![]() The biggest problem is when scattered photons end up in a detector that would usually have very few photons. This means photons could end up in a different detector than they should be in. Basically, scatter causes X-ray photons to change direction and change energy. The other big issue that causes streak artifacts is something called Compton scatter. In the same way, X-rays lose their energy, or "harden", more quickly as they pass through metal or bone than as they pass through muscles or organs. And if I’m swimming through water, I expend less energy than if I were swimming through, say, Jell-o. As I swim, I lose energy as I cross the pool I’m more tired the further I go. Here's an analogy to help understand beam hardening: P retend I’m swimming across a pool. I am an X-ray beam and the pool is the part of the body being scanned. See an example of an artifact caused by beam hardening below. ![]() Bright streaks are seen adjacent to the dark streaks 2. These phenomena produce dark streaks between metal, bone, iodinated contrast, barium, and other high-attenuation materials. Most streak artifacts occur near materials such as metal or bone, primarily as a result of beam hardening and scatter. The name should suffice to tell you what a streak artifact looks like, but the causes bear some explanation. In spite of this, CT is commonly susceptible to a number of image anomalies 1, including streak artifacts. The technology is a mainstay in the imaging stables of most hospitals. Generally, images produced by CT scanners are accurate representations of the scanned object.
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