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Purpose: In coronary computed tomographic angiography (CTA), low attenuation of coronary atherosclerotic plaque is associated with lipid-rich plaques. However, an overlap in Hounsfield units (HU) between fibrous and lipid-rich plaque as well as an influence of luminal enhancement on plaque attenuation was observed and may limit accurate detection of lipid-rich plaques by CTA. We sought to determine whether the quantitative histogram analysis improves accuracy of the detection of lipid-core plaque (LCP) in ex vivo hearts by validation against histological analysis., Materials and Methods: Human donor hearts were imaged with a 64-slice computed tomographic scanner using a standard coronary CTA protocol, optical coherence tomography (OCT), a histological analysis. Lipid-core plaque was defined in the histological analysis as any fibroatheroma with a lipid/necrotic core diameter of greater than 200 μm and a circumference greater than 60 degrees as well as a cap thickness of less than 450 μm. In OCT, lipid-rich plaque was determined as a signal-poor region with diffuse borders in 2 quadrants or more. In CTA, the boundaries of the noncalcified plaque were manually traced. The absolute and relative areas of low attenuation plaque based on pixels with less than 30, less than 60, and less than 90 HU were calculated using quantitative histogram analysis., Results: From 5 hearts, a total of 446 cross sections were coregistered between CTA and the histological analysis. Overall, 55 LCPs (12%) were identified by the histological analysis. In CTA, the absolute and relative areas of low attenuation plaque less than 30, less than 60, and less than 90 HU were 0.14 (0.31) mm2 (4.22% [9.02%]), 0.69 (0.95) mm2 (18.28% [21.22%]), and 1.35 (1.54) mm2 (35.65% [32.07%]), respectively. The low attenuation plaque area correlated significantly with histological lipid content (lipid/necrotic core size [in square millimeter] and a portion of lipid/necrotic core on the entire plaque) at all thresholds but was the strongest at less than 60 HU (r = 0.53 and r = 0.48 for the absolute and relative areas, respectively). Using a threshold of 1.0 mm2 or greater, the absolute plaque area of less than 60 HU in CTA yielded 69% sensitivity and 80% specificity to detect LCP, whereas sensitivity and specificity were 73% and 71% for using 25.0% or higher relative area less than 60 HU. The discriminatory ability of CTA for LCP was similar between the absolute and relative areas (the area under the curve, 0.744 versus 0.722; P = 0.37). Notably, the association of the low attenuation plaque area in CTA with LCP was not altered by the luminal enhancement for the relative (P = 0.48) but for the absolute measurement (P = 0.03). Similar results were achieved when validated against lipid-rich plaque by OCT in a subset of 285 cross sections., Conclusions: In ex vivo conditions, the relative area of coronary atherosclerotic plaque less than 60 HU in CTA as derived from quantitative histogram analysis has good accuracy to detect LCP as compared with a histological analysis independent of differences in luminal contrast enhancement.

Background: Coronary computed tomography angiography (CTA) enables accurate anatomic evaluation of coronary artery stenosis but lacks information about hemodynamic significance. The aim of this study was to evaluate 128-slice myocardial CT perfusion (CTP) imaging with adenosine stress using a high-pitch mode, in comparison with cardiac MRI (CMR)., Methods and Results: Thirty-nine patients with intermediate to high coronary risk profile underwent adenosine stress 128-slice dual source CTP (128×0.6 mm, 0.28 seconds). Among those, 30 patients (64 ± 10 years, 6% women) also underwent adenosine stress CMR (1.5T). The 2-step CTP protocol consisted of (1) adenosine stress-CTP using a high-pitch factor (3.4) ECG-synchronized spiral mode and (2) rest-CTP/coronary-CTA using either high-pitch (heart rate <63 bpm) or prospective ECG-triggering (heart rate >63 bpm). Results were compared with CMR and with invasive angiography in 25 patients. The performance of stress-CTP for detection of myocardial perfusion defects compared with CMR was sensitivity, 96%; specificity, 88%; positive predictive value (PPV), 93%; negative predictive value (NPV), 94% (per vessel); and sensitivity, 78%; specificity, 87%; PPV, 83%; NPV, 84% (per segment). The accuracy of stress-CTP for imaging of reversible ischemia compared with CMR was sensitivity, 95%; specificity, 96%; PPV, 95%; and NPV, 96% (per vessel). In 25 patients who underwent invasive angiography, the accuracy of CTA for detection of stenosis >70% was (per segment): sensitivity, 96%; specificity, 88%; PPV, 67%; and NPV, 98.9%. The accuracy improved from 84% to 95% after adding stress CTP to CTA. Radiation exposure of the entire stress/rest CT protocol was only 2.5 mSv., Conclusions: Adenosine-induced stress 128-slice dual-source high-pitch myocardial CTP allows for simultaneously assessment of reversible myocardial ischemia and coronary stenosis, with good diagnostic accuracy as compared with CMR and invasive angiography, at a very low radiation exposure.

