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Summary Systemic bile acid (BA) homeostasis is a critical determinant of dietary fat digestion, enterohepatic function, and postprandial thermogenesis. However, major checkpoints for the dynamics and the molecular regulation of BA homeostasis remain unknown. Here we show that hypothalamic-pituitary-adrenal (HPA) axis impairment in humans and liver-specific deficiency of the glucocorticoid receptor (GR) in mice disrupts the normal changes in systemic BA distribution during the fasted-to-fed transition. Fasted mice with hepatocyte-specific GR knockdown had smaller gallbladder BA content and were more susceptible to developing cholesterol gallstones when fed a cholesterol-rich diet. Hepatic GR deficiency impaired liver BA uptake/transport via lower expression of the major hepatocyte basolateral BA transporter, Na + -taurocholate transport protein (Ntcp/Slc10a1), which affected dietary fat absorption and brown adipose tissue activation. Our results demonstrate a role of the HPA axis in the endocrine regulation of BA homeostasis through the liver GR control of enterohepatic BA recycling.

Summary The aberrant accumulation of lipids in the liver ("fatty liver") is tightly associated with several components of the metabolic syndrome, including type 2 diabetes, coronary heart disease, and atherosclerosis. Here we show that the impaired hepatic expression of transcriptional cofactor transducin beta-like (TBL) 1 represents a common feature of mono- and multigenic fatty liver mouse models. Indeed, the liver-specific ablation of TBL1 gene expression in healthy mice promoted hypertriglyceridemia and hepatic steatosis under both normal and high-fat dietary conditions. TBL1 deficiency resulted in inhibition of fatty acid oxidation due to impaired functional cooperation with its heterodimerization partner TBL-related (TBLR) 1 and the nuclear receptor peroxisome proliferator-activated receptor (PPAR) α. As TBL1 expression levels were found to also inversely correlate with liver fat content in human patients, the lack of hepatic TBL1/TBLR1 cofactor activity may represent a molecular rationale for hepatic steatosis in subjects with obesity and the metabolic syndrome.

Purpose We sought to evaluate the feasibility and efficiency of dual energy (DE) bone and plaque removal in head and neck CT angiography. Materials and methods 20 patients with suspected carotid stenoses received head and neck DE-CTA as part of their pre-interventional workup. Visual grading using multiplanar reformations (MPR), thick slab maximum intensity projections (MIP) and quantitative vessel analysis (QVA) of stenoses was performed prior and after DE bone removal. Results were evaluated for the detection of relevant stenoses (vessel area reduction >70%). Vessel segmentation errors were analyzed. Results Segmentation errors occurred in 19% of all vessel segments. Nevertheless, most post-bone removal artifacts could be recognized using the MPR technique for reading. Compared to MPR reading prior to bone removal, sensitivity, specificity, positive and negative predictive values after bone removal were 100%, 98%, 88% and 100% for MPR reading and 100%, 91%, 63% and 100% for exclusive MIP reading, respectively. There was a good agreement between the QVA results prior and post-DE plaque removal (r2 = 0.8858). Conclusion DE bone and plaque removal for head and neck angiography is feasible and offers a rapid and highly sensitive overview over vascular head and neck studies. Due to a slightly limited specificity of the MIP technique due to segmentation errors, possible stenoses should be verified and graded using MPR techniques.

Rationale and Objectives The quantification of coronary calcification has established itself as a valid risk marker to predict cardiovascular events. However, data derived from cardiac multi–detector row computed tomography could demonstrate that the exclusion of coronary calcification is not synonymous with the exclusion of coronary artery disease (CAD). The aims of this retrospective analysis were to determine the prevalence of significant CAD in a symptomatic cohort with indications for invasive angiography but without coronary calcification (Agatston score 0) as assessed by multislice computed tomography and to investigate whether there were any differences in terms of risk factors between patients with and without significant CAD. Materials and Methods Five hundred multislice computed tomographic scans (in 371 men and 129 women) were included in the analysis. Agatston scores were determined on native scans. All patients underwent coronary angiography to detect or rule out obstructive CAD. Patients with negative calcium scoring were selected and divided into two subgroups: those without obstructive CAD and those with obstructive CAD (luminal stenoses > 50%). These subgroups were characterized in terms of clinical characteristics (age and sex) and cardiovascular risk factors (diabetes mellitus, hypertension, hyperlipoproteinemia, familial predisposition, smoking, and overweight). Results Sixty-one of 500 patients (12.2%) had negative calcium scores (Agatston score 0). Sixteen of these patients (26.3%, or 3.2% of the total population) had obstructive CAD according to invasive angiography. Patients with obstructive CAD were significantly older (mean age, 64 ± 9 vs 55 ± 10 years; P = .003) and were more frequently diabetic (25% vs 4%, P = .0389) than patients without obstructive CAD. There were no significant differences with regard to the other risk factors. Conclusions In this high-risk population, the absence of coronary calcification was not sufficient to rule out CAD. Among patients without coronary calcification, the presence of significant CAD was associated with increased age and the presence of diabetes mellitus.

Background Cardiac multi-detector computed tomography (MDCT) permits accurate visualization of high-grade coronary artery stenosis. However, in patients with heart rate irregularities, MDCT was found to have limitations. Thus, the aim of the present study was to evaluate the diagnostic accuracy of a new dual-source computed tomography (DSCT) scanner generation with 83 ms temporal resolution in patients without stable sinus rhythm. Methods 44 patients (31 men, mean age 67.5±9.2 years) without stable sinus rhythm and scheduled for invasive coronary angiography (ICA) because of suspected ( n =17) or known coronary artery disease (CAD, n =27) were included in this study. All patients were examined with DSCT (Somatom Definition ™ , Siemens). Besides assessment of total calcium score, all coronary segments were analyzed with regard to the presence of significant coronary artery lesions (>50%). The findings were compared to ICA in a blinded fashion. Results During CT examination, heart rhythm was as follows: 25 patients (57%) atrial fibrillation, 7 patients (16%) ventricular extrasystoles (two of them with atrial fibrillation), 4 patients (9%) supraventricular extrasystoles, 10 patients (23%) sinus arrhythmia (heart rate variability >10 bpm). Mean heart rate was 69±14 bpm, median 65 bpm. Mean Agatston score equivalent (ASE) was 762, ranging from 0 to 4949.7 ASE. Prevalence of CAD was 68% (30/44). 155 segments (27%) showed "step-ladder" artifacts and 28 segments (5%) could not be visualized by DSCT. Only 70 segments (12%) were completely imaged without any artifacts. Based on a coronary segment model, sensitivity was 73%, specificity 91%, positive predictive value 63%, and negative predictive value 94% for the detection of significant lesions (≥50% diameter stenosis). Overall accuracy was 88%. Conclusions In patients with heart rate irregularities, including patients with atrial fibrillation and a high prevalence of coronary artery disease, the diagnostic yield of dual-source computed tomography is still hampered due to a high number of segments with "step-ladder" artifacts.

