Which of the following is NOT a factor affecting contrast resolution?

• A. Tissue attenuation
• B. Observer
• C. Flat panel detector
• D. Display

Answer: (C)

Contrast resolution is the ability to distinguish small differences in gray levels on an image. What changes the perceived contrast are how differently tissues attenuate the X-ray beam (which creates the actual differences in signal), how well the observer can discern shades with the eye, and how faithfully the display system renders those shades with appropriate brightness and contrast. The detector’s role is to capture and convert the X-ray signal into digital data, influencing noise and dynamic range more than the number of perceivable gray levels. In this sense, while the detector affects overall image quality, it does not directly set the number of distinguishable gray levels seen on the display. So the flat panel detector isn’t a direct factor in contrast resolution.