Interpretation of Chest X-Rays
Chair Person : Dr. Muralidhar
Presenter : Dr. Akash Jain

Introduction
• Chest X-rays are the most commonly used radiographic imaging by
physicians.
• Chest X-rays should always be used in conjunction with the clinical
findings.
• Always compare with previous X-rays whenever available.

Relative Densities:
• The hierarchy of relative densities from least dense (Black) to most
dense (white) :
• Gas (air in the lungs)
• Fat (fat layer in soft tissue)
• Water (same density as heart and blood vessels)
• Bone (the most dense of the tissues)
• Metal (foreign bodies)

Factors Determine the technical quality of the
Radiograph:
• Inspiration
• Penetration property
• Rotation

Inspiration
• The chest radiograph should be obtained with the patient in full
inspiration to help assess intrapulmonary abnormalities
• At full inspiration, 6 anterior ribs, 10 posterior ribs are seen and the
right hemi-diaphragm should be observed at about the level of the 8th
to 10th rib posteriorly, or the 5th to 6th rib anteriorly.

Anatomical Part Inspiration Expiration
Superior Mediastinum Normal Magnified
Trachea Straight May be buckled
Heart Normal size Magnified
Lungs Fully expanded Partially expanded
Broncho-vascular markings Well spread out Crowded
Diaphragm Lowest Highest
Rib Cage Anterior ends lower Anterior and posterior same
level
Lung Volume Normal Reduced

Penetration Property
• On a properly exposed chest radiograph:
• The lower thoracic vertebrae should be visible through the heart
• The broncho vascular structures behind the heart(trachea, aortic
arch, pulmonary arteries, etc.) should be seen.

Underexposure
In an under exposed
chest radiograph, the
cardiac shadow is
opaque, with little or no
visibility of the thoracic
vertebrae.
The lungs may appear
much denser and whiter,
gives appearance of
infiltrates.

Overexposed
With greater exposure of the
chest radiograph, the heart
becomes more radiolucent
and the lungs become
proportionately darker.
Often gives the appearance
of lacking lung tissue, as
would be seen in a condition
such as emphysema.

Rotation
• Patient rotation can be assessed by observing the clavicular heads
and determining whether they are equal distance from the spinous
processes of the thoracic vertebral bodies.

Chest X-Ray Views
1. Posterior-anterior(PA)
2. Lateral
3. Anterior-posterior(AP)
4. Lateral Decubitus

Posterior-anterior (PA) Position
• The standard position for obtaining a routine adult chest radiograph
• Patient stands upright with the anterior wall of chest placed against
the front of the film
• The shoulders are rotated forward enough to touch the film, ensuring
that the scapulae do not obscure a portion of the lung field
• Usually taken with the patient in full inspiration
• The PA film is viewed as if the patient is standing in front of you

Anterior-Posterior (AP) Position
• Used when the patient is debilitated, immobilized, or unable to
cooperate with the PA procedure
• Film is placed behind the patient’s back with the patient in a supine
position
• Heart is at a greater distance from the film hence appear more
magnified than in a PA
• The scapulae are usually visible in the lung fields because they are not
rotated out of the view as they are in a PA

Parameter PA View AP View
Position Erect Supine
Patient’s hands On hips Along the sides
Scapula Away from lung
fields
Over the lung
fields
Clavicle Project over the
lung fields
Project above
lung apices
Ribs Posterior ribs
are distinct
Anterior ribs are
distinct
Marker PA AP

Lateral Position
• Patient stands upright with the left side of the chest against the film
and the arms raised over the head
• Allows the viewer to see behind the heart and diaphragmatic dome
• Typically used in conjunction with a PA view of the same side of chest
to help determine the three-dimensional position of organs or
abnormal densities

Lateral Decubitus Position
• The patient lies on either the right or left side rather than in the
standing position as with a regular lateral radiograph
• The radiograph is labeled according to the side that is placed down (a
left lateral decubitus radiograph would have the patient's left side
down against the film
• Often useful in revealing a pleural effusion that cannot be easily
observed in an upright view, since the effusion will collect in the
dependent position

Approach : ABCDEFGHI

AIRWAY

BONES & SOFT TISSUES

CARDIA

CARDIAC SITUS
LEVOCARDIA DEXTROCARDIA MESOCARDIA

Normal cardiac contour (PA view and
Lateral view)

CT Ratio - Cardiomegaly
Adults >0.50
Neonates >0.60
AP film >0.57

LA enlargement
Shadow in shadow – early sign
Straightening of left heart border
Elevation of left main bronchus
Splaying of carina (>600
.
)

