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Suppression of respiratory motion is one of the major challenges of magnetic resonance (MR) coronary angiography. Two approaches to compensate for respiratory motion have often been proposed: breath-hold (BH) and free-breathing respiratory-gated (FBRG) imaging. So far, however, these approaches have never been directly compared. MR coronary angiography was performed in 32 patients with suspected coronary artery disease. MR data were acquired using contrast-enhanced BH and FBRG 3-dimensional MR coronary angiographic techniques. MR images were compared with regard to image quality using quantitative parameters and with regard to accuracy for stenosis detection in the proximal and mid-coronary segments in comparison to x-ray angiography. With regard to image quality, BH was superior to FBRG. Signal-to-noise ratio was 29.1 +/- 10.7 for BH versus 18.8 +/- 9.7 for FBRG (p <0.05) and contrast-to-noise was 18.0 +/- 7.4 for BH versus 11.3 +/- 7.9 for FBRG (p

In recent years, several techniques for noninvasive imaging of the coronary artery lumen (noninvasive coronary angiography) have been developed. These techniques include magnetic resonance imaging, electron-beam computed tomography, and, most recently, multislice computed tomography. Each of these techniques has specific advantages and disadvantages. Currently, EBCT seems to permit the most robust coronary artery imaging. In the future, imaging modalities will have to be further improved and validated in order to define specific areas for potential clinical applications.

In 120 patients, the mean interscan variability of coronary calcium quantification by electron beam tomography was 19.9% (median 7.8%) for the traditional calcium score, and 16.2% (median 5.7%) for volumetric scoring. Although this difference was not significant, there was a significant influence of the total amount of calcium, number of acquired images, and image noise on interscan reproducibility.

Anomalous coronary arteries are rare conditions. However, they may cause myocardial ischemia and sudden death and their reliable identification is crucial for any imaging method that attempts coronary artery visualization. We studied the ability of contrast-enhanced electron beam tomography (EBT) to identify anomalous coronary arteries and their course. Thirty patients with previously identified coronary anomalies and 30 subjects with normal coronary anatomy were studied. By EBT, 40 to 50 axial images of the heart (3-mm slice thickness, 1 mm overlap, electrocardiographic trigger) were acquired in a single breathhold during continuous injection of contrast agent (160 ml, 4 ml/s). Based on the original images and 3-dimensional reconstructions, the EBT data were analyzed by 2 blinded observers as to the presence of coronary anomalies and their course. Results were compared with invasive angiography. EBT correctly identified all normal controls and all patients with coronary anomalies. The anatomic course of the coronary anomalies was correctly classified in 29 of 30 patients (97%), including right-sided origin of the left main coronary artery (n = 4) or of the left circumflex coronary artery (n = 15), left-sided origin of the right coronary artery (n = 9), and 1 coronary fistula from the left circumflex coronary artery to the right atrium. Only the distal anastomosis of a second fistula from the left circumflex coronary artery to a bronchial artery was not correctly identified. This study demonstrates that contrast-enhanced EBT is a reliable noninvasive technique to identify anomalous coronary arteries and their course.

Magnetic resonance coronary angiography (MRCA) is a promising method for the assessment of proximal coronary artery stenosis. Conventional 2-dimensional techniques require repetitive breath holds to image multiple sections. This may lead to misregistrations if the respiratory level is not exactly reproduced. In the present study, MRCA was performed using a 3-dimensional approach with navigator echo-based respiratory gating. In 73 patients (55 men and 18 women) who were referred for cardiac catheterization, the assessment of significant stenoses (> or = 50%) was performed in the proximal and midsegments of the coronary arteries after multiplanar reconstruction of the visualized coronary arteries. In addition, in 8 patients with coronary artery bypass grafts the patency of the transplants was evaluated. After withdrawing 8 patients from analysis because of poor image quality, stenosis evaluation was possible in 236 of 455 reviewed coronary segments (52%). In the other 219 cases, either the visualization of the vessel segment was indistinct (30%) or the segment was located outside the imaging volume (18%). In total, 28 of 43 significant coronary stenoses could be correctly identified (65%). Evaluation of bypass graft patency was possible in 7 patients. All 4 occluded and 13 of 15 patent grafts were correctly classified. Thus, respiratory gated MRCA is a feasable method for the assessment of hemodynamically significant coronary stenoses and bypass graft patency. However, technical improvements are mandatory to improve accuracy of the method.

Electron beam tomography (EBT, ultrafast computed tomography [CT], cine CT) combines unique temporal and high spatial resolution and is especially well suited for cardiac imaging. We established and evaluated a protocol for the noninvasive visualization and assessment of aortocoronary artery bypass grafts. Twenty-five patients with 56 bypass grafts were studied by EBT. Forty contiguous cross-sectional images were acquired triggered to the electrocardiogram during breathhold and intravenous injection of contrast agent. Three-dimensional reconstructions of the heart and bypass grafts were performed and compared with selective angiography of the bypass grafts. In 1 patient with 2 bypass grafts, a technically inadequate EBT examination was obtained. In the remaining patients (54 grafts), all 13 bypass occlusions were diagnosed with a sensitivity and specificity of 100%. Evaluation for hemodynamically relevant stenosis was possible in 84% of cases (36 of 43 patent grafts) and yielded a sensitivity of 100% (5 of 5 high-grade stenoses correctly detected) and specificity of 97% (1 false-positive diagnosis of high-grade graft stenosis). The main reasons for impaired ability to evaluate the scans were breathing artifacts and misplacement of the imaging volume, causing parts of the bypass grafts to be cut off. EBT permits noninvasive determination of bypass graft occlusion and relevant stenosis with high accuracy.