What happens to radiographic contrast when the radiation field size is changed from a 14"x17" to an 8"x10"?

When the radiation field size is reduced from a larger area, such as 14"x17", to a smaller area like 8"x10", several factors influence radiographic contrast. The primary effect of decreasing the field size is that it reduces the amount of scatter radiation reaching the image receptor. Scatter radiation is generated when the x-ray beam interacts with matter, and it can reduce the overall contrast of an image by adding unwanted gray tones.

By limiting the area being imaged, a smaller field size effectively minimizes scatter, which enhances the visibility of differences in tissue density and reduces the fogging of the image. This results in an image where the variations in contrast between different structures are more pronounced. As a result, the overall contrast of the radiographic image increases, leading to improved diagnostic quality.

In this context, changing the field size to a smaller one serves to enhance the contrast by making the structural details more distinguishable, thus allowing for clearer assessments and interpretations of the radiographic images.