Introduction to radiological interpretation
To achieve these objectives and maximize the diagnostic yield, interpretation should be carried out under specified conditions, following ordered, systematic guidelines.
Unfortunately, interpretation is often limited to a cursory glance under totally inappropriate conditions. It is easy to fall victim to the problems and pitfalls produced by spot diagnosis and tunnel vision. This is in spite of knowing that in most cases radiographs are the main diagnostic aid.
This chapter provides an introductory approach to show dental care professionals how radiographs should be interpreted, specifying the viewing conditions required and suggesting systematic guidelines.
Fig. 16.1 A Wardray viewing box incorporating an additional central bright-light source for viewing overexposed dark films. B The SDI X-ray reader – an extraneous light excluding intraoral film viewer with built-in magnification.
These ideal viewing conditions give the observer the best chance of perceiving all the detail contained within the radiographic image. With many simultaneous external stimuli, such as extraneous light and inadequate viewing conditions, the amount of information obtained from the radiograph is reduced. Radiographs should be viewed once they have dried as films still wet from processing may show some distortion of the image.
The importance of understanding the nature of different types of radiographic images – film-captured or digital (depending on the type of image receptor used) – and their specific limitations was explained in Chapter 1. How the visual images are created by processing – chemical or computer – was explained in Chapter 3. Revision of both these chapters is recommended. To reiterate, the final image, whether captured on film or digitally, is ‘a two-dimensional picture of three-dimensional structures superimposed on one another and represented as a variety of black, white and grey shadows’ – a shadowgraph.
To be able to assess and interpret any radiograph correctly, dental care professionals have to know what that radiograph should look like and which structures should be shown. It is for this reason that the chapters on radiography included: