Introduction

• In diagnostic radiography a beam of X-rays is produced by the appropriate apparatus and caused to impinge on the portion of the patient to be investigated. As the beam passes through the patient it will be absorbed to varying degree by the different tissues encountered and thus on emergence becomes capable of casting " shadowgraph " of the area penetrated.

• This shadow can be visualized by means of a fluorescent screen or recorded on a photographic film. From the picture produced the radiologist attempts to deduce the anatomical structure of the patient, noting in particular any variations from normality and inferring from this the pathological process which is occurring in the part examined.