Dual-energy Index Research Articles

Is dual-energy computed tomography helpful to determinate the ferromagnetic property of bullets?

Abstract Background Gunshot injuries are frequent and may result in retained ballistic projectiles or fragments, this is why it is crucial to determinate the ferromagnetic property of retained projectiles if an MRI is considered. Purpose The goal of this ex vivo study was to determine if Dual-Energy Computed Tomography (DECT) can discriminate ferromagnetic bullets from non-ferromagnetic bullets. Material and Methods Twelve different bullets, placed in the center of the scanner on a gelatin phantom, underwent DECT evaluation. These projectiles were both ancient bullets from the 19Th century (eg. 8 mm 1890 ECP) and recent bullets from the late 20th century (eg. 9 mm Luger; 7.92 mm Mauser; 7 mm sport carabin). Two independent radiologists who were blinded to the properties of bullets performed all measurement on an external workstation with extended CT scale. Regions of interest (ROI) were placed in the core of each projectile. From these data, a dual-energy index (DEI) was calculated. A bootstrap method with a p value of less than 0.05 was used to demote statistical significance. Results Five bullets were ferromagnetic and seven were non-ferromagnetic. The DEI calculated were significantly (p 0.05) for intrareader and interreader agreement analysis. Conclusion DECT, found a difference between this ferromagnetic and non-ferromagnetic bullets samples using an extended HU, but because of several limitations in this study there is no cut-off DEI value to differentiate these two groups of bullets.

EXPERIENCE OF USING DUAL-ENERGY COMPUTED TOMOGRAPHY IN PATIENT WITH UROLITHIASIS

We presented a clinical case of dual-energy computed tomography in a patient with urolithiasis. Was performed a complex evaluation of the specific parameters obtained in dual-energy computed tomography: dual-energy ratio, dual-energy difference, dual-energy index, Z effective and the chemical composition of the urinary stone in a patient in vivo to determine the tactics of surgical treatment and metaphylaxis.

Ex vivo validation of a stoichiometric dual energy CT proton stopping power ratio calibration

A major source of uncertainty in proton therapy is the conversion of Hounsfield unit (HU) to proton stopping power ratio relative to water (SPR). In this study, we measured and quantified the accuracy of a stoichiometric dual energy CT (DECT) SPR calibration.We applied a stoichiometric DECT calibration method to derive the SPR using CT images acquired sequentially at and . The dual energy index was derived based on the HUs of the paired spectral images and used to calculate the effective atomic number (Zeff), relative electron density (), and SPRs of phantom and biological materials. Two methods were used to verify the derived SPRs. The first method measured the sample’s water equivalent thicknesses to deduce the SPRs using a multi-layer ion chamber (MLIC) device. The second method utilized Gafchromic EBT3 film to directly compare relative ranges between sample and water after proton pencil beam irradiation. Ex vivo validation was performed using five different types of frozen animal tissues with the MLIC and three types of fresh animal tissues using film. In addition, the residual ranges recorded on the film were used to compare with those from the treatment planning system using both DECT and SECT derived SPRs.Bland–Altman analysis indicates that the differences between DECT and SPR measurement of tissue surrogates, frozen and fresh animal tissues has a mean of 0.07% and standard deviation of 0.58% compared to 0.55% and 1.94% respectively for single energy CT (SECT) and SPR measurement.Our ex vivo study indicates that the stoichiometric DECT SPR calibration method has the potential to be more accurate than SECT calibration under ideal conditions although beam hardening effects and other image artifacts may increase this uncertainty.

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.

