Learn Chest X-Ray
With Its Normal
Positioning &
Radio-Anatomy
Dr. Santosh Atreya
MD Resident (Phase- A)
Radiology & Imaging
BSMMU from Nepal

Before the procedure…
• Bring a signed form from your doctor when
you visit the X-ray technician.
• Be aware that you may have to hold your
breath for a few seconds during the X-ray,
especially if the X-ray focuses on the stomach
or chest areas.

What do I need to remove for the
procedure?
• Any jewellery around the affected areas.
unless otherwise advised by your doctor.

LUNGS

Introduction
• Radiographic examination of the lungs is
performed for a wide variety of medical
conditions, including primary lung disease and
pulmonary effects of diseases in other organ
systems. Such effects produce significant
changes in the appearance of the lung
parenchyma and may vary over time
depending on the nature and extent of the
disease.

Recommended projections
Examination is performed by means of the following
projections:
• Basic Postero-anterior – erect
• Alternative Antero-posterior – erect
Antero-posterior – semi-erect
Antero-posterior -supine
• Supplementary
Lateral
Postero-anterior – expiration
Apices
Lateral – upper anterior region
Decubitus with horizontal beam

Positioning
• The choice of erect or decubitus technique is
governed primarily by the condition of the patient.
• With the patient erect, positioning is simplified,
control of respiration is more satisfactory, the
gravity effect on the abdominal organs allows for
the disclosure of the maximum area of the lung
tissue & fluid levels are defined more easily.
• Supplementary projections may be required for
specific indications at the request of a clinician or
radiologist.

Postero-anterior – erect
A 35 X 43-cm or 35 X 35-cm cassette is
selected, depending on the size of the
patient.
Position of patient and cassette
• The patient is positioned facing the cassette,
with the chin extended and centered to the
middle of the top of the cassette.
• The median sagittal plane is adjusted at
right-angles to the middle of the cassette. The
shoulders are rotated forward and pressed
downward in contact with the cassette.
• This is achieved by placing the dorsal aspect
of the hands behind and below the hips, with
the elbows brought forward, or by allowing
the arms to encircle the cassette.

….contd
Direction and centering of the X-ray beam
• The horizontal central beam is directed at
right-angles to the cassette at the level of the
eighth thoracic vertebrae (i.e. spinous
process of T7), which is coincident with the
lung midpoint
• The surface marking of T7 spinous process
can be assessed by using the inferior angle of
the scapula before the shoulders are pushed
forward.
• Exposure is made in full normal arrested
inspiration.These days automatic chest film
changer devices is in use.

Essential image
characteristics
• Full lung fields with the scapulae
projected laterally away from the
lung fields.
• The clavicles symmetrical &
equidistant from the spinous
processes & not obscuring the lung
apices.
• The lungs well inflated.
• The costophrenic angles &
diaphragm outlined clearly.
• The mediastinum & heart central &
defined sharply.
• The fine demarcation of the lung
tissues shown from the hilum to
the periphery.

Penetration
• Adequate penetration of
the patient is also required
for a good film.
• On a good PA film, the
thoracic spine disc spaces
should be barely visible
through the heart but bony
details of the spine are not
usually seen.
• On the other hand
penetration is sufficient
then bronchovascular
structures can usually be
seen through the heart.
•

Left, an example of a normal PA film that is
underpenetrated. Right, an overpenetrated PA film.
Underpenetration: Likelihood of missing an
abnormality
overlying by another structure
Overpenetration: results in loss of
visibility of low density lesion
e.g. early consolidation

•Structures seen in a PA
View

Trachea and Bronchi
• The tracheal lumen appears as
a vertical radiolucent shadow.
Around the aortic knuckle it
deviates slightly to the right.
• Normal maximum coronal
diameter: 25mm for males and
21mm for females.
• In proper erect posture
trachea bifurcates at the level
of lower border of 6th thoracic
vertebra

……contd
• The tracheal lumen is
bordered on the right by
a water density stripe,
called the right
paratracheal stripe, it is
seen in 60% of patients,
normally measuring
about less than 5mm.
• Lt paratracheal stripe is
not visualized.

