This article describes the technical principles and clinical applications of dual-energy computed tomography (DECT) in the context of cardiothoracic imaging with a focus on current developments and techniques. Since the introduction of DECT, different vendors developed distinct hard and software approaches for generating multi-energy datasets and multiple DECT applications that were developed and clinically investigated for different fields of interest. Benefits for various clinical settings, such as oncology, trauma and emergency radiology, as well as musculoskeletal and cardiovascular imaging, were recently reported in the literature. State-of-the-art applications, such as virtual monoenergetic imaging (VMI), material decomposition, perfused blood volume imaging, virtual non-contrast imaging (VNC), plaque removal, and virtual non-calcium (VNCa) imaging, can significantly improve cardiothoracic CT image workflows and have a high potential for improvement of diagnostic accuracy and patient safety.

Background: Type 2 diabetes mellitus (DM) is the most common metabolic disorder in the world and an important risk factor for peripheral arterial disease (PAD). CT angiography represents the method of choice for the diagnosis, pre-operative planning, and follow-up of vascular disease. Low-energy dual-energy CT (DECT) virtual mono-energetic imaging (VMI) has been shown to improve image contrast, iodine signal, and may also lead to a reduction in contrast medium dose. In recent years, VMI has been improved with the use of a new algorithm called VMI+, able to obtain the best image contrast with the least possible image noise in low-keV reconstructions. Purpose: To evaluate the impact of VMI+ DECT reconstructions on quantitative and qualitative image quality in the evaluation of the lower extremity runoff. Materials and Methods: We evaluated DECT angiography of lower extremities in patients suffering from diabetes who had undergone clinically indicated DECT examinations between January 2018 and January 2023. Images were reconstructed with standard linear blending (F_0.5) and low VMI+ series were generated from 40 to 100 keV, in an interval of 15 keV. Vascular attenuation, image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were calculated for objective analysis. Subjective analysis was performed using five-point scales to evaluate image quality, image noise, and diagnostic assessability of vessel contrast. Results: Our final study cohort consisted of 77 patients (41 males). Attenuation values, CNR, and SNR were higher in 40-keV VMI+ reconstructions compared to the remaining VMI+ and standard F_0.5 series (HU: 1180.41 ± 45.09; SNR: 29.91 ± 0.99; CNR: 28.60 ± 1.03 vs. HU 251.32 ± 7.13; SNR: 13.22 ± 0.44; CNR: 10.57 ± 0.39 in standard F_0.5 series) (p < 0.0001). Subjective image rating was significantly higher in 55-keV VMI+ images compared to the other VMI+ and standard F_0.5 series in terms of image quality (mean score: 4.77), image noise (mean score: 4.39), and assessability of vessel contrast (mean value: 4.57) (p < 0.001). Conclusions: DECT 40-keV and 55-keV VMI+ showed the highest objective and subjective parameters of image quality, respectively. These specific energy levels for VMI+ reconstructions could be recommended in clinical practice, providing high-quality images with greater diagnostic suitability for the evaluation of lower extremity runoff, and potentially needing a lower amount of contrast medium, which is particularly advantageous for diabetic patients.

Objective: The aim of this study was to evaluate the diagnostic accuracy of conventional CT values and the dual-energy computed tomography (DECT)-derived effective atomic number (Zeff), fat fraction (FF) and iodine concentration (IC) for the differentiation of hypodense liver lesions in patients with colorectal cancer (CRC). Methods: One hundred and twenty patients (mean age: 65 ± 12 years) affected by CRC who underwent dual-source DECT as part of tumor staging between December 2015 and June 2023 were retrospectively evaluated. Spectral datasets were reconstructed for each patient and regions of interest were applied at the level of hypodense liver lesions to collect CT, Zeff, FF and IC values. To assess diagnostic accuracy, receiver operating characteristic (ROC) curves were constructed to evaluate the area under the curve (AUC), sensitivity, and specificity using biopsy or MRI (in cases when biopsy was not indicated or feasible) as a reference standard. The Youden index was used to identify optimal cut-off values for potential clinical applications. Results: A total of 223 lesions (147 metastases and 76 cysts) were evaluated. CT, FF and IC values differed significantly between metastases and cysts (p < 0.0001), showing high diagnostic accuracy. FF showed significantly higher diagnostic accuracy compared to all other parameters (all p ≤ 0.0074), with an AUC value of 0.97 (95% CI: 0.94–0.99). For a cut-off > 15.9, the sensitivity reached 91.8% (95% CI: 86.2–95.7) and the specificity reached 98.7% (95% CI: 92.9–100). Zeff numbers did not differ considerably (p = 0.781) between the two entities and demonstrated a lower AUC (0.511; 95% CI: 0.44–0.58). Conclusions: FF measurements proved to have high diagnostic accuracy compared to CT values, IC, and Zeff in the evaluation of hypodense liver lesions in patients suffering from colorectal carcinoma.