Download evaluation of the chest

RADIOLOGY OF THE CHEST
METHODS OF EXAMINATION
1. Plain Film – The plain chest film is the most common imaging procedure
ordered by the clinician. The routine chest exam consists of PA and lateral
views. Other plain films are: AP, decubitus, lordotic, and oblique views
(RAO, LAO, RPO, and LPO).
2. CT Scanning – CT scanning is helpful in the evaluation of many conditions
involving the chest. It is particularly helpful in the evaluation of mediastinal
mass lesions and in identifying normal structures such as vessels in the
mediastinum, which may be mistaken for abnormalities on plain films. CT
scanning of the lungs is useful in the evaluation of numerous conditions
including: carcinoma, occult metastatic lesions, interstitial lung disease,
bronchiestasis, and pleural abnormalities including pleural fluid and
emphyema. CT scanning for the evaluation of pulmonary embolus has
now become routine for the evaluation of PE and has largely replaced
nuclear medicine and pulmonary angiography. CT scanning of the chest
must follow a protocol tailored for the evaluation of a specific problem
such as pulmonary embolus or interstitial lung disease
3. Angiography
a. Pulmonary angiography – Has been the gold standard for the
diagnosis of pulmonary embolus but has more recently been largely
replaced by CT scanning. Angiography may be helpful in the
evaluation of vascular lesions such as pulmonary AV
malformations.
b. Thoracic aortography – Helpful in distinguishing vascular lesions of
the mediastinum such as aneurysms, pseudocoarctation, traumatic
rupture of the aorta, etc.
4. Nuclear Scanning – helpful in the diagnosis of pulmonary embolus.
5. MRI – has a limited role in the evaluation of the chest. It may be useful in
the evaluation of mediastinal abnormalities and the heart.
PLAIN FILM VIEWS
1. PA – posterior anterior. This view is usually obtained at a 6 foot target to
film distance in order to reduce magnification. With this view, the film is
against the anterior aspect of the patient and the x-ray beam is directed
toward the posterior aspect of the patient.
2. Lateral – a view of the patient’s sagittal plane.
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3. AP – anterior posterior. The film is against the posterior aspects of the
patient and the x-ray beam is directed toward the anterior aspect of the
chest. This is the view commonly obtained with portable technique and the
target to film distance is usually 40 inches. The cardiac silhouette is
magnified in this projection.
4. Decubitus View - This film is obtained with the patient on the side and is
named for the side which is down. The projection is usually obtained to
evaluate for pleural fluid.
5. Oblique View – The oblique projections are the RAO and LAO. They are
not usually obtained as a matter of routine but may be helpful in
localization of an abnormality in the lungs and helpful in evaluation of the
heart to determine specific chamber enlargement.
6. Lordotic View – This view is usually obtained in the AP projection with the
patients tilted back. The clavicles are projected above the lungs, therefore,
providing a better view of the upper lung fields.
EVALUATION OF THE CHEST
It is essential to have a systematic approach to the evaluation of the chest x-ray.
The PA chest film should be well centered. This can be determined by checking
the distance between the heads of the clavicles and the spinous process of the
vertebra between the clavicles.
The chest film should be penetrated just enough to see the thoracic vertebral
bodies but not enough to see the intervertebral disc spaces.
Films should be obtained in the best inspiratory effort possible. If nine of ten
posterior ribs can be counted above the diaphragm, this usually means the film
was obtained in good inspiration.
It is important to recognize the normal before the abnormal can be appreciated.
Several important features should be observed in analyzing the chest film:
1. The soft tissues and bony structures should be evaluated and checked
for symmetry.
2. The right hemidiaphragm is usually slightly higher than the left.
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3. The left hilus is slightly higher than the right.
4. The trachea should be in the midline position down to the aortic knob
where there is slight deviation to the right by the aortic knob.
5. Observe the interlobar fissures. The minor fissure can be seen on the
PA view running horizontally in the right mid lung field toward the hilus.
The major fissures are usually not seen on the PA view, but can be
well seen on the lateral view running from the anterior costophrenic
angle to the region of the T-5 vertebral body.
6. On the lateral view, the thoracic vertebral bodies become more lucent
(darker) as you go inferiorly. If they are more dense, this usually
indicates an opacity in the posterior lung base.
