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1、Computed Tomography of The Chest,Dong YuchaoChanghai HospitalRsepiratory Department,The Theory,The C.T. scan machine takes images using x-rays. The patient lies on the C.T. table and is moved into the C.T. gantry. This part of the machine contains an x-ray tube and x-ray detectors that spin rapidly
2、around the patient taking x-ray measurements. The measurements are fed to a specialized computer that assembles the measurement data into a series of C.T. pictures. The images are viewed as a series of standard 2D pictures. When required, the image data can be used to construct 3D pictures of the bo
3、dy region that has been examined.,CT number,The attenuation values, or CT numbers, are expressed as Hounsfield units(HU).,water,fat,muscle,fat,kidney,pancreas,liver,fluid,muscle,bone,Window Setting,(Level/center and width),lung window,-300-400,13001600,Mediastinal window,3040,300400,Special Windows,
4、Dual window,Special Windows,Sigma window,Special Windows,Adaptive window,Partial Volume Artifact,The CT number calculated for a layer is an average attenuation for all the contents. When the object of interest dose not completely fill a given layer, the CT number will partly reflect the attenuation
5、of whatever extraneous matreial fills the rest volume. The change in CT number is known as a partial volume artifact.,Normal Anatomy,Mediastinum,Anterior: thymus, lymph nodes, mammary vesselsMiddle: pericardium, heart, great vessels, trachea, main bronchi, fat, nerves, lymph nodesPosterior: esophagu
6、s, descending aorta, nerves, azygos and hemiazygos veins, lymph nodes,Carotid Arteries Level,RCC: right common carotidLCC: left common carotidRSA: right subclavian arteryLSA: left subclavian arteryRBV: right brachiocephalic veinLBV: left brachiocephalic vein,Brachiocephalic Artery Level (Sterno-clav
7、icular Joint Level),BA: brachiocephalic artery SCJ: Sterno-clavicular JointLCC: left common carotidLSA: left subclavian arteryRBV: right brachiocephalic veinLBV: left brachiocephalic vein,Aortic Arch Level,SVC: superior vena cavaIMV: internal mammary vessels: pretracheal-retrocaval space,Aortopulmon
8、ary Window Level,SVC: superior vena cavaAA: ascending aortaDA: descending aortaAZ: azygos,Left Pulmonary Artery Level,SVC: superior vena cavaLPA: Left Pulmonary Artery,Right Pulmonary Artery Level,RPA: Right Pulmonary ArteryA-ER: azygoesophageal recess,RPA,A-ER,Aortic Root Level,A: aortic rootLA: le
9、ft atrium PA: pulmonary arteryPV: pulmonary vein,PA,LA,A,PV,Cardiac Level,LV: left ventricleRV: right ventricleLA: left atrium RA: right atriumIS: interventricular septum,RV,LV,RA,LA,IS,Lobes,Segments and Bronchi,Each lobe is comprised of several smaller units referred to as pulmonary segments .It i
10、s important to remember that segmental anatomy is predicated on bronchial anatomy. Similar to bronchial nomenclature, each segment can be named numerically, using a S, and the same number of the corresponding bronchus that supplies it .,Segment,Bronchus,Right Lung,Left Lung,Right Lung Segments,The a
11、pical segment (or S1 segment ) is shaped like a truncated cone with its broadest base located superiorly filling the cupula of the lung. This segment thus extends over the pulmonary apex but does not extend inferiorly to the interlobar (minor fissure) surface.,The posterior segment (S2) extends from
12、 the right hilum, posteriorly and inferiorly and forms the posterior half of the interlobar surface relating to the right major fissure. The anterior segment (S3) of the right upper lobe, which like S2 extends from the right hilar area, is oriented anteriorly and somewhat superiorly. The anterior su
13、rface of S3 extends to the chest wall, while the broadest inferior surface borders the minor fissure which separating S3 from the right middle lobe.,The right middle lobe has two pulmonary segments which are situated side by side; the more lateral segment (S4), approximates the size of its adjacent
14、neighbor , S5 ( medial segment). S5 near the right heart border medially, while S4 extends to and comprises a portion of the lateral border of the right lung. Superiorly, both segments border the right minor fissure, and likewise, both abut the major fissure along their inferior margins. Both S4 and
15、 S5 touch the diaphragmatic surface at their anteroinferior edges. Anteriorly, both segments are adjacent to the anterior ribs ends of the 5th, 6th, and 7th ribs.,The right lower lobe is comprised of five pulmonary segments : the superior segment (S6) is situated immediately inferior to the posterio
16、r segment of the right upper lobe (S2) from which it is separated by the right major fissure. S6 is bordered by the major fissure anteriorly and comprises a sizeable portion of the posterior margin of the right lower lobe superiorly. It is this segment that surprisingly occupies a sizeable area behi
17、nd the anterior segment (S3) of the RUL.,The posterior basal segment (S10) as its name implies occupies the posterior most and inferior most portion of the right lower lobe. As such, it can be best remembered as the pulmonary segment which occupies most of the posterior costophrenic gutter. S10 also
