the radiology assistant : chest x-ray - basic interpretation

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8/6/2014 The Radiology Assistant : Chest X-Ray - Basic Interpretation http://www.radiologyassistant.nl/en/p497b2a265d96d/chest-x-ray-basic-interpretation.html 1/37 PA view On the PA chestfilm it is important to examine all the areas where the lung borders the diaphragm, the heart and other mediastinal structures. At these borders lungsoft tissue interfaces are seen resulting in a: Line or stripe for instance the right para tracheal stripe. Silhouette for instance the normal silhouette of the aortic knob or left ventricle These lines and silhouettes are useful localizers of disease, because they can be displaced or obscured with loss of the normal silhouette. This is called the silhouette sign, which we will discuss later. The paraspinal line may be displaced by a paravertebral abscess, hemorrhage due to a fracture or extravertebral extension of a neoplasm. Publicationdate February 18, 2013 The chest xray is the most frequently requested radiologic examination. In fact every radiologst should be an expert in chest film reading. The interpretation of a chest film requires the understanding of basic principles. In this article we will focus on: Normal anatomy and variants. Systematic approach to the chest film using an insideout approach. Pathology of the heart, mediastinum, lungs and pleura. Chest XRay Basic Interpretation Robin Smithuis and Otto van Delden Radiology Department of the Rijnland Hospital, Leiderdorp and the Academical Medical Centre, Amsterdam, the Netherlands Normal and Variants

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Page 1: The Radiology Assistant : Chest X-Ray - Basic Interpretation

8/6/2014 The Radiology Assistant : Chest X-Ray - Basic Interpretation

http://www.radiologyassistant.nl/en/p497b2a265d96d/chest-x-ray-basic-interpretation.html 1/37

PA view

On the PA chest­film it is important to examineall the areas where the lung borders thediaphragm, the heart and other mediastinalstructures.

At these borders lung­soft tissue interfaces areseen resulting in a:

Line or stripe ­ for instance the right paratracheal stripe.Silhouette ­ for instance the normalsilhouette of the aortic knob or leftventricle

These lines and silhouettes are useful localizersof disease, because they can be displaced orobscured with loss of the normal silhouette.This is called the silhouette sign, which we willdiscuss later.

The paraspinal line may be displaced by aparavertebral abscess, hemorrhage due to afracture or extravertebral extension of aneoplasm.

Publicationdate February 18, 2013

The chest x­ray is the most frequentlyrequested radiologic examination.In fact every radiologst should be an expert inchest film reading.The interpretation of a chest film requires theunderstanding of basic principles.

In this article we will focus on:

Normal anatomy and variants.Systematic approach to the chest filmusing an inside­out approach.Pathology of the heart, mediastinum,lungs and pleura.

Chest X­Ray ­ Basic InterpretationRobin Smithuis and Otto van Delden

Radiology Department of the Rijnland Hospital, Leiderdorp and the Academical Medical Centre,Amsterdam, the Netherlands

Normal and Variants

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Notice the deviation of the azygoesophageal lineon the PA­film.

It is caused by a hiatal hernia.

Widening of the paratracheal line (> 2­3mm)may be due to lymphadenopathy, pleuralthickening, hemorrhage or fluid overload andheart failure.

Displacement of the para­aortic line can be dueto elongation of the aorta, aneurysm, dissectionand rupture.

The anterior and posterior junction lines areformed where the upper lobes join anteriorlyand posteriorly. These are usely not well seenand we will not discuss them.

An important mediastinal­lung interface to lookfor is the azygoesophageal line or recess(arrow).

The azygoesophageal recess is the regioninferior to the level of the azygos vein arch inwhich the right lung forms an interface with themediastinum between the heart anteriorly andvertebral column posteriorly.It is bordered on the left by the esophagus.

Deviation of the azygoesophageal line is causedby (5):

Hiatal herniaEsophageal diseaseLeft atrial enlargementSubcarinal lymphadenopathyBronchogenic cyst

Azygoesophageal recess. The blue arrow indicatesthe paraaortic line.

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Vena azygos lobe

A common normal variant is the azygos lobe.

The azygos lobe is created when a laterallydisplaced azygos vein makes a deep fissure inthe upper part of the lung.

On a chest film it is seen as a fine line thatcrosses the apex of the right lung.

