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Detection of fat content in thymic lesions is crucial to differentiate thymic hyperplasia from thymic tumors or other anterior mediastinal pathologies.To assess the feasibility of dual-energy CT (DECT) fat content quantification for the differentiation of anterior mediastinal lesions from benign thymic lesions and the normal spectrum of the thymus.Chest DECT images of 465 patients (median 61 years, 63% female) were visually evaluated by two radiologists and semiquantitatively scored based on the degree of fatty degeneration ranging from completely fatty (score 0) to predominantly soft-tissue (score 3), and anterior mediastinal mass (score 4). A subset of scans (n =134 including all cases with scores 2-4 and 20 randomly-selected cases from scores 0 and 1) underwent quantitative DECT analysis (fat fraction, iodine density, and conventional CT value). DECT values were compared across the semiquantitative scores.Results of visual evaluation included 35 with predominantly solid thymus (score 3) and 15 with anterior mediastinal mass (score 4). The most common clinical diagnoses of the 15 masses (including 8 with pathologic confirmation) were metastases (n = 10) and lymphoma (n = 4). CT values in the abnormal thymus were significantly higher than those in score 3 (median: 69.7 HU versus 19.9 HU, P0.001). There was no significant difference in iodine density values (median: 1.7 mg/ml versus 1 mg/ml, P = 0.09). However, the fat fraction value was significantly lower in the abnormal thymus (score 4) than in the predominantly soft-tissue attenuation thymuses (score 3) (median: 12.8% versus 38.7%, P0.001). ROC curve analysis showed that fat fraction had an AUC of 0.96 (P0.001), with a cutoff of39.2% fat fraction yielding 100% sensitivity and 85% specificity.DECT fat fraction measurements of the thymus may provide additional value in distinguishing anterior mediastinal lesions from benign thymus. Use of DECT may reduce the need for subsequent imaging evaluation.

To investigate the prognostic value of dual-energy CT (DECT) based radiomics to predict disease-free survival (DFS) and overall survival (OS) for patients with advanced gastric cancer (AGC) after neoadjuvant chemotherapy (NAC).From January 2014 to December 2018, a total of 156 AGC patients were enrolled and randomly allocated into a training cohort and a testing cohort at a ratio of 2:1. Volume of interest of primary tumor was delineated on eight image series. Four feature sets derived from pre-NAC and delta radiomics were generated for each survival arm. Random survival forest was used for generating the optimal radiomics signature (RS). Statistical metrics for model evaluation included Harrell's concordance index (C-index) and the average cumulative/dynamic AUC throughout follow-up. A clinical model and a combined Rad-clinical model were built for comparison.The pre-IU (derived from iodine uptake images before NAC) RS performed best for DFS and OS in the testing cohort (C-indices, 0.784 and 0.698; the average cumulative/dynamic AUCs, 0.80 and 0.77). When compared with the clinical model, the radiomics model had significantly higher C-index to predict DFS in the testing cohort (0.784 vs. 0.635, p 0.001), but no statistical difference was found for OS (0.698 vs. 0.680, p = 0.473). The combined Rad-clinical models showed improved performance in the testing cohort, with C-indices of 0.810 and 0.710 for DFS and OS, respectively.DECT-derived radiomics serves as a promising non-invasive biomarker to predict survival for AGC patients after NAC, providing an opportunity for transforming proper treatment.

To evaluate the computed tomography (CT) attenuation values, background noise, arterial depiction, and image quality in whole-body dual-energy CT angiography (DECTA) at 40 keV with a reduced iodine dose using deep-learning image reconstruction (DLIR) and compare them with hybrid iterative reconstruction (IR).Whole-body DECTA with a reduced iodine dose (200 mg iodine/kg) was performed in 22 patients, and DECTA data at 1.25-mm section thickness with 50% overlap were reconstructed at 40 keV using 40% adaptive statistical iterative reconstruction with Veo (hybrid-IR group), and DLIR at medium and high levels (DLIR-M and DLIR-H groups). The CT attenuation values of the thoracic and abdominal aortas and iliac artery and background noise were measured. Arterial depiction and image quality on axial, multiplanar reformatted (MPR), and volume-rendered (VR) images were assessed by two readers. Quantitative and qualitative parameters were compared between the hybrid-IR, DLIR-M, and DLIR-H groups.The vascular CT attenuation values were almost comparable between the three groups (p=0.013-0.97), but the background noise was significantly lower in the DLIR-H group than in the hybrid-IR and DLIR-M groups (p0.001). The arterial depictions on axial and MPR images and in almost all arteries on VR images were comparable (p=0.14-1). The image quality of axial, MPR, and VR images was significantly better in the DLIR-H group (p0.001-0.015).DLIR significantly reduced background noise and improved image quality in DECTA at 40 keV compared with hybrid-IR, while maintaining the arterial depiction in almost all arteries.

We present the case of a 24-year-old woman who presented to the emergency department with mid-epigastric pain and nausea. Contrast enhanced dual-energy CT showed high iodine signal in the small bowel lumen concerning for gastrointestinal bleeding since oral contrast was not given. However, overt bleeding symptoms were absent. Further in-house analysis of the dual-energy CT data revealed the hyperattenuating intraluminal material to be oral indigestion medicine containing magnesium, aluminum, or bismuth, and not extravasated iodine.

