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

• A. To convert X-rays
• B. To increase receptor exposure
• C. To absorb scatter and improve image contrast
• D. To reduce resolution

Answer: (C)

Grids are used to improve image contrast by absorbing scattered radiation before it reaches the image receptor. When X-rays pass through the patient, some photons scatter in many directions; those scattered photons reach the detector and wash out details, lowering contrast. The grid, with lead strips and radiolucent gaps, preferentially absorbs much of this scatter, allowing mainly the useful primary photons to form the image, which makes structures stand out more clearly. Because some primary photons are also absorbed by the grid, technique often needs to be increased to maintain adequate receptor exposure.

Grids do not convert X-rays, they do not increase receptor exposure by themselves, and their primary purpose is not to alter resolution (though grid alignment is important to avoid artifacts).