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冠心病是由于冠状动脉粥样硬化引起冠状动脉循环的改变,导致冠状血流和心肌需求之间不平衡而出现心肌损害,其病理生理基础是心肌微循环状态失衡和冠状动脉血流量调节障碍[1]。心肌灌注成像(myocardial perfusion imaging,MPI)是评价心肌微循环和判断心血管疾病预后及不良事件的重要无创性检查方法[2]。冠状动脉解剖学情况和心肌灌注微循环情况相结合,对于指导缺血性心脏病患者的治疗至关重要。目前评价冠状动脉解剖学情况的主要方法是传统的冠状动脉造影(coronary angiography,CAG)或冠状动脉CT血管造影(coronary CT angiography,CCTA),评价心肌微循环灌注的主要方法为核素心肌灌注成像、磁共振心肌灌注成像等[3-4]。这些检查方法有一定的缺陷,并且都不能同时得到能够用于诊断的冠状动脉和心肌灌注图像。因此寻找一种“一站式”且能够准确得到冠状动脉管腔图像和心肌灌注图像的方法有重要的临床意义。CT灌注成像不仅可以准确地评价冠状动脉及心腔的解剖学信息,同时又能获得心肌灌注和心功能的功能学信息[5-7]。然而,传统的动态CT心肌灌注需要分次进行冠状动脉和心肌动态灌注扫描,有效射线剂量高。双源CT(dual source computed tomography)双能量(dual-energy)扫描可一次性获得冠状动脉和双能量MPI图像,“一站式”完成冠状动脉的形态学和心肌血供信息[8-11]。第二代双源CT在第一代双源CT的基础上,扩大了扫描视野,通过设置能量滤过器,纯化了能谱[12]。本研究通过建立猪急性心肌梗死模型,以组织病理学和传统CAG结果为金标准,评价第二代双源CT双能量“一站式”CCTA结合MPI检测急性心肌梗死的准确率。
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共有7只猪进行心肌梗死建模,平均体质量(29±3.8)kg(25~34 kg)。其中有2只于介入过程中死亡;2只在闭塞前降支过程中发生室速,给予利多卡因静脉推注后转复,即有5只成功建成模型(其中1只闭塞右冠状动脉远段、2只闭塞前降支中段+回旋支近段、2只闭塞前降支中段)。
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基于碘图节段分析,双能量CT心肌灌注共评价85个心肌节段,检测出45个血池缺损节段,40个正常心肌节段。以病理结果为金标准,43个节段证实为梗死区域,2个节段为假阳性,3个节段为假阴性。1号猪13节段为假阳性,14节段、16节段为假阴性;3号猪6节段为假阳性;5号猪2节段为假阴性。基于血管分布区域分析,共评价15个血管分布区域,其中9个区域检测出血池缺损区域、6个区域为正常心肌区域。以病理结果为金标准,2个区域证实为假阳性,1个区域为假阴性。双能量CT和组织病理学检出心肌梗死缺血节段部位和数量详见表 1,建模后24 h CT扫描得到的双能量心肌灌图像,检测心肌梗死的灵敏度、特异度、阳性预测值、阴性预测值(表 2),典型模型见图 1。
检查方法 心肌节段 合计 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 双能量CT碘图 2 2 1 2 2 0 4 4 4 1 4 0 4 4 4 3 4 45 组织病理学 2 2 1 2 2 2 4 4 4 1 4 0 2 4 4 4 4 46 表 1 双能量CT碘图和组织病理学检出心肌梗死缺血节段部位和数量(段)
Table 1. Segmental region and number of myocardial infarction detected by dual-energy CT and histopathology
准确率 基于节段评价
(n=85)基于区域评价
(n=15)真阳性 40 8 假阳性 2 1 真阴性 40 6 假阴性 3 0 灵敏度(95%可信区间) 93%(81%~98%) 100%(63%~100%) 特异度(95%可信区间) 95%(83%~99%) 86%(42%~97%) 阳性预测值(95%可信区间) 95%(83%~99%) 89%(52%~98%) 阴性预测值(95%可信区间) 93%(81%~98%) 100%(54%~100%) 表 2 双能量冠状动脉CT成像结合心肌灌注碘图检测心肌梗死的准确率
Table 2. Accuracy assessment for dual-energy CT Iodine map detection of myocardialinfarction
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氯化三苯基四氮唑染色正常心肌为红色,缺血心肌为白色。共检测到46个梗死节段,39个正常心肌节段。取心肌梗死中央区、周边区及正常心肌区组织进行HE染色,梗死中央区及周边区均可见广泛的细胞核溶解甚至消失。HE染色梗死区在低倍镜下可见坏死心肌灶和正常心肌灶穿插排列;在高倍镜下可见心肌细胞浆凝聚,嗜酸性变,横纹消失,细胞核外移,心肌细胞间隙水肿,部分坏死较严重的可见细胞核消失,细胞整体呈现嗜碱性颗粒状,证明成功建成急性心肌梗死模型。
图 2 建模前后冠状动脉造影和冠状动脉CT血管造影图 图中,A:造模前冠状动脉CT血管造影;B:双能量CT心肌灌注显示心肌灌注均匀,未见明显低灌注区域;C:前降支中远段、回旋支远段栓塞后的冠状动脉造影图;D:栓塞后的冠状动脉CT血管造影容积再现图。
Figure 2. Invasive angiography and coronary CT angiography before and after animal models
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5只猪控制心率后平均心率为(102±18)bpm(80~128 bpm),共显示56个冠状动脉节段。2只猪心率用艾司洛尔后仍超过100 bpm(分别为110、128 bpm),扫描后CCTA图像评分差,血管不可评价,其余3只猪的心率均控制在100 bpm以内,冠状动脉均可评价。心率≤100 bpm模型猪的冠状动脉节段图像质量均达到诊断要求,平均评分为1.1±0.4,心率 > 100 bpm的冠状动脉节段图像质量评分为3~4级,平均评分为3.9±0.3,不能用于诊断。
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单次双能量CT扫描平均DLP为(219.4±60.9)mGy·cm(172~321 mGy·cm);单次双能量CT扫描平均有效射线剂量为(3.07±0.85)mSv(2.21~4.49 mSv)。
第二代双源CT冠状动脉成像结合双能量心肌灌注评价猪急性心肌梗死的实验研究
Evaluation of combined coronary CT angiography and dual-energy myocardial perfusion imaging for detection of acute myocardial infarction via second-generation dual-source CT: an experimental study in a porcine phantom model