OBJECTIVES To assess the potential role of low monoenergetic images in the evaluation of acute appendicitis. METHODS A retrospective study of 42 patients with pathology proven acute appendicitis underwent contrast-enhanced-CT conducted on a single-source-DECT before surgery. Attenuation, SNR, and CNR were calculated on both monoenergetic and conventional images and compared to 24 abdominal CT-scans with normal appendix. Representative conventional and monoenergetic images were randomized and presented side-by-side to three abdominal radiologists to determine preferred images for detecting inflammation. Additionally, six individual acute inflammatory characteristics were graded on a 1-5 scale to determine factors contributing to differences between conventional and monoenergetic images by 2 abdominal radiologists. Paired t-tests, Wilcoxon and McNemar tests, and intra-observer error statistics were performed. RESULTS For the inflamed appendixes monoenergetic images had overall increased attenuation (average ratio 1.7; P

Background and purpose Dual energy CT is increasingly available and used in the standard diagnostic setting of ischemic stroke patients. We aimed to evaluate how different dual energy CT virtual monoenergetic energy levels impact identification of early ischemic changes, compared to conventional polyenergetic CT images. Materials and methods This retrospective single-center study included patients presenting with acute ischemic stroke caused by an occlusion of the intracranial internal carotid artery or proximal middle cerebral artery. Data was gathered on consecutive patients admitted to our institution who underwent initial diagnostic stroke imaging with dual layer dual energy CT and a subsequent follow-up CT one to three days after admission. Automated ASPECTS results from conventional polyenergetic and different virtual monoenergetic energy level reconstructions at admission were generated and compared to reference standard ASPECTS. Confidence intervals (CI) for sensitivity, specificity, negative and positive predictive value were calculated. Results A total of 24 patients were included. Virtual monoenergetic reconstructions of 70 keV had the highest region-based ASPECTS accuracy, 0.90 (sensitivity 0.82 (95% CI 0.72–0.93), specificity 0.92 (0.88–0.97), negative predictive value 0.94 (0.90–0.96)), whereas virtual monoenergetic reconstructions of 40 keV had the lowest, 0.77 (sensitivity 0.34 (0.26–0.42), specificity 0.90 (0.89–0.96), negative predictive value 0.80 (0.77–0.83)). Conclusions Automated 70 keV ASPECTS had the highest diagnostic accuracy, sensitivity and negative predictive value overall. Our results indicate that virtual monoenergetic energy levels impact the identification of early ischemic changes on CT.

Dual-energy computed tomography (DECT) combines the advantages of conventional CT with the ability to detect bone marrow oedema (BMO), which was previously limited to magnetic resonance imaging (MRI). By analysing DECT virtual non-calcium (VNCa) maps, radiologists can improve the detection of subtle and occult fractures and approximate the acuity/healing of fractures of indeterminate age. This review highlights the role of DECT in the assessment of musculoskeletal trauma, particularly among elderly, post-menopausal women and those at risk for osteoporosis. DECT is especially useful in investigating trabecular bone predominant regions (e.g., vertebral bodies, pelvis, hip, and long bone metaphyses) for stress (i.e., fatigue or insufficiency) and fragility fractures. CT is often performed first due to its increased availability, especially in the emergency setting, shorter imaging duration, and possible patient contraindications to magnetic resonance imaging (MRI). By enabling BMO detection, DECT may have a role in triaging patients for definitive MRI assessment. Understanding the role of anatomical, pathological, and patient factors in image interpretation can improve radiologist adoption of DECT, increase diagnostic confidence, and improve patient management.

A novel fast kilovoltage switching dual-energy CT with deep learning [Deep learning based-spectral CT (DL-Spectral CT)], which generates a complete sinogram for each kilovolt using deep learning views that complement the measured views at each energy, was commercialized in 2020. The purpose of this study was to evaluate the accuracy of CT numbers in virtual monochromatic images (VMIs) and iodine quantifications at various radiation doses using DL-Spectral CT.Two multi-energy phantoms (large and small) using several rods representing different materials (iodine, calcium, blood, and adipose) were scanned by DL-Spectral CT at varying radiation doses. Images were reconstructed using three reconstruction parameters (body, lung, bone). The absolute percentage errors (APEs) for CT numbers on VMIs at 50, 70, and 100 keV and iodine quantification were compared among different radiation dose protocols.The APEs of the CT numbers on VMIs were15% in both the large and small phantoms, except at the minimum dose in the large phantom. There were no significant differences among radiation dose protocols in computed tomography dose index volumes of 12.3 mGy or larger. The accuracy of iodine quantification provided by the body parameter was significantly better than those obtained with the lung and bone parameters. Increasing the radiation dose did not always improve the accuracy of iodine quantification, regardless of the reconstruction parameter and phantom size.The accuracy of iodine quantification and CT numbers on VMIs in DL-Spectral CT was not affected by the radiation dose, except for an extremely low radiation dose for body size.

Recognizing the bone edema associated with acute traumatic injury of the musculoskeletal system can guide the identification of subtle nondisplaced and minimally displaced fractures. On conventional single energy CT, this bone edema is obscured by cancellous bone. Dual-energy CT (DECT) techniques allow for material decomposition and, hence, ‘calcium subtracted’ virtual noncalcium (VNCa) images, which clearly depict intramedullary bone edema. This article discusses DECT in the context of musculoskeletal trauma, highlighting aspects of image acquisition technique and other technical considerations. The evidence supporting DECT with VNCa to diagnose acute fractures in the musculoskeletal system including the spine and extremities is discussed.

