Dr. Sreedhar Rao Associate Professor, Department of Rog Nidan

MODULE 1: Outline

• What is a Chest X-ray (Chest Radiography)? • What are some common uses of the procedure? • How should the patient be prepared? • What does the equipment look like? • How does the procedure work? • How is the procedure performed? • What will patient experience during and after the

procedure? • Who interprets the results? • What are the benefits vs. risks? • What are the limitations of Chest Radiography?

What is a Chest X-ray (Chest Radiography)?

• The chest x-ray is the most commonly performed

diagnostic x-ray examination.

• A chest x-ray makes images of the heart, lungs, airways, blood vessels and the bones of the spine and chest.

• An x-ray (radiograph) is a noninvasive medical test that helps physicians diagnose and treat medical conditions.

• Imaging with x-rays involves exposing a part of the body to a small dose of ionizing radiation to produce pictures of the inside of the body.

• X-rays are the oldest and most frequently used form of medical imaging.

What are some common uses of the procedure?

• The chest x-ray is performed to evaluate the

lungs, heart and chest wall.

A chest x-ray is typically the first imaging test used to help diagnose symptoms such as:

• shortness of breath.

• a bad or persistent cough.

• chest pain or injury.

• fever.

Physicians use the examination to help diagnose or monitor treatment

for conditions such as:

• pneumonia.

• heart failure and other heart problems.

• emphysema.

• lung cancer.

• line and tube placement.

• other medical conditions.

How should the patient be prepared?

• A chest x-ray requires no special preparation. • Patient may be asked to remove some or all of his

clothes and to wear a gown during the exam. • They may also be asked to remove jewelry, removable

dental appliances, eye glasses and any metal objects or clothing that might interfere with the x-ray images.

• Women should always inform their physician and x-ray technologist if there is any possibility that they are pregnant.

• Many imaging tests are not performed during pregnancy so as not to expose the fetus to radiation.

• If an x-ray is necessary, precautions will be taken to minimize radiation exposure to the baby.

What does the equipment look like?

• The equipment consists of a wall-mounted,

box-like apparatus containing the x-ray film or a special plate that records the image digitally and an x-ray producing tube, that is usually positioned about six feet away.

• The equipment may also be arranged with the x-ray tube suspended over a table on which the patient lies.

• A drawer under the table holds the x-ray film or digital recording plate.

Equipment

How does the procedure work?

• X-rays are a form of radiation like light or radio waves.

• X-rays pass through most objects, including the body.

• Once it is carefully aimed at the part of the body being examined, an x-ray machine produces a small burst of radiation that passes through the body, recording an image on photographic film or a special digital image recording plate.

• Different parts of the body absorb the x-rays in varying degrees.

• Dense bone absorbs much of the radiation while soft tissue, such as muscle, fat and organs, allow more of the x-rays to pass through them.

• As a result, bones appear white on the x-ray, soft tissue shows up in shades of gray and air appears black.

• On a chest x-ray, the ribs and spine will absorb much of the radiation and appear white or light gray on the image.

• Lung tissue absorbs little radiation and will appear dark on the image.

• Until recently, x-ray images were maintained as hard film copy (much like a photographic negative).

• Today, most images are digital files that are stored electronically.

• These stored images are easily accessible and are frequently compared to current x-ray images for diagnosis and disease management.

How is the procedure performed?

• Typically, two views of the chest are taken, one from the back and the other from the side of the body as the patient stands against the image recording plate.

• The technologist, an individual specially trained to perform radiology examinations, will position the patient with hands on hips and chest pressed against the image plate.

• For the second view, the patient's side is against the image plate with arms elevated.

PA (Postero-anterior)

FILM

Posterio-anterior view Lateral view

Projection

Exposed in full inspiration and the patient in upright position.

Film is placed anteriorly, X-ray beam passes from posterior aspect to anterior side.

PA view

X-ray beam passes from one lateral to other lateral, and the film is placed at the latter lateral.

Lateral view

• Patients who cannot stand may be positioned lying down on a table for chest x-rays.

• Patient must hold very still and may be asked to keep from breathing for a few seconds while the x-ray picture is taken to reduce the possibility of a blurred image.

• The technologist will walk behind a wall or into the next room to activate the x-ray machine.

• When the examination is complete, patient will be asked to wait until the radiologist determines that all the necessary images have been obtained.

