Validation of quantitative aortic valve calcification assessment by photon-counting computed tomography from contrast-enhanced data sets using virtual non-contrast reconstructions

Susanne Jung (Erlangen)1, F. Weidinger (Erlangen)1, F. Ammon (Erlangen)1, M. Moshage (Erlangen)1, S. Smolka (Erlangen)1, R. Janka (Erlangen)2, M. Marwan (Erlangen)1, S. Achenbach (Erlangen)1

1Universitätsklinikum Erlangen Medizinische Klinik 2 Erlangen, Deutschland; 2Universitätsklinikum Erlangen Radiologisches Institut Erlangen, Deutschland


The spectral information of photon-counting computed tomography (PCCT) permits the reconstruction of energy-selective images. We evaluated two methods for the reconstruction of virtual non-contrast-enhanced images from contrast-enhanced CT angiographic data sets regarding their ability to quantify aortic valve calcification. Results were validated by comparison to non-enhanced computed tomography.
A total of 100 subjects with severe aortic valve stenosis who underwent ECG-synchronized cardiac photon-counting CT (PCCT, Naeotom Alpha, Siemens Healthineers) for diagnostic workup prior to transcatheter aortic valve implantation (TAVI) were included in the current analysis. A standard true non-contrast (TNC) acquisiton was performed for aortic valve calcium quantification in each subject. In addition, two virtual non-scans were reconstructed from contrast-enhanced CT angiographic data: a calcium-specific image (“pure calcium scan”, PC scan) and a virtual non-contrast (VNC) scan by subtraction of iodine. The PCS algorithm separates calcium and iodine in spectral PCCT images, creating a noncalcium mask for denoised spectral input and preserving calcium contrast in final material decomposition. Iodine extraction is achieved by measurement of the iodine content and its differentiation from native soft tissue attenuation. The Agatston Score was assessed in each of the three image data sets using semi-automated software (syngo.via).
The mean age of the subjects was 78 ± 7 years, 66% were male. Mean EUROSCORE II was 4 ± 4%, mean STS Score for morbidity and mortality was 16 ± 11%. In the TNC data sets, the mean Agatston Score was 3028 ± 1820. The mean Agatston Score obtained from the PC scan was 3004 ± 2042 and did not differ significantly from the TNC scan (p=0.716). In the VNC scan, the mean Agatston score was 1726 ± 1288, significantly lower than in the TNC and the PC scan (both <0.001). Both, PC and VNC scans showed a significant correlation with TNC scans (correlation coefficient PC scan: 0.978, VNC scan: 0.975, both p<0.001).
In conclusion, the current results show limited diagnostic value of virtual non-contrast scans regarding the quantification of aortic valve calcification. Nevertheless, creation of calcium-specific images using energy-selective reconstructions, seem to be a reliable alternative in order to extract information on calcium quantity from contrast-enhanced data sets.
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