Objectives In dual energy (DE) computed tomography (CT), spectral shaping by additional filtration of the high energy spectrum can theoretically improve dual energy contrast. The aim of this in vitro study was to examine the influence of an additional tin filter for the differentiation of human urinary calculi by dual energy CT. Materials and methods A total of 36 pure human urinary calculi (uric acid, cystine, calciumoxalate monohydrate, calciumoxalate dihydrate, carbonatapatite, brushite, average diameter 10.5 mm) were placed in a phantom and imaged with 2 dual source CT scanners. One scanner was equipped with an additional tin (Sn) filter. Different combinations of tube voltages (140/80 kV, 140/100 kV, Sn140/100 kV, Sn140/80 kV, with Sn140 referring to 140 kV with the tin filter) were applied. Tube currents were adapted to yield comparable dose indices. Low- and high energy images were reconstructed. The calculi were segmented semiautomatically in the datasets and DE ratios (attenuation@low_kV/attenuation@high_kV) and were calculated for each calculus. DE contrasts (DE-ratio_material1/DE-ratio_material2) were computed for uric acid, cystine and calcified calculi and compared between the combinations of tube voltages. Results Using exclusively DE ratios, all uric acid, cystine and calcified calculi (as a group) could be differentiated in all protocols; the calcified calculi could not be differentiated among each other in any examination protocol. The highest DE ratios and DE contrasts were measured for the Sn140/80 protocol (53%-62% higher DE contrast than in the 140/80 kV protocol without additional filtration). The DE ratios and DE contrasts of the 80/140 kV and 100/Sn140 kV protocols were comparable. Conclusion Uric acid, cystine and calcified calculi could be reliably differentiated by any of the protocols. A dose-neutral gain of DE contrast was found in the Sn-filter protocols, which might improve the differentiation of smaller calculi (Sn140/80 kV) and improve image quality and calculi differentiation in larger patients (Sn140/100 kV). However, even with the improved spectral separation of the Sn-filter protocols, the DE ratios of calcified calculi are not sufficiently distinct to allow a differentiation within this group.

Introduction In preliminary studies DSCT provides robust image quality over a wide range of heart rates and excludes CAD with high accuracy. The aim of the present study was to evaluate the reproducibility of these results in a large, unselected and consecutive group of patients scheduled for invasive coronary angiography (ICA). Material and methods 170 patients (124 men, 46 women; mean age: 64 ± 9 years) with known CAD (101 patients) or suspected CAD (69 patients) scheduled for ICA were examined by coronary CTA prior to ICA. All coronary segments were assessed for image quality (1: excellent; 5: non-diagnostic). The presence of significant vessel stenosis (>50%) was calculated using ICA as standard of reference. Results A total of 680 vessels were analyzed. Despite of 45 arrythmic patients all analyzed coronary segments were diagnostically evaluable. Mean Agatston score equivalent was 686 (range 0–4950). ICA revealed 364 lesions with ≥50% diameter stenosis. DSCT correctly identified 336 of these lesions. 115 lesions with a diameter stenosis ≤50% were overestimated by DSCT and thus considered as false-positive findings. On a per-segment basis, sensitivity was 92%, specificity 93%, positive predictive value (PPV) was 75% and negative predictive value (NPV) 98%. On a per-vessel basis DSCT revealed a sensitivity of 93%, a specificity of 88%, a PPV of 78% and a NPV of 97%. On a per-patient basis sensitivity was 94%, specificity 79%, PPV 88% and NPV 90%. Conclusions Initial results of preliminary studies showing robust image quality and high accuracy in DSCT cardiac imaging could be approved with the present study enclosing a large consecutive population. However severe coronary calcifications and irregular heart rate still remain limiting factors for coronary CTA. Despite improved image quality and high accuracy of coronary DSCT angiography, proof of indication is necessary, due to still remaining limiting factors.

Objective: To assess dose and image quality of dual-energy (DE) mixed images in comparison to single-energy (SE) images. Methods: A phantom containing iodine contrast inserts was scanned using SE and DE protocols. Dual-energy mixed images were reconstructed with varying composition ratios (ratio describing the contribution of 80 and 140 data in the mixed images). Image noise, iodine contrast, and contrast-to-noise ratios (CNRs) were assessed inside and outside the central field of view (FoV). Results: With the default composition ratio (0.3), noise and contrast were comparable between both protocols in the central FoV. Peripherally, DE image noise exceeded noise in SE images; CNR in the periphery was lower in the DE images. The highest CNR was found for a composition ratio of 0.5 to 0.9, exceeding the CNR of SE images. Conclusions: Dual-energy mixed images offer an image quality comparable to SE images within the central FoV at comparable dose levels. In the peripheral FoV, image quality is decreased. By optimizing the composition ratio in the DE mixed images, higher CNRs than in the SE images can be achieved, leading to a dose reduction potential.

Rationale and Objectives To prospectively evaluate the influence of the clinical pretest probability assessed by the Morise score onto image quality and diagnostic accuracy in coronary dual-source computed tomography angiography (DSCTA). Materials and Methods In 61 patients, DSCTA and invasive coronary angiography were performed. Subjective image quality and accuracy for stenosis detection (>50%) of DSCTA with invasive coronary angiography as gold standard were evaluated. The influence of pretest probability onto image quality and accuracy was assessed by logistic regression and chi-square testing. Correlations of image quality and accuracy with the Morise score were determined using linear regression. Results Thirty-eight patients were categorized into the high, 21 into the intermediate, and 2 into the low probability group. Accuracies for the detection of significant stenoses were 0.94, 0.97, and 1.00, respectively. Logistic regressions and chi-square tests showed statistically significant correlations between Morise score and image quality ( P P P = .0049 and P = .027). Linear regression revealed a cutoff Morise score for a good image quality of 16 and a cutoff for a barely diagnostic image quality beyond the upper Morise scale. Conclusion Pretest probability is a weak predictor of image quality and diagnostic accuracy in coronary DSCTA. A sufficient image quality for diagnostic images can be reached with all pretest probabilities. Therefore, coronary DSCTA might be suitable also for patients with a high pretest probability.

Non-invasive assessment of plaque volume and composition is important for risk stratification and long-term studies of plaque stabilisation. Our aim was to evaluate dual-source computed tomography (DSCT) and colour-coded analysis in the quantification and classification of coronary atheroma. DSCT and virtual histology intravascular ultrasound (IVUS-VH) were prospectively performed in 14 patients. 22 lesions were compared in terms of plaque volume, maximal per cent vessel stenosis and percentages of fatty, fibrous or calcified components. Plaque characterisation was performed with software that automatically segments luminal or outer vessel boundaries and uses CT attenuation for a colour-coded plaque analysis. Good correlation was found for per cent vessel stenosis in DSCT (53+/-13%) and IVUS (51+/-14%; r(2) = 0.70). Mean volumes for entire plaque and non-calcified atheroma were 68.5+/-33 mm(3) and 56.7+/-30 mm(3), respectively, in DSCT and 60.8+/-29 mm(3) and 55.8+/-26 mm(3), respectively, in IVUS. Mean percentages of fatty, fibrous or calcified components were 28.2+/-6%, 53.2+/-9% and 18.7+/-13%, respectively, in DSCT and 29.9+/-5%, 55.3+/-12% and 14.4+/-9%, respectively, in IVUS-VH. Significant overestimation was present for the entire plaque and the volume of calcified plaque (p = 0.03; p = 0.0004). Although good correlation with IVUS was obtained for the entire plaque (r(2) = 0.76) and non-calcified plaque volume (r(2) = 0.84), correlation proved very poor and insignificant for percentage plaque composition. Interclass correlation coefficients for non-calcified plaque volume and percentages of fatty, fibrous or calcified components were 0.99, 0.99, 0.95 and 0.98, respectively, and intraclass coefficients were 0.98, 0.93, 0.98 and 0.99, respectively. We found that using Hounsfield unit-based analysis, DSCT allows for accurate quantification of non-calcified plaque. Although percentage plaque composition proves highly reproducible, it is not correlated with IVUS-VH.

