Download ⑤look at the diaphragms

Part 3
How to read a chest X-ray
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 HU
胡春峰
chunfeng
Including:
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The standard CXR projections
Normal radiographic anatomy
Assessment of a few important
techniqual aspects
Common radiographic findings and
patterns
Differential diagnosis
一、Projections performed
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1.The posteroanterior(PA) erect
diagram
Why?
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Accurate assessment of cardiac size as
a result of minimal magnification .
Scapulae can be rotated out of the way.
Why?
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Physiological representation of blood vessels of
mediastinum and lung.
Gas passes upwards (pneumothorax, free gas beneath
diaphragm)
Fluid passes downwards (pleural effusion)
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2. Lateral
Why?
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Further view of lungs, especially those
areas obscured on the PA film.
Further assessment of cardiac
configuration.
Further anatomical localization of
lesions.
More sensitive for pleural effusions
Good view of thoracic spine
二、Radiographic anatomy
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1.The posteroanterior
view
2.the lateral view
Tr （trachea）
SVC
RH(hilum) , LH
RA(right atrium）
AA(aortic arch/knuckle)
DA(descending aorta)
St
3.Diagnostic assessment of the CXR
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Accurate interpretation of the CXR
may be difficult or impossible in the
absence of relevant and accurate
clinical information.
PA and lateral film
(several important aspects)
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①Lung fields:
these should be of equal
transradiancy and one
should not be any whiter
or darker than the other.
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Look particularly at difficult areas where lesions
are easily missed:
Behind the heart
Behind each hilum
Behind the diaphragms
Lung apics
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②Look at the hilum.
The left hilum should be higher
than right though the difference
should be less than 2.5cm.
Compare the shape and density
of the hila. They should be
concave in shape and look
similar to each other.
The hilum is formed by main
bronchi, pulmonary artery and
their lobar divisions.
③look at the heart
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Check that the heart is of a
normal shape and that the
maximum diameter is less than
half of the transthoracic diameter.
Check that there are no
abnormally dense areas of the
heart shadow.
CARDIAC POSITION
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The apex is directed towards the patient’s left chest wall
Malpositioned too far to the left by collapse of the left
lung or by a space-occupying process (i.e. tension
pneumothorax or a large pleural effusion) on the right.
pulled to the right by right-sided collapse or by a leftsided space-occupying process.
Dextrocardia refers to reversal of the normal orientation
of the heart with the cardiac apex directed to the
patient’s right.
Dextrocardia with the gastric bubble lying beneath the right diaphragm
CARDIAC SIZE
 The cardiothoracic ratio (CTR) is the
ratio between maximum transverse
diameter of the heart and the
maximum transverse diameter of the
chest.
 a CTR of greater than 0.5 indicates
cardiac enlargement
The cardiothoracic ratio (CTR) is less than 0.5
④check the rest of the
mdiastinum
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The edge of the mediastinum
should be clear though some
fuzziness is acceptable at the
angle between the heart and the
diaphragm, the apices and the
right hilum.
A fuzzy edge to any other parts
of the mediastinum suggests a
problem with the neighbouring
lung(either collapse or
consolidation).
⑤look at the diaphragms
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The right diaphragm should be
higher than the left and this can be
remembered by thinking of the
heart pushing the left diaphragm
down. The difference should be
less than 1.2 inch/3cm.
The outline of the diaphragm
should be smooth.
The highest point of the right
diaphragm should be in the middle
of the right lung field and the
highest point of the left diaphragm
slightly more lateral.
⑥look specifically at the
costophrenic angle
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They should be well-defined acute angles.
Posterior costophrenic angle: very small pleural
effusions are seen with greater sensitivity than on the
PA film
⑦look at the trachea
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This should be central but
deviates slightly to the right
around the aortic knuckle.
If the trachea has been
shifted it suggests a problem
within the mediastinum or
pathology within one of the
lungs.
⑧look at the bones and chest wall
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Look at the ribs, scapulae, clavicles,
sternum and thoracic vertebrae.
Follow the edges of each individual
bone to look for fracture. Look for
areas of blackness within each bone
and compare the density of the
bones which should be the same on
both sides.
Soft tissues: check that both breast
shadows are present or mastectomy
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⑨Pleural space:
Check around the periphery of each
lung in the pleural spaces for
pneumothorax, pleural effusion,
pleural thickening or calcification.
4.Technical assessment
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We should assess the technical quality of
the PA film before making a diagnostic
assessment.
The patient should be properly centred on
the film.
With an adequate inspiration
X-ray exposure should be appropriate
Degree of inspiration
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To judge the degree of inspiration, count the
number of ribs above the diaphragm.
The midpoint of the right hemidiaphragm shuld be
between the 5th and 7th ribs anteriorly.
The anterior end of the 6th rib should be above the
diaphragm as should the posterior end of the 10th
rib.
If more ribs are visible the patient is hyperinflated.
If fewer are visible the patient has not managed a
full intake of breath perhaps due to pain,
exhaustion or disease.
The questions:
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The standard CXR projections.
Do you know what form the hilum?