• The chest x-ray examination is usually completed within 15 minutes.

Who interprets the results and how

do I get them? • A radiologist, a physician specifically trained to

supervise and interpret radiology examinations, will analyze the images and send a signed report to primary care or referring physician, who will discuss the results.

• The results of a chest x-ray can be available almost immediately for review by physician.

What are the benefits vs. risks?

Benefits • No radiation remains in a patient's body after an

x-ray examination. • X-rays usually have no side effects in the

diagnostic range. • X-ray equipment is relatively inexpensive and

widely available in emergency rooms, physician offices, ambulatory care centers, nursing homes and other locations, making it convenient for both patients and physicians.

• Because x-ray imaging is fast and easy, it is particularly useful in emergency diagnosis and treatment.

Risks

• There is always a slight chance of cancer from excessive exposure to radiation.

• However, the benefit of an accurate diagnosis far outweighs the risk.

• The effective radiation dose for this procedure varies.

• Women should always inform their physician or x-ray technologist if there is any possibility that they are pregnant.

Radiation Dose • The dose of radiation from a chest x-ray is very

small (0.25 mRad).

• Although this unit of measurement is probably unfamiliar, we all receive approximately 100 mRad (400 times that of a chest x-ray) yearly from cosmic rays and the trace radioactive minerals in rocks and building foundations.

• However, improperly used equipment can markedly increase the radiation dose.

A Word About Minimizing Radiation

Exposure • Special care is taken during x-ray examinations to use the

lowest radiation dose possible while producing the best images for evaluation.

• National and international radiology protection councils continually review and update the technique standards used by radiology professionals.

• State-of-the-art x-ray systems have tightly controlled x-ray beams with significant filtration and dose control methods to minimize stray or scatter radiation.

• This ensures that those parts of a patient's body not being imaged receive minimal radiation exposure.

What are the limitations of Chest

Radiography? • Because some conditions of the chest cannot be

detected on a conventional chest x-ray image, this examination cannot necessarily rule out all problems in the chest.

• For example, small cancers may not show up on a chest x-ray.

• A blood clot in the lungs, a condition called a pulmonary embolism, cannot be seen on chest x-rays.

• Further imaging studies may be necessary to clarify the results of a chest x-ray or to look for abnormalities not visible on the chest x-ray.

MODULE 2: Technique

• Learn the difference between PA vs. AP CXR

• Learn the utility of a lateral decubitus CXR

• Understand the terms inspiration, penetration, and rotation as they apply to determining a technically adequate film

Positioning - Posterioranterior

On the left is a simulated patient in position for a standard PA (posterioranterior) chest x-ray. On the right is a normal PA film.

Positioning - Lateral

On the left is a simulated patient in position for a lateral chest x-ray and on the right is a normal lateral film.

When reading a patient's chest films you should look at both the PA and the lateral films and hang them in this manner (PA on left and lateral on right).

• When using comparison films one should hang old PA then new PA • then new lateral followed by old lateral • View the PA and lateral, • then compare the new PA to old PA, • and finally the new lateral to the old lateral.

Lateral Positioning

• The lateral view is obtained with the left chest against the cassette.

• This diminishes the effect of magnification on the heart.

• Looking carefully at the posterior aspect of the chest on the lateral view, which ribs are left and right? Which is the right/left hemidiaphragm?

Lateral Positioning

The right ribs (red arrows below) are larger due to magnification and usually projected posterior to the left ribs if the patient was examined in a true lateral position. This can be very helpful if there is a unilateral pleural

effusion seen only on the lateral view.

By zooming in on the image you can clearly notice the increased width and posterior location of the right ribs (red arrows) as compared to the

left ribs (blue arrows) on CXR.

The left hemidiaphragm is usually lower than the right. Also, since the heart lies predominantly on the left hemidiaphragm the result on a lateral film is silouhetting

out of the anterior portion of the hemidiaphragm, whereas the anterior right hemidiaphragm remains visible.

Notice how the right diaphragm (red arrows) continues anteriorly, while the left diaphragm disappears (black arrow) because of the silouhetting caused by the heart. Also notice how the right diaphragm at the blue arrows continues past the smaller left ribs and ends at the larger and more posterior right ribs.

Posterioranterior and Lateral

• The standard chest examination consists of a PA (posterioranterior) and lateral chest x-ray.

