Which technique reduces the radiation dose to the patient by reducing the irradiated tissue volume?

• A. Beam collimation
• B. Longer exposure time
• C. Higher kVp
• D. Increased mA

Answer: (A)

Focusing the X-ray beam to the exact area of interest is the main idea here. Beam collimation narrows the field so only the necessary tissue receives radiation, which directly reduces the amount of tissue irradiated and the amount of scatter produced. This targeted exposure lowers the patient’s dose and also improves image quality by reducing ambient scatter.

Longer exposure time would increase the total dose because more X-rays are emitted. Higher kVp changes penetration and can reduce the skin entrance dose for a given image receptor exposure, but it doesn’t limit how much tissue is irradiated, just how the X-rays behave. Increased mA raises the number of photons and thus increases dose, again without changing the irradiated tissue volume.