Purpose: To evaluate the accuracy and added diagnostic value of 3-dimensional (3D) image fusion of computed tomography coronary angiography (CTCA) and functional cardiac magnetic resonance (CMR) for assessing hemodynamically relevant coronary artery disease (CAD)., Methods: Twenty-seven patients with significant coronary stenoses on prospectively electrocardiography-gated dual-source CTCA, confirmed by catheter angiography and perfusion defects on CMR at 1.5 T were included. Surface representations and volume-rendered images from 3D-fused CTCA/CMR data were generated using a software prototype. Fusion accuracy was evaluated by calculating surface distances of blood pools and Dice similarity coefficients. Two independent, blinded readers assigned myocardial defects to culprit coronary arteries with side-by side analysis of CTCA and CMR and using fused CTCA/CMR. Added value of fused CTCA/CMR was defined as change in assignment of culprit coronary artery to myocardial defect compared with side-by-side analysis., Results: 3D fusion of CTCA/CMR was feasible and accurate (surface distance of blood pools: 4.1 ± 1.3 mm, range: 2.4-7.1 mm; Dice similarity coefficients: 0.78 ± 0.08, range: 0.51-0.86) in all patients. Side-by-side analysis of CTCA and CMR allowed no assignment of a single culprit artery to a myocardial defect in 6 of 27 (22%) patients. Fused CTCA/CMR allowed further confinement of culprit coronary arteries in 3 of these 6 patients (11%). Myocardial defects were reassigned in 2 of 27 (7%) patients using fused CTCA/CMR, whereas the results remained unchanged in 22 of 27 (81%) patients. Interobserver agreement for assignment of culprit arteries to myocardial defects increased with fused CTCA/CMR (k = 0.66-0.89)., Conclusion: 3D fusion of low-dose CTCA and functional CMR is feasible and accurate, and adds, at a low radiation dose, diagnostic value for the assessment of hemodynamically relevant CAD as compared with side-by-side analysis alone. This technique can be clinically useful for the following: planning of surgical or interventional procedures in patients having a high prevalence of CAD and for improved topographic assignment of coronary stenoses to corresponding myocardial perfusion defects.