The combination of different bioimaging techniques, mainly in the field of oncology, allows circumventing the defects associated with the individual imaging modalities, thus providing a more reliable diagnosis. The development of multimodal endogenous probes that are simultaneously suitable for various imaging modalities, such as magnetic resonance imaging (MRI), X-ray computed tomography (CT) and luminescent imaging (LI) is, therefore, highly recommended. Such probes should operate in the conditions imposed by the newest imaging equipment, such as MRI operating at high magnetic fields and dual-energy CT. They should show, as well, high photoluminescence emission intensity for their use in optical imaging and present good biocompatibility. In this context, we have designed a single nanoprobe, based on a core-shell architecture, composed of a luminescent Eu:BaLuF core surrounded by an external HoF shell that confers the probe with very high magnetic transverse relaxivity at high field. An intermediate, optically inert BaLuF layer was interposed between the core and the shell to hinder Eu–Ho cross-relaxation and avoid luminescence quenching. The presence of Ba and Lu, with different K-edges, allows for good X-ray attenuation at high and low voltages. The core-shell nanoparticles synthesized are good potential candidates as trimodal bioprobes for MRI at high field, dual-energy CT and luminescent imaging., This research was funded by the Spanish Ministry of Science, Innovation, and Universities (RTI2018-094426-B-I00). Siemens Healthcare S.L.U. also supported part of the research. We also acknowledge the use of the CNA’s ICTS NanoCT facilities and support from DGA and Fondos Feder for funding Bionanosurf (E15_17R) research group. S. Garcia-Embid acknowledges the Ministerio de Educación, Cultura y Deportes of Spanish Government for a FPU grant (FPU15/04482).

Objective To determine the clinical value of 18F-FDG-PET/CT and dual-energy virtual noncalcium CT to detect and identify single osteolytic metastases (SOM) in participants with non-small cell lung cancer (NSCLC). Materials and Methods Forty-two participants (mean age, 63.5 years ± 10.1; range, 41–81 years) with suspected SOM diagnosed by whole-body 18F-FDG-PET/CT underwent non-enhanced dual-energy CT. All images were visually and quantitatively evaluated by two nuclear medicine physicians (R1 and R2) and two radiologists (R3 and R4) independently. The results of visual and quantitative analysis of 18F-FDG-PET/CT and dual-energy CT were compared with pathological results. Results In the visual analysis, the specificity and positive predictive value of dual-energy CT for reader 1 and reader 2 is larger than the corresponding figures of18F-FDG-PET/CT for reader 3 and reader 4 (94.1% each vs 82.4%/76.5%; 95.2%/95.0% vs 88.9%/86.2%). The sensitivity and negative predictive value of dual-energy CT is relatively lower than the number of 18F-FDG-PET/CT for readers (80.0%/76.0% vs 96.0%/100.0%; 76.2%/72.7% vs 93.3%/100.0%, respectively). ROI-based analysis of SUVmax on PET/CT images and CT numbers on VNCa images showed a significant difference between metastases and non-metastases (P Conclusions Pre-surgical evaluation by combination of whole-body 18F-FDG-PET/CT and dual-energy CT could improve the classification of SOM and may further guide the surgical decision-making in participants with NSCLC.

This article explores the technical background of dual-energy CT (DECT) imaging along with its basic principles, before turning to a review of the various DECT applications specific to pancreatic imaging. In light of the most recent literature, we will review the constellation of DECT applications available for pancreatic imaging in both oncologic and non-oncologic applications. We emphasize the increased lesion conspicuity and the improved tissue characterization available with DECT post-processing tools. Finally, future clinical applications and opportunities for research will be overviewed.

Purpose To evaluate the effect of advanced monoenergetic imaging (MEI+) postprocessing algorithm on the visualization of various intramuscular lesions on portal-venous-phase contrast-enhanced dual-energy computed tomography (DECT). Material and Methods Thirty-nine patients (64.3 ± 11.1 years; 26 males) with various intramuscular lesions ranging from malignancy, bleeding, inflammation, edematous changes, and benign neoplasms were included and underwent DECT (100/Sn150kV). Postprocessing with MEI+ technique was used to reconstruct images at four different keV levels (40, 60, 80, 100) and compared to the standard portal-venous-phase CT (CTpv) images. Image quality was assessed qualitatively (conspicuity, delineation, sharpness, noise, and confidence) by two independent readers using 5-point Likert scales, 5 = excellent; as well as quantitatively by calculating signal-to-noise ratios (SNR), contrast-to-noise ratios (CNR), and area under the receiver operating characteristic (ROC) curve (AUC) for lesion characterization. Results Highest lesion enhancement and diagnostic confidence were observed in MEI+ 40 keV, with significant differences to CTpv (p Conclusion MEI+ at low keV levels can significantly improve lesion detection of benign versus malignant intramuscular entities in patients undergoing portal-venous-phase DECT scans due to increased CNR.

Background The current clinical standard for in vivo imaging of myocardial fibrosis is contrast-enhanced cardiac magnetic resonance (CMR). We sought to validate a novel non-contrast dual energy computed tomography (DECT) method to estimate myocardial fibrosis in patients undergoing CMR with contrast. Methods All subjects underwent non-contrast, prospectively-triggered cardiac DECT on a single source scanner with interleaved acquisition between tube voltages of 80 and 140 kVp. Monochromatic images were reconstructed at 11 energies spanning 40–140 keV; a region of interest (ROI) was drawn in the mid-inferoseptal segment, recording mean attenuation value in the ROI, at each energy level. Comparison was made to data from single energy (70 keV) image data. Linear discriminant analysis (LDA) was performed to compare the predictive capability of single vs. multi-energy inferoseptal segment CT attenuation on myocardial fibrosis by both visually assessed LGE (absent/present fibrosis) and CMR T1 mapping-derived myocardial extracellular volume fraction (ECV). Results The multi-energy CT/LDA approach performed better than a single energy approach to discriminate among LGE-CMR classes of present/absence myocardial fibrosis severity, demonstrating correct classification rates of 89% and 71%, respectively. The multi-energy CT/LDA approach also performed better in correctly discriminating normal from elevated ECV, doing so in 89% of patients vs. correct distinction of normal/elevated ECV in only 70% using the single energy approach. Conclusions Non-contrast cardiac DECT with multi-energy analysis better classifies myocardial fibrosis and extracellular volume compared to what is feasible with non-contrast single energy cardiac CT. These data support further evaluation of this approach to noninvasively assess myocardial fibrosis.