Dual-energy CT can detect malignant lymph nodes in rectal cancer

BackgroundThere is a need for an accurate and operator independent method to assess the lymph node status to provide the most optimal personalized treatment for rectal cancer patients.This study evaluates whether Dual Energy Computed Tomography (DECT) could contribute to the preoperative lymph node assessment, and compared it to Magnetic Resonance Imaging (MRI).The objective of this prospective observational feasibility study was to determine the clinical value of the DECT for the detection of metastases in the pelvic lymph nodes of rectal cancer patients and compare the findings to MRI and histopathology. Materials and methodsThe patients were referred to total mesorectal excision (TME) without any neoadjuvant oncological treatment. After surgery the rectum specimen was scanned, and lymph nodes were matched to the pathology report.Fifty-four histology proven rectal cancer patients received a pelvic DECT scan and a standard MRI.The Dual Energy CT quantitative parameters were analyzed: Water and Iodine concentration, Dual-Energy Ratio, Dual Energy Index, and Effective Z value, for the benign and malignant lymph node differentiation. ResultsDECT scanning showed statistical difference between malignant and benign lymph nodes in the measurements of iodine concentration, Dual-Energy Ratio, Dual Energy Index, and Effective Z value.Dual energy CT classified 42% of the cases correctly according to N-stage compared to 40% for MRI. ConclusionThis study showed statistical difference in several quantitative parameters between benign and malignant lymph nodes. There were no difference in the accuracy of lymph node staging between DECT and MRI.

Dual-Energy CT of Rectal Cancer Specimens: A CT-based Method for Mesorectal Lymph Node Characterization.

An accurate method to assess malignant lymph nodes in the mesorectum is needed. Dual-energy CT scans simultaneously with 2 levels of energy and thereby provides information about tissue composition based on the known effective Z value of different tissues. Each point investigated is represented by a certain effective Z value, which allows for information on its composition. We wanted to standardize a method for dual-energy scanning of rectal specimens to evaluate the sensitivity and specificity of benign versus malignant lymph node differentiation. Histopathological evaluation of the nodes was our reference. This was a descriptive and prospective study. Seventeen rectal specimens were examined in 2 series. The first series was conducted with 3 specimens from patients who were not given perioperative contrast; 3 had iodine-based contrast and 3 had gadolinium-based contrast. We concluded that iodine was the contrast agent of choice and therefore included 8 more patients in a second series, given iodine-based contrast, for further analysis. Quantitative imaging data were collected from 197 individual lymph nodes from 17 specimens, from patients with rectal cancer. We measured accuracy of differentiating benign from malignant lymph nodes by investigating the following: 1) gadolinium, iodine, and water concentrations in lymph nodes; 2) dual-energy ratio; 3) dual-energy index; and 4) effective Z value. Optimal discriminations between benign and malignant lymph nodes were obtained using the following cutoff values: 1) effective Z at 7.58 (sensitivity, 100%; specificity, 90%; and accuracy, 93%), 2) dual-energy ratio at 1.0 × 10 (sensitivity, 96%; specificity, 87%; and accuracy, 90%), 3) dual-energy index at 0.03 (sensitivity, 97%; specificity, 88%; and accuracy, 91%), and 4) iodine concentration at 2.58 μg/mL (sensitivity, 86%; specificity, 92%; and accuracy, 89%). The investigation is conducted on isolated surgical specimens from rectal cancer operations. Dual-energy CT can be performed on rectal specimens. The discrimination between benign and malignant nodes seems promising when using iodine as contrast.

TU-FG-BRB-01: Dual Energy CT Proton Stopping Power Ratio Calibration and Validation with Animal Tissues

Purpose: The conversion of Hounsfield Unit (HU) to proton stopping power ratio (SPR) is a main source of uncertainty in proton therapy. In this study, the SPRs of animal tissues were measured and compared with prediction from dual energy CT (DECT) and single energy CT (SECT) calibrations. Methods: A stoichiometric calibration method for DECT was applied to predict the SPR using CT images acquired at 80 kVp and 140 kVp. The dual energy index was derived based on the HUs of the paired spectral images and used to calculate the SPRs of the materials. Tissue surrogates with known chemical compositions were used for calibration, and animal tissues (pig brain, liver, kidney; veal shank, muscle) were used for validation. The materials were irradiated with proton pencil beams, and SPRs were deduced from the residual proton range measured using a multi-layer ion chamber device. In addition, Gafchromic EBT3 films were used to measure the distal dose profiles after irradiation through the tissue samples and compared with those calculated by the treatment planning system using both DECT and SECT predicted SPRs. Results: The differences in SPR between DECT prediction and measurement were −0.31±0.36% for bone, 0.47±0.42% for brain, 0.67±0.15% for liver, 0.51±0.52% for kidney, and −0.96±0.15% for muscle. The corresponding results using SECT were 3.1±0.12%, 1.90±0.45%, −0.66±0.11%, 2.33±0.21%, and −1.70±0.17%. In the film measurements, average distances between film and calculated distal dose profiles were 0.35±0.12 mm for DECT calibration and −1.22±0.12 mm for SECT calibration for a beam with a range of 15.79 cm. Conclusion: Our study indicates that DECT is superior to SECT for proton SPR prediction and has the potential to reduce the range uncertainty to less than 2%. DECT may permit the use of tighter distal and proximal range uncertainty margins for treatment, thereby increasing the precision of proton therapy.

