Quality of virtual-non-contrast phases derived from arterial and delayed phases of fast-kVp switching dual-energy CT in patients after endovascular aortic repair

Abstract

Objective of this study is: to analyze CT numbers in arteries and endoleaks in true non-contrast (TNC) and virtual non-contrast phases derived from arterial (VNCa) and delayed (VNCd) phases of dual-energy CT (DECT) in patients after endovascular aneurysm repair (EVAR); to assess the impact of image noise on subjective image quality parameters and the degree of subtraction of calcifications; to calculate effective dose (ED) reduction following replacement of TNC with VNC. The study included 97 patients after EVAR procedure. An initial single-energy TNC acquisition was followed by two DECT acquisitions. CT numbers of TNC, VNCa, VNCd were analyzed statistically. VNCd images were assessed qualitatively. The mean densities in endoleaks were 46.19 HU in TNC, 51.24 HU in VNCa, 42.24 HU in VNCd. The differences between them were statistically significant (p < 0.05). The mean signal-to-noise ratio (SNR) measured in the aorta and endoleaks was highest in VNCa, lowest in TNC images. No correlation between image noise, the results of qualitative analysis of VNCd, and the degree of subtraction of calcifications was found. Omitting TNC led to mean 6.54 ± 1.63 (SD) mSv (23.28% of total examination) ED reduction. VNC images have a higher SNR compared to TNC images with significant differences in the CT numbers between the TNC and VNC reconstructions. Image noise has no impact on the subjective image quality and the degree of subtraction of calcifications in VNCd images. The findings show a high diagnostic value of VNC images and suggest that VNCd images are optimal in the assessment of endoleaks with possible substantial ED reduction.

Differentiation of Hamartomas and Malignant Lung Tumors in Single-Phased Dual-Energy Computed Tomography

“…Evidence from multiple studies indicates that VNC images acquired during different vascular phases—specifically in the arterial and venous phase—exhibit notably disparate CT values. This variability could compromise the diagnostic reliability of VNC HU values in the post-contrast phase, thereby affecting their ability to accurately differentiate between these lesions [ 45 , 46 ]…”

Dual-Energy and Photon-Counting Computed Tomography in Vascular Applications—Technical Background and Post-Processing Techniques

“…VNC reconstructions are images created by the subtraction of iodine [ 14 ]. Numerous studies have proven that VNC images can substitute for TNC images with sufficient quality [ 15 , 16 , 17 , 18 ].…”

“…Iodine quantification obtained through VNC images can greatly increase diagnostic accuracy in differentiating malignant and bland thrombus in portal vein thrombosis [ 20 ]. VNC images have proven to be reliable in settings of the endoleak assessment in patients after EVAR, with possible radiation dose reduction [ 14 , 21 ]. However, VNC images have been proven prone to the iodine content.…”

“…However, VNC images have been proven prone to the iodine content. This results in differences in attenuation between TNC and VNC reconstructions obtained from various phases of examination [ 14 , 22 ]. Figure 8 presents the differences between TNC and two post-contrast VNC images.…”

Review of Clinical Applications of Dual-Energy CT in Patients after Endovascular Aortic Repair

“…Numerous studies in various clinical settings have proven that VNC images can substitute for TNC images and that the TNC phase of multiphasic examinations can be omitted [12][13][14][15][16]. VNC images have been proven to be vulnerable to iodine content, leading to significant differences in CT numbers between TNC and VNC images derived from arterial and delayed examination phases [17,18]. Figure 5 shows the differences between the TNC and the two postcontrast VNC reconstructions.…”