High coronary calcium scores are known to be associated with elevated all-cause mortality. Moreover, low response to clopidogrel influences cardiovascular outcome after coronary stent placement. We sought to evaluate whether elevated calcium scores measured by cardiac computed tomography are associated with a higher residual platelet aggregation (RPA) after treatment with clopidogrel. Thus, in 62 patients coronary calcium scoring was measured prior to stent implantation. RPA was assessed by ADP (20 micromol/L)-induced aggregometry at least 6 h after administration of a loading dose of 600 mg clopidogrel. We found a significant correlation between ASE and RPA (r2 = 0.135, p = 0.0033, slope 7.809 +/- 2.549). Patients within the first quartile of ASE had significantly lower RPA after administration of clopidogrel than other patients (p0.05). Establishing a threshold of 200 ASE responsiveness to clopidogrel could be predicted with a positive predictive value of 80% and a specificity of 91%. In conclusion, we could demonstrate that patients with a low coronary plaque burden are more likely to have low RPA. Coronary calcium scoring might help to identify low responders to clopidogrel prior to stent placement and aggregometry.

Ziel: Die Darstellbarkeit oropharyngealer Leitstrukturen ist durch Metallartefakte von Zahnimplantaten eingeschrankt. Ziel der Studie war der Vergleich der Bildqualitat von multiplanaren Rekonstruktionen (MPR) mit einer zusatzlichen angulierten Spirale in der Halsbildgebung mittels Dual-Source-CT. Material und Methoden: Bei 62 Patienten wurde eine Halsbildgebung mittels DSCT durchgefuhrt. MPRs des axialen Datensatzes sowie eine zusatzliche angulierte Spirale parallel zum Mundboden wurden akquiriert. Anschliesend wurden anatomische Leitstrukturen bezuglich ihrer Uberlagerung durch Metallartefakte anhand einer Visualskala von 1 (keine Artefakte) bis 4 (starke Artefakte) analysiert. Ergebnisse: Wahrend 87,1 % der anatomischen Strukturen in den MPRs starke Artefakte (3,12 ± 0,86) aufwiesen, zeigten die Leitstrukturen in der angulierten Spirale lediglich geringfugige Artefakte (1,28 ± 0,46). Der diagnostische Zugewinn durch die angulierte Spirale bezuglich des Schweregrads der Artefakte war signifikant (p < 0,01). Schlussfolgerung: MPRs sind nicht geeignet, um Zahnartefakte ausreichend zu reduzieren. Eine zusatzliche angulierte Spirale ist bei Patienten mit Zahnartefakten, die die anatomischen Leitstrukturen des Oropharynx uberlagern, empfehlenswert und sollte in der taglichen Routine eingesetzt werden. Als Folge des statischen Gantryaufbaus des DSCT ist der Einsatz einer flexiblen Kopfschale zur Akquisition einer angulierten Spirale notwendig. Purpose: Important oropharyngeal structures can be superimposed by metallic artifacts due to dental implants. The aim of this study was to compare the image quality of multiplanar reconstructions and an angulated spiral in dual-source computed tomography (DSCT) of the neck. Materials and Methods: Sixty-two patients were included for neck imaging with DSCT. MPRs from an axial dataset and an additional short spiral parallel to the mouth floor were acquired. Leading anatomical structures were then evaluated with respect to the extent to which they were affected by dental artifacts using a visual scale, ranging from 1 (least artifacts) to 4 (most artifacts). Results: In MPR, 87.1 % of anatomical structures had significant artifacts (3.12 ± 0.86), while in angulated slices leading anatomical structures of the oropharynx showed negligible artifacts (1.28 ± 0.46). The diagnostic growth due to primarily angulated slices concerning artifact severity was significant (p < 0.01). Conclusion: MPRs are not capable of reducing dental artifacts sufficiently. In patients with dental artifacts overlying the anatomical structures of the oropharynx, an additional short angulated spiral parallel to the floor of the mouth is recommended and should be applied for daily routine. As a result of the static gantry design of DSCT, the use of a flexible head holder is essential.

To assess HU-based color mapping for characterization of coronary plaque, using intravascular ultrasound virtual histology (IVUS-VH) as a standard of reference. Dual-source computed tomography and IVUS-VH were prospectively performed in 13 patients. In five lesions, HU thresholds of the color-coding software were calibrated to IVUS-VH. In a 15-lesion verification cohort, volumes of vessel, lumen and plaque or percentages of lipid, fibrous and calcified components were obtained through use of pre-set HU cut-offs as well as through purely visual adjustment of color maps. Calibrated HU ranges for fatty or fibrous plaque, lumen and calcification were -10-69, 70-158, 159-436 and 437+. Using these cut-offs, HU-based analysis achieved good agreement of plaque volume with IVUS (47.0 vs. 51.0 mm(3)). Visual segmentation led to significant overestimation of atheroma (61.6 vs. 51.0 mm(3); P = 0.04) Correlation coefficients for volumes of vessel, lumen and plaque were 0.92, 0.87 and 0.83 with HU-based analysis or 0.92, 0.85 and 0.71 with visual evaluation. With both methods, correlation of percentage plaque composition was poor or insignificant. HU-based plaque analysis showed good reproducibility with intra-class correlation coefficients being 0.90 for plaque volume and 0.81, 0.94 or 0.98 for percentages of fatty, fibrous or calcified components. With use of optimized HU thresholds, color mapping allows for accurate and reproducible quantification of coronary plaque.

Objective The aim of this study was to assess the impact of heart rate, heart rate variability and calcification on image quality and diagnostic accuracy in an unselected patient collective. Subjects and methods One hundred and two consecutive patients with known or suspected coronary artery disease underwent both 64-MSCT and invasive coronary angiography. Image quality (IQ) was assessed by independent observers using a 4-point scale from excellent (1) to non-diagnostic (4). Accuracy of MSCT regarding detection or exclusion of significant stenosis (>50%) was evaluated on a per segment basis in a modified AHA 13-segment model. Effects of heart rate, heart rate variability, calcification and body mass index (BMI) on IQ and accuracy were evaluated by multivariate regression. IQ and accuracy were further analysed in subgroups of significant predictor variables and simple regression performed to calculate thresholds for adequate IQ. Results Mean heart rate was 68.2 ± 13.3 bpm, mean heart rate variability 11.5 ± 16.0 beats per CT-examination (bpct) and median Agatston score 226.5. Average IQ score was 2 ± 0.6 whilst diagnostic quality was obtained in 89% of segments. Overall sensitivity, specificity, PPV or NPV was 91.2%, 99.2%, 95.3% or 98.3%. According to multivariate regression, overall IQ was significantly related to heart rate and calcification ( P = 0.0038; P P = 0.018); BMI was not related to IQ ( P = 0.52). Calcification was the only predictor variable with significant effect on the number of non-diagnostic segments ( P In a multivariate regression, calcification was also the single factor with impact on diagnostic accuracy ( P = 0.0049). Conclusion Whilst heart rate, heart rate variability and calcification all show an inverse correlation to IQ, severe calcium burden remains the single factor with translation of such effect into decrease of diagnostic accuracy.