Purpose To evaluate the use of dual-energy computed tomography (CT) virtual noncalcium imaging (VNCa) to visualize ice ball growth during skeletal cryoablation procedures in the spine and bony pelvis. Materials and Methods Cryoablation was performed in the spine and bony pelvis of swine and human cadavers at 5 and 6 locations, respectively. CT scans were acquired every 2 minutes using a dual-source dual-energy scanner. Artifacts were suppressed using iterative metal artifact reduction, and ablation zones in the bones and surrounding tissue were visualized using multiplanar VNCa and mixed kV imaging. For each probe location and time point, ice detectability was determined and the volume of the ice was measured. Results At each location, ice was visualized within the bone before reaching critical neural and intraabdominal structures. Within bone, the ice ball could not be visualized on mixed kV images, but was seen using VNCa images before reaching the adjacent soft tissue in 7/11 (64%) scenarios. Volume of the smallest ice ball seen in VNCa images was 18% of the final volume after cryoablation compared with 42% for mixed kV (P = .014). Conclusions This application of dual-energy CT and VNCa imaging to cryoablation monitoring permits earlier ice visualization within the vertebral column and pelvic bones in near real time. Because these scanners and imaging techniques increase in availability in interventional suites, cryoablation of tumors along the spine and pelvic bone potentially could be performed with greater confidence.

Purpose To compare attenuation measurements and image quality of virtual unenhanced phase (VUP) images with those of conventional true unenhanced phase (TUP) images on spectral dual energy computed tomography (DECT) with dual layer detector on abdominal tissues and to assess potential reduction in radiation dose. Material and method A total of 295 patients (185 men, 110 women; mean age 61 ± 17.6 [SD] years [range: 17–95 years]) who had undergone abdominal or thoraco-abdominal CT with pre- and post-contrast imaging (portal phase) with spectral DECT with dual layer detector were retrospectively analyzed. VUP images based on portal-venous phase DECT acquisition were generated. Regions of interest were defined in abdominal tissues (liver, spleen, kidney, muscle and fat) by two independent readers. Inter-technique agreement (VUP images vs. TUP images) on attenuation measurements was assessed. Signal-to noise ratio (SNR) and image quality of TUP and VUP images were compared. The radiation dose delivered to patients was compared with the radiation dose of protocols without TUP images. Results A total of 9880 ROIs were drawn in the abdominal tissues. The difference in mean attenuation values between TUP and VUP images was less than 15 HU in 98.3% and less than 10 HU in 92.3% of all measurements. VUP images overestimated attenuation in fat comparatively to TUP images. Image quality was evaluated as good or excellent in 77% (37/48) of TUP images and 54% (26/48) of VUP images. Using VUP images instead of TUP images could decrease the radiation dose by 32%. Conclusion VUP images demonstrate good agreement with TUP images in different abdominals tissues and can be obtained with similar image quality as TUP. VUP images appear as an alternative to TUP images, resulting in reduction of radiation dose delivered to the patient.

Objectives To compare the virtual non-contrast (VNC) images acquired through dual-energy computed tomography (DECT) with the true non-contrast (TNC) images in the detection of biliary stones and to calculate dose reduction by replacing TNC images with VNC images. Methods Between March 2017 and April 2018, we retrospectively enrolled 75 patients with suspicious biliary disease who underwent dual-source DECT and surgery and/or endoscopic intervention within 2 months from the CT. Biliary stones were present in 45 patients. The sensitivity and specificity for detecting gallstone and common bile duct (CBD) stone were compared between the VNC and TNC using McNemar test. In addition, the possible reduction in radiation dose was calculated. Results In our study, 37 patients had gallstones, 2 had CBD stones, and 6 had both gallstone and CBD stones. For detection of gallstones, the sensitivity and specificity were 90.7% (39/43) and 87.5% (28/32), respectively, for the TNC images, and 88.4% (38/43) and 90.6% (29/32), respectively, for the VNC images. With respect to CBD stones, the sensitivity and specificity were 87.5% (7/8) and 98.5% (66/67), respectively, for the TNC images, and 75.0% (6/8) and 100% (67/67), respectively, for the VNC images. There was no significant difference in the sensitivity and specificity between each image set (P > 0.05). The radiation dose reduction of 22.4 ± 1.3% is expected by omitting TNC images. Conclusions The VNC images derived from DECT were comparable to the TNC images for the detection of biliary stones and may replace the TNC images to reduce radiation dose.

Purpose To investigate the hemodynamic changes in liver cirrhosis by comparing iodine density in hepatic and splenic parenchyma with 8 cm detector dual energy CT (DECT). Materials and Methods Forty-six consecutive patients with liver cirrhosis and 22 healthy volunteers were recruited in this study, and they were all performed contrast enhanced examination with 8 cm detector DECT. All raw data were reconstructed with 1.25 mm slice thickness, Iodine density (in milligrams per milliliter) were measured on iodine-based material decomposition images. Quantitative indices of iodine density (ID), including normalized ID of liver parenchyma for arterial phase (NIDLAP), ID of liver parenchyma for venous phase (IDLVP), ID of splenic parenchyma for arterial phase (IDSAP), ID of splenic parenchyma for venous phase (IDSVP), ID of portal vein in venous phase (IDPVP) and Liver arterial iodine density fraction (AIF) were measured and compared between two groups. The correlation between Child-Pugh grade and other quantitative indices were calculated, with statistical significance as P Results For all 46 liver cirrhosis patients, 10 were classified in grade A, 24 in Grade B and 12 in Grade C. Compared with control group, patients with liver cirrhosis showed (1) no statistical difference in general data (age, gender, height and weight) (all P>0.05), (2) higher iodine density of NIDLAP, IDSVP, IDPVP and AIF, and lower NIDSAP (all P Conclusion Based on iodine density measurement in DECT, it is possible to evaluate the hemodynamic changes in liver and spleen parenchyma in liver cirrhosis. Quantitative indices of AIF and NIDLAP demonstrate positive correlation with Child-Pugh grade, which accommodates potential possibility for DECT as a noninvasive tool in assessing the severity of liver cirrhosis.