…….contd
• Rt bronchus is shorter,wider and steeper than
left, which is longer, narrow and less oblique.
• .

The Heart
• The central dense shadow seen
on the PA chest film-
mediastinum, heart, spine and
sternum.
• With good centering, 2/3rd of the
cardiac shadow lies to the left of
midline & 1/3rd to the right.
• The normal cardio-thoracic ratio
< 50% in PA film in adult.in
children however, the CTR is
usually <60%.
• .

 Right border of heart is
formed by-
• Superior vena cava
• The right atrium
• Small part of inferior vena
cava
 Left heart border is formed by-
• aortic nuckle
• The pulmonary bay
• The auricle of left atrium
• The left ventricle.

……Contd
• In babies and young
children the normal
thymus is a triangular sail-
shaped structure with
well-defined borders
projecting from one or
both sides of the
mediastinum

Diaphragm

Diaphragm
• Dome shaped sheet of muscle
• Contains right hemidiaphrgm,central tendon
and left hemidiaphragm
• arches over abdominal contents
• Seperating abdomen from chest

….contd
• on inspiration the domes
are at the level of 6th rib
anteriorly and at or below
the 10th rib posteriorly
• In most patients the right
hemidiaphragm is higher
than the left.

Measurements of hyperinflation of
the lungs
• The normal dome of
each hemidiaphragm should
rise at least 1.5cm above a line
connecting the costophrenic
angle posteriorly and
sternophrenic angle anteriorly

OBLIQUE FISSURE OF LEFT LUNG
HORIZONTAL FISSURE
OBLIQUE FISSURE OF RIGHT LUNG

• The horizontal fissure of right lung may be
seen ,on the PA film extending from right
hilum to the region of the 6th rib in the axillary
line.
On a PA radiograph the main lobes overlap, so
the lung is divided into 3 zones separated by
imaginary horizontal lines 1.upper zone 2.mid
zone 3.lower zone.

• The central area on each
side is referred to as the
hilum of lung field. left hilum
is higher than the right.
• Hilum is formed by
pulmonary vessels,bronchus
and bronchopulmonary
lymph nodes .
• Of all the structures in the
hilum only the pulmonary
arteries and upper lobe veins
contribute significantly to the
hilar shadows.
• Normal bronchial walls are
only seen end-on.

• The apex of each lung field projects above the
medial third of clavicle.
• The infero-lateral corner of each lung field is called
lateral costophrenic angle.
• The infero-medial corner of each lung field is called
cardiophrenic angle.

Bones of chest wall
1. Clavicles:
• The radiograph shows almost entire length of
clavicle. The medial end of the clavicle lie
equidistant from the midline of the spinous
process of the 4th thoracic vertebra in proper
position.
• Rotation Can be assessed by observing the
clavicular heads and determining whether they
are equal distance from the spinous process of
the thoracic vertebral bodies.

2. Thoracic vertebrae
The radiopaque bodies of thoracic vertebrae
should be discernible within the cardiovascular
shadow.
3. Ribs
The radiograph shows the head and neck of most
of the ribs and the bodies of the upper 8 to 10 ribs.
4. Scapulae
The scapula project lateral to the supero-lateral
regions of the lung field in proper positioning.

Soft tissues
It is important to confirm the
presence or absence of breast
shadows.The breast may partially
obscure the lung bases.
Nipple shadows are nodular
opacities that are consistent in
shape, size and position
.

• oval or round
– 5-15mm in diameter
– between the 9th and 10th rib
posteriorly or the 5th and 6th
rib anteriorly
• Care is necessary to avoid mis-
interpretation as a neoplasm
or vice versa

LATERAL VIEW

Lateral view
A supplementary lateral
projection may be useful for
localizing the position of a
lesion, encysted pleural fluid
and demonstrating anterior
mediastinal masses not shown
on the postero-anterior
projection.