• The films are read together.

• The PA exam is viewed as if the patient is standing in front of you with their right side on your left.

• The patient is facing towards the left on the lateral view. • Comparison films can be invaluable - Old Gold! If you

have comparison films, the old PA film is displayed adjacent to the new PA film and the old lateral is displayed adjacent to the new lateral.

PA vs AP

Patient in PA (posterioranterior) position.

Note that the x-ray tube is 72 inches away.

Supine AP (anteriorposterior) position, the x-ray tube is 40

inches from the patient.

• PA film on the left compared with a AP supine film on the right.

• The AP shows magnification of the heart and widening of the mediastinum. Whenever possible the patient should be imaged in an upright PA position.

• AP views are less useful and should be reserved for very ill patients who cannot stand erect.

Lateral decubitus position • The patient can also be examined in a lateral

decubitus position.

• This could be helpful to assess the volume of pleural effusion and demonstrate whether a pleural effusion is mobile or loculated.

• You could also look at the nondependent hemithorax to confirm a pneumothorax in a patient who could not be examined erect.

• Additionally, the dependant lung should increase in density due to atelectasis from the weight of the mediastinum putting pressure on it.

• Failure to do so indicates air trapping.

• Left shows a patient in position for a right lateral decubitis position.

• The right is an example of a decubitus film in this case showing a mobile pleural effusion (arrows).

Inspiration

• The patient should be examined in full inspiration.

• This greatly helps the radiologist to determine if there are intrapulmonary abnormalities.

• The diaphragm should be found at about the level of the 8th - 10th posterior rib or 5th - 6th anterior rib on good inspiration.

•A patient can appear to have a very abnormal chest if the film is taken during expiration. - On the first film, the loss of the right heart border silhouette would lead you to the diagnosis of a possible pneumonia. However, the patient had taken a poor inspiration. - On repeat exam with improved inspiration, the right heart border is normal.

Penetration

• Adequate penetration of the patient by radiation is also required for a good film.

• On a good PA film, the thoracic spine disc spaces should be barely visible through the heart but bony details of the spine are not usually seen.

• On the other hand penetration is sufficient that bronchovascular structures can usually be seen through the heart.

• On the lateral view, you can look for proper penetration and inspiration by observing that the spine appears to be darken as you move caudally.

• This is due to more air in lung in the lower lobes and less chest wall.

• The sternum should be seen edge on and posteriorly you should see two sets of ribs.

•

an example of a normal PA film that is underpenetrated.

an overpenetrated PA film.

Rotation

• The technologists are usually very careful to x-ray the patient flat against the cassette.

• If there is rotation of the patient, the mediastinum may look very unusual.

• One can access patient rotation by observing the clavicular heads and determining whether they are equal distance from the spinous process of the thoracic vertebral bodies.

Normal PA film without any rotation.

• Magnification of clavicular head and spinous process alignment demonstrating a straight film.

In this rotated film skin folds can be mistaken for a tension pneumothorax (blue arrows).

Notice the skewed positioning of the heads of the clavicles (red arrows) and the spinous processes.

Opacity

Mass vs. Infiltrate

In each of the cases above, there is an abnormal opacity in the left upper lobe. In the case on the left, the opacity would best be described as a mass because it is well-defined. The case on the right has an opacity that is poorly defined. This is airspace disease such as pneumonia.

The basic diagnostic instance is to detect an abnormality. In both of the cases above, there is an abnormal opacity. It is most useful to state the diagnostic findings as specifically as possible, then try to put these together and construct a useful differential diagnosis using the clinical information to order it.

MODULE 3: Anatomy

• Learn the basic anatomy of the fissures of the lungs, heart borders, bronchi, and vasculature that can be seen on a chest x-ray

Lobes and Fissures On the PA chest x-ray, the minor fissure divides the right middle lobe from

the right upper lobe and is sometimes not well seen. There is no minor

fissure on the left. The major fissures are usually not well seen on the PA

view because you are looking through them obliquely. If there is fluid in the

fissure, it is occasionally manifested as a density at the lower lateral margin.

The left image shows the right minor fissure (A) and the inferior borders (B) of the major fissures bilaterally. The right image shows the superior border of the major fissures (B) bilaterally.

