Delayed-enhancement MRI earned the modality an essential role in myocardial assessments. Now it is showing promise for measuring intra-arterial inflammation in coronary artery disease and maybe systemic arteriosclerosis as well.
These possibilities came to light Wednesday in a study prepared by Dr. Tareq Ibrahim and presented by his mentor, Dr. René Michael Botnar, of the Technical University of Munich in Germany.
Ibrahim found that DE-MRI tracked a significant decrease in coronary artery uptake in the two months after myocardial infarction and stenting. The decline most likely corresponds with a decline in inflammation and a related decrease of C-reactive protein within the affected coronary artery segments in the aftermath of the event, Botnar said.
The comparison between 10 patients following acute MI and 17 patients with known stable CAD also demonstrated that aortic vessel wall enhancement correlates with CAD, although it is independent from acute and unstable CAD. DE-MRI found that aortic hyperenhancement decreased between imaging performed seven days after MI and repeat imaging two months later. The finding suggests that in addition to declining inflammation in the coronary arteries after acute MI, overall systemic inflammation goes down as well, Botnar said.
The imaging protocol involved an injection of gadolinium five minutes before scanning. The right coronary, left anterior descending, and right circumflex coronary arteries were scanned with a spatial resolution of 1.25 mm. The in-plane slice thickness was 3 mm. Coronary angiography was performed with a 3D steady-state free precession (SSFP) sequence and T2-weighted fat saturation. Coronary delayed-enhancement imaging was performed on inversion recovery 3D gradient.
Results were probably influenced by the 10-year age difference between the MI patients, whose average age was 56, and the chronic CAD patients, who averaged 66, Botnar said in an interview. Because the MI patients were younger, they probably have a lighter overall plaque load, and their atherosclerotic plaques are likely less fibrous than the older controls.
More work is needed to boost the imaging protocol's efficacy. Its sensitivity, using receiver operating characteristic (ROC) analysis, was 73%. The specificity was 79%. With improvements, the technique could monitor inflammation during clinical trials of drugs designed to control inflammation. MRI enhanced with iron oxides also show promise because they are more specific than gadolinium for inflammation and macrophage infiltration.
"This is a first step toward understanding these processes," Botnar said.
For more information, examine the following from the Diagnostic Imaging abstracts:
MRI demonstrates heart morphology and function
Hearts leap as molecular cardiovascular imaging edges forward