Latest Advances in Musculoskeletal Dual Energy Computed Tomography (DECT)

Dual energy computed tomography (DECT) is a revolutionary imaging modality, which has shown great promise for new and improved diagnostic avenues—particularly in the realm of musculoskeletal imaging. The primary aim of this review will be to discuss these recent advances, while also providing insight regarding the recognition of artifacts inherent to DECT imaging itself. First we will discuss the ability of dual source DECT to scan one anatomic structure with two beams at different energy levels and compute a Dual Energy Index value. This allows for material decomposition and provides superior detection of urate and bone marrow edema when compared to conventional CT scan. Secondly, DECT provides alternative avenues for ligamentous characterization when modalities such as MRI are contraindicated. Lastly, extrapolation of dual energy data into virtual monoenergetic spectra levels allows for reduction of metal artifacts that can significantly degrade image quality on conventional CT imaging. As such, DECT is becoming a vital diagnostic tool for musculoskeletal and trauma radiologists globally.

Materials-based 3D segmentation of unknown objects from dual-energy computed tomography imagery in baggage security screening

We present a novel technique for the 3D segmentation of unknown objects from cluttered dual-energy Computed Tomography (CT) data obtained in the baggage security-screening domain. Initial materials-based coarse segmentations, generated using the Dual-Energy Index (DEI), are refined by partitioning at automatically detected regions. Partitioning is guided by a novel random forest based quality metric, trained to recognise high-quality, single-object segments. A second novel segmentation quality measure is presented for quantifying the quality of full segmentations based on the random forest metric of the constituent parts and the error in the number of objects segmented. In a comparative evaluation between the proposed approach and three state-of-the-art volumetric segmentation techniques designed for single-energy CT data (two region-growing [1,2] and one graph-based [3]) our method is shown to outperform both region-growing methods in terms of segmentation quality and speed. Although the graph-based approach generates more accurate partitions, it is characterised by high processing times and is significantly outperformed by the proposed method in this regard. The observations made in this study indicate that the proposed segmentation technique is well-suited to the baggage security-screening domain, where the demand for computational efficiency is paramount to maximise throughput.

Differentiation of heroin and cocaine using dual-energy CT—an experimental study

To evaluate if heroin and cocaine can be distinguished using dual-energy CT. Twenty samples of heroin and cocaine at different concentrations and standardized compression (SC) were scanned in dual-energy mode on a newest generation Dual Energy 64-row MDCT scanner. CT number, spectral graphs, and dual-energy index (DEI) were evaluated. Results were prospectively tested on six original samples from a body packer. Wilcoxon's test was used for statistical evaluation. Values are given as median and range. Under SC, the CT number of cocaine samples (-29.87 Hounsfield unit (HU) [-125.85; 16.16 HU]) was higher than the CT number of heroin samples (-184.37 HU [-199.81; -159.25 HU]; p < 0.01). Slope of spectral curves for cocaine was -2.36 HU/keV [-7.15; -0.67 HU/keV], and for heroin, 1.75 HU/keV [1.28; 2.5 HU/keV] (p < 0.01). DEI was 0.0352 [0.0081; 0.0528] for cocaine and significantly higher than for heroin samples (-0.0127 [-0.0097; -0.0159]; p < 0.001). While CT number was inconclusive, all six original packs were correctly classified after evaluation of the spectral curve and DEI. In contrast to the CT number, slope of the spectral curve and DEI were independent of concentration and compression. The slope of the spectral curve and the DEI from dual-energy CT data can be used to distinguish heroin and cocaine in vitro; these results are independent of compression and concentration in the measured range.