18、 comprises a large portion of the posteromedial border of the right lower lobe and is the segment which is located immediately inferior to S6. S10 characteristically tends to be the largest segment of the right lower lobe.,Immediately anterior to S10 is the medial basal segment (S7) which typically
19、is the smallest pulmonary segment of the lower lobe. Along its superior margin, S7 forms a portion of the major fissure medially, and its location can be best thought of as being immediately inferior to the right hilum, abutting the major fissure ventrally.,Inferior to S7 is the anterior basal segme
20、nt S8, which tends to be rather large in size. This segment along with S6 comprise a large portion of the major fissure surface, laterally. S8 resides in a predominantly lateral location having a large peripheral surface.,The lateral basal segment (S9), located between S8 and S10 is shaped like a tr
21、iangle with its base directed laterally and as such forms a portion of the lateral surface of the right lower lobe. The pulmonary segments which border or touch the right hemidiaphragm are S4, S5, S7, S8, S9, and S10. S8 and S10 have the largest surface areas abutting the diaphragm.,Right Lung Bronc
22、hi,The carina resides approximately at the level of the fifth thoracic vertebral body, and can be localized approximately at the same level as the sternal notch. On CT, the carina visually appears as a vertical cleft, representing the junction of the superomedial surfaces of the two mainstem bronchi
23、. The left mainstem bronchus (LMSB) measures approximately 4.5 cm in length compared to the right (RMSB) which measures approximately 2.5 cm in length. The shortness of the right mainstem bronchus is explained by the more proximal origin of the right upper lobe bronchus.,Soon after its origin, the r
24、ight mainstem bronchus (RMSB) gives rise to the right upper lobe bronchus which typically is directed superiorly and slightly laterally, having an almost 90o angle of incidence with the RMSB. The upper lobe bronchial trunk measures approximately 1 cm in length and approximately 1 cm in diameter. The
25、 trunk then gives rise to the segmental bronchi, B1, B2, and B3. The B1 bronchus supplies the apical segment of the right upper lobe and has a diameter ranging from 4 to 7 mm . On CT, this bronchus is typically imaged in cross section.,The B2 bronchus, supplying the posterior segment has a more hori
26、zontal course relative to B1 but is nevertheless is readily visualized on CT. B3 supplies the anterior segment (S3) and like B2, has a generally horizontal course but proceeds somewhat inferiorly from its origin.,The right mainstem bronchus is considered to extend no farther inferiorly than the orig
27、in of the right upper lobe bronchus. The airway distal to the upper lobe bronchus is referred to as the bronchus intermedius (BI). BI generally averages 2 cm in length and terminates at the point at the origin of the right middle lobe bronchus.,The middle lobe bronchial trunk measures approximately
28、12 mm in length, and 8 mm in diameter. The origin of the middle lobe bronchus marks the point of origin of the right lower lobe bronchus. From its origin off the anterior aspect of the bronchus intermedius, the right middle lobe bronchial trunk continues slightly inferiorly for a short distance befo
29、re giving rise to the B4 and B5 segmental bronchi.,On CT, both of these bronchi are almost routinely seen since they run almost parallel with the axial plane of section. B4 supplies the lateral segment while B5 supplies the medial segment (S5). The medial segmental bronchus has a slightly more obliq
30、ue course than B4. In approximately 30-40% of the cases, B5 may be substantially larger than the lateral segmental bronchus.,The superior segmental bronchus (B6), may arise at, or above the level as the origin of the right middle lobe bronchus but more frequently arises slightly more distally. Regar
31、dless, B6 is the first branch off the lower lobe bronchus, and has a predominantly horizontal course making it readily identifiable on CT. The airway distal to B6 is referred to as the basilar trunk.,Because of their predominantly vertical orientation, the basilar segmental bronchi of the right lowe
32、r lobe are routinely sectioned transversely on CT. It should be pointed out however, there is significant variation as to the points of origin of the basal segmental bronchi. The posterior and lateral basilar segmental bronchi typically arise from a common trunk. The medial basal bronchus (B7) has i
33、ts origin inferior to B6. Oriented medially, B7 supplies the medial basal segment.,Using their course as a guide, identification of the remaining three basilar bronchi is usually straightforward. Potentially arising from a common trunk, B8, B9, and B10, ultimately are seen coursing out to their resp