On the lateral view, both lungs are superimposed. Think about them separately, the left lung has only a major fissure as shown.

The right lung will have both the major and minor fissure.

The patient above has a pleural effusion extending into the fissure. Which fissure is which?

Mediastinum and Lungs

• The radiologist needs to know both the structures within the mediastinum forming the mediastinal margins and the lobes of the lungs forming the margins of the lungs along the mediastinum and chest wall.

• If a mass or pneumonia "silhouettes" (obscures) a part of the lung/mediastinal margin, the radiologist should be able to identify what part of the lung and what organ within the mediastinum are involved.

• The margins of the mediastinum are made up of the structures shown below. Trace the margin of the mediastinum with your eye all the way around the margin.

• Think of the mediastinal structures that comprise this interface.

• If the margin were abnormal you could diagnose the cause.

Specific anatomy of the PA chest x-ray.

The locations of each lung margin on chest x-ray.

Trace the margin of the lung with your eye in the image below thinking about what mediastinal structure and what lobe of the

lung is present at this margin.

Bronchi

A = Right Main Stem Bronchus B = Right Upper Lobe Bronchus B1 = Apical Segmental Bronchus B2 = Anterior Segmental Bronchus B3 = Posterior Segmental Bronchus C = Bronchus Intermedius D = Right Middle Lobe Bronchus D4 = Lateral Segmental Bronchus D5 = Medial Segmental Bronchus E = Right Lower Lobe Bronchus E6 = Superior Segmental Bronchus E7 = Medial Basal Segmental Bronchus E8 = Anterior Basal Segmental Bronchus E9 = Lateral Basal Segmental Bronchus E10 = Posterior Basal Segmental Bronchus F = Left Main Stem Bronchus G = Left Upper Lobe Bronchus G1, G2 = Apicoposterior Segmental Bronchus G3 = Anterior Segmental Bronchus H = Lingular Bronchus H4 = Superior Lingular Segmental Bronchus H5 = Inferior Lingular Segmental Bronchus I = Left Lower Lobe Bronchus I6 = Superior Segmental Bronchus I7 = Medial Basal Segmental Bronchus I8 = Anterior Basal Segmental Bronchus I9 = Lateral Basal Segmental Bronchus I10 = Posterior Basal Segmental Bronchus SMALP = "Suppose My Aunt Loves Peaches" is a helpful way to remember the segmental lower lobe bronchi.

Pulmonary Vasculature • The following drawings show the major pulmonary vessels

within the mediastinum. The bronchi that you have already learned are the same as on the prior drawing. These structures are obviously present on every chest x-ray but are usually unrecognized.

MODULE 4: How to Read a Chest X-Ray

MODULE 4: How to Read a Chest X-Ray

• Turn off stray lights, optimize room lighting, view images in order

• Patient Data (name history #, age, sex, old films) • Routine Technique: AP/PA, exposure, rotation, supine or

erect • Trachea: midline or deviated, caliber, mass • Lungs: abnormal shadowing or lucency • Pulmonary vessels: artery or vein enlargement • Hila: masses, lymphadenopathy • Heart: thorax: heart width > 2:1 ? Cardiac configuration? • Mediastinal contour: width? mass? • Pleura: effusion, thickening, calcification • Bones: lesions or fractures • Soft tissues: don’t miss a mastectomy

Looking for abnormalities • It is best to do a directed search of the chest film rather than

simply gazing at the film. • An abnormality will not likely hit you over the head. • Remember that detail vision is only permitted at the fovea

centralis of your retina. • This area contains only cones and is the part that you use to

read. • The remainder of the retina helps you to put this detailed

portion in context and helps to determine whether this is a saber tooth tiger sneaking up on you.

• Therefore, it is best to look for abnormalities and to have a planned search in mind.

• Your eye gaze should scan all portions of the film, follow lung/mediastinal interfaces and look again carefully in areas where you know that mistakes are easily made, such as over the spine on the lateral view and in the apex on the PA view.

The diagrams depict the human eye and light waves hitting the fovea, the

area of detailed vision.

Stare at the 'X' in the center of the image above. Note how you cannot read the letters in the corner unless you are looking directly at them (ie unless the letter you

are trying to read is hitting your retina at the fovea).

PA technique for looking at films. Encompassing the entire lung boundaries (left), scanning with fovea over each part of lung (right).