Low dose dual-energy computed tomography in suspected body packers and body stuffers—Preliminary clinical experience

Background The detectability of drug packages with abdominal plain film radiography is limited by sophisticated packaging methods and overlying stool, organs and bones. The aim of this study was to investigate the accuracy and practicability of dual-energy CT in body packers and stuffers, and the discernibility of cocaine from heroine. Materials and methods From May to December 2012 two suspected body packers and six suspected body stuffers (mean age of 30 years, range 20–43 years) were referred to our institution. A low dose native dual-energy CT of the abdomen and pelvis was performed in each case with tube currents of 14 mA s at 140 kV and 72 mA s at 80 kV. The data sets were reviewed for drug packages in a soft tissue and bone window as well as on color-encoded reformations of the dual energy index (DEI). Three-dimensional renderings of the DEI (cocaine material in green, heroine material in red) were produced to demonstrate findings to the police. Results In two body packers and three body stuffers an average of five drug packages were detected (range 1–11) with a mean size of 19 mm (range 9–39 mm). The mean attenuation of the packages was 151 HU (range 93–215 HU) at 80 kVp with an average decrease in attenuation of −92 HU (range −27 to −139 HU) at 140 kVp, suspicious of cocaine content in all cases. These results have been confirmed by chemical analysis of the defecated drug packages. The mean effective dose was 2.1 mSv (range 1.9–2.2 mSv), comparable to abdominal plain film radiographs with a typical effective dose of 1.3 mSv. Conclusion Dual-energy CT is a promising novel technique in detecting and characterizing drug packages in suspected body packers and stuffers. As most of these traffickers are of young age, the application of a low dose protocol is essential to limit the harm of ionizing irradiation.

Differentiation of cocaine from heroine body packs by computed tomography: Impact of different tube voltages and the dual-energy index

Abstract Objectives To investigate the computed tomography (CT) attenuation values and the dual-energy index (DEI) of cocaine and heroin at different tube voltage settings in a phantom study. Materials and methods Thirty-three hand-wrapped bodypacks prepared of heroin ( n =17) and cocaine ( n =16) at varying concentrations were submerged in a 28-cm water tank and imaged four times with a dual-source 64-detector row CT at peak tube voltage levels of 80kVp, 100kVp, 120kVp, and 140kVp. Tube current in each protocol was adjusted for a similar CT volume dose index of 8.0mGy. Image noise and the CT attenuation values were measured in each drug container three times at each tube voltage level by two independent observers, and the DEI was calculated from measurements at 80kVp and 140kVp. Results Image noise at the four tube voltage levels was similar ( p =0.32). Intra- and interobserver agreement was good ( r =0.89 to.93; p p r =−0.67; p r =−0.15; p =0.23). Conclusions CT attenuation values measured at low tube voltage level and using the DEI improve the differentiation of cocaine and heroin-containing bodypacks compared to measurements at higher tube voltage settings.

Informatics in Radiology: Dual-Energy Electronic Cleansing for Fecal-Tagging CT Colonography

Electronic cleansing (EC) is an emerging technique for the removal of tagged fecal materials at fecal-tagging computed tomographic (CT) colonography. However, existing EC methods may generate various types of artifacts that severely impair the quality of the cleansed CT colonographic images. Dual-energy fecal-tagging CT colonography is regarded as a next-generation imaging modality. EC that makes use of dual-energy fecal-tagging CT colonographic images promises to be effective in reducing cleansing artifacts by means of applying the material decomposition capability of dual-energy CT. The dual-energy index (DEI), which is calculated from the relative change in the attenuation values of a material at two different photon energies, is a reliable and effective indicator for differentiating tagged fecal materials from various types of tissues on fecal-tagging CT colonographic images. A DEI-based dual-energy EC scheme uses the DEI to help differentiate the colonic lumen-including the luminal air, tagged fecal materials, and air-tagging mixture-from the colonic soft-tissue structures, and then segments the entire colonic lumen for cleansing of the tagged fecal materials. As a result, dual-energy EC can help identify partial-volume effects in the air-tagging mixture and inhomogeneous tagging in residual fecal materials, the major causes of EC artifacts. This technique has the potential to significantly improve the quality of EC and promises to provide images of a cleansed colon that are free of the artifacts commonly observed with conventional single-energy EC methods.

