What is off-center exposure or off-level grid error and how does it appear on radiographs?

• A. Uniform density across the image.
• B. Increased sharpness across the image.
• C. Uneven density with one side lighter or darker due to grid cutoff.
• D. Decreased noise across the image.

Answer: (C)

Off-center exposure or off-level grid error is about misalignment between the x-ray beam and the grid. When the central ray isn’t centered on the grid or the grid isn’t parallel to the image receptor, the grid absorbs more of the primary beam in parts of the field. That creates grid cutoff, meaning less exposure reaches the receptor in those areas.

On the radiograph this shows up as uneven density across the image, with one side being lighter (less exposure) than the other. You’ll often see a shading effect toward the edge that’s affected by the grid cutoff. To prevent it, realign the beam to the grid and keep the grid level and centered with the patient and receptor.