The aim of this study was to use dual energy CT technology to maintain or improve image quality in pediatric head CT while simultaneously reducing radiation dose.In this retrospective study, helical head CTs performed using a standard head CT protocol were compared to studies performed with a dual energy (DE) protocol. Objective comparison was performed by measuring regions of interest in 11 areas of the brain. Subjective rating for image quality using a Likert scale, was performed by three radiologists. Radiation doses were evaluated using CT dose index and dose length product.Signal-to-noise ratio was, for the most part, not significantly different between the DE and conventional scans. Contrast-to-noise ratio was slightly lower for children over 6 year of age utilizing the dual energy protocol versus the standard protocol. Qualitatively, there was little difference in image quality in patients6 years old, with the only significant difference in infratentorial noise. However, in patients6 years of age, infratentorial noise, sharpness and diagnostic acceptability, as well as supratentorial sharpness were all significantly improved by DE CT technique. Radiation exposure as measured by CTDI and DLP was modestly lower with the dual energy protocol in all study populations.Dual energy CT can be used clinically in pediatric patients to maintain or improve image quality while reducing radiation dose.

This article reviews the imaging manifestations of chronic myocardial infarction (MI) on computed tomography (CT) and the common mimickers of MI, clinically and on imaging. Several examples of the appearance of chronic MI, its complications, and mimickers of MI are shown on both routine and cardiac CT.

We aimed to review the latest cutting-edge trends in emerging techniques of musculoskeletal imaging. This study reviews the current status and the preliminary studies of Magnetic Resonance Fingerprinting (MRF), Ultrashort Echo Time (UTE) sequence, Positron Emission Tomography (PET)/MR and Dual-Energy CT scan (DECT) in various oncologic and non-oncologic conditions of the musculoskeletal system. The current application, current and future research trends and limitations of each imaging technique were discussed. There are substantial potentials in MRF, UTE, PET/MR and DECT for characterization of various musculoskeletal disorders. Further dedicated studies in various fields are necessary.

To evaluate the impact of noise-optimized virtual monoenergetic imaging (VMI) on lesion demarcation and measuring accuracy of hypoattenuating liver metastases in patients with fatty liver disease compared to standard reconstructions.Twenty-eight patients (mean age 62.2 ± 7.7 years) with fatty liver disease and hypoattenuating liver metastases who underwent unenhanced and contrast-enhanced portal-venous dual-energy CT (DECT) were enrolled. Standard linearly blended and VMI series were reconstructed in 10-keV intervals. Lesion-to-parenchyma contrast-to-noise ratio (CNR) was calculated and the best VMI series was further investigated in a subjective evaluation of overall image quality and lesion demarcation. Size measurements were performed independently by measuring all hypodense lesions (n = 58) twice in a predefined sequence. Inter- and intra-rater agreement was assessed using intra-class correlation coefficient (ICC) statistics.The calculated CNR was greatest at 40-keV VMI (4.3 ± 2.6), significantly higher compared to standard reconstructions (2.9 ± 1.9; p0.001). Subjective ratings for overall image quality showed no significant difference between the 2 reconstruction techniques (both medians 4; p = 0.147), while lesion margin demarcation was found to be superior for 40-keV VMI (median 5; p ≤ 0.001). Inter- (ICC, 0.98 for 40-keV VMI; ICC, 0.93 for standard reconstruction) and intra-rater (ICC, 0.99 for 40-keV VMI; ICC, 0.94 for standard image series) analysis showed an excellent agreement for lesion measurements in both reconstruction techniques.Noise-optimized VMI reconstructions significantly improve contrast and lesion demarcation of hypoattenuating liver metastases in patients with the fatty liver disease compared to standard reconstruction.

Current computed tomography bowel imaging is challenging given the variable distension, content, and location of the bowel, the different appearance of tumors within and adjacent to bowel, and peristaltic artifacts. Published data remain sparse. Derangements in enhancement may be highlighted, image artifacts reduced, and radiation dose from multiphase scans minimized. This modality is suited for imaging bowel tumor detection and characterization, gastrointestinal bleeding, and bowel inflammation, and ischemia. Experimental results on computed tomography colonography and novel bowel contrast material offer hope for major improvements in bowel interrogation. It is likely to become increasingly valuable for bowel-related disease diagnosis and monitoring.

Since its clinical inception a decade ago, dual-energy computed tomography has expanded the array of computed tomography imaging tools available to the practicing abdominal radiologist. Of note, diagnostic solutions for imaging-based evaluation of genitourinary diseases, foremost kidney calculi and renal tumors characterization, represent the apogee applications of dual-energy computed tomography in abdominal imaging. This article reviews clinical applications of dual-energy computed tomography for the assessment of genitourinary diseases.

Objective To analyze whether there are significant differences in the objective quantitative parameters obtained in the postprocessing of dual-energy CT enterography studies between bowel segments with radiologic signs of Crohn's disease and radiologically normal segments. Material and methods This retrospective study analyzed 33 patients (16 men and 17 women; mean age 54 years) with known Crohn's disease who underwent CT enterography on a dual-energy scanner with oral sorbitol and intravenous contrast material in the portal phase. Images obtained with dual energy were postprocessed to obtain color maps (iodine maps). For each patient, regions of interest were traced on these color maps and the density of iodine (mg/ml) and the fat fraction (%) were calculated for the wall of a pathologic bowel segment with radiologic signs of Crohn's disease and for the wall of a healthy bowel segment; the differences in these parameters between the two segments were analyzed. Results The density of iodine was lower in the radiologically normal segments than in the pathologic segments [1.8 ± 0.4 mg/ml vs. 3.7 ± 0.9 mg/ml; p The fat fraction was higher in the radiologically normal segments than in the pathologic segments [32.42% ± 6.5 vs. 22.23% ± 9.4; p Conclusion There are significant differences in the iodine density and fat fraction between bowel segments with radiologic signs of Crohn's disease and radiologically normal segments.

