Which of the following is a CT dose optimization feature?

• A. Lower mA
• B. Automatic exposure control
• C. Iterative reconstruction
• D. Increased scan length

Answer: (C)

Dose optimization in CT aims to keep diagnostic image quality while using as little radiation as possible. Iterative reconstruction directly supports this by improving image quality when dose is reduced. It works differently from traditional reconstruction: instead of directly converting raw data to an image in one pass, it starts with an initial image and repeatedly refines it. Each cycle uses models of how X-rays travel through the body, how noise behaves, and the scanner's physics to compare what the projection data should look like with what was actually measured. By reconciling these differences over multiple iterations, it suppresses noise and artifacts more effectively than basic methods. That means you can lower the tube current (and thus the dose) and still achieve a diagnostically acceptable image, or even better image quality at the same dose.

Lowering tube current alone reduces dose but often degrades image quality due to increased noise. Automatic exposure control adjusts the dose along the scan to match patient attenuation, which is useful for dose management but does not inherently enhance image quality through reconstruction. Increasing scan length raises dose rather than optimizes it. So, iterative reconstruction stands out as a true dose-optimization feature because it enables meaningful dose reduction without sacrificing diagnostic clarity.