CARDIOLOGY UPDATE Cardiac magnetic resonance imaging

Submitted 25 May 2003 Accepted 23 June 2003 . . . . . . . . . . . . . . . . . . . . . . . M agnetic resonance imaging (MRI) has been in clinical use for 20 years and has a major role in the fields of musculoskeletal and neurological imaging. Progress in technology has reduced scan times and improved image resolution, and the modality now can offer static and dynamic cardiac and vascular imaging on a wide scale. Cardiac MRI should be regarded as complementary to other imaging modalities. The availability of transthoracic and transoesophageal echocardiography, their portability, and the experience in this field will keep them as first line investigations for many years. Cardiac MRI cannot measure coronary artery calcification and has not achieved the spatial resolution of the most modern computed tomography systems. Widespread use of computed tomography and nuclear medicine for multiple follow up cardiac studies is limited by the cumulative radiation doses acquired. MRI is currently of particular value in assessing following up congenital cardiac anomalies and in visualising abnormalities of the aorta. There is a rapidly expanding role of MRI in the assessment of ischaemic heart disease with myocardial perfusion and scar imaging. The strength of magnet required to achieve morphological cardiac imaging is similar to that used for other applications and many of the modern systems will have pre-loaded software able to perform some static and cine imaging. This technology is available from dedicated research centres through to the district general hospital. Absolute contraindications to cardiac MRI are few but include permanent pacemakers, defibrillators, and cerebral aneurysm clips. Most prosthetic heart valves and coronary artery stents are safe, although they may produce some artefact.