American Society of Radiologic Technologist (ASRT) Practice Exam

In the air-gap technique, which parameter remains unchanged while the image quality is examined?

1. Sharpness

2. Receptor exposure

3. Contrast

4. Spatial resolution

The correct answer is: Contrast

In the air-gap technique, the key feature is that it utilizes the distance between the patient and the image receptor to reduce scatter radiation, which in turn affects image quality. When examining image quality in this context, the parameter that remains unchanged is contrast. Contrast refers to the difference in density between various parts of the image and is largely influenced by the composition of the tissues being imaged and the inherent properties of the imaging system. While the air-gap technique modifies exposure and distribution of scatter radiation, contrast typically remains stable because it is determined by the nature of the subject being imaged rather than the technical factors used in the imaging process. Other parameters like sharpness, receptor exposure, and spatial resolution could be impacted by the air-gap technique due to changes in the amount of scatter and the distance from the receptor, leading to variability in how these factors influence the overall quality of the image. In contrast, contrast itself remains relatively constant as it primarily represents the inherent characteristics of the objects imaged and their interaction with the radiation.