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Purpose Dual‐energy computed tomography (DECT) has been proposed for quantification of hepatic iron concentration (IC). However, the lower limit of quantification (LLOQ) has not been established, limiting the clinical adoption of this technology. In this study, we aim to (a) establish the LLOQ using phantoms and (b) investigate the effects of patient size, dose level, energy combination, and reconstruction method. Methods Three phantom sizes and eight vials of ferric nitrate solution with IC ranging from 0 to 10 mg/ml were used. DECT scans were performed at 80/140 and 100/140Sn kVp, and using five different levels of CT dose index (CTDI). An image‐domain three‐material‐decomposition algorithm was used to calculate the IC. The LLOQ was determined based on the coefficient of variation from repeated measurements. Results The measured IC correlated strongly with the true IC in the small and medium phantoms (R2 of linear regression > 0.99) and moderately in the large phantom (0.8

OBJECTIVE. The purpose of this study was to determine the quantification accuracy of virtual unenhanced images and establish the lower limit of iodine quantification as a function of dose. MATERIAL...

PurposeTo investigate and quantify the potential benefits associated with the use of stopping-power-ratio (SPR) images created from dual-energy computed tomography (DECT) images for proton dose calculation in a clinical proton treatment planning system (TPS).Materials and MethodsThe DECT and single-energy computed tomography (SECT) scans obtained for 26 plastic tissue surrogate plugs were placed individually in a tissue-equivalent plastic phantom. Relative-electron density (ρe) and effective atomic number (Zeff) images were reconstructed from the DECT scans and used to create an SPR image set for each plug. Next, the SPR for each plug was measured in a clinical proton beam for comparison of the calculated values in the SPR images. The SPR images and SECTs were then imported into a clinical TPS, and treatment plans were developed consisting of a single field delivering a 10 × 10 × 10-cm3 spread-out Bragg peak to a clinical target volume that contained the plugs. To verify the accuracy of the TPS dose calculated from the SPR images and SECTs, treatment plans were delivered to the phantom containing each plug, and comparisons of point-dose measurements and 2-dimensional γ-analysis were performed.ResultsFor all 26 plugs considered in this study, SPR values for each plug from the SPR images were within 2% agreement with measurements. Additionally, treatment plans developed with the SPR images agreed with the measured point dose to within 2%, whereas a 3% agreement was observed for SECT-based plans. γ-Index pass rates were > 90% for all SECT plans and > 97% for all SPR image–based plans.ConclusionTreatment plans created in a TPS with SPR images obtained from DECT scans are accurate to within guidelines set for validation of clinical treatment plans at our center. The calculated doses from the SPR image–based treatment plans showed better agreement to measured doses than identical plans created with standard SECT scans.

Comparison of dual-source dual-energy CT (DS-DECT) and split-filter dual-energy CT (SF-DECT) regarding image quality and radiation dose in patients with suspected pulmonary embolism. We retrospectively analyzed pulmonary dual-energy CT angiography (CTPA) scans performed on two different CT scanners in 135 patients with suspected pulmonary embolism (PE). Scan parameters for DS-DECT were 90/Sn150 kV (n = 68 patients), and Au/Sn120 kV for SF-DECT (n = 67 patients). The iodine delivery rate was 1400 mg/s in the DS-DECT group vs. 1750 mg/s in the SF-DECT group. Color-coded iodine distribution maps were generated for both protocols. Objective (CT attenuation of pulmonary trunk [HU], signal-to-noise ratio [SNR], contrast-to-noise ratio [CNR]) and subjective image quality parameters (two readers [R], five-point Likert scale), as well as radiation dose parameters (effective radiation dose, size-specific dose estimations [SSDE]) were compared. All CTPA scans in both groups were of diagnostic image quality. Subjective CTPA image quality was rated as good or excellent in 80.9 %/82.4 % (R1 / R2) of DS-DECT scans, and in 77.6 %/76.1 % of SF-DECT scans. For both readers, the image quality of split-filter iodine distribution maps was significantly lower (p 0.05) with good or excellent ratings in only 43.3 %/46.3 % (R1 / R2) vs. 83.8 %/88.2 % for maps from DS-DECT. The HU values of the pulmonary trunk did not differ between the two techniques (p = n. s.), while both the SNR and CNR were significantly higher in the split-filter group (p 0.001; p = 0.003). Both effective radiation dose (2.70 ± 1.32 mSv vs. 2.89 ± 0.94 mSv) and SSDE (4.71 ± 1.63 mGy vs. 5.84 ± 1.11 mGy) were significantly higher in the split-filter group (p 0.05). The split-filter allows for dual-energy imaging of suspected pulmonary embolism but is associated with lower iodine distribution map quality and higher radiation dose. · The split-filter allows for dual-energy data acquisition from single-source single-layer CT scanners.. · Compared to the assessed dual-source dual-energy system, split-filter dual-energy imaging of a suspected pulmonary embolism is associated with lower iodine distribution map quality and higher radiation dose.. · Both the split-filter and the dual-source scanner provide diagnostic image quality in CTPA..· Petritsch B, Pannenbecker P, Weng AM et al. Comparison of Dual- and Single-Source Dual-Energy CT for Diagnosis of Acute Pulmonary Artery Embolism. Fortschr Röntgenstr 2021; 193: 427 - 436.ZIEL: Vergleich von Dual-Source-Dual-Energy-CT (DS-DECT) und Split-Filter-Dual-Energy-CT (SF-DECT) hinsichtlich objektiver und subjektiver Bildqualitätsparameter und Dosisexposition bei Patienten mit Verdacht auf eine Lungenarterienembolie (LAE). Es wurden 135 Patienten, welche bei Verdacht auf eine LAE eine pulmonale Dual-Energy-CT-Angiografie (CTPA) erhielten, in die retrospektive Studie eingeschlossen. Die Scan-Parameter waren 90/Sn150 kV beim DS-DECT- (n = 68 Patienten) und Au/Sn120 kV beim SF-DECT-System (n = 67 Patienten). Die Jod-Injektionsrate betrug 1400 mg/s in der DS-DECT-Gruppe vs. 1750 mg/s in der SF-DECT. Farbkodierte Jod-Distributionskarten wurden für beide Protokolle berechnet. Es wurden die objektive (CT-Abschwächung im Truncus pulmonalis (HU), Signal-Rausch-Verhältnis (SNR), Kontrast-Rausch-Verhältnis (CNR)) und subjektive Bildqualität (2 Auswerter (R), 5-Punkte-Likert-Skala) sowie Dosisparameter (effektive Dosis, größenspezifische Dosiseinschätzungen (SSDE)) erhoben und verglichen. In beiden Gruppen waren alle CTPAs von diagnostischer Qualität. Die subjektive Bildqualität der CTPA wurde in 80,9/82,4 % (R1 / R2) der DS-DECT und in 77,6 %/76,1 % der SF-DECT als gut oder exzellent bewertet. Die Qualität der Jod-Distributionskarten der DS-DECT wurde in 83,8/88,2 % als gut oder exzellent bewertet. Beide Auswerter bewerteten die Qualität der Jod-Distributionskarten der SF-DECT signifikant niedriger (p 0,05), wobei nur in 43,3/46,3 % (R1 / R2) eine gute oder exzellente Qualität vorlag. Die HU-Werte im Truncus pulmonalis waren zwischen beiden Gruppen ähnlich (p = n. s.), während SNR und CNR in der Split-Filter-Gruppe signifikant höher waren (p 0,001; p = 0,003). Sowohl die effektive Dosis (2,70 ± 1,32 mSv vs. 2,89 ± 0,94 mSv) als auch die SSDE (4,71 ± 1,63 mGy vs. 5,84 ± 1,11 mGy) waren in der Split-Filter-Gruppe signifikant höher (p 0,05). Bei Verdacht auf eine Lungenembolie ermöglicht der Split-Filter eine Dual-Energy-Untersuchung an Single-Source-CT-Scannern, ist aber mit einer schlechteren Qualität der Jod-Distributionskarten und einer höheren Dosisexposition vergesellschaftet. · Der Split-Filter ermöglicht eine Dual-Energy-Datenakquisition an Single-Source-Single-Layer-CT-Scannern.. · Verglichen mit dem untersuchten Dual-Source-Dual-Energy-System ist die pulmonale Split-Filter-Dual-Energy-CT mit einer schlechteren Qualität der Jod-Distributionskarten und einer höheren Dosisexposition vergesellschaftet.. · Sowohl der Split-Filter als auch der Dual-Source-Scanner ermöglichen eine CTPA in diagnostischer Bildqualität..

