American Registry of Radiologic Technologists (ARRT) Practice Exam

In electronic imaging, what do mAs and kV not regulate?

1. Image sharpness

2. Density/brightness and contrast

3. Spatial frequency

4. Image acquisition time

The correct answer is: Density/brightness and contrast

In electronic imaging, mAs (milliampere-seconds) primarily controls the quantity of radiation reaching the detector, which affects the overall brightness or density of the image. kV (kilovolt peak), on the other hand, influences the penetration power of the X-ray beam, which is crucial for contrast. While both mAs and kV play significant roles in determining the density and contrast of the image, they do not directly regulate image sharpness, spatial frequency, or image acquisition time. Image sharpness relates more to factors such as focal spot size, motion, and the quality of the imaging system rather than the radiation exposure settings themselves. Similarly, spatial frequency pertains to the level of detail that can be discerned in an image, which depends on the imaging system's resolution, rather than the settings of mAs or kV. Lastly, image acquisition time is influenced by time factors related to the imaging procedure, such as the duration for which the detector is exposed to radiation, rather than solely by mAs and kV settings. Thus, the correct understanding is that while mAs and kV are critical for controlling density and contrast, they do not inherently regulate sharpness, spatial frequency, or image acquisition time, making the choice