Current and future clinical applications of contrast-enhanced cardiac CT: the clinics' perspective.

Abstract

Since the early 1980s, magnetic resonance imaging (MRI) [1] and computed tomography (CT) [2] have been applied to the evaluation of diseases affecting the heart, central vessels, and/or surrounding structures. While use of MRI for assessing the cardiovascular system has gradually become fairly widespread [3], utilization of CT has remained limited by the need for specialized equipment, in particular electron-beam CT (EBCT) [4]. With the advent of multi-detector CT (MDCT) technology [5, 6], however, sub-second ECG-referenced imaging of the central cardiovascular system has also become feasible on conventional CT systems. As a result, motion (cardiac and respiratory)-free imaging of the heart, central vessels, and surrounding structures over an extended range can be accomplished within a breath-hold period [7–11]. The reliance on MDCT technology potentially broadens the worldwide application of cardiovascular CT. Unlike sub-second ECG-referenced MDCT technology, EBCT technology suffers from restricted longitudinal coverage, with complete imaging of the central cardiovascular system usually requiring two breath-holds, but has the advantage of better temporal resolution for dynamic imaging [12–15 S.S. Halliburton et al., submitted]. MDCT technology has the advantage of allowing imaging in either a sequential mode with prospective ECG-triggering [16, 17] or spiral mode with retrospective ECG-gating [7, 8, 20, 21]; while the latter is more suitable for 3D reconstructions [18, 19], it requires greater radiation exposure. Nevertheless, CT is entering the field of cardiac imaging which is already filled with validated modalities. In fact, CT is appearing at a time when MRI, which has many of the same attributes (e.g., 3D imaging), is maturing [3, 22]. Hence, considering current cardiovascular MRI capabilities, the introduction of such potential from contrast-enhanced cardiovascular CT produces a practical dilemma. For some sites, justification for additional investments (i.e., labor or funds) in cardiovascular CT technology is not clear without expectations of gains over already available MRI capabilities. For other sites considering an initial commitment to general cardiovascular imaging, a decision in favor of CT over MRI is not yet fully supported by reported experience. Clinical experiences at large cardiac centers at major multi-specialty clinics (Cleveland Clinic Foundation and Mayo Clinic) indicate that for morphologic assessment of cardiac disease, CT is comparable-to-superior to state-of-the-art MRI from the standpoint of information supplied and clearly superior from the standpoint of ease and expedience of performance. CT has led to the identification of key abnormalities associated with a wide range of acquired or congenital cardiovascular diseases. Of course, CT can be used for cardiac imaging in the setting of MRI contra-indications [23]. In these sessions, the experiences of the Cleveland Clinic Foundation and the Mayo Clinic with MDCT and/or EBCT for the evaluation of key morphologic and/or physiologic abnormalities in patients presenting with arrhythmia, signs of heart failure, or suspected coronary artery abnormalities will be reviewed.