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

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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BASICS OF CHEST X RAY-PART 4, THE HEART AND PERICARDIUM



This is the fourth Post in the series Chest X Ray Interpretation. I personally suggest to read the other three posts before proceeding

 1

    Heart and Pericardium
    On a chest film only the outer contours of the heart are seen.
    In many cases we can only tell whether the heart figure is normal or enlarged and it will be difficult to say anything about the different heart compartments.

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     However it can be helpful to know where the different compartments are situated.
    Left Atrium
        Most posterior structure.
        Receives blood from the pulmonary veins that run almost horizontally towards the left atrium.
        Left atrial appendage (in purple) can sometimes be seen as a small outpouching just below the pulmonary trunk.
        Enlargement of the left atrium results on the PA-view in outpouching of the upper heart contour on the right and an obtuse angle between the right and left main bronchus. On the lateral view bulging of the upper posterior contour will be seen.

    Right Atrium
        Receives blood from the inferior and superior vena cava.
        Enlargement will cause an outpouching of the right heart contour.

    Left Ventricle
        Situated to the left and posteriorly to the right ventricle.
        Enlargement will result on the PA-view in an increase of the heart size to the left and on the lateral view in bulging of the lower posterior contour.

    Right Ventricle
        Most anterior structure and is situated behind the sternum.
        Enlargement will result on the PA-view in an increase of the heart size to the left and can finally result in the left heart border being formed by the right ventricle.
    Left Atrium
        The upper posterior border of the heart is formed by the left atrium.
        Enlargement will result in bulging of the upper posterior contour

    Left Ventricle
        Forms the lower posterior border.
        Enlargement will displace the contour more posteriorly.

    Right Ventricle
        The lower retrosternal space is filled by the right ventricle.
        Enlargement of the right ventricle will result in more superior filling of this retrosternal space.

    Left Atrium enlargement
    This is a patient with longstanding mitral valve disease and mitral valve replacement.
    Extreme dilatation of the left atrium has resulted in bulging of the contours (blue and black arrows).

    Right ventricle enlargement
    First study the PA and lateral chest film and then continue reading.

    On these chest films the heart is extremely dilated.
    Notice that it is especially the right ventricle that is dilated. This is well seen on the lateral film (yellow arrow).

    There is a small aortic knob (blue arrow), while the pulmonary trunk and the right lower pulmonary artery are dilated.
    All these findings are probably the result of a left-to-right shunt with subsequent development of pulmonary hypertension.
    The location of the cardiac valves
    is best determined on the lateral radiograph.
    A line is drawn on the lateral radiograph from the carina to the cardiac apex.
    The pulmonic and aortic valves generally sit above this line and the tricuspid and mitral valves sit below this line .

    On this lateral view you can get a good impression of the enlargement of the left atrium.

    Cardiac incisura
    On the right side of the chest the lung will lie against the anterior chest wall.
    On the left however the inferior part of the lung may not reach the anterior chest wall, since the heart or pericardial fat or effusion is situated there.
    This causes a density on the anteroinferior side on the lateral view which can have many forms.
    It is a normal finding, which can be seen on many chest x-rays and should not be mistaken for pathology in the lingula or middle lobe.

    The explanation for the cardiac incisura is seen on this CT-image.
    At the level of the inferior part of the heart we can appreciate that the lower lobe of the right lung is seen more anteriorly compared to the left lower lobe.

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

    A third lead is seen, which is guided through the coronary sinus towards the left ventricle.
    This is done in patients with asynchrone ventricular contractions.
    Pacing both ventricles at the same time will lead to synchrone contractions and a better cardiac output.


    Pericardial effusion
    Whenever we encounter a large heart figure, we should always be aware of the possibility of pericardial effusion simulating a large heart.

    On the chest x-ray it looks as if this patient has a dilated heart while on the CT it is clear, that it is the pericardial effusion that is responsible for the enlarged heart figure.
    Especially in patients who had recent cardiac surgery an enlargement of the heart figure can indicate pericardial bleeding.

    This patient had a change in the heart configuration and pericardial bleeding was suspected.
    Ultrasound demonstrated only a minimal pericardial effusion.
    Continue with the CT.

    There is a large pericardial effusion, which is located posteriorly to the left ventricle (blue arrow).
    The left ventricle id filled with contrast and is compressed (red arrow).
    At surgery a large hematoma in the posterior part of the pericardium was found.

    Notice that on the anterior side there is only a minimal collection of pericardial fluid, which explains why the ultrasound examination underestimated the amount of pericardial fluid.

    Here another patient who had valve-replacement.

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

    Continue with the CT.
      

    The CT-image shows a large pericardial effusion.

    Always compare these post-operative chest films with the pre-operative ones.

    Calcifications

    Detection of calcifications within the heart is quite common.
    The most common are coronary artery calcifications and valve calcifications.

    Here we see pericardial calcifications which can be associated with constrictive pericarditis.
    In this case there are calcifications that look like pericardial calcifications,
    but these are myocardial calcifications in an infarcted area of the left ventricle.

    Notice that they follow the contour of the left ventricle.

    Pericardial fatpad

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

    Necrosis of the fat pad has pathologic features similar to fat necrosis in epiploic appendagitis.
    It is an uncommon benign condition, that manifests as acute pleuritic chest pain in previously healthy persons.

    Pericardial cyst     
       
                                                                                                                 

     Pericardial cysts are connected to the pericardium and usually contain clear fluid.
    The majority of pericardial cysts arise in the anterior cardiophrenic angle, more frequently on the rightside, but they can be seen as high as the pericardial recesses at the level of the proximal aorta and pulmonary arteries .
    Most patients are asymptomatic.
    On the chest x-ray it seems as if there is a elevated left hemidiaphragm.
    On CT however there is a cyst connected to the pericardium

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