Imaging
Multidetector-row Computed Tomography in the Assessment of Coronary Artery Disease – New Techniques and Insights
Andreas H Mahnken Department of Diagnostic and Interventional Radiology, RWTH Aachen University
Abstract
Over the last decade, cardiac computed tomography (CT) technology has experienced revolutionary changes and gained broad clinical acceptance in the work-up of patients suffering from coronary artery disease (CAD). Since cardiac multidetector-row CT (MDCT) was introduced in 1998, acquisition time, number of detector rows and spatial and temporal resolution have improved tremendously. Current developments in cardiac CT are focusing on low-dose cardiac scanning at ultra-high temporal resolution. Technically, there are two major approaches to achieving these goals: rapid data acquisition using dual-source CT scanners with high temporal resolution or volumetric data acquisition with 256/320-slice CT scanners. While each approach has specific advantages and disadvantages, both technologies foster the extension of cardiac MDCT beyond morphological imaging towards the functional assessment of CAD. This article examines current trends in the development of cardiac MDCT.
Keywords Heart, computed tomography, coronary artery disease, temporal resolution, radiation dose, perfusion
Disclosure: The author has no conflicts of interest to declare. Received: 13 April 2010 Accepted: 8 May 2010 Citation: European Cardiology, 2010;6(2):43–7 Correspondence: Andreas H Mahnken, Department of Diagnostic and Interventional Radiology, RWTH Aachen University, University Hospital Pauwelsstrasse 30, D-52074 Aachen, Germany. E:
mahnken@rad.rwth-aachen.de
Over the last few decades, the rapid development of cardiac computed tomography (CT) has been unequalled by any other imaging technique. The driving forces behind cardiac multidetector-row CT (MDCT) are the enormous socioeconomic relevance of coronary artery disease (CAD) and the need for comprehensive, reliable and reproducible diagnostic tests that overcome the morbidity and mortality of cardiac catheter angiography, which currently is considered the standard of reference in the assessment of CAD.
Various non-invasive imaging techniques were evaluated for assessing CAD. Some techniques such as single-photon-emission computed tomography (SPECT) focused on the assessment of myocardial perfusion, while other techniques concentrated on morphological imaging of the coronary arteries. Magnetic resonance imaging (MRI) was established as the gold standard for the non-invasive work-up of CAD. However, it failed to provide sufficient image quality for assessing the coronary arteries compared with CT.1
Moreover, its
ability to evaluate myocardial perfusion, viability and ventricular function is challenged by MDCT, which also proved capable of functional cardiac imaging.2
Currently, a variety of factors are
converging, potentially making coronary CT angiography a cornerstone in the management of CAD. Rapidly evolving MDCT technology is only one among these factors with a critical influence on the clinical implementation of cardiac CT.
History of Cardiac Computed Tomography Cardiac CT was introduced at the same time that whole-body CT scanners became available. In 1977, only a few years after the
© TOUCH BRIEFINGS 2010
introduction of CT in routine clinical practice, two methods of cardiac CT imaging were laid out: conventional CT using whole-body CT scanners3
and ultrafast CT, better known as electron-beam CT (EBCT).4 After an intense evaluation of both techniques, EBCT was considered the technique of choice for cardiac CT imaging. EBCT had a role in non-invasive cardiac imaging as a technique for coronary artery calcium scoring. With its high temporal resolution of 100ms, it was also well-suited for functional imaging. Although coronary imaging was also feasible with EBCT,5
it did not become a clinically accepted
technique because of its limited spatial resolution. Despite the astonishing capabilities of cardiac EBCT imaging and the large numbers of patients who underwent coronary calcium scoring, cardiac EBCT imaging remained a niche technique.
Driven by the introduction of MDCT scanners, cardiac CT experienced a rapid rise from a niche application to a relevant mainstream technology. Starting in 1998, MDCT scanners became ubiquitously available within only a few years, providing a global infrastructure for large-volume cardiac CT imaging. The first generation of four-slice CT scanners enabled electrocardiography (ECG)-synchronised imaging of the heart with subsecond temporal resolution and a spatial resolution of about 1mm.6
Within the first
year after its introduction, MDCT was shown to be capable of coronary calcium scoring and coronary CT angiography.
While four-slice CT provided a high sensitivity and specificity for the detection of coronary artery stenoses, there was a relevant proportion of up to 43% of coronary segments that could not be evaluated due to
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