Advances in computed tomography (CT) technology have revolutionized the diagnosis of cardiovascular disease. CT has dramatically reduced, and for some clinical scenarios eliminated, the need for additional testing such as diagnostic arterial catheterization. In the process, CT has become invaluable in cardiac diagnosis and surgical planning.
CT is based on an x-ray source and detector system mounted on the “CT gantry” that rotates around the patient. Major technology advances have enabled CT to image the beating heart, and routine CT at Brigham and Women’s Hospital (BWH) has noninvasively excluded coronary artery disease in one heart beat (Fig. 6-1) for over 7 years.1 However, the role of CT extends far beyond the coronary arteries alone. Using roughly the same CT acquisition strategies, native coronary imaging can be extended to coronary bypass grafts, the beating myocardium, valve motion, the ventricles and ventricular outflow tracks, and cardiac lesions.
Selected coronary computed tomography angiography (CTA) image of the proximal left coronary arterial system in a patient scheduled for isolated mitral valve surgery. Using the protocol detailed in this chapter, CT demonstrated normal coronary arteries in this patient, eliminating the need for arterial catheterization.
In order to understand the clinical contribution of CT and to avoid pitfalls in image interpretation, it is essential for the surgeon to appreciate the basic principles of CT used in cardiac imaging. This chapter is divided into two parts. The first part describes the technical considerations for cardiac CT. By understanding each component, the surgeon will be better able to distinguish image artifacts from pathology. The second part reviews those CT examinations that are most frequently performed in the noninvasive cardiovascular imaging program at BWH, detailing the strengths and limitations of each exam.
PART 1. CARDIAC CT PROTOCOLS
Most advances in cardiac CT, for example in coronary CT angiography (CTA), have focused on the development of protocols consistent with the rapid incremental technology improvements. One of the major technological advances has been the incorporation of multiple elements into the CT detector system, called Multi-Detector CT (MDCT). MDCT is synonymous with multislice CT. Since all modern scanners have multiple detectors, the semantics can and should be eliminated; this chapter simply uses “CT” to describe the technology.
Data from each of CT detector is used to reconstruct an axial slice perpendicular to the long axis, or z-axis, of the patient. The width of the detectors determines the minimum slice thickness and thus the ability to resolve small anatomic detail (spatial resolution) of the scanner. Thinner slices yield superior spatial resolution; however, comparing two scanners that produce the same number of slices, the scanner with thinner slices will have less z-axis (ie, craniocaudal) coverage per gantry rotation and thus will have a longer scan time. To date, ...