What type of AEC utilizes a fluorescent screen to terminate the exposure?

• A. Ionization Chamber Type
• B. Photomultiplier/Phototimer Type
• C. Digital Radiography Type
• D. Film-Screen Type

Answer: (B)

The photomultiplier/phototimer type of AEC (Automatic Exposure Control) system utilizes a fluorescent screen to terminate the exposure. This type of AEC works by converting the radiation that exposes the patient and the image receptor into light. When the x-rays strike the fluorescent screen, it emits light, which is then detected by a photomultiplier tube. This tube amplifies the light signal, which eventually triggers the termination of the exposure when a predetermined amount of radiation has been reached.

This method allows for precise control over exposure times and ensures that the resulting images are of high quality with optimal contrast and detail. The photomultiplier/phototimer type is particularly effective in scenarios where quick and accurate exposure termination is necessary, making it valuable in radiographic procedures.

In contrast, the other types of AEC systems operate based on different principles, such as measuring ionization or using electronic sensors, and do not involve the conversion of x-rays to light for exposure termination.