Since inaccuracies in the measurements usually manifest themselves as errors in the reconstructed images, the probability of producing an image artifact is much higher for CT.
Because the nature of the backprojection process is to map a point in a projection to a straight line in an image, an error in the projection reading is no longer localized, as is the case for conventional radiography. (In the case of a multislice CT scanner, which will be discussed in Chapter 10, the number of measurements in a single projection can easily be quadrupled.) As a result, nearly 106 independent readings or measurements are used to form an image. In a typical CT system, each projection contains roughly 1000 separate measurements. Recall the discussion in Chapter 3 that explained how a CT image is generated with a larger number of projections (about 1000). This chapter provides a broad overview of the causes of some artifacts and presents solutions to avoid or correct them whenever appropriate. We want to examine only the discrepancies that impact the radiologists' performance.Ĭompared to conventional radiography, CT systems are inherently more prone to artifacts. In practice, we have to limit our discussion to the discrepancies that are clinically significant or relevant as judged by the radiologists. In fact, most pixels in a CT image are âartifactsâ in some shape or form. Although this definition is broad enough to cover nearly all types of nonideal images, it has little practical value since nearly every image produced by a CT scanner contains an artifact by this definition.
Theoretically, an image artifact can be defined as any discrepancy between the reconstructed values in an image and the true attenuation coefficients of the object. Artifacts might be databases, data models, printed documents or scripts. Artifacts are like roadmaps that software developers can use to trace the entire software development process. The definition of an image artifact is not as clearly defined as one might expect. An artifact is a byproduct of software development that helps describe the architecture, design and function of software. They are only differentiated by the communities in which they are used. Word Originearly 19th cent.: from Latin arte by or using art + factum something. Is it artefact or artifact Artefact and artifact are two versions of the same noun. This chapter provides a broad overview of the causes of some artifacts and presents solutions to avoid or correct them whenever appropriate. Oxford Collocations DictionaryArtefact is used after these nouns: museum. In other words, a significant portion of the computation associated with CT image generation is related to the reduction or elimination of image artifacts. Chapter 3 provided a representative flow diagram for the image generation process and stated that the preprocessing and postprocessing steps used to overcome nonideal data collection often outweigh, in terms of the number of operations, âtextbookâ tomographic reconstruction.
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