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A noise-optimized virtual monochromatic reconstruction algorithm improves stent visualization and diagnostic accuracy for detection of in-stent re-stenosis in lower extremity run-off CT angiography

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To evaluate the impact of noise-optimized virtual monochromatic imaging (VMI+) on stent visualization and accuracy for in-stent re-stenosis at lower extremity dual-energy CT angiography (DE-CTA).

Material and methods

We evaluated third-generation dual-source DE-CTA studies in 31 patients with prior stent placement. Images were reconstructed with linear blending (F_0.5) and VMI+ at 40–150 keV. In-stent luminal diameter was measured and contrast-to-noise ratio (CNR) calculated. Diagnostic confidence was determined using a five-point scale. In 21 patients with invasive catheter angiography, accuracy for significant re-stenosis (≥50 %) was assessed at F_0.5 and 80 keV-VMI+ chosen as the optimal energy level based on image-quality analysis.


At CTA, 45 stents were present. DSA was available for 28 stents whereas 12 stents showed significant re-stenosis. CNR was significantly higher with ≤80 keV-VMI+ (17.9 ± 6.4–33.7 ± 12.3) compared to F_0.5 (16.9 ± 4.8; all p < 0.0463); luminal stent diameters were increased at ≥70 keV (5.41 ± 1.8–5.92 ± 1.7 vs. 5.27 ± 1.8, all p < 0.001) and diagnostic confidence was highest at 70–80 keV-VMI+ (4.90 ± 0.48–4.88 ± 0.63 vs. 4.60 ± 0.66, p = 0.001, 0.0042). Sensitivity, negative predictive value and accuracy for re-stenosis were higher with 80 keV-VMI+ (100, 100, 96.4 %) than F_0.5 (90.9, 94.1, 89.3 %).


80 keV-VMI+ improves image quality, diagnostic confidence and accuracy for stent evaluation at lower extremity DE-CTA.

Key Points

The impact of noise-optimized virtual monochromatic imaging on stent visualization was assessed.

Virtual monochromatic imaging significantly improves stent lumen visualization and diagnostic confidence.

At 80 keV diagnostic performance for detection of in-stent restenosis was increased.

80 keV virtual monochromatic images are recommended for stent evaluation of lower extremity vasculature.

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Contrast-to-noise ratio


CT angiography


CT dose index


Dual-energy CT


Dual-energy CT angiography


Dose-length product


Digital subtraction angiography


Dual-source CT


Linearly-blended images


Hounsfield Units


kilo-electron Volt


Negative predictive value


Positive predictive value


Region of interest


Standard deviation


Signal-to-noise ratio


Virtual monochromatic imaging


Noise-optimized virtual monochromatic imaging


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The scientific guarantor of this publication is Prof. Dr. U. Joseph Schoepf. The authors of this manuscript declare relationships with the following companies: Dr. Schoepf is a consultant for and receives research support from Astellas, Bayer, Bracco, GE, Medrad, and Siemens. The other authors have no conflicts of interest to disclose. The authors state that this work has not received any funding. One of the authors has significant statistical expertise. Institutional Review Board approval was obtained. Written informed consent was waived by the Institutional Review Board.

Some study subjects or cohorts have been previously reported in Wichmann et al. (2016) Dual-Energy CT Angiography of the Lower Extremity Run-off: Impact of Noise-Optimized Virtual Monochromatic Imaging on Image Quality and Diagnostic Accuracy. Invest Radiol. 51(2): 139-46. Methodology: retrospective, cross-sectional study, performed at one institution.

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Correspondence to U. Joseph Schoepf.

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Mangold, S., De Cecco, C.N., Schoepf, U.J. et al. A noise-optimized virtual monochromatic reconstruction algorithm improves stent visualization and diagnostic accuracy for detection of in-stent re-stenosis in lower extremity run-off CT angiography. Eur Radiol 26, 4380–4389 (2016).

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