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冠状动脉CT血管造影(computed tomography angiography, CTA)已发展成为一种应用广泛、无创性的影像学检查工具,可诊断冠状动脉管腔狭窄且准确率高。尽管冠状动脉CTA评估冠状动脉狭窄程度有一定优势,但它不能确定冠状动脉狭窄与血流动力学的相关性[1]。心肌灌注成像(myocardial perfusion imaging,MPI)提供了冠状动脉狭窄血流动力学的信息。目前临床可进行MPI检查的设备有SPECT、超声心动图、MRI和PET。SPECT的应用较常见,但因其空间分辨率低和软组织衰减伪影降低了诊断的准确率[2]。双源CT双能量MPI的优势在于可“一站式”获得冠状动脉狭窄的信息和心肌灌注的功能学信息。
CT心肌灌注的直接评价技术可分为静态CT-MPI和动态CT-MPI[3]。由于静态CT-MPI是早期心肌衰减一个快照,其评估的是心肌内的碘分布而不是血流灌注情况,所以又称为静态心肌血池成像,其可以准确评估心肌内的碘分布。在早期,单源CT的静态CT-MPI是基于CT值的衰减来定义心肌的碘分布,诊断准确率低。双源CT双能量模式的采集法通过心肌内碘分布图提供了对心肌内碘的直接定量评估,进而能够评估心肌供血情况[4-5]。
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双源CT双能量MPI自提出以来一直是各国专家研究的热点,分别以SPECT、有创性冠状动脉造影及MRI-MPI为标准,进行双能量MPI准确率的研究。
应用双源CT对冠心病患者的冠状动脉狭窄情况和心肌灌注情况进行评价,并与冠状动脉造影以及SPECT的MPI进行比较,研究结果表明,其检测心肌缺血具有较高的准确率[4]。2010年,Zhang等[9]进行动物实验并以组织病理学为参考标准,结果证实心肌双源CT双能量成像显示每节段心肌梗死具有较高的灵敏度和特异度。使用双源CT双能量进行腺苷负荷心肌灌注扫描时,正常冠状动脉血流量明显增加,而病变区冠状动脉血流量不能相应增加或减少,使得静息状态下显像正常的病变冠状动脉血流供应区得以显示。2011年,Ko等[10]已证实,腺苷负荷双源CT双能量可以识别冠心病患者心肌应激诱发的心肌缺血。有学者认为,腺苷负荷CT双能量心肌血池成像检测心肌缺血的灵敏度和特异度都较好,但进一步要克服的问题是减少伪影并提高诊断的灵敏度[11]。另外,通过腺苷负荷双源CT双能量碘图定量分析有助于区分健康和缺血或坏死心肌[12]。与CTA相比,双源CT双能量MPI和CTA联合应用可以明显提高冠状动脉疾病诊断的准确率[13-14]。目前认为双源CT双能量加常规CTA有助于提高急性心肌梗死的检出率[15],通过建立动物模型也同样验证了双源CTA双能量是冠状动脉评估的最有价值的方法之一[16]。对于双源CT双能量心肌血池成像灵敏度和特异度的文献报道归纳见表 1。
作者 时间 病例数 参考标准 灵敏度/% 特异度/% Ruzsics等[4] 2008 35 SPECT 84.0 94.0 Zhang等[9] 2010 6(动物) 病理学 88.0~93.0 74.0~79.0 Ko等[10] 2011 41 MRI 89.0 76.0 Kim等[11] 2014 50 MRI 77.0 94.0 Delgado等[12] 2015 36 MRI 73.0 96.0 Wang等[13] 2011 34 SPECT 90.0 86.0 De Cecco等[14] 2014 29 ICA 86.0 75.0 Peng等[15] 2013 9(动物) SPECT/病理学 87.5 92.9 Kerl等[16] 2011 9(动物) MRI/病理学 72.0 88.0 Ruzsics等[17] 2009 36 SPECT 92.0 93.0 注:表中,ICA:侵入性冠状动脉造影 表 1 双源CT双能量心肌血池成像的灵敏度和特异度
Table 1. The sensitivity and specificity of dual-source dual energy myocardial blood pool imaging
