The grid ratio is expressed as:

The grid ratio is defined as the relationship between the height of the lead strips and the space between those strips. This ratio is significant in radiology because it indicates how effectively a grid can reduce scatter radiation while allowing useful rays to pass through to the detector. A higher grid ratio typically means that there are taller lead strips compared to the interspace material, which means that the grid is more effective at blocking scatter.

Understanding this ratio is crucial for selecting and utilizing grids properly in imaging, as higher grid ratios allow for better image quality by reducing the amount of scatter, but they may also require more precise alignment and higher exposure due to the increased absorption of primary rays. Like in the question, this ratio does not involve the number of lead strips or their density, which are different aspects of grid design and utilization.