Objectives: To prospectively investigate whether the high-pitch mode (HPM) for computed tomography (CT) enables the diagnostic visualization of the lung parenchyma without suspended respiration., Materials and Methods: A total of 40 consecutive patients (age, 67 ± 11 years) underwent 128-slice dual-source CT of the chest including nonenhanced, arterial, and venous phase of contrast. CT was performed in the HPM with a pitch of 3.2 during continuous breathing (group A) and during breath-hold (group B), and at standard pitch of 1 during deep-inspiratory breath-hold (group C). The 3 protocols were scanned in a random order in each patient. Two blinded readers independently assessed the image quality of 5 regions in both the lungs using a semiquantitative 3-point score. Image noise was measured as the standard deviation of attenuation. Presence and size of pulmonary nodules were noted and measured on each CT dataset. Lung volume was measured using dedicated semi-automated segmentation software., Results: Interobserver agreement for image quality ratings was excellent (κ = 0.91). There were no significant differences in the number of lung regions having an image quality other than excellent between group A (2.5%) and B (1.5%, P = 0.48), whereas significantly less regions had impaired image quality in group B compared with group C (5.5%, P < 0.01). Image quality impairment in group C was because of breathing in 36% and cardiac pulsation in 64%. Image noise in group C (9 ± 2 HU) was significantly lower than that in group B (30 ± 2 HU, P < 0.001) whereas no significant difference was found between group A and B (P = 0.52). There were no significant differences for the depiction (P = 1.0) and size (P = 0.94) of lung nodules among the 3 modes. Average lung volume in group A was 75% ± 15% of that in deep inspiration (group B/C) being significantly smaller (P < 0.05). Estimated effective radiation doses in group C and group B were 5.8 ± 0.5 mSv and 1.6 ± 0.1 mSv, respectively., Conclusions: CT of the lung can be accomplished using the HPM at a low radiation dose with a diagnostic image quality even without suspended respiration.

Objectives: To prospectively evaluate a 3-dimensional spoiled gradient-dual-echo (3D SPGR-DE) magnetic resonance imaging (MRI) sequence for the qualitative and quantitative analysis of liver fat content (LFC) in patients with the suspicion of fatty liver disease using histopathology as the standard of reference., Materials and Methods: Thirty-four adult patients (15 women; mean age, 67 +/- 13 years) underwent hepatic 1.5-Tesla 3D SPGR-DE MRI including in-/out-of-phase (IP/OP) and fat-only sequences prior to hepatic surgery with biopsy. Histopathological analyses of total and macrovesicular LFC could be made from biopsies of 39 segments in 23 patients. Two radiologists independently classified steatosis visually using a 4-point scale for IP/OP and fat-only images. Additionally, fat signal fractions (FSF) were calculated from signal intensities on IP/OP (FSF(ip/op)) and fat-only images (FSF(fat-only)). Pearson correlation analysis and Student t test were used to study the relationship between the FSF and LFC as determined by histopathology. The accuracy of MRI in detecting pathologically elevated LFC was assessed by receiver operating characteristic analysis., Results: Histopathology revealed steatosis in 29/39 (74%) segments in 15/23 patients (65%), with a total LFC ranging from <5% to 90%. Inter-reader agreement for visual steatosis grading was moderate (k = 0.53) for IP/OP images and good (k = 0.68) for fat-only images. FSF calculated from IP/OP and fat-only images significantly correlated with LFC from histopathology (both, P < 0.0001). Mean FSF(fat-only) and FSF(ip/op) values significantly differed from total LFC (both, P < 0.0001), whereas mean FSF(fat-only) showed no significant differences to macrovesicular LFC (P = 0.46). Both FSF(fat-only) and FSF(ip/op) performed accurately in discriminating between normal LFC and elevated LFC according to histopathology with good diagnostic accuracy (AUC: 0.85; 95% CI: 0.73-0.89 vs. AUC 0.90, 95% CI: 0.7-1.00)., Conclusions: FSF(fat-only) and FSF(ip/op) derived from 3D SPGR-DE MRI mostly reflect the macrovesicular as opposed to the total LFC from histopathology, whereas both discriminate healthy and fatty liver. Analysis of fat-only images improves interreader-agreement for visual liver steatosis grading.