To compare the renal parenchyma attenuation of virtual noncontrast (VNC) images derived from multiphase renal dual-energy computed tomography (DECT) with standard noncontrast (SNC) images, and to determine the optimum phase for VNC images.Twenty-nine men and 16 women (mean age, 61 ± 13 years; range, 37-89 years) underwent dynamic renal DECT (100/Sn140 kVp) were included in this institutional review board-approved retrospective study. There were four phases of the scan, which included noncontrast, corticomedullary (CMP), nephrographic (NP), and excretory phases (EP). The VNC images was generated from CMP, NP and EP. CT numbers of SNC images and VNC images of each phases were measured in the renal cortex and medulla. Mean standard deviation of subcutaneous fat was measured as image noise on SNC and VNC images. Radiation dose was recorded and potential radiation dose reduction was estimated. Results were tested for statistical significance using the unpaired t-test and agreement using Bland-Altman plot analysis.The difference in mean attenuation between SNC and each phase of VNC images were ≤4 HU. The mean attenuation of renal cortex and medulla was 33.2 ± 4.4 HU, and 34.2 ± 4.8 HU in SNC, 33.6 ± 7.6 HU and 31.1 ± 8.3 HU in VNC of CMP, 34.8 ± 8.6 HU and 35.6 ± 8.5 HU in VNC of NP, 31.5 ± 7.6 HU and 32.4 ± 7.5 HU in VNC of EP. In VNC of CMP, the attenuation of the cortex was higher than the medulla (p 0.05), and the attenuation of medulla was significant lower than that of SNC (p 0.01). In VNC of NP, the attenuation of renal cortex was higher than SNC (p 0.05). In VNC of EP, the attenuation of cortex and medulla were lower than SNC (p 0.05), and inadequate iodine subtraction in collecting system was noted. Image noise was significantly greater in SNC (p 0.001). Mean radiation dose reduction achievable by removing the SNC was 12.3% ± 0.9%.VNC images from multiphase renal DECT were similar to SNC images. Using the nephrographic phase can gives more comparable VNC images to SNC images in renal parenchyma than other phases.

Spectral computed tomography (CT) or dual-energy CT (DECT) is an advanced form of CT with increasing applications in head and neck radiology. This article provides an overview of the DECT technique and reviews current applications for the evaluation of neck pathology, focusing on oncologic applications. Included are an overview of the basic underlying principles and approaches for DECT scan acquisition and material characterization; a discussion of various DECT reconstructions and a brief overview of practical issues pertaining to DECT implementation, including those related to workflow impact of DECT; and a discussion of various applications of DECT for the evaluation of the neck, especially in oncology.

Cerebrospinal fluid leaks pose a serious threat to patients as they represent an unchecked communication between the subarachnoid space and the extracranial environment. Accurate localization of the leakage site is essential for treatment planning. We describe the novel utilization of dual-energy computed tomography technology in cisternography in the evaluation of a patient with a cerebrospinal fluid leak.

Highlights • Macrophage imaging with Ultrasmall Superparamagnetic Iron Oxide could be achieved using Dual Energy CT. • Quantitative iron congaing could be evaluated using Dual Energy CT. • Our research showed could be visualized by overlaying the iron density image on the 70-keV image., Purpose While ultrasmall superparamagnetic iron oxide (USPIO) is useful for identifying atherosclerotic lesions as an MRI contrast medium, there are limitations in its power to quantitatively evaluate and resolve USPIO in atherosclerotic lesions of the heart. Computed tomography (CT) has a higher resolution than MRI, and Dual Energy CT is capable of visualizing iron atoms, the main component of USPIO. More recently, a new USPIO capable of achieving longer retention times in blood circulation compared to the previous USPIO has been developed. The objective of this study was to investigate the feasibility of visualizing and quantifying the new USPIO by dual energy CT. Materials and Methods USPIO with iron concentrations adjusted in 5 steps from 2.5 to 50 mg/mL was visualized by dual energy CT to measure the contrast on virtual monochromatic imaging (40 and 70 keV). In parallel experiments, iodine contrast medium was diluted to the same concentrations and visualized by dual energy CT to measure the contrast at 70 keV. The linearity of the contrast against the iron and iodine concentrations was measured for the quantitative evaluation. Further, a vascular phantom simulating clinical cases (divided into 4 layers: meat alone, meat + USPIO, vascular lumen, and with or without calcification) was prepared. The iron density image was overlaid on the image at 70 keV to evaluate the visualization of the USPIO medium. Results In the imaging of the medium with an iron concentration of 25 mg/mL, the CT numberat 70 keV was 117.0 HU, or about 17% of that of iodine (664.4 HU). The CT number rose to 319.9 HU at 40 keV, or to about 48% of that of iodine. The linearity of the contrast against the iron concentration in USPIO was R2 = 0.9996, indicating a strong correlation. In the simulated vascular phantom, the iron concentration significantly increased in the region containing USPIO, and the quantity could be visualized by overlaying the iron density image displayed with a color scale on the 70-keV image. Conclusion Our results suggested that macrophages could be both quantified and visualized by USPIO on dual energy CT.

There are multiple emerging advanced computed tomography (CT) applications for the evaluation of the neck, many based on dual-energy CT (DECT). DECT is an advanced form of CT in which scan acquisition is performed at two different energies, enabling spectral tissue characterisation beyond what is possible with conventional single-energy CT and potentially providing a new horizon for quantitative analysis and tissue characterisation, particularly in oncological imaging. The purpose of this review is to familiarise the reader with DECT principles and review different clinical applications for the evaluation of the soft tissues of the neck. The article will begin with an overview of DECT scan acquisition, material characterisation, reconstructions, and basic considerations for implementation in the clinical setting. This will then be followed by a review of different clinical applications. The focus will be on oncological imaging, but artefact reduction and other miscellaneous applications will also be discussed.

