Which of the following technologist errors is most likely to result in incorrect histogram rescaling and look-up table adjustment?

• A. Using an incorrect patient identification number
• B. Not checking the exposure indicator value
• C. Using incorrect collimation
• D. Processing a knee radiograph as a chest

Answer: (C)

In digital radiography, the image brightness and contrast are set by automatically rescaling the histogram and applying the look-up table based on the data within the collimated field. The histogram is built from the pixel values in the area that was exposed. If the collimation is incorrect, the histogram is generated from the wrong region—either including unexposed margins or excluding part of the anatomy. That distorted histogram leads the system to perform improper rescaling and LUT adjustment, producing an image with suboptimal brightness and contrast for the intended anatomy.

The other options don’t directly change the data the histogram uses. Not checking the exposure indicator value could miss a misexposure, but it doesn’t directly alter how the histogram is formed and how the LUT is applied. Incorrect patient ID is unrelated to image processing, and processing a knee radiograph as a chest would mislabel the study rather than cause the histogram and LUT to be miscalibrated.