| Objective:11C-N-CH3-Dopamine was used to detect myocardial ischemia of different degrees,and compared with18F-BMS myocardial perfusion imaging and18F-FDG myocardial metabolism imaging.The changes of cardiac nerve with time after myocardial ischemia reperfusion and the time window of11C-N-CH3-Dopamine cardiac nerve imaging for the diagnosis of"ischemic memory"were discussed,and the cardiac nerve imaging was established as a more sensitive method for non-invasive detection of"ischemic memory".Method:Eight Bama miniature pigs,male or female,weighing 25-30kg,were selected.Balloon occlusion was performed on the distal left anterior descending branch（LAD）after the first diagonal branch.According to the time of balloon occlusion,they were divided into8min group and 15min group.Cardiac enzyme,troponin T and ECG were monitored before and after modeling in each piglet.11C-N-CH3-Dopamine,18F-FDG and18F-BMS PET/CT imaging were performed before modeling,24h,48h,72h and 1w after modeling,respectively.After the completion of the imaging,the radioactivity counts in the ischemic area and the normal area were measured,and the ratios of the two were calculated and analyzed.Results:1.Comparison of 18F-BMS,18F-FDG and 11C-N-CH3-Dopamine PET/CT myocardial imaging（1）The myocardial imaging results of18F-BMS,18F-FDG and11C-N-CH3-Dopamine PET/CT before and after modeling（24h,48h,72h and 1w）in the 8min group were as follows:there was no significant difference in the ratio of radioactivity count in the ischemic/non-ischemic area before modeling among the three imaging agents（F=0.01,P>0.05）;The variance analysis of the ratio of radioactivity count in the ischemic/non-ischemic area at each time after modeling showed that there were significant differences in the ratio of the three imaging agents in the same time period.The results of pairwise comparison(18F-BMS and18F-FDG,18F-BMS and11C-N-CH3-Dopamine,18F-FDG and11C-N-CH3-Dopamine)showed that there were significant differences in the ratio of radioactivity count in the ischemic/non-ischemic area at 24h after modeling.There was no significant difference between the ratios of18F-BMS and18F-FDG at 48h,72h and 1w after modeling,but the ratio of18F-BMS to18F-FDG was significantly different compared with11C-N-CH3-Dopamine.（2）The myocardial imaging results of18F-BMS,18F-FDG and11C-N-CH3-Dopamine PET/CT before and after modeling（24h,48h,72h and 1w）in the 15min group were as follows:there was no significant difference in the ratio of radioactivity count in the ischemic/non-ischemic area before modeling among the three imaging agents（F=0.05,P=0.96）;The variance analysis of the ratio of radioactivity count in the ischemic/non-ischemic area in each imaging period after modeling showed that there were significant differences in the ratio of the three imaging agents in the same imaging period.Further pairwise comparison results(18F-BMS and18F-FDG,18F-BMS and11C-N-CH3-Dopamine,18F-FDG and11C-N-CH3-Dopamine)showed that there was a statistically significant difference in the ratio of radioactive counts in the ischemic/non-ischemic area at 24h and 48h after modeling.At 72h and 1w after modeling,there was no significant difference between the ratios of18F-BMS and18F-FDG,but they were significantly different compared with the ratios of11C-N-CH3-Dopamine.2.PET/CT myocardial imaging with different degrees of ischemia:（1）Myocardial perfusion imaging of18F-BMS PET/CT with different degrees of ischemia:At 24h,48h,72h and 1w after modeling,no obvious abnormal18F-BMS distribution was observed in the myocardial ischemia area in the 8min and 15min groups.There was no statistically significant difference in the radioactive count ratio in the ischemic/normal area between 24h,48h,72h,1w after modeling and before modeling in the 8min and 15min groups.At 24h,48h,72h and 1w after modeling,there was no statistically significant difference between the two groups in the ratio of radioactivity counts in the ischemic/normal area.This indicated that the myocardial blood perfusion had returned to normal at 24 hours after modeling,and there was no significant difference in the rate of blood flow recovery between the two groups.（2）18F-FDG PET/CT myocardial metabolism imaging with different degrees of ischemia:In the 8min group,a sparse area of18F-FDG imaging agent uptake was observed at 24h after modeling,and the ratio of radioactivity count in the ischemic/normal area was 0.68±0.01.No abnormal imaging agent uptake sparse-defect area was observed at 48h,72h and 1w after modeling,and there is no significant difference between the corresponding radioactive count ratio in the ischemic/normal area and the before modeling,suggesting that FDG metabolism in the 8min group gradually recovered with time,and basically returned to normal at 48h after modeling.In the 15min group,a sparse area of18F-FDG imaging agent uptake was seen at24h and 48h after modeling,and the radioactive count ratios in the ischemic/normal area were0.56±0.01 and 0.64±0.03,respectively.No abnormal imaging agent uptake was observed at72h and 1w after modeling,and the corresponding ischemic/normal area radioactive count ratio was not significantly different from before modeling.It was suggested that FDG metabolism in the 15-minute group basically returned to normal at 72 hours after modeling.In the myocardial imaging at 24h and 48h after modeling,the ratio of radioactive counts in the ischemic/normal area of the 15min and 8min groups was significantly different（t=14.54,P<0.001;t=16.39,P<0.001）.And the ratio of the 15min group was less than that of the 8min group,suggesting that the ischemia of the 15min group was heavier than that of the 8min group and the metabolic recovery was slower.（3）11C-N-CH3-Dopamine PET/CT cardiac nerve imaging with different degrees of ischemia:In the 8min and 15min groups,11C-N-CH3-Dopamine PET/CT cardiac nerve imaging was performed before modeling and 24h,48h,72h and 1w after the model was modeled.Sparse-defect area of imaging agent uptake was obvious in both groups.There was no statistically significant difference in the radioactive count ratio in the ischemic/normal area between 24h,48h,72h,1w after modeling and before modeling in the 8min and 15min groups.It was suggested that the time window of11C-N-CH3-Dopamine cardiac nerve imaging to diagnose previous myocardial ischemia can be as long as 1w in the 8min group and 15min group.The difference in the ratio of radioactivity counts in the ischemic/normal area after modeling（24h,48h,72h,1w）between the two groups was statistically significant.And the ratio of the 15min group was less than that of the 8min group,suggesting that in the11C-N-CH3-Dopamine cardiac nerve imaging,the ischemia of the 15min group was heavier than that of the 8min group.Conclusion:1.18F-BMS,18F-FDG and 11C-N-CH3-Dopamine had different time window for tissue damage to return to normal after transient myocardial ischemia,namely,the time window for ischemic memory was different.11C-N-CH3-Dopamine had the longest time window,18F-FDG was the second,and 18F-BMS had the shortest time window.Therefore,the degree of cardiac nerve injury is more serious than that of metabolism and perfusion injury,so11C-N-CH3-Dopamine cardiac nerve imaging is more sensitive to diagnose myocardial"ischemic memory".2.After transient myocardial ischemia reperfusion,different degrees of ischemia（8min and 15min）require different time for tissue damage to return to normal.The time window of"ischemic memory"in the 15min group is longer than that in the 8min group,and the recovery of metabolism and nerve injury of the ischemic myocardium is slower. |
PDF Full Text Request