What is streak artifacts in CT scan?
Streak artifacts from high attenuation objects are a common problem in CT. This type of artifacts typically occurs from metallic implants such as dental fillings, hip prostheses, implanted marker bins, and branchy-therapy seeds.
How many types of artifacts are there in CT scan?
Artifacts are commonly encountered in clinical computed tomography (CT), and may obscure or simulate pathology. There are many different types of CT artifacts, including noise, beam hardening, scatter, pseudoenhancement, motion, cone beam, helical, ring, and metal artifacts.
What causes ring artifact on CT?
Ring artifacts are a CT phenomenon that occurs due to miscalibration or failure of one or more detector elements in a CT scanner. Less often, it can be caused by insufficient radiation dose or contrast material contamination of the detector cover 2.
What causes streak artifact?
Most streak artifacts occur near materials such as metal or bone, primarily as a result of beam hardening and scatter. These phenomena produce dark streaks between metal, bone, iodinated contrast, barium, and other high-attenuation materials.
What causes the edge gradient effect?
The exponential edge-gradient effect must arise in any x-ray transmission CT scanner whenever long sharp edges of high contrast are encountered. The effect is non-linear and is due to the interaction of the exponential law of x-ray attenuation and the finite width of the scanning beam in the x-y plane.
How do artifacts reduce streaks?
Streak artifacts can sometimes effectively be reduced by increasing tube voltage (better penetration of high-density objects), or by using a dual-energy imaging approach.
How do you avoid artifacts in Connecticut?
Design features incorporated into modern CT scanners minimize some types of artifacts, and some can be partially corrected by the scanner software. However, in many instances, careful patient positioning and optimum selection of scanning parameters are the most important factors in avoiding CT artifacts.
How do you stop the ring artifact?
The ring artifact seen in trans-axial image was caused by contrast contamination of CT tube aperture. Proper fitting of Mylar window and avoidance of contrast leakage can avoid this occurrence.
How do you lower the ring artifact?
There are a number of different methods to reduce these ring artifacts, e.g., hardware modification [3], flat-field correction [4], and signal processing in sinogram domain [5–7].
What causes spiral interpolation artifacts?
The artifacts occur when anatomic structures change rapidly in the z direction (eg, at the top of the skull) and are worse for higher pitches. If a helical scan is performed of a cone-shaped phantom lying along the z axis of the scanner, the resultant axial images should appear circular.
What is edge gradient artifact?
The edge gradient effect result in streak artifact or shading (both light and dark) arising from irregularly shaped object that have a pronounced difference in density from surrounding structures. A common clinical example is artifacts that result when barium and air lie adjacent to each other in the stomach.
What is photon starvation?
Photon starvation is one source of streak artifact which may occur in CT. It is seen in high attenuation areas, particularly behind metal implants. Because of high attenuation, insufficient photons reach the detector.