7. Check the normal bumps along the mediastinum. On the left from
superiorly to inferiorly are the left subclavian vessels, aortic knob, main
pulmonary artery segment, left atrial appendage, and left ventricle. On
the right are the innominate vessel, superior vena cava, right atrium,
and inferior vena cava.
8. On the lateral view the right hemidiaphragm can usually be
distinguished from the left because is extends all the way to the
anterior chest whereas the left is obliterated anteriorly by the positive
silhouette sign produced by the heart. The right hemidiaphragm is also
slightly higher and the stomach bubble is under the left diaphragm.
9. The CP angles should be sharp. Blunting may indicate pleural effusion.
10. The vessels in the suprahilar region are smaller than those in the
infrahilar region in the upright position. If the upper lobe vessels are the
same size or larger than the lower lobe vessels, this usually means
pulmonary venous congestion, possibly from left heart failure. On films
obtained in the supine position, the upper lobe and lower lobe vessels
are of equal size.
11. The stomach bubble is located approximately 5mm. below the left
hemidiaphragm. If this distance is increased, pleural effusion should be
suspected. If air is within 1mm. To 2mm. Under the diaphragm, free
intraperitoneal air should be suspected. Free intraperitoneal air is
usually located under the most superior aspect of the diaphragm.
12. Always look carefully behind the heart, in the CP angles and in the
lung apices because pathology is frequently overlooked in these areas.
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ABNORMALITIES PRODUCING INCREASED DENSITY IN THE LUNGS
1.
2.
3.
4.
1.
Parenchymal disease
a. Air space disease – consolidation
b. Interstitial disease.
Atelectasis
Pleural effusion
Pulmonary nodules and other mass lesions
Parenchymal disease
In general, these densities may be thought of as involving the air spaces,
the interstitium of the lung or a combination of the two.
A.
Air space disease
Fluid (exudates, transudate, blood) replaces the air in the
pulmonary acinus. The pulmonary acinus represents that portion of
lung to a terminal bronchiole and consists of respiratory
bronchioles, alveolar ducts, alveolar sacs, and alveoli.
The acinus is the unit of lung that can be seen on the x-ray with air
space disease as flurry irregular shadows approximately 5mm. in
diameter. Air space disease may spread through the pores of Kohn
and coalesce to produce consolidation. Air spaces and distal
bronchial structures within an area of consolidation, which still
contain air rather than fluid are identified as air bronchograms and
are the hallmark of air space disease.
Most pneumonias are manifest as air space disease. It is helpful to
look for the distribution in the lung, pneumatoceles, pleural effusion,
and other associated findings, which may help identify the specific
type of pneumonia. Determination of a specific causative agent for
pneumonia is usually not possible by x-ray.
Pulmonary edema from any cause such as heart failure, azotemia,
inhalation of noxious agents, etc. are manifest as air space disease
in a perihilar or bat-wing distribution. Pulmonary hemorrhage may
also have the same perihilar distribution.
B.
Interstitial disease
The radiographic appearance of interstitial disease consists of
either a nodular or reticular pattern. The nodules are usually small
and punctate in appearance and the reticular pattern has the
appearance of numerous interlacing linear densities.
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Honeycombing may be associated with interstitial disease and
appears as small cystic spaces within a coarse reticular infiltrate.
Several diseases present with interstitial involvement. Interstitial
edema secondary to congestive failure is one of the most common
interstitial processes. Certain pneumonias may present as
interstitial disease such as viral, Mycoplasma, and pnemocystics
carinii infections. Many pneumonias represent a combination of
interstitial and air space disease. Interstitial pneumonias in children,
especially RSV pneumonias, also produce peribronchial thickening
best seen in the hilar areas as peribronchial cuffing.
CT scanning using a special technique of High Resolution , HRCT,
is very helpful in the evaluation of diffuse parenchymal disease and
permits the visualization of the parenchymal network of the lung.
The interstitial network is much better seen than with the plain film
or conventional CT. Thickening of the interstitial tissue from
inflammation, fibrosis and tumor as well as focal areas of
decreased opacity may be better appreciated with HRCT.
There are a number of diseases which present primarily as diffuse
interstitial disease.
1.
2.
3.
4.
5.
6.
2.