Lateral scanning technique

Signs

Silhouette sign • One of the most useful signs in chest radiology is

the silhouette sign. • This was described by Dr. Ben Felson. • The silhouette sign is in essence elimination of

the silhouette or loss of lung/soft tissue interface caused by a mass or fluid in the normally air filled lung.

• In other words, if an intrathoracic opacity is in anatomic contact with, for example, the heart border, then the opacity will obscure that border.

• The sign is commonly applied to the heart, aorta, chest wall, and diaphragm.

• The location of this abnormality can help to determine the location anatomically.

• For the heart, the silhouette sign can be caused by an opacity in the RML, lingula, anterior segment of the upper lobe, lower aspect of the oblique fissure, anterior mediastinum, and anterior portion of the pleural cavity.

• This contrasts with an opacity in the posterior pleural cavity, posterior mediastinum, of lower lobes which cause an overlap and not an obliteration of the heart border.

• Therefore both the presence and absence of this sign is useful in the localization of pathology.

The right heart border is silhouetted out. This is caused by a pneumonia, can you determine which lobe the pneumonia affects?

Air Bronchogram • An air bronchogram is a tubular outline of an

airway made visible by filling of the surrounding alveoli by fluid or inflammatory exudates.

Six causes of air bronchograms are;

1. lung consolidation,

2. pulmonary edema,

3. nonobstructive pulmonary atelectasis

4. severe interstitial disease,

5. neoplasm, and

6. normal expiration.

This patient has bilateral lower lobe pulmonary edema. The alveoli are filled with fluid making the bronchi visible as an air

bronchogram. The upper right is a closeup of the right side of the film with arrows outlining a prominent air bronchogram. The lower right is

a CT scan demonstrating an air bronchogram clearly.

Solitary Pulmonary Nodule

• A solitary nodule in the lung can be potentially a fatal lung cancer.

• After detection the initial step in analyis is to compare the film with prior films if available.

• A nodule that is unchanged for two years is almost certainly benign.

• If the nodule is completely calcified or has central or stippled calcium it is benign.

• Nodules with irregular calcifications or those that are off center should be considered suspicious, and need to be worked up further with a biopsy.

• PA and Lateral of a subtle right lower lobe cancer.

• Can you find it in the frontal projection?

Atelectasis • Atelectasis is collapse or incomplete expansion of

the lung or part of the lung.

• This is one of the most common findings on a chest x-ray.

• It is most often caused by an endobronchial lesion, such as mucus plug or tumor.

• It can also be caused by extrinsic compression centrally by a mass such as lymph nodes or peripheral compression by pleural effusion.

• An unusual type of atelectasis is cicatricial and is secondary to scarring, TB, or status post radiation.

Atelectasis • Atelectasis is almost always associated with a linear

increased density on chest x-ray.

• The apex tends to be at the hilum.

• The density is associated with volume loss.

• Some indirect signs of volume loss include vascular crowding or fissural, tracheal, or mediastinal shift, towards the collapse.

• There may be compensatory hyperinflation of adjacent lobes, or hilar elevation (upper lobe collapse) or depression (lower lobe collapse).

• Segmental and subsegmental collapse may show linear, curvilinear, wedge shaped opacities.

• This is most often associated with post-op patients and those with massive hepatosplenomegaly or ascites .

Note the loss of the right heart border silhouette due to partial atelectasis of the RML. Atelectasis is usually, but not always, a

benign finding as in this example which was caused by an endobronchial mass in the RML.

This is a PA and lateral film showing round atelectasis, where the lung becomes attached to the chest wall by an area of previous inflammation. The

lung then rolls up, causing this opacity.

Left Lung Atelectasis Left Upper Lobe

• The left lung lacks a middle lobe and therefore a minor fissure, so left upper lobe atelectasis presents a different picture from that of the right upper lobe collapse.

• The result is predominantly anterior shift of the upper lobe in left upper lobe collapse, with loss of the left upper cardiac border.

• The expanded lower lobe will migrate to a location both superior and posterior to the upper lobe in order to occupy the vacated space.

• As the lower lobe expands, the lower lobe artery shifts superiorly.

• The left mainstem bronchus also rotates to a nearly horizontal position.

This patient suffered from left upper lobe atelectasis following right upper lobectomy.

