Which device is used to limit the area of the patient being irradiated?

Which device is used to limit the area of the patient being irradiated?

• A. Lead mask
• B. Collimator
• C. Grid
• D. Compensating filter

Answer: (B)

Limiting the X-ray field to the area of interest is essential to protect the patient and improve image quality. The device that does this is the collimator. It sits at the end of the X-ray tube and uses adjustable lead shutters to shape the beam. A light field projects onto the patient so you can see exactly what area will be exposed, and you can adjust the shutters to match the anatomy you intend to image. By narrowing the beam, only the target region is irradiated, which reduces dose to surrounding tissues and decreases scatter that can blur the image. The other devices have different roles. A grid is placed between the patient and the image receptor to absorb scattered photons, enhancing image contrast but not controlling the beam’s size. A compensating filter adjusts the beam’s intensity to compensate for thickness differences in the body, helping to produce uniform density across the image rather than limiting exposure area. A lead mask isn’t used to define the radiographic field in typical practice; it’s not the tool for shaping the X-ray beam in diagnostic imaging.

Limiting the X-ray field to the area of interest is essential to protect the patient and improve image quality. The device that does this is the collimator. It sits at the end of the X-ray tube and uses adjustable lead shutters to shape the beam. A light field projects onto the patient so you can see exactly what area will be exposed, and you can adjust the shutters to match the anatomy you intend to image. By narrowing the beam, only the target region is irradiated, which reduces dose to surrounding tissues and decreases scatter that can blur the image.

The other devices have different roles. A grid is placed between the patient and the image receptor to absorb scattered photons, enhancing image contrast but not controlling the beam’s size. A compensating filter adjusts the beam’s intensity to compensate for thickness differences in the body, helping to produce uniform density across the image rather than limiting exposure area. A lead mask isn’t used to define the radiographic field in typical practice; it’s not the tool for shaping the X-ray beam in diagnostic imaging.