Showing posts with label chest x ray. Show all posts
Showing posts with label chest x ray. Show all posts

Basics of Chest X Ray Part 3- systematic approach, silhouette sign and Hidden areas in chest Xray

This is the third post in the series, this post deals with the systematic interpretation and analysis of X-ray Chest with special emphasis on silhouette sign and hidden areas of the lung.

Whenever you review a chest x-ray, always use a systematic approach.
We use an inside-out approach from central to peripheral.

First the heart figure is evaluated, followed by mediastinum and hili.
Subsequently the lungs, lungborders and finally the chest wall and abdomen are examined.
You have to know the normal anatomy and variants.

Find subtle abnormalities by using the sihouette sign and mediastinal lines.
Once you see an abnormality use a pattern approach to come up with the most likely diagnosis and differential diagnosis.
Old films
It is extremely important to always compare with old films, as we will demonstrate in this case.
Actually someone said that the most important radiograph is the old film, since it gives you so much information.
For instance a lung mass, which hasn't changed in many years is not a lung cancer.
First study the chest films.
Then continue.
Based on the CXR that you just saw, you could have made the diagnosis of congestive heart failure, but the findings are very subtle.
However once you compare it to the old film, things become more obvious and you will be much more confident in your diagnosis:
1.     The size of the heart is slightly increased compared to the old film.
2.     The pulmonary vessels are slightly increased in diameter indicating increased pulmonary pressure.
3.     There are subtle interstitial markings as a result of interstitial edema.
4.     There is pleural fluid bilaterally. Notice that the inferior border of the lower lobes has changed in position.
All these findings indicate the presence of heart failure.

Silhouette sign

This is a very important sign. It enables us to find subtle pathology and to locate it within the chest.
The loss of the normal silhouette of a structure is called the silhouette sign.
Here an example to explain the silhouette sign:
The heart is located anteriorly in the chest and it is bordered by the lingula of the left lung.
The difference in density between the heart and the air in the lung enables us to see the silhouette of the left ventricle.
When there is something in the lingula with the same 'water density' as the heart, the normal silhouette will be lost (blue arrow).



 When there is a pneumonia in the left lower lobe, which is located more posteriorly in the chest, the left ventricle will still be bordered by air in the lingula and we will still see the silhouette of the heart (red arrow).
The PA-film shows a silhouette sign of the left heart border.

Even without looking at the lateral film, we know, that the pathology must be located anteriorly in the left lung.
This was a consolidation due to a pneumonia caused by Sterptococcus pneumoniae.
Here we see a consolidation which is located in the left lower lobe.
There is a normal silhouette of the left heart border.
On this lateral film there is too much density over the lower part of the spine.

By only looking at the interfaces of the left and right diaphragm on the lateral film, it is possible to tell on which side the pathology is located.
First study the lateral film.
Then continue.
On a normal lateral chest film the silhouette of the left diaphragm 2- can be seen from posterior up to where it is bordered by the heart, which has the same density (blue arrow).

One should be able to follow the contour of the right diaphragm -1- from posterior all the way to anterior, because it is only bordered by the lung.
Here we cannot follow the contour of the right diaphragm all the way to posterior, which indicates that there is something of water-density in the right lower lobe (red arrow).
On the PA-film there is a normal silhouette of the heart border,
so the pathology is not in the anterior part of the chest, which we already suspected by studying the lateral view.
Why do we still see the silhouette of the right diaphragm on the PA-film?
What we see is actually the highest point of the right diaphragm, which is anterior to the pneumonia in the right lower lobe.
The pneumonia does not border the highest point of the diaphragm.

Hidden areas
There are some areas that need special attention, because pathology in these areas can easily be overlooked:
  • apical zones
  • hilar zones
  • retrocardial zone
  • zone below the dome of diaphragm
These areas are also known as the hidden areas.
Notice that there is quite some lung volume below the dome of the diaphragm, which will need your attention (arrow)
Here an example of a large lesion in the right lower lobe,
which is difficult to detect on the PA-film, unless when you give special attention to the hidden areas.
Here a pneumonia which was hidden in the right lower lobe mainly below the level of the dome of the diaphragm (red arrow).

Notice the increase in density on the lateral film in the lower vertebral region.
You may have to enlarge the image to get a better view.
First study the CXR.