Left Lower Lobe • Atelectasis of either the right or left lower lobe

presents a similar appearance.

• Silhouetting of the corresponding hemidiaphragm, crowding of vessels, and air bronchograms are sometimes seen, and silhouetting of descending aorta is seen on the left.

• It is important to remember that these findings are all nonspecific, often occuring in cases of consolidation, as well.

• A substantially collapsed lower lobe will usually show as a triangular opacity situated posteromedially against the mediastinum.

These radiographs demonstrate left lower lobe atelectasis followed by partial resolution,

respectively.

Right Lung Atelectasis

Right Upper Lobe

• Right upper lobe atelectasis is easily detected as the lobe migrates superomedially toward the apex and mediastinum.

• The minor fissure elevates and the inferior border of the collapsed lobe is a well demarcated curvilinear border arcing from the hilum towards the apex with inferior concavity.

• Due to reactive hyperaeration of the lower lobe, the lower lobe artery will often be displaced superiorly on a frontal view.

Note the elevation of the horizontal fissure (arrows) caused by RUL atelectasis.

Right Middle Lobe

• Right middle lobe atelectasis may cause minimal changes on the frontal chest film.

• A loss of definition of the right heart border is the key finding.

• Right middle lobe collapse is usually more easily seen in the lateral view.

• The horizontal and lower portion of the major fissures start to approximate with increasing opacity leading to a wedge of opacity pointing to the hilum.

• Like other cases of atelectasis, this collapse may by confused with right middle lobe pneumonia.

- Right middle lobe atelectasis can be difficult to detect in the AP film. - The right heart border is indistinct on the AP film. - The lateral, though, shows a marked decrease in the distance between the horizontal and oblique fissures.

Right Lower Lobe

• Silhouetting of the right hemidiaphragm and a triangular density posteromedially are common signs of right lower lobe atelectasis.

• Right lower lobe atelectasis can be distinguished from right middle lobe atelectasis by the persistance of the right heart border.

Notice the stretched vessels in the hyperexpanded right upper lobe in right lower lobe atelectasis. The right hilum is

also displaced inferiorly. This is a tough one.

Pulmonary Edema

• There are two basic types of pulmonary edema.

• One is cardogenic edema caused by increased hydrostatic pulmonary capillary pressure.

• The other is termed noncardogenic pulmonary edema, and is caused by either altered capillary membrane permeability or decreased plasma oncotic pressure.

• A helpful mnemonic for noncardiogenic pulmonary edema is NOT CARDIAC (near-drowning, oxygen therapy, transfusion or trauma, CNS disorder, ARDS, aspiration, or altitude sickness, renal disorder or resuscitation, drugs, inhaled toxins, allergic alveolitis, contrast or contusion.

X-ray findings

• On a CXR, cardiogenic pulmonary edema can show; cephalization of the pulmonary vessels, peribronchial cuffing, "bat wing" pattern, patchy shadowing with air bronchograms, and increased cardiac size.

• Unilateral, miliary and lobar or lower zone edema are considered atypical patterns of cardiac pulmonary edema.

• A unilateral pattern may be caused by lying preferentially on one side.

• Unusual patterns of edema may be found in patients with COPD who have predominant upper lobe emphysema.

PA film of a patient with pulmonary edema showing cephalization of pulmonary veins and indistinctness

of the vascular margins. The heart is enlarged.

Would you favor pneumonia or CHF in this patient? Why? What pattern is shown?

Congestive Heart Failure

• Congestive heart failure (CHF) is one of the most common abnormalities evaluated by CXR.

• CHF occurs when the heart fails to maintain adequate forward flow.

• CHF may progress to pulmonary venous hypertension and pulmonary edema with leakage of fluid into the interstitium, alveoli and pleural space.

• The earliest CXR finding of CHF is cardiomegaly, detected as an increased cardiothoracic ratio (>50%).

• In the pulmonary vasculature of the normal chest, the lower zone pulmonary veins are larger than the upper zone veins due to gravity.

• In a patient with CHF, the pulmonary capillary wedge pressure rises to the 12-18 mmHg range and the upper zone veins dilate and are equal in size or larger, termed cephalization.

• Often in a classic perihilar bat wing pattern of density.

• Pleural effusions also often occur.

X-ray Findings

This is a typical chest x-ray of a patient in severe CHF. Note the cardiomegaly, alveolar edema, and haziness of

vascular margins.

