Dual-energy CT Scans Research Articles

Improved imaging of colorectal liver metastases using single-source, fast kVp-switching, dual-energy CT: preliminary results.

PurposeComputed tomography remains the first-choice modality for assessment of colorectal cancer liver metastases (CRLM). Dual-energy computed tomography (DECT) is a relatively new technique that is becoming increasingly available. One of the advantages of DECT is the ability to maximise iodine detection. Our aim was to test whether single-source, fast kVp-switching DECT can improve imaging quality of CRLM compared to conventional (polychromatic) CT.Material and methodsTwenty consecutive patients were enrolled into a preliminary prospective study. The scanning protocol consisted of four phases: non-contrast with standard 120 kV tube voltage and three post-contrast phases with rapid voltage switching. As a result, three sets of images were reconstructed: pre- and postcontrast polychromatic (PR), monochromatic (MR), and iodine concentration map (IM). To compare the sensitivity of the tested reconstructions, the number of CRLMs and the maximum diameter of the largest lesion were calculated. Objective image quality was measured as signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). The radiation dose was expressed as CTDIvol.ResultsImaging was successfully performed in all patients. The number of detected lesions was significantly lower on PR images than on IM and MR 50-70 keV (mean number: 4.20 and 4.45, respectively). IM and MR at 70 keV presented the highest quality. SNR was significantly higher for IM and 70 keV images than for other reconstructions. The mean radiation dose was 14.61 mGy for non-contrast 120 kV scan and 17.89 mGy for single DECT scan (p < 0.05).ConclusionsDECT is a promising tool for CRLM imaging. IM and low-photon energy MR present the highest differences in contrast between metastases and the normal liver parenchyma.

Energy-angle correlation correction algorithm for monochromatic computed tomography based on Thomson scattering X-ray source

The necessity for compact and relatively low cost x-ray sources with monochromaticity, continuous tunability of x-ray energy, high spatial coherence, straightforward polarization control, and high brightness has led to the rapid development of Thomson scattering x-ray sources. To meet the requirement of in-situ monochromatic computed tomography (CT) for large-scale and/or high-attenuation materials based on this type of x-ray source, there is an increasing demand for effective algorithms to correct the energy-angle correlation. In this paper, we take advantage of the parametrization of the x-ray attenuation coefficient to resolve this problem. The linear attenuation coefficient of a material can be decomposed into a linear combination of the energy-dependent photoelectric and Compton cross-sections in the keV energy regime without K-edge discontinuities, and the line integrals of the decomposition coefficients of the above two parts can be determined by performing two spectrally different measurements. After that, the line integral of the linear attenuation coefficient of an imaging object at a certain interested energy can be derived through the above parametrization formula, and monochromatic CT can be reconstructed at this energy using traditional reconstruction methods, e.g., filtered back projection or algebraic reconstruction technique. Not only can monochromatic CT be realized, but also the distributions of the effective atomic number and electron density of the imaging object can be retrieved at the expense of dual-energy CT scan. Simulation results validate our proposal and will be shown in this paper. Our results will further expand the scope of application for Thomson scattering x-ray sources.

Defectos de perfusión en el mapa de iodo pulmonar: causas y semiología

Objectiveto describe the usefulness of dual-energy CT for obtaining pulmonary perfusion maps to provide morphological and functional information in patients with pulmonary embolisms. To review the semiology of perfusion defects due to pulmonary embolism so they can be differentiated from perfusion defects due to other causes: alterations outside the range used in the iodine map caused by other diseases of the lung parenchyma or artifacts. ConclusionCT angiography of the pulmonary arteries is the technique of choice for the diagnosis of pulmonary embolisms. New dual-energy CT scanners are useful for detecting perfusion defects secondary to complete or partial obstruction of pulmonary arteries and is most useful for detecting pulmonary embolisms in subsegmental branches.

Experimental validation of two dual-energy CT methods for proton therapy using heterogeneous tissue samples.

