What is the process called that identifies the values of interest in a radiographic histogram?

• A. Histogram analysis
• B. Rescaling
• C. Lookup table (LUT) conversion
• D. Post-processing

Answer: (A)

Determining which pixel values correspond to the actual anatomy in the image is done by histogram analysis. The digital image histogram shows how many pixels fall at each gray level, and histogram analysis identifies the range of gray values that represent the true anatomy—the values of interest. This identification lets the system know which part of the histogram to emphasize so the image can be displayed with correct brightness and contrast.

Once the values of interest are found, the image can be scaled automatically (rescaling) to map that VOI to the display range. The lookup table (LUT) then defines how those gray levels are displayed, and post-processing may further enhance the image.