Here another patient with an azygos lobe.The azygos vein is seen as a thick structurewithin the azygos fissure.

In some patients an extra joint is seen in theanterior part of the first rib at the point wherethe bone meets the calcified cartilageneous part(arrow).

This may simulate a lung mass.

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Pectus excavatum

In patients with a pectus excavatum the rightheart border can be ill­defined, but this isnormal.It produces a silhouette sign and thussimulating a consolidation or atelectasis of theright middle lobe.

The lateral view is helpful in such cases.

Pectus excavatum is a congenital deformity ofthe ribs and the sternum producing a concaveappearance of the anterior chest wall.

Lateral view

On a normal lateral view the contours of theheart are visible and the IVC is seen enteringthe right atrium.

The retrosternal space should be radiolucent,since it only contains air. Any radiopacity in thisarea is suspective of a proces in the anteriormediastinum or upper lobes of the lung.

As you go from superior to inferior over thevertebral bodies they should get darker,because usually there will be less soft tissueand more radiolucent lung tissue (red arrow).If this is not the case, look carefully forpathology in the lower lobes.

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The left main pulmonary artery (in purple)passes over the left main bronchus and ishigher than the right pulmonary artery (inblue) which passes in front of the right mainbronchus.

The contours of the left and right diaphragmshould be visible.

The right diaphragm should be visible all theway to the anterior chest wall (red arrow).Actually we see the interface between the air inthe lungs and the soft tissue structures in theabdomen.

The left diaphragm can only be seen to a pointwhere it borders the heart (blue arrow).Here the interface is lost, since the heart hasthe same density as the structures below thediaphragm.

Once you know how the normal hilar structureslook like on a lateral view, it is easier to detectabnormalities.

In this case on the PA­view there is hilarenlargement.On the PA­view it is not clear whether this isdue to dilated vessels or enlarged lymph nodes.On the lateral view there are round structuresin areas where you don't expect any vessels. Sowe can conclude that we are dealing withenlarged lymph nodes.

This patient has sarcoidosis.Notice also the widening of the paratracheal line(or stripe) as a result of enlarged lymph nodes.

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On the lateral view spondylosis may mimick alung mass.

Any density in the area of the vertebral bodiesshould lead you to the PA­film to look forspondylosis, which is usually located on theright side (arrows).On the left side the formation of osteophytes ishampered by the pulsations of the aorta.

On the PA­view the superior mediastinum iswidened.The lateral view is helpful in this case because itdemonstrates a density in the retrosternalspace.Now the differential diagnosis is limited to amass in the anterior mediastinum (4 T's).

This was a Hodgkins lymphoma.

A common incidental finding in adults is aBochdalek hernia, which is due to a congenitaldefect in the posterior diaphragm (arrows).In most cases it only contains retroperitonealfat and is asymptomatic, but occasionally itmay contain abdominal organs.

Large hernias are sometimes seen in neonatesand can be complicated by pulmonaryhypoplasia.

A hernia of Morgagni is also a congenitaldiaphragmatic hernia, but is less common.It is located anteriorly.

Systematic Approach

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Whenever you review a chest x­ray, always usea systematic approach.We use an inside­out approach from central toperipheral.First the heart figure is evaluated, followed bymediastinum and hili.Subsequently the lungs, lungborders and finallythe chest wall and abdomen are examined.

You have to know the normal anatomy andvariants.Find subtle abnormalities by using thesihouette sign and mediastinal lines.Once you see an abnormality use a patternapproach to come up with the most likelydiagnosis and differential diagnosis.

Old films

It is extremely important to always comparewith old films, as we will demonstrate in thiscase.Actually someone said that the most importantradiograph is the old film, since it gives you somuch information.For instance a lung mass, which hasn't changedin many years is not a lung cancer.

First study the chest films.Then continue.

Based on the CXR that you just saw, you couldhave made the diagnosis of congestive heartfailure, but the findings are very subtle.However once you compare it to the old film,things become more obvious and you will bemuch more confident in your diagnosis:

1. The size of the heart is slightly increasedcompared to the old film.

2. The pulmonary vessels are slightlyincreased in diameter indicating increasedpulmonary pressure.

3. There are subtle interstitial markings as a

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The PA­film shows a silhouette sign of the leftheart border.Even without looking at the lateral film, weknow, that the pathology must be locatedanteriorly in the left lung.This was a consolidation due to a pneumoniacaused by Sterptococcus pneumoniae.

