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70 2011


IMAGING & ONCOLOGY


datasets, which give a better chance of obtaining motion-free images of all segments of the coronary arteries and which can be used to assess function , are not the sole preserve of retrospectively ECG-gated acquisitions. They can also be acquired prospectively, potentially at lower dose33


.


Despite the encouraging downward trend in radiation dose for CTCA, there are risks at even low doses - greater for younger patients, particularly females - and we must be sure that the expected benefits of the examination outweigh the risks.


SERVICE REQUIREMENTS A 64-slice scanner with cardiac software, a dual-headed CT-injector, radiographers who understand and are familiar with cardiac CT, radiologists and/or cardiologists who have completed a Level 2 course in cardiac imaging, and appropriate sessional time for performing and reporting scans, are all essential34,35 of Cardiovascular Imaging36


. The website of the British Society is a good resource for those new to cardiac imaging and lists appropriate courses for radiographers, radiologists, and cardiologists.


Patients must, of course, be informed in advance of the details of the procedure. A nurse who can ascertain the patient’s pulse rate and blood pressure, perform an ECG, determine what medications the patient is taking, assess for contra-indications to beta- blockers, nitroglycerin, and contrast, and administer beta-blockers if necessary, can be enormously helpful.


Good communication between referrers and those performing the examinations ensures that referrers are aware of the strengths and limitations of the technique and that they refer appropriately. It also ensures that the imaging team receives valuable feedback. Historically, communication between cardiology and radiology departments has been limited because staff in cardiology departments have performed the imaging that is most germane for their patients, namely echocardiography and catheter angiography. With increasing numbers of patients having cardiac MRI, CT, and nuclear medicine scans, which are performed by radiographers and often reported by radiologists, there is a compelling argument for regular clinical meetings between these departments.


THE FUTURE OF CARDIAC CT ECG-gated multislice CT is now an established non-invasive technique for investigating suspected coronary artery disease and a number of other cardiac pathologies. Given the recent NICE recommendation on using CTCA for a subset of patients presenting with chest pain, we are on the threshold of new era in which cardiac CT will become a standard investigation to be provided by all CT departments in the UK. It is, however, complex and demanding. To replicate the accuracy achieved under research conditions in centres of excellence, we need to be scrupulous in patient selection, patient preparation, acquisition technique, minimisation of radiation dose, post-processing, interpretation, follow-up/feedback, and all aspects of quality control.


REFERENCES 1. Mark D B, Berman D S, Budoff M J, Carr J J, Gerber T C, Hecht H S, Hlatky M A, Hodgson J M, Lauer M S, Miller J M, Morin R L, Mukherjee D, Poon M, Rubin G D, Schwartz R S. ACCF/ACR/AHA/NASCI/SAIP/SCAI/ SCCT 2010 expert consensus document on coronary computed tomographic angiography: a report of the American College of Cardiology Foundation Task Force on Expert Consensus Documents. Catheter Cardiovasc Interv. 2010 Aug 1; 76(2):E1-42.


2. Taylor A J, Cerqueira M, Hodgson J M, Mark D, Min J, O'Gara P, Rubin G D. ACCF/ SCCT/ACR/AHA/ASE/ASNC/NASCI/SCAI/ SCMR 2010 Appropriate Use Criteria for Cardiac Computed Tomography A Report of the American College of Cardiology Foundation Appropriate Use Criteria Task Force, the Society of Cardiovascular Computed Tomography, the American College of Radiology, the American Heart Association, the American Society of Echocardiography, the American Society of Nuclear Cardiology, the North American Society for Cardiovascular Imaging, the Society for Cardiovascular Angiography and Interventions, and the Society for Cardiovascular Magnetic Resonance. J Am Coll Cardiol. 2010 Nov 23; 56(22):1864-94.


3. N, Cotterell M, Hill D, Adams P, Ashcroft J, Clark L, Coulden R, Hemingway H, James C, Jarman H, Kendall J, Lewis P, Patel K, Smeeth L, Taylor J. Chest pain of recent


onset: assessment and diagnosis of recent onset chest pain or discomfort of suspected cardiac origin. Cooper A, Calvert N, Skinner J, Sawyer L, Sparrow, K, Timmis A, Turnbull. March 2010 Available at http://www.nice. org.uk/CG95


4. Agatston A S, Janowitz W R, Hildner F J, Zusmer N R, Viamonte M, Detrano R. Quantification of coronary artery calcium using ultrafast computed tomography. J Am Coll Cardiol 1990; 15:827-832


5. Ohnesorge B, Flohr T, Becker C, Kopp A F, Schoepf U J, Baum U, Knez A, Klingenbeck- Regn K, Reiser M F. Radiology. Cardiac imaging by means of electrocardiographically gated multisection spiral CT: initial experience. 2000 Nov; 217(2):564-71.


6. Dodge J T Jr, Brown B G, Bolson E L, Dodge H T. Lumen diameter of normal human coronary arteries. Influence of age, sex, anatomic variation, and left ventricular hypertrophy or dilation. Circulation 1992; 86:232–46.


7. Herzog C, Nguyen S A, Savino G., et al. Does two-segment image reconstruction at 64-section CT coronary angiography improve image quality and diagnostic accuracy? Radiology 2007; 244:121-129.


8. Kroft L J, de Roos A, Geleijns J. Artifacts in ECG-synchronized MDCT coronary angiography. AJR Am J Roentgenol. 2007 Sep; 189(3):581-91.


9. Wang Y, Vidan E, Bergman G W. Cardiac


Further developments in CT technology are likely to bring better temporal and spatial resolution, reducing artefacts, and improving anatomical diagnostic accuracy. The most interesting and exciting development of cardiac CT, however, is its potential for functional imaging, particularly myocardial perfusion and delayed enhancement imaging in the setting of CAD26


. If it fulfils its promise in this arena, it will be the only


test in the cardiologists’ armamentarium which can demonstrate both coronary artery disease and its functional significance in a single convenient ‘one-stop’ assessment. This combined intelligence is essential for appropriate patient management and will make cardiac CT an even more cost-effective, useful and sought-after investigation.


John J Curtin is a consultant radiologist at the Norfolk and Norwich University Hospital.


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