1.CR Anatomy

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Editors: Collins, Jannette; Stern, Eric J.

Title: Chest Radiology: The Essentials, 2nd Edition

Copyright 2008 Lippincott Williams & Wilkins

> Table of Contents > Chapter 1 !ormal "natomy of the Chest

Chapter 1Normal Anatomy of the Chest

Learning Obecti!es

1# !ame an$ $efine the three %ones of the airays#

2# 'efine a secon$ary p(lmonary lob(le an$ itsappearance on highresol(tion comp(te$ tomography)CT*#

+# List the lobar an$ segmental bronchi of both l(ngs#

,# -$entify the folloing str(ct(res on theposteroanterior chest ra$iograph.

L(ngs/right an$ left right (pper3 mi$$le3 an$loer lobes left (pper )incl($ing ling(la* an$loer lobes

4(lmonary arteries/main3 right3 left3 rightinterlobar3 left loer lobe

"iray/trachea3 carina3 main bronchi

5iss(res/minor3 s(perior accessory3 inferior

accessory3 a%ygos"orta/ascen$ing3 arch )/6knob/ *3$escen$ing

7eins/s(perior ena caa3 a%ygos3 left s(periorintercostal )/6aortic nipple/ *

"ortop(lmonary in$o

9ight paratracheal stripe

:(nction lines/anterior3 posterior"%ygoesophageal recess


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4araspinal lines

Left s(bclaian artery

;eart/right atri(m3 left atrial appen$age3 leftentricle3 locations of the fo(r car$iac ales


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;eart/left entricle3 right entricle3 left atri(m3right atri(m3 mitral ale3 aortic ale3 tric(spi$ale3 p(lmonary ale3 coronary arteries )leftmain3 left anterior $escen$ing3 left circ(mfle@3

right3 posterior $escen$ing*3 coronary sin(s4ericar$i(m3 incl($ing pericar$ial recesses

4(lmonary arteries/main3 right3 left3 rightinterlobar3 segmental

"orta/ascen$ing3 arch3 $escen$ing

"rteries/brachiocephalic )innominate*3 commoncaroti$3 s(bclaian3 a@illary3 ertebral3 internalmammary3 intercostal

7eins/s(perior an$ inferior p(lmonary3 s(perioran$ inferior ena caae3 brachiocephalic3s(bclaian3 a@illary3 internal (g(lar3 e@ternal

(g(lar3 a%ygos3 hemia%ygos3 left s(periorintercostal3 internal mammary


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:ean 5erne )1,D/E1==8*3 On theNatural Part of Medicine

Fo(Ge hear$ it before/hatGs important in real estatehol$s tr(e for (n$erstan$ing $iseases of the chest./6location3 location3 location#/ " goo$ ra$iologistknos the anatomy3 so $onGt skip this chapterH Thischapter is an abbreiate$ reie of thoracic anatomy asseen on chest ra$iographs an$ comp(te$ tomography)CT* of the chest# "s a res(lt of $ifferences in patientage3 bo$y habit(s3 positioning3 inspiratory effort3 e@amtechniI(e3 an$ many other factors3 normal anatomicstr(ct(res ill ary in appearance on chest ra$iographsfrom e@am to e@am3 patient to patient3 an$ een breathto breath# Jome str(ct(res are not seen consistently)posterior (nction line*3 hereas others are seen onmost e@ams )left (pper lobe bronch(s on lateral ie*#Jhoing the myria$ $ifferent appearances of normalanatomic str(ct(res is beyon$ the scope of this chapterthey are learne$ by paying close attention to an$i$entifying normal str(ct(res on tho(san$s of chestra$iographs#