Idiopathic interstitial fibrosis
Sarcoidosis
Rheumatoid lung
Eosinophilic granuloma of lung
Pneumoconiosis
Metastatic disease
Atelectasis – Volume loss in the lung may be secondary to obstruction of
the bronchus, compression of lung tissue or scarring.
Obstructive atelectasis is also known as resorption atelectasis. A major
bronchus is occluded and there is a resultant resorption of air in spaces
and loss of volume.
Compression of lung may be secondary to an adjacent mass or bulla.
Compression of lung by pneumothorax or effusion in the pleural space
also results in loss in volume of the lung.
Scarring may result in retraction and loss of volume.
The signs of atelectasis are largely produces as a result of volume loss.
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Signs of atelectasis:
A.
Local increased density
B.
Displacement of interlobar fissures
C.
Elevation of hemidiaphragm
D.
Displacement of mediastinum
E.
Compensatory overinflation
F.
Displacement of hila
G.
Approximation of ribs
H.
Absence of air bronchograms in obstructive atelectasis
Displacement of fissures is one of the most important of the signs of
atelectasis. The fissures always appear as sharp straight lines bordering
on an area of increased density.
3.
Pleural Effusion
Pleural effusion is first seen in the posterior costophrenic gutters on the
lateral view. The posterior gutter is deeper than the lateral costophrenic
angles; therefore, small amounts of fluid are first seen here. The
diaphragm on the side of the effusions is usually obliterated on the lateral
view.
Fluid then fills the lateral costophrenic angle.
As fluid accumulates, the superior border appears as a meniscus. The
lateral margin seems higher on the PA view because the x-ray beam is
shooting through a greater thickness of fluid projection. The fluid appears
to extend more posteriorly and anteriorly on the lateral view for the same
reason.
Occasionally, fluid may appear as an elevated diaphragm. This is referred
to as subpulmonic effusion and the lung appears to elevate away from the
diaphragm with the superior margin of the pleural fluid maintaining the
same configuration as the diaphragm rather than a meniscus appearance.
If pleural effusion is suspected, the decubitus view is the recommended
view for further evaluation. This will reveal a shift and layering of fluid
along the dependent portion of the chest is the fluid is free in the pleural
space.
Large amounts of pleural effusion may produce shift of the mediastinal
structures to the opposite side.
Fluid may also encapsulate in the pleural space if there is fusion on the
parietal and visceral layers. The fluid in this case will demonstrate the
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extrapleural sign with a convex border. This configuration is commonly
seen with empyema and is best evaluated with CT scanning. CT scanning
is also helpful to differentiate pleural fluid from other causes of
parenchymal opacification.
Fluid may also accumulate in an interlobar fissure and present as a
homogeneous mass. The mass of elliptical configuration and conforms to
an interlobar fissure. This is commonly seen with congestive failure.
4.
Nodules and Mass Lesions
Lung abscesses and loculated fluid may present as mass lesions.
Malignancy should be the primary consideration in any mass that is
encountered in the lung.
Pulmonary nodules and other mass lesions should be carefully evaluated
to determine if the lesion is single or multiple. CT is usually necessary to
characterize the nodule and to determine if the nodule is single or multiple
Other factors to be considered in evaluating a nodule are:
A.
Presence of calcifications – Central calcification indicates a benign
lesion and is the only absolutely certain sign of benignity. Popcorn
type calcification is characteristic of a hamartoma.
B.
Borders of the lesions – Smooth borders usually indicate a benign
lesion; irregular and speculated margins indicate malignancy.
C.
Length of time the lesion has been present – If present for over two
years with no change in size, this usually means a benign nodule;
however, occasionally malignancy will go for ling periods without
change.
D.
Location – Pulmonary sequestration may present as a mass and it
typically located in the lung bases adjacent to the diaphragm.
Metastatic lesions are more common in the lower lobes. It is
unusual to find a solitary metastasis in the upper lobes.
E.
Cavitation – If the cavity wall is thick and irregular, lung abscess or
carcinoma, either primary or metastatic, should be considered. If
the wall is thin, this is usually a benign process such as a
coccidioidomycosis or infected bulla.
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F.
Adjacent Structures – Pulmonary AV malformations
characteristically have large vessels associated with the mass,
which are directed toward the hilus.