The purpose of this work is to evaluate the performance of dual-energy CT (DECT) for determining proton stopping power ratios (SPRs) in an experimental environment and to demonstrate its potential advantages over conventional single-energy CT (SECT) in clinical conditions. Water equivalent range (WER) measurements of 12 tissue-equivalent plastic materials and 12 fresh animal tissue samples are performed in a 195MeV broad proton beam using the dose extinction method. SECT and DECT scans of the samples are performed with a dual-source CT scanner (Siemens SOMATOM Definition Flash). The methods of Schneider etal. (1996), Bourque etal. (2014), and Lalonde etal. (2017) are used to predict proton SPR on SECT and DECT images. From predicted SPR values, the WER of the proton beam through the sample is predicted for SECT and DECT using Monte Carlo simulations and compared to the measured WER. For homogeneous tissue-equivalent plastic materials, results with DECT are consistent with experimental measurements and show a systematic reduction of SPR uncertainty compared to SECT, with root-mean-square errors of 1.59% versus 0.61% for SECT and DECT, respectively. Measurements with heterogeneous animal samples show a clear reduction of the bias on range predictions in the presence of bones, with -0.88% for SECT versus -0.58% and -0.14% for both DECT methods. An uncertainty budgetallows isolating the effect of CT number conversion to SPR and predicts improvements by DECT over SECT consistently with theoretical predictions, with 0.34% and 0.31% for soft tissues and bones in the experimental setup compared to 0.34% and 1.14% with the theoretical method. The present work uses experimental measurements in a realistic clinical environment to show potential benefits of DECT for proton therapy treatment planning. Our results show clear improvements over SECT in tissue-equivalent plastic materials and animal tissues. Further work towards using Monte Carlo simulations for treatment planning with DECT data and a more detailed investigation of the uncertainties on I-value and limitations on the Bragg additivity rule could potentially further enhance the benefits of this imaging technology for proton therapy.

Non-contrast estimation of diffuse myocardial fibrosis with dual energy CT: A phantom study

BackgroundEstimation of diffuse myocardial fibrosis, substrate for adverse events such as heart failure and arrhythmias in patients with various cardiac disorders, is presently done by histopathology or cardiac magnetic resonance. We sought to develop a non-contrast method to estimate the amount of diffuse myocardial fibrosis leveraging dual energy computed tomography (DECT) in phantoms and a suitable small animal model. Methods and ResultsPhantoms consisted of homogenized bovine myocardium with varying amounts of Type 1 collagen. Fifteen mice underwent sham surgery, no procedure, or transverse aortic constriction (TAC) for 5 or 8 weeks to produce moderate or severe fibrosis, respectively. Phantoms and ex vivo mouse hearts were imaged on a single source, DECT scanner equipped with kVp switching. Monochromatic images were reconstructed at 40–140 keV. Linear discriminant analysis (LDA) was performed on mean myocardial CT numbers derived from single energy (70 keV) images as well as images reconstructed across multiple energies. Classification of myocardial fibrosis severity as low, moderate or severe was more often correct using the multi-energy CT/LDA approach vs. single energy CT/LDA in both phantoms (80.0% vs. 70.0%) and mice (93.3% vs. 33.3%). ConclusionsDECT myocardial imaging with multi-energy analysis better classifies myocardial fibrosis severity compared to a single energy-based approach. Non-contrast DECT can accurately and non-invasively estimate the extent of diffuse myocardial fibrosis in phantom and animal models. These data support further evaluation of this approach for in vivo myocardial fibrosis estimation.

Dual Energy Computed Tomography in Musculoskeletal Imaging, with Focus on Fragility Fractures of the Pelvis.

Dual energy computed tomography (DECT) is a constantly evolving technology, which opens up new diagnostic possibilities. It is particularly valuable for musculoskeletal (MSK) imaging. Due to the lack of recognition and availability of dual energy scanners, routine use is only established in a few centres. The intention of this review is to show the possibilities and fields of applications of the DECT in MSK imaging, as well as to describe technical principles and typical indications. We mainly focus on the use of DECT in the context of fragility fractures of the pelvis. The use of the DECT in pelvic fractures of the elderly could combine the advantages of CT diagnostics - fast and continuous availability, lower costs by dispensing with a supplementary MRI examination - and the high sensitivity of MRI to oedema in fragility fractures. Furthermore, the latest DECT scanners are dose neutral, so that these examinations can also be carried out without increased radiation exposure.