Here we see a consolidation which is located inthe left lower lobe.There is a normal silhouette of the left heartborder.

result of interstitial edema.4. There is pleural fluid bilaterally. Notice

that the inferior border of the lower lobeshas changed in position.

All these findings indicate the presence of heartfailure.

Silhouette sign

This is a very important sign. It enables us tofind subtle pathology and to locate it within thechest.The loss of the normal silhouette of a structureis called the silhouette sign.

Here an example to explain the silhouette sign:The heart is located anteriorly in the chest andit is bordered by the lingula of the left lung.The difference in density between the heart andthe air in the lung enables us to see thesilhouette of the left ventricle.When there is something in the lingula with thesame 'water density' as the heart, the normalsilhouette will be lost (blue arrow).

When there is a pneumonia in the left lowerlobe, which is located more posteriorly in thechest, the left ventricle will still be bordered byair in the lingula and we will still see thesilhouette of the heart (red arrow).

Silhouette sign in a consolidation located in thelingula (blue arrow). The silhouette of the leftheart border will still be visible in a consolidationin the left lower lobe (red arrow).

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On this lateral film there is too much densityover the lower part of the spine.

By only looking at the interfaces of the left andright diaphragm on the lateral film, it ispossible to tell on which side the pathology islocated.

First study the lateral film.Then continue.

On a normal lateral chest film the silhouette ofthe left diaphragm 2­ can be seen fromposterior up to where it is bordered by theheart, which has the same density (blue arrow).

One should be able to follow the contour of theright diaphragm ­1­ from posterior all the wayto anterior, because it is only bordered by thelung.

Here we cannot follow the contour of the rightdiaphragm all the way to posterior, whichindicates that there is something of water­density in the right lower lobe (red arrow).

On the PA­film there is a normal silhouette ofthe heart border, so the pathology is not in theanterior part of the chest, which we alreadysuspected by studying the lateral view.

Why do we still see the silhouette of the rightdiaphragm on the PA­film?

What we see is actually the highest point of theright diaphragm, which is anterior to thepneumonia in the right lower lobe.The pneumonia does not border the highestpoint of the diaphragm.

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Hidden areas

There are some areas that need specialattention, because pathology in these areas caneasily be overlooked:

apical zoneshilar zonesretrocardial zonezone below the dome of diaphragm

These areas are also known as the hidden areas.

Notice that there is quite some lung volumebelow the dome of the diaphragm, which willneed your attention (arrow).

Here an example of a large lesion in the rightlower lobe, which is difficult to detect on thePA­film, unless when you give special attentionto the hidden areas.

Click on the image for an enlarged view.

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Here a pneumonia which was hidden in theright lower lobe mainly below the level of thedome of the diaphragm (red arrow).

Notice the increase in density on the lateral filmin the lower vertebral region.

You may have to enlarge the image to get abetter view.

First study the CXR.

Notice the subtle increased density in the areabehind the heart that needs special attention(blue arrow).This was a lower lobe pneumonia.

First study the CXR.

We know that in some cases there is an extrajoint in the anterior part of the first rib whichmay simulate a mass.However this is also a hidden area where it canbe difficult to detect a mass.

In this case a small lung cancer is seen behindthe left first rib.Notice that is is also seen on the lateral view inthe retrosternal area.

Continue with the PET­CT.

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The PET­CT demonstrates the tumor (arrow)which has already spread to the bone and liver.The diagnosis was made by a biopsy of anosteeolytic metastasis in the iliac bone.

First study the CXRs.

There is a subtle consolidation in the left lowerlobe in the hidden area behind the heart.Again there is increased density over the lowervertrebral region.

Heart and Pericardium

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On a chest film only the outer contours of theheart are seen.In many cases we can only tell whether theheart figure is normal or enlarged and it will bedifficult to say anything about the differentheart compartments.However it can be helpful to know where thedifferent compartments are situated.

Left Atrium

Most posterior structure.Receives blood from the pulmonary veinsthat run almost horizontally towards theleft atrium.Left atrial appendage (in purple) cansometimes be seen as a smalloutpouching just below the pulmonarytrunk.Enlargement of the left atrium results onthe PA­view in outpouching of the upperheart contour on the right and an obtuseangle between the right and left mainbronchus. On the lateral view bulging ofthe upper posterior contour will be seen.