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摘要:
目的 通过建立猪急性心肌梗死模型,以组织病理学和冠状动脉造影(CAG)结果为金标准,评价第二代双源CT双能量“一站式”冠状动脉CT血管造影(CCTA)结合心肌灌注成像(MPI)检测急性心肌梗死的准确率。 方法 7只健康小型猪,采用导管介入冠状动脉明胶海绵栓塞方法制作急性心肌梗死模型,分别在造模前20 min、心肌梗死后即刻、心肌梗死后24 h行CAG及双能量模式CCTA和MPI。采用心肌17节段法评价心肌碘图灌注缺损。双盲法由2名放射科医师对图像进行评价,以病理和CAG结果为金标准,计算双能量CCTA结合心肌灌注碘图诊断心肌灌注缺损节段的灵敏度和特异度。 结果 5只小型猪成功建成急性心肌梗死模型。双能量碘图显示45个梗死节段和40个非梗死节段。以病理和CAG结果为金标准,基于节段分析得出灵敏度、特异度、阳性预测值、阴性预测值分别为93%、95%、95%、93%;基于血管分布区域分析,双能量CT心肌灌注检测心肌梗死的灵敏度、特异度、阳性预测值、阴性预测值分别为100%、86%、89%、100%。单次双能量扫描平均有效射线剂量为(3.07±0.85)mSv(2.21~4.49 mSv)。 结论 以病理和CAG结果为金标准,第二代双源CT双能量“一站式”CCTA结合心肌灌注碘图检测急性心肌梗死准确率较高,CCTA的图像质量好。 -
关键词:
- 心肌梗死 /
- 体层摄影术, X线计算机 /
- 心肌灌注 /
- 第二代双源CT
Abstract:Objective To evaluate the diagnostic accuracy of dual-energy "one-step"combined CT coronary angiography(CCTA) and myocardial perfusion imaging(MPI) for the detection of acute myocardial infarction via second-generation dual-source CT compared with histopathological and conventional coronary angiography(CAG) findings in a porcine phantom. Methods Seven minipigs underwent transcatheter embolization of the coronary arteries by using gelatin sponge to produce acute myocardial infarction. CAG, dual-energy CCTA, and MPI were performed 20 min before, immediately after, and 24 h following the modeling procedure, respectively. A color-coded iodine map was used to evaluate the myocardial perfusion defects on the 17-segment model. In consensus, two radiologists interpreted all iodine map imaging results from MPI and CCTA. Considering CAG and pathological staining as gold standards, the sensibility and specificity of the CCTA and iodine maps from MPI were evaluated using dual-energy CT. Results Models of acute myocardial infarction were successfully made in five minipigs. Following coronary embolization, dual-energy CT iodine maps showed 45 infarcted segments and 40 non-infarcted segments. Per-segment analysis indicated the sensitivity, specificity, positive predictive value and negative predictive value as 93%, 95%, 95% and 93%, respectively. The corresponding values obtained by per-territory analysis were 100%, 86%, 89% and 100%, with CAG and histopathological findings as reference standards. The effective radiation dose of each dual-energy scan was 3.07±0.85 mSv(2.21-4.49 mSv). Conclusions Dual-energy"one-step"combined CCTA and MPI iodine maps for the detection of acute myocardial infarction via second-generation dual-source CT showed enhanced diagnostic accuracy with CAG and histopathology as gold standards. -
表 1 双能量CT碘图和组织病理学检出心肌梗死缺血节段部位和数量(段)
Table 1. Segmental region and number of myocardial infarction detected by dual-energy CT and histopathology
检查方法 心肌节段 合计 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 双能量CT碘图 2 2 1 2 2 0 4 4 4 1 4 0 4 4 4 3 4 45 组织病理学 2 2 1 2 2 2 4 4 4 1 4 0 2 4 4 4 4 46 表 2 双能量冠状动脉CT成像结合心肌灌注碘图检测心肌梗死的准确率
Table 2. Accuracy assessment for dual-energy CT Iodine map detection of myocardialinfarction
准确率 基于节段评价
(n=85)基于区域评价
(n=15)真阳性 40 8 假阳性 2 1 真阴性 40 6 假阴性 3 0 灵敏度(95%可信区间) 93%(81%~98%) 100%(63%~100%) 特异度(95%可信区间) 95%(83%~99%) 86%(42%~97%) 阳性预测值(95%可信区间) 95%(83%~99%) 89%(52%~98%) 阴性预测值(95%可信区间) 93%(81%~98%) 100%(54%~100%) -
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