The Effect of Patient Diameter on the Dual-Energy Ratio of Selected Contrast-Producing Elements.
OBJECTIVE
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.
From the *Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA; and †GE Global Research, Niskayuna, NY.
Jack W
JW
Lambert
Paul F
PF
FitzGerald
Peter M
PM
Edic
Yuxin
Y
Sun
Peter J
PJ
Bonitatibus
Robert E
RE
Colborn
Benjamin M
BM
Yeh
D000005:Abdomen / Q000000981:diagnostic imaging*; D000273:Adipose Tissue / Q000000981:diagnostic imaging*; D001837:Body Weights and Measures; D019047:Phantoms, Imaging; D014057:Tomography, X-Ray Computed / Q000379:methods*