Aims Detecting stenoses of coronary arteries with multidetector row computer tomography (MDCT) is a well feasible non-invasive method. However, there is still the problem of deciding whether a stenosis is hemodynamically relevant or not. Objective of the present study was to validate the feasibility of a low dose protocol for MDCT using 80 kV for detecting late enhancement. Methods and results Using a Alderson-Rando Phantom evaluation of the effective dose of this LE protocol was performed. Ten patients (six male, four female, mean age 61) with known coronary artery disease and scheduled for a conventional coronary angiogram in our facility were subsequently recruited. All patients underwent CT-angiography (CTA) 1 day prior to magnetic resonance imaging. Five minutes after the application of 100 ml contrast agent for the CTA scan, a low dose late enhancement scan (80 kV, 400 mA s maximum, ECG pulsed scan, 64 mm × 0.6 mm collimation, 0.33 s tube rotation) was performed. Phantom dose measurements showed an effective dose for this protocol of 1.19 mSv (male) and 1.61 mSv (female). Fifty-six percent (5/9) of the patients showed a late enhancement on the MRI scan. Three transmural late enhancements and all four negative findings were correctly identified by CT. This represents a sensitivity of 78% (3/5), specificity of 100% (3/3), NPV of 100% (4/4) and a PPV of 97%. Conclusion We were able to show that the low dose protocol is feasible and, furthermore, preliminary results look promising.

The aim of the present study was to evaluate the diagnostic accuracy of a new dual-source computed tomographic scanner generation with 83-ms temporal resolution in cardiac imaging. Fifty-one unselected consecutive patients (mean age 64 +/- 10 years) scheduled for invasive coronary angiography because of suspected or known coronary artery disease (CAD) were examined with dual-source computed tomography (DSCT). All coronary segments were analyzed regarding the presence of coronary artery lesions. The findings were compared with invasive coronary angiography. During computed tomographic examination, mean heart rate was 65 +/- 14 beats/min. Thirteen of 51 patients (25%) did not have sinus rhythm. Mean Agatston score equivalent was 779 (median 358, range 0 to 3,898). Prevalence of CAD was 75%. Based on a coronary segment model, sensitivity was 96%, specificity 87%, positive predictive value 61%, and negative predictive value 99% for the detection of significant lesions (or =50% diameter stenosis). The main reason for false-positive results was an overestimation of mild lesions by DSCT. In conclusion, our initial data indicate that DSCT allows a high accuracy to exclude relevant coronary stenosis in unselected patients with a high prevalence of CAD and a relevant number with heart rhythm irregularities. However, overestimation of stenosis, especially in cases of calcifications, is still a limitation.

The purpose was to assess 64-slice CT in the analysis of global and regional ventricular function, using a model of acute and subacute myocardial infarction in comparison with cine-MRI. Seven pigs underwent standard MSCT and MRI examination a median 1 and 21 days following creation of reperfused myocardial infarction. Endocardial and epicardial contours were manually defined and ventricular volumes calculated according to Simpson's method. Results were compared by Pearson's correlation coefficient and Blant-Altman analysis. Wall motion was assessed on cine-images and evaluated by kappa statistics. MSCT revealed a strong correlation with cine-MRI regarding quantification of end-diastolic volume (EDV; r = 0.97), end-systolic volume (ESV; r = 0.97), stroke volume (SV; r = 0.94), ejection fraction (EF; r = 0.95) or myocardial mass (MM; r =0.94 ). Minor overestimation was observed for EDV and ESV (bias -1.7 ml; -1.5 ml; P=0.095; 0.025), whilst the mean difference for EF was found to be negligible (bias 0.9%; P = 0.18). Both modalities showed a 96.2% segmental agreement in regional wall motion (weighted-kappa 0.91 for 238 segments). This was true for both acute and subacute infarct phase and MSCT, and thereby enabled accurate intraindividual follow-up of segmental dysfunction. Sixty-four-slice CT allows for reliable analysis of global cardiac function and, moreover, provides accurate evaluation of wall motion in acute and subacute myocardial infarct.

Objective The aim of this study was to assess the accuracy of MSCT in characterizing myocardial infarction (MI) and, thereby, determine the extent of early perfusion defect (ED), microvascular obstruction (MO) and transmural depth of late enhancement (LE) in comparison to MRI and histology. Materials and methods Seven pigs were studied with MSCT (Somatom Sensation 64) and MRI (Magnetom Sonata) a median 1 and 21 days following temporary occlusion of a diagonal branch and creation of small reperfused infarction. For depiction of ED, CT images were acquired in the early arterial phase and following 35 s; LE and MO were evaluated on images obtained at 3, 5, 10 and 15 min. Thereby, a bolus/low-flow contrast injection protocol was used. Triphenyltetrazolium-chloride (TTC) stain and histology were obtained. Volumes of enhancement patterns were assessed as percentage of the ventricle and compared by Bland–Altman analysis. Segmental co-localization and graded transmurality was evaluated with weighted-kappa-test. Results Close spatial agreement was observed for MRI–MO and MSCT–MO (bias = 0.55; CI = −1.49 to 2.60 at 5 min MSCT), TTC and MSCT–LE (bias = −1.28; CI = −3.76 to 1.19) or MRI–LE and MSCT–LE (bias = −0.79; CI = −4.19 to 2.60). There was good segmental co-localization for MO (weighted kappa = 0.93) and high agreement for transmural extent of TTC, MRI–LE and MSCT–LE (weighted kappa = 0.84 TTC versus MSCT; 0.86 MRI versus MSCT). Arterial and 35 s ED significantly underestimated infarct size and showed poor segmental or transmural agreement (weighted kappa = 0.33; 0.44). Conclusions MSCT late-scans not only reliably depict size of MO and LE in acute or subacute infarct phases but, moreover, allow for accurate determination of LE transmurality.

Multislice detector computed tomography (MSCT) is an accurate noninvasive modality to detect and classify different stages of atherosclerosis. The aim of the New Age II Study was to detect coronary lesions in men without established coronary artery disease (CAD) but with a distinct cardiovascular risk profile. We also sought to assess the effect after 1 year of a lipid-lowering therapy (LLT) using 20 mg of atorvastatin.Forty-sixe male patients (mean, 61 +/- 10 years) with an elevated risk for CAD (PROCAM score3 quintile) without LLT were included. Native and contrast-enhanced scans were performed in all patients. A total of 27 of 46 patients received a follow-up scan (after 488 +/- 138 days). Coronary plaque burden (CPB) was assessed volumetrically.The prevalence of CAD was 83% (38/46 patients), and 11% (5/46) without coronary calcifications still had noncalcified plaques. Total cholesterol and low-density lipoprotein cholesterol levels decreased significantly under LLT (225 +/- 41 mg/dL vs. 162 +/- 37 mg/dL, P0.0001 and 148 +/- 7 mg/dL vs. 88 +/- 5 mg/dL, P0.001, respectively). On follow-up, calcium score and CPB remained unchanged (Agatston score: 261 +/- 301 vs. 282 +/- 360; CPB: 0.149 +/- 0.108 vs. 0.128 +/- 0.075 mL, P0.05), whereas mean plaque volume of noncalcified plaques decreased significantly from 0.042 +/- 0.029 mL versus 0.030 +/- 0.014 mL (P0.05, mean reduction 0.012 +/- 0.017 mL or 24 +/- 13%).Statin therapy led to a significant reduction of noncalcified plaque burden that was not reflected in calcium scoring or total plaque burden. This finding might explain the risk reduction after the initiation of statin therapy. Using multislice detector computed tomography, physicians have the potential to monitor medical treatment in patients with coronary atherosclerosis.

