肺血栓栓塞症CTPA假阳性诊断常见原因分析及影像表现

Analysis of common causes and imaging manifestations of CTPA false-positive diagnosis in pulmonarythromboembolism

目的:分析肺血栓栓塞症(PTE)CT肺动脉成像(CTPA)假阳性诊断的常见原因,以降低PTE的误诊率。方法:搜集我院62例PTE假阳性诊断病例的CTPA资料,观察肺动脉CTPA表现,分析误诊原因并对其进行分型,统计各型的发生率。结果:肺血栓栓塞CTPA假阳性诊断的常见原因包括:①呼吸运动及心脏传导搏动伪影引起的假阳性诊断(17.74%,11/62),假性栓子表现为紧贴肺动脉管壁一侧的窄带状稍低密度影,常累及多支血管;②上腔静脉内高浓度对比剂引起的硬射线伪影导致假阳性诊断(8.06%,5/62),表现为上腔静脉内对比剂浓度较高,周围见放射状分布的条纹状低密度影,累及邻近右肺动脉或右肺上叶肺动脉;③将肺门淋巴结误诊为栓子(12.90%,8/62),假性栓子常位于肺动脉分叉处,邻近肺动脉管壁轮廓光整,未见明显充盈缺损;④肺血管阻力局限性增高所致假阳性诊断(27.42%,17/62),表现为肺动脉期肺动脉管腔内条片状低密度影,主动脉期该条片状低密度影消失,邻近肺组织内常见慢性炎症或伴有同侧胸腔积液;⑤心血管功能差、肺循环减慢所致假阳性诊断(16.13%,10/62),CTPA表现为肺动脉远端分支强化程度减低,管腔内对比剂充盈不良;⑥纵隔及肺门淋巴结肿大压迫邻近肺动脉所致假阳性诊断(9.68%,6/62),CTPA表现为肺门及纵隔多发淋巴结增大、钙化,邻近肺动脉管腔受压狭窄,多见于尘肺及肺结核患者;⑦将支气管黏液栓误诊为肺动脉血栓(8.06%,5/62),表现为肺动脉走行区条状无强化低密度影,近端与支气管相连,周围见肺动脉分支伴行。结论:肺栓塞CTPA假阳性诊断的类型多样,正确识别各型误诊病例的图像特点,规范扫描方案,优化扫描策略,掌握正确的分析方法,有助于降低PTE的假阳性诊断率。

Objective:To analyze the common causes of false-positive diagnosis of pulmonary thromboembolism(PTE)by computed tomography pulmonary angiography(CTPA),in order to reduce the misdiagnosis rate of PTE.Methods:CTPA data of 62 PTE cases with false-positive diagnosis in our hospital were collected.The manifestations of pulmonary artery CTPA were observed,the causes of misdiagnosis were analyzed and classified,and the incidence of each type was counted.Results:Common causes of false-positive CTPA diagnosis of PTE including:①False-positive diagnosis caused by respiratory movement and cardiac conduction pulsation artifacts(17.74%,11/62):the false emboli appeared as a narrow band of slightly low-density shadow attached to one side of the pulmonary artery wall,which often involved multiple vessels.②False-positive diagnosis due to hard radiographic artifacts caused by high concentration of contrast medium in the superior vena cava(8.06%,5/62):the concentration of contrast medium in the superior vena cava was relatively high,and there were streaky low-density shadows with radial distribution around it,which involved the adjacent right pulmonary artery or the right upper lobe pulmonary artery.③Misdiagnosis of hilar lymph nodes as emboli(12.90%,8/62):the false emboli were usually located at the bifurcation of pulmonary artery,and the adjacent pulmonary artery wall was smooth,without obvious filling defect.④False-positive diagnosis caused by localized increase of pulmonary vascular resistance(27.42%,17/62):it was manifested as strip shaped low density shadow,which was seen in pulmonary artery lumen in pulmonary artery phase,and disappeared in aortic phase,and meanwhile,chronic inflammation or ipsilateral pleural effusion was commonly seen in adjacent lung tissue.⑤False-positive diagnosis caused by poor cardiovascular function and slow pulmonary circulation(16.13%,10/62):CTPA showed decreased enhancement of the distal branch of pulmonary artery and poor filling of contrast medium in the lumen.⑥False-positive diagnosis due to the compression on adjacent pulmonary arteries by enlarged mediastinal and hilar lymph nodes(9.68%,6/62):CTPA showed enlargement and calcification of multiple lymph nodes in the hilum and mediastinum,and compression and stenosis of adjacent pulmonary artery lumen,which was more commonly in patients with pneumoconiosis and tuberculosis.⑦Misdiagnosis of bronchial mucus thrombosis as pulmonary artery thrombosis(8.06%,5/62):it was manifested as strip shaped low density shadow without enhancement in the course of pulmonary artery,proximal to the bronchi and accompanied by pulmonary artery branches.Conclusion:There are various types of CTPA false-positive diagnosis of pulmonary embolism.Correct identification of the image characteristics of each type of misdiagnosed cases,standardization of scanning protocols,optimization of scanning strategies,and mastery of correct analysis methods will be help to reduce the false-positive diagnosis rate of PTE.