American Society of Radiologic Technologist (ASRT) Practice Exam

Modern automatic exposure control (AEC) sensors are of which type?

1. Scintillator

2. Ionization chamber

3. Autotransformer

4. Phototimer

The correct answer is: Ionization chamber

Modern automatic exposure control (AEC) sensors predominantly utilize ionization chambers for determining the appropriate exposure time in radiographic imaging. Ionization chambers work by detecting the ionization produced by X-rays as they pass through the chambers. When the radiation exposure reaches a certain predetermined level, the ionization results in an electrical signal that signals the equipment to terminate the exposure, ensuring optimal imaging quality while minimizing patient dose. This technology has become fundamental to achieving consistent and accurate exposure, allowing for better control over image quality. The use of ionization chambers is a significant advancement over older technologies such as phototimers, which relied on light detection rather than direct measurement of ionization. The ionization chamber's ability to provide real-time feedback based on the actual radiation levels contributes to its modern application in AEC systems. The other options, such as scintillators and autotransformers, do not function in the same capacity as AEC sensors. Scintillators are used for converting X-ray photons into visible light for imaging detectors but are not utilized as AEC sensors. Autotransformers serve a different purpose in electrical circuits, specifically for voltage regulation, and are not involved in exposure control processes. Thus, the definition and operational functions of ionization chambers