Notice the subtle increased density in the area behind 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 extra joint in the anterior part of the first rib which may simulate a mass.
However this is also a hidden area where it can be difficult to detect a mass.
In this case a small lung cancer is seen behind the left first rib.
Notice that is is also seen on the lateral view in the retrosternal area.
Continue with the PET-CT.

The PET-CT demonstrates the tumor (arrow) which has already spread to the bone and liver.


The diagnosis was made by a biopsy of an osteeolytic metastasis in the iliac bone.
First study the CXRs.

There is a subtle consolidation in the left lower lobe in the hidden area behind the heart.

Again there is increased density over the lower vertrebral region.

suggested reading


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BASICS OF CHEST X RAY- PART 2 , EASY WAY TO INTERPRET CXR.

Welcome to basics of CXR, this is part two of this series, read my previous post part 1, in the next post we will be exploring about the silhouette sign and Hidden areas of the lung. You can print this page by clicking on the print option on right side, at the end of this post.

   Chest X-Rays (CXR) are routine investigation in clinical practice and consequently it is important for medical students and clinician’s alike to know how to interpret them. There are many approaches to CXR interpretation, each trying to ensure that key abnormalities are identified and no area is overlooked.
Many people would be familiar with the ABC method to interpreting CXRs.
  • Airways
  • Breathing & Bones
  • Circulation
This is a simple way of approaching CXR, and it works for many people, however some people still struggle using this approach. 
Normal CXR Labelled
DRSABCD is a familiar acronym for those who have undertaken First Aid/Basic Life Support courses. NowDRSABCDE can used as a simple, yet comprehensive, approach to CXR interpretation.

D – Details

Before you even begin interpreting a CXR you should have the correct details. This includes;
  • Patient name, age / DOB, sex
  • Type of film – PA or AP, erect or supine, correct L/R marker, inspiratory/expiratory series
  • Date and time of study

R – RIPE (assessing the image quality)

Next up, how “ripe” is the image. That is, what is the technical quality of the film?
  • Rotation – medial clavicle ends equidistant from spinous process
  • Inspiration – 5-6 anterior ribs in MCL or 8-10 posterior ribs above diaphragm, poor inspiration?, hyperexpanded?
  • Picture – straight vs oblique, entire lung fields, scapulae outside lung fields, angulation (ie ’tilt’ in vertical plane)
  • Exposure (Penetration) – IV disc spaces, spinous processes to ~T4, L) hemidiaphragm visible through cardiac shadow.

S – Soft tissues and bones

In CXR interpretation it is common to leave soft tissues until the end.
  • Ribs, sternum, spine, clavicles – symmetry, fractures, dislocations, lytic lesions, density
  • Soft tissues – looking for symmetry, swelling, loss of tissue planes, subcutaneous air, masses
  • Breast shadows
  • Calcification – great vessels, carotids

A – Airway & mediastinum

  • Trachea – central or slightly to right lung as crosses aortic arch
  • Paratracheal/mediastinal masses or adenopathy
  • Carina & RMB/LMB
  • Mediastinal width <8cm on PA film
  • Aortic knob
  • Hilum – T6-7 IV disc level, left hilum is usually higher (2cm) and squarer than the V-shaped right hilum.
  • Check vessels, calcification.

B – Breathing

  • Lung fields
    • Vascularity – to ~2cm of pleural surface (~3cm in apices), vessels in bases > apices
    • Pneumothorax – don’t forget apices
    • Lung field outlines – abnormal opacity/lucency, atelectasis, collapse, consolidation, bullae
    • Horizontal fissure on Right Lung
    • Pulmonary infiltrates – interstitial vs alveolar pattern
    • Coin lesions
    • Cavitary lesions
  • Pleura
    • Pleural reflections
    • Pleural thickening

C – Circulation

  • Heart position –⅔ to left, ⅓ to right
  • Heart size – measure cardiothoracic ratio on PA film (normal <0.5)
  • Heart borders – R) border is R) atrium, L) border is L) ventricle & atrium
  • Heart shape
  • Aortic stripe

D – Diaphragm

  • Hemidiaphragm levels – Right Lung higher than Left Lung (~2.5cm / 1 intercostal space)
  • Diaphragm shape/contour
  • Cardiophrenic and costophrenic angles – clear and sharp
  • Gastric bubble / colonic air
  • Subdiaphragmatic air (pneumoperitoneum)

E – Extras

  • ETT, CVP line, NG tube, PA catheters, ECG electrodes, PICC line, chest tube
  • PPM, AIDC, metalwork

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Case of the week- Chest Medicine challenge - Answer for Case 1

THE ANSWER FOR FRIDAYS Chest Medicine Challenge is C. Read The complete Rationale. Next Question will be posted on Friday.Bookmark this site for easy access.

