Contrast, image count density

Contrast of an image arises from the relative variations in count densities between adjacent areas in the image of an object. Contrast (C) gives a measure of the detectability of an abnormality relative to normal tissue and is expressed as... 

Several factors affect the contrast of an image, namely count density, scattered radiations, type of film, size of the lesion, and patient motion. Each contributes to the contrast to a varying degree. These factors are briefly discussed here. 

Figure 3 represents the values of contrast in hot regions. Different formula is applied to measure the contrast relative to cold regions. Count density was obtained by using the same method as in the case of cold region images. 

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