Kerley B lines • These are horizontal lines less than 2cm long,

commonly found in the lower zone periphery.

• These lines are the thickened, edematous interlobular septa.

• Causes of Kerley B lines include; pulmonary edema, lymphangitis carcinomatosa and malignant lymphoma, viral and mycoplasmal pneumonia, interstital pulmonary fibrosis, pneumoconiosis, sarcoidosis.

• They can be an evanescent sign on the CXR of a patient in and out of heart failure.

The patient above is suffering from congestive heart failure resulting in interstitial edema.

Notice the Kerley's B lines in right periphery (arrows).

Pneumonia

• Pneumonia is airspace disease and consolidation.

• The air spaces are filled with bacteria or other microorganisms and pus.

• Other causes of airspace filling not distinguishable radiographically would be fluid (inflammatory), cells (cancer), protein (alveolar proteinosis) and blood (pulmonary hemorrhage), Pneumonia is NOT associated with volume loss.

• Pneumonia is caused by bacteria, viruses, mycoplasmae and fungi.

X-ray findings

• Airspace opacity, lobar consolidation, or interstitial opacities.

• There is usually considerable overlap.

• Again, pneumonias is a space occupying lesion without volume loss.

• What differentiates it from a mass? Masses are generally more well-defined.

• Pneumonia may have an associated parapneumonic effusion.

Major differentiating factors between atelectasis and pneumonia

Atelectasis Pneumonia

Volume Loss

Associated Ipsilateral Shift

Linear, Wedge-Shaped

Apex at Hilum

Normal or Increased Volume

No Shift, or if Present Then Contralateral

Consolidation, Air Space

Process

Not Centered at Hilum

Air bronchograms can occur in both.

These are PA and lateral films of RML pneumonia (arrows). Note the indistinct borders, air bronchograms, and

silhouetting of the right heart border.

Tuberculosis • Primary tuberculosis (TB) is the initial infection

with Mycobacterium tuberculosis.

• Post-primary TB is reactivation of a primary focus, or continuation of the initial infection.

• Radiographically, TB is represented by consolidation, adenopathy, and pleural effusion.

• A Ghon focus is an area of consolidation that most commonly occurs in the mid and lower lung zones.

• A Ghon complex is the addition of hilar adenopathy to a Ghon focus.

Radiographic features

• Focal patchy airspace disease "cotton wool" shadows, cavitation, fibrosis, nodal calcification, and flecks of caseous material.

• These occur most commonly in the posterior segments of the upper lobes, and superior segments of the lower lobes.

• Endobronchial TB involves the wall of a major bronchus.

• Complications of endobronchial TB are cicatrical stenosis and obstruction.

This is a PA film of a patient who has had tuberculosis for years. This shows fibrosis, cavitation, and calcification, particularly in the

left upper lobe.

Pulmonary Hemorrhage

• Pulmonary hemorrhage has an appearance like that of other airspace filling processes (pneumonia, edema) which have opacity often with air bronchograms.

• It is caused by trauma, Goodpastrue's syndrome, bleeding disorders, high altitude, and mitral stenosis.

• Blood fills the bronchi and eventually the alveoli.

• Pulmonary hemorrhage is notable in that it may clear more quickly than other alveolar densities such as pneumonia.

PA and Lateral films of a patient with right upper lobe hemorrhage. Notice the large pleural effusion

in the left hemithorax.

Pleural Effusion • Common causes for a pleural effusion are CHF, infection

(parapneumonic), trauma, PE, tumor, autoimmune disease, and renal failure.

• On an upright film, an effusion will cause blunting on the lateral and if large enough, the posterior costophrenic sulci.

• Sometimes a depression of the involved diaphragm will occur.

• A large effusion can lead to a mediastinal shift away from the effusion and opacify the hemothorax.

• Approximately 200 ml of fluid are needed to detect an effusion in the frontal film vs. approximately 75ml for the lateral.

• Larger effusions, especially if unilateral, are more likely to be caused by malignancy than smaller ones.

• In the supine film, an effusion will appear as a graded haze that is denser at the base.

•

• The vascular shadows can usually be seen through the effusion.

• An effusion in the supine view can veil the lung tissue, thicken fissure lines, and if large, cause a fluid cap over the apex.

