CAMRT Radiography Practice Exam

To evaluate bony structures in a CT image, what would increase the dark appearance of the image?

1. Decrease the window width

2. Decrease the window level

3. Increase the window level

4. Increase the window width

The correct answer is: Increase the window level

To understand how the adjustment of window levels in a CT image affects the appearance of bony structures, it's important to consider what window level and width mean in the context of CT imaging. The window level controls the center of the range of tissue densities displayed in the image, while the window width determines the range of densities that are included. When you increase the window level, you are shifting the center of the grayscale representation to higher density values. Bony structures, which have a high density and therefore appear lighter on CT images, will become less prominent when the window level is elevated. This shift allows less dense tissues, such as surrounding softer tissues or fat, to be evaluated more clearly, resulting in a relatively darker appearance of bony structures. As the relative contrast between the bony areas and adjacent soft tissues diminishes due to this adjustment, the bones appear darker in the visual output. In contrast, decreasing the window level or width would allow for broader range visualization of lower densities, making bones appear lighter. Hence, increasing the window level effectively enhances the visualization of softer tissue at the potential expense of bony detail, which is perceived as a darker appearance on the image.