Our standard cardiac CT examination has two parts. First, we start with an un-enhanced high-resolution CT of the heart. This will be analyzed to provide a quantitative evaluation of the amount of calcium present in the coronary arteries. The second part of the CT examination, the cardiac CT angiogram, requires placement of ECG electrodes on the patient's chest to monitor the heart rate throughout the study. To optimize imaging, the patient's heart rate should be below 65 BPM, and therefore an oral beta-blocker will typically be administered to the patient in the radiology department one hour prior to the examination (if no contraindications exist). Occasionally, additional intravenous beta-blocker will be administered to the patient immediately prior to the study, in order to further slow the heart rate. Because of the speed of the Siemens Dual Source CT— Somatom Definition, the need to have the patient take a beta-blocker is most often eliminated. However, depending on the clinical scenario, some patients may still require administration of beta-blocker to optimize the cardiac CT angiogram. An 18- or 20-gauge angio-catheter is placed into a vein in the patient's arm for administration of nonionic intravenous contrast material. Because of the intravenous contrast administration, patients will need to abstain from eating for 3 hours prior to the study. A dose of sublingual nitroglycerine will also usually be given to the patient immediately prior to image acquisition for the cardiac CT angiogram to help dilate the cardiac arteries. Both parts of the study require the patient to hold their breath for approximately 10-15 seconds (the time it takes to scan the heart). The entire CT examination takes approximately 20-30 minutes. Patients may return to normal activity immediately following the examination.