The purpose of this study was to assess segment image quality at high heart rates using 16-slice computed tomography and differential reconstruction for major coronary vessels. According to the following protocol, 16-slice CT coronary angiography in 46 patients with a mean heart rate of 86.3+/-11.8 was reconstructed. At three transverse planes, preview series were obtained and motion artifacts evaluated in 5% increments from 0-95% within the cardiac cycle. Relying on image quality in the previews, reconstructions were performed at three z-positions for each patient. Segment image quality was assessed in terms of artifacts and visibility. The effects of heart rate and trigger delay on image quality were analyzed. Optimal image quality was achieved at 25 to 35% of the cardiac cycle for the left circumflex (CX) and right coronary artery (RCA) or 30 to 40% for the left main (LM) and left anterior descending artery (LAD). Sixteen-slice CT and differential reconstruction produced good image quality with a low percentage of motion-degraded proximal and middle segments (8.8%). Grades were 1.5 for the LM, 1.9 for the LAD, 2.0 for the CX and 2.3 for the RCA. At high heart rates, good image quality of the coronary arteries is achieved by 16-slice CT and a sophisticated reconstruction strategy at peak to late systole.

Objective To compare different image reconstruction parameters for detecting emboli of the pulmonary arteries according to anatomic levels using 16-slice multidetector-row computed tomography in patients suspected of having an acute pulmonary embolism (PE). Methods Sixty-two patients (33 male and 29 female) with a clinically suspected acute PE were included in the present study. Multidetector-row computed tomography scans were performed using 16-mmx0.75-mm collimation. Based on the computed tomography data set, different image reconstruction parameters were used for each patient: axial slice thicknesses (STs) of 0.75, 2, 4, and 6 mm; axial maximum intensity projection (MIP) STs of 4 mm; and coronal STs of 2 and 4 mm. In joint reading fashion, 2 experienced radiologists reviewed examination findings regarding the presence and/or absence of a PE. The reference standard for visualization and detection of PEs was defined using the axial images with a 0.75-mm ST. Results In 23 of 62 patients, a PE was diagnosed. For main and lobar pulmonary arteries, the sensitivities and specificities were as follows: axial 2-mm images, 1.0/1.0; axial 4-mm images, 1.0/1.0; axial 6-mm images, 0.97/0.99; MIP 4-mm images, 0.95/0.99; coronal 2-mm images, 1.0/1.0; and coronal 4-mm images, 1.0/1.0. Regarding segmental and subsegmental pulmonary arteries, sensitivity and specificity varied: axial 2-mm images, 0.97/1.0; axial 4-mm images, 0.81/0.99; axial 6-mm images, 0.65/0.99; axial MIP 4-mm images, 0.63/0.99; coronal 2-mm images, 0.91/0.99; and coronal 4-mm images, 0.74/0.99. Conclusions In detecting segmental and subsegmental PEs, only the axial images with an ST of 2 mm proved to have results comparable with the axial 0.75-mm images. Therefore, thin-slice collimation and ST are mandatory for visualization of segmental and subsegmental PEs in patients suspected of having an acute PE.

Coronary artery disease (CAD) is the leading cause of morbidity and mortality in the Western world. Since the majority of all invasive diagnostic coronary angiography procedures are not followed by therapeutic interventions, interest is growing in noninvasive technologies to diagnose and visualize CAD. The most promising of these is multislice spiral computed tomography (MSCT), which can visualize human coronary arteries in vivo noninvasively. Since 1999, this technique has improved rapidly, offering faster gantry rotation times and smaller voxel sizes. The image quality has become significantly more stable and MSCT has become a robust imaging modality. Beginning with 4-slice scanners in 1999, the latest scanner generation employs 64 slices. The present article summarizes the technical principles, image protocols and possible clinical applications of the current 64-row scanners.

OBJECTIVES To determine the image quality and diagnostic accuracy of cardiac multislice spiral computed tomography (MSCT) in elderly patients (>65 years old) in comparison to younger patients, this retrospective analysis was performed. METHODS The catheter-controlled MSCT results from patients older than 65 years of age were compared with the results of younger patients in a cohort of 117 patients with regard to sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and image quality. Fifty-three patients were older than 65 years of age (group 1: 31 men, age range: 72.2 +/- 4.1 years, number of risk factors: 2.6 +/- 1.3, Agatston score: 866 +/- 1090) and 64 were younger (group 2: 45 men, age range: 57.4 +/- 6.1 years, number of risk factors: 2.6 +/- 1.0, Agatston score: 765 +/- 1013). All patients were examined by MSCT (Sensation 16 Speed 4 D; Siemens, Forchheim, Germany, with a gantry rotation time of 375 milliseconds) and invasive coronary angiography. The MSCT results were compared blinded with the results of the coronary angiography with regard to the presence or absence of significant stenosis (>50%) in a 13-segment model. Image quality was assessed on a qualitative scale between 1 (very good) and 5 (insufficient image quality) for each segment. RESULTS Sensitivity, specificity, PPV, and NPP were not different statistically in both groups (group 1: 0.80/0.96/0.89/0.93 and group 2: 0.89/0.98/0.93/0.97). Three patients (all

Multislice CT, with 16, 32 or 64 rows per image, can provide an image quality that has improved the noninvasive diagnosis of disorders such as atherosclerotic plaque or coronary anomalies. This review summarizes the main data available and, despite various remaining confounding factors to image quality, calls for guidelines. With the introduction of four-slice scanners in 1999, multislice CT (MSCT) technology became available for investigative examination of the heart. Since then, MSCT technology has undergone rapid technical progress; temporal and spatial resolutions have been especially improved. The improved diagnostic image quality has led to more possible uses of MSCT being defined. At present, issues such as visualization of coronary artery bypass grafts, detection of stenoses of native coronary arteries, description of coronary anomalies, and calcium scoring, can be investigated reasonably well. Other features, such as plaque imaging and visualization of intracoronary stents, need further evaluation. A large number of factors, however, such as heart rate, atrial fibrillation, breathing artefacts and severe calcification, still influence image quality and reduce validity. In this article we provide a summary of current fields of application of cardiac MSCT. The word 'indication' is consciously avoided because official guidelines for the use of MSCT in heart examination have not yet been issued. Hopefully, prospective multicenter trials will be performed soon, providing more data with which to establish guidelines for both cardiologist and radiologist.