RA enlargement
Right border >5.5cms from midline or 3.5cms
from right sternal border
Spans > 2½ intercostal spaces in its vertical
extent
Exceeds 1/3rd the total diameter of heart
>50% vertical height compared with
mediastinal height

LV enlargement (PA view)
• LV apex forms an obtuse angle
with the diaphragm
• Increased CT ratio

LV hypertrophy (PA view)
• LV hypertrophy causes only a
rounded contour of LV border
• Shmoo sign

RV enlargement (PA view)
Overall increase in cardiac shadow with a
triangular configuration
Tilting-up and posterior displacement of LV
Apex forms an acute angle with diaphragm

RV enlargement (Lateral view)
• Sternal contact sign :
Earliest and most
sensitive sign
• Obliteration of
Holtzneck’s space
NORMAL

Pulmonary vascularity
 Normal
 Increased pulmonary blood flow (Plethora)
 Decreased pulmonary blood flow (Oligemia)
 Pulmonary venous hypertension
 Pulmonary arterial hypertension

Normal pulmonary vasculature
1
2
3
1) RDPA <17mm
2) Larger lower lobe vessels
3) Gradual tapering of vessels from
centre to periphery

Pulmonary Plethora
≥3 end on view in one lung field or ≥5 in both lung fields

Pulmonary Oligemia
Hilar, lobar, and segmental
pulmonary arteries appear small
Concave or absent main
pulmonary artery segment
Lung fields have an overexposed
or emphysema like appearance

Pulmonary Venous Hypertension

GRADE 1 (Cephalisation - Deer Antler Sign)

GRADE 2 (Interstitial edema – Kerley B lines)

GRADE 2 (Interlobar effusion – Phantom tumor)

GRADE 3- Alveolar edema (Bat Wing appearance)

Grades of PVH
Grade Stage X ray Finding PCWP
I Cephalisation
Deer Antler Sign,
Inverted moustache
sign
12-18 mmHg
II Interstitial edema Kerley B lines
19-25 mmHg
III Alveolar edema Bat wing appearance >25 mmHg

Pulmonary Arterial Hypertension
Enlargement of the pulmonary trunk and main
pulmonary arteries
Disproportionately small peripheral vessels
Oligemic lungs
Prune tree appearance

Pericardial Effusion

Pulmonary Embolism

DIAPHRAGM

EFFUSIONS

Pneumothorax

Hydro pneumothorax

F-Lung Fields
• Normally, there are visible markings throughout the lungs
due to the pulmonary arteries and veins, continuing all the
way to the chest wall.
• Both lungs should be scanned, starting at the apices and
working downward, comparing the left and right lung fields
at the same level.

F-Lung Fields

Lungs
• On a PA radiograph, the minor fissure can often be seen as a faint
horizontal line dividing the RML from the RUL.
• The major fissures are not usually seen on a PA view because they
are being viewed obliquely.

Lobar anatomy

Lobar anatomy …

Hidden areas…

AIR BRONCHOGRAM SIGN
• When the internal tubular outline of a bronchus is visible within a
thoracic opacity...that is an air bronchogram.
• It is most commonly associated with a simple pneumonia. Sometimes
it occurs with pulmonary oedema.

The Cardiac density

Chronic Bronchitis

Emphysema

Lung Apices

Peripheral Opacities

H-Hilum and mediastinum

H-Hilum and mediastinum
• The hila consist primarily of the major bronchi and the
pulmonary veins and arteries.
• The hila are not symmetrical, but contain the same basic
structures on each side.
• The hila may be at the same level, but the left hilum is commonly
higher than the right.
• Both hila should be of similar size and density

HILUM CONVERGENCE SIGN

HILUM OVERLAY SIGN

DESCENDING PULMONARY ARTERIES

Mediastinum
• The trachea should be centrally located or slightly to the right
• The aortic arch is the first convexity on the left side of the
mediastinum
• The pulmonary artery is the next convexity on the left, and the
branches should be traceable as it fans out through the lungs
• The lateral margin of the superior vena cava lies above the right heart
border

Mediastinum

ICU – Tubes and Lines

Ryles Tube

Central
Venous
Catheter

Artificial
Valves

PREVIOUS CXR
• Previous CXRS your best friend. You see a real or possible abnormality
on the CXR.
• Was it there before? Has it got larger or smaller? Is it unchanged?
• A previous CXR will often highlight an important but subtle change.
• On the other hand it will frequently provide reassurance that all is
well.

Take Home Message

THORACO-ABDOMINAL SIGN

CERVICO–THORACIC SIGN

SPINE SIGN – POSTERIOR MEDIASTINAL MASS

SUBCARINAL ANGLE

UNILATERAL HYPERTRANSRADIANCY