" freI(ent I(estion of me$ical st($ents an$ resi$ents ontheir first rotation on a chest ra$iology serice is./6;o $o yo( look at a chest ra$iographK/ Theapproach to interpretation of the chest ra$iograph is apersonally eoling art# " personGs approach changesoer time after seeing many chest ra$iographs# That

anser $oesnGt help the beginner3 so a fe general/6chest ra$iograph r(les/ are offere$ in Table 113an$ reference stan$ar$s are presente$ in Table 12#!ormal anatomic str(ct(res are labele$ onposteroanterior )4"* an$ lateral chest ra$iographs )5igs#11 an$ 12* an$ a@ial CT images )5igs# 1+ an$ 1,*#The frontal chest ra$iograph an$ a@ial chest CT imagesare iee$ as if looking at the patient3 ith the patientGs

right si$e on the ieerGs left# Lateral ra$iographs are3 byconention3 iee$ ith the patient facing to the ieerGs


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left )patientGs left si$e closest to the imaging plate*#

TA"LE #$# %NTE&'&ETAT%ON O(

T)E C)EST &A*%O+&A'):-&LES TO (OLLO/

1# When yo( hae them3 alays look at both ies)4" an$ lateral*# To confirm that pathology isithin the chest3 it m(st (s(ally be seen in thechest on both ies#

2# The right heart bor$er is forme$ by the rightatri(m3 an$ it is obsc(re$ by me$ial segmentright mi$$le lobe processes )$isease limite$ tothe lateral segment ill not obsc(re the rightheart bor$er*#

+# The left heart bor$er is forme$ mainly by theleft entricle an$ is obsc(re$ by ling(larprocesses#

,# The right $iaphragm is (s(ally 1#= to 2#0 cmhigher than the left#

=# The $iaphragm is obsc(re$ by loer lobeprocesses )(nless only the s(perior segment ofthe loer lobe is inole$*#

?# 4ortions of the maor fiss(res are ariably seenon the lateral ie as obliI(e lines from theanterior $iaphragm to the (pper thoracic spine3

to the leel of the aortic arch#D# The minor fiss(re is on the right3 separating theright (pper lobe from the right mi$$le lobe# -tco(rses from the right hil(m to the right lateralanterior chest all an$ is ariably seen on 4"an$ lateral chest ra$iographs#

8# !ormal hilar opacities are pre$ominantly ca(se$by the p(lmonary arteries an$ sho(l$ be

symmetric in si%e an$ $ensity#


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0ones of the Air1aysThe airays are compose$ of three %ones# The conductivezoneincl($es the trachea3 bronchi3 an$ nonaleolate$bronchioles )air cannot $iff(se thro(gh the ell$eelope$ all*# The transitory zonehas both con$(ctiean$ respiratory f(nctions an$ consists of respiratorybronchioles3 aleolar $(cts3 an$ aleolar sacs# The

respiratory zoneconsists of aleoli# The primary f(nctionof this %one is the e@change of gases beteen air an$

# The aortic arch3 or /6knob3/ is aboe theleft hil(m# )Watch o(t for the right aortic archariantH*

10# The trachea is mi$line b(t may be $eiate$ tothe right or forar$ from a tort(o(s aorta#

11# The costophrenic angles sho(l$ be sharp onboth ies )sharp eno(gh to pick yo(r teethith*3 e@cept in patients ith seere p(lmonaryemphysema3 res(lting in flattening of thehemi$iaphragms#

12# With goo$ inspiratory effort3 the si%e of theheart on the 4" ra$iograph is normally lessthan or eI(al to =0 of the i$est $iameter ofthe thoracic cage#

1+# 9ight mi$$le lobe an$ ling(lar processes areproecte$ oer the heart on the lateral ie#

1,# " yo(ng healthy person can take a breath $eepeno(gh to inflate the l(ngs to the leel of the10th rib posteriorly )or the si@th rib anteriorly*#

1=# Mpacity of the l(ngs sho(l$ be symmetric(nless the patient is rotate$#

1?# The stomach b(bble is (n$er the lefthemi$iaphragm# )Watch o(t for sit(s iners(s#*

