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Diagnostics and Imaging
Multislice Computed Tomography Coronary Angiography
a report by
PJ de Feyter, N Mollet and Koen Nieman
Erasmus Medical Centre, Rotterdam
In vivo visualisation of the coronary arteries was first introduced by de Mason which are combined to form one image reconstruction. However, this
Sones in the 1950s. Selective invasive coronary angiography (CA) has technique is less robust and requires a very stable heart rate.
significantly increased our understanding and management of coronary
atherosclerosis and has precisely delineated coronary stenoses, which was a A high spatial resolution is necessary to allow assessment of small
prerequisite for the development of coronary revascularisation techniques. coronary artery details, such as severity of stenosis or detection of often
However, it was almost 10 years before the first bypass operation was small non-obstructive plaques. The spatial resolution of current CT
performed by Favoralo in the late 1960s, and another 10 years before scanners in a phantom setting is ~0.4mm, but in clinical CT imaging
percutaneous transluminal CA (PTCA) was performed by Grüntzig in the late is estimated to be 0.6–0.7mm. A higher spatial resolution decreases
1970s. Today, invasive CA is still the cornerstone imaging modality for partial volume effects, which allows improved delineation of, for instance,
clinical decision-making in patients with suspected coronary artery disease in-stent restenosis or cases of calcified lesions, and so minimises
(CAD), and it also serves as an indispensable roadmap for percutaneous overestimation of the stenosis severity.
coronary intervention (PCI). Over the past 15 years substantial advances have
been made in non-invasive coronary imaging, initially with the introduction Computed Tomography Coronary Angiography –
of magnetic resonance (MR) CA, which more recently has been superseded Contrast Agent
by the implementation of multislice CT-CA.
1,2
CT coronary imaging requires intravenous administration of iodinated
contrast medium. Current 64-slice CT scanner protocols recommend using
Multislice Computed Tomography 80–100ml of contrast medium injection at a rate of 4–6ml/second;
Coronary Angiography – Basics
3–8
therefore, CT-CA is indicated only for patients with normal renal function.
Computed Tomography Coronary Angiography – Computed Tomography Coronary Angiography –
Temporal and Spatial Resolution Radiation Exposure
A high temporal resolution is essential for the depiction of the coronary CT-CA is associated with radiation exposure and inherent lifetime
arteries, mainly because of the rapid motion of the coronary arteries. The attributable risk of fatal cancer. The radiation dose for coronary CT is usually
motion velocity of the left anterior descending (LAD) is 22.4±4.0mm/second, given as the effective dose (E) expressed in SI units of milli-Sievert (mSv).
of the left circumflex artery (LC
x
) 48.4±15mm/second and of the right E represents a rough estimate of the biological risk of partial body exposure
coronary artery (RCA) 69.5±22.5mm/second.
9,10
It is estimated that a (as occurs in CT-CA) relative to an equivalent whole-body radiation
temporal resolution of 19–75ms is desirable to capture motion-free exposure. Recent clinical studies revealed that 64-slice CT-CA was associated
coronary images. with an effective dose ranging from 13 to 15mSv for men and from 18 to
21mSv for women. This is considerably higher than the effective dose of
The temporal resolution of CT scanners used for the visualisation of coronary
arteries is determined by the rotation speed of the gantry around the
PJ de Feyter is a Professor of Non-invasive Cardiac Imaging
patient. As the coronary images are reconstructed from data acquired from
at the Erasmus Medical Centre in Rotterdam, where he has
a 180º gantry rotation, the temporal resolution is equal to half the gantry served since 1983. His core interests include invasive and
rotation speed. Current-generation 64-slice or dual-source (DS) CT scanners
non-invasive coronary diagnostic procedures and percutaneous
coronary interventions. Professor de Feyter has authored or
still have limited temporal resolution, ranging from 83 to 165ms, which may
co-authored over 450 articles in peer-reviewed journals and over
cause image blurring (motion artefacts), particularly during higher heart
55 book chapters, and has edited seven cardiovascular books.
He received his cardiology training in the Cardiology Department
rates (<70bpm). To decrease the likelihood of the creation of unsharp
of the Free University, Amsterdam.
images, the coronary images are usually reconstructed from data acquired
E:
p.j.defeyter@erasmusmc.nl
during the relatively motion-free diastolic phase of the heart cycle. During
lower heart rates (<65bpm), this relatively motion-free period increases and Koen Nieman is a member of the cardiology staff at the
thus the likelihood of obtaining sharp images increases. Therefore,
Thoraxcenter at the Erasmus Medical Centre in Rotterdam,
with a particular interest in non-invasive cardiovascular
administration of B-receptor blocking agents 60–90 minutes before CT
imaging and acute cardiac care. He has authored or
scanning is recommended to reduce the heart rate to less than 65bpm to
co-authored over 75 papers in peer-reviewed journals and over
15 book chapters. Dr Nieman received his MD in 1998 from
prolong the rest period in the diastolic phase. To further reduce motion
the University of Nijmegen and, after completing a research
artefacts a segmented reconstruction mode is used, which improves the fellowship in cardiac computed tomography, continued his
nominal temporal resolution by a factor of two to three. Segmented
cardiology training at the Erasmus Medical Centre.
reconstruction selects data acquired during two or more cardiac cycles,
© TOUCH BRIEFINGS 2008 21
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