Analysis of pulmonary pure ground-glass nodule in enhanced dual energy CT imaging for predicting invasive adenocarcinoma: comparing with conventional thin-section CT imaging.

To investigate the value of dual energy computed tomography (DECT) parameters (including iodine concentration and monochromatic CT numbers) for predicting pure ground-glass nodules (pGGNs) of invasive adenocarcinoma (IA). A total of 55 resected pGGNs evaluated with both unenhanced thin-section CT (TSCT) and enhanced DECT scans were included. Correlations between histopathology [adenocarcinoma in situ (AIS), minimally IA (MIA), and IA] and CT scan characteristics were examined. CT scan and clinicodemographic data were investigated by univariate and multivariate analysis to identify features that helped distinguish IA from AIS or MIA. Both normalized iodine concentration (NIC) of IA and slope of spectral curve [slope(k)] were not significantly different between IA and AIS or MIA. Size, performance of pleural retraction and enhanced monochromatic CT attenuation values of 120-140 keV were significantly higher for IA. In multivariate regression analysis, size and enhanced monochromatic CT number of 140 keV were independent predictors for IA. Using the two parameters together, the diagnostic capacity of IA could be improved from 0.697 or 0.635 to 0.713. DECT could help demonstrate blood supply and indicate invasion extent of pGGNs, and monochromatic CT number of higher energy (especially 140 keV) would be better for diagnosing IA than lower energies. Together with size of pGGNs, the diagnostic capacity of IA could be better.

Can dual-energy CT replace perfusion CT for the functional evaluation of advanced hepatocellular carcinoma?

To determine the degree of relationship between iodine concentrations derived from dual-energy CT (DECT) and perfusion CT parameters in patients with advanced HCC under treatment. In this single-centre IRB approved study, 16 patients with advanced HCC treated with sorafenib or radioembolization who underwent concurrent dynamic perfusion CT and multiphase DECT using a single source, fast kV switching DECT scanner were included. Written informed consent was obtained for all patients. HCC late-arterial and portal iodine concentrations, blood flow (BF)-related and blood volume (BV)-related perfusion parameters maps were calculated. Mixed-effects models of the relationship between iodine concentrations and perfusion parameters were computed. An adjusted p value (Bonferroni method) < 0.05 was considered significant. Mean HCC late-arterial and portal iodine concentrations were 22.7±12.7 mg/mL and 18.7±8.3 mg/mL, respectively. Late-arterial iodine concentration was significantly related to BV (mixed-effects model F statistic (F)=28.52, p<0.0001), arterial BF (aBF, F=17.62, p<0.0001), hepatic perfusion index (F=28.24, p<0.0001), positive enhancement integral (PEI, F=66.75, p<0.0001) and mean slope of increase (F=32.96, p<0.0001), while portal-venous iodine concentration was mainly related to BV (F=29.68, p<0.0001) and PEI (F=66.75, p<0.0001). In advanced HCC lesions, DECT-derived late-arterial iodine concentration is strongly related to both aBF and BV, while portal iodine concentration mainly reflects BV, offering DECT the ability to evaluate both morphological and perfusion changes. • Late-arterial iodine concentration is highly related to arterial BF and BV. • Portal iodine concentration mainly reflects tumour blood volume. • Dual-energy CT offers significantly decreased radiation dose compared with perfusion CT.

