Anja Reimann

Dual-Source CT: Effect of Heart Rate, Heart Rate Variability, and Calcification on Image Quality and Diagnostic Accuracy

PURPOSE 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. MATERIALS AND METHODS 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. RESULTS 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). CONCLUSION While dual-source CT resulted in heart-rate independent image quality, image quality remained prone to heart rate variability and calcification.

Influence of a lipid-lowering therapy on calcified and noncalcified coronary plaques monitored by multislice detector computed tomography: results of the New Age II Pilot Study.

Purpose: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. Methods:Forty-sixe male patients (mean, 61 ± 10 years) with an elevated risk for CAD (PROCAM score >3 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. Results: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, P < 0.0001 and 148 ± 7 mg/dL vs. 88 ± 5 mg/dL, P < 0.001, 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, P > 0.05), whereas mean plaque volume of noncalcified plaques decreased significantly from 0.042 ± 0.029 mL versus 0.030 ± 0.014 mL (P < 0.05, mean reduction 0.012 ± 0.017 mL or 24 ± 13%). Conclusions: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.

Dual-source computed tomography: advances of improved temporal resolution in coronary plaque imaging.

Objectives:The aim of this study was to quantify image quality gains of a moving coronary plaque phantom using dual-source computed tomography (DSCT) providing 83 milliseconds temporal resolution in direct comparison to 64 slice single-source multidetector CT (MDCT) with a temporal resolution of 165 milliseconds. Materials and Methods:Three cardiac vessel phantoms with fixed 50% stenosis and changing plaque configurations were mounted on a moving device simulating cardiac motion. Scans were performed at a simulated heart frequency of 60 to 120 bpm. Image quality assessment was performed in different anatomic orientations inside a thoracic phantom. Results:A significant improvement of image quality using the DSCT could be found (P = 0.0002). Relevant factors influencing image quality aside from frequency (P = 0.0002) are plaque composition (P < 0.0001), as well as orientation (P < 0.0001). Conclusion:Scanning with 83 milliseconds temporal resolution improved image quality of coronary plaque at higher heart frequencies.

Dual-Source CT with Improved Temporal Resolution in Assessment of Left Ventricular Function: A Pilot Study

OBJECTIVE 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. SUBJECTS AND METHODS 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 Simpsons method, ventricular volumes were determined for the whole of the cardiac cycle and results compared using Parsons correlation and Bland-Altman analysis. Regional wall motion was assessed on cine images and compared using weighted kappa statistics. RESULTS 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). CONCLUSION 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.

Coronary CT angiography with dual source computed tomography in 170 patients

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 > or =50% diameter stenosis. DSCT correctly identified 336 of these lesions. 115 lesions with a diameter stenosis < or =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.

Assessment of myocardial viability in a reperfused porcine model: evaluation of different MSCT contrast protocols in acute and subacute infarct stages in comparison with MRI.

Objective: To assess myocardial viability in acute and subacute infarcts using different multislice spiral computed tomography contrast protocols with magnetic resonance imaging (MRI) correlation. Methods: Seven pigs were studied with 64-multislice spiral computed tomography and MRI (1.5 T) at a median of 1 and 21 days after temporary occlusion of the second diagonal branch. Computed tomography was performed at 3, 5, 10, and 15 minutes after injection of contrast medium. Contrast agent was applied either as a bolus (protocol 1; n = 7 for the first; n = 5 for the second scan) or as a bolus plus 30 mL of subsequent 0.1 mL/s low-flow (protocol 2; n = 7 for the first; n = 6 for the second scan). Finally, histological sections were obtained. Volumes of infarcted myocardium were assessed as the percentage of the left ventricle. Computed tomography attenuation values were obtained, and image quality was assessed. Results: When compared with protocol 1, protocol 2 provided greater Hounsfield unit attenuation difference between viable and nonviable myocardium at 5, 10, and 15 minutes (P = 0.19; 0.003; 0.0006) and an additional significant contrast between nonviable myocardium and ventricular blood at 3 and 5 minutes (P < 0.001). Image quality was rated significantly higher with the use of protocol 2 at 5, 10, and 15 minutes (P ≤ 0.027) and for all time points use of protocol 2 resulted in improved correlation of acute and subacute infarct size with MRI. Conclusions: Good correlation of infarct zones with MRI was achieved for both acute and subacute infarcts. With the use of a bolus/low-flow protocol, image quality was substantially improved by means of a higher tissue contrast.

Cardiac Dual-Source Computed Tomography : Effect of Body Mass Index on Image Quality and Diagnostic Accuracy

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/m2. 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/m2 (P < 0.05). Although the proportion of segments with diagnostic image quality was equal in all BMI subgroups, linear regression suggested 25 kg/m2 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.

Atypical cases of gallstone ileus evaluated with multidetector computed tomography

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 MDCT, 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.

Cardiac dual-source computed tomography in patients with severe coronary calcifications and a high prevalence of coronary artery disease

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 < 0.001). 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.

Quantitative parameters to compare image quality of non-invasive coronary angiography with 16-slice, 64-slice and dual-source computed tomography.

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 p < 0.05), 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 (p < 0.05). BMI had no impact on the CA ratio in DSCT only (p < 0.001). 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.