1D# 'onGt forget to look at the bones an$ softtiss(es#


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passes oer the left main bronch(s3 sho(l$ be lessthan the i$th of the aortic knob# The aortic arch isappro@imately + cm aboe the carina in a$(lts (ntil

the aorta begins to get tort(o(s# The leftp(lmonary artery is appro@imately + cm $on theleft main bronch(s then ascen$s (p an$ o(t atappro@imately ,= $egrees#AzygotrachealThe a%ygos ein3 if is(ali%e$ )at theright tracheobronchial angle*3 sho(l$ be no i$erthan appro@imately one half the i$th of thetrachea3 an$ its height sho(l$ be no greater thanthe i$th of the trachea#Tracheobronchial wall to lumenThe all of thetrachea or bronch(s sho(l$ not be thicker thanappro@imately one eighth of the $iameter of thel(men# The tracheal $iameter sho(l$ be eI(al onthe 4" an$ lateral ies an$ sho(l$ be less thanthe i$th of a ertebral bo$y#Right lower lobe artery to tracheaThe right loerlobe p(lmonary artery sho(l$ not be i$er than thei$th of the tracheal l(men#ilar heightThe left hil(s sho(l$ be appro@imately2 cm higher than the right3 beca(se the leftp(lmonary artery has to go oer the left mainbronch(s#Arteriobronchial"n artery an$ its accompanyingbronch(s sho(l$ be the same si%e )seen best/6en$on/ *#DensityCardiohepaticThe heart sho(l$ be abo(t half as$ense as the mi$$le of the lier )itGs abo(t half asthick*# This reference reI(ires goo$ e@pos(re#


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on each si$e of the spine#!ntrahepaticThe top of the lier sho(l$ be abo(thalf as $ense as the mi$$le3 beca(se itGs abo(t half

as thick3 proi$e$ the $iaphragm $omes normally#Right paratracheal"#aorticThe $ensity to the rightof the trachea at the leel of the aortic arch sho(l$neer be as great or greater than the $ensity of theaortic knob#ilarThe hila sho(l$ be the same $ensity )they arecompose$ of the same asc(larity*#

(%+&E #$#. Normal anatomic str2ct2res on

5osteroanterior 6'A7 and lateral chestradiogra5hs. A:4" ie shoing trachea )$*3 rightmainstem bronch(s )%*3 left mainstem bronch(s )&*3aortic /6knob/ or arch )'*3 a%ygos ein emptyinginto s(perior ena caa )(*3 right interlobarp(lmonary artery ))*3 left p(lmonary artery )**3 right(pper lobe p(lmonary artery )tr(nc(s anterior* )+*3right inferior p(lmonary ein ),*3 right atri(m )$-*3

left entricle )$$*3 an$ other str(ct(res as labele$# ":


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Lateral ie shoing p(lmonary o(tflo tract )$*3ascen$ing aorta )%*3 aortic arch )&*3 brachiocephalicessels )'*3 trachea )(*3 right (pper lobe bronch(s

))*3 left (pper lobe bronch(s )**3 right p(lmonaryartery )+*3 left p(lmonary artery ),*3 confl(ence ofp(lmonary eins )$-*3 an$ other str(ct(res as labele$#

4#,

(%+&E #$3. Normal 'A)A* and lateral)"* chestradiogra5hs3 shoing the str(ct(res n(mbere$ an$labele$ in 5ig(re 11#


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)white dashed arrow* segmental bronchi# +:-mageinferior to )(* shos in$ii$(al loer lobe basilarsegmental bronchi. right me$ial )A*3 anterior )/*3

posterolateral )C*3 an$ left me$ial )0*3 anterior )1*3lateral )2*3 an$ posterior )3*# !ote that in$ii$(al leftanterior an$ me$ial basilar segmental bronchi areseen3 hich arise from a common anterome$ial basilartr(nk# Jeparate right posterior an$ lateral basilarsegmental bronchi are not seen on this image#