To evaluate the feasibility of producing 2-dimensional (2D) virtual noncontrast images and 3-dimensional (3D) bone models from dual-energy computed tomography (DECT) arthrograms and to determine whether this is best accomplished using 190 keV virtual monoenergetic images (VMI) or virtual unenhanced (VUE) images. VMI and VUE images were retrospectively reconstructed from patients with internal derangement of the shoulder or knee joint who underwent DECT arthrography between September 2017 and August 2019. A region of interest was placed in the area of brightest contrast, and the mean attenuation (in Hounsfield units [HUs]) was recorded. Two blinded musculoskeletal radiologists qualitatively graded the 2D images and 3D models using scores ranging from 0 to 3 (0 considered optimal). Twenty-six patients (mean age ± SD, 57.5 ± 16.8 years; 6 women) were included in the study. The contrast attenuation on VUE images (overall mean ± SD, 10.5 ± 16.4 HU; knee, 19.3 ± 10.7 HU; shoulder, 5.0 ± 17.2 HU) was significantly lower (p

PURPOSE: We aimed to evaluate whether rapid kV-switching dual energy CT (rsDECT) can discriminate between papillary renal cell carcinoma (RCC) and benign proteinaceous cysts (BPCs) based on iodine and water content. METHODS: Twenty-four patients with histopathologically proven papillary RCC and 38 patients with 41 BPCs were retrospectively included. Patients with BPCs were eligible for inclusion when the cysts were stable in size and appearance for at least 2 years or proved to be a cyst on ultrasound or MRI. All patients underwent delayed phase (70–90 s) rsDECT. Iodine and water content of each lesion was measured on the workstation. RESULTS: Of papillary RCC patients, 4 (16%) were female and 20 (84%) were male. Mean tumor size was 39±20 mm. Mean iodine and water content was 2.08±0.7 mg/mL and 1021±14 mg/mL, respectively. Of BPC patients, 9 were female and 29 were male. Mean cyst size was 20±7 mm. Mean iodine and water content was 0.82±0.4 mg/mL and 1012±14 mg/mL, respectively. There were significant differences between iodine and water contents of papillary RCCs and BPCs (P < 0.001). The best cutoff of iodine content for differentiating papillary RCC from BPC was 1.21 mg/mL (area under the curve [AUC]=0.97, P < 0.001, sensitivity 96%, specificity 88%, positive predictive value [PPV] 82%, negative predictive value [NPV] 97%, accuracy 91%,); the best cutoff of water content was 1015.5 mg/mL (AUC=0.68, P = 0.016, sensitivity 83%, specificity 56%, PPV 52%, NPV 85%, accuracy 66%). CONCLUSION: An iodine content threshold of 1.21 mg/mL accurately differentiates papillary RCC from BPCs on a single postcontrast rsDECT. Despite having a high sensitivity, water content has inferior diagnostic accuracy.

This study evaluated the calcium blooming-reducing effect and the differences of luminal diameter among various-energy virtual monochromatic images (VMIs) using rapid kilovolt-switching dual-energy computed tomography (DECT). Forty-five calcified segments in 31 patients were analyzed. For the analysis, 40- to 140-keV VMIs on both non-contrast CT and coronary CT angiography were generated at 10-keV steps, and calcification size and luminal diameter were measured using CT number profile curve and full-width at half-maximum method. We compared calcification size and luminal diameter on each keV VMIs with those on 70-keV VMI. There was no significant differences among the 40- to 140-keV VMIs regarding calcification size or luminal diameter. The 40- to 140-keV VMIs produced by single-source DECT had no effect on the calcification size or luminal diameter in the coronary artery.