Bamberg等[18]对38例确诊为冠心病的患者行负荷双能量动态CT-MPI,结果表明CT的诊断准确率高于MRI。双源CT双能量检测急性胸痛的灵敏度和特异度分别为93%和99%,与组织病理学检查结果有较好的一致性。Ko等[19]对100例冠心病患者行动态CT双能量MPI,其灵敏度和特异度分别为89%和74%。有研究表明,双能量CT比单能量CT有更高的时间分辨率,可避免由使用β-受体阻滞剂引起的对心肌灌注的潜在影响。Rochitte等[20]的研究是迄今为止对CT-MPI进行的样本量最大的研究,比较了381例患者在合并SPECT和侵入性冠状动脉造影术中获得的静态CT-MPI的诊断性能,研究结果表明冠状动脉CTA联合CT灌注成像进行冠心病诊断的准确率较高。赵瑞平等[21]以5只猪心肌梗死模型为实验对象,应用第二代双源CT“一站式”扫描得到的心肌灌注碘图,证实第二代双源CT双能量心肌灌注“一站式”扫描可以准确得到猪急性心肌梗死模型的冠状动脉图像及心肌灌注图像。孙凯等[22]以7只小型猪制作急性心肌梗死模型,行冠状动脉造影及双能量模式CTA和MPI,研究结果显示,第二代双源CT双能量心肌灌注显像可“一站式”获得心肌灌注和CTA图像,进一步提高了心脏CT检测心肌梗死的准确率,且有效辐射剂量低。韩瑞娟等[23]对40例可疑心肌梗死患者用双能量心肌灌注碘图评价心肌梗死的灵敏度和特异度分别为85.0%和93.0%,证实第二代双源CT双能量“一站式”心肌灌注碘图联合冠状动脉CTA检测心肌梗死的准确率高,有效辐射剂量低,具有极大的临床应用潜能。
双源CT双能量心肌血池成像的应用及研究进展
Application and research progress of dual-energy myocardial blood pool imaging by dual-source computed tomography
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摘要: 缺血性心脏病已经成为威胁人类健康的高发疾病,判断供血区心肌灌注情况以及冠脉是否有狭窄对预防、治疗缺血性心脏病有重要意义。双能量CT心肌灌注检查在临床上多用于静态评估心肌血池,用于冠心病或心肌梗死的检查。笔者将近年来双源CT双能量心肌血池成像的原理、扫描方法、图像采集及临床应用做一综述。Abstract: Ischemic heart disease has become a high incidence disease threating to human health, the judgement of the status about myocardial perfusion and whether the coronary is stenosis has great significance for preventing and treating ischemic heart disease. Dual-energy computed tomography myocardial perfusion imaging is always using for static evaluating myocardial blood pool imaging, diagnosing coronary artery disease and myocardial infarction in clinical medicine. The authors review the progress of dual-energy myocardial perfusion imaging via dual source CT in imaging principle, scanning methods, image acquisition and clinical applications.
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表 1 双源CT双能量心肌血池成像的灵敏度和特异度
Table 1. The sensitivity and specificity of dual-source dual energy myocardial blood pool imaging
作者 时间 病例数 参考标准 灵敏度/% 特异度/% Ruzsics等[4] 2008 35 SPECT 84.0 94.0 Zhang等[9] 2010 6(动物) 病理学 88.0~93.0 74.0~79.0 Ko等[10] 2011 41 MRI 89.0 76.0 Kim等[11] 2014 50 MRI 77.0 94.0 Delgado等[12] 2015 36 MRI 73.0 96.0 Wang等[13] 2011 34 SPECT 90.0 86.0 De Cecco等[14] 2014 29 ICA 86.0 75.0 Peng等[15] 2013 9(动物) SPECT/病理学 87.5 92.9 Kerl等[16] 2011 9(动物) MRI/病理学 72.0 88.0 Ruzsics等[17] 2009 36 SPECT 92.0 93.0 注:表中,ICA:侵入性冠状动脉造影 -
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