Coronary angiography by electron beam tomography

Electron Beam Tomography (EBT), a non-invasive imaging method with very high spatial and temporal resolution, is well suited for cardiac imaging. We established a protocol for the visualization of the coronary arteries by EBT and have so far evaluated the method in 88 patients. EBT imaging was performed using an Evolution scanner with a matrix of 512 x 512, a field of view of 15 cm and a slice thickness of 3 mm. After venous injection of contrast agent, 40 axial cross-sections of the heart were obtained triggered to the ECG at 80% of the R-R interval in inspiratory breathhold. With a lower threshold of 80 HU, 3D reconstructions of the heart and coronary arteries were rendered using shaded-surface display and maximum-intensity projection techniques. In all patients, the coronary arteries and, if present, aorto-coronary bypass grafts, were evaluated as to their visibility and presence or absence of haemodynamically relevant stenoses. All results were compared to the X-ray angiograms obtained by selective catheterization in a blinded manner. In 90% of cases, image quality was sufficient for evaluation. In 10% of the investigations, the EBT images could not be evaluated, mainly due to respiration artifacts. While the left anterior descending coronary artery was represented in very good image quality, the right coronary artery and left circumflex coronary artery showed decreased image quality due to motion artifacts and close correlation to venous structures such as the coronary sinus and atrial appendages. In a subgroup of 30 patients in which EBT results were compared to quantitative coronary angiography, the correlation of the vessel diameter in EBT and quantitative angiography was 0.82. Twelve out of 14 high-grade stenoses and 5/5 occlusions of the left anterior descending coronary artery as well as 3/4 highgrade stenoses and 1/2 occlusions of the right coronary artery and 2/4 high-grade stenoses of the left circumflex coronary artery were correctly identified. Nine patients were reinvestigated by EBT after successful angioplasty of high-grade coronary artery stenoses. The increase in vessel diameter could be documented in all cases. Twelve patients had a total of 28 aorto-coronary bypass grafts. Except for one mammarian artery graft which could not be evaluated due to small vessel lumen and clip artifacts, graft patency (21 cases) or occlusion (6 cases) was correctly diagnosed by EBT. EBT is a non-invasive method which permits the visualization of the coronary arteries. Stenoses of coronary artery bypass grafts and of the left anterior descending coronary artery can be reliably diagnosed, while reduced image quality, mainly due to faster vessel motion, impairs the results obtained for the right and left circumflex coronary artery.