Right Atrium

Receives blood from the inferior andsuperior vena cava.Enlargement will cause an outpouching ofthe right heart contour.

Left Ventricle

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Left Atrium enlargement

This is a patient with longstanding mitral valvedisease and mitral valve replacement.

Extreme dilatation of the left atrium hasresulted in bulging of the contours (blue andblack arrows).

Situated to the left and posteriorly to theright ventricle.Enlargement will result on the PA­view inan increase of the heart size to the leftand on the lateral view in bulging of thelower posterior contour.

Right Ventricle

Most anterior structure and is situatedbehind the sternum.Enlargement will result on the PA­view inan increase of the heart size to the leftand can finally result in the left heartborder being formed by the rightventricle.

Left Atrium

The upper posterior border of the heart isformed by the left atrium.Enlargement will result in bulging of theupper posterior contour

Left Ventricle

Forms the lower posterior border.Enlargement will displace the contourmore posteriorly.

Right Ventricle

The lower retrosternal space is filled bythe right ventricle.Enlargement of the right ventricle willresult in more superior filling of thisretrosternal space.

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The location of the cardiac valves is bestdetermined on the lateral radiograph.A line is drawn on the lateral radiograph fromthe carina to the cardiac apex.The pulmonic and aortic valves generally sitabove this line and the tricuspid and mitralvalves sit below this line (4).

On this lateral view you can get a goodimpression of the enlargement of the leftatrium.

Right ventricle enlargement

First study the PA and lateral chest film andthen continue reading.

On these chest films the heart is extremelydilated.Notice that it is especially the right ventriclethat is dilated. This is well seen on the lateralfilm (yellow arrow).

There is a small aortic knob (blue arrow), whilethe pulmonary trunk and the right lowerpulmonary artery are dilated.All these findings are probably the result of aleft­to­right shunt with subsequentdevelopment of pulmonary hypertension.

Cardiac incisura

Click image to enlarge.

On the right side of the chest the lung will lieagainst the anterior chest wall.On the left however the inferior part of the lungmay not reach the anterior chest wall, since theheart or pericardial fat or effusion is situatedthere.

This causes a density on the anteroinferior sideon the lateral view which can have many forms.It is a normal finding, which can be seen onmany chest x­rays and should not be mistaken

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The explanation for the cardiac incisura is seenon this CT­image.At the level of the inferior part of the heart wecan appreciate that the lower lobe of the rightlung is seen more anteriorly compared to theleft lower lobe.

for pathology in the lingula or middle lobe.

PacemakerThere are different types of cardiac pacemakers.Here we see a pacemaker with one lead in theright atrium and another in the right ventricle.

A third lead is seen, which is guided throughthe coronary sinus towards the left ventricle.This is done in patients with asynchroneventricular contractions.Pacing both ventricles at the same time willlead to synchrone contractions and a bettercardiac output.

More on cardiac pacemakers...

Pericardial effusion

Whenever we encounter a large heart figure, weshould always be aware of the possibility ofpericardial effusion simulating a large heart.

On the chest x­ray it looks as if this patient hasa dilated heart while on the CT it is clear, thatit is the pericardial effusion that is responsiblefor the enlarged heart figure.

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Especially in patients who had recent cardiacsurgery an enlargement of the heart figure canindicate pericardial bleeding.

This patient had a change in the heartconfiguration and pericardial bleeding wassuspected.Ultrasound demonstrated only a minimalpericardial effusion.Continue with the CT.

There is a large pericardial effusion, which islocated posteriorly to the left ventricle (bluearrow).The left ventricle id filled with contrast and iscompressed (red arrow).At surgery a large hematoma in the posteriorpart of the pericardium was found.

Notice that on the anterior side there is only aminimal collection of pericardial fluid, whichexplains why the ultrasound examinationunderestimated the amount of pericardial fluid.

Here another patient who had valve­replacement.

Notice the large heart size.There is redistribution of the pulmonary vesselswhich indicates heart failure.

Continue with the CT.

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The CT­image shows a large pericardialeffusion.

Always compare these post­operative chestfilms with the pre­operative ones.

Calcifications

Detection of calcifications within the heart isquite common.The most common are coronary arterycalcifications and valve calcifications.