Dual-Energy Index Value of Luminal Air in Fecal-Tagging Computed Tomography Colonography

The purpose of our study was to measure the dual-energy index (DEI) value of colonic luminal air in both phantom and clinical fecal-tagging dual-energy computed tomography (CT) colonography (DE-CTC) images and to demonstrate its impact on dual-energy electronic cleansing. For the phantom study, a custom-ordered colon phantom was scanned by a dual-energy CT scanner (SOMATON Definition Flash; Siemens Healthcare, Forchheim, Germany) at two photon energies: 80 and 140 kVp. Before imaging, the phantom was filled with a 300-mL mixture of simulated fecal materials tagged by a nonionic iodinated contrast agent at three contrast concentrations: 20, 40, and 60 mg/mL. Ten regions-of-interest (ROIs) were randomly placed in each of the colonic luminal air, abdominal fat, bony structure, and tagged material in each scan. For the clinical study, 22 DE-CTC (80 and 140 kVp) patient cases were collected, who underwent a low-fiber, low-residue diet bowel preparation and orally administered iodine-based fecal tagging. Twenty ROIs were randomly placed in each of the colonic luminal air, abdominal fat, abdominal soft tissue, and tagged fecal material in each scan. For each ROI, the mean CT values in both 80- and 140-kVp images were measured, and then its DEI was calculated. In the phantom study, the mean DEI values of luminal air were 0.270, 0.298, 0.386, and 0.402 for the four groups of tagging conditions: no tagged material and tagged with three groups of contrast concentrations at 20, 40, and 60 mg/mL. In the clinical study, the mean DEI values were 0.341, -0.012, -0.002, and 0.188 for colonic luminal air, abdominal fat, abdominal soft tissue, and tagged fecal material, respectively. In our study, we observed that the DEI values of colonic luminal air in DE-CTC images (>0.10) were substantially higher than the theoretical value of 0.0063. In addition, the observed DEI values of colonic luminal air were significantly higher than those of soft tissue. These findings have an important impact on electronic cleansing: it may provide an effective means of differentiating colonic soft-tissue structures from the air-tagging mixture caused by the partial volume effect and thus of minimizing the cleansing artifacts.

113 Dual energy ct improves differentiation of coronary atherosclerotic plaque components compared to conventional single energy CT

<h3>Introduction</h3> Vulnerable plaques have a relatively high necrotic core area and low fibrous tissue content. Although CT can identify plaque components on the basis of their x-ray attenuation, there is significant overlap between their attenuation ranges, most crucially between necrotic core and fibrous plaque. Recently introduced dual energy CT (DECT) permits acquisition of 2 different energy data sets simultaneously, with the change in attenuation of plaque components to different energies depending upon their material composition. We therefore examined whether DECT was better than single energy CT in determining plaque components defined by virtual histology IVUS. <h3>Methods</h3> 20 patients underwent DECT and 3-vessel VH-IVUS. CT data was obtained at peak voltages of 100 kV and 140 kV. 52 plaques were chosen with either homogenous fibrous plaque or confluent areas of calcified plaque or necrotic core as defined by VH-IVUS. VH-IVUS images were co-registered and orientated with the corresponding CT images using distance from coronary ostia and fiduciary markers (Abstract 113 figure 1). Multiple regions of interest (ROI) were placed within the plaque components or in lumen on cross sectional CT images pre-classified by VH-IVUS (Abstract 113 figure 1). ROI densities were measured (in Hounsfield Units) and assigned to the plaque component. A dual energy index (DEI) was created for each component, defined as the ratio of the difference in attenuation at 2 different energies / sum of attenuation with 1000 added to each attenuation value to avoid negatives. <h3>Results</h3> Attenuation values for 1088 ROIs were measured from 70 paired data sets at 100 kV and 140 kV creating 70 DEIs (12 necrotic core, 11 fibrous plaque, 29 calcified plaques and 18 lumen). Values obtained using a single energy data set showed good differentiation between calcified plaque and all others (p&lt;0.05), but considerable overlap between necrotic core and fibrous plaque (p=ns) (Abstract 113 figure 2A) (Abstract 113 table 1). In DECT, lumen (iodinated contrast) showed the greatest change in attenuation and hence had the highest DEI. Necrotic core had the lowest DEI and could be distinguished from all other components (p&lt;000.1) Importantly, in contrast to the single energy data, DEI derived from both energy data sets permitted resolution of necrotic core and fibrous plaque without overlap (Abstract 113 figure 2B). <h3>Conclusions</h3> The additional attenuation data provided by DECT improves the differentiation of plaque components when compared to conventional single energy CT. In particular, DECT may allow better differentiation of necrotic core and fibrous plaque, a weakness of conventional cardiac CT, allowing for more accurate non-invasive identification of vulnerable plaques.

