Optimization of keV-settings in abdominal and lower extremity dual-source dual-energy CT angiography determined with virtual monoenergetic imaging

Abstract

ObjectivesTo compare objective image quality indices in dual-energy CT angiography (DE-CTA) studies of the abdomen and lower extremity using conventional polyenergetic images (PEIs) and virtual monoenergetic images (MEIs) at different kiloelectron volt (keV) levels. MethodsWe retrospectively evaluated 68 dual-source DE-CTA studies. 50 patients (42 men, 71±10 years) underwent abdominal DE-CTA. 18 patients (13 men, 67±10 years) underwent lower extremity DE-CTA. MEIs from 40 to 120keV were reconstructed. Signal intensity, noise, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were assessed in infrarenal aorta, superior mesenteric, external iliac, femoral, popliteal, and lower leg arteries. Comparisons between MEIs and PEIs were performed with Dunnett's test. Results222 arteries were evaluated. In abdominal arteries 70keV MEIs showed statistically equal signal intensity, noise and CNR levels (+13%; +31%, −14% on average; all p>0.05) compared to PEIs; SNR was equal or slightly impaired (−7% on average; p<0.001–1.00). In lower extremity arteries 60keV MEIs resulted in significantly higher signal intensity and CNR (+54%; +54% on average; all p<0.05) compared to PEIs at equal noise levels (+18% on average; all p>0.05) and equal or higher SNR (+49% on average; p<0.01–0.35). ConclusionsLow-keV MEIs lead to equal or higher signal intensity and CNR compared to PEIs. In lower extremity DE-CTA, additional reconstruction of low-keV MEIs at 60keV might increase diagnostic confidence.