Geochemical and petrophysical source rock characterization of the Vaca Muerta Formation, Argentina: Implications for unconventional petroleum resource estimations

The Vaca Muerta Formation is currently regarded as the most prolific source rock interval for unconventional petroleum exploration in Argentina. In this study, we integrate recent CT-scanner, nuclear magnetic resonance (NMR) T1-T2 and Rock-Eval Shale Play® analytical techniques, combined with classical geochemical, petrological and petrophysical methods to characterize Vaca Muerta source rocks along a vertical profile. The proposed analytical workflow was tested here on 4 samples derived from one core: the LJE-1010 borehole drilled in the lowermost Jurassic Vaca Muerta member (Neuquén Basin – Argentina), to evaluate the unconventional hydrocarbon potential and pore network attributes. First, entire rock samples were analyzed by dual energy CT scanner to evaluate possible heterogeneities; this also helped in the selection of representative samples. Then the organic matter properties were investigated by open-system pyrolysis techniques, organic petrography and biomarker analyses as a function of the core depth. A comparative approach between open-system pyrolysis methods (e.g. Rock-Eval Basic/Bulk-Rock & Shale Play® methods vs. Source Rock Analyzer) is also illustrated in this work. Finally, petrophysical characteristics and pore network attributes in shale were estimated by gas permeability (steady-state method corrected for Klinkenberg effect), porosity and NMR methods. The investigated samples have oil-window maturity and are characterized by a network of solid bitumen. Based on new Rock-Eval Shale Play® data, the potentially producible oil present in the rock samples was estimated using the modified oil saturation index (OSI=Sh0+Sh1 peaks×100/TOC). Results indicate that the oil crossover effect and potential productive oils occur within intervals showing higher TOC values (~3 to 8wt%). We also illustrated here that, for unconventional shale play perspectives, Rock-Eval Shale Play® parameters (Sh0 & Sh1) allow to obtain both a better quantification of free and retained hydrocarbons in source-reservoir rock samples and correct original oil in place (OOIP) estimations in early exploration campaign for shale oil and shale gas assessment. For Vaca Muerta rock samples, OOIP estimations range from 60 to 160bbl oil/acre-ft, approximately. We also demonstrated that the solid bitumen, oil and organic matter are clearly distinguished in the studied samples using advanced NMR T1-T2 maps obtained at different temperatures. The solid bitumen was clearly evidenced as a peak with T1/T2 ratio~14 on NMR T1-T2 maps. Concerning the matrix bulk rock permeability, the obtained results showed that the most deep sample is characterized by a permeability of about 140nanoDarcy (nD) whereas the shallower sample containing also higher amounts of organic matter is more permeable (~213nD), indicating that TOC values play a main control on Vaca Muerta poromechanical characteristics. The maximum total porosity values range between 6.5 and 21.8% and were calculated in this work integrating NMR and helium porosity values. Finally, global interpretations of these obtained results suggest that the Vaca Muerta Formation could be considered as a prolific shale play interval for unconventional petroleum exploration in the near future.

Radiation dose and image quality of computed tomography of the supra-aortic arteries: A comparison between single-source and dual-source CT Scanners

PurposeThe purpose of this work was to compare the image quality and radiation dose delivered to patients during computed tomography (CT) angiography (CTA) of the supra-aortic arteries using two single-source (SS) and two dual-energy (DE) CT scanners. Material and methodsIn this retrospective study, 120 patients who underwent CTA of supra-aortic arteries were studied using four different types of CT scanners: a sixteen and forty-detector-row SS and two DE CT scanners. Seventy milliters of contrast medium were injected at a flow rate of 4mL/s using a power injector. For each patient the dose-length product (DLP), the volume computed tomography dose index (CDTIvol), the length of the scan and the effective dose (ED) were calculated. Qualitative and quantitative [image noise, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR)] image quality assessment was performed. ResultsA statistically significant lower value of the DE compared to the SS technology (P<0.0001) for the CDTI, DLP and ED was found, whereas we did not find any statistically significant difference between the four scanners for the measurements of the image noise, SNR and CNR. ConclusionDS CT scanners allow performing CTAs with a reduced dose compared to SS CT scanner with comparable image quality.