Here we see pericardial calcifications which canbe associated with constrictive pericarditis.

In this case there are calcifications that look likepericardial calcifications, but these aremyocardial calcifications in an infarcted area ofthe left ventricle.

Notice that they follow the contour of the leftventricle.

Pericardial fatpad

Pericardial fat depositions are common.Sometimes a large fat pad can be seen (figure).

Necrosis of the fat pad has pathologic featuressimilar to fat necrosis in epiploic appendagitis.It is an uncommon benign condition, thatmanifests as acute pleuritic chest pain inpreviously healthy persons (10).

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The normal hilar shadow is for 99% composedof vessels ­ pulmonary arteries and to a lesserextent veins (1).The vessel margins are smooth and the vesselshave branches.

The left pulmonary artery runs over the leftmain bronchus, while the right pulmonaryartery runs in front of the right main bronchus,which is usually lower in position than the leftmain bronchus.

Hence the left hilum is higher than the right.Only in a minority of cases the right hilus is atthe same level as the left, but never higher.

Pericardial cyst

Pericardial cysts are connected to thepericardium and usually contain clear fluid.The majority of pericardial cysts arise in theanterior cardiophrenic angle, more frequentlyon the rightside, but they can be seen as highas the pericardial recesses at the level of theproximal aorta and pulmonary arteries (11).Most patients are asymptomatic.

On the chest x­ray it seems as if there is aelevated left hemidiaphragm.

On CT however there is a cyst connected to thepericardium.

Hili

The left hilum should never be lower than theright hilum.

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In this illustration the lower lobe arteries arecoloured blue because they contain oxygen­poorblood.

They have a more vertical orientation, while thepulmonary veins run more horizontally towardsthe left atrium, which is located below the levelof the main pulmonary arteries.

The lower lobe pulmonary arteries extendinferiorly from the hilum.They are described as little fingers, becauseeach has the size of a little finger (1).

On the right side the little finger will be visiblein 94% of normal CXRs and on the left side in62% of normals (1).

Both pulmonary arteries and veins can beidentified on a lateral view and should not bemistaken for lymphadenopathy.

Sometimes the pulmonary veins can be veryprominent.

The left main pulmonary artery passes over theleft main bronchus and is higher than the rightpulmonary artery which passes in front of theright main bronchus.

These images are thick slab sagittalreconstructions of a chest­ct to get a betterview of the hilar structures.

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Study the CXR of a 70­year old male who fellfrom the stairs and has severe pain on the rightflank..

Notice on the PA­film the absence of the littlefinger on the right and on the lateral view theincreased density over the lower vertebralcolumn.

What is your diagnosis?

There is a right lower lobe atelectasis.

Notice the abnormal right border of the heart.The right interlobar artery is not visible,because it is not surrounded by aerated lungbut by the collapsed lower lobe, which isadjacent to the right atrium.

On a follow­up chest film the atelectasis hasresolved.We assume that the atelectasis was a result ofpost­traumatic poor ventilation with mucusplugging.

Notice the reappearance of the right little finger(red arrow) and the normal right heart border(blue arrow).

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Hilar enlargement

The table summarizes the causes of hilarenlargement.

Normal hili are:

Normal in position ­ left higher than rightEqual densityNormal branching vessels

Enlargement of the hili is usually due tolymphadenopathy or enlarged vessels.

In this case there is an enlarged hilar shadowon both sides.This could be the result of enlarged vessels orenlarged lymph nodes.A very helpful finding in this case is the masson the right of the trachea.

This is known as the 1­2­3 sign in sarcoidosis,i.e. enlargement of left hilum, right hilum andparatracheal.

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Mediastinal masses are discussed in more detailin Mediastinal masses.

Here is just a brief overview.

The mediastinum can be divided into ananterior, middle and posterior compartment,each with it's own pathology.

Here some more examples of sarcoidosis.Click to enlarge.

1. Lymphadenopathy and groundglassappearance of the lungs

2. Lymphadenopathy, 1­2­3 sign3. Bulky lymphadenopathy4. 1­2­3 sign5. Nodular lung pattern, no

lymphadenopathy6. Hilar and paratracheal lymphadenopathy

Mediastinum

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Mediastinal lines

Mediastinal lines or stripes are interfacesbetween the soft tissue of mediastinalstructures and the lung.Displacement of these lines is helpful in findingmediastinal pathology, as we have discussedabove.