A 72-year-old man is admitted for increased shortness of breath, a cough productive of yellow sputum with scant hemoptysis, left pleuritic chest pain, and low-grade fevers. His past medical history is notable for hypertension and diabetes. He has a history of 80 pack-years of tobacco use, and was a ship-yard worker while in the military. On physical examination, his temperature is 38°C and his lung examination reveals decreased breath sounds on the left. His frontal and lateral chest radiographs are shown in Figure 158-A and Figure 158-B. What do you expect to observe on the chest CT scan?
A. Left pleural effusion.
B. Left upper lobe (LUL) consolidation.
C. LUL collapse.
D. Pleural thickening.

Click on the Image to enlarge


Buy Chest X ray Made Easy- Good Book with easy approach for X ray Reading




This patient has developed complete LUL collapse as noted on the CT scan in Figure 158-C (choice C is correct).
Careful review of the plain frontal chest radiograph illustrates the main features of complete LUL collapse. The LUL is bigger than the right upper lobe due to the usual lack of a minor fissure on the left. When the LUL collapses, it tends to collapse anteriorly and somewhat superiorly and medially. On the frontal chest radiograph, there is a left hazy opacity/density in the upper left lung field (see Fig 158-A), which is readily apparent when the upper hemithoraces are compared. Due to volume loss, there is elevation of the left hemidiaphragm, upward retraction of the left hilum, and sometimes tracheal deviation to the left. The left pulmonary artery occupies the AP window. Because the lingula is part of the LUL, it appears as a hazy opacity silhouetting the left heart border, resulting in obscuration of this border.
Sometimes, vessels from the lower lobe can be seen presenting as linear opacities running vertically on the radiograph. The hyperexpanded left lower lobe (LLL) occupies the hemithorax, and the superior segment occupies the apical region of the hemithorax appearing as aerated lung. Sometimes, but not well demonstrated in this patient, there is a portion of the superior segment of the left lower lobe between the mediastinum and the collapsed left upper lobe abutting the arch of the aorta. The luftsichel, or air crescent sign is the name given to the appearance of aerated lung in this area. Alternatively, there may be loss of a discrete left mediastinal border, and obliteration of the aortic contour.
The chest CT scan illustrates the complete LUL collapse, showing the collapse anteriorly and medially with anterior displacement of the left major fissure. An endobronchial cut off sign of the LUL bronchus consistent with obstruction is noted (Fig 158-C, arrow). Bronchoscopy revealed an extrinsic endobronchial lesion, and pathologic findings revealed small cell carcinoma in this patient. The findings of LUL collapse can sometime be confused with pleural thickening because of the density and the nonsegmental borders, but careful review of the other radiographic features suggest LUL collapse (choice D is incorrect). A left pleural effusion, even if loculated, would appear denser, and one would not see superimposed lung markings (choice A is incorrect). Consolidation would appear dense with air bronchograms (choice B is incorrect).
Proto AV. Lobar collapse: basic concepts. Eur J Radiol. 1996;23(1):9-22.
Mintzer RA, Sakowicz BA, Blonder JA. Lobar collapse: usual and unusual forms. Chest. 1988;94(3):615-620.
Woodring JH, Reed JC. Radiographic manifestations of lobar atelectasis. J Thorac Imaging. 1996;11(2):109-144.
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Chest X Ray Part 1- Normal Anatomy And ItsVariants



