Imaging Time After Gd-DTPA Injection Is Critical in Using Delayed Enhancement to Determine Infarct Size Accurately With Magnetic Resonance Imaging

Abstract

Background-In patients with acute myocardial infarction (MI), delayed enhancement is seen in MRI 5 to 7 minutes after gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) injection, and the enhancement occurs in regions that later show recovery of function. However, in a canine model of acute MI, delayed enhancement 20 to 30 minutes after injection only occurs in necrotic regions and not in surrounding, reversibly injured myocardium. The objective of the present study was to determine (1) if the size of the enhanced region varies with time after Gd-DTPA injection and (2) if and when the size of the enhanced region corresponds to the true infarct size. Methods and Results-The left coronary artery was occluded in 15 Lewis rats for 30 minutes (nϭ9) or 2 hours (nϭ6); this was followed by reperfusion. MRI scans were performed 48Ϯ2 hours after-MI. Midventricular short-axis images were obtained continuously for 40 minutes after Gd-DTPA injection (0.3 mmol/kg). The sizes of enhanced regions at each time were determined by threshold analysis and compared with triphenyltetrazolium chloride-stained sections of the excised rat heart. In all animals, the enhanced region overestimated infarct size (28Ϯ5%) immediately after the injection of Gd-DTPA, although it then gradually receded to match the size of the infarct. The time required for enhancement to accurately determine infarct size was significantly different between 2-hour infarcts (16Ϯ2 minutes) and 30-minute (26Ϯ4 minutes) infarcts (PϽ0.05). Conclusions-In reperfused acute MI, accurate determination of infarct size by delayed enhancement MRI requires imaging at specific times after Gd-DTPA injection, and this time varies with the duration of occlusion.

Imaging Time After Gd-DTPA Injection Is Critical in Using Delayed Enhancement to Determine Infarct Size Accurately With Magnetic Resonance Imaging

“…1 We found that 2 days after MI, there exists an area at the periphery of the infarct that has a highly transient T1 value. Within the first 5 to 10 minutes after gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) injection, the T1 of this region was similar to infarct, but 20 minutes after contrast injection, its T1 value was similar to normal myocardium.…”

“…The changes in size of the hyperenhanced regions observed by Oshinski et al, 1 however, were likely caused by an incorrect implementation of the MRI technique. As we have described previously, the MRI technique requires that the correct inversion time be chosen in order to "null" normal myocardium.…”

“…In a recent report, Oshinski et al 1 concluded that "accurate determination of infarct size by delayed enhancement MRI requires imaging at specific times after gadoliniumdiethylenetriamine pentaacetic acid (Gd-DTPA) injection." This conclusion was based on the observation that the size of hyperenhanced regions changed in images acquired at different times after contrast administration.…”

The role of imaging and molecular imaging in the early detection of metabolic and cardiovascular dysfunctions

“…Delayed images have to be acquired between 10 and 30 min post-injection of the contrast media. 43 A too early acquisition will overestimate the size of the myocardial infarct, 44 whereas a too late acquisition will result in poor contrast to noise ratio, due to an excessive wash out of the contrast media. It is important to remember that not only will the time post-injection influence the size of the myocardial infarct, but also the type of MR sequences used.…”

Improved delayed enhanced myocardial imaging with T2‐Prep inversion recovery magnetization preparation

“…Most MR protocols utilize a T 1 -weighted inversion-recovery (IR) prepared fast gradient echo (GRE) segmented k-space acquisition with imaging performed 10 -20 minutes after the intravenous administration of an extracellular gadolinium (Gd)-based contrast agent (5). With this approach, the optimal inversion time (TI) is adapted to suppress signal from normal myocardium (6,7), while the infarcted tissue appears hyperintense (bright) because of the delayed uptake and retention of Gd-based contrast media. DE imaging exhibits excellent contrast between infarcted and normal myocardium.…”