Prepered by: Dr. Sa’d Sulaiman
Supervised by: Dr. Tawfiq Al Jundi
• The resulting image on the X‐ray detector is a two‐dimensional (2D)
representation of a three‐dimensional (3D) structure.
• The less “dense” the tissue is, the more X‐rays get through and the
greater the amount of radiation hitting a detector, the darker the image
will be.
▪ Conventional radiograph have 5 radiological densities
Less dense
More dense
o The standerd chest radiographs are standing, full inspiratory,
posteroanterior (PA) and the x-ray tube is 6 feet from the
detector.
o The terms posterior and anterior refer to the direction of the x-
ray beam >> PA: traverses the patient from back to front
• The other routine view is the lateral. By convention, the left side of the chest
is held against the x-ray receptor.
▪ When the patient’s condition precludes these standard views,
a portable anteroposterior (AP) view can be obtained. (This is
usually because the patient is too unwell to stand)
▪ Generally less sensitive for detecting disease, and are subject
to technical limitations such as magnification and suboptimal
patient positioning.
X-rays pass from the anterior to the posterior of the patient
Both PA and AP views are viewed as if
looking at the patient from the front
▪ The PA upright is preferred to the AP supine view
because
▪ less magnification
▪ the image is sharper
▪ the erect patient inspires more deeply, showing more lung
▪ pleural air and fluid shift with gravity and are easier to detect
on the erect film.
▪ As a rule of thumb, you should never
consider the heart size to be enlarged if
the projection used is AP. If however the
heart size is normal on an AP view, then you
can say it is not enlarged.
1 - Trachea
2 - Hila
3 - Lungs
4 - Diaphragm
5 - Heart
6 - Aortic knuckle
7 - Ribs
8 - Scapulae
9 - Breasts
10 - Bowel gas
• Upper zone: above upper
boarder of 2nd rib anteriorly
• Middle zone: between
upper boarder of anterior 2nd
rib to upper boarder of
anterior 4th rib
• Lower zone: below upper
boarder of anterior 4th rib
If you have only frontal chest
radiograph refer to
abnormalities by 'zones' not
'lobes'
Silhouette sign:
▪ Is the blurring or obscuration of a normal
radiographic border when two contiguous
structures are of similar radiodensity.
▪ If part of the lung is radiodense (alveolar pattern,
consolidated, water density, airless), it can affect our
ability to see adjacent structures.
▪ We can use these changes to help us both detect and
localize disease in the lung.
RLL and LLL
consolidations we can’t
see the diaphragm
except for the superior
segments of these
lobes where we can
clearly see the
diaphragm and heart
boarders
▪ the left diaphragm
is visible, but the
right is not because
the adjacent right
lower lobe is
consolidated
(airless) the
silhouette sign.
▪ The right heart
border, still in
contact with aerated
right middle lobe, is
visible. The left
heart border is
normal.
Air bronchogram.
▪ The appearance of patent bronchi in the background
of opaque (fluid filled) alveoli
▪ Bronchi are usually not seen on a chest film because
they contain and are surrounded by air.
▪ The presence of air bronchogram indicates:
▪ Lung parenchymal disease
▪ Alveolar pathology
▪ Consolidation
Consolidation
▪ an exudate or other product of disease that replaces
alveolar air, rendering the lung solid
▪ Indicate one of 5 disease processes:
▪
Transude: pulmonary edema
▪
Exudate: pneumonia
▪
Blood: goodpasture, trauma, other vasculitis,…
▪
proteinatous material
▪
Cells/tumor: alveolar cell carcinoma
▪ Opacity: any white lesion on chest X-ray
▪ Lucency: any black lesion on chest X-ray
▪ NB, use these term only when descriping lesions at chest X-ray
for other X-rays of the body it is better to use the terms “radioopaque” or “radio-lucent” lesions
▪ Nodule: Well defined lung opacity less than or equal
to 3 cm
▪ Mass: Well defined lung opacity more than 3 cm
▪ Patch: ill defined lesion
▪ Cavity: a gas-filled space (either partial or complete),
seen as a lucency or low-attenuation area
1 confirm patient identity
2 identify image right and
Left (by metallic marker),
3 assess the quality of the
image.
• anatomy inclusion
First ribs?
Costophrenic angles?
Lateral edges of ribs?
We can’t judge
the CPA or the
Lateral edges of
ribs
3 assess the quality of the
image.
Inspiration and lung volume
(9-10th posterior ribs, or
6th anterior rib intersecting
the center of diaphragm)
• The imaginary dotted line
between the costophrenic
and cardiophrenic angles.
The distance between this
line and the diaphragm
(green lines) should be
greater than 1.5 cm
(asterisk) in normal
individuals.
Chest radiograph taken
during expiration
lungs are relatively airless
and their density is
increased.
• raised position of the
diaphragm leads to
exaggeration of heart size,
and obscuration of the
lung bases.
•
• Is there consolidation?
• How big is the heart?
(Same patient as previous image)
The lungs are not consolidated
The heart size is clearly normal
hyperexpansion
• >7th anterior rib intersecting
the diaphragm at the midclavicular line
• a sign of obstructive airways
disease.
• Also look for flattened
hemidiaphragms
• Standard chest radiograph is full inspiratory but there are some cases where
expiratory films can be helpful
• Suspected foreign body aspiration
• emphysema
• Pneumothorax
Figure A
Figure B
In Figure A the left lung is slightly blacker than the right lung.
In Figure B, an expiratory image, the right deflates normally
and gets whiter. The left remains inflated and black as the
result of air trapping behind an aspirated foreign body.
• An impacted foreign body will
cause partial bronchial
obstruction that impedes
airflow on expiration (air
trapping)
• Because the air behind the
obstructed bronchus cannot
be expelled readily, that lung
remains inflated on expiration.