Position of patient and cassette
• The patient is turned to bring the side
under investigation in contact with the
cassette.
• The median sagittal plane is adjusted
parallel to the cassette.
• The arms are folded over the head or
raised above the head to rest on a
horizontal bar.
• The mid-axillary line is coincident with
the middle of the film, and the cassette is
adjusted to include the apices and the
lower lobes to the level of the first lumbar
vertebra.

Direction and centering of the X-ray
beam
• Direct the horizontal
central ray at right-angles
to the middle of the
cassette at the mid-
axillary line.

Postero-anterior and lateral radiographs of same patient
showing a tumour in the right lower lobe

Structures seen in lateral view

The clear spaces
• There are two clear spaces;retrosternal and
retrocardiac. these correspond to the sites
where the lungs meet behind the sternum and
the heart
• Loss of translucency of these areas indicates
local pathology.
• Normally the retrosternal space is less than 3
cm deep maximum.

Normal lateral film. Note
the retrosternal and
retrocardiac clear spaces
(open arrows) and the
increased translucency of the
lower vertebrae. The axillary
folds (straight black arrows)
and scapulae (curved black
arrows) overlie the lungs. The
tracheal translucency is well
seen (small black arrows)

Trachea
• Tracheal lumen appears as an vertical radiolucent
band which passes down slightly posterior
direction to the T6/7 level of the spine.
• Tracheal lumen is bordered posteriorly by a
water-density stripe that represents the posterior
tracheal wall and collapsed esophagus together
• The right upper lobe bronchus is seen end-on as a
circular structure overlying the lower trachea.
• Lying inferiorly is the left upper lobe bronchus
seen end-on .

Mediastinal viscera
 The chambers of the heart
cast a bulbous shadow
 The anterior wall of the right
ventricle defines the lower
half of the anterior border of
the cardiac shadow
 The posterior wall of left
ventricle defines the lower
third of the posterior border
of the cardiac shadow
 Posterior wall of left atrium
defines the middle third of
the posterior border of the
cardiac shadow

 The 3 segment of thoracic aorta cast a cane
shaped shadow
 The shadow of ascending aorta projects upward
from the superior limit of the anterior border of
the cardiac shadow
 The shadow of aortic arch arches over the cardiac
shadow and into the radiolucent space anterior to
the bodies of the 3rd and 4th thoracic vertebra
 The shadow of descending thoracic aorta parallels
the curved stack of the bodies of the lower
thoracic vertebrae

Diaphragm outline
• Both diaphragms are visible
throughout their length, except
the left anteriorly where it
merges with the heart. A small
segment of the right hemi
diaphragm is effaced by the IVC.
• The posterior costophrenic
angles are acute and small
amounts of pleural fluid may be
detected by blunting of these
angles.

Lungs
• All fissures of lung are clearly seen on lateral
film.
• The horizontal fissure runs anteriorly and
often slightly downwards
• Both oblique fissures commence posteriorly at
the level of T4 /T5,passing through the hilum.
The left ends 5cm behind the anterior
costophrenic angle and right ends just behind
the angle.

Bones and soft tissues of chest wall
• The radiograph shows the manubrium sterni
and body of sternum in profile.
• Shows the body of thoracic vertebrae, images
of the paired pedicles of each vertebra are
seen.
• The T4-T5 intervertebral disc lies at the level
of manubrio-sternal joint.
• The bodies of thoracic vertebra appear
progressively more radiolucent inferiorly.

• ANTERO POSTERIOR VIEW

Antero-posterior – erect
This projection is used as an alternative to the
postero-anterior erect projection for elucidation of an
opacity seen on a postero-anterior, or when the
patient’s shape or medical condition makes it difficult
or unsafe for the patient to stand or sit for the basic
projection.

