S. Busch

Diagnostic accuracy of dual-source computed tomography in the diagnosis of coronary artery disease.

Purpose:The aim of this study was to evaluate the diagnostic accuracy of dual-source computed tomography (DSCT) with reference to invasive coronary angiography in the diagnosis of coronary artery disease (CAD) on a per-patient as well as on a per-segment basis. Materials and Methods:Thirty-five patients with known or suspected CAD underwent both DSCT (Somatom Definition, Siemens Medical Solutions) and quantitative x-ray coronary angiography (QCA). Parameters of CT acquisition were gantry rotation time 0.330 seconds (ie, temporal resolution 83 milliseconds), tube voltage 120 kV, tube current 560 mA with ECG-triggered tube current modulation and full current at 70% of the cardiac cycle for heart rates below 70 beats per minute or full current between 30% and 80% for higher and arrhythmic heart rates. The pitch was also adapted to the heart rate, ranging from 0.2 to 0.43. Volume and flow rate of contrast material (Ultravist 370, Schering AG) were adapted to the patients body weight. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of DSCT in the detection or exclusion of significant CAD (ie, stenoses >50%) were evaluated on a per-patient and per-segment basis. Results:All 35 CT angiograms were of diagnostic image quality. QCA demonstrated significant CAD in 48% (n = 17) and nonsignificant disease or normal coronary angiograms in 52% (n = 18) of the patients. Sensitivity, specificity, PPV, and NPV of DSCT on a per-patient basis were 100%, 89%, 89%, and 100%, respectively. On a per-segment basis, 473 of 481 coronary artery segments were assessable (98%). QCA demonstrated stenoses >50% in 32 segments (7%), and no disease or nonsignificant disease in 433 segments (93%). For the detection of stenoses >50% on a per-segment basis, DSCT showed a sensitivity, specificity, PPV, and NPV of 88%, 98%, 78%, and 99%, respectively. Conclusions:The comparison of coronary DSCT with QCA shows a very robust image quality and a high diagnostic accuracy in a patient-based as well as a per-segment analysis. Maximal sensitivity and NPV in the per-patient analysis show the strength of the technique in ruling out significant CAD.

Visual and automatic grading of coronary artery stenoses with 64-slice CT angiography in reference to invasive angiography

The aim of this study was to assess the performance of a software tool for quantitative coronary artery analysis of computed tomography coronary angiography (CT-QCA) in comparison with invasive coronary angiography with quantitative analysis (CAG-QCA) as standard of reference. Two radiologists reviewed the CT angiography data sets (Siemens Sensation 64) of 25 patients, grading coronary artery stenoses visually and with a software tool (Circulation, Siemens). Twenty-three data sets with sufficient image quality were included in the final analysis. CAG revealed a total of 30 wall irregularities and 28 stenoses, of which 17 were graded as moderate and nine as hemodynamically significant. CT-QCA showed a better agreement to CAG-QCA, with a systematic overestimation of the degree of stenosis of 6.1% and limits of agreement of +36.1% and −23.9; the correlation coefficient was 0.82 (p < 0.0001). Using CT-QCA, sensitivity, specificity, and positive and negative predictive value were 89%, 100%, 89%, and 100%, respectively, for significant area stenoses greater than 75%. The positive predictive value for the visual assessment amounted to 53%. Interobserver variability between CT-QCA and visual assessment showed a kappa value of 0.72. In conclusion, software-supported CT-QCA makes it possible to quantify significant coronary artery stenoses automatically, with good agreement to CAG-QCA.

Evaluation of Left Atrial Myxoma by Dual-Source CT

A 63-year-old female patient was referred for exclusion of coronary artery disease prior to cardiac surgery. She had presented at her general practitioner with unexplained exhaustibility and an inadequate increase in heart rate and blood pressure upon exercise. Echocardiography revealed a mass in the left atrium, but dignity and attachment to the interatrial septum or the mitral valve had remained unclear. Computed tomography (CT) was performed on a 64-slice dual-source CT scanner (Somatom Definition; Siemens, Malvern, PA USA) at 120-kVp tube voltage and 560-mA tube current with ECG-triggered modulation and 2 · 32 · 0.6-mm collimation. Calculated dose amounted to 5.2 mSv. One hundred twenty milliliters of iopromide (Ultravist 300; Schering, Germany) followed by 50 ml of saline chaser were injected at a flow rate of 5 ml/s, and the scan was initiated by automatic bolus tracking in the ascending aorta. Images were reconstructed at 10% intervals of the cardiac cycle using a medium-soft convolution kernel (B26f) with a slice thickness of 0.75 mm and a distance of 0.5 mm. Multiplanar and volume-rendered cine loops offered a good depiction of coronary artery morphology, wall motion, and valve function. The coronary arteries showed no atherosclerotic alterations (Fig. 1). In cross-sectional dynamic images, the left atrial mass could be visualized without motion-related blurring (Fig. 2a). The pedunculated tumor of 2.3-cm diameter was attached to the interatrial septum and swayed in tune with the cardiac cycle but never prolapsed into the mitral valve (Figs. 2a and b). The hypoattanuated mass demonstrated small speckled calcifications (Fig. 2a). This location and morphology were regarded as typical for a myxoma [1]. There was clearly no involvement and no significant obstruction of the mitral valve. Left ventricular morphology and wall motion as well as aortic and mitral valve function were normal. Characteristic features of malignant tumors such as involvement of more than one chamber, intramural spread or infiltration, broad attachment, extension into pulmonary veins or arteries, combined intramural and intracavitary location, hemorrhagic pericardial effu-