Cardiac MR research builds on modality's inherent strengths

The 2006 Society for Cardiovascular Magnetic Resonance meeting showed that the most productive areas of cardiac MR research are those that exploit the modality's inherent strengths.

Most cardiac imagers agree that cardiac CT will become the modality of choice for coronary artery imaging. But the coronary arteries are only one feature of cardiac anatomy, and this approach excludes many aspects of coronary artery disease. Events leading to myocardial infarction may begin in a vessel wall, but they ultimately end in the heart muscle, causing physiologic changes that CMR measures extremely well.

"We are moving full speed ahead in areas where CMR has strength," said Dr. Christopher Kramer, SCMR scientific program director. "MR has advantages whether it is imaging of ventricular function, perfusion, delayed enhancement for viability and identifying at-risk patients, or identifying forms of cardiomyopathies and vascular imaging."

Research presented at this year's meeting in January confirmed CMR's prominence for all aspects of cardiovascular imaging involving infants and children or serial imaging that would otherwise involve repeated exposure to ionizing radiation. CMR has long been the instrument of choice for imaging the repair of the tetralogy of Fallot. Research presented at the meeting in Miami revealed dobutamine MR's ability to show the relationship among end-diastolic forward flow, pulmonary regurgitation, and exercise following surgical tetralogy of Fallot repair.

For the evaluation of myocardial infarction, research established that the extent of microvascular obstruction measured with delayed-enhancement MR is more accurate than other functional indicators for predicting future adverse events. Studies showed that DE-MRI is better than stress SPECT for diagnosing significant coronary artery disease, and DE-MRI combined with stress-rest perfusion MRI is more accurate than either test performed alone.

Delayed enhancement is not just for infarctions. Its value for diagnosing and assessing cardiomyopathies is improving as well. Research presented at this year's meeting underscored the importance of fibrosis in assessing the risk of sudden death from dilated cardiomyopathy. By measuring delayed-enhancement signal intensity, clinicians can also interrogate the internal architecture of lesions to see if islands of functioning myocytes reside among the necrotic tissue.

Additional research discussed in Miami demonstrated the value of delayed enhancement for follow-up evaluation of pulmonary artery radiofrequency ablation. The feasibility of real-time 3D catheter tracking was established with human subjects. Black blood MR angiography measured arteriosclerotic plaque burden.

parallel benefits

The benefits of parallel imaging could be seen in excellent extended field-of-view peripheral vascular angiography performed by researchers at the University of California, Los Angeles using an investigational 32-channel extremity coil on a 1.5T scanner. Presenters at the SCMR meeting reported progress in extracting the benefits of higher signal to noise from 3T CMR, and research reported in Miami may lead to less restrictive policies for MRI of patients equipped with pacemakers or implantable cardioverter defibrillators.

These and other discoveries illustrate why the SCMR annual meeting is considered the premier scientific event for cardiovascular MRI.

This special section was compiled by James Brice, senior editor of Diagnostic Imaging.