Cardiac Imaging - Technical Advances in MDCT Compared with Conventional X-ray Angiography

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US Cardiology 2006;2005:2(1):1-5

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Coronary artery disease (CAD) represents the major cause of morbidity and mortality in Western populations.1 The prime diagnostic tool that allowed the development of rational treatment techniques for this disease is invasive coronary angiography ((CA) an X-ray fluoroscopy guided procedure), which is associated with a low rate of life-threatening complications.2 More than 40% of the invasive CA studies are also carried out for the purpose of ruling out CAD.3 Non-invasive cardiac assessment has therefore been a goal of investigators for decades; however, the coronary arteries in particular prove a formidable challenge because of their small size (3-4mm), tortuous course, and susceptibility to cardiac and respiratory motion. In addition, the evaluation of cardiac function requires excellent temporal resolution on the order of less than 100ms. Echocardiography (ECG), nuclear medicine techniques, and MRI have been used non-invasively for a variety of cardiac indications, although no single technique provides a comprehensive assessment.

The prospect of imaging the heart and coronary arteries using computed tomography (CT) has been anticipated since the development of CT more than three decades ago. The lack of speed and poor temporal resolution of previous generations of CT scanners prevented meaningful evaluation of the coronary arteries and cardiac function. Most early assessments of the coronary arteries with CT were performed with electron beam computed tomography (EBCT), developed in the early 1980s.4 EBCT has been mostly used for the non-invasive evaluation of coronary artery calcium (CAC), but other applications, including assessment of coronary artery stenosis (CAS), have been reported in limited cases; however, EBCT is expensive and is not widely available.

Recent advances in CT technologies, especially multiple-row detector computed tomography (MDCT), have dramatically changed the approach to the non-invasive imaging of cardiac disease. With sub-millimeter spatial resolution (less than 0.75mm), improved temporal resolution (50-200ms), and ECG gating, the current generation of CT scanners (16-64-row detectors) makes imaging possible, and has the potential to accurately characterize the coronary tree. The purpose of this article is to provide a perspective on the developments in MDCT technology that have made non-invasive cardiac imaging with CT a reality, and compare it with conventional imaging techniques, such as CA performed under X-ray fluoroscopy guidance.

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