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Self-assessment CME RadioGraphic 自我评价式继续医学教育读物 · 第374期 ·
鉴别诊断方法  Assess the Pulmonary Vasculature 评估肺的脉管系统 Pulmonary arterial findings suggestive of pulmonary hypertension include central pulmonary artery enlargement, pulmonary artery–to-aorta ratio greater than 1, and increased segmental artery-to-bronchus ratio. 提示肺动脉高压引起马赛克征的肺动脉异常表现包括：肺动脉主干增粗，肺动脉与主动脉的比值＞1，肺动脉段分支与伴行支气管的比例也变大。 Although the Framingham Heart Study set a normal cutoff value for pulmonary artery size at 29 mm for men and 27 mm for women (measured as the transverse diameter of the main pulmonary artery on an axial image at the level of the bifurcation of the right pulmonary artery), this isolated value is not specific for pulmonary hypertension, as multiple other factors can affect pulmonary artery size, including body mass index, systemic hypertension, diabetes, age, and underlying cardiovascular disease (46,47). A more accurate measurement is to compare the ratio of the diameter of the main pulmonary artery to that of the ascending aorta (transverse diameter measured on the same axial image as used for the main pulmonary artery measurement), where a ratio greater than 1 is suggestive of pulmonary hypertension (Fig 13) (48,49). In addition to the size of the main pulmonary artery, one should also assess the segmental artery-to-bronchus ratio. If this ratio is greater than 1 in three or more lobes, this finding is also highly specific for pulmonary hypertension (46). 虽然Framingham心脏研究对肺动脉粗细设定了一个临界值，男性为29mm，女性为27mm（测量方法：轴位图像右肺动脉分叉处的肺动脉主干横径），这个数值不能孤立来看，对肺动脉高压并无特异性，因为引起肺动脉管径变化的因素很多，包括体质指数，系统性高血压，糖尿病，年龄，已及其他基础的心血管疾病。更准确的测量应该是以肺动脉主干的横径与升主动脉横径（测量平面与肺动脉主干测量平面相同）进行比较算出比值，比值＞1提示肺动脉高压（图13）。除肺动脉主干外，应该参考肺动脉段分支与支气管的比例，如果比例超过1，而且在三个或更多的肺叶发现这种改变，对肺动脉高压的诊断有较高的特异性。 Figure 13. PAH in a 24-year-old woman with a mean pulmonary artery pressure of 64 mm Hg. 肺动脉高压患者，24岁，平均肺动脉压为64mmHg. (a) Axial image from CT pulmonary angiography (lung window) shows mosaic attenuation with more nodular areas of ground-glass opacity centered around the pulmonary arteries. This appearance is different than the more segmental areas of hyperattenuation and hypoattenuation seen in chronic thromboembolic disease. （a）肺窗轴位CT肺动脉造影显示马赛克征，伴有多数围绕肺动脉为中心分布的磨玻璃结节区。这种表现与在慢性肺栓塞性疾病所见到的以肺段分布的高和低密度区不同。 (b) Expiration CT image shows increased attenuation throughout the lung, excluding airtrapping and a small airways cause. （b）呼气相CT显示全肺密度增加，排除了空气潴留和小气道疾病所致的马赛克征 (c) CT image shows transverse measurement of the main pulmonary artery, which is only 26 mm. However, the main pulmonary artery is larger than the aorta, which is abnormal. （c）CT影像，测量肺动脉主干横径仅为26mm，但肺动脉主干明显比主动脉粗，这是异常现象。 (d) Four-chamber CT image shows mild flattening of the interventricular septum (arrow) suggestive of increased right heart pressures, as the image was obtained during systole (atrioventricular valves are closed). There are also prominent trabeculae in the right ventricle (*), suggestive of right ventricular hypertrophy. （d）CT四腔图像显示变扁的室间隔（箭），因图像在收缩期（房室瓣关闭）获得，故提示右心压力增高。同时可以看到右心室小梁凸起，提示右心室肥厚。 