Quantification of Liver Fat in the Presence of Iron and Iodine

Iodinated contrast media (CM) and iron in the liver are known to hinder an accurate quantification of liver fat content (LFC) with single-energy computed tomography (SECT). The purpose of this study was to evaluate the feasibility and accuracy of dual-energy CT (DECT) for ex vivo quantification of LFC, in the presence of iron and CM, compared with SECT. Sixteen phantoms with a defined LFC of 0%, 10%, 30%, and 50% fat and with varying iron content (0, 1.5, 3, and 6 mg/mL wet weight liver) were scanned with a second-generation dual-source 128-slice CT system. Phantoms were scanned unenhanced and contrast-enhanced after adding 1.0 mg/mL iodine to each phantom. Both SECT (120 kV) and DECT (tube A: 140 kV, using a tin filter 228 mAs; tube B: 80 kV, 421 mAs) data were acquired. An iron-specific dual-energy 3-material decomposition algorithm providing virtual noniron images (VNI) was used to subtract iron and CM from the data. CT numbers (Hounsfield units) were measured in all data sets, including 120 kV from SECT, as well as 140 kV, 80 kV, 50%:50% weighted 80 kV/140 kV, and VNI derived from DECT. The dual-energy index was calculated from 80 kV and 140 kV data. SECT and DECT measurements (Hounsfield units) including the dual-energy index of unenhanced and contrast-enhanced phantoms were compared with the known titrated LFC, using Pearson correlation analysis and Student t test for related samples. Inter-reader agreement was excellent for all measurements of CT numbers in both SECT and DECT data (Pearson r, 0.965-1.0). For fat quantification in the absence of iron and CM, CT numbers were similar in SECT and DECT (all, P > 0.05), showing a linear correlation with titrated LFC (r ranging from 0.981 to 0.999; P < 0.01). For fat quantification in the presence of iron but without CM, significant underestimation of LFC was observed for all measurements in SECT and DECT (P < 0.05), except for VNI. Measurements in VNI images allowed for an accurate LFC estimation, with no significant differences compared with measurements in iron-free phantoms (all, P > 0.25). For fat quantification in the presence of iron and CM, further underestimation of LFC was seen for measurements in SECT and DECT (P < 0.015), except for VNI. Measurements in VNI images showed a high accuracy for estimating the LFC, with no significant difference compared with measurements in iron- and CM-free phantoms (P > 0.2). Our ex vivo phantom study indicates that DECT with the use of a dedicated, iron-specific 3-material decomposition algorithm allows for the accurate quantification of LFC, even in the presence of iron and iodinated CM. VNI images reconstructed from DECT data equal nonenhanced SECT data of liver without CM by eliminating iron and iodine from the images. No added value was seen for DECT as compared with SECT for quantification of LFC in the absence of iron and iodine.

