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. This chapter provides a broad overview of the causes of some artifacts and presents solutions to avoid or correct them whenever appropriate.
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. The following artifacts are defined in Scrum Process Framework. film artifact artificial images on x-ray films due to storage, handling, or processing. distortion or fuzziness of an image caused by manipulation, such as during compression of a digital file. Recall the discussion in Chapter 3 that explained how a CT image is generated with a larger number of projections (about 1000). Scrum Artifacts provide key information that the Scrum Team and the stakeholders need to be aware of for understanding the product under development, the activities being planned, and the activities done in the project. any artificial product a structure or appearance that is not natural, but is due to manipulation.
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. this a new artefact or not What about self-made artefacts, those that children have made at school, or that individuals have knitted on the bus Clearly we. 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. The definition of an image artifact is not as clearly defined as one might expect.
This chapter provides a broad overview of the causes of some artifacts and presents solutions to avoid or correct them whenever appropriate. 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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