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The Effect of Patient Diameter on the Dual-Energy Ratio of Selected Contrast-Producing Elements
Jack W Lambert1, Paul F FitzGerald, Peter M Edic
1From the *Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA; and †GE Global Research, Niskayuna, NY.
Objectives:
The aim of this study was to assess whether the low- to high-kVp computed tomography (CT) number ratio at dual-energy CT is affected by changes in patient diameter.
Methods:
Seven contrast-producing elements were housed sequentially within an abdomen phantom. Fat rings enlarged the phantom diameter from 26 to 44 cm. The phantom was scanned using single-energy CT at tube potentials of 80 and 140 kVp and rapid-kVp-switching dual-energy CT.
Results:
CT numbers decreased proportionally (∼20% CT number reduction for smallest to largest phantom diameters) for low- and high-energy acquisitions but resulted in consistent dual-energy ratios for each contrast element. For 17 of 21 material pair combinations, the dual-energy ratio ranges of the two elements did not overlap, implying that discrimination should remain possible for these material pairs at all patient sizes.
Conclusions:
The dual-energy ratio for different contrast materials is largely unaffected by changes in phantom diameter. This should allow for robust separation of most contrast material combinations irrespective of patient size.
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