OBJECTIVE. This study assessed a machine learning-based dual-energy CT (DECT) tumor analysis prototype for semiautomatic segmentation and radiomic analysis of benign and malignant liver lesions seen on contrast-enhanced DECT. MATERIALS AND METHODS. This institutional review board-approved study included 103 adult patients (mean age, 65 ± 15 [SD] years; 53 men, 50 women) with benign (60/103) or malignant (43/103) hepatic lesions on contrast-enhanced dual-source DECT. Most malignant lesions were histologically proven; benign lesions were either stable on follow-up CT or had characteristic benign features on MRI. Low- and high-kilovoltage datasets were deidentified, exported offline, and processed with the DECT tumor analysis for semiautomatic segmentation of the volume and rim of each liver lesion. For each segmentation, contrast enhancement and iodine concentrations as well as radiomic features were derived for different DECT image series. Statistical analyses were performed to determine if DECT tumor analysis and radiomics can differentiate benign from malignant liver lesions. RESULTS. Normalized iodine concentration and mean iodine concentration in the benign and malignant lesions were significantly different (p < 0.0001-0.0084; AUC, 0.695-0.856). Iodine quantification and radiomic features from lesion rims (AUC, ≤ 0.877) had higher accuracy for differentiating liver lesions compared with the values from lesion volumes (AUC, ≤ 0.856). There was no difference in the accuracies of DECT iodine quantification (AUC, 0.91) and radiomics (AUC, 0.90) for characterizing liver lesions. CONCLUSION. DECT radiomics were more accurate than iodine quantification for differentiating solid benign and malignant hepatic lesions.

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).

Purpose Early infarcts are hard to diagnose on non-contrast head CT. Dual-energy CT (DECT) may potentially increase infarct differentiation. The optimal DECT settings for differentiation were identified and evaluated. Methods One hundred and twenty-five consecutive patients who presented with suspected acute ischemic stroke (AIS) and underwent non-contrast DECT and subsequent DWI were retrospectively identified. The DWI was used as reference standard. First, virtual monochromatic images (VMI) of 25 patients were reconstructed from 40 to 140 keV and scored by two readers for acute infarct. Sensitivity, specificity, positive, and negative predictive values for infarct detection were compared and a subset of VMI energies were selected. Next, for a separate larger cohort of 100 suspected AIS patients, conventional non-contrast CT (NCT) and selected VMI were scored by two readers for the presence and location of infarct. The same statistics for infarct detection were calculated. Infarct location match was compared per vascular territory. Subgroup analyses were dichotomized by time from last-seen-well to CT imaging. Results A total of 80–90 keV VMI were marginally more sensitive (36.3–37.3%) than NCT (32.4%; p > 0.680), with marginally higher specificity (92.2–94.4 vs 91.1%; p > 0.509) for infarct detection. Location match was superior for VMI compared with NCT (28.7–27.4 vs 19.5%; p p = 0.004) than NCT, whereas after 4.5 h, 90 keV VMI was more accurate (69.3 vs 66.3%). Conclusion Non-contrast 80–90 keV VMI best differentiates normal from infarcted brain parenchyma.

Purpose Several dual‐energy computed tomography (DECT) techniques require a deformable image registration to correct for motion between the acquisition of low and high energy data. However, current DECT software does not provide tools to assess registration accuracy or allow the user to export deformed images, presenting a unique challenge for image registration quality assurance (QA). This work presents a methodology to evaluate the accuracy of DECT deformable registration and to quantify the impact of registration errors on end‐product images. Methods The deformable algorithm implemented in Siemen Healthineers's Syngo was evaluated using a deformable abdomen phantom and a rigid phantom to mimic sliding motion in the thorax. Both phantoms were imaged using sequential 80 and 140 kVp scans with motion applied between the two scans. Since Syngo does not allow the export of the deformed images, this study focused on quantifying the accuracy of various end‐product, dual‐energy images resulting from processing of deformed images. Results The Syngo algorithm performed well for the abdomen phantom with a mean registration error of 0.4 mm for landmark analysis, Dice similarity coefficients (DSCs) > 0.90 for five organs contoured, and mean iodine concentrations within 0.2 mg/mL of values measured on static images. For rigid sliding motion, the algorithm performed poorer and resulted in noticeable registration errors toward the superior and inferior scan extents and DSCs as low as 0.41 for iodine rods imaged in the phantom. Additionally, local iodine concentration errors in areas of misregistration exceeded 3 mg/mL. Conclusions This work represents the first methodology for DECT image registration QA using commercial software. Our data support the clinical use of the Syngo algorithm for abdominal sites with limited motion (i.e., pancreas and liver). However, dual‐energy images generated with this algorithm should be used with caution for quantitative measurements in areas with sliding motion.

Conventional computed tomography (CT) plays an important role in detection of lung nodules. However, further characterization is usually limited requiring additional imaging and invasive work up. Spectral Detector CT (SDCT) is an upcoming novel modality that not only allows morphological evaluation but also provides insight into prediction of malignant behavior of lung nodules. Additional quantification capabilities available from the same scan make it a more comprehensive imaging option in oncology patients. This is a first case report demonstrating the potential of single SDCT to provide necessary information for lung cancer diagnosis and preoperative planning, comparable to standard of care imaging.

Metastatic pulmonary calcification is an underdiagnosed metabolic lung disease characterized by diffuse calcium deposition in the lungs, often associated with secondary hyperparathyroidism due to chronic renal failure. A 31-year-old man with chronic renal failure initially presented with diffuse pain symptoms, deterioration of general condition, and respiratory insufficiency. Noncontrast-enhanced computed tomography of the chest was performed using a spectral-detector-based dual-energy CT. It showed multiple, centrilobular, ground-glass opacities, and nodules, ultimately leading to the diagnosis. Calcium suppression proved to be highly useful to classify the pulmonary alterations.

To compare intravenous contrast material (CM) injection protocols for dual-energy CT pulmonary angiography (CTPA) in patients with suspected acute pulmonary embolism with regard to image quality and pulmonary perfused blood volume (PBV) values. A total of 198 studies performed with four CM injection protocols varying in CM volume and iodine delivery rates (IDR) were retrospectively included: (A) 60 ml at 5 ml/s (IDR = 1.75gI/s), (B) 50 ml at 5 ml/s (IDR = 1.75gI/s), (C) 50 ml at 4 ml/s (IDR = 1.40gI/s), (D) 40 ml at 3 ml/s (IDR = 1.05gI/s). Image quality and PBV values at different resolution settings were compared. Pulmonary arterial tract attenuation was highest for protocol A (397 ± 110 HU; p vs. B = 0.13; vs. C = 0.02; vs. D p = 0.01; p p p = 0.10; 0.10; 0.09), while otherwise PBV values displayed a decreasing trend from protocol A to D (p

Dual energy computed tomography (DECT), also known as spectral CT, refers to advanced CT technology that separately acquires high and low energy X-ray data to enable material characterization applications for substances that exhibit different energy-dependent x-ray absorption behavior. DECT supports a variety of post-processing applications that add value in routine clinical CT imaging, including material selective and virtual non-contrast images using two- and three-material decomposition algorithms, virtual monoenergetic imaging, and other material characterization techniques. Following a review of acquisition and post-processing techniques, we present a case-based approach to highlight the added value of DECT in common clinical scenarios. These scenarios include improved lesion detection, improved lesion characterization, improved ease of interpretation, improved prognostication, inherently more robust imaging protocols to account for unexpected pathology or suboptimal contrast opacification, length of stay reduction, reduced utilization by avoiding unnecessary follow-up examinations, and radiation dose reduction. A brief discussion of post-processing workflow approaches, challenges, and solutions is also included.

