Download Chest Imaging: Introduction

2014/2015
Hassan Al-Balas, MD
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Imaging modalities in chest evaluation.
Chest pathology:
Lung parenchymal pathology
 Mediastinal pathology.
 Pleural pathology.

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Specific Entities:
Pulmonary edema.
 TB.
 Airway disease.
 Pneumothorax.
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Chest X-Ray:
 PA and Lateral views:
 PA view is obtained with patient in standing position and
in full inspiration.
 Lateral chest view is obtained with left side against the
cassette to minimize cardiac magnification.
 AP view:
 Portable view is obtained with patient in supine or sitting
patient.
 Because of decreased X Ray source patient distance, there
is significant magnification factor.
 Usually obtained in sick patients in ICU and is less useful
than PA view.

Evaluate PA CXR for adequate and proper
technique:
 Penetration:
 Faint visualization of the thoracic disc spaces behind the
cardiac shadow.
 Rotation:
 Thoracic spine process is midway between medial ends of
the clavicles.
 Inspiration:
 Adequate inspiratory film should show the dome of the
diaphragm below the 10th rib posteriorly.

Chest X-Ray:
 Special views:
 Decubitus view:
 Obtained with patient on his lateral side.
 Is used to evaluate:
 Size and possible loculation of the pleural effusion.
 Small pneumothorax in patient an upright CXR is not
possible.
 Air trapping.
 Lordiotic view:
 Obtained with patient leaning backward.
 Useful for evaluation of lung apices.

CT Scan:
 Non-contrast CT:
 Is used to evaluate lung parenchyma, e.g. metastasis.
 Contrast enhanced CT:
 Essential for evaluation of mediastinal and hilar structures.
 High Resolution CT:
 Non contrast thin section images.
 For evaluation of interstitial lung disease.

MRI:
 Very limited value for chest evaluation.

Nuclear Ventilation/ perfusion scans:
 To evaluate for pulmonary embolism.

Angiography:
 Evaluate vascular pathology.
Individual alveoli are
too small to resolve,
but together they
appear radiolucent.
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Air space disease.

Interstitial lung disease.

Focal lung masses/ Nodules.
Filling of alveoli by: water, blood,
pus, proteinaceous fluid or cells
- Ground glass
- Consolidation
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Also known alveolar lung disease.
Features of Airspace disease:
Air bronchogram.
 Respects lobar anatomy.
 Ill-defined borders except at fissures.
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Airspace disease could be:
Partial: Ground glass opacity.
 Complete: Consolidation.
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Causes of ALD:

Acute:
 Pulmonary edema.
 Pneumonias.
 Pulmonary hemorrhage.

Chronic:
 Broncho-alveolar carcinoma.
 Lymphoma.
 Alveolar proteinosis.
- Diffuse and bilateral.
- May have regional distribution.
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Normal interstitium is not seen on CXR unless is
diseased.
Four patterns of interstitial lung disease:
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Linear.
Reticular.
Nodular
Reticulo-nodular
End stage pattern of interstitial lung disease =
honeycombing.
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
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Small sub-pleural cystic changes of the lung parenchyma.
Most prominent in the lower lung lobes.
Nonspecific finding represent end stage ILD secondary to
several underlying pathology.
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Linear pattern:
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Thickened interlobular septa.
Called kerley A and B lines:
 kerley A lines:
 Long lines(2-6cm).
 Centrally located radiating from hila.
 More common in upper and mid lung fields.
 Kerley B lines:
 Short (1-2cm).
 Peripheral sub-pleural location.
 More common in lower lung fields.

Common etiology:
 Pulmonary edema: most common etiology.
 Interstitial pneumonia-viral or mycoplasma.
 Lymphangitis carcinomatosis.
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Reticular pattern:
Result from summation of irregular linear opacities.
 Usually associated with low lung volumes.
 Classic example:

 Idiopathic pulmonary fibrosis.
 Asbestosis.
 Scleroderma.
UIP
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Nodular pattern:
Numerous small nodules (1mm-10mm in diameter).
 Miliary pattern: small nodules 1-2mm in diameter.
 Classic examples:

 Miliary TB.
 Sarcoidosis.
 Silicosis.
 Metastasis from thyroid, kidney, …
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Characterization of focal lung pathology:

Size:
 Nodule(<3cm) vs. mass(>3cm).

Number:
 Single vs. multiple.

Cavitation:
 Presence and thickness of the cavity.

Calcifications:
 Presence and pattern of calcifications.

Margins:
 Rounded vs speculated.
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Bronchogenic carcinoma:

Adenocarcinoma:
 Most common.
 Peripherally located.
 Broncho-alveolar carcinoma is a subtype.

Squamous cell carcinoma:


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Second most common type.
Strong smoking association.
Centrally located.
Most likely to cavitate.
Large cell carcinoma:
 Rare type, peripherally located tumor.

Small cell carcinoma:
 Strong smoking association.
 Centrally located.
 Very poor prognosis.
Hamartoma
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Pleural effusion:


Accumulation of transudate or exudate fluid in the
pleural cavity.
Signs of pleural effusion:
 Blunted costo-phrenic angle.
 Meniscus sign.
 Opacification of hemithorax.

Loculated effusion:
 Usually seen in empyema or malignant effusion.
 Failure of layering on decubitus film.
 CT may show split pleural sign.
Normal R costophrenic angle
Blunted L costophrenic angle
When 200-300cc of fluid accumulate in pleural space, the usually acute
costo-phrenic angle becomes blunted
Meniscus Sign
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Pleural fluid tends to rise higher along its
edge producing a meniscus shape medially
and laterally
Usually only lateral meniscus can be seen
The meniscus is a good indicator of the
presence of a pleural effusion
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DDX:
Total lung collapse/ atelectasis.
 Entire lung consolidation.
 Large pleural effusion.
 Post pneumonectomy.

