Which statement is true according to image processing principles?

• A. The look-up table is unique for each anatomical part
• B. The Nyquist theorem states sampling frequency must be less than twice input frequency
• C. Shuttering reduces exposure to patient
• D. Automatic rescaling is used for underexposure

Answer: (A)

In digital imaging, the data from a detector are transformed into display values through a look-up table, and this mapping can be tailored to the anatomy being imaged to optimize contrast for that part. Different anatomical regions have distinct gray‑scale distributions and diagnostic needs, so using a LUT designed or chosen for a specific part enhances visibility of relevant structures (for example, emphasizing soft tissue details or bone contrast). That makes the idea of a unique LUT for each anatomical part the best choice.

The Nyquist principle actually says that the sampling frequency must be at least twice the highest frequency in the signal to avoid aliasing, so claiming it must be less than twice is incorrect. Shuttering is a hardware dose‑reduction technique, not a principle of image processing. Automatic rescaling adjusts the image appearance to compensate for exposure variations, but it isn’t defined as being limited to underexposure alone.