What does upside-down grid cutoff demonstrate?

An upside-down grid cutoff typically demonstrates that both sides of the image are underexposed. This phenomenon occurs when a radiographic grid, which is designed to reduce scatter radiation and improve image contrast, is improperly oriented. When the grid is upside down, it can absorb too much of the primary radiation while allowing scatter to affect the final image.

As a result, what you see is a significant reduction in exposure on both sides of the radiograph, leading to underexposed areas. The central region of the image may appear somewhat better, depending on how much grid material is intercepting the primary beam in the center compared to the edges. However, the crucial point is that the malfunction creates an overall underexposure on both lateral sides, confirming the outcome described.