Anatomy Of Pulmonary Veins Of Superior Lobe Of The Left Lung By Multi-slice Spiral Computed Tomography

Background: At present, most of the studies about the bronchovascular anatomy of the lung are focused on the bronchus and pulmonary arteries while only a few are on the pulmonary veins. But the pulmonary veins are the landmarks in the division of the pulmonary segments, so it is urgent to supply more and more sectional anatomic data about the pulmonary veins. In these years, multi-slice spiral CT (MSCT) is used in clinical practice widespreadly. It has some advantages of rapid volume scanning, multiplanar reconstruction, random thickness reconstruction and 3-dimensional reconstruction which provide the technology supports for the sectional anatomic studies in vivo. So it's necessary to explore the sectional anatomy and 3-dimensional structures of the bronchi and blood vessels of the lungs especially the pulmonary veins by MSCT.Objective : To explore the branch numbers, the confluens types, and the distribution regularity of the pulmonary segmental veins of the superior lobe of the left lung of the Chinese adults in vivo in a large sample using MSCT in order to provide sectional anatomic bases for the imaging diagnosis, interventional therapy of the diseases of the superior lobe of the left lung and pulmonary segmentectomy in the thorax surgery.Materials and methods: 160 male adults without any pathological changes in the chest and abdomen are selected for this study. They are aged from 18 to 60 years old and the average age is 37.4 years. The acquired MSCT raw images with the thickness of 0.75mm were dataed in the Volume Wizard Work Station to be reconstructed in cross, coronal, and sagittal planes. The radiation reconstruction based the hilum of lung and the reconstruction along the long axis of the pulmonary veins, as well as the thick reconstruction of the blood vessels in different directions and 3D reconstructions are also undertaken to evaluate the pulmonary veins of the superior lobe of left lung in different window widthes and levels.Results: The occurrence rate of apicoposterior segmental veins (V₁₊₂) is 71.3% (114/160), which is merged by apical and posterior segmental veins (V₁₊₂). Meanwhile the absence rate of V₁₊₂ is 28.8% (46/160), apical segmental veins (V₁) converge into left superior pulmonary vein solely, while posterior and anterior segmental veins merge into posteroanterior segmental vein (V₂₊₃), then converge into left superior pulmonary vein. The occurrence rate of apicoposterior segmental vein (V₁₊₂ ) is affected by the position of posterior segmental vein(V₂ ). When V₂ is high-set type, V₂ and V₁ merge into V₁₊₂ and when V₂ is low-set type, V₂ and V₃ merge into V₂₊₃.There are 1 to 6 branches of V₁, defined by the their positions, which are apical branch (98.1%), anterior branch(75.6%), external branch(57.5%), anterointernal branch(8.1%),anteroexternal branch(11.3%),posterior branch(29.4%) and internal branch (6.3%) Anterolateral to the apical segmental bronchus (B₁) and superior to anterior segmental bronchus (B₃) and anterior segmental artery (A₃), the thick V₂ forms the posterior segmental venous arch, which goes from posterior superoexternal to anterior inferointerior. There are 1 to 7 branches of V₂ , which are apical branch (96.8%), posteroexternal branch(85%), external branch(52.5%), posterior branch (56.9%), posterointernal branch(30.6%), superior branch(20%) and internal branch (15.6%).Generally, the branches of anterior segmental vein can be divided into the superior and inferior parts. There is always one branch of the superior part, which converges into V₁₊₂ or V₁ and the confluent height from the position of confluens of V₁ and V₂ to the root of V₁₊₂. Its occurrence rate is 95.6%. There are 1 to 6 branches of the inferior part, they are anterior branch (94.4%), middle branch(67.5%), posterior branch(64.4%), apical branch(20%), inferior branch(16.9%), anterointernal branch (11.8%), and anteroexternal branch (6.3%), of which the anterior branch is much thicker. Except apical and inferior branches, all of others align to horizontal position or approximately. The branches of the inferior part merging with the V₂ or directly joined into the left superior pulmonary vein.The percent of superior and inferior lingular segmental veins forming the lingual vein (V₄₊₅) in conjunct trunk is 61.3% (98/160), while the percent of the two veins converging into the left superior pulmonary vein respectively is 38.8% (62/160). There are 1 to 5 branches of V₄, they are anterior branch(81.9%), posterior branch(89.4%), middle branch(23.8%), posteroexternal branch(3.8%), and anterointernal branch (2.5%), most of which join the V₄₊₅ or left superior pulmonary vein alone and the other minority branches join V3 (3.8%,6/160). V₅ also has 1 to 5 branches, which are superior branch(93.8%), inferior branch(96.3%), superoanterior branch(16.8%), superoposterior branch(15.6%), superomiddle branch(6.9%), middle branch(5.6%), and internal branch(3.8%). Most of the branches join the V₄₊₅ or left superior pulmonary vein alone while there are 5.6% (9/160) V₅ joined into left inferior pulmonary vein.Except for all the branches mentioned above, there are still some little accessory tributaries, which converged into V₁ , V₁₊₂ , V₄ , V₅ or V₄₊₅. Meanwhile the accessory tributaries of V₂₊₃ and V₃ are seldom.Conclusions:1. The MSCT is an ideal method to investigate the bronchovascular anatomy of the lung in vivo because it can display the sectional anatomy and spatial distribution of the segmental veins sufficiently.2. The segmental veins of the superior lobe of the left lung vary comparatively large, and there are tremendous variance in the number and course of the tributaries.3. The posterior segmental veins(V₂) have two types: one is the high-set type merged with apical segmental vein (V₁), the other is low-set type merged with anterior segment ( V₃ ) , which breaks the traditional view about anatomy of the apicoposterior segment vein ( V₁₊₂ ) .4. The branches of anterior segmental vein (V₃) include the superior and inferior parts . The branches of the superior part converge into V₁₊₂ or V₁ .while the inferior part's branches converge into left superior pulmonary vein directly or joining with the posterior segmental vein ( V₂ ) and then converge into left superior pulmonary vein.5. 38.8% of superior and inferior lingular segmental veins (V₄ and V₅) are not in conjunct trunk and 5.6% (9/160) V₅ join into left inferior pulmonary vein.