To determine whether contrast enhanced DECT low monoenergetic can improve diagnostic conspicuity of inflamed kidney foci in acute pyelonephritis compared to conventional images.A retrospective study of 45 patients with clinical signs of acute pyelonephritis undergoing contrast-enhanced exams on a single source-DECT was conducted. Representative conventional and monoenergetic images were randomized and presented to four abdominal radiologists to determine their preference for inflamed kidney foci detection, and to determine the number of foci identified. Clinical impact of monoenergetic images was assessed using multivariant analysis. Contrast and signal to noise ratios were compared between the images using paired t-tests.A greater number of foci were detected on the low energetic images for each patient (6.4 ± 5.3 vs. 4.2 ± 3.8, p 0.02). Additionally, a consistent linear increase in the number of detected foci on the monoenergetic compared to the conventional images was seen (y = 0.10X + 0.36 RLow monoenergetic images enable increased detection of inflamed kidney parenchyma, and permit identification of pathologic foci some of which were not seen on the conventional images. Along with the strong preference of radiologists, these images should be considered beneficial for evaluating acute pyelonephritis.

To assesses whether utilising bone marrow oedema (BMO) maps improved fracture read times and reader confidence in a large series of acute lower extremity trauma dual-energy computed tomography (DECT) studies.One hundred and six DECT studies, including 60 fracture cases and 46 non-fracture cases, were evaluated retrospectively in this cross-sectional study. Three-dimensional (3D) BMO maps were generated for each study and coded to display skeletal anatomy in blue and marrow oedema in green. Studies were interpreted by two readers in two timed stages (without and with BMO maps). Readers identified the number, anatomical location, and comminution of fractures. Reader confidence (five-point Likert scale) for fracture identification and anatomical regions where oedema was present was also recorded.Decreased read times (p0.01) were observed when readers utilised BMO maps for their fracture search. The presence of oedema on BMO maps corresponded with associated fracture in 75.7% reads. No differences in reader confidence were observed as a result of using this BMO-guided technique (95%, 5/5 for both readers with and without the aid of BMO maps).DECT BMO maps improve the speed of radiological identification of suspected acute lower extremity fractures with preserved reader confidence. It may help emergent detection of fractures, important for patient management and outcomes.

Purpose To evaluate the difference in liver density and to compare the performance to diagnose fatty liver between true noncontrast (TNC) images and virtual noncontrast (VNC) images generated from dual-energy CT (DECT). Materials and methods Patients who underwent liver dynamic DECT and MRI were included (n = 49). Two observers measured the liver and spleen densities on TNC images and three VNC images from the arterial, portal and delayed phases of DECT (VNCa, VNCp and VNCd, respectively). The liver-minus-spleen density (density L–S) and liver-to-spleen ratio (density L/S) were calculated. The CT parameters were compared between normal liver patients and fatty liver patients by using the independent t-test. Differences and agreements between measurements on TNC images and VNC images were evaluated by using the paired t-test and Bland-Altman analysis. Receiver operating characteristic (ROC) curve analysis was used to evaluate the diagnostic performance of CT parameters for diagnosing fatty liver. Results All CT parameters measured on TNC and VNC images were significantly higher in normal liver patients than in fatty liver patients. Although the mean liver densities on VNC images were significantly lower than those on TNC images, all CT parameters showed good agreement between TNC images and VNC images. The diagnostic performances of CT parameters on VNC images were not significantly different from those on TNC images. Conclusion Although the liver and spleen density on VNC images was significantly lower than that on TNC images, the diagnostic performances of CT parameters on three VNC images from multiple phases were similar to those on TNC images for diagnosing fatty liver.

Lymph node metastasis (LNM) identification is the most clinically important tasks related to survival and recurrence from lung cancer. However, the preoperative prediction of nodal metastasis remains a challenge to determine surgical plans and pretreatment decisions in patients with cancers. We proposed a novel deep prediction method with a size-related damper block for nodal metastasis (Nmet) identification from the primary tumor in lung cancer generated by gemstone spectral imaging (GSI) dual-energy computer tomography (CT). The best model is the proposed method trained by the 40 keV dataset achieves an accuracy of 86 % and a Kappa value of 72 % for Nmet prediction. In the experiment, we have 11 different monochromatic images from 40∼140 keV (the interval is 10 keV) for each patient. When we used the model of 40 keV dataset, there has significant difference in other energy levels (unit of keV). Therefore, we apply in 5-fold cross-validation to explain the lower keV is more efficient to predict Nmet of the primary tumor. The result shows that tumor heterogeneity and size contributed to the proposed model to estimate whether absence or presence of nodal metastasis from the primary tumor.

Background and purpose To reduce range uncertainty in particle therapy, an accurate computation of stopping-power ratios (SPRs) based on computed tomography (CT) is crucial. Here, we assess range differences between the state-of-the-art CT-number-to-SPR conversion using a generic Hounsfield look-up table (HLUT) and a direct patient-specific SPR prediction (RhoSigma) based on dual-energy CT (DECT) in 100 proton treatment fields. Material and methods For 25 head-tumor and 25 prostate-cancer patients, the clinically applied treatment plan, optimized using a HLUT, was recalculated with RhoSigma as CT-number-to-SPR conversion. Depth–dose curves in beam direction were extracted for both dose distributions in a regular grid and range deviations were determined and correlated to SPR differences within the irradiated volume. Results Absolute (relative) mean water-equivalent range shifts of 1.1 mm (1.2%) and 4.1 mm (1.7%) were observed in the head-tumor and prostate-cancer cohort, respectively. Due to the case dependency of a generic HLUT, range deviations within treatment fields strongly depend on the tissues traversed leading to a larger variation within one patient than between patients. Conclusions The magnitude of patient-specific range deviations between HLUT and the more accurate DECT-based SPR prediction is clinically relevant. A clinical application of the latter seems feasible as demonstrated in this study using medically approved systems from CT acquisition to treatment planning.

