Basic Chest X-Ray Interptation

Positioning

• Typical views – The standard chest examination consists of a PA

(posterioranterior) and lateral chest x-ray.

• Additional views:– Decubitus - useful for differentiating pleural effusions from

consolidation (e.g. pneumonia). In effusions, the fluid layers out (by comparison to an up-right view, when it often accumulates in the costophrenic angles).

– Lordotic view - used to visualize the apex of the lung, to pick-up abnormalities such as a Pancoast tumour.

– Expiratory view - helpful for the diagnosis of pneumothorax – Oblique view

Lateral Decubitus view

Lordotic view

FOR EXAMINATION OF THE LUNG APEX

Expiratory view

FOR DIAGNOSIS OF BRONCHIAL ASTHMA

Normal chest PA

Lung Fissures

Lobes and segments of the lungs.

Drawing of the pleura on the right side, showing the course of the pleura on surface of lung. Only the visceral pleura passes into a normal fissure. The parietal pleura follows the chest wall, except when the course of the azygos vein is abnormal. Both layers of pleura then pass into the fissure, which makes this fissure prominent.

1.Cervical part of parietal pleura 2.Costal part of parietal pleura 3.Mediastinal part of parietal pleura 4.Diaphragmatic part of parietal pleur

1. Heart 2. Fibrous pericardium 3. Parietal layer of serous pericardium 4. Visceral layer of serous pericardium 5. Pericardial space 6. Pleural cavity and lung

1. Superior vena cava 2. Inferior vena cava 3. Right atrium (blue( 4. Right ventricle (blue(5. Left ventricle (red(6. Aorta 7. Pulmonary trunk

Frontal and lateral radiograph of the chest shows mediastinal adenopathy(red arrows) producing lobulated soft tissue masses

Radiograph showing a narrowed trachea secondary to an anterior mediastinal mass

Different tissues in our body absorb X-rays at different extents:

•Bone- high absorption (white)

•Tissue- somewhere in the middle absorption (grey)

•Air- low absorption (black)

How to read the film correctly

Be systematic

1) Check the quality of the film

Film Quality

• First determine is the film a PA or AP view.

PA- the x-rays penetrate through the back of the patient on to the film

AP-the x-rays penetrate through the front of the patient on to the film.

Film Quality (cont)

• Was film taken under full inspiration?

-10 posterior ribs should be visible.

Why do I say posterior here?

When X-ray beams pass through the anterior chest on to the film Under the patient, the ribs closer to the film (posterior) are most apparent.

A really good film will show anterior ribs too, there shouldBe 6 to qualify as a good inspiratory film.

This is A normal X-ray Chest !

Quality (cont.)

• Is the film over or under penetrated if under penetrated you will not be able to see the thoracic vertebrae.

Quality (cont)

• Check for rotation

– Does the thoracic spine align in the center of the sternum and between the clavicles?

– Are the clavicles symmetrical ?

Verify Right and Left sides

• Gastric bubble should be on the left

Gastric bubble

Diphragm

• Look at the diaphram:

for tenting

free air

abnormal elevation• Margins should be

sharp(the right hemidiaphram is usually slightly higher than

the left)

Check the Heart

• Size

• Shape

• Silhouette-margins should be sharp

• Diameter (>1/2 thoracic diameter is enlarged heart)

Remember: AP views make heart appear larger than it

actually is.

Cardio-thoracic Cardio-thoracic RatioRatio

<50%

One of the easiest observations to make is something you already

know: the cardio-thoracic ratio which is the widest

diameter of the heart compared to the widest

internal diameter of the rib cage

Sometimes, CTR is more than 50%But Heart is Normal

� Extra-cardiac causes of cardiac enlargement

� Portable AP films � Obesity � Pregnancy� Ascites � Straight back syndrome � Pectus excavatum

Flat / elevated diaphragm

>50%

Here is a heart that is larger than 50% of the cardiothoracic ratio, but it is still a normal heart. This is because there is an extracardiac cause for the apparent cardiomegaly. On the lateral

film, the arrows point to the inward displacement of the lower sternum in a pectus excavatum deformity.

� Obstruction to outflow of the ventricles � Ventricular hypertrophy

� Must look at cardiac contours

Sometimes, CTR is less than 50%But Heart is Abnormal

<50%

Here is an example of a heart which is less than 50% of the CTR in which the heart is still abnormal. This is recognizable because

there is an abnormal contour to the heart (yellow arrows).

Cardiac Silhouette

1. Superior vena cava 2. Inferior vena cava 3. Right atrium (blue(

4.Right ventricle (blue(5.Left ventricle (red(6.Aorta

7.Pulmonary trunk

Ascending Aorta

“Double density” of LA enlargement

Right atrium Left ventricle

Indentation for LA

Main pulmonary artery

Aortic knob

The Cardiac Contours

There are 7 contours to the heart in the

frontal projection in this system.

Ascending Aorta

“Double density” of LA enlargement

Right atrium Left ventricle

Indentation for LA

Main pulmonary artery

Aortic knob

The Cardiac Contours

But only the top five are really important

in making a diagnosis.

Loss of cardiac boarder

Check the costophrenic angles

Margins should be sharp

Loss of Sharp Costophrenic Angles

Check the Hilar region

• The hilum : – the large blood vessels going to and from the lung at the root of each lung where it meets the heart.

• Check for size and shape of aorta, Lymph nodes, enlarged vessels

Elevated Hilum

Finally, Check the Lung Fields

• Infiltrates

• Increased interstitial markings

• Masses

• Absence of normal margins

• Air bronchograms

• Increased vascularity

Silhouette Sign

� When two objects of the same When two objects of the same density touch each other, the density touch each other, the edge between them disappearsedge between them disappears

A B

Using the Silhouette Sign

� Right middle lobe silhouettes right heart border

� Lingula silhouettes left heart border

� Right lower lobe silhouettes right hemidiaphragm

� Left lower lobe silhouettes left hemidiaphragm

This patient has had the left lung removed – a pneumonectomy. Fibrous tissue now fills the left hemithorax. The heart is “invisible”

Using the Silhouette Sign

The mass (red arrow) silhouettes the right heart border which is to say there is no longer an edge of the right heart seen. That means the mass is (a) touching the right heart border (the mass is anterior) and (b) the mass is the same density as the heart (fluid or soft tissue density). The mass is a thymoma.

Using the Silhouette Sign

Air Bronchogram

� Bronchi are not visible since their walls are thin, they contain air, are surrounded by air

� When something of fluid density fills alveoli, air in bronchus becomes visible, e.g.

� Pulmonary edema fluid � Blood � Gastric aspirate � Inflammatory exudate

Air Bronchogram

� The visibility of air in the bronchi because of surrounding airspace disease is called an “air bronchogram”

� An air bronchogram is almost always a sign of airspace disease

The black branching structures are the result of air in the bronchi, now visible because density other than air surrounds them (in this case it is inflammatory exudate from a pneumonia).

Nodular Infiltrates

Patchy infiltrates

Absence of normal broncho-vascular markings

Masses

Absence of normal margins

Thank You