4#=

(%+&E #$. A9ial CT images)=mm collimation* ofthe normal me$iastin(m ith intraeno(s contrastenhancement# 5or all images3 the in$o i$ths an$leels are +=0 an$ +=3 respectiely# A:The

intraeno(s contrast as inecte$ from a rightantec(bital ein# Aery a@ial CT scan of the chest )10mm collimation or less* in patients ith stan$ar$anatomy ill hae at least one /6fieesselimage/ like this3 shoing the left brachiocephalicein )$*3 right brachiocephalic ein )%*3 innominate)brachiocephalic* artery )&*3 left common caroti$artery )'*3 an$ left s(bclaian artery )(*# ":-mage

inferior to )A* shos the aortic arch )A* an$ s(periorena caa )4* $ensely enhancing ith contrast# C:


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-mage inferior to )"* shos ascen$ing aorta )AA*3$escen$ing aorta )0A*3 left p(lmonary artery )5PA*3an$ s(perior ena caa )46C*# *:-mage inferior to

)C* shos the right p(lmonary artery )RPA*# E:-mageinferior to )** shos the right )R55* an$ left )555*p(lmonary arteries# (:-mage inferior to )E* shos theleft s(perior p(lmonary ein )54P6*# +:-mage inferiorto )(* shos the right s(perior p(lmonary ein)R4P6*# ):-mage inferior to )+* shos the left atri(m)5A* an$ left inferior p(lmonary ein )5!P6*# %:-mageinferior to ))* shos the right atri(m )RA*3 aortic

o(tflo )AO*3 left atri(m )5A*3 an$ right inferiorp(lmonary ein )R!P6*# J:-mage inferior to )%* shosthe right entricle )R6*3 left entricle )56*3interentric(lar sept(m )dashed blac. arrow*3papillary m(scles )solid blac. arrow*3 esophag(s)white arrow*3 an$ inferior ena caa )!6C*#

4#?4#D

(%+&E #$. Secondary 52lmonary lob2le.!ormal


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Tracheobronchial AnatomyThe intrathoracic tracheais ? to cm in length )2* an$enters the thora@ 1 to + cm aboe the leel of thes(prasternal notch# The (pper limits of normal for coronalan$ sagittal tracheal $iameters in a$(lts on chestra$iography are 21 an$ 2+ mm3 respectiely3 for omen3an$ 2= an$ 2D mm for men )+*# The trachea has 1= to 20

Cshape$ rings of hyaline cartilage )absent in theposterior membrano(s trachea*3 hich proi$e therigi$ity that preents the trachea from collapsing ),*# Thetrachea $ii$es into rightan$ left mainstem bronchiatthe carina# The right main bronch(s3 abo(t 2#= cm inlength3 is shorter3 i$er3 an$ more nearly ertical thanthe left#


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an$ are referre$ to as bronchioles# The bronchioles$ii$e3 an$ the last of the p(rely con$(cting airays isreferre$ to as the terminal bronchiole#


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The maor )obliI(e* fiss(res r(n obliI(ely forar$ an$$onar$ from appro@imately the leel of the fifththoracic ertebral bo$y to the $iaphragm an$ $ii$e thel(ngs into (pper an$ loer lobes )5ig# 1*# The right

ma7or fissureis more obliI(e3 en$s f(rther forar$inferiorly )more anterior on the lateral chest ra$iograph*3merges ith the right hemi$iaphragm3 an$ oins theminor fiss(re# The minor 8horizontal9 fissureseparatesthe right mi$$le from the right (pper lobe an$ fans o(tforar$ an$ laterally from the right hil(s )5ig# 110*# -t is(n(s(al to be able to trace both fiss(res in their entiretyon chest ra$iographs# 5iss(res are often

/6incomplete/ an$ only partially separate lobes#Mn CT scans3 the region of the maor fiss(res can (s(allybe seen as a ban$ of aasc(larity# The fiss(re itself maybe inisible3 or it may be seen as a poorly $efine$ orell$efine$ ban$ of $ensity3 $epen$ing (pon slicethickness# The position of the minor fiss(re can beinferre$ on CT scans from the large oal $eficiency ofessels on one or more sections at the leel of the

bronch(s interme$i(s#

!(mero(s accessory fissuresmay be i$entifie$ as normalariants# "ppro@imately 1 of the pop(lation ill hae anaccessory azygos fissure3 creating an accessory a%ygoslobe in the right s(perome$ial l(ng )5ig# 111*# Thea%ygos fiss(re contains the a%ygos ein )hich3 in thecase of an a%ygos fiss(re3 is alays locate$ higher than