Position of patient and cassette
• The patient may be standing or sitting with their back against
the cassette, which is supported vertically with the upper
edge of the cassette above the lung apices.
• The median sagittal plane is adjusted at right-angles to the
middle of the cassette.
• The shoulders are brought downward and forward, with the
backs of the hands below the hips and the elbows well
forward, which has the effect of projecting the scapulae clear
of the lung fields.
• In the unwell patient, it may not be possible to perform this
procedure, In this situation, it is preferable that the patient’s
arms are rotated laterally and supported with the palms of
the hands facing forward. In this position, the scapulae are
superimposed on the lungs but the effect of absorption is
less.

Direction and centering of the X-ray
beam
• The horizontal ray is directed first at right-angles
to the cassette and towards the sternal notch.
• The central ray is then angled until it is coincident
with the middle of the cassette. This has the effect
of confining the radiation field to the film, thus
avoiding unnecessary exposure of the eyes.
• The exposure is taken on normal full inspiration.

Normal antero-posterior radiograph
of thorax

• Antero-posterior - supine

Antero-posterior – supine
This projection is selected
when patients are unable to
either stand or sit for the
projections described
previously. The patient is
usually lying supine on a
trolley or bed.

Position of patient and cassette
• With assistance, a cassette is carefully positioned
under the patient’s chest with the upper edge of
the cassette above the lung apices.
• The median sagittal plane is adjusted at right-
angles to the middle of the cassette, and the
patient’s pelvis is checked to ensure that it is not
rotated.
• The arms are rotated laterally and supported by
the side of the trunk. The head is supported on a
pillow, with the chin slightly raised.

Direction and centering of the X-ray
beam
• The central ray is directed first at right-angles
and towards the sternal notch.
• The central ray is then angled until it is
coincident with the middle of the film, thus
avoiding unnecessary exposure to the eyes.

Normal supine
radiograph of thorax

• ANTERO-POSTERIOR SEMI ERECT

Antero-posterior – semi-erect
This semi-recumbent
position is adopted as an
alternative to the antero-
posterior erect projection
when the patient is too ill to
stand or sit erect without
support.

Normal semi-erect radiograph of thorax. The chin
is just superimposed on the upper thorax

DIFFERENCES OF PA & AP VIEW

S.N POSTERIOR ANTERIOR VIEW ANTEROPOSTERIOR VIEW
1. Clavicles are more horizontal,donot project towards the
apices
Projects towards the apices
2. Scapula are away from the lung field Scapula are towards the lung
field.
3. Reduces radiation dose to radiosensetive organs like
eyes,thyroid and breasts.
Radiation exposure
4. Magnification of heart is reduced Heart size is exaggerated .
5. X-rays pass from the posterior to the anterior of the
patient - hence Posterior-Anterior (PA) projection. The
image is viewed as if looking at the patient face-to-face.
X-rays pass from the anterior
to the posterior of the patient
- hence Anterior-Posterior (AP)
projection. The image is still
viewed as if looking at the
patient face-to-face.
6. Compression of breast tissue against the film cassette
reduces the density of tissue around the cp bases
therefore visualizing them more clearly
no any compressions.

•APICES

Apices
• Opacities obscured in
the apical region by
overlying ribs or
clavicular shadows may
be demonstrated by
modification of the
postero-anterior and
antero-posterior
projections.

Direction and centering of the X-ray beam
• With the patient in the position for the postero-anterior
projection, the central ray is angled 30 degrees caudally towards
the seventh cervical spinous process coincident with the sternal
angle.
• With the patient in the position for the antero-posterior
projection, the central ray is angled 30 degrees cephalad
towards the sternal angle.
• With the patient reclining, and the coronal plane at 30 degrees
to the cassette, to enable the nape of the neck to rest against
the upper border of the cassette, the central ray is directed at
right-angles to the film towards the sternal angle. Alternatively,
if the patient is unable to recline 30 degrees, the technique is
adapted, with the patient reclining 15 degrees and the tube
angled 15 degrees cephalad.

Normal postero-anterior 30 degrees caudad

Antero-posterior 30 degrees cephalad,
showing small tumour at the left apex

•LORDOTIC VIEW

Lordotic view
This technique may be used to demonstrate
right middle-lobe collapse or an inter-lobar
pleural effusion. The patient is positioned to
bring the middle-lobe fissure horizontal.