OBJECTIVE. The clumpy artifact has a high misdiagnosis rate, but the artifact has not been well studied. The aims of this study were to evaluate the frequency and location of clumpy artifacts, the rate of misdiagnosis of clumpy artifacts as gout, and the effects of raising the minimum attenuation value and using a selective photon shield in dual-energy CT (DECT). MATERIALS AND METHODS. Forty patients without gout who underwent foot and ankle DECT were enrolled in this study. Images in both sets were randomly assigned a minimum attenuation of 130 HU or 150 HU. Three radiologists independently checked all images for presence, volume, and location of green color-coded pixelation and graded their findings according to a 4-point confidence scale, frequency, and volume. Misdiagnosis rate and misdiagnosis score were compared using the Wilcoxon signed rank and McNemar tests. RESULTS. In set 1, the frequency of clumpy artifacts in DECT with the minimum attenuation set to 130 HU and 150 HU were 81% and 68%, respectively. For all three readers, the misdiagnosis rate and misdiagnosis score decreased when changing the minimum attenuation from 130 HU to 150 HU. In set 2, with the minimum attenuation set to 130 HU, the frequency of the clumpy artifact was 44%; with the minimum attenuation set to 150 HU, no clumpy artifacts were seen. CONCLUSION. Clumpy artifacts occurred frequently in DECT without a tin filter. Setting the minimum attenuation to the higher value of 150 HU reduced the frequency of clumpy artifacts, and adding a tin filter to DECT greatly reduced their occurrence.

AIM: To investigate possible differences between surgeons and radiologists in selecting optimal photon energy settings from a set of virtual monochromatic dual-energy computed tomography (CT) images for the assessment of bone union in patients with a suspected non-union of the appendicular skeleton. MATERIALS AND METHODS: Fifty patients suspected of having bone non-union after operative fracture treatment with a variety of fixation implants were included. Patients were scanned on a dual-source CT machine using 150/100-kVp. Monochromatic images were extracted at 70, 90, 110, 130, 150, and 190 keV. Images were reviewed by 159 orthopaedic trauma surgeons and 12 musculoskeletal radiologists in order to select the best and worst energy setting to assess bone union. Furthermore, a confidence score (1–4) was given in selecting the best and worst setting to assess bone union. RESULTS: Monochromatic 190 keV images were selected most frequently as the optimal energy in titanium (34.8%), stainless steel (40%), and combined implants of stainless steel and titanium (40.5%). Confidence scores and average optimal energies were higher and average worst energies were lower for radiologists compared to surgeons in all hardware (p

Background Dual-energy computed tomography (DE-CT) scans were acquired to identify cholesterol and adenomatous gallbladder (GB) polyps, which have not been well evaluated before surgery. Purpose To evaluate the DE-CT findings of GB polyps 1.0–2.0 cm in size and differentiate between cholesterol and adenomatous polyps. Material and Methods Forty-six patients with GB polyps were surgically treated from December 2017 to December 2019 and divided into two groups according to their postoperative pathologic results: a cholesterol group with 26 patients and an adenomatous group with 20 patients. All of these patients underwent DE-CT imaging with tube voltages of 80 kVp and 140 kVp within two weeks before surgery. Mean attenuation values were measured for every GB polyp at 80/140 kVp and at 40/140 keV. The mean attenuation value changes between 140 kVp and 80 kVp (MAVC140–80 kVp) and mean attenuation value changes between 100 keV and 40 keV (MAVC100–40 keV) were calculated. Results The CT image parameters of all 46 patients with GB polyps were analyzed. There were significant differences in MAVC140–80 kVp and MAVC100–40 keV between cholesterol and adenomatous polyps ( P Conclusion The unique energy spectrum information provided by DE-CT scans is helpful in differentiating between cholesterol and adenomatous polyps 1.0–2.0 cm in size.

OBJECTIVE. The purpose of this article is to outline the utility of iodine density maps for evaluating cardiothoracic disease and abnormalities. Multiple studies have shown that the variety of images generated from dual-energy spectral detector CT (SDCT) improve identification of cardiothoracic conditions. CONCLUSION. Understanding the technique of SDCT and being familiar with the features of different cardiothoracic conditions on iodine density map images help the radiologist make a better diagnosis.

OBJECTIVE. The objective of this study was to demonstrate the feasibility of dual-energy CT (DECT) for locoregional staging of breast cancer and differentiation of tumor histotypes. MATERIALS AND METHODS. From January 2016 to July 2017, a total of 31 patients (mean [± SD] age, 55.8 ± 14.8 years) with breast cancer diagnosed by needle biopsy who underwent preoperative contrast-enhanced DECT for staging purposes were selected from a retrospective review of institutional databases. Monochromatic images obtained at 40 and 70 keV were evaluated by two readers who determining the number of hypervascularized tumors present and the largest tumor diameter for each breast. The attenuation values and iodine concentration of tumors and normal breast tissue and the ratios of these findings in each tissue type were recorded. Cancers were classified as ductal carcinoma in situ, invasive ductal carcinoma, and invasive lobular carcinoma. The reference standard was the final pathologic finding after surgery. RESULTS. A total of 64 tumor lesions were found at histopathologic analysis versus 67 on DECT for 34 breasts (three bilateral cancers were included). Nonparametric statistics were used. The largest lesion diameter observed DECT was 33.2 ± 20.5 mm versus 31.8 ± 20.5 mm on pathologic analysis, and cancer distribution was correctly classified for 31 of 34 (91%) cases. ROC curves derived from lesion iodine concentration showed that the optimal thresholds for distinguishing infiltrating carcinomas (invasive lobular and ductal carcinomas) and from other lesions were 1.70 mg/mL (sensitivity, 94.9%; specificity, 93.0%; AUC value, 0.968). ROC curves derived from the ratio of the iodine concentration in lesions to that in normal breast parenchyma showed that 6.13 was the optimal threshold to distinguish invasive ductal carcinoma from other lesions (sensitivity, 87.0%; specificity, 81.1%; AUC value, 0.914). CONCLUSION. DECT is feasible and seems to be a reliable tool for locoregional staging of breast cancer.

