What is the primary purpose of using a grid in radiography?

• A. Improve contrast by reducing scatter
• B. Correct beam alignment
• C. Increase patient dose
• D. Reduce focal spot size

Answer: (A)

The grid’s purpose is to improve image contrast by reducing scatter radiation that reaches the image receptor. Scatter produced inside the patient travels in many directions and adds a level of fog to the image, lowering the visibility of anatomy. The grid uses lead strips to absorb scatter as it travels between the patient and the detector, while most of the primary photons travel in a relatively direct path and pass through to form the image. Using a grid, especially with a higher grid ratio, enhances contrast because more scatter is removed. However, because the grid also absorbs some primary photons, you often need more exposure (higher mAs) to maintain brightness. The grid isn’t about correcting beam alignment or changing focal spot size; its main job is to increase contrast by cuttin down on scattered radiation.