(larger, darker, and there
might
be mediastinal shift)
CLINICAL PEARL: If you hear
a unilateral wheeze, order an
expiratory image to look for
air trapping.
• Pneumothorax
(An expiratory x-ray may
accentuate a small
pneumothorax.
On expiration, the deflated
lung appears whiter
compared with the black
intrapleural air.
The fixed amount of
intrapleural air is relatively
larger in the
smaller hemithorax.
Therefore it should be easier
to detect a
small pneumothorax.
3 assess the quality of the
image.
Rotation
• The radiograph should
be well centralized
• The spinous processes
should lie half way
between the medial
ends of the clavicles
•
With Rotated picture it is
difficult to know if the
trachea is deviated to one
side by a disease process.
It also becomes difficult to
comment accurately on
the heart size.
3 assess the quality of the
image.
Rotation
• In pediatric patients
measure the distance
between medial end of
the clavicle and
vertebral bodies
3 assess the quality of the
image.
Penetration (exposure)
• Penetration is the degree to
which X-rays have passed
through the body.
• A well penetrated chest Xray is one where the
vertebrae are just visible
behind the heart.
• The left hemidiaphragm
should be visible to the
edge of the spine.
Always check the
structures behind the
heart
overexposed
underexposed
Exposure is related to Kilovoltage peak (kVp)
▪ Decreasing KVp result in whitening of the film and therefore
increases contrast
▪ Why not better?
▪ It increases the time of exposure to X-ray (ionizing radiation)
▪ Increasing time results in increased motion artifact ( by breathing,
cardiac motion) which may lead to hazy film
▪ It would be more difficult to ass the spine and retrocardic lungs
▪ High KVp
▪ Increased sharpness, decreased motion artifact, decreased
radiation, we can see retrocardiac lungs
4 Trachea
• Should be central or slightly
to the right.
• The trachea branches at the
carina, into the left and right
main bronchi
• Look for:
• Filling defects at
trachea
• Shifting of trachea
• increase of the tracheal
bifurcation angle
(normal up to 90
degrees)
• Thickened right Para
tracheal stripe ( normal
less than or equal to 3
▪ tracheal bifurcation
angle more than 90
differential:
▪ Enlarged subcarinal
lymph nodes
▪ Pericardial cyst
▪ Mitral valve disease
Mitral valve disease leading to left atrial enlargement
double density sign
tracheal bifurcation angle over
90
▪ Right paratracheal stripe is a normal finding on the frontal
chest x-ray and represents the right tracheal wall, adjacent pleural
surfaces and any mediastinal fat between them
▪ It normally measures less than 4 mm, and thickening may represent
:
▪ paratracheal lymphadenopathy
▪ thyroid malignancy
▪ tracheal malignancy
▪ pleural effusion/pleuritis
▪ Mediastinitis
▪ Vascular malformatiuons
Widened right paratracheal stripe from lymphadenopathy
5 Lungs
• In normal frontal chest X-ray
as we move from the apex of
the lung to the base the lungs
appear to become whiter
(due to breast shadow in females
and thick pectoralis muscle in
males)
• The lungs are assessed and
described by dividing them
into upper, middle and lower
zones
• If the lungs appear
asymmetrical, determine if
this the asymmetry is because
of normal structures, technical
factors such as rotation, or
lung pathology.
5 Lungs
• In normal lateral chest X-ray
as we move down from the
apex of the lung to the base
the lungs should become
darker.
• There should be 2 lucencies
in the lateral Chest X-ray:
retrosternal and retrocardic,
always check them
6 Heart size and contours
• The heart size is assessed as
the cardiothoracic ratio (CTR)
• A CTR of >50% is abnormal PA view only
• In infants CTR of > 60% is
abnormal (AP is the standard
view up to 4 years, and you can’t
know for sure the exact location of
the thymus)
• The left hemidiaphragm
should be visible behind the
heart
Draw lines at most lateral points on
each side of the heart and inner
aspect of the widest points of the rib
cage
7 Diaphragm
• The hemidiaphragms are
domed, well defined
structures
• The hemidiaphragm contours do
not represent the lowest part of
the lungs
• The right hemidiaphragm is
usually a little higher than the
left because of the heart weight
(so in dextrocardia the left
diaphragm is higher)
7 Diaphragm
• The costophrenic angle (CPA)
should be sharp and smooth
• Obliteration of CPA to be visible
at chest X-ray it needs:
• 200 cc on frontal view
• 70 cc on lateral view
Ultrasound can detect as few as 5
cc!
Always check for air under the
diaphragm (pneumoperitonium)
7 Diaphragm
• On PA view below the diaphragm
there is an overlap between lung
and liver tissue
• If there is and opacity in this
lesion its appearance on chest Xray indicates that the lesion arise
from the lung (liver lesions would
not appear as they will form
silhouette sign)
7 Diaphragm
• At lateral view posterior CPA
appears lower
8 Hilar structures
• The hila (lung roots) mainly
consisting of the major
bronchi and the pulmonary
veins and arteries
• hilar lymph nodes are not
visible on a normal chest Xray, but hilar enlargement is
usually due to enlargement of
these nodes.
• The left hilum is often higher
than the right
• Both hila should be of similar
shape, size and density.
8 Hilar structures
•
In more than 90% of normal
individuals, the left hilar
shadow is higher than the
right. This is because the left
pulmonary artery, which
comprises the predominant
portion of the left hilar shadow,
ascends over the left main
and upper lobe bronchus,
whereas the right pulmonary
artery lies inferior to the RUL
bronchus.
9 Ribs
• Look for fractures, erosions,
lesions
• Check both sides one rib at a
time
• Pancost tumor may cause 1st
rib to disappear
10 special look at lung apex
11 look at the picture as a
whole