Objective: To describe the multidetector computed tomography (CT) findings in 3 patients with atypical gallstone ileus. Methods: We retrospectively evaluated computed radiography and CT images from three cases of surgically proven gallstone ileus. Two radiologists evaluated by consensus all images for the presence of ectopic gallstone, small bowel obstruction. intrahepatic pneumobilia, cholecystic pneumobilia. One author recorded whether diagnosis of gallstone ileus was made prospectively on radiologic reports and correlated findings to pathology. Results: All cases of gallstone ileus were atypical in that one patient had porcelain gallbladder, one had recurrent pyogenic cholangitis, and one was only 35 years of age. Prospective clinical diagnosis of gallstone ileus was made in only 1 patient at computed radiography and all 3 patients at CT. Retrospectively, small bowel obstruction and cholecystic pneumobilia were identified retrospectively in all 3 patients at both computed radiography and MDC'T, and an ectopic gallstone, intrahepatic pneumobilia, and choledochoduodenal fistula was seen in 2, 1, and 0 patients at computed radiography and 3, 2, and 3 patients at CT respectively. Conclusion: Multidetector CT is an accurate means to diagnose gallstone ileus, even in patients with atypical features. In particular, multidetector CT is useful for identifying the ectopic gallstone at the transition point between dilated and decompressed bowel.

Summary Normally post-mitotic neurons that aberrantly re-enter the cell cycle without dividing account for a substantial fraction of the neurons that die in Alzheimer's disease (AD). We now report that this ectopic cell cycle re-entry (CCR) requires soluble amyloid-β (Aβ) and tau, the respective building blocks of the insoluble plaques and tangles that accumulate in AD brain. Exposure of cultured wild type (WT) neurons to Aβ oligomers caused CCR and activation of the non-receptor tyrosine kinase, fyn, the cAMP-regulated protein kinase A and calcium-calmodulin kinase II, which respectively phosphorylated tau on Y18, S409 and S416. In tau knockout (KO) neurons, Aβ oligomers activated all three kinases, but failed to induce CCR. Expression of WT, but not Y18F, S409A or S416A tau restored CCR in tau KO neurons. Tau-dependent CCR was also observed in vivo in an AD mouse model. CCR, a seminal step in AD pathogenesis, therefore requires signaling from Aβ through tau independently of their incorporation into plaques and tangles.

Via multidetector computed tomography (MDCT) with retrospective electrographic gating, we sought to evaluate whether plaque distribution differs between responders and low responders to clopidogrel treatment. Low response was defined as a post-treatment aggregation of 35% to 70%. In this observational study, we enrolled 62 patients (mean age, 64.8 ± 8.9 yr; 51 men). In addition to determining coronary calcium scores, we performed noninvasive coronary angiography with MDCT before stent implantation. Plaques were visually classified as calcified, mixed, or completely noncalcified. Mean density was measured. Residual platelet aggregation (RPA) was evaluated by aggregometry 6 hr after administration of a 600-mg loading dose of clopidogrel. Patients with an RPA of less than 35% were defined as responders.The median calcium score was 736 Agatston score equivalent (ASE) (range, 0-5,772) and mean platelet inhibition was 35% ± 19% (range, 0-70%). A total of 494 coronary plaques were detected (responders: calcified, 197; mixed, 47, noncalcified, 5; and low responders: calcified, 177; mixed, 65; noncalcified, 3). Responders (n = 35) had significantly lower ASEs and fewer mixed but more calcified plaques than did low responders. In mean plaque density (measured within the noncalcified part of the plaques), no statistically significant difference existed between the 2 patient groups. By use of MDCT, we showed that ASE and plaque distribution were associated with RPA after clopidogrel treatment. Patients with a low coronary plaque burden and a small proportion of mixed plaques were more likely to have low RPA after administration of clopidogrel.

This study assesses the global left ventricular function and volumes using dual-source computed tomography (DSCT) with improved temporal resolution (83 ms) by use of a semi-automatic software tool in comparison to invasive angiography (IVA). One hundred patients scheduled for invasive coronary angiography because of suspected or known coronary artery disease (80 men; 20 women, mean age 62 ± 10 years) were additionally examined by DSCT. Global left ventricular function (LVF), left ventricular end-diastolic volume (LVEDV), end-systolic volume (LVESV), and stroke volume (SV) were calculated by the use of semi-automatic post-processing software and results compared with those of IVA. Bland-Altman analysis revealed a good concordance between DSCT and IVA in terms of LVF: Pearson’s r 0.78, confidence interval [CI] 0.68–0.86, P < 0.0001, bias 7.1% ± 9.1%. The same was true for LVESV (Pearson’s r 0.78, CI 0.67–0.85, P < 0.0001, bias 15.0 ± 21.0 ml), whereas the agreement for LVEDV and SV was only moderate (LVEDV: Pearson’s r 0.59, CI 0.43–0.72, P < 0.0001, bias 13.0 ± 18.1 ml; SV: Pearson’s r 0.47, CI 0.28–0.62, P < 0.0001, bias −1.4 ± 28.4 ml). Semi-automatic evaluation of left ventricular parameters with DSCT revealed good correlation for LVF and LVESV, whereas LVEDV and SV showed only a moderate correlation. Moreover, LVF is systematically underestimated by DSCT.

Objective: The aim of our study was to assess the impact of body mass index (BMI) on image quality and diagnostic accuracy using dual-source computed tomography. Subjects and Methods: Dual-source computed tomography and invasive coronary angiography were performed in 125 consecutive patients. Coronary segments were assessed for both image quality (1: excellent; 4: poor) and presence of significant vessel stenosis (≥50%). Accuracy of lesion detection was calculated using invasive coronary angiography as the standard of reference. The impact of BMI on image quality and accuracy was assessed by multivariate regression and between subgroups of BMI. Results: Mean BMI in our study was 28.4 ± 4.1 kg/m 2 . In multivariate regression, BMI was proved to have a significant and independent impact on image quality (P = 0.009). Similarly, the latter was significantly degraded in a subgroup of patients with BMI ≥30 kg/m 2 (P < 0.05). Although the proportion of segments with diagnostic image quality was equal in all BMI subgroups, linear regression suggested 25 kg/m 2 as the cut-off until which excellent or good image quality can be achieved. Sensitivity, specificity, positive, and negative predictive values were 91.6%, 93%, 75.2%, and 97.9% on a per-segment and 100%, 77.5%, 90.4%, and 100% on a per-patient level. In both multivariate analysis and comparison of subgroups, there was no significant effect of BMI on the per-segment diagnostic accuracy. Conclusion: Although in an unselected population, obesity turns out to have an independent impact on image quality, there is no translation of this effect into a deterioration of diagnostic accuracy.

The aim of the study was to estimate radiation exposure of coronary calcium scoring and angiography using ECG-gated and ECG-triggered dual-source computed tomography.An Alderson Rando phantom equipped with thermoluminescent dosimeters was used for all dose measurements. Effective dose was calculated according to ICRP 103. Radiation exposure was performed on a dual-source computed tomography (DSCT) scanner with standard protocols for calcium scoring (DSCT-Ca) and coronary angiography (DSCTA) at different heart rates (40-100 beats/min). Furthermore, a scanning protocol with ECG-triggering as well as a standard chest CT scan were evaluated.Depending on gender, heart rate and ECG-pulsing, the effective dose of a complete cardiac DSCT (DSCT-Ca and DSCTA) scan varies from 10.2 to 32.6mSv. The effective radiation dose increased significantly with lower heart rates (p0.035). ECG-pulsing reduced the radiation exposure significantly in DSCTA (p0.001). Due to breast tissue in the primary scan range, females' doses showed an increase up to 69.9% compared to males in scan protocols without ECG-pulsing. Prospective ECG-triggered DSCTA resulted in estimated effective doses from 2.8mSv (males) to 4.1mSv (females).The ECG-pulsing technique has proven its effectiveness to reduce effective dose in coronary CT angiography and is recommended for all patients with regular heart rates. The patient's heart rate influences the radiation exposure with a significant decrease at higher heart rates. Due to its lower dose, ECG-triggered DSCTA should be implemented for special indications, i.e. for diagnosis of pathologies of the aortic root and the ascending aorta.

