ReviewMulti-detector row computed tomography: imaging the coronary arteries
Introduction
Coronary artery disease continues to be one of the leading causes of morbidity and mortality in England and Wales; 108,000 deaths from coronary disease were recorded in the year 2000. More than 41,000 of these deaths took place under the age of 75 years. The current prevalence of angina is over 2 million in the UK,1 about 300,000 people experience a myocardial infarction each year and coronary disease accounts for about 3% of all hospital admissions in England.2
Following other non-invasive diagnostic procedures, such as exercise-ECG testing, conventional invasive catheter coronary angiography currently provides the standard of reference for definitive diagnosis.3, 4, 5 Its advantages are high spatial (∼0.15 mm) and temporal resolution and the options of performing percutaneous angioplasty or stent insertion on the same occasion. However, many of these examinations do not lead to revascularization therapy; up to 25% of subjects in the UK are found to have normal coronary arteries,6 and 66% of subjects in the USA3 undergo invasive angiography for the presence and assessment of disease severity alone. In order to prevent unnecessary invasive tests, a reliable and reproducible non-invasive diagnostic test for the detection and grading of coronary artery stenosis is highly desirable. The most promising method at present is multi-detector row computed tomographic (MDCT) coronary angiography.7, 8, 9
Imaging the coronary arteries is a technical challenge, owing to continuous cardiac motion and the small luminal diameter of the vessels. High-performance temporal resolution (time needed to acquire one image) and spatial resolution (ability to distinguish between adjacent structures) is therefore required. There have been recent technical advances which have led to improvements in temporal resolution, fast ECG-gated scanning10 and reconstruction techniques for motion-free cardiac imaging, with improvements in spatial resolution for sub-millimetre imaging and reduction in radiation exposure times, resulting in the generation of images without artefacts.
Cardiac imaging with MDCT acquired with a single breath hold confers additional benefits, providing information about cardiac morphology, volume assessment and ejection fraction.11, 12 MDCT cardiac perfusion application software is under ongoing development for potential use in the clinical setting.13, 14
The ultimate aim of MDCT coronary angiography will be to complement conventional diagnostic invasive coronary angiography15, 16 and other existing imaging methods, avoiding negative invasive coronary angiograms and assisting the planning of any revascularization procedure.
MRI also can assess cardiac morphology, function, perfusion and viability with low temporal resolutions (20 to 50 ms). However, the 3D spatial resolution achievable is marginal for coronary arterial imaging and is therefore not yet reliable, thus limiting this particular application.17
We present this update review of cardiac MDCT, with particular emphasis on coronary artery imaging. Brief historical perspectives and present and future uses are discussed with reference to current clinical experience in our own institution.
Section snippets
Pathology of coronary artery disease
When using and interpreting cardiac MDCT coronary angiography, it is useful to have some understanding of the pathological processes involved in the development of atherosclerosis.
Angina is caused by coronary artery atherosclerosis leading to luminal stenosis. A mature fibrolipid plaque has a core of extracellular lipid, surrounded by smooth muscle cells, and is separated from the arterial lumen by a fibrous cap.18, 19 At the edge of the plaque is a vulnerable zone that is often the site of
Overview of cardiac CT evolution
Coronary arterial CT imaging has been a challenging area of research because of limitations in scanner speed, volume coverage and temporal resolution (Table 1).
Even higher isotropic spatial resolution is now possible with the next generation of CT technology, i.e. the 32-channel and 64-channel MDCT (0.35 mm collimation and 340 ms rotation times). The 64-MDCT is currently being developed, with recent results indicating visual clarity of up to fifth-order coronary arterial branches.22 This should
Technical and practical aspects of cardiac CT
A number of factors must be optimized in order to achieve the highest quality images.
Clinical applications of cardiac CT
The usefulness of cardiac CT is under continual evolution from research to clinical setting. Ultimately, the aim is to establish MDCT as a complementary adjunct to conventional established techniques.
Other clinical uses and future considerations
Coronary artery anomalies are being described with greater frequency because of the increased use of coronary angiography. Myocardial bridging and ectopic aortic origins of the coronary arteries are generally asymptomatic, unless the course is altered to pass between the aorta and the right ventricular outflow tract (Fig. 11) or via a prolonged intramuscular course, both of which may result in vessel impingement and ischaemic symptoms. Anomalous coronary arterial origins from the pulmonary
Conclusion
With the advent and increasing clinical use of 16-detector row machines, and now with the imminent clinical emergence of 64-channel and flat-plate technology, the improvements in spatial and temporal resolution, sophisticated ECG-gating and post-processing software algorithms are allowing motion-free, fast, accurate, detailed, contrast-enhanced cardiac imaging that not only rivals the accuracy of traditional invasive and non-invasive diagnostic techniques, but also provides additional
Acknowledgements
The Royal College of Radiologists Research Fellowship Award 2004/5 funds N. Manghat to study the clinical applications of cardiac CT. Thanks are also due to General Electric Medical Systems for assistance. Figure 13, Figure 14 are used by kind permission of D. Foley. Particular thanks are extended to all the CT radiographers at Derriford Hospital for their continued enthusiasm and support.
References (58)
- et al.
Sub-second multi-slice CT: Basics and applications
Eur J Radiol
(1999) - et al.
Current developments of cardiac imaging with multi-detector row CT
Eur J Radiol
(2000) - et al.
Advances in cardiac imaging with 16-section CT systems
Acad Radiol
(2003) - et al.
The technical design and performance of ultrafast computed tomography
Radiol Clin North Am
(1994) - et al.
