^18F-FDG PET/CT显像与心脏磁共振成像对Beagle犬局部辐射后心脏损伤的诊断

目的探讨^18F-脱氧葡萄糖(FDG)PET/CT显像与心脏磁共振成像(CMR)对Beagle犬局部放射性心脏损伤(RIHD)的诊断价值。方法将24只1岁龄健康雄性Beagle犬按照随机数字表法分为对照组及照射后3、6和12个月组,每组各6只;其中各照射组左心室前壁行单次20 Gy调强放疗。对全部犬行^18F-FDG PET/CT心肌代谢显像和CMR检查,计算^18F-FDG摄取增高区平均标准摄取值(SUVmean)及面积。全部检查结束后1周处死实验犬,取心脏进行Masson染色及电子显微镜检查。采用单因素方差分析比较组间差异。结果对照组心肌^18F-FDG几乎不摄取,照射后3个月即可见犬心肌^18F-FDG摄取增加,照射后3、6和12个月组的心肌SUVmean分别为5.90±1.31、4.66±2.21和3.21±0.82,与对照组(1.13±0.21)的差异有统计学意义(F=11.81,P<0.05);照射组^18F-FDG摄取增高面积随着照射后时间延长逐渐下降(F=195.74,P<0.01)。CMR示照射后6和12个月组的心肌灌注降低、进行性纤维化加重;与对照组相比,照射后6和12个月组的舒张末期容积(EDV)和收缩末期容积(ESV)增加(F=15.479和16.908,均P<0.01),而左心室射血分数(LVEF)下降(F=63.715,P<0.01)。Masson染色发现照射后心肌纤维化进行性加重;电子显微镜检查示照射后心肌线粒体变性肿胀,线粒体数量进行性减少。结论照射后局部心肌^18F-FDG摄取增高对于RIHD的危险性有预测价值,^18F-FDG PET/CT显像能早于CMR发现RIHD。

Experimental study of^18F-FDG PET/CT imaging and cardiac MRI in diagnosis of radiation-induced myocardial injury in Beagle dogs

Objective To investigate the value of^18F-fluorodeoxyglucose(FDG)PET/CT imaging and cardiac MRI(CMR)in the diagnosis of radiation-induced heart disease(RIHD)in Beagle models.Methods Twenty-four normal male Beagle dogs(1-year old)were randomly divided into control group and irradiated groups(3-month,6-month and 12-month after radiation).The left anterior myocardium of Beagle dogs in irradiated groups was irradiated locally with a single dose of 20 Gy X-ray.Cardiac^18F-FDG PET/CT imaging and CMR were performed on all dogs,and the mean standardized uptake value(SUVmean)and the area of lesions with increased^18F-FDG uptake were obtained.After imaging examinations were finished,dogs were sacrificed and their hearts were taken out to perform Masson staining and electron microcopy.One-way analysis of variance was used for data analysis.Results There was basically no uptake in myocardium in control group.The myocardium showed increased uptake of^18F-FDG in the irradiated groups.The SUVmean of myocardium in 3-month,6-month and 12-month after radiation groups and control group were 5.90±1.31,4.66±2.21,3.21±0.82 and 1.13±0.21,respectively(F=11.81,P<0.05).The area with increased^18F-FDG uptake in the irradiated groups decreased progressively with the prolongation of irradiation time(F=195.74,P<0.01).The reduction in myocardial perfusion and myocardial fibrosis were observed by CMR early at 6-month after irradiation.Compared with the control group,the 6-month and 12-month after radiation groups had increased end diastolic volume(EDV)and end systolic volume(ESV;F=15.479 and 16.908,both P<0.01),and decreased left ventricular ejection fraction(LVEF;F=63.715,P<0.01).The progressive aggravation of myocardial fibrosis was displayed in irradiated groups by Masson staining.The mitochondria degeneration,swelling and the count reduction in irradiated groups were observed by electron microscopy.Conclusions The increased^18F-FDG uptake in the irradiated myocardium may predict the risk of RIHD.^18F-FDG PET/CT imaging can detect RIHD earlier than CMR.