Dual-source dual-energy CT for the differentiation of urinary stone composition: preliminary study

Objective To evaluate dual-source dual-energy CT(DSCT) for the differentiation of urinary stone composition in vitro. Methods Ninety-seven urinary stones were obtained by endoscopic lithotripsy and scanned using dual-source dual-energy CT. The stones were divided into six groups according to infrared spectroscopy stone analysis: uric acid ( UA ) stones ( n = 10 ), cystine stones ( n = 5 ), struvite stones( n = 6), calcium oxalate ( CaOx ) stones ( n = 22 ), mixed UA stones ( n=7 ) and mixed calcium stones(n=47). Hounsfield units (HU) of each stone were recorded for the 80 kV and the 140 kV datasets by hand-drawing method. HU difference, HU ratio and dual energy index ( DEI ) were calculated and compared among the stone groups with one-way ANOVA. Using dual energy software to determine the composition of all stones, results were compared to infrared spectroscopy analysis. Results There were statistical differences in HU difference [(-17±13), (229±34),(309 ±45), (512 ±97), (201±64)and (530±71) HU respectively], in HU ratio (0.96±0.03, 1.34 ±0.04, 1.41 ±0.03, 1.47 ±0.03,1.30±0.07, and 1.49 ±0.03 respectively), and DEI( -0.006 ±0.004, 0.064 ±0.007, 0.080 ±0. 007, 0. 108±0.011 ,0. 055 ±0.014 and 0. 112 ±0.008 respectively ) among different stone groups(F=124. 894,407.028, 322. 864 respectively, P ＜0. 01 ). There were statistical differences in HU difference,HU ratio and DE1 between UA stones and the other groups( P ＜ 0. 01 ). There were statistical differences in HU difference, HU ratio and DEI between CaOx or mixed calcium stones and the other four groups (P＜0. 01 ). There was statistical difference in HU ratio between cystine and struvite stones ( P ＜ 0. 01 ). There were statistical differences in HU difference, HU ratio and DEI between struvite and mixed UA stones (P＜0. 05 ). Dual energy software correctly characterized 10 UA stones, 4 cystine stones, 22 CaOx stones and 6 mixed UA stones. Two struvite stones were considered to contain cystine. One cystine stone, 1 mixed UA stone, 4 struvite stones and 47 mixed calcium stones were considered to contain oxalate. Conclusions DSCT has the ability to differentiate urinary stone composition in vitro. With dual energy software, the UA, cystine and mixed UA stones can be differentiated from other types of stones. Key words: Urinary calculi; Tomography,X-ray computed

Potential of dual-energy computed tomography to characterize atherosclerotic plaque: ex vivo assessment of human coronary arteries in comparison to histology

Noninvasive characterization of coronary atherosclerotic plaque is limited with current computed tomography (CT) techniques. Dual-energy CT (DECT) has the potential to provide additional attenuation data for better differentiation of plaque components. We attempted to characterize coronary atherosclerotic plaque with DECT. Seven human coronary arteries acquired at autopsy were scanned consecutively at 80 and 140 kVp with CT. Vessels were perfused with saline, and data were acquired before and after contrast agent injection. Lesions were identified, and attenuation measurements were made from CT image quadrants. CT quadrants were classified as densely calcified, fibrocalcific, fibrous, lipid-rich, or normal vessel wall, corresponding to matched histology images. Attenuation values at each peak tube voltage were compared within plaque types for both noncontrast and contrast scans. Further, dual-energy index (DEI) values computed from attenuation were analyzed for classification of plaque. In 14 lesions, a total of 56 quadrants were identified. Histology results classified 8 (14%) as densely calcified, 8 (14%) as fibrocalcific, 9 (16%) as fibrous, 5 (9%) as lipid-rich, and 25 (45%) as normal vessel wall. Calcified lesions attenuated significantly more at 80 kVp in both contrast and noncontrast scans, whereas fibrous plaque attenuated more at 80 kVp only for contrast-enhanced scans. No differences were found for lipid-rich plaques. Using DEI values, only densely calcified plaques could be distinguished from other plaque types except fibrocalcific plaques in contrast images. Only densely calcified and fibrocalcific plaques showed a true change in attenuation at 80 versus 140 kVp. Therefore, calcified plaques could be distinguished from noncalcified plaques with DECT, but further classification of plaque types was not possible.