CAMRT Radiography Practice Exam

If an MRT changes the grid ratio from 5:1 to 12:1 without adjusting technical factors, what effect will this have on the image?

1. Not be affected

2. Demonstrate spatial resolution

3. Have a decreased EI

4. Have an increased EI

The correct answer is: Have a decreased EI

When an MRT changes the grid ratio from 5:1 to 12:1 without adjusting technical factors, the image will likely exhibit a decreased exposure index (EI). This occurs because a higher grid ratio is more effective at reducing scatter radiation, which is undesirable in radiography as it can degrade image quality. With a grid ratio of 12:1, the grid is designed to absorb more of the scatter compared to a 5:1 grid. However, if the technical settings, such as the milliampere-seconds (mAs) or kilovoltage peak (kVp), remain unchanged, the overall exposure to the detector is diminished due to the greater amount of absorbed scatter by the higher ratio grid. Consequently, this results in less exposure reaching the image receptor, leading to a decrease in the EI value that reflects the extent of exposure received by the detector. This demonstrates the importance of adjusting technical factors to compensate for changes in grid ratio to maintain optimal exposure levels and image quality.