Purpose: To assess the feasibility and image quality of computed tomography (CT) liver perfusion imaging using an adaptive 4D spiral-mode, developed to extend the z-axis coverage, and to report initial qualitative and quantitative results in patients with cancer metastases., Materials and Methods: A total of 21 patients with liver metastases of various origins underwent CT perfusion imaging (100 kV and 150 mAs/rot) using a 4D spiral-mode with single-source 64-slice CT (n = 7) with a scan range of 6.7 cm (protocol A: 16 cycles, 46.5 seconds examination time), or dual-source 128-slice CT with a scan range of 14.8 cm (protocol B: 16 cycles, 46.5 seconds examination time, n = 7; protocol C: 12 cycles, 51.0 seconds examination time, n = 7). Ability to suspend respiration during perfusion imaging was monitored. Two independent readers assessed image quality on a 4-point scale, both before and after motion correction, and performed a qualitative (ie, arterial enhancement pattern and enhancement change over time) and quantitative perfusion (ie, arterial liver perfusion [ALP]; portal-venous perfusion [PVP]; hepatic perfusion index [HPI]) analysis., Results: Of 21 patients, 7 (33%) could suspend respiration throughout the perfusion study and 14 (67%) resumed shallow breathing during the perfusion scan. The 21 patients had a total of 88 metastases. The scan range of protocol A covered at least 1 metastasis in all patients (total 20/34 [58.8%] metastases). The scan range of protocol B and C covered 53 of 54 (98.1%) metastases, whereas one metastasis in segment VIII was only partially imaged. Image quality was diagnostic both before and after motion correction, whereas being significantly better after motion correction (P < 0.001). Qualitative perfusion analysis of 67 metastases revealed diffuse arterial enhancement in 3 (4.5%), sparse enhancement in 11 (16.4%), peripheral-nodular enhancement in 9 (13.4%), rim-like enhancement in 15 (22.4%), and none in 29 (43.3%) metastases. Enhancement over time of 67 metastases showed a centripetal progression in 6 (8.9%), sustained portal phase in 16 (23.9%), wash-out in 16 (23.9%), and none in 29 (43.3%) metastases. Quantitative perfusion analysis revealed significantly higher arterial liver perfusion and HPI in metastases and metastasis borders than in adjacent normal liver tissue (P < 0.001 each). Portal-venous perfusion was significantly lower in metastases and metastasis borders than in normal liver tissue (P < 0.001). There were no significant differences in image quality and qualitative perfusion analysis between the 3 protocols (P = n.s.). Calculated effective radiation doses were 13.4 mSv for protocol A, 30.7 mSv for protocol B, and 23.0 mSv for protocol C., Conclusion: CT perfusion imaging of the liver using the 4D spiral-mode is feasible with diagnostic image quality, and enables the reliable qualitative and quantitative analysis of the normal and metastatic liver parenchyma. Radiation dose issues must be considered when determining the scan range, number of cycles, and scan duration of the perfusion CT protocol.

Purpose: To assess image quality and capability of stone differentiation between UA-containing and non-UA-containing uroliths with the latest dual-energy (DE) computed tomography (CT) system equipped with a tin filter (TF) using various data acquisition parameters in a work bench model., Methods and Materials: One hundred ten urinary stones (4.2 +/- 3.0 mm, 0.4-12 mm) of 15 compositions were examined in an ex vivo phantom, using DE dual-source CT (Definition Flash, Siemens Healthcare) equipped with a TF. Phantom was scanned in a water tank and contained stones in acrylic elliptic spheres filled with a parenchyma substitute. Scans were performed at 3 different settings: at 80 and 140 kVp without TF, at 80 and 140 kVp with TF, and at 100 and 140 kVp with TF. Tube current time products were adapted to yield constancy in CT dose indices (CTDIvol = 18.84 mGy, 18.95 mGy, and 18.90 mGy, respectively). CT numbers of urinary stones and image noise were electronically measured by placing regions of interest. DE indices (DEI) were calculated and compared using analysis of variances for repeated measures and paired t tests; image noise (IN) using the Friedman test. The stones were classified as UA-containing or non-UA-containing on color-coded images based on the DEI. Diagnostic accuracy was calculated using crystallographic analysis as standard of reference., Results: Of the 110 stones (60%), 65 contained UA; 45 stones (40%) contained no UA. DEI was greatest at 80 and 140 kVp when using the TF (DEI80 kVp/TF140 kVp = 0.038 vs. DEI80 kVp/140 kVp = 0.028, DEI100 kVp/TF140 kVp = 0.025; P < 0.01). IN of high kVp acquisitions were similar (P = 0.15), whereas IN of low kVp acquisitions were significantly (P < 0.001) different being lowest at 100 kVp. The semiautomated DE software correctly classified all stones at all settings with a diagnostic accuracy of 100% (95% confidence interval: 97%-100%)., Conclusion: DECT with TF and 80-140 kVp tube voltage settings significantly improves the discrimination between UA-containing and non-UA containing urinary stones as compared with DECT without using the TF on the basis of DEI. The 100/140 kVp setting with TF is associated with lower IN but demonstrates similar discrimination abilities as compared with 80/140 kVp setting without the use of the TF.

