Refinements in MRI technique continue to show promise in clarifying the nature and extent of damage of myocardial infarction. Take for example teams from Munich, Germany presenting this week at ECR 2011, who have been finding ways around the problem of adapting inversion time to the individual patient when using delayed enhancement to detect tissue damage.
Merely mapping T1 values obtained with late gadolinium enhancement (LGE) on a 1.5 T Siemens MRI scanner revealed significant differences between normal and infarcted myocardium, according to a study by radiologist Kerstin Baumer, MD, and a team at the University of Munich, who used the left ventricular cavity as a reference in analyzing scans of 18 patients who showed chronic MI six months after the initial infarction. This was true whether or not the images were contrast enhanced, said Baumer.
In the nearby MRI Clinic at the Technical University of Munich, Armin Huber and his colleagues examined 19 patients with evidence of MI, comparing the data from delayed contrast images from a 1.5 T Philips scanner assessed in two different ways: using phase-sensitive inversion recovery (PSIR) and with individually adapted inversion times.
Not only does the PSIR analysis allow them to take five slices of the myocardium, rather than one, with one breath-hold, Huber reported, the determinations of infarct shape and volume were similar. The resolution on the PSIR images was clearly better, which should be an advantage for smaller lesions, he added.
Radiologists fortunate enough to have access to a 3 T MRI scanner can expect even better results from cardiac MRI, to judge from the evidence presented by Peter Bernhardt of the University Clinic in Ulm, Germany.
Radiologists there scanned 52 patients suspected of having coronary artery disease (judging from their average Framingham Risk Scores of 15) with Gd-DOTA enhanced MRI at both 1.5 T and 3 T, after assessing their condition with coronary angiography and adenosine-stress perfusion testing. The order of the different MRI tests was randomized, and readers were blinded to the results of other tests. The specificity and sensitivity of 3 T MRI were significantly better than 1.5 T at detecting stenosis in both the left anterior descending and left circumflex artery but not, curiously, in the right coronary artery.
"There's a much bigger contrast to noise ratio at 3-T," said Bernhardt, allowing a reduction in contrast medium. Studies before the experiment predicted that a 0.075 mmol/kg would produce better results at 3 T than 0.1 mmol/kg at 1.5 T, and this proved to be the case.