Christof Burgstahler

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.

Reliability of differentiating human coronary plaque morphology using contrast-enhanced multislice spiral computed tomography : A comparison with histology

Background: Initial clinical results indicate that multislice spiral computed tomography (MDCT) might be useful for the noninvasive characterization of human coronary plaque morphology by determining tissue density within the lesions. This seems to be of clinical relevance, because coronary artery disease might be detected at an early stage before calcifications occur and noncalcified plaques that may be more likely to rupture could also be visualized noninvasively. The aim of the present study was to evaluate the reliability of contrast-enhanced MDCT in differentiating human atherosclerotic coronary plaque morphology by comparing it with the histopathologic gold standard. Methods and Results: Twelve human hearts were scanned postmortem using an MDCT (Somatom Volume Zoom; Siemens, Forchheim, Germany) high-resolution computed tomography scanner to detect atherosclerotic coronary plaques. Density measurements were performed within detected plaque areas. The exact location of each plaque was marked at the surface of the heart to assure accurate histopathologic sectioning of these lesions. The plaques were classified according to a modified Stary classification. Seventeen plaques were identified by MDCT. Six plaques were histopathologically classified as lipid rich (Stary III/IV), 6 plaques as intermediate (Stary V), and 5 plaques as calcific (Stary VII). Lipid-rich plaques had a mean density on MDCT of 42 ± 22 Hounsfield units (HU), intermediate plaques had a mean density of 70 ± 21 HU, and calcific plaques had a mean density of 715 ± 328 HU. ANOVA analysis revealed a significant difference in plaque density between the 3 groups (P < 0.0001). Conclusions: The comparison with histopathology confirms that tissue density as determined by contrast-enhanced MDCT might be used to differentiate atherosclerotic plaque morphology.

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.

Image quality and diagnostic accuracy of non-invasive coronary imaging with 16 detector slice spiral computed tomography with 188 ms temporal resolution

Objective: To evaluate image quality and clinical accuracy in detecting coronary artery lesions with a new multidetector spiral computed tomography (MDCT) generation with 16 detector slices and a temporal resolution of 188 ms. Methods: 124 consecutive patients scheduled for invasive coronary angiography (ICA) were additionally studied by MDCT (Sensation 16 Speed 4D). MDCTs were analysed with regard to image quality and presence of coronary artery lesions. The results were compared with ICA. Results: 120 of 124 scans were successful. The image quality of all remaining 120 scans was sufficient (mean (SD) heart rate 64.2 (9.8) beats/min, range 43–95). The mean calcium mass was 167 (223) mg (range 0–1038). Thirteen coronary segments were evaluated for each patient (1560 segments in total). Image quality was graded as follows: excellent, 422 (27.1%) segments; good, 540 (34.6%) segments; moderate, 277 (17.7%) segments; heavily calcified, 215 (13.8%) segments; and blurred, 106 (6.8%) segments. ICA detected 359 lesions with a diameter stenosis > 50% and MDCT detected 304 of 359 (85%). Sensitivity, specificity, and positive and negative predictive values were 85%, 98%, 91%, and 96%, respectively. The correct clinical diagnosis (presence or absence of at least one stenosis > 50%) was obtained for 110 of 120 (92%) patients. Conclusions: MDCT image quality can be further improved with 16 slices and faster gantry rotation time. These results in an unselected population underline the potential of MDCT to become a non-invasive diagnostic alternative, especially for the exclusion of coronary artery disease, in the near future.

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.

Safety, Efficacy, and Indications of β-Adrenergic Receptor Blockade to Reduce Heart Rate prior to Coronary CT Angiography

For selected indications, coronary computed tomographic (CT) angiography is an established clinical technology for evaluation in patients suspected of having or known to have coronary artery disease. In coronary CT angiography, image quality is highly dependent on heart rate, with heart rate reduction to less than 60 beats per minute being important for both image quality and radiation dose reduction, especially when single-source CT scanners are used. β-Blockers are the first-line option for short-term reduction of heart rate prior to coronary CT angiography. In recent years, multiple β-blocker administration protocols with oral and/or intravenous application have been proposed. This review article provides an overview of the indications, efficacy, and safety of β-blockade protocols prior to coronary CT angiography with respect to different scanner techniques. Moreover, implications for radiation exposure and left ventricular function analysis are discussed.