Multislice computed tomographic coronary angiography: Experience in a UK centre
Clin Radiol
(2003) - et al.
Multislice spiral computed tomography coronary angiography in patients with stable angina pectoris
J Am Coll Cardiol
(2004) - et al.
Noninvasive detection of coronary lesions using 16-detector multislice spiral computed tomography technology: Initial clinical results
J Am Coll Cardiol
(2004) - et al.
Non-invasive detection and evaluation of atherosclerotic plaques with multislice CT
J Am Coll Cardiol
(2001) - et al.
Isotropic half-millimeter angiography of coronary artery bypass grafts with 16-slice computed tomography
Ann Thorac Surg
(2004) - et al.
Multislice spiral computed tomography for the detection of coronary stent restenosis and patency
Int J Cardiol
(2003)
Cine coronary arteriography
Mod Concepts Cardiovasc Dis
Percutaneous selective coronary cine arteriography
JAMA
Selective coronary arteriography: A percutaneous transfemoral technique
Radiology
Diagnostic cardiac catheterisation in a hospital without on-site cardiac surgery
Heart
Performance evaluation of a multi-slice CT system
Med Phys
Detection of coronary artery stenosis by contrast-enhanced, retrospectively ECG-gated, multi-slice spiral CT
Circulation
25 years of cardiac CT imaging: Past, present and future
Herz
Multisection CT: Scanning techniques and clinical applications
RadioGraphics
Coronary microvascular functional reserve: Quantification of long term changes with electron-beam CT preliminary results in a porcine model
Radiology
Quantification evaluation of regional myocardial perfusion using fast X-ray computed tomography
Herz
Reliable noninvasive coronary angiography with fast sub-millimetre multislice spiral computed tomography
Circulation
Detection of coronary artery stenosis with thin-slice multi-detector row spiral computed tomography and multiplanar reconstruction
Circulation
Coronary arteries
Eur Radiol
Inflammation in cardiovascular disease
J R Coll Physicians Lond
A definition of advanced types of atherosclerotic lesions and a histological classification of atherosclerosis
Circulation
The pathogenesis of atherosclerosis
Nature
Our preoccupation with coronary luminology
Circulation
Cited by (25)
Diagnostic efficacy for coronary in-stent patency with parameters defined on Hounsfield CT value-spatial profile curves
2008, RadiographyCitation Excerpt :New contrivances of anti-platelet therapy for sub-acute thrombosis,1,2 material improvement for feasibility of stent delivery3,4 and radioisotope or drug eluting stents5–8 have expanded indications for coronary stenting with the result that morphological evaluation of coronary in-stent re-stenosis becomes clinically essential. MR imaging9–13 and multi-detector CT14–20 can be used in part as an alternative noninvasive coronary angiography. Both can scrutinize the given lesions at the specific coronary segments although their spatial and temporal resolution is insufficient at present for screening the entire coronary artery tree.12
Impaired left ventricular function has a detrimental effect on image quality in multi-detector row CT coronary angiography
2008, Clinical RadiologyCitation Excerpt :Exclusion criteria were NYHA class 4 heart failure, previous contrast allergy, pregnancy, significant renal impairment, and inability to breath-hold for 20 s. Patients were not excluded on the basis of body mass index (BMI), age, or cardiac dysrhythmias. CT examinations were performed on a 16-detector row MDCT machine (GE Healthcare Technologies, Waukesha, WI, USA) with a gantry rotation time of 500 ms and a collimation of 16 × 0.625 mm.7 The imaging delay was calculated from commencement of the injection of 20 ml intravenous contrast medium at 4 ml/s (Iopromide; Ultravist® 370, Schering Healthcare Ltd, West Sussex, UK) followed by a 20 ml saline chaser bolus, via an 18 G right antecubital fossa venous cannula, to the time of maximal contrast enhancement, imaging at one 2.5 mm section/s (using prospective ECG-gating) at the level of the aortic root and coronary origins (MIROI: maximum intensity region of interest; GE Healthcare Technologies).
Considerations when introducing a new cardiac MDCT service. Avoiding the pitfalls
2008, Clinical RadiologyCitation Excerpt :The ability to manipulate data remotely with cardiology and cardiothoracic colleagues is undoubtedly valuable, but the cost of workstations and networks can be prohibitive and a balance between cost and utility must be made. Reconstruction of all phases of the R–R interval will result in 2000–3000 individual trans-axial images per study.28 The axial images are often adequate to assess the absence or presence of atherosclerosis; however, for a full assessment and quantification of stenosis severity and plaque morphology further post-processing is often necessary.29
Multi-detector row CT coronary angiography in patients with cardiomyopathy - initial single-centre experience
2007, Clinical RadiologyCitation Excerpt :Consensus opinion was obtained. CT examinations were performed on a 16-detector row machine (GE Healthcare Technologies, Waukesha, WI, USA) using our previously published protocol for MDCTA with a gantry rotation time of 500 ms and a collimation of 16 × 0.625 mm.15 A subsegmental partial reconstruction algorithm using two cardiac cycles was used for all patients (pitch = 0.24).
16-Detector row computed tomographic coronary angiography in patients undergoing evaluation for aortic valve replacement: comparison with catheter angiography
2006, Clinical RadiologyCitation Excerpt :Total ASE was used to divide patients into groups: ASE ≤400, >400, ≤1000 and >1000, which were predefined as representing significant CAC of different severities. These cut-off points were used to define a “high-risk” score.17,19,23 ASE was also determined on a vessel-by-vessel basis.