ABNORMALITIES WHICH PRODUCE DECREASED DENSITY OF LUNG
Hyperinflation of the lungs from any cause will cause hyperlucency.
Decrease in the pulmonary vascularity such as with congenital heart disease can
cause generalized decreases density.
CAUSES OF GENERALIZED RADIOLUCENCY OR HYPEREXPANDED
LUNGS
1.
2.
3.
4.
5.
1.
Emphysema
Asthma
Bronchiolitis
Congenital heart disease
Tracheal or laryngeal obstruction
Emphysema – There is a pathological enlargement of the distal air spaces
either from chronic dilation or from destruction of their walls.
Radiographic features of emphysema:
A.
Lungs are hyperexpanded. The diaphragms are flattened
and usually eleven posterior ribs can be seen on the PA
view. The retrosternal space is increased.
B.
There is a reduction in the number and size of vessels in the
peripheral portions of the lungs.
C.
The main pulmonary arteries are enlarged and the branches
taper rapidly and there is reduction in the branching
(pruning). This finding usually indicates pulmonary
hypertension.
D.
The heart shadow usually appears long and narrow.
2. Asthma – the lungs are hyperexpanded with the diaphragm is a low
position and there is increase in the retrosternal space. In contrast to
emphysema, the vascular markings are usually normal. It is important to
look for associated problems such as consolidation, atelectasis,
pneumomediastinum and pneumothorax.
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DECREASED DENSITY OF THE LUNGS MAY BE UNILATERAL IN WHICH
CASE THE FOLLOWING CAUSES SHOULD BE CONSIDERED
1.
Absence of soft tissues of the chest wall
2.
Rotation – technical factors
3.
Pneumothorax
4.
Bullous emphysema
5.
Compensatory overdistention with collapse
6.
Absent of phypoplastic pulmonary artery
7.
Congenital lobar emphysema
8.
Pneumatocele
9.
Pulmonary embolus
Absence of soft tissues – Absence of soft tissues from mastectomy is one of the
most common causes of one lung appearing more lucent than the other.
Rotation – Rotation of the patient may produce a similar appearance.
Pneumothorax – is a collection of air within the pleural space, between the
visceral and parietal pleura. Pneumothorax may be spontaneous and is
commonly produced by a ruptured bleb. Spontaneous pneumothorax may occur
in young adults.
Pneumothorax may be produced by many other conditions including interstitial
lung disease and mechanical ventilation. Chronic obstructive pulmonary disease
and asthma may also produce pneumothorax and be related to alveolar rupture
with dissection into the pleural space. Alveolar rupture commonly dissects along
vascular sheaths into the mediastinum and produces pneumomediastinum.
Trauma is a common cause of pneumothorax and results from penetrating injury
of the chest. Penetrating injury or rib fractures may rupture the pleura and result
in pneumothorax. Pneumothorax may be iatrogenic following a thoracentesis or
subclavian puncture for placement of subclavian lines.
Radiographically, pneumothorax presents as a radiolucency of the chest due to
the accumulation of air within the pleural space. No vascular markings are
identified within the hyperlucent area. The hallmark of pneumothorax is the
detection of the visceral pleural line profiled against air in the pleural space and
air in the adjacent partially collapsed lung. There is radiolucency peripheral to the
visceral pleural line, which represents air between the visceral and parietal pleura
of the lung. Pneumothorax may be under tension in which case there is
increased volume in the hemothorax with contralateral shift of the heart and
mediastinum, depression of the diaphragm, and separation of the intercostal
spaces.
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A small pneumothorax may be very subtle and difficult to identify on the plain
chest film. A film in expiration will accentuate the air within the pleural space and
help in diagnosing a pneumothorax. Decubitus views and lateral projections are
often helpful in identifying air within the pleural space.
Bulla – An air-filled thin-walled space within the lung secondary to the destruction
of alveolar tissue. A bulla is usually larger than 0.5 cm. and may become
enormous in size compression adjacent lung tissue. A large bulla produces
radiolucency or decreased density of the involved area. Bulla should be
distinguished from blebs which are much smaller. Blebs – are air spaces usually
less than 0.5 cm. in size located in the apical regions between the visceral and
parietal pleura. Rupture of a bleb is commonly associated with spontaneous
pneumothorax.
