What happens if grid-focus decentering occurs during an x-ray exposure?

When grid-focus decentering occurs during an x-ray exposure, the image density is affected primarily at the edges of the image, leading to a noticeable decrease in density toward those areas. This phenomenon occurs due to the misalignment between the x-ray tube and the grid, which is designed to filter out scatter radiation. When the grid is not properly aligned with the beam (which can happen if the angle or distance is incorrect), it becomes less effective in absorbing scattered x-rays, resulting in uneven image density.

The central area of the image typically receives more exposure because the primary x-rays travel directly through the grid, while the edges may have less exposure due to their angular relationship to the grid. This decentering effect creates a gradient in image density, which manifests as darker central areas and progressively lighter edges, thus producing the characteristic decreased density toward the edges of the image. This understanding is crucial for radiologic technologists and radiologists as it highlights the importance of proper alignment and positioning to ensure high-quality imaging.