Abstract ID: 187 Validation of dual energy CT atomic composition extraction using proton Monte Carlo

Proton Monte Carlo (MC) simulations model the physics processes between protons and medium and yield more accurate dose calculation compared to proton stopping power based pencil beam convolution algorithm. MC simulation is also essential for prompt gamma and proton-induced isotope production for in vivo proton range detection. It requires the tissue element composition to be determined from patient CT images. We propose a new hierarchical clustering based approach in extracting the atomic composition in human tissues from Dual Energy CT (DECT) scans and a method for validation using MC simulations. 70 published human tissues samples were used for the theoretical study of this approach. The tissues were first clustered by their composition similarities using hierarchical clustering. For each tissue cluster, three base tissues were randomly selected. Other tissues in this cluster were the weighted sum of these base tissues, where the weights were derived by fitting the attenuation coefficients calculated from DECT X-ray spectrums. The derived tissue atomic compositions and effective atomic number were compared with the ground truth. Animal tissues were scanned using a DECT scanner. The tissues were then irradiated using a PBS proton beam. A double Gaussian proton source has been modeled in GEANT4. Using these images, source model and extraction method, Monte Carlo simulations will be run mimicking the experimental setup. The soft tissues and bones were clustered into 8 subcategories, with cophenetic correlation 0.895 and inconsistency coefficient (IC) > 1.15 ( IC max = 1.1547 ). The mean and standard deviations of the difference in the derived atomic compositions and the ground truth for H, C, N, O, Ca, P were 0.05% (±0.07%), 1.56% (±2.02%), 0.61% (±0.55%), 1.81% (±2.37%), 0.03% (±0.07%), 0.13% (±0.16%), respectively. The Z eff from derived elemental composition was within 0.04 from the true values. We have investigated a new approach to extract the atomic composition from DECT scans. The accuracy of the extraction was demonstrated for published tissue samples. This approach will be validated using the DECT scans of animal tissues and GEANT4 source model, by comparing the Zeff derived from this method against measurements from proton beam irradiations.

31. Use of Dual Energy CT (DECT) scan to establish diagnosis of gout in dialysis dependent patient suspended from renal transplant list due to recurrent pyrexias of unknown origin

31. Use of Dual Energy CT (DECT) scan to establish diagnosis of gout in dialysis dependent patient suspended from renal transplant list due to recurrent pyrexias of unknown origin

Assessing lung function using contrast-enhanced dual-energy computed tomography for potential applications in radiation therapy.

There is an increasing interest in the evaluation of lung function from physiological images in radiation therapy treatment planning to reduce the extent of postradiation toxicities. The purpose of this work was to retrieve reliable functional information from contrast-enhanced dual-energy computed tomography (DECT) for new applications in radiation therapy. The functional information obtained by DECT is also compared with other methods using single-energy CT (SECT) and single-photon emission computed tomography (SPECT) with CT. The differential function between left and right lung, as well as between lobes is computed for all methods. Five lung cancer patients were retrospectively selected for this study; each underwent a SPECT/CT scan and a contrast-injected DECT scan, using 100 and 140 Sn kVp. The DECT images are postprocessed into iodine concentration maps, which are further used to determine the perfused blood volume. These maps are calculated in two steps: (a) a DECT stoichiometric calibration adapted to the presence of iodine and followed by (b) a two-material decomposition technique. The functional information from SECT is assumed proportional to the HU numbers from a mixed CT image. The functional data from SPECT/CT are considered proportional to the number of counts. A radiation oncologist segmented the entire lung volume into five lobes on both mixed CT images and low-dose CT images from SPECT/CT to allow a regional comparison. The differential function for each subvolume is computed relative to the entire lung volume. The differential function per lobe derived from SPECT/CT correlates strongly with DECT (Pearson's coefficient r = 0.91) and moderately with SECT (r = 0.46). The differential function for the left lung shows a mean difference of 7% between SPECT/CT and DECT; and 17% between SPECT/CT and SECT. The presence of nonfunctional areas, such as localized emphysema or a lung tumor, is reflected by an intensity drop in the iodine concentration maps. Functional dose volume histograms (fDVH) are also generated for two patients as a proof of concept. The extraction of iodine concentration maps from a contrast-enhanced DECT scan is achieved to compute the differential function for each lung subvolume and good agreement is found in respect to SPECT/CT. One promising avenue in radiation therapy is to include such functional information during treatment planning dose optimization to spare functional lung tissues.

