Which modification may decrease the total exposure time when using an automatic exposure control (AEC) system?

In an automatic exposure control (AEC) system, using increased milliamperage (mA) can significantly decrease the total exposure time required to obtain a radiographic image with optimal quality. When the mA is increased, it enhances the X-ray tube's output by generating more X-ray photons per unit of time. This means that the required exposure for a specific image quality can be reached more quickly.

A higher mA results in an improved signal-to-noise ratio, allowing for clearer images without extending the exposure duration. As a consequence, the AEC will terminate the exposure sooner because sufficient radiation has been detected to achieve the needed image quality. Thus, increasing the mA essentially allows the system to complete the exposure in less time while still providing accurate and high-quality imaging.

Reducing the back-up timer or adjusting the density setting can potentially affect the exposure time; however, they may not directly correlate with a guaranteed reduction in exposure duration like increasing the mA does. Decreased kVp affects the quality and penetration of the X-ray beam and typically requires longer exposure times to maintain image quality under lower energy conditions.