Showing posts sorted by relevance for query BASICS OF HRCT INTERPRETATION-PART 2- RETICULAR PATTERN. Sort by date Show all posts
Showing posts sorted by relevance for query BASICS OF HRCT INTERPRETATION-PART 2- RETICULAR PATTERN. Sort by date 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


Posted by
No comments:

BASICS OF CHEST X RAY-PART 5, THE HILUM AND MEDIASTINUM

Hello, Welcome to the fifth part of chest Xray Reading, today we shall know about the hilum and mediastinum
spare time to go through the other posts on chest X ray
Here are the links

The Part 2 has over a lakh views, please go through it.


Hilum
The normal hilar shadow is for 99% composed of vessels - pulmonary arteries and to a lesser extent veins .

The vessel margins are smooth and the vessels have branches.
The left hilum should never be lower than the right hilum.

The left pulmonary artery runs over the left main bronchus, while the right pulmonary artery runs in front of the right main bronchus, which is usually lower in position than the left main bronchus.
Hence the left hilum is higher than the right.
Only in a minority of cases the right hilus is at the same level as the left, but never higher.
In this illustration the lower lobe arteries are coloured blue because they contain oxygen-poor blood.
They have a more vertical orientation, while the pulmonary veins run more horizontally towards the left atrium, which is located below the level of the main pulmonary arteries.
Both pulmonary arteries and veins can be identified on a lateral view and should not be mistaken for lymphadenopathy

Sometimes the pulmonary veins can be very prominent.
The left main pulmonary artery passes over the left main bronchus and is higher than the right pulmonary artery which passes in front of the right main bronchus.

These images are thick slab sagittal reconstructions of a chest-ct to get a better view of the hilar structures.
The lower lobe pulmonary arteries extend inferiorly from the hilum.

They are described as little fingers, because each has the size of a little finger .
On the right side the little finger will be visible in 94% of normal CXRs and on the left side in 62% of normals.
IMPROVE YOUR X RAY READING SKILLS, BUY A BOOK. FIND ALL MEDICAL BOOKS ON FLIPKART WITH GREAT DISCOUNT

 
Study the CXR of a 70-year old male who fell from the stairs and has severe pain on the right flank..
Notice on the PA-film the absence of the little finger on the right and on the lateral view the increased density over the lower vertebral column.
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 lung but by the collapsed lower lobe, which is adjacent to the right atrium.

On a follow-up chest film the atelectasis has resolved.
We assume that the atelectasis was a result of post-traumatic poor ventilation with mucus plugging.
Notice the reappearance of the right little finger (red arrow) and the normal right heart border (blue arrow).

Hilar enlargement

The table summarizes the causes of hilar enlargement.


Normal hili are:
    Normal in position - left higher than right
    Equal density
    Normal branching vessels
Enlargement of the hili is usually due to lymphadenopathy or enlarged vessels.
In this case there is an enlarged hilar shadow on both sides.

This could be the result of enlarged vessels or enlarged lymph nodes.
A very helpful finding in this case is the mass on the right of the trachea.
This is known as the 1-2-3 sign in sarcoidosis, i.e. enlargement of left hilum, right hilum and paratracheal.
Here some more examples of sarcoidosis.

    Lymphadenopathy and groundglass appearance of the lungs
    Lymphadenopathy, 1-2-3 sign
    Bulky lymphadenopathy
    1-2-3 sign
    Nodular lung pattern, no lymphadenopathy
    Hilar and paratracheal lymphadenopathy

Mediastinum


Here is just a brief overview of Mediastinal masses.
The mediastinum can be divided into an anterior, middle and posterior compartment, each with it's own pathology.



Mediastinal lines



Mediastinal lines or stripes are interfaces between the soft tissue of mediastinal structures and the lung.
Displacement of these lines is helpful in finding mediastinal pathology, as we have discussed above.
Azygoesophageal recess



The most important mediastinal line to look for is the azygoesophageal line, which borders the azygoesophageal recess.



 This line is visible on most frontal CXRs.
The causes of displacement of this line are summarized in the table.
A hiatal hernia is the most common cause of displacement of the azygoesophageal line.
Notice the air within the hernia on the lateral view.

 HERE IS A SMALL BUT QUITE INFORMATIVE BOOK ON CHEST X RAY DOCTORS SHOULD READ, THERE IS GOOD COLLECTION OF BOOKS ON FLIPKART

Another common cause of displacement of the azygoesophageal line is subcarinal lymphadenopathy.

Notice the displacement of the upper part of the azygoesophageal line on the chest x-ray in the area below the carina.
This is the result of massive lymphadenopathy in the subcarinal region (station 7).
There are also nodes on the right of the trachea displacing the right paratracheal line.
On the PET we can appreciate the massive lymphadenopathy far better than on the CXR.



There are also lymphomas in the neck.
this is an important finding, since these nodes are accessible for biopsy.
Continue with images of CT and ultrasound.
Here we see a CT-image.


The azygoesophageal recess is displaced by lymph nodes that compress the left atrium.
The final diagnosis of small cel lungcancer was made through a biopsy of a lymphnode in the neck.
First study the chest x-ray.

Then continue reading.
Notice the following:
    There is displacement of the azygoesophageal line both superiorly an inferiorly.
    There is an air-fluid level (arrow).
    Combined with the above this must be a dilated esophagus with residual fluid. The final diagnosis was achalasia.
    The density on the left in the region of the lingula is the result from prior aspiration pneumonia.
Here we have a prior CXR of this patient.



The AP-film shows a right paratracheal mass.
The azygoesophageal recess is not identified, because it is displaced and parallels the border of the right atrium.
The large round density in the left lung is the result of aspiration.
Notice the massive dilatation of the esophagus on the CT.
Aortopulmonary window

The aortopulmonary window is the interface below the aorta and above the pulmonary trunk and is concave or straight laterally.
Here the AP-window is convex laterally due to a mass that fills the retrosternal space on the lateral view.


On the CT-images a mass in the anterior mediastinum is seen.




Final diagnosis: Hodgkins lymphoma.
Here another case.


On the PA-film a mass is seen that fills the aortopulmonary window.

The PET better demonstrates the extent of the lymphnode metastases in this patient.
Final diagnosis: small cell lungcarcinoma.
Posted by
No comments:
Subscribe to: Posts (Atom)