Compensatory Emphysema – When a section of lung contracts, either by
collapse or fibrosis or is surgically removed, the remainder of that lung expands
by overinflation.
Congenital Lobar Emphysema – occurs in infancy and may be a cause of
respiratory distress. The upper lobes are the most commonly involved; sometime
the right middle lobe. Congenital lobar emphysema is thought to be related to
maldevelopment of cartilage in the bronchus producing air trapping.
Radiographically, the lesion appears as an overdistended upper lobe, which is
markedly hyperlucent and void of normal vascular markings. The mediastinum is
frequently shifted to the opposite side,
Pneumatocele – a thin-walled cystic structure similar in appearance to a bulla.
These are probably secondary to overdistention and air trapping distal to a
partially obstructed small bronchiole. They are commonly seen in staphylococcal
and hydrocarbon pneumonias.
Pulmonary Embolus – Radiographic findings in pulmonary embolus on the plain
chest film are minimal and a normal chest film is frequently the case. An area of
radiloucency or decreased density may be seen on the plain film as a result of
the oligemia produced by the occluded pulmonary vessel. This area of
radiolucency is know as the Westermark Sign.
In pulmonary infarction, an area of pleural-based consolidation may develop in a
segmental of subsegmental distribution. The pleural based density has a
rounded configuration and is referred to as a Hampton’s Hump.
Subsegmental atelectasis and pleural reaction with a small effusion are other
common manifestations of infarction. The diaphragm may also be elevated on
the affected side. Occasionally infarcts may become infected and cavitate.
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The diaphragm may also be elevated on the affected side.
CT scanning utilizing a special protocol to assure the proper timing of contrast
media filling the pulmonary vessels is now the imaging method of choice
CAVITIES
Cavities represent a combination of increased and decreased density on
radiographs and the following should be considered in the differential diagnosis
of a solitary cavitary lesion.
1.
Abscess
2.
Bronchogenic carcinoma
3.
Granulomas due to TB, fungus, or idiopathic
4.
Metastatic neoplasms
5.
Blebs or bullae
6.
Lung cyst (bronchogenic, congenital)
7.
Traumatic cyst
8.
Pneumatocele
In the cavity, the central portion of an area of increased density had been
replaced by air.
An abscess and cavity are not synonymous. An abscess which does not
communicate with the bronchial tree is a homogeneous density on the
radiograph. When necrotic tissue in the center of an abscess is replaced by air
as a result of communication with the bronchus, it then becomes a cavity.
Several features of a cavitary lesion should be carefully observed to help in the
differential diagnosis.
1.
Thickness of wall – A thick wall usually means lung abscess,
primary or metastatic neoplasm. Thin walls may be seen in bullae,
pneumatoceles, and post-traumatic lung cysts.
2.
Inner lining – Irregular nodular inner lining usually means a
carcinoma. A shaggy inner lining usually indicates a lung abscess.
3.
Contents of a cavity – An intercavitary mass is diagnostic of fungus
ball or mycetoma. This mass is frequently movable.
A ruptured Echinococcus cyst may reveal the collapsed membrane
floating on fluid within the cyst.
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4.
Multiplicity of lesions – Some cavitary lesions may be multiple and the
following possibilities should be considered:
A.
Bullae
B.
Cystic bronchiectasis
C.
TB and fungus disease
D.
Metastasis
E.
Pneumatoceles
F.
Septic emboli
G.
Rheumatoid granulomas
H.
Wegener’s granulomatosis
I.
Cystic adenomatoid lung
MEDIASTINAL LESIONS
The divisions of the mediastinum as defined by the anatomist are difficult to
identify on the radiograph. Because of ease in identifying the mediastinal
compartments, the following radiographic subdivision is recommended as
suggested by Felson.
An imaginary line is traced upward from the diaphragm along the back of
the heart and in front of the trachea to the neck. This divides the anterior
from the middle mediastinum. A second imaginary vertical line connects
the point of each thoracic vertebra 1 cm. behind its anterior margin. This
divides the middle from the posterior mediastinum.
Divisions of the mediastinum into the various compartments is helpful in
differential diagnosis.
1.
Anterior mediastinum
a. Substernal thyroid
b. Thymic lesions
c. Teratomas
d. Lymphoma
)
)
)
)
3 T’s and an L
2.