To evaluate the role of conventional contrast-enhanced CT (CECT) imaging and dual-energy spectral CT (DECT) perfusion imaging in differentiating the WHO histological subtypes of thymic epithelial tumours (TETs). Eighty-eight patients with TETs who underwent DECT perfusion scans (n = 51) and conventional CT enhancement scans (n = 37) using a GE Discovery CT750 HD scanner were enrolled in this study. The mean maximal contrast-enhanced range (mean CEmax) and the perfusion and spectral parameters of the lesions were analysed. Among the six WHO subtypes (Type A, AB, B1, B2, and B3 thymoma and thymic carcinoma), the mean CEmax values and most of the perfusion and spectral parameter values of Type A and Type AB were significantly higher than those of the other subtypes (all P 0.05). The mean CEmax value was not different between Type B (including Type B1, B2, and B3) and thymic carcinoma (P = 1.000). The PS, IC, NIC and λHU values in the optimal venous phase of thymic carcinoma were higher than those of Type B (all P

The purpose of this work was to develop and validate a Monte Carlo model for a Dual Source Computed Tomography (DSCT) scanner based on the Monte Carlo N-particle radiation transport computer code (MCNP5). The geometry of the Siemens Somatom Definition CT scanner was modeled, taking into consideration the x-ray spectrum, bowtie filter, collimator, and detector system. The accuracy of the simulation from the dosimetry point of view was tested by calculating the Computed Tomography Dose Index (CTDI) values. Furthermore, typical quality assurance phantoms were modeled in order to assess the imaging aspects of the simulation. Simulated projection data were processed, using the MATLAB software, in order to reconstruct slices, using a Filtered Back Projection algorithm. CTDI, image noise, CT-number linearity, spatial and low contrast resolution were calculated using the simulated test phantoms. The results were compared using several published values including IMPACT, NIST and actual measurements. Bowtie filter shapes are in agreement with those theoretically expected. Results show that low contrast and spatial resolution are comparable with expected ones, taking into consideration the relatively limited number of events used for the simulation. The differences between simulated and nominal CT-number values were small. The present attempt to simulate a DSCT scanner could provide a powerful tool for dose assessment and support the training of clinical scientists in the imaging performance characteristics of Computed Tomography scanners.

ZusammenfassungUntersuchungen zur Anwendung der monochromen (MC) Bildgebung nach Implantation metallischer Materialien an den Extremitäten oder der Wirbelsäule haben gezeigt, dass dadurch verursachte Artefakte deutlich reduziert werden können. Aufgrund der hohen Ordnungszahlen und der hohen Dichte der in der Kieferorthopädie, Kieferchirurgie und Zahnerhaltung verwendeten Materialien stellen Aufhärtungsartefakte ein großes Problem bei der Computertomografie-Bildgebung (CT) der Zähne und des Kiefers dar. Die verursachten Einschränkungen der Bildqualität bei der Darstellung der Kiefer und denkbare Verbesserungsmöglichkeiten sind bisher unzureichend untersucht. Das Ziel dieser Arbeit war, die oben genannten Artefakte zu untersuchen und diese durch Erzeugung von Monochromen im Zahn- und Kieferbereich zu reduzieren. Dual-Energy-Computertomografien (DECTs) wurden an 10 Leichenköpfen mit und ohne kieferorthopädische Apparatur durchgeführt. Anschließend wurden MC von 80 bis 160 kV generiert. Die Artefakte wurden mit etablierten Methoden qualitativ und quantitativ beurteilt. An anatomischen Strukturen wie dem Mundboden und dem weichen Gaumen, die sich nicht in der gleichen axialen Ebene mit stark artefaktproduzierenden Objekten mit hoher Ordnungszahl befinden, konnte mit zunehmender kV-Zahl der MC eine Zunahme der Hounsfieldeinheiten (HE) beobachtet werden. An Strukturen in der gleichen Ebene mit artefaktproduzierenden Objekten konnte mit zunehmender kV-Zahl der MC eine Abnahme der HE beobachtet werden. Diese Studie zeigt, dass es auch im Kieferbereich möglich ist mittels MC Artefaktreduktion zu betreiben. In allen Untersuchungen konnten keine signifikant erhöhten Artefakte im Setting mit KFO-Apparatur im Vergleich zum Setting ohne KFO-Apparatur festgestellt werden.

Background and purpose Proton treatment planning relies on an accurate determination of stopping-power ratio (SPR) from x-ray computed tomography (CT). A refinement of the heuristic CT-based SPR prediction using a state-of-the-art Hounsfield look-up table (HLUT) is proposed, which incorporates patient SPR information obtained from dual-energy CT (DECT) in a retrospective patient-cohort analysis. Material and methods SPR datasets of 25 brain-tumor patients, 25 prostate-cancer patients, and three nonsmall cell lung-cancer (NSCLC) patients were calculated from clinical DECT scans with the comprehensively validated DirectSPR approach. Based on the median frequency distribution of voxelwise correlations between CT number and SPR within the irradiated volume, a piecewise linear function was specified (DirectSPR-based adapted HLUT). Differences in dose distribution and proton range were assessed for the nonadapted and adapted HLUT in comparison to the DirectSPR method, which has been shown to be an accurate and reliable SPR estimation method. Results The application of the DirectSPR-based adapted HLUT instead of the nonadapted HLUT reduced the systematic proton range differences from 1.2% (1.1 mm) to -0.1% (0.0 mm) for brain-tumor patients, 1.7% (4.1 mm) to 0.2% (0.5 mm) for prostate-cancer patients, and 2.0% (2.9 mm) to -0.1% (0.0 mm) for NSCLC patients. Due to the large intra- and inter-patient tissue variability, range differences to DirectSPR larger than 1% remained for the adapted HLUT. Conclusions The incorporation of patient-specific correlations between CT number and SPR, derived from a retrospective application of DirectSPR to a broad patient cohort, improves the SPR accuracy of the current state-of-the-art HLUT approach. The DirectSPR-based adapted HLUT has been clinically implemented at the University Proton Therapy Dresden (Dresden, Germany) in 2017. This already facilitates the benefits of an improved DECT-based tissue differentiation within clinical routine without changing the general approach for range prediction (HLUT), and represents a further step toward full integration of the DECT-based DirectSPR method for treatment planning in proton therapy.