its (s(al location in the tracheobronchial angle* ithin itsloer margin3 an$ it is easily seen on chest ra$iographybeca(se it contains fo(r ple(ral layers )to isceral an$to parietal*# The left minor fissureseparates the ling(lafrom the other left (pper lobe segments# The superioraccessory fissureseparates the s(perior segment fromthe basal segments in either loer lobe3 is hori%ontallyoriente$3 an$ is seen belo the leel of the minor fiss(re

on the right# The inferior accessory fissureseparates theme$ial basal segment from


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other basal segments in either loer lobe3 an$ it r(nsobliI(ely (par$ an$ me$ially toar$ the hil(s from the

$iaphragm )5ig# 112*#

4#8

4#

(%+&E #$


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=ediastinal "lood >essels

Climbing the $iaphragm from lateral to me$ial can betho(ght of as climbing the A5Ps )Anterior3 5ateral3 an$Posterior basilar segmental bronchi*3 as a ay to

remember this orientation# 9NL3 right (pper lobe9BL3 right me$ial lobe 9LL3 right loer lobe LNL3 left(pper lobe3 LLL3 left loer lobe#

(%+&E #$?. *iagrams of normal air1ay anatomy,

lateral !ie1s. A:9ight bronchial tree# !ote that themi$$le lobe bronchi are relatiely anterior )rightmi$$le lobe pne(monia is proecte$ anteriorly oer theheart on a lateral chest ra$iograph*# 9LL3 right loerlobe 9BL3 right mi$$le lobe 9NL3 right (pper lobe#":Left bronchial tree# !ote that the ling(lar bronchiare relatiely anterior )analogo(s to the right mi$$lelobe bronchi*# LLL3 left loer lobe LNL3 left (pperlobe#


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The thoracic aortahas ascen$ing3 transerse )arch*3 an$$escen$ing portions# The ascen$ing portion becomesmore prominent as a patient ages# Mn a frontal chestra$iograph3 the arch is seen to the left of mi$line as a

smooth /6knob#/ The $escen$ing portion gra$(allymoes from a position to the left of the ertebral bo$iesto an almost mi$line position before e@iting the chestthro(gh the aortic hiat(s in the $iaphragm# The threemaor aortic branches3 lying anterior to an$ to the left ofthe trachea3 are )in or$er from the patientGs right to left*the brachiocephalic)innominate* artery3 the left commoncarotid artery3 an$ the left subclavian artery:

The superior vena cava)J7C* is seen in the rightparatracheal area3 typically representing the rights(perior me$iastinal conto(r# -n 0#+ to 0#= of peopleitho(t congenital heart $isease3 a left superior venacavais present )=*# " left J7C arises from the (nction ofthe left (g(lar an$ s(bclaian eins an$ traels erticallythro(gh the left me$iastin(m3 (s(ally emptying into thecoronary sin(s3 hich $rains into the right atri(m#

4atients ith a left J7C may also hae a right J7C3 hichis typically smaller than (s(al#

The azygos veinco(rses anterior to the spine3 eitherbehin$ or to the right of the esophag(s3 (ntil it archesanteriorly to oin the posterior all of the J7C# Thea%ygos ein (s(ally remains ithin the me$iastin(m an$occ(pies the right tracheobronchial angle )in the case of

an a%ygos lobe3 the a%ygos ein traerses the l(ng beforeentering the J7C*# The hemiazygos an$ accessoryhemiazygos eins lie against the ertebral bo$ies3posterior to the a%ygos ein# The accessory hemia%ygosein $rains into the left superior intercostal vein3 hicharches aro(n$ the aorta at the (nction of the arch an$the $escen$ing portion3 an$ oins the left brachiocephalicein )this contact ith the aorta forms the socalle$

/6aortic nipple/

occasionally seen on the 4" chestra$iograph*# 7eno(s anatomy is ill(strate$ in 5ig(re 1


