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8 March 2007 Performance evaluation of CT-automatic exposure control devices
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Abstract
Technological developments of computed tomography (CT) have led to an increase of its clinical utilization. To optimize patient dose and image quality, scanner manufacturers have introduced X-ray tube current modulation coupled to Automatic Exposure Control (AEC) devices. The purpose of this work was to assess the performance of the CT-AEC of three different MSCT manufacturers by means of two phantoms: a conical PMMA phantom to vary the thickness of the absorber in a monotonous way, and an anthropomorphic chest phantom to assess the response of the CT-AEC in more realistic conditions. Noise measurements were made by standard deviation assessments, and dose indicators (CTDIvol and DLP) were calculated. All scanners were able to compensate for thickness variation by an adaptation of tube current. Initial current adaptation lengths varied for all systems in the range of 1 to 5 cm. With the anthropomorphic phantom, noticeable differences appeared concerning the adaptation rapidity in a sudden X-ray attenuation change, and non-intuitive behavior of current evolution was noticed for some acquisitions. The xyz-modulation allowed to reduce the DLP of the acquisition by 18% compared to the z-modulation. It is also showed that a homogeneous test object is not sufficient to characterize CT-AEC devices.
© (2007) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Daniel Gutierrez, Sabine Schmidt, Alban Denys, Pierre Schnyder, François O. Bochud, and Francis R. Verdun "Performance evaluation of CT-automatic exposure control devices", Proc. SPIE 6515, Medical Imaging 2007: Image Perception, Observer Performance, and Technology Assessment, 65151P (8 March 2007); https://doi.org/10.1117/12.708386
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