Objective: To assess in severely obese patients the subjective and objective image quality parameters and to estimate the radiation dose of dual-source computed tomography coronary angiography (CTCA), using 3 different protocols., Materials and Methods: Dual-source CTCA was performed in 60 patients (30 women; mean age 58 +/- 7 years) suffering from obesity class II or higher (body mass index [BMI] >35 kg/sq m). Twenty patients were examined with a standard CTCA protocol at 120 kV/350 mAs (protocol A), 20 patients with a CTCA protocol at 140 kV/350 mAs (protocol B), and 20 patients at 140 kV/350 mAs with a dedicated obesity protocol (protocol C), that allows the additional data sampling by expanding the data acquisition for each tube from a quarter to a half rotation, permitting to trade off temporal resolution and image noise. Two blinded observers independently assessed the image quality of each coronary segment, using a 4-point scale (1: excellent-4: nondiagnostic) and measured the different image parameters (image noise, signal-to-noise ratio [SNR], and contrast-to-noise ratio [CNR]). Radiation dose estimates were calculated., Results: The average BMI was 46.3 +/- 8.3 kg/sq m (range, 36.8-69.6 kg/sq m). Subjective image quality (1.55 +/- 0.73) was significantly better in protocol C when compared with protocol A (2.46 +/- 0.76; P < 0.01) and protocol B (2.12 +/- 0.87; P < 0.017). There was a significantly lower rate of coronary artery segments with nondiagnostic image quality when using the obesity protocol C (1.5%; 4/262) compared with that obtained when using protocol A (7.8%; 22/280; P < 0.01) and protocol B (4.4%; 12/275; P < 0.017). Image noise was significantly lower in protocol C (31.8 +/- 5.0 HU) when compared with group A (43.5 +/- 4.7 HU; P < 0.001) and B (36.8 +/- 5.5 HU; P < 0.01). SNR and CNR were significantly higher in group C (13.8 +/- 2.4 and 23.1 +/- 2.8) compared with group A (10.6 +/- 1.7 and 15.1 +/- 3.2; each P < 0.001) and group B (12.0 +/- 2.0 and 18.8 +/- 3.1; each P < 0.01). The estimated effective radiation dose of the obesity protocol C (15.6 +/- 0.9 mSv) was significantly higher when compared with that in protocol A (10.1 +/- 0.8 mSv; P < 0.01), but not significantly different from that in protocol B (13.3 +/- 0.8 mSv; P = 0.022)., Conclusions: Use of an obesity protocol in dual-source CTCA in severely obese patients significantly improves image quality, but goes along with a higher radiation dose.