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1+# -n patients ith absence of the inferior ena caa)-7C*3 the a%ygos ein forms the eno(s con$(it $rainingthe /6-7C bloo$/ back to the heart )hepatic einsthen $rain into the right atri(m3 not into the -7C*# -n

s(ch cases3 the a%ygos ein ill be ery large3 as seen onthe 4" chest ra$iograph in the tracheobronchial angle3an$ can resemble a$enopathy#

The main pulmonary arteryis anterior an$ to the left ofthe ascen$ing aorta# The left p(lmonary artery archeshigher than the right an$ passes oer the left mainbronch(s#

4#10


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(%+&E #$@. *iagrams of 52lmonary lobes and

segments# A:"nterior ie# ":4osterior ie# 9NL3right (pper lobe 9BL3 right mi$$le lobe 9LL3 rightloer lobe LNL3 left (pper lobe3 LLL3 left loer lobe#


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4#11

(%+&E #$. =aor and minor fiss2res on lateral

chest radiogra5h.The inferior portions of the maorfiss(res )dashed white arrows* an$ the right minorfiss(re )solid white arrows* are shon# They o(tlinethe location of the right mi$$le lobe# The s(periorportions of the maor fiss(res are not ell seen# -t isnot (ncommon that portions of the fiss(res are notis(ali%e$ on normal chest ra$iographs#


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(%+&E #$#B. =inor fiss2re on 'A chest

radiogra5h.The minor fiss(re has a hori%ontal co(rsefrom the right hil(m to the periphery of the right l(ng)arrow*#


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(%+&E #$##. Accessory aygos fiss2re. The

accessory a%ygos fiss(re )solid arrows* creates anaccessory a%ygos lobe# The fiss(re contains the a%ygosein )dashed arrow*3 hich is higher than its (s(allocation in the tracheobronchial angle#


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(%+&E #$#3. %nferior accessory fiss2re. "@ial CTscan shos the right inferior accessory fiss(re )largerarrows*3 hich separates the me$ial from the otherbasilar segments of the right loer lobe3 an$ the leftmaor fiss(re )smaller arrows*#

4#12


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=ediastinal S5aces, Lines, Stri5es,and "orders

The aortopulmonary windowis the space (n$er the aorticarch an$ aboe the left p(lmonary artery# The

(%+&E #$#8. *iagrams of normal !eno2s

anatomy of the thora9. A:5rontal ie# ":Lateralie# 3 ein#


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ligament(m arterios(m )remnant of the $(ct(sarterios(s* an$ rec(rrent laryngeal nere traerse thisspace )a mass in the aortop(lmonary in$o can inolethe rec(rrent laryngeal nere an$ res(lt in hoarseness*#

The subcarinal spaceis inferior to the carina3 bo(n$e$ bythe main bronchi3 an$ is a site here a$enopathy occ(rs#The prevascular spaceis an area anterior to thep(lmonary artery3 ascen$ing aorta3 an$ three maorbranches of the aortic arch# This space lies beteen theto l(ngs an$ is bo(n$e$ anteriorly by the chest all#Where the l(ngs appro@imate3 there is no preasc(larspace b(t rather an anterior (nction line# Within the

preasc(lar space is the left brachiocephalic ein3 internalmammary arteries3 lymph no$es3

thym(s3 an$ phrenic nere# The retrocrural space)aortichiat(s* is the space bo(n$e$ by the $iaphragmatic cr(raan$ the spine# Jtr(ct(res that pass thro(gh this area canbe tho(ght of as the /6bir$s of the me$iastin(m/ .a%ygos ein )/6a%ygoose/ *3 hemia%ygos ein

)/6hemia%ygoose/ *3 an$ thoracic $(ct )/6thoracic$(ck/ *# The esophag(s )/6esophagoose/ * isanother of the bir$s of the me$iastin(m hoeer3 itpasses thro(gh the esophageal hiat(s#

