CAMRT Radiography Practice Exam

What grid error is indicated if the center of the image is adequate but the periphery is light?

1. Grid misalignment

2. Upside-down grid

3. Incorrect focal distance

4. Dirty grid

The correct answer is: Upside-down grid

In the situation where the center of the image appears adequate while the periphery is lighter, it suggests that an upside-down grid is likely at play. An upside-down grid will prevent the x-ray photons from being properly transmitted through the peripheral areas of the image receptor, resulting in a noticeable decrease in exposure around the edges. The center may still receive adequate exposure because the x-ray beam is more centered, allowing some photons to penetrate effectively. In contrast, grid misalignment usually leads to uneven exposure without the distinct pattern of a lighter periphery compared to the center. Incorrect focal distance typically results in a global underexposure or overexposure across the entire image rather than a differential exposure pattern. A dirty grid may lead to artifacts and less overall image quality, but it would not specifically cause the described effect of a good center and light periphery. Therefore, identifying an upside-down grid helps pinpoint the specific issue affecting image quality in this scenario.