34、ective segments. B9 + B10 is often referred to collectively as the terminal bronchus. B8 supplies the anterior basal segment; B9 courses laterally to supply the lateral basal segment; B10, directed predominantly posteriorly supplies the posterior basal segment.,Left Lung Segments,(S1+2) represents a
35、 combination of the two separate (apical and posterior) segments seen on the right upper lobe. It is referred to as the apical posterior segment. Combined, S1+2 anatomically is similar in shape to the two segments on the right.,The S3 or anterior segment also is similar to the right S3 segment, havi
36、ng a large area directed anteriorly.,On the left there is no middle lobe; the anatomical equivalent region corresponding to the right middle lobe is known as the lingula, and like the RML, is also composed of two segments. Unlike their counterparts on the right however, the segments are stacked one
37、on top of another, rather than side by side.,The superior lingular segment (S4) is positioned immediately inferior to S3 and is directly above the inferior lingular segment (S5). Both lingular segments have their greatest area directed anteriorly and inferiorly. Additionally, S4 tends to have more a
38、rea directed laterally while S5 has more area directed medially, abutting the mediastinum. Both segments extend anteroinferiorly to reach the ventral surface of the left hemidiaphragm, and hence border a large portion of the anteroinferior surface of the major fissure.,The left lower lobe segmental
39、architecture is similar to that of the right lower lobe, however because the anterior and medial basal segments share a common bronchial supply, these two segments are characteristically combined, forming an anterior medial basal segment (S8). Therefore, the anterior segment is combined with the med
40、ial segment but may be denoted by SX7. The anterior medial basal segment is bordered anteriorly by the interlobar (major fissure), and abuts the visceral pleural surfaces of the two lingular segments located anterosuperiorly.,Forming the remainder of the interlobar surface is the superior segment (S
41、6). S6 is identical to its counterpart on the right.,The lateral basal segment, S9 and the posterior basal segment, S10 also closely approximate the same segments in the right lower lobe. S9 (lateral basal segment) has its broadest surface area exposed posterolaterally, and may be slightly larger th
42、an S9 on the right. S9, not in continuity with the major fissure, occupies much of the posterior costophrenic sulcus posterolaterally.,Like its contralateral counterpart, S10 (posterior basal segment) is quite large and occupies the posterior and inferior most portion of the right lower lobe occupyi
43、ng the posteromedial costophrenic gutter.,Left Lung Bronchi,The origin of the left upper lobe bronchus occurs at a lower level than the origin of the right upper lobe bronchus. The left upper lobe bronchial trunk gives rise to the upper lobe and lingular segmental bronchi. Measuring 9 mm in length a
44、nd approximately 12 mm in diameter, the left upper lobe bronchial trunk characteristically appears short but has a large diameter.,The left upper lobe bronchial trunk divides giving rise to the ascending upper division (eventually giving rise to B1+2, and B3), and the descending lower division, whic
45、h gives rise to the lingular segmental bronchi, B4 and B5.,The course of B1+2 has vertically and horizontally oriented components as bronchial rami divide to supply the apical posterior segment. The B3 bronchus will have a more horizontal course, similar to that seen on the right side. B3 supplies t
46、he anterior segment of the left upper lobe.,The lingular segmental bronchi are some of the most difficult segmental bronchi to visualize on CT. Their inconspicuousness is a result of their oblique course. If seen, B4 has a more horizontal course and supplies the superior lingular segment. B4 is supe
47、rior to the more vertically oriented lingular bronchus (B5) which supplies the inferior lingular segment,Reviewing shows that there are only 4 segments in the left lower lobe, compared to 5 on the right.The B6 (superior segmental bronchus) bronchus is similar to that seen on the right side having a
48、typically horizontal course, supplying the superior segment.,The bronchial segment that supplies the medial basal segment on the right side ( B7 ) is not a separate entity on the left. As a result, the S7 and S8 segments are combined and supplied by B8, (anterior medial bronchus). Also because of th
49、e absence of B7, the left lower lobe basilar bronchial trunk typically measures slightly longer than the right lower lobe basilar trunk; while the overall diameter of the left lower lobe basilar trunk is similar measuring approximately 10 mm, the average length measures approximately 15 mm .,As is t
50、he case on the right side, the basilar segmental lower lobe bronchi course predominantly vertically, appearing in cross-section on CT. The direction and course make identification of the remaining lower lobe bronchi straight forward. Like their contralateral counterparts, B9, and B10 supply the late