Middle mediastinum
a. Lymph node disease – inflammatory, primary, or metastatic
carcinoma
b. Bronchogenic cyst
c. Esophageal lesions
d. Aneurysms of aorta
3.
Posterior mediastinum
Neurogenic tumors
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Thymomas are the most frequently found tumors of the anterior mediastinum and
teratomas are a close second.
Fifteen percent of patients with myasthenia gravis have thymomas.
Seventy-five percent of thymoma patients have myasthenia gravis.
Calcium may be present in either teratomas or thymomas. Presence of bone,
teeth, or calcium in mediastinal teratomas is less common than in ovarian
teratomas.
Substernal thyroid commonly produces deviation of the trachea. Isotopic
scanning is helpful in establishing the diagnosis of substernal thyroid.
Bronchogenic cysts are usually found in the middle mediastinum and are
commonly subcarinal in location.
Gastroenteric cysts may be found in the middle mediastinum and are similar to
bronchogenic cysts except that they are lined with GI mucosa and have two
layers of muscle but no cartilage in the wall. They are usually closely associated
with the esophagus.
Lesions of the posterior mediastinum are almost always of neurogenic origin and
common lesions are:
1.
Neurilemomas – found in older people and have a rounded
configuration
2.
Ganglioneuromas – found in young people and are elliptical or
fusiform in shape.
3.
Neuroblastoma – a highly malignant tumor found in infants
CONGESTIVE HEART FAILURE
Congestive heart failure occurs when the left ventricle fails to eject a normal
volume of blood during systole. Decreased ejection results in increased
ventricular end-diastolic volume, increased pressure, and slight cardiac
enlargement. Mild to moderate cardiac enlargement may not be detected on
portable radiographs because of the magnification. Serial films showing
progressive enlargement may be helpful. Because of the variability of heart size,
radiographic signs of increased pulmonary venous pressure, no cardiomegaly,
are the primary diagnostic criteria. Assessment of the pulmonary vascularity on
the chest film may be difficult on supine films. Ideally, an upright film or at least a
semi-erect AP radiograph should be obtained.
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The following correlation between the chest radiograph and the pulmonary
wedge pressure may be helpful:
1.
The radiograph is normal when the pulmonary capillary wedge pressure
(PCW) is less than 12mm. Hg.
2.
When the PCW is 12-18mm. Hg, there is a redistribution of flow to the
upper lobe vessels. The upper lobe vessels appear engorged and indicate
mild CHF.
3.
When the PCW is between 18-22mm. Hg, the peripheral vessels dilate.
Interstitial edema develops in the form of Kerley lines. Kerley lines may
appear as linear shadows best seen peripherally in the lungs bases
(Kerley-B lines). Kerley lines may also appear as linear shadows radiating
from the hilar regions (Kerley-A lines) or as reticular linear shadows
throughout the lung fields (Kerley-C lines). There may also be blurring of
the margins of medium-sized vessels and peribronchial cuffing or
thickening.
4.
Further elevation of the PCW above 22mm. Hg results in fluid in the
alveoli or alveolar edema.
Cardiomegaly and pleural effusions are inconsistent findings. The radiography
may also lag several hours behind the PCW in the patient’s course. Other factors
may alter the appearance of classic congestive failure such as pulmonary
parenchymal disease and gravity. COPD commonly alters the picture of
pulmonary edema. In the bedridden patient with pulmonary edema who has
segmental or lobar sparing, the possibility of a recent pulmonary embolus to that
area should be considered.
It is often difficult to distinguish cardiogenic pulmonary edema from other causes
of bilateral infiltrates such as pneumonia and ARDS. If the patient is placed in the
decubitus position for a prolonged period of time, edema will increase on the
dependent side and diminish on the contralateral side, whereas other infiltrates
will not diminish.
MONITORING APPARATUS
1.
Endotracheal Tubes
The proper radiographic evaluation of the endotracheal tube position
requires an estimate of the position of the tube tip relative to the carina
and a knowledge of the position of the head and neck at the time of the
radiograph. There is considerable movement of the endotracheal tube
relative to the carina with flexion and extension of the head and neck.
