To minimize patient exposure in digital radiography (DR), which of the following practices is most effective?

• A. High kVp, low mAs
• B. Low kVp high mAs
• C. High mAs low kVp
• D. Low mA with long exposure

Answer: (C)

In digital radiography, the key to minimizing patient exposure is delivering the necessary image quality with the smallest dose possible. The most effective way to do this is to use a higher kVp and a lower mAs. A higher kilovoltage beam is more penetrating, so it passes through the patient with less energy being deposited in tissues on average. By reducing the tube current-exposure factor (mAs), you emit fewer photons overall, which further lowers the dose. Digital detectors tolerate these changes well and, with post-processing, can maintain diagnostic quality even when image contrast is somewhat reduced. So, selecting a high kVp while keeping mAs as low as is clinically acceptable is the best strategy to keep patient dose down without sacrificing the ability to make an accurate diagnosis.