Christoph R. Becker

In the United States, more than 1 million diagnostic invasive coronary angiograms are performed annually, and in about 50% the investigation is followed by an interventional procedure. The remaining symptomatic patients after angiography are treated conservatively or by bypass graft surgery. In recent decades coronary angiography has advanced to a fast and safe investigation. Nevertheless, in particular, patients are well aware of the small but not negligible risk of complications and the discomfort of the invasive procedure. In addition to electrocardiogram (EKG) or ultrasound stress test and thallium scintigraphy, there is further need for another noninvasive method that displays the morphology of the coronary arteries in a way that would allow the triage of patients with suspicion of coronary artery disease (CAD) for a conservative, interventional, or surgical treatment. J. Magn. Reson. Imaging 2004;19:676–685.

This study was designed to determine the optimal contrast protocol for 4-detector-row computed tomography angiography of the heart. Sixty patients were randomly assigned to 1 of 4 groups with 300 and 400 mg/mL iodine concentrations and 2.5 and 3.5 mL/s flow rates. Contrast density was measured in the left ventricular cavity and coronary arteries. Low iodine concentration injected at slow flow rate (0.75 g iodine/s) resulted in acceptable contrast enhancement in only 53.8% of the patients. There was no significant difference between low contrast concentration injected at high flow rate and high contrast concentration injected at slow flow rate ( approximately 1 g iodine/s). High contrast concentration administered with high flow rates (1.4 g iodine/s) may result in an enhancement above 350 Hounsfield units (HU) and interfere with coronary calcifications. The injection of approximately 1 g iodine/s resulted in an optimal (250-300 HU) contrast enhancement for cardiac 4-detector-row computed tomography.

Multi-detector-row CT angiography (CTA) is a new technology that allows for non-invasive investigation of coronary atherosclerosis in patients. The relation between the morphology of atherosclerotic plaques assessed by CTA and histopathology is unknown. We investigated 11 human cadaver heart specimens. A mixture of methylcellulose and CT contrast media was injected into the coronary arteries to achieve in-vivo-like contrast enhancement within the coronary artery lumen. The morphologic pattern of atherosclerotic lesions found on CTA images and the tissue attenuation of non-calcified plaques were determined. After CTA imaging, atherosclerotic lesions in the coronary arteries were macroscopically identified and characterized histopathologically according to American Heart Association criteria. A total of 50 and 40 lesions were found macroscopically and by CTA, respectively. Thirty-three lesions could have been compared directly. The sensitivity of CTA compared with macroscopic detection of atheromas, fibroatheromas, fibrocalcified, and calcified lesions was 73, 70, 86, and 100%, respectively. The mean CT attenuation of predominantly lipid-rich and fibrous-rich plaques was significantly different (47±9 and 104±28 HU, respectively; p<0.01). Atherosclerotic coronary plaques detected by CTA may represent different stages of coronary atherosclerosis. The tissue attenuation of non-calcified plaques may allow for assessment of their predominant component.

Mit der neuesten Generation der Mehrzeilen-CT-Geräte kann das gesamte Herz in einer Atempause von 20 s untersucht werden. In dieser Zeit werden etwa 250 Schichten mit einer Dicke von 1 mm angefertigt. Zusammen mit dem EKG-Signal werden die Bilder mit einer zeitlichen Auflösung von 210 ms aufgenommen. Technische Innovationen: Bei einer Herzfrequenz < 60 Schläge/min können artefaktfreie Bilder in der Diastole angefertigt werden, die nach intravaskulärer Kontrastmittelgabe neben dem Lumen des Koronargefäßes auch Wandveränderungen in Form von verkalkten und nicht verkalkten Plaques darstellen. Dabei weisen diese Wandveränderungen charakteristische Zeichen auf, die eine differentialdiagnostische Zuordnung in Thromben, Atherome und fibrokalzifizierte Plaques zulassen. Koronare Herzerkrankung im CT: Bei symptomatischen Patienten mit unklaren thorakalen Beschwerden kann die CT bei Fehlen solcher Wandveränderungen eine koronare Herzerkrankung mit hoher Sicherheit ausschließen. Bei asymptomatischen Patienten mit kardiovaskulären Risikofaktoren führen wir zunächst eine Untersuchung ohne Kontrastmittel durch, um eine Atherosklerose durch Koronarkalk nachzuweisen. Um das vollständige Ausmaß einer Atherosklerose bei Hochrisikopatienten abzubilden, kann eine kontrastverstärkte CT-Untersuchung erwogen werden. The newest generation multi-detector-row CT scanner is allowed for investigation of the entire heart within a breathhold period of approximately 20 s. Within this time 250 slices with a thickness of 1 mm each are acquired. In conjunction with the ECG signal the images are acquired with a temporal resolution of 210 ms in the mid diastolic phase of the heart. Technical Innovations: In patients with a heart rate < 60 beats per minute images free of motion artefacts can be reconstructed, that allow for assessment of the coronary artery lumen as well as calcified and non-calcified lesions in the coronary artery wall. Such lesions may be differentiated into thrombus, atheroma and fibrocalcified plaques on the base of characteristic morphologic criteria. Coronary Heart Disease in CT: The absence of coronary artery lesions in symptomatic patients with atypical chest pain allows for reliable exclusion for coronary heart disease. In asymptomatic patients with cardiovascular risk factors we first perform an investigation without contrast media to detect coronary calcifications as a marker of atherosclerosis. To assess the complete extent of coronary atherosclerosis in high risk patients, we then consider a contrast enhanced CT study.

The authors compared multislice CT angiography and selective angiography for the assessment of coronary artery disease. In 28 patients, the presence and degree of coronary artery stenoses were determined in coronary segments prepared with β-blocker for good image quality with multislice CT. In 187 coronary artery segments, sensitivity, specificity, and negative predictive value for the detection of stenoses >50% with multislice CT angiography were 81%, 90%, and 97%, respectively. The agreement for determining the degree of stenoses with multislice CT angiography and selective coronary angiography was only moderate (κ = 0.58). Because of the limited spatial resolution, it is not possible with multislice CT angiography to determine the degree the coronary artery stenoses precisely. However, the high negative predictive value indicates that multislice CT may be a suitable tool to reliably rule out coronary artery disease.

PURPOSE: To evaluate the effectiveness of electrocardiographically (ECG)-gated retrospective image reconstruction for multi–detector row computed tomographic (CT) coronary angiography in reducing cardiac motion artifacts and to evaluate the influence of heart rate on cardiac image quality. MATERIALS AND METHODS: Sixty-five patients with different heart rates underwent coronary CT angiography. Raw helical CT data and ECG tracings were combined to retrospectively reconstruct at the defined consecutive z position with a temporal resolution of 250 msec per section. The starting points of the reconstruction were chosen between 30% and 80% of the R-R intervals. The relationships between heart rate, trigger delay, and image quality were analyzed. RESULTS: Optimal image quality was achieved with a 50% trigger delay for the right coronary artery and 60% for the left circumflex coronary artery. Optimal image quality for the left anterior descending coronary artery was equally obtained at 50% and 60% triggering. A s...

Detection of coronary artery calcifications with slice by slice prospective ECG triggering is feasible with electron beam CT as well as with single and multi-row-detector CT (MDCT). The radiation...