Artifacts in Multi Slice CT

Artifacts can critically degrade the quality of calculated tomographic (CT) images, sometimes to begin making them diagnostically unusable. To be able to optimize image top quality, it is necessary to understand the reason why artifacts occur and exactly how they can be prevented as well as suppressed. CT artifacts originated from a range of sources. Physics-based items result from the actual processes involved in the acquiring CT data. Patient-based artifacts originate from such factors while patient movement or even the presence of material materials in or even on the patient. Scanner-based items result from imperfections inside scanner function. Helical along with multisection technique artifacts are designed by the image renovation process. Design functions incorporated into modern CT scanning devices minimize some types of items, and some can be in part corrected by the reader software. However, in most cases, careful patient placement and optimum choice of scanning parameters would be the most important factors while we are avoiding CT artifacts.
Thin-slice images refurbished from helical multi-slice CT scans normally display artifacts referred to as windmill artifacts, that arise from not really satisfying the Nyquist trying criteria in the affected person longitudinal direction. Since these tend to be essentially aliasing artifacts, they could be reduced or eliminated by trading away from resolution, either throughout the world (by reconstructing fuller slices) or in the area (by local removing of the strong gradients). Well-known drawback to this approach will be the associated loss in decision. Another approach would be to utilize an x-ray conduit with the capability to modulate the actual focal spot inside z-direction, to effectively help the sampling rate. The work presents a new means for windmill artifact lowering based on total alternative minimization in the image area, which is capable of taking away windmill artifacts yet still time preserving the particular resolution of anatomic houses within the images. This can be a big improvement more than previous reconstruction strategies that sacrifice solution, and it provides pretty much the same benefits as being a z-switching x-ray tube with a more simple impact to the all round CT system.

Julia F. Barrett, MSc and Nicholas Keat, MSc
1From Imaging Performance Assessment of CT Scanners (ImPACT), St George’s Hospital, Blackshaw Rd, London SW17 0QT, England. Presented as an education exhibit at the 2003 RSNA scientific assembly. Received April 5, 2004; revision requested May 7; final revision received August 20; accepted September 1. Both authors have no financial relationships to disclose.