Azygoesophageal recess

The most important mediastinal line to look foris the azygoesophageal line, which borders theazygoesophageal recess.

This line is visible on most frontal CXRs.

The causes of displacement of this line aresummarized in the table.

A hiatal hernia is the most common cause ofdisplacement of the azygoesophageal line.

Notice the air within the hernia on the lateralview.

Another common cause of displacement of theazygoesophageal line is subcarinallymphadenopathy.

Notice the displacement of the upper part ofthe azygoesophageal line on the chest x­ray inthe area below the carina.This is the result of massive lymphadenopathyin the subcarinal region (station 7).

There are also nodes on the right of the tracheadisplacing the right paratracheal line.

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On the PET we can appreciate the massivelymphadenopathy far better than on the CXR.

There are also lymphomas in the neck.this is an important finding, since these nodesare accessible for biopsy.

Continue with images of CT and ultrasound.

Here we have a prior CXR of this patient.

The AP­film shows a right paratracheal mass.The azygoesophageal recess is not identified,because it is displaced and parallels the borderof the right atrium.The large round density in the left lung is theresult of aspiration.

Notice the massive dilatation of the esophaguson the CT.

Here we see a CT­image.The azygoesophageal recess is displaced bylymph nodes that compress the left atrium.

The final diagnosis of small cel lungcancer wasmade through a biopsy of a lymphnode in theneck.

First study the chest x­ray.Then continue reading.

Notice the following:

1. There is displacement of theazygoesophageal line both superiorly aninferiorly.

2. There is an air­fluid level (arrow).Combined with the above this must be adilated esophagus with residual fluid. Thefinal diagnosis was achalasia.

3. The density on the left in the region ofthe lingula is the result from prioraspiration pneumonia.

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Aortopulmonary window

The aortopulmonary window is the interfacebelow the aorta and above the pulmonary trunkand is concave or straight laterally.

Here the AP­window is convex laterally due to amass that fills the retrosternal space on thelateral view.

On the CT­images a mass in the anteriormediastinum is seen.

Final diagnosis: Hodgkins lymphoma.

Here another case.On the PA­film a mass is seen that fills theaortopulmonary window.

The PET better demonstrates the extent of thelymphnode metastases in this patient.

Final diagnosis: small cell lungcarcinoma.

Lungs

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Consolidation

Atelectasis

Lung abnormalities mostly present as areas ofincreased density, which can be divided into thefollowing patterns:

1. Consolidation2. Atelectasis3. Nodule or mass ­ solitary or multiple4. Interstitial

Less frequently areas of decreased density areseen as in emphysema or lungcysts.

These lungpatterns will discussed in more detailin an article that will be published soon: ChestX­Ray ­ Lung disease.

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Nodule ­ Masses

Solitary pulmonary node ­ SPN is discussedhere.

Interstitial pattern

Click on the table to enlarge.

Interstitial lung diseases are discussed here.

Pleural fluid

It takes about 200­300 ml of fluid before itcomes visible on an CXR (figure).About 5 liters of pleural fluid are present whenthere is total opacification of the hemithorax.

Pleura

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Total opacification of the right hemithorax in apatient with pleuritis carcinomatosa on bothsides.

On the right there is only some air visible in themajor bronchi creating an air bronchogramwithin the compressed lung.

Pleural fluid may become encysted.

Here we see fluid entrapped within the fissure.This can sometimes give the impression of amass and is called 'vanishing tumor'.

Pneumothorax

The table lists the most common causes of apneumothorax.

The other cystic lungdisease which causespneumothorax is Langerhans cell histiocytosis(LCH) which is seen in smokers.

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Study the CXR.

There are two important findings.

The retracted visceral pleura is seen (bluearrow) which indicates that there is apneumothorax.

There is a horizontal line visible (yellow arrow).Normally there are no straight lines in thehuman body unless when there is an air­fluidlevel.This means that there is a hydro­pneumothorax.

When a pneumothorax is small, this air­fluidlevel can be the only key to the diagnosis of apneumothorax.

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Study the CXR.

There are 3 important findings.

Notice that the mediastinum is slightlydisplaced to the left.Does this mean that there is a tensionpneumothorax?

Do you have an idea about the cause of thepneumothorax?

