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X‐ray scattering in single‐ and dual‐source CT
Author(s) -
Engel Klaus J.,
Herrmann Christoph,
Zeitler Günter
Publication year - 2008
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.2820901
Subject(s) - physics , streak , nuclear medicine , optics , scattering , cone beam computed tomography , tomography , scanner , computed tomography , medicine , radiology
For medical imaging applications, such as cardiac imaging, dual‐source computed tomography (CT) improves the temporal resolution by the simultaneous use of two cone beams, which acquire twice as many projections as single‐source CT does within the same time interval. Besides this advantage, a drawback of such a system is additional x‐ray scatter originating from the extra (cross‐illuminating) cone beam. In this work, a comparison with single‐source CT images is performed under same‐dose conditions for two different thorax phantoms, and for different cone beam angles corresponding to a coverage of 20, 40, 80, and 160 mm on the rotation axis ( z coverage). As a general result, the HU‐magnitude of scatter‐induced streak and cupping artifacts scale almost proportional to the illuminated volume. In dual‐source CT, cross scatter induces a further factor of almost 2 in the scaling of artifacts in comparison to single‐source CT. For all examined systems, the scatter‐induced noise reduces the contrast‐to‐noise ratio (CNR). In the case of an ideal scatter correction, the CNR is reduced even more, but contrast and CNR can be restored by an additional x‐ray dose. With a 32‐slice single‐source CT ( z overage of 20 mm) taken as a reference, a corresponding dual‐source CT requires 7 % more dose to maintain the same CNR. A CT system with a z coverage of 40, 80, and 160 mm requires 8 % , 23 % , and 54 % more dose in a single‐source configuration, respectively, and 20 % , 47 % , and 102 % more dose in a dual‐source configuration, respectively. In conclusion, a dual‐source CT is comparable to a single‐source CT with twice the z coverage concerning image degradation by scatter.