Purpose: In this systematic review and meta-analysis, we aimed to investigate the accuracy of dual-energy computed tomography (DECT) in the detection of acute pulmonary embolism (PE). Methods: We searched Medline (via PubMed), EBSCO, Web of Science, Scopus, and the Cochrane Library for relevant published studies. We selected studies assessing the accuracy of DECT in the detection of PE. Quality assessment of bias and applicability was conducted using the Quality of Diagnostic Accuracy Studies-2 tool. Meta-analysis was performed to calculate mean estimates of sensitivity, specificity, positive likelihood ratio (PLR), and negative likelihood ratio (NLR). The summary receiver operating characteristic (sROC) curve was drawn to get the Cochran Q-index and the area under the curve (AUC). Results: Seven studies were included in our systematic review. Of the 182 patients included, 108 patients had PEs. The pooled analysis showed an overall sensitivity and specificity of 88.9% (95% confidence interval [CI]: 81.4%-94.1%) and 94.6% (95% CI: 86.7%-98.5%), respectively. The pooled PLR was 8.186 (95% CI: 3.726-17.986), while the pooled NLR was 0.159 (95% CI: 0.093-0.270). Cochran-Q was 0.8712, and AUC was 0.935 in the sROC curve. Conclusion: Dual-energy computed tomography shows high sensitivity, specificity, and diagnostic accuracy in the detection of acute PE. The high PLR highlights the high clinical importance of DECT as a prevalence-independent, rule-in test. Studies with a larger sample size with standardized reference tests are still needed to increase the statistical power of the study and support these findings.

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.

To determine whether dual energy CT (DECT) scanning can aid in the differentiation between acute traumatic and pathologic fractures of the pelvis and long bones. Retrospective review of 11 patients with 15 pathologic fractures proven by biopsy and/or other advanced imaging modalities. Age- and sex-matched patients with non-pathologic traumatic fractures were used as controls. Studies were reviewed by two readers on syngo.via software before and after the creation of virtual bone marrow color maps. Hounsfield units (HU) of the marrow space at the level of the fracture were recorded on both reviews. Differences between the HU of the bone marrow of traumatic and pathologic fractures were compared using two-tailed unpaired t-test. A statistically significant difference was found in the HU of the affected bone marrow on DECT virtual noncalcium bone marrow color maps between the pathologic group (mean HU:4.89) and the non-pathologic group (mean HU: − 286.2) (p = 0.0177). HU measurements on the mixed kVp images were 150.4 for the pathologic and 94.1 for the non-pathologic fracture groups, respectively, with no statistical significance (p = 0.272). DECT scanning can aid in the differentiation between hematoma at acute traumatic fracture sites and neoplasm at pathologic fracture sites. HU of the bone marrow is higher for pathologic fractures, and the difference in bone marrow attenuation is more evident on the virtual bone marrow color maps.

To evaluate the cost-effectiveness of DECT versus multiphasic CT and MRI for characterizing small incidentally detected indeterminate renal lesions using a Markov Monte Carlo decision-analytic model. Incidental renal lesions are commonly encountered due to the increasing utilization of medical imaging and the increasing prevalence of renal lesions with age. Currently recommended imaging modalities to further characterize incidental indeterminate renal lesions have some inherent drawbacks. Single-phase DECT may overcome these limitations, but its cost-effectiveness remains uncertain. A decision-analytic (Markov) model was constructed to estimate life expectancy and lifetime costs for otherwise healthy 64-year-old patients with small (≤ 4 cm) incidentally detected, indeterminate renal lesions on routine imaging (e.g., ultrasound or single-phase CT). Three strategies for evaluating renal lesions for enhancement were compared: multiphase SECT (e.g., true unenhanced and nephrographic phase), multiphasic MRI, and single-phase DECT (nephrographic phase in dual-energy mode). The model incorporated modality-specific diagnostic test performance, incidence, and prevalence of incidental renal cell carcinomas (RCCs), effectiveness, costs, and health outcomes. An incremental cost-effectiveness analysis was performed to identify strategy preference at willingness-to-pay (WTP) thresholds of $50,000 and $100,000 per quality-adjusted life-year (QALY) gained. Deterministic and probabilistic sensitivity analysis were performed. In the base case analysis, expected mean costs per patient undergoing characterization of incidental renal lesions were $2567 for single-phase DECT, $3290 for multiphasic CT, and $3751 for multiphasic MRI. Associated quality-adjusted life-years were the highest for single-phase DECT at 0.962, for multiphasic MRI it was 0.940, and was the lowest for multiphasic CT at 0.925. Because of lower associated costs and higher effectiveness, the single-phase DECT strategy dominated the other two strategies. Single-phase DECT is potentially more cost-effective than multiphasic SECT and MRI for evaluating small incidentally detected indeterminate renal lesions.

Purpose Dual-energy computed tomography (DECT) has shown great potential in many clinical applications. By incorporating the information from two different energy spectra, DECT provides higher contrast and reveals more material differences of tissues compared to conventional single-energy CT (SECT). Recent research shows that automatic multi-organ segmentation of DECT data can improve DECT clinical applications. However, most segmentation methods are designed for SECT, while DECT has been significantly less pronounced in research. Therefore, a novel approach is required that is able to take full advantage of the extra information provided by DECT. Methods In the scope of this work, we proposed four three-dimensional (3D) fully convolutional neural network algorithms for the automatic segmentation of DECT data. We incorporated the extra energy information differently and embedded the fusion of information in each of the network architectures. Results Quantitative evaluation using 45 thorax/abdomen DECT datasets acquired with a clinical dual-source CT system was investigated. The segmentation of six thoracic and abdominal organs (left and right lungs, liver, spleen, and left and right kidneys) were evaluated using a fivefold cross-validation strategy. In all of the tests, we achieved the best average Dice coefficients of 98% for the right lung, 98% for the left lung, 96% for the liver, 92% for the spleen, 95% for the right kidney, 93% for the left kidney, respectively. The network architectures exploit dual-energy spectra and outperform deep learning for SECT. Conclusions The results of the cross-validation show that our methods are feasible and promising. Successful tests on special clinical cases reveal that our methods have high adaptability in the practical application.