Dual-energy bone removal computed tomography (BRCT): preliminary report of efficacy of acute intracranial hemorrhage detection.

One of the major applications of dual-energy computed tomography (DECT) is automated bone removal (BR). We hypothesized that the visualization of acute intracranial hemorrhage could be improved on BRCT by removing bone as it has the highest density tissue in the head. This preliminary study evaluated the efficacy of a DE BR algorithm for the head CT of trauma patients. Sixteen patients with acute intracranial hemorrhage within 1day after head trauma were enrolled in this study. All CT examinations were performed on a dual-source dual-energy CT scanner. BRCT images were generated using the Bone Removal Application. Simulated standard CT and BRCT images were visually reviewed in terms of detectability (presence or absence) of acute hemorrhagic lesions. DECT depicted 28 epidural/subdural hemorrhages, 17 contusional hemorrhages, and 7 subarachnoid hemorrhages. In detecting epidural/subdural hemorrhage, BRCT [28/28 (100%)] was significantly superior to simulated standard CT [17/28 (61%)] (p=.001). In detecting contusional hemorrhage, BRCT [17/17 (100%)] was also significantly superior to simulated standard CT [11/17 (65%)] (p=.0092). BRCT was superior to simulated standard CT in detecting acute intracranial hemorrhage. BRCT could improve the detection of small intracranial hemorrhages, particularly those adjacent to bone, by removing bone that can interfere with the visualization of small acute hemorrhage. In an emergency such as head trauma, BRCT can be used as support imaging in combination with simulated standard CT and bone scale CT, although BRCT cannot replace a simulated standard CT.

Detection of Myocardial Infarction Using Delayed Enhancement Dual-Energy CT in Stable Patients.

The objective of our study was to explore whether delayed enhancement dual-energy CT (DECT) allows the detection of myocardial infarcts in stable patients. Patients with known or suspected coronary artery disease clinically referred for myocardial perfusion imaging using SPECT were prospectively included. All patients (n = 34) also underwent stress, rest, and delayed enhancement DECT on a DECT scanner. At SPECT, segments with myocardial infarction (MI) were defined as those with a summed rest score of ≥ 2 in two or more consecutive segments, and a diagnosis of MI was supported by wall motion abnormalities, clinical history, and ECG findings. Segments with MI were identified in 13 (38%), 15 (44%), and 14 (41%) patients using SPECT, perfusion CT, and delayed enhancement DECT, respectively. When combined SPECT and perfusion CT results were used as the reference standard, delayed enhancement DECT had a sensitivity, specificity, positive predictive value, and negative predictive value for the detection of MI of 91.7% (95% CI, 62-98%), 86.4% (95% CI, 65-97%), 78.6% (95% CI, 49-95%), and 95.0% (95% CI, 75-100%). At delayed enhancement DECT (40 keV), a signal attenuation higher than 161 HU had a sensitivity of 72% and a specificity of 79% for the detection of MI on a per-segment basis. The median signal attenuation of myocardial infarcts at 40 keV was 3.0 SDs (interquartile range, 1.3-4.0 SDs) above that of normal myocardium. In this study, delayed enhancement DECT allowed the detection of myocardial infarcts in stable patients.

Dual-energy computed tomography has limited diagnostic sensitivity for short-term gout

The aim of this study was to discuss the diagnostic value of dual-energy computed tomography (DECT) in patients with gout during different disease phases. Two hundred twenty-one patients (136 with gout and 85 with other arthritic diseases) were recruited to the study. Arthrosis pain was evaluated in all patients by DECT scans. We calculated the sensitivity and specificity of DECT for the diagnosis of gout, including the first onset period, less than 24 months period, and more than 24 months period. We then investigated the related risk factors of urate crystals volume in the foot. The diagnostic sensitivity of DECT in the first onset, less than 24 months, and more than 24 months groups was 35.71, 61.54, and 92.86%, respectively. The overall sensitivity and specificity values were 80.88 and 88.24%, respectively. The multilinear regression analysis showed that longer disease duration (P = 0.001) and higher serum uric acid (SUA) (P = 0.001) were the two important predictive factors of the monosodium urate (MSU) crystal volume in the foot. DECT provides good diagnostic accuracy for detection of MSU crystal deposits in gout patients. However, DECT has limited diagnostic sensitivity for short-term gout patients, especially for the first onset patients. Longer disease duration and higher SUA were predictive factors of MSU crystal volume.