There is descent of the tube with flexion of the neck and ascent of the tube
with extension. The combined excursion of the tip of the tube may be as
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much as 4 cm. When the head and neck are in the neutral position, the
inferior border of the mandible overlies C5 to C6. In full flexion the
mandible is over the upper thoracic spine and in full extension the
mandible is above C4. Ideally, the tip of the endotracheal tube should be
5-7 cm. above the carina in the neutral position.
One of the most common aberrant positions for the endotracheal tube is
extension into the right main stem bronchus. This may result in atelectasis
of the left lung with shift of the mediastinum to the left and hyperlucency of
the right lung. If the endotracheal tube enters the bronchus intermedius,
the right upper lobe may also collapse.
2.
Tracheostomy Tubes
The tub tip should be located approximately one-half to two-thirds the
distance between the tracheal stoma and the carina. T3 is usually a
satisfactory position. The lumen of the tracheostomy tube should be
approximately two-thirds the diameter of the trachea. Pneumothorax,
pneumomediastinum, and subcutaneous emphysema are frequent
sequelae of tracheostomy.
3.
Subclavian Vein Catheters
The optimal location of the catheter tip is within the superior vena cava or
at the cavo-atrial junction. It is important to look for aberrant positioning
such as an extravascular location or extension into the jugular vein.
Catheters may also extend into the right ventricle of extrathoracic
locations. Pneumothorax is a frequent complication and if possible, an
upright film is the most helpful in evaluation for the detection of pleural air
and the visceral pleural line. Films in expiration may also accentuate the
pneumothorax and aid in detection.
4.
Swan-Ganz Catheters
The tip of the catheter is ideally positioned so that it is within the right or
left main pulmonary artery. Inflation of the balloon causes the catheter to
float downstream into a wedge position and deflation of the balloon allows
the catheter to recoil into the central pulmonary artery. Potential
complications are pulmonary infarction distal to the tip of the catheter and
occurs as a result of occlusion of the pulmonary artery by the catheter
itself or from clot formation in or about the catheter. Other aberrant
positions of the Swan-Ganz catheter may be extension into a jugular vein
or out the right atrium into a hepatic vein.
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INDICATIONS FOR THE PERFORMANCE OF CHEST RADIOGRAPHY:
A. Evaluation of signs and symptoms potentially related to the respiratory,
cardiovascular, and upper gastrointestinal systems, and the
musculoskeletal system of the thorax. The chest radiograph may also help
to evaluate thoracic disease processes, including systemic and
extrathoracic diseases that secondarily involve the chest. Because the
lungs and bony thorax are frequent sites of metastases, chest radiography
may be useful in staging extrathoracic as well as thoracic neoplasms.
B. Follow-up of known thoracic disease processes to assess improvement,
resolution, or progression.
C. Monitoring of patients with life-support devices and patients who have
undergone cardiac or thoracic surgery or other interventional procedures.
D. Compliance with government regulations that may mandate chest
radiography. Examples include surveillance PA chest radiographs for
active tuberculosis or occupational lung disease or exposures, or other
surveillance studies required by public health law.
E. Preoperative radiographic evaluation when cardiac or respiratory
symptoms are present or when there is a significant potential for thoracic
pathology that may influence anesthesia or the surgical result or lead to
increased perioperative morbidity or mortality.
INDICATIONS FOR THE PERFORMANCE OF CHEST CT:
Chest CT may be a complementary examination to other imaging studies such
as chest radiography (see the ACR–SPR Practice Guideline for the Performance
of Chest Radiography) or a stand-alone procedure.
A. Evaluation of abnormalities discovered on chest radiographs.
B. Evaluation of clinically suspected thoracic pathology.
C. Staging and follow-up of lung and other primary thoracic malignancies, and
detection and evaluation of metastatic disease.
D. Evaluation for thoracic manifestations of known extrathoracic diseases.
E. Evaluation of known or suspected thoracic vascular abnormalities (congenital
or acquired).
F. Evaluation of known or suspected congenital thoracic anomalies.
G. Evaluation and follow-up of pulmonary parenchymal and airway disease.
H. Evaluation of trauma.
I. Evaluation of postoperative patients and surgical complications.
J. Performance of CT-guided interventional procedures.
K. Evaluation of the chest wall.
L. Evaluation of pleural disease.
M. Treatment planning for radiation therapy.
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