Noninvasive assessment of myocardial viability in a small animal model: Comparison of MRI, SPECT, and PET

Abstract

Acute myocardial infarction (AMI) research relies increasingly on small animal models and noninvasive imaging methods such as MRI, single-photon emission computed tomography (SPECT), and positron emission tomography (PET). However, a direct comparison among these techniques for characterization of perfusion, viability, and infarct size is lacking. Rats were studied within 18 -24 hr post AMI by MRI (4.7 T) and subsequently (40 -48 hr post AMI) by SPECT ( 99 Tc-MIBI) and micro-PET ( 18 FDG). A necrosis-specific MRI contrast agent was used to detect AMI, and a fast low angle shot (FLASH) sequence was used to acquire late enhancement and functional images contemporaneously. Infarcted regions showed late enhancement, whereas corresponding radionuclide images had reduced tracer uptake. MRI most accurately depicted AMI, showing the closest correlation and agreement with triphenyl tetrazolium chloride (TTC), followed by SPECT and PET. In some animals a mismatch of reduced uptake in normal myocardium and relatively increased 18

Speckle tracking imaging improves in vivo assessment of EPO-induced myocardial salvage early after ischemia-reperfusion in rats

“…As a final assessment, however, TTC staining cannot be used for longitudinal follow-up. Several noninvasive imaging techniques attempted to measure infarct size and viability in rodents: single-photon emission computed tomography (11,36), positron emission tomography (27), magnetic resonance imaging (23,32,37), and contrast echocardiography (24). These options are not only invasive in nature as they require intravenous access and deep anesthesia, but, in addition, they are not widely available.…”

Is it Feasible to Use the Commercially Available Autoquantitation Software for the Evaluation of Myocardial Viability on Small-Animal Cardiac F-18 FDG PET Scan?

“…This method has been well known as the absolute threshold method [21,22]. MI size was defined as the percentage ratio of the area that was under the threshold value to the entire polar map area.…”

“…MI size was defined as the percentage ratio of the area that was under the threshold value to the entire polar map area. In previous studies, various absolute threshold values had been proposed (50-72 %) [21,22]. Higuchi et al [23] and Thomas et al [21] reported that decreased correlation coefficient was observed when took much lower threshold value in rodent model compared with the human study.…”

“…In previous studies, various absolute threshold values had been proposed (50-72 %) [21,22]. Higuchi et al [23] and Thomas et al [21] reported that decreased correlation coefficient was observed when took much lower threshold value in rodent model compared with the human study. In the study of Woo et al [24], threshold value of 40 % showed the best correlation coefficient in small animal myocardial infarction PET imaging.…”

A good beginning with an uncertain future

“…Several investigations have shown that this is possible indeed with dedicated radionuclide imaging devices and radiotracers of myocardial blood flow and substrate metabolism. [1][2][3][4][5][6] Non-invasively observed regional radiotracer tissue concentrations were found to be closely correlated with those measured postmortem by tissue counting. Image-derived sizes of perfusion defects closely matched the infarct sizes determined postmortem by tissue staining techniques and thus were highly accurate.…”