MR Imaging of Double-Contrast Enhanced Porcine Myocardial Infarction

Abstract

MR imaging was performed to investigate whether Gd-DTPA-BMA-induced contrast enhancement of myocardial infarction is counteracted by Dy-DTPA-BMA. Myocardial infarction was induced in 5 pigs. Microdialysate probes were inserted in ischemic and nonischemic myocardium. Gd-DTPA-BMA (0.3 mmol/kg b.w.) and Dy-DTPA-BMA (1.0 mmol/kg b.w.) were administered i.v. 4 hours post occlusion. The microdialysate was collected every 10 min and measured for Gd and Dy using inductively coupled plasma atomic emission spectrometry. The pigs were sacrificed 2 hours after administration of contrast media. The concentration of both contrast agents was 3 times higher in infarcted myocardium than in nonischemic myocardium. The infarctions displayed high signal intensity in spin-echo sequences ex vivo. This lack of detectable susceptibility effects from Dy may be caused by loss of cell membrane integrity in infarcted tissue as shown by our microdialysate and biopsy data.

MR Imaging of Gadolinium-DTPA-BMA-Enhanced Reperfused and Nonreperfused Porcine Myocardial Infarction

“…The reperfused infarctions in the current study contained a 3-fold higher concentration of Gd than did 6-h-old nonreperfused infarctions (mean 0.90, SD 0.16 mmol/kg d.w.), 2 h after Gd injection in a previous study (16). These differences in behavior of contrast media in reperfused and nonreperfused infarctions are believed to be caused by the rapid delivery of contrast medium, with extravasation due to capillary damage and reactive hyperemia during the early stage of reperfusion, compared with a slow diffusion of the contrast agent into the infarction in the absence of reperfusion.…”

The contributory role of interstitial water in Gd‐DTPA‐enhanced MRI in myocardial infarction

“…Previous investigations using microdialysis clearly established the difference between the tissue concentration of Gd-DTPA-bismethylamide and its extracellular concentration in an occlusive pig infarction model (18). Since loss of cell membrane integrity could frequently occur in ischemically damaged myocardium (13), intracellular accumulation of Gd-DTPA might also be one of the mechanisms of Gd-enhancement in reperfused myocardial infarction.…”

“…The tissue Gd-DTPA concentration was measured using inductively coupled plasma (ICP) emission spectrometry (15,17,18,(20)(21)(22). The heart was excised, and the atrioventricular connective tissue and apical part were removed.…”

“…Understanding the mechanisms of Gd-DTPA enhancement is therefore essential to the interpretation of these images. The regional concentration of Gd-DTPA has been reported to be one of the mechanisms of enhancement in phantom or in vivo studies on tumor tissues (15,16) and in reperfused myocardial infarction [17,18]. The question of whether the tissue concentration of Gd-DTPA in the reperfused and nonreperfused myocardial infarction is related to tissue water content, however, remains unanswered.…”

Effect of Gd‐DTPA‐BMA on choline signals of HT29 tumors detected by in vivo 1H MRS

“…Nevertheless, our data are consistent with uptake of contrast agent by tumor cells, with a gradient of contrast agent concentration from vascular to extra-to intracellular spaces, but with complexity in the mechanisms that allow distribution of the contrast agent into the various tissue compartments. Additional evidence that contrast agents may enter the intracellular space was shown in a study of myocardial infarction with both Gd-and Dy-based contrast agents, where it was observed that susceptibility effects due to contrast agent compartmentation were lower than expected, suggesting distribution of the agent both intra-and extracellularly due to loss of cell membrane integrity (35). It is plausible that some tumor cells may also be in a stage of severe hypoxia with membrane damage prior to necrosis, but still with measurable levels of choline.…”