Background: Bone marrow edema is assumed to be caused as a result of trabecular microfractures that are detected by MRI. As MRI is not widely available in countries like India, this study aims to encourage the use of DECT in detection of bone edema as evidence with comparable efficiency to MRI. Aim: To assess the diagnostic accuracy of dual-energy CT in detecting bone marrow edema in patients of trauma of lower limb and correlate it with MRI. Setting and Design: It is a cross-sectional study. Materials and Methods: The study included 40 patients of age 15–70 years irrespective of sex. All the patients of lower extremity trauma underwent DECT and MRI evaluation after clinical evaluation. All the images were postprocessed on a work station and were further evaluated by a radiologist. Results: Mean attenuation at fractured site observed by Dual energy CT was found to be significantly higher as compared to that at adjacent site (170.75 ± 33.99 vs. 19.73 ± 22.50 HU). The sensitivity and specificity of dual energy CT as compared to MRI in detecting bone marrow edema were 94.1% and 91.3%, respectively. Of the 40 cases enrolled in the study, agreement of MRI and Dual energy CT was observed in 37 (92.5%). Conclusion: Dual energy CT can be an effective alternative to MRI in the detection of bone marrow edema in patients of lower limb trauma. Dual energy CT can also be used in patients in whom MRI is contraindicated.

PURPOSE A virtual monochromatic image (VMI) is acquired from two different types of polychromatic energy X-rays, not a monochromatic X-ray. The effective energy of monochromatic X-ray does not vary in passing through the patient's body. On the other hand, beam hardening effects are seen in images because of the change of polychromatic X-ray energy. The purpose of the present study was to evaluate the beam hardening improvement effect of VMI using a phantom with a bone mimicking ring. METHOD We used a water equivalent electron density phantom with a hole in the center for inserting various measurement materials (i.e. fat, two types of bone with differing densities, contrast medium, blood, and water). Then, the CT numbers of each measurement materials were obtained from single energy CT (SECT) images and VMIs, respectively. Also, an additional bone-mimetic ring was used to obtain the CT numbers for evaluation of beam hardening effect. The CT number change rates were calculated from the obtained CT numbers with and without beam hardening effect. RESULT The rate of CT number, change of VMI was significantly lower than that of SECT for all measured materials. CONCLUSION In this study, VMI minimized changes in CT numbers due to the beam hardening effect and showed a higher beam hardening reduction effect.

Purpose The objective of this study was to assess synthesized effective atomic number (Z eff ) values with a new developed tissue characteristic phantom and contrast material of varying iodine concentrations using single-source fast kilovoltage switching dual-energy CT (DECT) scanner. Methods A newly developed multi energy tissue characterisation CT phantom and an acrylic phantom with various iodine concentrations of were scanned using single-source fast kilovoltage switching DECT (GE-DECT) scanner. The difference between the measured and theoretical values of Z eff were evaluated. Additionally, the difference and coefficient of variation (CV) values of the theoretical and measured values were compared with values obtained with the Canon-DECT scanner that was analysed in our previous study. Results The average Z eff difference in the Multi-energy phantom was within 4.5%. The average difference of the theoretical and measured Z eff values for the acrylic phantom with variation of iodine concentration was within 3.3%. Compared to the results for the single-source Canon-DECT scanner used in our previous study, the average difference and CV of the theoretical and measured Z eff values obtained with the GE-DECT scanner were markedly smaller. Conclusions The accuracy of the synthesized Z eff values with GE-DECT had a good agreement with the theoretical Z eff values for the Multi-Energy phantom. The GE-DECT could reduce the noise and the accuracy of the Z eff values than that with Canon-DECT for the varying iodine concentrations of contrast medium. Advances in knowledge The accuracy and precision of the Z eff values of the contrast medium with the GE-DECT could be sufficient with human equivalent materials.

Background Virtual monoenergetic (VM) dual-energy computed tomography (DE-CT) enables grey-to-white matter contrast-to-noise ratio optimization, potentially increasing ischaemic brain oedema visibility. The aim of this study was to compare the diagnostic accuracy of VM and standard DE-CT reconstructions for early stroke detection. Methods Consecutive patients with non-contrast DE-CT of the brain scanned within 12 h of stroke symptom onset were prospectively included in the study. Patients with other significant brain pathology were excluded. Two radiologists jointly evaluated standard and VM reconstructions (from 40 to 190 keV at increments of 10 keV) for early stroke signs on a four-point Likert scale: (a) stroke definitely present, (b) stroke probably present, (c) probably no stroke, and (d) definitely no stroke. Follow-up imaging and clinical data served as the standard of reference. Diagnostic accuracy was evaluated by receiver operating characteristic analysis. Results Stroke incidence among 184 patients was 76%. In 64 patients follow-up imaging served as the standard of reference: ischemic brain oedema detection was significantly more accurate on VM reconstructions at 80 keV compared with standard DE-CT reconstructions (area under the curve (AUC) = 0.821 vs. AUC = 0.672, p = 0.002). The difference was most prominent within the first 3 h after symptom onset (at 11%, AUC = 0.819 vs. AUC = 0.709, p = 0.17) and in patients with National Institutes of Health Stroke Scale above 16 (at 37.5%, AUC = 1 vs. AUC = 0.625, p = 0.14). Conclusion VM DE-CT reconstructions at 80 keV appear to be the optimal non-contrast CT technique for diagnosing early ischaemic stroke, particularly within the first 3 h after symptom onset and in severely ill patients.

Objective To evaluate the image quality of dual energy CT (DECT) of the shoulder after arthrography and of virtual non-contrast (VNC) 3D reformats of the glenoid and to compare glenoid measurements on VNC 3D reformats and on 2D CTs. Materials and methods DECT arthrography (80 kV/140 kV) was performed in 42 shoulders of 41 patients with instability using diluted iodinated contrast media (80 mg/ml). VNC images and VNC 3D reformats of the glenoid were calculated using image postprocessing. Dose parameters, CT values of intraarticular iodine and muscle, image contrast (iodine/muscle), and image quality (5-point scale: 1 = worst, 5 = best) were evaluated. Two independent readers assessed glenoid morphology and performed glenoid measurements on 2D and 3D images. Results Calculation of VNC images and VNC 3D reformats was successful in 42/42 shoulders (100%). The effective dose was mean 1.95 mSv (± 0.9 mSv). CT values of iodine and muscle were mean 1014.6 HU (± 235.8 HU) and 64.5 HU(± 8.6 HU), respectively, and image contrast was mean 950.2 HU (± 235.5 HU). Quality of cross-sectional images, VNC images, and VNC 3D reformats was rated good (median 4 (4–5), 4 (3–4), 4 (3–5), respectively). Detection of an osseous defect was equal on 2D and 3D images (13/42, P > 0.99) with no difference for measurement of the glenoid diameter with mean 28.3 mm (± 2.8 mm) vs. 28.4 mm (± 2.9 mm) (P = 0.5), width of the glenoid defect with 3.2 mm (± 2.1 mm) vs. 3.1 mm (± 2.3 mm) (P = 0.84), surface area with 638.5 mm2 (± 127 mm2) vs. 640.8 mm2 (± 129.5 mm2) (P = 0.47), and surface area of the defect with 46.6 mm2 (± 44.3 mm2) vs. 47.2 mm2 (± 48.0 mm2) (P = 0.73), respectively. Conclusion DECT shoulder arthrography is feasible and allows successful iodine removal with generation of VNC images and accurate VNC 3D reformats of the glenoid for assessment of bone loss.