4#1+


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The rightan$ posterior tracheal stripesare forme$ herethe l(ng contacts the trachea to the right an$ posteriorly3an$ they are normally + mm i$e or less# The anterior7unction lineis here the right an$ left l(ngsappro@imate aboe the leel of the heart an$ belo theman(bri(m )5ig# 11,*# -t is compose$ of fo(r layers ofple(ra )both the parietal an$ isceral layers from eachhemithora@*3 may reach the leel of the claicless(periorly3 an$ is not alays ei$ent on chestra$iography beca(se of interening fat an$Oor thym(s#'eiation of the anterior (nction line s(ggests a mass orshift of the me$iastin(m# The posterior 7unction lineishere the to l(ngs meet behin$ the trachea an$ heart#Nnlike the anterior (nction line3 it e@ten$s to the l(ng

apices3 proecting aboe the claicles )5ig# 11=*# -t isalso compose$ of fo(r ple(ral layers3 an$ b(lging of thebor$er is normal only in the area of the a%ygos ein oraortic arch# The azygoesophageal line3 seen on the frontalchest ra$iograph belo the aortic arch3 is here the rightloer lobe makes contact ith the right all of theesophag(s an$ the a%ygos ein as it ascen$s ne@t to theesophag(s# This portion of l(ng is knon as the

azygoesophageal recessan$ the interface is knon as thea%ygoesophageal line# The (pper fe centimeters of thea%ygoesophageal line are alays straight or concaetoar$ the l(ng in a$(lts a cone@ shape in$icates as(bcarinal mass# Paraspinal linesare stripes of soft tiss(e$ensity3 parallel to the left an$ right margins of thespine3 forme$ by the appro@imation of the l(ng ith thespine# They are (s(ally less than 1 cm in i$th# "ortic

tort(osity ill contrib(te to the thickness of the leftparaspinal line#

(%+&E #$#. Anterior 2nction line on 'A chest

radiogra5h)arrows*# !ote that the line $oes note@ten$ aboe the leel of the claicles#


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"boe the aortic arch3 the left paratracheal shadowisca(se$ by the left caroti$ an$ s(bclaian arteries an$ theleft (g(lar ein# The o(ter margin of the left trachealall is almost neer o(tline$ beca(se the trachea is not

contig(o(s ith the l(ng )it is separate$ by the aorta an$great essels*#


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$iaphragm* refers to a thin membrano(s sheet replacinghat sho(l$ be m(scle3 ca(sing a smooth h(mp on theconto(r of the $iaphragm )freI(ently the anterome$ialright $iaphragm*# Total eentration3 more common on the

left than on the right3 res(lts in eleation of the holehemi$iaphragm#

Lateral Chest &adiogra5hWhat follos is an abbreiate$ reie of chest anatomyas seen on the lateral chest ra$iograph# " completereie of the left lateral chest ra$iograph as p(blishe$in 1D by 4roto an$ Jpeckman )D*#

The brachiocephalic )innominate* artery arises anterior tothe tracheal air col(mn# -ts posterior all can be seen asa gentle Jshape$ interface crossing the tracheal aircol(mn# The left brachiocephalic ein often forms ane@traple(ral b(lge behin$ the man(bri(m# The posteriorbor$er of the right brachiocephalic ein an$ the J7C canoccasionally be i$entifie$ c(ring $onar$ in m(ch thesame position an$ $irection as the brachiocephalic artery3

b(t they are sometimes traceable belo the (pper marginof the aortic arch# The cone@ margin of the innominateartery/Eright s(bclaian artery comple@ proects thro(ghthe tracheal air col(mn an$ merges ith the posterioraspect of the right brachiocephalic ein/EJ7C to form asigmoi$shape$ interface#

