Virtual Non-Contrast Spectral CT in Renal Masses: Is It Time to Discard Conventional Unenhanced Phase?

Abstract

Dual-layer Dual-Energy CT (dl-DECT) allows one to create virtual non-contrast (VNC) reconstructions from contrast-enhanced CT scans, with a consequent decrease of the radiation dose. This study aims to assess the reliability of VNC for the diagnostic evaluation of renal masses in comparison with true non-contrast (TNC) images. The study cohort included 100 renal masses in 40 patients who underwent dl-DECT between June and December 2021. Attenuation values and standard deviations were assessed through the drawing of regions of interest on TNC and VNC images reconstructed from corticomedullary and nephrographic phases. A Wilcoxon signed-rank test was performed in order to assess equivalence of data and Spearman’s Rho correlation coefficient to evaluate correlations between each parameter. The diagnostic accuracy of VNC was estimated through the performance of receiver operating characteristic (ROC) curve analysis. Differences between attenuation values were, respectively, 74%, 18%, 5% and 3% (TNC-VNCcort), and 74%, 15%, 9% and 2% (TNC-VNCneph). The Wilcoxon signed-rank test demonstrated the equivalence of attenuation values between the TNC and VNC images. The diagnostic performance of VNC images in the depiction of kidney simple cysts remains high compared to TNC (VNCcort-AUC: 0.896; VNCneph-AUC: 0.901, TNC-AUC: 0.903). In conclusion, quantitative analysis of attenuation values showed a strong agreement between VNC and TNC images in the evaluation of renal masses.

Transcatheter Aortic Valve Implantation (TAVI) Planning with Dual-Layer Spectral CT Using Virtual Monoenergetic Image (VMI) Reconstructions and 20 mL of Contrast Media

“…From a single study, it is possible to decide retrospectively to enhance contrast by employing VMI reconstructions, create a virtual non-contrast image [18] to minimize patient radiation exposure, or investigate tissue composition through the utilization of Z effective images [19,20]. With dual-layer technology, there is no need to schedule a separate examination for a specific clinical question.…”

“…In our study, virtual monoenergetic images were used that resulted from reconstructing data at a hypothetical energy level, such as that achieved with a monoenergetic X-ray beam. In recent times, there has been a growing use of low-energy VMIs, especially in situations with limited contrast, such as in oncology and vascular assessment [18,[21][22][23]. This involves adjusting the energy level close to the iodine absorption K-edge (around 36 keV) to produce low-energy VMIs.…”

Update on Renal Cell Carcinoma Diagnosis with Novel Imaging Approaches

“…In addition, the elimination of true enhanced acquisition would result in an estimated mean radiation dose savings of 24% (range 10-36%) for CT renal mass examinations [25]. A large, recently published retrospective study [26] confirmed that there is a strong agreement between VUE and true unenhanced images in the assessment of renal masses. This is important because unenhanced images provide essential information for the classification of renal cystic lesions and the detection of macroscopic fat, hemorrhage, and calcifications and serve as a baseline for comparison with contrastenhanced images.…”

Virtual Non-Contrast versus True Native in Photon-Counting CT: Stability of Density of Upper Abdominal Organs and Vessels

“…Previous studies using Dual Energy CT (DECT)-derived VNC reconstructions have shown promising results. A high level of consistency between VNC and TNC was shown in many cases, such as, for example, in the imaging of brain structures [ 7 ], abdominal organs [ 8 , 9 , 10 , 11 ] and vessels [ 12 ]. Similarly, studies on DECT-derived data sets have repeatedly described the direct clinical benefits of VNC.…”

“…Overview of the measured structures. Circular regions of interest (ROI) were placed in the portal vein (1), in the descending aorta (2), in the inferior vena cava (3), in the liver parenchyma (4), in the spleen parenchyma(5), in the psoas muscle(6), in the subcutaneous adipose tissue(7), in the surrounding air(8), in the erector spinae muscle(9) and in the first lumbar vertebral body(10).…”