Purpose To assess image quality and diagnostic performance of a noise-optimized algorithm to reconstruct virtual monoenergetic images (VMI+) for the detection of endoleaks after endovascular abdominal aortic aneurysm repair (EVAR) using dual-energy CT angiography (DE-CTA). Materials and methods Seventy-five patients (42 men; 66.2 ± 11.7 years) underwent DE-CTA following EVAR. Arterial phase images were acquired in dual-energy mode for the reconstruction of standard linearly-blended M_0.5, VMI+ and traditional monoenergetic images (VMI) at 40–100 keV in 10-keV intervals. Contrast-to-noise ratios (CNR) were calculated for the area of leakage in patients with endoleaks. Diagnostic accuracy for endoleak detection was evaluated by three blinded radiologists using the objectively best series for each reconstruction technique. Results Thirty-four out of 75 patients showed endoleaks. Quantitative image parameters were highest at 40-keV VMI+ (CNR, 21.3 ± 11.1), compared to M_0.5 (CNR, 10.9 ± 5.5) and all VMI series that showed highest values at 70 keV (CNR, 13.5 ± 6.6; all P 0.001). ROC analysis for endoleak detection revealed an area under the curve (AUC) of 0.992 for 40-keV VMI+ series, which was significantly higher ( P ≤ 0.039) compared to 70-keV VMI (0.914) and M_0.5 series (0.916). Conclusions Noise-optimized VMI+ series at 40 keV improve diagnostic accuracy for the detection and rule-out of endoleaks after EVAR.

Dual energy CT (DECT) is an emerging imaging modality that combines data collected with different x-ray energy spectra. The resulting volumetric reconstructions can be utilised for material differentiation and metal artefact reduction in radiological assessments. The literature was reviewed to identify articles discussing the use of post mortem CT (PMCT) in odontology, DECT for metal artefact reduction in dental imaging, and current uses of DECT in forensic imaging. Articles written in English and published between 2004 and 2016 were selected for thematic analysis. A total of 54 articles were analysed. PMCT has been used routinely and validated for identification and age estimation due to its numerous reformatting capabilities and registration techniques. DECT-specific techniques including mono-energetic reconstructions, coupled with extended CT scale visualisation and the use of metal artefact reduction (MAR) software have been shown to overcome the limitations of metal artefact susceptibility in PMCT and enhance material differentiation in forensic odontology. Further benefits of DECT in forensic applications include improved soft-tissue visualisation, virtual bony subtraction and foreign body characterization. The literature supports the use of DECT in extending the benefits of PMCT for dental identification. Further systematic research is required to explore the use of DECT for material differentiation in forensic odontology.

There are increasing applications and use of spectral computed tomography or dual-energy computed tomography (DECT) in neuroradiology and head and neck imaging in routine clinical practice. Part 1 of this 2-part review covered fundamental physical principles underlying DECT scanning and the different approaches for scanning. Part 2 focuses on important and practical considerations for implementing and using DECT in clinical practice, including a review of different images and reconstructions produced by these scanners and important and practical issues, ranging from image quality and radiation dose to workflow-related aspects of DECT scanning, that routinely come up during operationalization of DECT.

There is recent interest in the use of dual-energy computed tomography (CT) in head and neck imaging, and the results are encouraging. This article reviews dual-energy CT applications as complementary tools to conventional CT scanning in the evaluation of cervical lymphadenopathy. The article cites the most relevant studies and highlights their results. Single-source and dual-source dual-energy applications including virtual noncontrast images, linear and nonlinear image blending, monochromatic images, iodine quantification, and spectral Hounsfield unit attenuation curve analysis are reviewed. Future directions and research suggestions are discussed in brief.

Dual-energy computed tomography (CT) has the potential to improve detection of abnormalities and increase diagnostic confidence in the evaluation of a variety of neurologic conditions by using different x-ray energy-dependent absorption behaviors of different materials. This article reviews the virtual monochromatic imaging applications of dual-energy CT, particularly material decomposition algorithms to improve lesion conspicuity, define lesion-normal tissue interface using different reconstruction techniques, and discuss miscellaneous emerging applications of dual-energy CT for neuroimaging, with an emphasis on their potential clinical utility.

There is increasing use of dual-energy computed tomography (DECT) for the evaluation of head and neck pathologic entities. Optimal DECT utilization requires familiarity with the appearance of normal tissues variants, and pathologic entities on different DECT reconstructions that may be used in clinical practice. The purpose of this article is to provide a practical, pictorial review of the appearance of normal anatomic structures and different neoplastic and nonneoplastic head and neck pathologic entities on commonly used DECT reconstructions.

In the last article of this issue, advanced analysis capabilities of DECT is reviewed, including spectral Hounsfield unit attenuation curves, virtual monochromatic images, material decomposition maps, tissue effective Z determination, and other advanced post-processing DECT tools, followed by different methods of analysis of the attenuation curves generated using DECT. The article concludes with exciting future horizons and potential applications, such as the use of the rich quantitative data in dual energy CT scans for texture or radiomic analysis and the use of machine learning methods for generation of prediction models using spectral data.

There is increasing use and popularity of dual-energy computed tomography (DECT) in many subspecialties in radiology. This article reviews the practical workflow implications of routine DECT scanning based on the experience at a single institution where a large percentage of elective neck CTs are acquired in DECT mode. The article reviews factors both on the production (technologist) and on the interpretation (radiologist) side, focusing on challenges posed and potential solutions for seamless workflow implementation.