Objective: To assess prospectively, in healthy subjects and in patients with dilated cardiomyopathy (DCM) and hypertrophic obstructive cardiomyopathy (HOCM), the 3-dimensional (3D) shape, size, and motion of the mitral annulus (MA) using computed tomography (CT)., Materials and Methods: Twenty patients with no cardiac abnormalities (referred to as normals), 15 with DCM, and 15 with HOCM as determined by echocardiography underwent contrast-enhanced, retrospectively electrocardiography (ECG)-gated 64-slice CT of the heart. The MA was manually segmented in 10% steps of the RR interval with dedicated 3D software employing the point-wrap algorithm. The MA shape, area size, change of the MA area, and apicobasal MA motion throughout the cardiac cycle was determined and compared between the groups. Intercommissural distances were measured with CT and compared with findings during surgery in 9 patients undergoing ring annuloplasty., Results: The MA was nonplanar in all phases and subjects, being largest in diastole and smallest in systole. The MA area was significantly (P < 0.001) larger in patients with DCM (11.5 +/- 4.1 cm/m) as compared with normals (5.5 +/- 0.9 cm/m) and HOCM (4.7 +/- 0.9 cm/m). The change of MA area throughout the cardiac cycle was significantly (P < 0.017) smaller in patients with DCM (12.2 +/- 3.3%/m) as compared with normals (20.0 +/- 7.9%/m) and HOCM (20.5 +/- 7.7%/m). The mean apicobasal motion was significantly (P < 0.017) smaller in patients with DCM (2.2 +/- 1.0 mm/m) as compared with normals (3.6 +/- 0.8 mm/m) and HOCM (2.7 +/- 0.7 mm/m). Intercommissural distances as determined by CT showed a good correlation (r = 0.68, P < 0.05) with intraoperative measurements (mean difference, 0.44 mm; limits of agreement, -2.73-3.62 mm)., Conclusion: Our study provides in vivo human data on the 3D shape, size, and motion of the MA in healthy subjects. Significant changes in size and motion of the MA were noted in patients with HOCM.

Objective: To compare the image quality of mono- versus bisegment reconstruction algorithms for dual-source computed tomography coronary angiography (CTCA)., Materials and Methods: Eighty consecutive patients (27 women; average age, 60 +/- 12 years) were randomly assigned to 2 different CTCA scanning protocols: 40 patients (group A) underwent dual-source CTCA with a heart rate (HR)-dependent pitch adaptation with datasets reconstructed using the monosegment algorithm; 40 patients (group B) underwent CTCA at a fixed pitch of 0.2 and datasets were reconstructed using both mono- and bisegment algorithms. The temporal resolution was 82 milliseconds for mono- and 42 to 83 milliseconds (58 +/- 14 milliseconds) for bisegment reconstruction, the latter depending on the HR during CTCA. Images were reconstructed in the reconstruction phase having least motion artifacts in the individual patient, primarily during mid-diastole at 70% of the R-R interval. The HR variability was defined as the standard deviation from the average HR. Two blinded observers independently assessed the image quality of each coronary segment using a 4-point scale (1: excellent to 4: nonevaluable). Effective radiation dose estimates were calculated., Results: The overall image quality showed no significant differences between the 2 groups scanned with a fixed or a HR-adapted pitch (group A, score 1.21 +/- 0.63; group B, score 1.19 +/- 0.52). The overall image quality was superior when using monosegment (group A and B, score 1.21 +/- 0.63 and 1.19 +/- 0.52, respectively) when compared with the bisegment reconstruction algorithm (group B, score 1.33 +/- 0.72; P < 0.01). Image quality did not significantly correlate with average HR neither for monosegment (group A: r = 0.07; P = 0.35; group B: r = 0.06; P = 0.41) nor bisegment reconstructions (r = 0.07; P = 0.32). There was no significant correlation between image quality and HR variability using monosegment reconstructions (group A: r = 0.09; P = 0.22; group B: r = 0.05; P = 0.67), whereas a significant correlation was found for bisegment reconstructions (group B: r = 0.51; P < 0.01). The estimated effective radiation dose was significantly higher in group B (10.8 +/- 1.4 mSv) when compared with group A (9.0 +/- 0.8 mSv; P < 0.01)., Conclusions: Although providing a higher temporal resolution at certain HRs, the use of bisegment reconstructions for dual-source CTCA does not result in an improved overall image quality when compared with the monosegment reconstruction algorithm.