The efficiency and radiation dose of a low-dose dual-energy (DE) CT protocol for the evaluation of urinary calculus disease were evaluated. A low-dose dual-source DE-CT renal calculi protocol (140 kV, 46 mAs; 80 kV, 210 mAs) was derived from the single-energy (SE) CT protocol used in our institution for the detection of renal calculi (120 kV, 75 mAs). An Alderson-Rando phantom was equipped with thermoluminescence dosimeters and examined by CT with both protocols. The effective doses were calculated. Fifty-one patients with suspected or known urinary calculus disease underwent DE-CT. DE analysis was performed if calculi were detected using a dedicated software tool. Results were compared to chemical analysis after invasive calculus extraction. An effective dose of 3.43 mSv (male) and 5.30 mSv (female) was measured in the phantom for the DE protocol (vs. 3.17/4.57 mSv for the SE protocol). Urinary calculi were found in 34 patients; in 28 patients, calculi were removed and analyzed (23 patients with calcified calculi, three with uric acid calculi, one with 2,8-dihyxdroxyadenine-calculi, one patient with a mixed struvite calculus). DE analysis was able to distinguish between calcified and non-calcified calculi in all cases. In conclusion, dual-energy urinary calculus analysis is effective also with a low-dose protocol. The protocol tested in this study reliably identified calcified urinary calculi in vivo.

Multi-slice computed tomography (MSCT) is a non-invasive modality to visualize coronary arteries with an overall good image quality. Improved spatial and temporal resolution of 64-slice and dual-source computed tomography (DSCT) scanners are supposed to have a positive impact on diagnostic accuracy and image quality. However, quantitative parameters to compare image quality of 16-slice, 64-slice MSCT and DSCT are missing. A total of 256 CT examinations were evaluated (Siemens, Sensation 16: n = 90; Siemens Sensation 64: n = 91; Siemens Definition: n = 75). Mean Hounsfield units (HU) were measured in the cavum of the left ventricle (LV), the ascending aorta (Ao), the left ventricular myocardium (My) and the proximal part of the left main (LM), the left anterior descending artery (LAD), the right coronary artery (RCA) and the circumflex artery (CX). Moreover, the ratio of intraluminal attenuation (HU) to myocardial attenuation was assessed for all coronary arteries. Clinical data [body mass index (BMI), gender, heart rate] were accessible for all patients. Mean attenuation (CA) of the coronary arteries was significantly higher for DSCT in comparison to 64- and 16-slice MSCT within the RCA [347 +/- 13 vs. 254 +/- 14 (64-MSCT) vs. 233 +/- 11 (16-MSCT) HU], LM (362 +/- 11/275 +/- 12/262 +/- 9), LAD (332 +/- 17/248 +/- 19/219 +/- 14) and LCX (310 +/- 12/210 +/- 13/221 +/- 10, all p0.05), whereas there was no significant difference between DSCT and 64-MSCT for the LV, the Ao and My. Heart rate had a significant impact on CA ratio in 16-slice and 64-slice CT only (p0.05). BMI had no impact on the CA ratio in DSCT only (p0.001). Improved spatial and temporal resolution of dual-source CT is associated with better opacification of the coronary arteries and a better contrast with the myocardium, which is independent of heart rate. In comparison to MSCT, opacification of the coronary arteries at DSCT is not affected by BMI. The main advantage of DSCT lies with the heart rate independency, which might have a positive impact on the diagnostic accuracy.

To prospectively evaluate the effect of heart rate, heart rate variability, and calcification on dual-source computed tomography (CT) image quality and to prospectively assess diagnostic accuracy of dual-source CT for coronary artery stenosis, by using invasive coronary angiography as the reference standard.This study had local Ethics Committee approval; all patients gave informed consent. Patients who underwent bypass surgery were excluded; patients with coronary artery stent-grafts were included. One hundred patients (20 women, 80 men; mean age, 62 years +/- 10 [standard deviation]) known to have or suspected of having coronary artery disease underwent dual-source CT and invasive coronary angiography. Image quality was assessed. Accuracy of dual-source CT in depiction or exclusion of significant stenosis (or=50%) was evaluated on a per-segment and per-patient basis. Effects of heart rate, heart rate variability, and calcification on image quality and accuracy were analyzed by using multivariate regression and were analyzed between subgroups of predictor variables. Simple regression was performed to calculate thresholds for adequate image quality.Mean heart rate was 64.9 beats per minute +/- 13.2, mean variability was 23.6 beats per CT examination +/- 36.2, and mean Agatston score was 786.5 +/- 965.9. Diagnostic image quality was obtained in 90.2% of segments. Sensitivity, specificity, and positive and negative predictive values for the presence of significant stenosis were, respectively, 91.1%, 92.0%, 75.4%, and 97.5% by segment and 100%, 81.5%, 93.6%, and 100% by patient. Image quality was significantly related to heart rate variability (P = .015) and calcification (P.001); the number of nondiagnostic segments was significantly affected by calcification only. Calcification was the single factor with significant impact on diagnostic accuracy (P = .001).While dual-source CT resulted in heart-rate independent image quality, image quality remained prone to heart rate variability and calcification.

Objective To analyze the diagnostic efficacy of computer aided analysis of relevant coronary artery stenosis using dual source computed tomography (DSCT). Methods In a larger scale study patients scheduled for conventional coronary angiography (CA) were additionally examined with DSCT. Based on a 13-segment model 30 CT scans of this study population were analyzed for significant stenosis using conventional 3D charts (3D) as well as a specialized cardiac analysis tool (CAT). Diagnostic accuracy and time to diagnosis was recorded for each vessel separately as well as the three readers’ confidence. Results With severe coronary artery calcifications, 53 false interpretations of segments were found for the total of 390 coronary segments analyzed. 3D and CAT analysis showed a Sensitivity, Specificity, PPV and NPV of 0.59, 0.91, 0.57, 0.92 and 0.57, 0.92, 0.56, 0.92, respectively. No significant differences in diagnostic accuracy could be found between 3D and CAT (P = 0.1667). 3D took a mean of 5.2 min (3–10 min). With CAT a mean time of 8.2 min (4–12 min) was needed. No significant inter-reader time differences (P = 0.4954) and no significant confidence level differences were found between readers and analyzes. Conclusion CAT of the coronary tree shows comparable accuracy to manual 3D analysis but needs improvements concerning coronary tree segmentation times.