BACKGROUND: To compare task-based image quality (TB-IQ) among virtual monoenergetic images (VMI) and linear-blended images (LBI) from dual-energy CT as a function of contrast task, radiation dose, size, and lesion diameter. METHODS: A TB-IQ phantom (Mercury Phantom 4.0, Sun Nuclear Corporation) was imaged on a third-generation dual-source dual-energy CT with 100/Sn150 kVp at three volume CT dose levels (5, 10, 15 mGy). Three size sections (diameters 16, 26, 36 cm) with subsections for image noise and spatial resolution analysis were used. High-contrast tasks (e.g., calcium-containing stone and vascular lesion) were emulated using bone and iodine inserts. A low-contrast task (e.g., low-contrast lesion or hematoma) was emulated using a polystyrene insert. VMI at 40–190 keV and LBI were reconstructed. Noise power spectrum (NPS) determined the noise magnitude and texture. Spatial resolution was assessed using the task-transfer function (TTF) of the three inserts. The detectability index (d’) served as TB-IQ metric. RESULTS: Noise magnitude increased with increasing phantom size, decreasing dose, and decreasing VMI-energy. Overall, noise magnitude was higher for VMI at 40–60 keV compared to LBI (range of noise increase, 3–124%). Blotchier noise texture was found for low and high VMIs (40–60 keV, 130–190 keV) compared to LBI. No difference in spatial resolution was observed for high contrast tasks. d’ increased with increasing dose level or lesion diameter and decreasing size. For high-contrast tasks, d’ was higher at 40–80 keV and lower at high VMIs. For the low-contrast task, d’ was higher for VMI at 70–90 keV and lower at 40–60 keV. CONCLUSIONS: Task-based image quality differed among VMI-energy and LBI dependent on the contrast task, dose level, phantom size, and lesion diameter. Image quality could be optimized by tailoring VMI-energy to the contrast task. Considering the clinical relevance of iodine, VMIs at 50–60 keV could be proposed as an alternative to LBI.

A 67-year-old male presented to the hospital for lower back pain and left lower extremity radiculopathy. Although the patient was afebrile and white blood cell count was normal, MRI was concerning for discitis/osteomyelitis at L4-L5. Subsequently, the patient developed a right knee joint effusion and underwent an arthrocentesis that was notable for the presence of urate crystals. A systemic urate crystal arthropathy was proposed as a potential etiology for the patient’s back pain and radiculopathy. Dual energy CT of the lumbar spine was performed, a technique which determines material composition by comparing the photon attenuation of the substance from two different x-ray energy levels. Results revealed the presence of monosodium urate crystals in the intervertebral discs. This technique is proposed as a noninvasive way to evaluate for gout in atypical locations or those difficult to sample and may replace an invasive intervertebral disc/endplate aspiration and/or biopsy. Dual energy CT should be considered in patients with elevated serum uric acid and concern for spinal involvement of gout.

Background: The urinary tract stone disease is a common problem. Dual energy CT with advanced post processing techniques gives anatomical information as size, site of the stone as well as its chemical composition which alter the clinical management. Objective: This study was aimed at studying the role of dual energy computed tomography in characterization of renal stones. Patients and methods: This study was carried out at the private radiology center throughout the period from January 2020 to January 2021 included 48 patients with renal stones. In this study, renal stones were more common in men (66.7 %) than in women (30.3%). The age of our selected patients ranged from 24 to 55 years with a mean of 42 years. The most affected age group was from 24-44 years (24 cases) represented 50% of the cases. Results: The average age of the studied group was (42.1±7.6), the most common presentation symptoms was loin pain (75.0%) followed by hematuria (18.8 %) then nausea& vomiting (4.2%) and fever (2.0%).Dual energy CT had 88.9% ability to truly detect uric from non-uric acid stones with (97.9%) accuracy, (100.0%) ability to exclude non uric stones (specificity), (100.0%) predictive value positive and (97.5%) predictive value negative with (50.0%) prevalence and (35.0%) likelihood positive ratio. Conclusion: It could be concluded that dual energy CT has been shown to be effective for characterizing chemical composition of the urinary stones, dual energy CT not well established enough to be used in clinical practice, but it will replace helical non contrast CT as the standard imaging modality for urinary calculi.

Background: Chronic rhinosinusitis is a common disease with a significant impact on the quality of life. Topical drug delivery to the paranasal sinuses is not efficient to prevent sinus surgery or expensive biologic treatment in a lot of cases as the affected mucosa is not reached. More efficient approaches for topical drug delivery are, therefore, necessary. In the current study, dual-energy CT (DECT) imaging was used to examine sinus ventilation before and after sinus surgery using a pulsating xenon gas ventilator in a cadaver head. Methods: Xenon gas was administered to the nasal cavity of a cadaver head with a laminar flow of 7 L/min and with pulsating xenon-flow (45 Hz frequency, 25 mbar amplitude). Nasal cavity and paranasal sinuses were imaged by DECT. This procedure was repeated after functional endoscopic sinus surgery (FESS). Based on the enhancement levels in the different sinuses, regional xenon concentrations were calculated. Results: Xenon-related enhancement could not be detected in most of the sinuses during laminar gas flow. By superimposing laminar flow with pulsation, DECT imaging revealed a xenon wash-in and wash-out in the sinuses. After FESS, xenon enhancement was immediately seen in all sinuses and reached higher concentrations than before surgery. Conclusion: Xenon-enhanced DECT can be used to visualize and quantify sinus ventilation. Pulsating air-/gas flow was superior to laminar flow for the administration of xenon to the paranasal sinuses. FESS leads to successful ventilation of all paranasal sinuses.