Dual Energy CT Scanning in Evaluation of the Urinary Tract

This review will provide a comprehensive overview of the current techniques and possibilities for DECT in genito-urinary imaging. Datasets obtained with each DE acquisition carry different information, both qualitatively and quantitatively. Qualitative improvement of images results in a better contrast resolution and noise reduction, whereas the iodine amount in tissues can be quantified and expressed in mg/mL yielding information on tissue vascularization. Despite the concern on radiation dose exposure, DECT obviates the need of unenhanced standard scanning phase and with the monochromatic images, a higher contrast-to-noise ratio is obtained reducing artifacts such as beam hardening and pseudo-enhancement. Furthermore, DECT allows composition characterization of renal stones and helps in differentiating adrenal adenomas from non-adenomas. Dual energy technology brought considerable innovation in the field of CT imaging since its first use. Genitourinary imaging represents one of the pivotal fields of application in which researchers have tested the performance of dual energy CT (DECT).

Dual-Energy Computed Tomography: Physical Principles, Approaches to Scanning, Usage, and Implementation: Part 2.

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.

Ultrasonography and dual-energy computed tomography provide different quantification of urate burden in gout: results from a cross-sectional study

BackgroundUltrasonography (US) and dual-energy computed tomography (DECT) can assess urate burden in gout. The objective of this study was to compare the quantification of urate deposition provided by US to the one provided by DECT.MethodsPatients with a diagnosis of gout were prospectively recruited to undergo quantification of urate deposition using US and DECT. US examination for tophi and the double contour (DC) sign was performed on the knees and feet and corresponding DECT scans provided volumes of tophi and of overall urate deposition. The primary endpoint was the intra-class correlation coefficient (ICC) of the volume of the index tophus measured by US and DECT and its 95% confidence interval (CI 95%).ResultsOf the 64 patients included, 34 presented with at least one tophus on US. DECT inter-reader agreement for urate deposition was perfect with an ICC of 1 (1–1) and good for the measurement of the index tophus with an ICC of 0.69 (0.47–0.83). The ICC for the measurement of the index tophus between the two techniques was poor with a value of 0.45 (0.1–0.71). The average ratio between the index tophi volume as assessed by DECT and US was 0.65. The number of DC-positive joints did not correlate with DECT volume of overall deposits (Spearman correlation coefficient of 0.23).ConclusionsDECT measurements of tophi give smaller volumes to the same tophi measured with US, and US signs of urate deposition in joints do not correlate with overall DECT volumes of extra-articular deposition.

Dual energy CT − a possible new method to assess regression of rectal cancers after neoadjuvant treatment

The measurement of tumor regression after neoadjuvant oncological treatment has gained increasing interest because it has a prognostic value and because it may influence the method of treatment in rectal cancer. The assessment of tumor regression remains difficult and inaccurate with existing methods. Dual Energy Computed Tomography (DECT) enables qualitative tissue differentiation by simultaneous scanning with different levels of energy. We aimed to assess the feasibility of DECT in quantifying tumor response to neoadjuvant therapy in loco-advanced rectal cancer. We enrolled 11 patients with histological and MRI verified loco-advanced rectal adenocarcinoma and followed up on them prospectively. All patients had one DECT scanning before neoadjuvant treatment and one 12 weeks after using the spectral imaging scan mode. DECT analyzing tools were used to determine the average quantitative parameters; effective-Z, water- and iodine-concentration, Dual Energy Index (DEI), and Dual Energy Ratio (DER). These parameters were compared to the regression in the resection specimen as measured by the pathologist. Changes in the quantitative parameters differed significantly after treatment in comparison with pre-treatment, and the results were different in patients with different CRT response rates. DECT might be helpful in the assessment of rectal cancer regression grade after neoadjuvant treatment.