CAMRT Radiography Practice Exam

As window width increases in a CT image, how does contrast change?

1. Increases

2. Decreases

3. Remains constant

4. Fluctuates

The correct answer is: Decreases

When assessing the relationship between window width and contrast in a CT image, it is important to understand how windowing affects the visualization of different tissue types. Window width refers to the range of CT numbers that are displayed in a specific image. When the window width is increased, a broader range of attenuation values is represented on the grayscale. As the window width increases, more tissue types fall within this broader range of displayed values, which effectively reduces the contrast between different tissues. In other words, when more values are included, the differences between adjacent values (such as those representing fat, soft tissue, and fluid) become less distinct. Therefore, greater window width leads to a decrease in perceived contrast. This relationship is critical for radiographers to understand, as adjusting window width is a common method for optimizing image quality and enhancing visualization of specific structures in a CT scan. The interplay between window width and window level also plays a pivotal role in determining how well different tissues can be differentiated based on their attenuation characteristics.