Beyond perfusion with ultrafast computed tomography.

Abstract

Ultrafast computed tomography (CT) has been available for the clinician for nearly 10 years. Although cost, as well as availability of competing technologies, have limited its application, several investigative groups have demonstrated the feasibility of measuring regional myocardial blood flow by this method. Ultrafast CT provides accurate measurements when myocardial blood flow is normal or reduced. However, when flow is increased (e.g., by pharmacologic vasodilation), the technique underestimates flow. (This can apparently be corrected by using a complex curve-fitting technique.) Direct injection of contrast medium into the aorta distinguishes differences in endocardial and epicardial blood flow. Although imaging of myocardial perfusion has proven clinical value, there is a need for new noninvasive approaches for detecting silent coronary atherosclerosis before coronary events occur. Here it is possible to make use of the close association between coronary atherosclerosis and coronary intimal calcium, recognized over 35 years ago. Even though the amount of coronary calcium is a function of age, individuals with coronary artery disease usually have greater amounts, and the greater the number of coronary vessels with calcium, the greater the likelihood of obstructive coronary disease. Ultrafast CT has proven value for visualizing coronary calcium. No contrast medium is required and radiation exposure is approximately 425 mrads.