Objectives: We sought to determine the agreement for the quantification of cardiac chamber dimensions, volumes, and myocardial mass between dual-source computed tomography (DSCT) and echocardiography., Material and Methods: One-hundred patients underwent DSCT and transthoracal echocardiography within 1 week. Measurements of dimensions were obtained in standardized planes in end-systole and end-diastole and included the anterior-posterior diameter of the left atrium, septal and posterior wall thickness, and inner diameter of the left ventricle. Global left ventricular (LV) functional parameters [end-systolic volume (ESV), end-diastolic volume (EDV), ejection fraction, and LV myocardial mass (LVMM)] were computed using semiautomated software. ESV, EDV, and LVMM were normalized to the body-surface-area (BSA). Intraobserver and interobserver agreement of DSCT analysis was assessed. Correlation between DSCT and echocardiography was tested through linear regression and Bland-Altman analysis., Results: DSCT measurements had an excellent inter- and intraobserver agreement with close limits of agreement (R = 0.85-0.99, P < 0.001). All measurements obtained with DSCT showed a significant correlation with echocardiography, with close limits of agreement between modalities for all parameters. Significant differences of the mean difference from zero were only found for septal and posterior wall thickness (P < 0.001) (with a homogenous underestimation) and for EDV/BSA (P < 0.05) (showing an overestimation) in DSCT compared with echocardiography. No significant directional measurement bias was found for any parameter except for LVMM/BSA (R = 0.24, P < 0.05)., Conclusion: Our results indicate that DSCT provides reliable measurements of LV dimensions, volumes, and myocardial mass with similar values as compared with echocardiography.

Objectives: To assess the value of dual-energy contrast-enhanced computed tomography (CT) imaging for the detection of urinary stone disease using dual-source CT., Materials and Methods: Forty consecutive patients (mean age 46.6 +/- 16.2 years, range 27-85 years) suspected of having urinary stone disease underwent dual-source CT of the urinary tract. A 3-phasic CT scan protocol consisting of a standard unenhanced scan, a nephrographic, and an excretory phase of contrast enhancement was performed. The nephrographic phase scan was acquired in the dual-energy mode (80 kV/400 mA and 140 kV/95 mA) allowing reconstruction of virtual unenhanced images. Two blinded readers independently compared standard and virtual unenhanced CT for the number, size, and location of urinary stones. Measurements of anteroposterior abdominal diameters were performed to determine abdominal obesity., Results: Standard unenhanced CT revealed 35 uroliths in 18 of the 40 patients (18 of 40; 45%), virtual unenhanced CT demonstrated 26 uroliths in 15 of the 40 patients (15 of 40; 38%) ([kappa] value 0.89). Three false-negative and no false-positive ratings occurred using virtual unenhanced CT, and false-negative ratings solely occurred in obese patients. Sensitivity, specificity, positive predictive, and negative predictive values for virtual unenhanced CT for the diagnosis of urinary stone disease were 83%, 100%, 100%, and 88%, respectively., Conclusions: Virtual unenhanced CT images reconstructed from contrast-enhanced dual-energy CT allow detection of urinary stones with good sensitivity and excellent specificity, but sensitivity is decreased in abdominal obese patients.

Purpose: To evaluate reconstruction intervals and image quality in dual-source computed tomography (DSCT) coronary angiography for optimal placement of the ECG-pulsing window., Materials and Methods: DSCT coronary angiography was performed in 60 patients. Thirteen datasets were reconstructed in 5% increments from 20-80%. Two readers independently assessed image quality of each segment in each percentage-interval, using scores ranging from 1 (no motion artifacts) to 4 (nonevaluable)., Results: Mean heart rate (HR) was 69.0 +/- 18.9 beats per minute (bpm) (range, 35-117 bpm). Diagnostic image quality (scores 1-3) was found in 97.8% of all segments (763 of 780). The 70% RR-interval provided best image quality in all patients and all HRs. The narrowest reconstruction window providing diagnostic image quality was 60-70% for HR <60 bpm, 60-80% for 60-70 bpm, 55-80% for 70-80 bpm, and 30-80% for HR >80 bpm., Conclusions: DSCT coronary angiography provides best image quality for various HRs at 70%. The ECG-pulsing window can be adapted according to the HR while maintaining diagnostic image quality.