cardiovascular disorders
Cardiac Imaging Tests
Introduction
Cardiac imaging tests can delineate cardiac structure and function. Standard imaging tests include Echocardiography None Chest X-Rays in Cardiac Diagnosis None Computed Tomography (CT) in Cardiac Diagnosis None Magnetic Resonance Imaging (MRI) in Cardiac Diagnosis None Various Radionuclide Imaging of the Heart None Standard CT and MRI have limited application because the heart constantly beats, but faster CT and magnetic resonance techniques can provide useful cardiac images if the rhythm is regular and the heart rate is controlled; sometimes patients are given a drug (eg, a beta-blocker) to slow the heart rate during imaging. InECG gating,the image recording (or reconstruction) is synchronized with the electrocardiogram (ECG), providing information from several cardiac cycles that can be used to create single images of selected points in the cardiac cycle. CT gatinguses the ECG to trigger the x-ray beam at the desired portion of the cardiac cycle, exposing the patient to less radiation than gating that reconstructs information from only the desired portion of the cardiac cycle (gated reconstruction) and does not interrupt the x-ray beam. 