Non-invasive evaluation of coronary artery bypass grafts using multi-slice computed tomography: initial clinical experience

Recurrence of angina pectoris in patients with previous coronary artery bypass graft (CABG) surgery due to severe coronary artery disease (CAD) is a common problem. Non-invasive imaging of coronary artery bypass grafts by computed tomography was first described in the early 1980s. Meanwhile, multi-slice computed tomography (MSCT) is now available. This new technique allows detection of coronary lesions with good sensitivity and specificity due to continuous improvement and modification of this method. The aim of this study was to investigate whether stenosis or occlusion of CABG can be detected by MSCT. Ten consecutive male patients (mean age 61+/-9.1 years) with previous CABG surgery and 21 bypass grafts (14 venous grafts, seven arterial grafts) were included in this study. Conventional coronary angiography and MSCT angiography (MSCTA) were performed in all patients. MSCTA results were compared with coronary angiography in regard of visualization and lesion detection in CABG. The analysis of MSCTA was performed blinded to the angiographic results. It was found that 18 of 21 bypass grafts (86%) were analyzable by MSCTA: seven of 21 (33%) grafts showed a significant stenosis (>75%), while six of them were detected by MSCTA (sensitivity: 86%, positive predictive value: 0.75). Dissection of one arterial graft could not be evaluated by MSCTA. Twelve of 13 grafts without severe lesion showed no significant stenosis in MSCTA (negative predictive value: 0.86). All grafts without severe lesions by MSCT showed no significant lesion in X-ray angiography (specificity: 100%). MSCTA is a promising new method for the detection of lesions in coronary artery bypass grafts. However, these data based on a small number has to be reevaluated by larger studies.

Non-invasive evaluation of atherosclerosis with contrast enhanced 16 slice spiral computed tomography: results of ex vivo investigations

Objective: To evaluate the diagnostic accuracy of 16 slice computed tomography (CT) in determining plaque morphology and composition in an experimental setting. The results were compared with histopathological analysis as the reference standard. Methods: Nine human popliteal arteries derived from amputations because of atherosclerotic disease were investigated with multislice spiral CT (MSCT). Atherosclerotic lesions were morphologically classified (completely or partially occlusive, concentric, eccentric), and tissue densities were determined within these plaques. In addition, vessel dimensions were quantitatively measured. Results: The results were compared with histological analysis. The concordance index κ for morphological classification was 0.88. Plaque density (n  =  51 lesions) was significantly different (p < 0.0001) between lipid rich, fibrotic, and calcified lesions (Stary stage III: n  =  2, 58 (8) Hounsfield units (HU); Stary V: n  =  11, 50 (21) HU; Stary VI: n  =  14, 96 (42) HU; Stary VII: n  =  6, 858 (263) HU; Stary VIII: n  =  18, 126 (99) HU). The concordance index κ for the classification of plaques based on density was 0.51. Vessel dimensions had a good correlation (r  =  0.98). Conclusions: 16 slice CT was found to be a reliable non-invasive imaging technique for assessing atherosclerotic plaque morphology and composition. Although calcified lesions can be differentiated from non-calcified lesions, the diagnostic accuracy in further subclassifying non-calcified plaques as lipid rich and fibrotic is low, even under experimental conditions.

Assessment of Left Ventricular Outflow Tract Geometry in Non-Stenotic and Stenotic Aortic Valves by Cardiovascular Magnetic Resonance

PURPOSE To assess the geometry and area of the left ventricular outflow tract (LVOT) in non-stenotic and stenotic aortic valves and to determine the aortic valve area (AVA) in non-stenotic valves by magnetic resonance imaging (MRI) using a modified continuity equation. METHODS Twenty patients (10 male, mean age 54.8 +/- 15 years) without known aortic valve disease and 10 patients (7 male, mean age 65.1 +/- 14 years) with moderate to severe aortic stenosis were included in this study. MRI was performed using a 1.5 T scanner (Philips Intera CV). AVA was assessed by planimetry on high quality SSFP cine sequences and used as reference standard. LVOT area was defined by calculating a circular area using the LVOT diameter from the 3 chamber view (3CV) and by planimetry. Peak flow velocity was assessed in the LVOT and the proximal aorta. AVA was calculated by a modified Gorlin equation, the continuity equation and a modified continuity equation using the planimetric LVOT area. RESULTS Planimetric AVA ranged from 2.9 to 6.4 cm2 in patients with non-stenotic and from 0.3 to 1.3 cm2 with stenotic valves, LVOT area from 3.4 to 6.1 cm2 and from 2.6 to 6.5 cm2, respectively. The LVOT area based on the LVOT diameter derived from the 3CV was significantly underestimated in comparison to planimetry in non-stenotic and stenotic aortic valves (3.3 +/- 0.7 vs. 4.7 +/- 1.0 cm2, p < 0.0001; mean difference 1.1 +/- 0.12 cm2, CI 0.86-1.36 and 3.7 +/- 1.2 vs. 4.7 +/- 1.5 cm2, p < 0.05; mean difference 1.0 +/- 1.0 cm2, CI 0.24-1.71). The Gorlin formula showed a poor agreement with planimetry, whereas continuity equation and the modified continuity equation revealed a very good agreement. Planimetry of the LVOT displayed an elliptic shape of the LVOT in all patients with the minimum diameter perpendicular to the 3CV, which was the reason for the above mentioned underestimation. CONCLUSION The LVOT area calculated from the 3CV-LVOT diameter underestimates the LVOT area compared to planimetry due to an elliptic shape of the LVOT in patients with non-stenotic as well as with stenotic aortic valves. The modified Gorlin equation proved to be less useful to assess AVA in non-stenotic valves, whereas the continuity equation and a modified continuity equation displayed a very good agreement with planimetric area measurements.