The co(rse of the trachea is straight or boe$ forar$ in

patients ith aortic tort(osity# The carina is not isible onthe lateral chest ra$iograph# The anterior all of thetrachea is isible in only a minority of people# Theposterior all of the trachea is (s(ally isible3 beca(sel(ng often passes behin$ the trachea3 forming theposterior tracheal stripe )seen in =0 to 0 of a$(lts*#This stripe is normally narroer than + to , mm# -f thereis little or no air in the esophag(s3 this stripe

is forme$ by the f(ll i$th of a collapse$ esophag(s4#1,


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fat occ(pies this space#

The posterior all of the -7C is isible (st before itenters the right atri(m# The ascen$ing aorta proectsslightly s(perior an$ posterior to the right entric(lar

o(tflo tract# These str(ct(res are $isting(ishe$ as$iscrete b(lges on appro@imately 10 of lateral chestra$iographs# The right p(lmonary artery is seen on en$ asa ro(n$ or oal str(ct(re anterior to the bronch(sinterme$i(s# The left p(lmonary artery has an arc(ateconto(r an$ co(rses s(perior an$ then posterior to theorifice of the left (pper lobe bronch(s )it can be likene$to a miniat(ri%e$ ersion of the transerse aortic arch*#

"t the hil(m3 the right (pper lobe bronch(s is s(perior tothe left (pper lobe bronch(s3 an$ the posterior all of thebronch(s interme$i(s is seen as a thin opaI(e stripebeteen the to an$ intersecting the left (pper lobebronch(s# Mften3 only the left (pper lobe bronch(s )an$not the right (pper lobe bronch(s* is seen on the lateralie# The posterior all of the bronch(s interme$i(s

sho(l$ be no thicker than + mm# The most commonca(ses of thickening are p(lmonary e$ema an$ ariationin patient positioning3 b(t malignancy can also res(lt inthickening#

Jeeral metho$s can be (se$ to locali%e the right an$ lefthemi$iaphragms on the lateral chest ra$iograph )5ig# 11?*# Mn the stan$ar$ left lateral chest ra$iograph3 theright ribs are proecte$ behin$ the left an$ appear larger

beca(se of magnification )(nless the patient is not in atr(e left lateral position*# Mccasionally3 the $iaphragmcan be folloe$ o(t to its respectie ribs# The stomachb(bble is (n$er the left hemi$iaphragm )(nless thepatient has sit(s iners(s*# 4athologic processesobsc(ring only one hemi$iaphragm on the 4" ie illconfirm hich $iaphragm is being obsc(re$ by the samepathology on the lateral ie# The right $iaphragm ill

often be seen e@ten$ing more anteriorly than the lefthemi$iaphragm3


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be isible on either frontal or lateral ies or on bothies3 an$ they can be ery large#

9eference stan$ar$s are (se$ in making ($gments ofabnormality either clinically or ra$iologically# A@ternal

reference stan$ar$s are eI(ialent to e@perience# -f yo(see eno(gh e@amples3 yo( ill eent(ally get goo$ at it#This is not m(ch help to the noice# 5o(r types of internalreference stan$ar$s can be (se$ by the noice. time)interal change3 hich allos instant ($gment as toactiity or chronicity* symmetry )paire$ str(ct(res3 s(chas ribs3 sho(l$ look alike* contin((m $ist(rbance)similar str(ct(res3 s(ch as ribs or ertebral bo$ies3

sho(l$ sho a progressie change* an$ ratios )$ensityan$ si%e/$ensity ratios reI(ire a elle@pose$ film3si%e ratios $o not*# Ji%e an$ $ensity ratios are o(tline$ inTable 12# These ratios are for eery$ay (se an$ illI(ickly become instinctie# When all else fails3 rememberthat /6nobo$yGs perfect/ )5ig# 11D*3 neither yo( northe patientH

(%+&E #$#?. -NobodyDs 5erfect/ )co(rtesy of


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&eferences1# "rmstrong 4# !ormal chest# -n. "rmstrong 43 Wilson"P3 'ee 43 ;ansell 'B3 e$s# !maging 0iseases of theChest# 2n$ e$# Jt# Lo(is3 BM. Bosby 1=.21#

2# Pams( P3 Webb W9# Comp(te$ tomography of thetrachea an$ main bronchi# 4emin Roentgenol:

18+18.=1/E?0#

+#

1.CR Anatomy

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