[Comparison of input grey values and contrast profiles: a contribution to the discussion on optimization of...

On comparing the individual imaging stages in conventional and digital image radiography it becomes evident that a significant advantage of the digital method is the possibility to adapt the image character and exposure dose individually to various problems requiring an answer. To take advantage of this it is imperative to optimise image processing with care, especially contrast processing. No systematic procedure based on objective criteria had existed to date. This paper describes a method of taking into account both the diagnostic significance of the structures to be imaged and their distribution within the relevant density range, in order to arrive at the best possible contrast conversion. A prerequisite is to know for every kind of imaging which distribution of grey values pertaining to the relevant structures can be expected before digital image processing (initial grey values). This distribution determines the most favourable contrast conversion. The processing parameters for several types of imaging were optimised by this method. The method is demonstrated via thoracic images of newborn and children.