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1、Computed Tomography of The ChestDong YuchaoChanghai HospitalRsepiratory DepartmentThe 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 around
2、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 body region th
3、at has been examined.CT number The attenuation values,or CT numbers,are expressed as Hounsfield units(HU).CT number=1000 xH2O_H2O0100-1001000-1000waterfatmuscle010-1080-80fatkidneypancreasliverfluidmuscleboneWindow Setting(Level/center and width)WCLlung window-300-40013001600WCLMediastinal window304
4、0300400Special WindowsdensitybrightnessDual windowSpecial WindowsdensitybrightnessSigma windowSpecial WindowsdensitybrightnessAdaptive windowPartial 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 fil
5、l a given layer,the CT number will partly reflect the attenuation of whatever extraneous matreial fills the rest volume.The change in CT number is known as a partial volume artifact.Normal AnatomyMediastinumAnterior:thymus,lymph nodes,mammary vesselsMiddle:pericardium,heart,great vessels,trachea,mai
6、n bronchi,fat,nerves,lymph nodesPosterior:esophagus,descending aorta,nerves,azygos and hemiazygos veins,lymph nodesCarotid Arteries LevelRCC:right common carotidLCC:left common carotidRSA:right subclavian arteryLSA:left subclavian arteryRBV:right brachiocephalic veinLBV:left brachiocephalic vein LBV
7、LCCLSARCCRBVRSABrachiocephalic Artery Level(Sterno-clavicular Joint Level)BA:brachiocephalic artery SCJ:Sterno-clavicular JointLCC:left common carotidLSA:left subclavian arteryRBV:right brachiocephalic veinLBV:left brachiocephalic vein LSALCCBALBVRBVSCJAortic Arch LevelSVC:superior vena cavaIMV:inte
8、rnal mammary vessels:pretracheal-retrocaval spacethymusarchtracheaesophagusSVCIMVAortopulmonary Window LevelSVC:superior vena cavaAA:ascending aortaDA:descending aortaAZ:azygosAADAAZarchcarinaSVCLeft Pulmonary Artery LevelSVC:superior vena cavaLPA:Left Pulmonary Artery LPASVCpericardiumRight Pulmona
9、ry Artery LevelRPA:Right Pulmonary ArteryA-ER:azygoesophageal recessRPAA-ERAortic Root LevelA:aortic rootLA:left atrium PA:pulmonary arteryPV:pulmonary vein PALAAPVCardiac LevelLV:left ventricleRV:right ventricleLA:left atrium RA:right atriumIS:interventricular septum RVLVRALAISLobesSegments and Bro
10、nchi Each lobe is comprised of several smaller units referred to as pulmonary segments.It is 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 bron
11、chus that supplies it.Segment Bronchus Upper Lobe Apical S1 B1 Posterior S2 B2 Anterior S3 B3 Middle Lobe LateralS4 B4 MedialS5 B5 Lower Lobe Superior S6 B6 Medial BasalS7 B7 Anterior BasalS8 B8 Lateral BasalS9 B9 Posterior Basal S10 B10 Upper Lobe Apical Posterior S1+2 B1+2 AnteriorS3 B3 Superior L
12、ingularS4 B4 Inferior LingularS5 B5 Lower Lobe SuperiorS6 B6 Anterior Medial BasalS8 B8 Lateral BasalS9 B9 Posterior BasalS10 B10 SegmentBronchusRight LungLeft LungRight Lung Segments The apical segment(or S1 segment)is shaped like a truncated cone with its broadest base located superiorly filling t
13、he 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 the right hilum,posteriorly and inferiorly and forms the posterior half of the interlobar surface relating to the right
14、 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 surface of S3 extends to the chest wall,while the broadest inferior surface borders the minor fissure which separating S3 from th
15、e 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 neighbor,S5(medial segment).S5 near the right heart border medially,while S4 extends to and comprises a portion of the lateral borde
16、r 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 S5 touch the diaphragmatic surface at their anteroinferior edges.Anteriorly,both segments are adjacent to the anterior ribs ends of the 5th,6t
17、h,and 7th ribs.The right lower lobe is comprised of five pulmonary segments:the superior segment(S6)is situated immediately inferior to the posterior 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
18、a sizeable portion of the posterior margin of the right lower lobe superiorly.It is this segment that surprisingly occupies a sizeable area behind 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
19、 lower lobe.As such,it can be best remembered as the pulmonary segment which occupies most of the posterior costophrenic gutter.S10 also 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
20、 tends to be the largest segment of the right lower lobe.Immediately anterior to S10 is the medial basal segment(S7)which typically 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 a
21、s being immediately inferior to the right hilum,abutting the major fissure ventrally.Inferior to S7 is the anterior basal segment 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
22、 location having a large peripheral surface.The lateral basal segment(S9),located between S8 and S10 is shaped like a triangle 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 hemidiaphr
23、agm are S4,S5,S7,S8,S9,and S10.S8 and S10 have the largest surface areas abutting the diaphragm.Right Lung Bronchi 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 ap
24、pears as a vertical cleft,representing the junction of the superomedial surfaces of the two mainstem bronchi.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 i
25、s explained by the more proximal origin of the right upper lobe bronchus.Soon after its origin,the right 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 lo
26、be bronchial trunk measures approximately 1 cm in length and approximately 1 cm in diameter.The 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 i
27、maged in cross section.The B2 bronchus,supplying the posterior segment has a more horizontal 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 ri
28、ght mainstem bronchus is considered to extend no farther inferiorly than the origin 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
29、 middle lobe bronchus.The middle lobe bronchial trunk measures approximately 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 lob
30、e bronchial trunk continues slightly inferiorly for a short distance before 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
31、 segment(S5).The medial segmental bronchus has a slightly more oblique 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 bron
32、chus but more frequently arises slightly more distally.Regardless,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 orie
33、ntation,the basilar segmental bronchi of the right lower 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
34、a common trunk.The medial basal bronchus(B7)has its 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,ultima
35、tely are seen coursing out to their respective 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 L
36、ung Segments (S1+2)represents a 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 t
37、he right S3 segment,having 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 segment
38、s are stacked one 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 h
39、ave more area 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 segm
40、ental 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
41、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(S6).S6
42、 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 than S9 on the
43、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 occupying the posteromedial
44、 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 and approximately 12 mm
45、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,which gives rise to the lingular
46、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 the anterior segment of the left up
47、per 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 superior to the more vertically oriented li
48、ngular 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 typically horizontal course,supplying the su
49、perior 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 the absence of B7,the left lower lobe basilar bronchial
50、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 the case on the right side,the basilar segmental lower lobe