Experimental study on 13N-NH3 and 99MTc-MIBI myocardial perfusion imaging in rabbits with subacute myocardial infarction of ischemic reperfusion

Purpose: To explore the relationship between 13N-NH3 and 99mTc-MIBI myocardial perfusion imaging in rabbits with subacute myocardial infarction of ischemic reperfusion. Methods: Eight male New Zealand White rabbits of which left anterior descending (LAD) coronary arteries were completely occluded for 45 min followed by 7-10 d reperfusion. One week later, the rabbits after an overnight fast were anaesthetized with sodium pentobarbital (30 mg/kg), and LAD arteries were religated for 45 min followed by 2 h reperfusion. Then the animals were positioned on the LS-PET/CT (4 row spirals CT, Discovery GE. US) table. Myocardial blood flows were obtained with 148 MBq 13N-NH3 administered via a marginal ear vein over 20 s. According to PET imaging procedure, PET/CT acquisition of dynamic scans began 5 min after injection and was accomplished within 10 min. Two hours after PET imaging the rabbits were injected with 148 MBq 99mTc-MIBI via a marginal ear vein, 30 min later myocardial perfusion imaging was performed under a single-photon emission computed tomography (SPECT). PET imaging ZOOM value was generally amplified 6 times while that of SPECT was 3 times. Tomographic images along the vertical long, horizontal long and short axes were created. Tomographic reconstruction was then performed by dividing the PET and SPECT image of the LV on a polar map into 9 segments for semi- quantitative analysis. The changes of infarct size were determined by triphenyl tetrazolium chloride (TTC) staining. The ultra-structural damage of myocardial cells in infarct and periphery areas were observed under transmission electron microscope. Results: Infarct size (24.2±1.9)% of LV mass by TTC staining, while (23.7±2.3)% vs. (20.5± 2.5)% (P < 0.001) by 99mTc-MIBI Hawkeye-SPECT and 13N-NH3 PET/CT respectively. Serious myocardial cell damages including myocardial cell denaturalization, texture, and karyolysis in infracted area and myocardial cells swelling in the periphery of infracted area was observed under the transmission electron microscope. Conclusion: Compared with 99mTc-MIBI Hawkeye SPECT, 13N-NH3 perfusion under Discovery LS-PET/CT imaging could more accurately assess infarct size. (authors)