Which of the following is NOT an advantage of correct collimation?

• A. Decreased patient dose
• B. Improved image contrast
• C. Reduced field size
• D. Longer exposure time

Answer: (D)

Controlling the size and shape of the x-ray beam focuses irradiation on the area of interest, which reduces unnecessary tissue exposure and cuts down on scatter that can fog the image. Because fewer photons interact with non-essential tissues, the patient receives a smaller dose and the image quality improves. The reduced field size also means the image receptor captures fewer scattered photons, which enhances contrast and detail in the region of interest. However, extending the exposure time prolongs how long the patient is exposed to radiation and can increase motion blur and overall dose, so it is not an advantage of proper collimation. In practice, collimation often allows you to achieve the needed receptor exposure with shorter or equal exposure times and lower dose.