There is a hydropneumothorax.Notice the air­fluid level (blue arrow).

The upper lobe is still attached to the chest wallby adhesions.Maybe this patient was treated for a priorpneumothorax.

There is a lung cyst in the upper lobe (redarrow).So we can assume that the pneumothorax hassomething to do with a cystic lung disease.

Since this patient is a woman,lymphangioleiomyomatosis (LAM) is a possiblediagnosis.

LAM is a rare lung disease that results in aproliferation of smooth muscle throughout the

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Study the CXR.

What is your diagnosis?

This is not a pneumothorax but a skin fold.

The radiography was performed supine with aCR cassette inserted underneath the patient,which resulted in a skinfold.

Notice that there are lung markings beyond theapparent pneumothorax.

Here two CXRs of another patient with obviousskinfolds.

lungs resulting in the obstruction of smallairways leading to pulmonary cyst formationand pneumothorax.LAM also occurs in patients who have tuberoussclerosis.

Recognition of a pneumothorax depends on thevolume of air in the pleural space and theposition of the body.On a supine radiograph a pneumothorax can besubtle and approximately 30% ofpneumothoraces are undetected.

A sign to look for is the 'deep sulcus sign'.It represents lucency of the lateral costophrenicangle extending toward the hypochondrium(Figure).

The image is of a patient in the ICU who is onmechanical ventilation. There was an acuteexacerbation of the dyspnoe.There is a deep sulcus sign on the left.

Notice that the left hemidiaphragm isdepressed.This is an important finding since it indicates atension pneumothorax.

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The image on the right is after insertion of anintercostal drain.

Notice that the diaphragm has regained itsnormal appearance.

Pleural opacities

The table lists the most common causes ofpleural opacities.

Pleural plaquesThe CXR shows multiple opacities.They have irregular shapes and do not look likea lung masses or consolidations.

Some of these opacities are clearly borderingthe chest wall (red arrows).

All these findings indicate that we are dealingasbestos related pleural plaques.

Asbestos related pleural plaques are usually:

1. bilateral and extensive.2. covering the dome of the diaphragm.

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Unilateral pleural calcifications are usually dueto:

infection (TB)empyemahemorrhagic

Pleural hematomaThese images are of a patient, who had apleural opacity after a chest trauma.

It was believed to be a hematoma and resolvedspontaneously.

Chest wall

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RibfracturesThe most common identified chest wallabnormalities are old ribfractures.

The CXR shows many rib deformities due to oldfracturees.

When a rib fracture heals, the callus formationmay create a mass­like appearance (bluearrow).

Sometimes a CT is necessary to differentiate ahealing fracture from a lung mass.

Notice the large lung volume and the enlargedpulmonary vessels.Probably we are dealing with pulmonary arterialhypertension in a patient with COPD.

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The second most common chest wallabnormalities that we see on a CXR aremetastases in vertebral bodies and ribs.

Notice the expansile mass in the posterior ribon the right.

The most obvious finding on this CXR is free airunder the diaphragm.

This finding indicates a bowel perforation,unless when the patient had recent abdominalsurgery and there is still some air left in theabdomen, which can stay there for several days.

There is another subtle finding in the left upperlobe.A subtle density projecting over the first rib ­hidden area ­ proved to be a lungcarcinoma.

Abdomen

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Here another patient with free abdominal air.

Notice the very thin regular line which is thediaphragm (arrow).

At first impression one might think that this isjust some plate­like atelectasis due to poorinspiration.

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2. introduction to chest radiologyIntroduction to chest radiology

3. Fleischner Society: Glossary of Terms for Thoracic Imagingby David M. Hansell et al Radiology 2008;246:697

4. Lines and Stripes: Where Did They Go? From Conventional Radiography to CTby Jerry M. Gibbs et al RadioGraphics 2007;27:33­48

5. Cardiac Valves: Assessment and Identificationon RadDaily.com

6. A Diagnostic Approach to Mediastinal Abnormalitiesby Camilla R. WhittenMay 2007 RadioGraphics, 27,657­671.

7. The Deep Sulcus SignRadiology 2003; 228:415­416

8. Chest Radiology Plain Film Patterns and Differential Diagnosesby James C. Reed

9. Thoracic Imaging: Pulmonary And Cardiovascular Radiologyby Richard Webb and Charles Higgins

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