• There may be no apparent blunting of the lateral costophrenic sulci.

• A lateral decubitis film is helpful in confirming an effusion in a bedridden patient as the fluid will layer out on the affected side (unless the fluid is loculated).

• Today, ultrasound is also a key component in the diagnosis.

• Ultrasound is also used to guide diagnostic aspiration of small effusions.

PA and lateral film of a patient with bilateral pleural effusions.

Note the concave menisci blunting both posterior costophrenic angles.

Pneumothorax • A pneumothorax is defined as air inside the thoracic cavity but outside the

lung.

• A spontaneous pneumothorax (PTX) is one that occurs without an obvious inciting incident.

• Some causes of spontaneous PTX are; idiopathic, asthma, COPD, pulmonary infection, neoplasm, Marfan's syndrome, and smoking cocaine.

• However, most pneumothoraces are iatrogenic and caused by a physician during surgery or central line placement.

• Trauma, such as a motor vehicle accident is another important cause.

• A tension PTX is a type of PTX in which air enters the pleural cavity and is trapped during expiration usually by some type of ball valve-like mechanism.

• This leads to a buildup of air increasing intrathoracic pressure.

• Eventually the pressure buildup is large enough to collapse the lung and shift the mediastinum away from the tension PTX.

• If it continues, it can compromise venous filling of the heart and even death.

X-ray findings • On CXR, a PTX appears as air without lung markings in the

least dependant part of the chest. • Generally, the air is found peripheral to the white line of the

pleura. • In an upright film this is most likely seen in the apices. • A PTX is best demonstrated by an expiration film. • It can be difficult to see when the patient is in a supine

position. • In this position, air rises to the medial aspect of the lung and

may be seen as a lucency along the mediastinum. • It may also collect in the inferior sulci causing a deep sulcus

sign. • A hydropneumothorax is both air and fluid in the pleural

space. • It is characterized by an air-fluid level on an upright or

decubitus film in a patient with a pneumothorax. Some causes of a hydropneumothorax are trauma, thoracentesis, surgery, ruptured esophagus, and empyema.

The above film shows a right sided tension pneumothorax with right sided lucency and leftward mediastinal shift. This is a medical

emergency. Failure to place a right chest tube immediately could allow venous return to diminish and lead to possible death.

Left is a supine view of a PTX, note the medial position of the air. Right is an image demonstrating the deep sulcus sign (letter D in the

image) in supine views of a PTX.

The above three images show a hydropneumothorax in three different views.

The PA, lateral, and right decube reveal a layering out of the air and fluid.

The right decube film demonstrates a right hydropneumothorax. Note the pleural air/fluid level demonstrated by the horizontal

air/fluid interface (arrows).

Emphysema

• Emphysema is loss of elastic recoil of the lung with destruction of pulmonary capillary bed and alveolar septa.

• It is caused most often by cigarette smoking

• Functional hallmarks are decreased airflow and diffusing capacity.

X-ray findings

• Emphysema is commonly seen on CXR as diffuse hyperinflation with flattening of diaphragms, increased retrosternal space.

• Hyperinflation and bullae are the best radiographic predictors of emphysema.

• However, the radiographic findings correlate poorly with the patientâs pulmonary function tests.

Note bilateral flattening of the diaphragms and significant hyperinflation as demonstrated by

visualization of 11 posterior ribs.

Pericardial Effusion • Pericardial effusion causes an enlarged heart shadow that is

often globular shaped (transverse diameter is disproportionately increased).

• A "fat pad" sign, a soft tissue stripe wider than 2mm between the epicardial fat and the anterior mediastinal fat can be seen anterior to the heart on a lateral view.

• Serial films can be helpful in the diagnosis especially if rapid changes in the size of the heart shadow are observed.

• Approximately 400-500 ml of fluid must be in the pericardium to lead to a detectable change in the size of the heart shadow on PA CXR.

• Pericardial effusion can be definitively diagnosed with either echocardiography or CT.

• It can be critical to diagnose pericardial effusion because if it is acute it may lead to cardiac tamponade, and poor cardiac filling.

PA of a patient with a pericardial effusion.

A lateral film and closeup of a pericardial effusion showing the anterior mediastinal fat (blue arrows)

and epicardial fat (red arrows) separated by a soft tissue stripe reflecting the pericardial effusion seen edge-on.

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