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Cardiac application of dual-layer spectral CT

Abstract
Philips CT Clinical Science Philips Healthcare • USA

Prof. Yining Wang, MD

Peking Union Medical College Hospital

Beijing

China

yiningpumc@163.com

 

We investigated the cardiac applications of dual-layer spectral detector CT, including the radiation dose and image quality of coronary CT angiography (CCTA), contrast medium optimization, coronary stenosis with heavy calcified plaque, myocardial perfusion defect with monochromatic imaging, iodine and effective anatomic number quantification technique. The aim of this presentation is to share with you our preliminary results of those studies.

 

Low radiation dose coronary CT angiography with 30 ml contrast medium

Thirty patients with suspected ischemic heart disease underwent CCTA on a dual-layer spectral detector CT using step-and-shoot mode and 30 ml contrast medium injection protocol. The conventional and monochromatic 50 keV images were reconstructed. The attenuation, noise and SNR were significantly better on monochromatic images than those on conventional images (all P < 0.01). The dose length product and effective dose were 142.9 ± 44.7 mGy.cm, and 2.0 ± 0.6 mSv (conversion factor k = 0.014). The monochromatic 50 keV images provide good diagnostic image quality with 30 ml contrast medium and 2 mSv radiation dose in CCTA study. It is feasible to apply spectral imaging in CCTA study with low dose of contrast medium and radiation.

 

Coronary stenosis with heavy calcification

Seventeen patients underwent CCTA and invasive coronary angiography (ICA). CCTA images were acquired on a dual-layer spectral detector CT. Monochromatic images from 50 to 150 keV with 10 keV increment were reconstructed. The degree of each coronary stenosis was quantitatively measured at all keV levels. The best keV was defined at which the stenosis degree was close to the result of ICA. We concluded that when using the best keV image, the mean and standard deviation for the difference of stenosis grade between monochromatic image and ICA was 0.35% ± 1.60%. While using conventional images, the mean and standard deviation for the difference of stenosis grade between conventional image and ICA was 7.9% ± 5.4%. The difference of conventional image was significantly larger than that of the best keV images using ICA as the reference (P < 0.001).

 

Evaluation of myocardial perfusion defect by iodine and effective Z

Twenty-one patients with coronary heart disease underwent CCTA and SPECT within a week. Eleven patients underwent rest SPECT myocardial perfusion and ten patients underwent stress SPECT myocardial perfusion. CCTA images were reconstructed to iodine density, Z effective and conventional CT images. Our results showed Iodine density and Z effective image had similar sensitivity and specificity using rest SPECT (sensitivity 53%, specificity 92%) or stress SPECT (sensitivity 35%, specificity 91%) as reference, which was higher than conventional images (rest SPECT, sensitivity 31%, stress SPECT, sensitivity 25%).

Figure 1a
Figure 1a

Conventional CT image does not clearly show the coronary lumen and plaque due to calcification artifact.

 

Figure 1b
Figure 1b

Mono E 80 keV and Mono E 90 keV images clearly show coronary lumen with less calcification artifact and better delineation between hypodense plaque and calcified plaque.

 

Figure 2
Figure 2
Spectral CT images (iodine density map, Z effective image and fusion map) show myocardial hypo-perfusion (S1) whereas conventional CT image shows normal myocardial perfusion (Helical, 120 kV, DRI 30, Reconstruction: Spectral Level 3).


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Abstract
IntelliSpace Portal, IQon Spectral CT
13th MDCT Users Meeting abstracts, artifacts, calcified plaque, Cardiac, coronary angiography, dose, Effective Z, image quality, iodine density, MonoE, myocardial perfusion, spectral CT, stenosis, Step & Shoot, Vascular
 

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