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Optimization of Z-Axis Automatic Exposure Control for Multidetector Row CT Evaluation of Neck and Comparison with Fixed Tube Current Technique for Image Quality and Radiation Dose

S. Namasivayama, M.K. Kalraa, K.M. Pottalaa, S.M. Waldropa and P.A. Hudginsa

a From the Department of Radiology, Emory University Hospital, Atlanta, Ga


Figure 1
Figure 1
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  		Fig 1. Graphs illustrate schematic representations of the modulation of tube current (A) and, hence, tube current-time product (mA · s) (B) with body region along z-axis in automatic exposure control (AEC) technique (continuous lines in A and B). Tube current and tube current-time products in fixed current technique is shown for comparison as dotted lines in A and B, respectively. Radiation dose (mA · s) with AEC is less than that with fixed current in all section positions along z-axis.


Figure 2
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  		Fig 2. Multidetector row CT evaluation of extracranial head and neck. Transverse image through upper neck using fixed current (A), z-axis automatic exposure control (AEC) with noise index 8 (B), and noise index 10 (C). The subjective noise and diagnostic acceptability of the 3 techniques are comparable.


Figure 3
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  		Fig 3. Multidetector row CT evaluation of extracranial head and neck. Transverse image at the level of shoulders using fixed current (A), z-axis automatic exposure control (AEC) with noise index 8 (B), and noise index 10 (C). The subjective noise and diagnostic acceptability of the 3 techniques are comparable.


Figure 4
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  		Fig 4. Multidetector row CT evaluation of extracranial head and neck. Transverse CT images of fixed current (A) and z-axis automatic exposure control (AEC) with noise index 8 (B) and noise index 10 (C) at the level of the shoulders, illustrating suboptimal subjective noise and diagnostic acceptability.





Copyright © 2009 by the American Society of Neuroradiology. Print ISSN: 0195-6108 Online ISSN: 1936-959X