Performance evaluation of CT-automatic exposure control devices

Daniel Gutierrez; Sabine Schmidt; Alban Denys; Pierre Schnyder; François O. Bochud; Francis R. Verdun

doi:10.1117/12.708386

8 March 2007 Performance evaluation of CT-automatic exposure control devices

Daniel Gutierrez, Sabine Schmidt, Alban Denys, Pierre Schnyder, François O. Bochud, Francis R. Verdun

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Proceedings Volume 6515, Medical Imaging 2007: Image Perception, Observer Performance, and Technology Assessment; 65151P (2007) https://doi.org/10.1117/12.708386
Event: Medical Imaging, 2007, San Diego, CA, United States

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 (CTDI_vol 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.

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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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KEYWORDS

Scanners

Modulation

X-rays

Image quality

Control systems

Signal attenuation

Digital Light Processing

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