The chest x-ray is the most frequently requested radiologic examination.
In fact every radiologist and pulmonary physician 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.
PA view
On the PA chest-film it is important to examine all the areas where the lung borders the diaphragm, the heart and other mediastinal structures.
At these borders lung-soft 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.
Widening of the paratracheal line (> 2-3mm) may be due to lymphadenopathy, pleural thickening, hemorrhage or fluid overload and heart failure.
Displacement of the para-aortic line can be due to elongation of the aorta, aneurysm, dissection and rupture.
The anterior and posterior junction lines are formed where the upper lobes join anteriorly and posteriorly. These are usely not well seen and we will not discuss them.
An important mediastinal-lung interface to look for is the azygoesophageal line or recess (arrow).
The azygoesophageal recess is the region inferior to the level of the azygos vein arch in which the right lung forms an interface with the mediastinum between the heart anteriorly and vertebral column posteriorly.
It is bordered on the left by the esophagus.
Deviation of the azygoesophageal line is caused by (5):
  • Hiatal hernia
  • Esophageal disease
  • Left atrial enlargement
  • Subcarinal lymphadenopathy
  • Bronchogenic cyst
·         Notice the deviation of the azygoesophageal line on the PA-film.


·         It is caused by a hiatal hernia.

Vena azygos lobe

A common normal variant is the azygos lobe.
The azygos lobe is created when a laterally displaced azygos vein makes a deep fissure in the upper part of the lung.
On a chest film it is seen as a fine line that crosses the apex of the right lung.
Here another patient with an azygos lobe.

The azygos vein is seen as a thick structure within the azygos fissure.
In some patients an extra joint is seen in the anterior part of the first rib at the point where the bone meets the calcified cartilageneous part (arrow).
This may simulate a lung mass.

Pectus excavatum

In patients with a pectus excavatum the right heart border can be ill-defined, but this is normal.
It produces a silhouette sign and thus simulating a consolidation or atelectasis of the right middle lobe.
The lateral view is helpful in such cases.
Pectus excavatum is a congenital deformity of the ribs and the sternum producing a concave appearance of the anterior chest wall.

Lateral view

On a normal lateral view the contours of the heart are visible and the IVC is seen entering the right atrium.
The retrosternal space should be radiolucent, since it only contains air. Any radiopacity in this area is suspective of a proces in the anterior mediastinum or upper lobes of the lung.
As you go from superior to inferior over the vertebral bodies they should get darker, because usually there will be less soft tissue and more radiolucent lung tissue (red arrow).
If this is not the case, look carefully for pathology in the lower lobes.
The contours of the left and right diaphragm should be visible.

The right diaphragm should be visible all the way to the anterior chest wall (red arrow).
Actually we see the interface between the air in the lungs and the soft tissue structures in the abdomen.
The left diaphragm can only be seen to a point where it borders the heart (blue arrow).
Here the interface is lost, since the heart has the same density as the structures below the diaphragm.
The left main pulmonary artery (in purple)
passes over the left main bronchus and is higher than the right pulmonary artery (in blue) which passes in front of the right main bronchus.
Once you know how the normal hilar structures look like on a lateral view, it is easier to detect abnormalities.

In this case on the PA-view there is hilar enlargement.
On the PA-view it is not clear whether this is due to dilated vessels or enlarged lymph nodes.
On the lateral view there are round structures in areas where you don't expect any vessels. So we can conclude that we are dealing with enlarged lymph nodes.
This patient has sarcoidosis.
Notice also the widening of the paratracheal line (or stripe) as a result of enlarged lymph nodes.
On the lateral view spondylosis may mimick a lung mass.

Any density in the area of the vertebral bodies should lead you to the PA-film to look for spondylosis, which is usually located on the right side (arrows).
On the left side the formation of osteophytes is hampered by the pulsations of the aorta.
On the PA-view the superior mediastinum is widened.

The lateral view is helpful in this case because it demonstrates a density in the retrosternal space.
Now the differential diagnosis is limited to a mass in the anterior mediastinum (4 T's).
This was a Hodgkins lymphoma
A common incidental finding in adults is a Bochdalek hernia, which is due to a congenital defect in the posterior diaphragm (arrows).

In most cases it only contains retroperitoneal fat and is asymptomatic, but occasionally it may contain abdominal organs.
Large hernias are sometimes seen in neonates and can be complicated by pulmonary hypoplasia.
 
A hernia of Morgagni is also a congenital diaphragmatic hernia, but is less common.
It is located anteriorly.
 
other posts in radiology

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