Which practice reduces patient exposure during dental radiography?

• A. Use rectangular collimation
• B. Use circular collimation
• C. Increase exposure time
• D. Decrease film speed

Answer: (A)

The main idea is limiting the size of the X-ray beam to reduce how much tissue is exposed. Rectangular collimation narrows the beam to match the film or sensor size, which significantly lowers the amount of radiation reaching the patient and also reduces scatter that can contribute to dose. This approach typically yields a substantial dose reduction—much more than circular collimation—while still producing a diagnostic image when used with proper technique and appropriate film or sensor speed.

Using circular collimation would expose a larger area, increasing the dose. Increasing exposure time directly raises the amount of radiation the patient receives. Decreasing film speed means more exposure is needed to get a usable image, which also increases patient dose.