Korean J Radiol.  2016 Jun;17(3):321-329. 10.3348/kjr.2016.17.3.321.

Virtual Non-Contrast CT Using Dual-Energy Spectral CT: Feasibility of Coronary Artery Calcium Scoring

• Song I
• Yi JG
• Park JH
• Kim SM
• Lee KS
• Chung MJ

• KMID: 2451407
• DOI: http://doi.org/10.3348/kjr.2016.17.3.321

Abstract

OBJECTIVE
To evaluate the feasibility of coronary artery calcium scoring based on three virtual noncontrast-enhanced (VNC) images derived from single-source spectral dual-energy CT (DECT) as compared with true noncontrast-enhanced (TNC) images.
MATERIALS AND METHODS
This prospective study was conducted with the approval of our Institutional Review Board. Ninety-seven patients underwent noncontrast CT followed by contrast-enhanced chest CT using single-source spectral DECT. Iodine eliminated VNC images were reconstructed using two kinds of 2-material decomposition algorithms (material density iodine-water pair [MDW], material density iodine-calcium pair [MDC]) and a material suppressed algorithm (material suppressed iodine [MSI]). Two readers independently quantified calcium on VNC and TNC images. The Spearman correlation coefficient test and Bland-Altman method were used for statistical analyses.
RESULTS
Coronary artery calcium scores from all three VNC images showed excellent correlation with those from the TNC images (Spearman's correlation coefficient [ρ] = 0.94, 0.88, and 0.89 for MDW, MDC, and MSI, respectively; p < 0.001 for all pairs). Measured coronary calcium volumes from VNC images also correlated well with those from TNC images (ρ = 0.92, 0.87, and 0.91 for MDW, MDC, and MSI, respectively; p < 0.001 for all pairs). Among the three VNC images, coronary calcium from MDW correlated best with that from TNC. The coronary artery calcium scores and volumes were significantly lower from the VNC images than from the TNC images (p < 0.001 for all pairs).
CONCLUSION
The use of VNC images from contrast-enhanced CT using dual-energy material decomposition/suppression is feasible for coronary calcium scoring. The absolute value from VNC tends to be smaller than that from TNC.

Keyword

Coronary artery disease; Computed tomography; Dual energy

MeSH Terms

Aged
Aged, 80 and over
Algorithms
Body Mass Index
Calcium/analysis/*metabolism
Coronary Vessels/*diagnostic imaging
Female
Humans
Image Interpretation, Computer-Assisted
Iodine/analysis/metabolism
Male
Middle Aged
Prospective Studies
Reproducibility of Results
Tomography, X-Ray Computed/instrumentation/*methods
Calcium
Iodine

Figure

• 

  Fig. 1 Reconstructed images of corresponding axial 2.5-mm sections of heart in 70-year-old man. A. True noncontrast-enhanced image used as reference standard shows calcification in left anterior descending coronary artery (arrow). B. Material density iodine-calcium pair image shows coronary plaque (arrow) having similar size as in reference image (A). C. Material density iodine-water pair image shows coronary plaque (arrow) having similar size as in reference image (A). D. Material suppressed iodine image also depicts clearly calcification (arrow) but looks smaller than in reference image (A).

• 

  Fig. 2 Scatter-plots of CAC scores (A) and volumes (B) from TNC images and VNC images. A. Association between coronary artery calcium (CAC) scores from virtual noncontrast-enhanced (VNC) images and those from TNC images evaluated by calculation of Spearman's correlation coefficients. Scatter-plots show excellent correlation between CAC scores from VNC images and those from TNC images (Spearman's correlation coefficient [ρ] = 0.935, 0.875, and 0.890 for MDW, MDC, and MSI, respectively; p < 0.001 for all pairs). B. Association between CAC volumes from VNC images and those from TNC images. Scatter-plots show excellent correlation between CAC volumes from VNC images and those from TNC images (ρ = 0.923, 0.865, and 0.906 for MDW, MDC, and MSI, respectively; p < 0.001 for all pairs). MDC = material density iodine-calcium pair, MDW = material density iodine-water pair, MSI = material suppressed iodine, TNC = true noncontrast-enhanced

• 

  Fig. 3 Bland-Altman plots of CAC scores between TNC image and MDW (A), MDC (B), MSI (C) images. Mean CAC score from TNC image and VNC images is plotted against difference between two methods. solid blue line = mean difference (bias) between two measurements, dashed green lines = 95% confidence intervals for that difference, dashed red lines = limits of agreement between two measurements. CAC = coronary artery calcium, MDC = material density iodine-calcium pair, MDW = material density iodine-water pair, MSI = material suppressed iodine, TNC = true noncontrast-enhanced, VNC = virtual noncontrast-enhanced

• 

  Fig. 4 Bland-Altman plots of CAC volumes between TNC image and MDW (A), MDC (B), MSI (C) images. Mean CAC volume from TNC image and VNC images is plotted against difference between two methods. solid blue line = mean difference (bias) between two measurements, dashed green lines = 95% confidence intervals for that difference, dashed red lines = limits of agreement between two measurements. CAC = coronary artery calcium, MDC = material density iodine-calcium pair, MDW = material density iodine-water pair, MSI = material suppressed iodine, TNC = true noncontrast-enhanced, VNC = virtual noncontrast-enhanced

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