Opacified hemithorax
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In atelectasis, there is s shift toward the
side of the opacification.
In pleural effusion, there is a shift away
from the side of the opacification.
In pneumonia, there is no shift.
In pneumonectomy, the 5th rib is usually
absent.
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Mediastinal masses can be differentiated from
lung parenchymal lesions by their smooth
contour since they are covered by parietal
pleura.
The mediastinum is divided anatomically into
four compartments:
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Superior.
Anterior.
Middle.
Posterior.
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Superior mediastinum:

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Located between the thoracic inlet and a line
connecting sterno-manubrial joint with T4 body.
DDX of superior mediastinal mass:
 Lesion extending from the neck e.g. thyroid mass,
cystic hygroma.
 Lymphadenopathy.
 Vascular abnormalities e.g. aneurysm.

Anterior mediastinum:
Also known pre-vascular space.
 Located between the stenum anteriorly and
pericardium and great vessels posteriorly.
 It contains lymph nodes and thymus.
 DDX of anterior mediastinal mass are:

 4 T’s
 Thymoma
 Teratoma
 Thyroid
 Terrible lymphoma.
Lymphadenopathy
Thymoma
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Middle mediastinum:
Also known vascular space.
 Located between the anterior and posterior
mediastnum.
 Contains the heart, pericardium, trachea and major
arteries and veins.
 DDX of middle mediastinal masses:

 3 A’s.
 Vascular/ aneurysm.
 Lymphadenopathy.
 Congenital lesions.
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Posterior mediastinum:
Post vascular space.
 Located posterior to the heart and anterior to the
spine.
 Content: descending aorta, esophagus, sympathetic
chains and lymph nodes.
 DDX of posterior mediastinal masses:

 Neurogenic tumors-most common.
 Others e.g. lymphoma, descending aortic aneurysm,
esophageal varices, hiatal hernia,..
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Usually results from congestive heart failure.
It may/ may not be associated with
cardiomegaly.
Other causes of pulmonary edema includes:
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Renal failure.
fluid overload.
Two types of pulmonary edema:
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Interstitial pulmonary edema.
Alveolar pulmonary edema.
Congestive Heart Failure
Four Signs of Pulmonary interstitial edema
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Thickening of the interlobular septa:
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Kerley B lines
Peribronchial cuffing:
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Wall is normally hairline thin
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Thickening of the fissures
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Pleural effusions
Peribronchial Cuffing
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Bronchial wall is usually not visible
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Interstitial fluid accumulates around bronchi
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Causes thickening of bronchial wall
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When seen on end, looks like little “doughnuts”
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Meaningful when seen distal to hilar area
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Fluid in The Fissures
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Fluid collects in the subpleural space
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Between visceral pleura and lung parenchyma
Normal fissure is thickness of a
sharpened pencil line
Fluid may collect in any fissure
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Major, minor, accessory fissures, azygous
fissure
Fluid in the minor fissure
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Congestive Heart Failure
Pulmonary alveolar edema
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Fluffy, indistinct patchy densities
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Outer third of lung frequently spared
n
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Bat-wing or butterfly configuration
Lower lung zones more affected than
upper
Minor fissure
Pulmonary
Edema
154 slides
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Normal cardiothoracic ratio is less than 50%.
Several entities may cause apparent
cardiomegaly:
Portable AP view.
 Obesity.
 Ascites.
 Pectus excavatum.

Cardio-thoracic
Ratio
<50%

Two forms of TB:

Primary:
 Usually is a disease of childhood.
 Usually resolves without trace or may leave Ghon
complex.
 Usually mild consolidation associated with unilateral
hilar and mediastinal lymphadenopathy.

Reactivation TB:
 Ill-defined opacity associated with cavitation and
satellite lesions.
 Affects mostly posterior segment of the upper lobes or
superior segment of the lower lobes.
TB

Includes:

COPD.
 Emphysema.
 Chronic bronchitis.

Bronchiactasis.
 Cystic vs. cylindrical.
 Focal vs. diffuse
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There are two layers of pleura- parietal and visceral-the
pleural space between them .
Normally there is no air in the pleural space.
The visceral pleura is inseparable from the lung parenchyma
and moves with the lung.
When air enters the pleural space, the parietal and visceral
pleura separate making the visceral pleura visible
The thin white line of the visceral pleura is called the
visceral pleural white line
You must see the visceral pleural white line to make
diagnosis of pneumothorax
A pneumothorax
will be visible as a
thin white line - the
visceral pleural
white line
Bullous Emphysema
Enlarged
Retrosternal
Air Space
154 slides
Flattened
Diaphragms
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Skin fold vs. Pneumothorax
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A fold of the patient’s skin may become
trapped between the patient and cassette
Skin folds are common
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Especially in patient’s who have lost a great
deal of weight
This skin fold can mimic a pneumothorax
This is an edge
Dense
Lucent
Skin Fold
The key difference is that a skin fold is an edge
consisting of a density (light) and then a lucency (dark)
This is a line
Lucent
Dense
Lucent
Pneumothorax
Whereas the visceral pleural line is a
thin white line with a lucency (darker) on both sides of it
Skin Fold
Pneumothorax
Types of Pneumothoraces
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Two major types of pneumothorax
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Simple:
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In a simple pneumothorax, there is no shift of the heart or
mediastinal structures (trachea).
Air in left hemithorax balances the air in the right hemithorax.
Tension:
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Progressive loss of air into pleural space causing a shift of the
heart and mediastinal structures away from side of
pneumothorax
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Opposite lung is compressed
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Respiratory function severely compromised
Tension pneumothorax