Position of patient and cassette
• The patient is placed for
the postero-anterior
projection.
• Then clasping the sides
of the vertical Bucky, the
patient bends backwards
at the waist.
• The degree of
dorsiflexion varies for
each subject, but in
general it is about 30–40
degrees.

Direction and centering of the X-ray beam
The horizontal ray is directed
at right-angles to the cassette and
towards the middle of the film.

Lordotic postero-anterior radiograph
showing middle lobe collapse

• Decubitus: the patient is lying down. In the decubitus
position,
• the patient may be lying in any of the following positions:
• • Supine (dorsal decubitus): lying on the back.
• • Prone (ventral decubitus): lying face-down.
• • Lateral decubitus: lying on the side. Right lateral decubitus
–
• lying on the right side. Left lateral decubitus – lying on the
• left side.
• • Semi-recumbent: reclining, part way between supine and
sitting

Heart and lungs – fluid level
Postero-anterior or antero-posterior (lateral decubitus)
This projection is used to confirm the presence of fluid. Moving the
patient into a different position causes movement of free fluid, so that
loculation is also detected. It may also be used to demonstrate the
lateral chest wall of the affected side clear of fluid, and to unmask any
underlying lung pathology.
Position of patient and cassette
• The patient is turned on to the lateral decubitus position and, if
possible, raised on to a supporting foam pad.
• A cassette is supported vertically against the anterior chest wall, and
the median sagittal plane is adjusted at right-angles to the cassette.
• The patient’s arms are raised and folded over the head to clear the
chest wall.

• Direction and centring of the X-ray beam
• • Centre to the level of the eighth thoracic
vertebra, with the central
• ray horizontal and directed at right-angles to the
cassette.
• Alternatively, an antero-posterior projection may
be taken, with
• the cassette supported against the posterior
aspect of the patient

Postero-anterior radiograph in lateral
decubitus position showing pleural effusion
with pneumothorax
Patient positioned for postero-anterior chest
(lateral decubitus) projection

Supine(dorsal decubitus)
This projection will show as much as possible of the lung fields, clear of
a fluid level, when the patient is unable to turn on their side.
Position of patient and cassette
• The patient lies supine and, if possible, is raised off the bed on a
supporting foam pad.
• The arms are extended and supported above the head.
• A cassette is supported vertically against the lateral aspect of the
chest of the affected side and adjusted parallel to the median sagittal
plane.
Direction and centring of the X-ray beam
• Centre to the axilla, with the central ray horizontal and directed at
right-angles to the cassette.

Patient positioned for lateral chest (dorsal
decubitus) projection
Lateral radiograph in dorsal decubitus position
showing pleural effusion with pneumothorax

Right anterior oblique
This projection is used to separate the heart, aorta and vertebral
column on a 35x 43-cm film. The projection will also demonstrate the
diameter and the degree of unfolding of the aorta.
Position of patient and cassette
• The patient is initially positioned facing the cassette, which is
supported vertically in the cassette holder with the upper edge above
the lung apices.
• With the right side of the trunk kept in contact with the cassette, the
patient is rotated to bring the left side away from the cassette, so that
the coronal plane forms an angle of 60 degrees to the cassette.
Direction and centring of the X-ray beam
• Direct the horizontal central ray at right-angles to the middle of the
cassette at the level of the sixth thoracic vertebrae, to show the heart,
aortic arch and descending aorta.

Right anterior oblique radiograph
Right anterior oblique
radiograph with barium outlining
the oesophagus

LIMITATIONS OF THE PLAIN CHEST FILM
First,the radiologist may fail to spot a lesion.Felson
reported that 20-30% of significant information
on a chest film may be over-looked by a trained
radiologist.
Second,a disease process may fail to appear as a
visible abnormality on a plain film.examples
includes miliary shadowing,metastasis,infective
process such as tuberculosis,histoplasmosis,and
pneumocystis,bronchiectasis and small pleural
effusions.such lesions are demonstrated earlier
using high resolution CT.