Infants and very small children may not be imageable with X-ray equipment utilizing which feature?

• A. Phototimers
• B. Filtration
• C. Gonadal shielding
• D. Collimation

Answer: (A)

Phototimers rely on light transmitted through the patient to decide when to stop the exposure. For very small infants, there is very little tissue to attenuate the beam, so a large amount of light reaches the sensor almost immediately and the exposure can be terminated before enough x-ray photons have reached the image receptor. The result is underexposure and non-diagnostic images. This makes imaging infants with phototimer-equipped equipment unreliable unless manual override or pediatric-tuned exposure settings are used. Filtration, collimation, and shielding affect dose and image quality but do not prevent imaging with such small patients in the same way phototimers can.