In addition to assessing size of the pulmonary arteries, one should assess the morphology of the pulmonary vasculature. For instance, abruptly tapering or corkscrew vessels are associated with pulmonary hypertension, as are dilated bronchial or other systemic collaterals (50). In cases of CTEPH, which are important to recognize since invasive treatments are possible (51), close inspection of the pulmonary vasculature scans can demonstrate adherent thrombus (Fig 14), abrupt occlusion of pulmonary arteries, luminal irregularities with eccentric wall thickening, abrupt caliber change (often due to recanalization), and webs or bands (21,52,53). 除了测量肺动脉直径，还要记得评估肺脉管结构的形态。例如，血管突然变尖或扭曲与肺动脉高压有关，也可同时看到支气管扩张或其他体动脉分支侧枝形成。在CTEPH的病例，因为涉及到有创治疗，及时作出诊断非常重要，仔细观察肺动脉结构可发现附壁血栓（图14），肺动脉的突然闭塞，管腔不规则并管壁的偏心性增厚，管径的大幅度变化（通常继发于再通），以及网状和带状改变。 Figure 14. Mosaic attenuation in a 56-year-old man with chronic thromboembolic disease 56岁男性，患有慢性血栓栓塞性疾病，出现马赛克征
(a) Sagittal CT image shows the difference in segmental pulmonary arterial size in areas of hypoattenuated lung due to vascular occlusion (white outline) versus in areas of hyperattenuated lung due to increased perfusion (black outline). The large airways are normal and the main pulmonary artery is enlarged (*). （a）矢状位CT，血管闭塞区肺野密度降低（用白线勾画的区域），灌注增加区肺野密度升高（用黑线勾画的区域），两区内肺动脉段分支的粗细有明显差别。大气道正常，肺动脉主干增粗（*）。
(b) Sagittal CT image (soft-tissue window) shows marked enlargement of the main pulmonary artery (*) compared with the aorta (Ao). Chronic thrombus is present in the left pulmonary artery (arrow). （b）矢状位CT（软组织窗）显示肺动脉主干（*）与主动脉（Ao）相比明显增粗。左肺动脉内可见慢性血栓。 Differentiating between PAH (also known as primary pulmonary hypertension) and CTEPH is not always easy. Classically, patients with mosaic attenuation due to CTEPH often demonstrate a well-demarcated segmental or subsegmental distribution of mosaicism due to the vascular distribution of thrombi, whereas the mosaic pattern in PAH often manifests as focal perivascular hyperattenuation or small scattered areas of low attenuation confined to the secondary pulmonary lobule (20). The perivascular areas of hyperattenuation may mimic discrete centrilobular ground-glass nodules that are of uncertain cause but thought to represent cholesterol granulomas, large plexogenic arterial lesions, or small systemic collateral arteries (Fig 13) (54). In addition, dilated peripheral arteries can have a corkscrew morphology (20). While adherent thrombus is a good clue to the presence of CTEPH, in situ thrombus and/or atherosclerosis may result from severe long-standing PAH and can sometimes be confused for CTEPH, so assessment of the pattern of mosaic attenuation is important for differentiation of these entities (20,55,56). 在PAH（即所谓原发肺动脉高压）和CTEPH之间进行鉴别不总是那么容易。一般来讲，由CETPH引起的马赛克征在分布上常以段和亚段清楚为界，这是由于血管内的栓子如此分布所致；相反PAH所致的马赛克征，常呈以血管为中心的局灶高密度影，或以二级小叶为界的散在的低密度区。围绕血管的高密度区与分散的小叶中心磨玻璃结节很相似，后者原因不确定，但多认为与胆固醇肉芽肿，大血管病变，或体动脉小侧枝循环等有关（图13）。此外，外周肺动脉分支扩张可产生扭曲的形态改变。附壁血栓是提示CTEPH的重要线索，长期的PAH也可引起原位血栓和/或动脉粥样硬化，有时会和CTEPH混淆，因此，甄别马赛克征的形态特点对鉴别这些疾病非常重要。 未完待续： 资料来源 | http://pubs./doi/full/10.1148/rg.2015140308 |
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