapical or occlusal images. However, thedisplacement of images in the palatally placedstructures in panoramic imaging is not fullyappreciated with the principle of parallax method. Tubemovement of 30-35 degrees horizontally is needed fora 2-3 mm image shift. To successfully localize a buccalstructure, a combination of either periapical or occlusalimages with a dental panoramic imaging can beemployed. However, this combination with panoramicimaging is limited when looking at palatally placedstructures.