Ziele: Die koronare CT-Angiographie mittels Multi-Detektor Computertomographie(MDCT) mit retrospektivem EKG-Gating ermoglicht die nicht-invasive Detektion und Klassifizierung von koronaren Plaques. Geringes Ansprechen auf Clopidogrel beeinflusst das kardiovaskulare Outcome nach koronarer Stentimplantion. Ziel dieser Studie war es, Unterschiede in der Plaqueverteilung zwischen Respondern und Low-Respondern auf die Clopidogrelbehandlung zu ermitteln. Methode: 62 Patienten (52mannlich, 10 weiblich, Durchschnittsalter 64,8±8,9 Jahre) wurden in diese Studie eingeschlossen. Es wurde sowohl eine native Spirale zur Bestimmung des Kalzium-Scores (in agatston score equivalent[ASE]), als auch eine KM-angehobene CT-Koronarangiographie (Sensation 64™[19 Patienten], Somatom Definition™[43 Patienten], Siemens Medical Solutions, Forchheim) vor der Stentimplantation durchgefuhrt. Plaques wurden in kalzifizierte (KP), Misch- (MP) und nicht-kalzifizierte (NP) Plaques eingeteilt. Desweiteren wurde die durchschnittliche Plaquedichte gemessen. Die verbleibende Thrombozytenaggregation („residual platelet aggregation“ [RPA]) wurde 6 Stunden nach Gabe einer loading-Dosis von 600mg Clopidogrel mittels Messung der ADP (20µmol/l) – induzierten Plattchenaggregation bestimmt. Patienten mit einer RPA niedriger als 35% wurden als Responder definiert. Ergebnis: Der mittlere Calcium-Score betrug 736 ASE (0–3126 ASE) und die durchschnittliche Thrombozyteninhibierung 35±19% (0–70%). Insgesamt wurden 494 Koronarplaques erfasst (Responder: 197 KP, 47 MP, 5 NP; Low-Responder: 177 KP, 65 MP, 3 NP). Die Responder(n=38) hatten einen signifikant niedrigeren Agatston-Score (mittlerer ASE 405 vs. 912, p

Functional analysis using MDCT has been limited by insufficient temporal resolution. The aim of this study was to assess the performance of a dual-source CT system with improved temporal resolution in the determination of both volume- or time-dependent functional parameters and regional wall motion in comparison with cine MRI.Twenty patients (15 of whom had previous myocardial infarction) were prospectively examined using dual-source CT. MRI was used as the standard of reference. Using the Simpson's method, ventricular volumes were determined for the whole of the cardiac cycle and results compared using Parson's correlation and Bland-Altman analysis. Regional wall motion was assessed on cine images and compared using weighted kappa statistics.Dual-source CT revealed a strong correlation with cine MRI regarding the quantification of end-diastolic volume (r = 0.98), end-systolic volume (r = 0.99), stroke volume (r = 0.96), and ejection fraction (r = 0.95). Good correlation was obtained for peak ejection rate (r = 0.79) and peak filling rate (r = 0.84), whereas agreement proved only moderate for time-to-peak ejection rate (r = 0.68) or time-to-peak filling rate from end-systole (r = 0.64). The mean difference for ejection fraction was negligible (bias, 0.72%). Good agreement between both techniques was likewise found for regional wall motion (kappa = 0.88).With the improvement of temporal resolution between 42 and 83 milliseconds, dual-source CT not only enables accurate assessment of global functional parameters, but it also allows for quantification of time-dependent variables and reliable evaluation of regional wall motion.

Cardiac multi-detector computed tomography (MDCT) with retrospective ECG-gating permits the determination and quantification of coronary calcifications. High calcium scores are known to be associated with elevated all-cause mortality. Moreover, low response to clopidogrel influences cardiovascular outcome after coronary stent placement. We sought to evaluate whether elevated calcium scores are associated with a low response to clopidogrel. Methods 62 patients were enrolled in this trial (52 male, mean age 64.8 ± 8.9 years). Coronary calcium scoring (expressed as Agatston score equivalent, ASE) was measured with multi-slice computed tomography (Sensation 64™ [n=19] and Somatom Definition ™ [n=43], Siemens, Forchheim, Germany) prior to stent implantation. Responsiveness to clopidogrel was assessed by ADP (20 micromol/L)-induced aggregometry at least 6 h after administration of a loading dose of 600 mg clopidogrel. Results Median calcium score was 736 ASE [range 0 –3126] and mean platelet inhibition was 35±19% [range 0 –70]. There was a significant negative correlation between ASE and response to clopidogrel (r 2 =0.135, p=0.0033, slope 7.809 ± 2.549). Patients within the first quartile of ASE had significantly better response to clopidogrel than other patients (p Conclusions We could demonstrate that elevated ASE is associated with a low response to clopidogrel. Patients with a low coronary plaque burden are more likely to have a good response to clopidogrel. Coronary calcium scoring might help to identify low responders to clopidogrel prior to stent placement and aggregometry.

Objective: The aim of this study was to assess DSCT for evaluation of coronary artery disease in an unselected patient population. Impact of heart rate, heart rate variability and calcification on image quality and diagnostic accuracy were, thereby, considered. Subjects and Methods: 100 consecutive patients with known or suspected CAD underwent DSCT and invasive coronary angiography. Image quality (IQ) was assessed using a 4-point scale (1: excellent; 4: non-diagnostic). Accuracy of DSCT in detection or exclusion of significant stenosis (>50%) was evaluated on a per-segment and per-patient level. Effects of heart rate, heart rate variability and calcification on IQ and accuracy were analyzed by multivariate regression and between subgroups of predictor variables. Simple regression was performed to calculate thresholds for adequate IQ. Results: Average heart rate was 64.9± 13.2 bpm, mean variability 23.6± 36.2 beats per CT-examination and mean Agatston score 786.5± 965.9. Diagnostic image quality was obtained in 90.2% of segments. Sensitivity, specificity, positive and negative predictive values for the presence of significant stenosis was: by segment 91.1%, 92.0%, 75.4% and 97.5%; by patient 100%, 81.5%, 93.6% and 100%. According to multivariate regression, IQ was significantly related to heart rate variability and calcification (P=0.025; P Conclusion: Whilst DSCT achieves heart rate independent image quality, the latter remains prone to heart rate variability and calcification. In an unselected patient collective, calcium burden proves to be the single determinant of diagnostic accuracy.

Background Cardiac multidetector computed tomography (MSCT) permits the visualization of coronary artery stenosis. However, in patients with severe coronary calcifications, higher heart rates, and arrhythmia, MSCT was found to have limitations because of insufficient temporal and spatial resolution. Objective The aim was to evaluate the diagnostic accuracy of a new dual-source computed tomography (DSCT) scanner generation with 83-ms temporal resolution in cardiac imaging, especially in patients with high calcium scores and a high prevalence of coronary artery disease (CAD). Methods Of 82 unselected consecutive patients scheduled for invasive coronary angiography, 41 persons were identified to have severe coronary calcifications (Agatston score > 350; 35 men; 66.2 ± 8.4 years). All coronary segments were analyzed after intravenous injection of contrast media for the presence of coronary artery lesions. Results Mean heart rate was 64 ± 14 beats/min. Sixteen (39%) of 41 patients had nonsinus rhythm. Mean Agatston score equivalent (ASE) was 1391 (median 1146; range 358–3898). Prevalence of CAD was 98% (40 of 41). From a coronary segment model, sensitivity was 91%, specificity was 84%, positive predictive value was 70%, and negative predictive value was 96% for the detection of significant lesions (>50% diameter stenosis). Vessels with false-positive results had significantly higher ASE values than coronaries without false-positive results (median, 319.1 vs 143.3; P Conclusion In unselected patients with severe coronary calcifications, a high prevalence of CAD and a large percentage with heart rhythm irregularities, our data indicate that the accuracy of DSCT is limited in clinical routine.