This document provides information on reading and interpreting chest x-rays. It begins with background on x-rays and radiographic densities seen on chest films. It describes the important details to note before interpreting a chest x-ray, including patient information, view, exposure, and breath status. The four main views of chest x-rays are described. Key structures seen on chest films are outlined, including the heart, diaphragm, lungs, and interfaces. Common abnormalities like pleural effusions, pneumothorax, and cardiomegaly are discussed. The document provides a thorough guide to evaluating all aspects of the chest on x-ray films.

1. READING CHEST X-RAYS
Dr. Samriddha Pokharel
Jalalabad Ragib-Rabeya Medical College, Sylhet

2. X-RAYS
X-rays are a form of electromagnetic radiation.
Wavelength(λ) : 10 picometres to 10 nanometres (10×10−12 m) to (10×10−9)
(Shorter than visible and UV Rays and longer than Gamma
Rays)
Frequencies(f) : 30 petahertz to 30 exahertz (3×1016 Hz to 3×1019 Hz)
Energy(E) : 100 eV to 200 keV
Discovered by: Wilhelm Conrad Roentgen (Father of Radiology) in 1895A.D.

3. RADIOGRAPHIC DENSITIES/GRAYSCALE
• Different body tissues absorb X-Rays at different extents.
 Gas (air in the lungs) » Least dense/Least absorption of X-Rays » Black(Radiolucent)
 Metal/Bone » More dense/Absorb more radiation » White(Radiopaque)
White – Metal
Off White – Bone
Light grey – Soft
Tissue
Dark Grey – Fat
Black - Air

4. BEFORE INTERPRETING THE X-RAY….
• Patient’s Details and Site Determination(left side and right side)
• View : Postero-Anterior or Antero-Posterior
• Exposure of the film to radiation
• Rotation of the patient
• Breath : Inspiration or Expiration
Mnemonic- P-VERB
o In exam, the X-ray provided will be an inspiratory film with adequate exposure and
usually of posteroanterior view(children’s x-ray may be anteroposterior)

5. 4 MAJOR VIEWS OF THE CHEST RADIOGRAPH
PosteroAnterior- 1.Most commonly preferred.
2. Standard view for Chest X-rays.
3.Patient stands upright with the chest placed on the film after
full inspiration.
AnteroPosterior- 1.Used in debilitated , very ill , uncooperative patients and in
children.
Lateral - 1. Usually done in conjunction with PA view Chest X-Ray
2.Lung lobes and lobar pathology, Mediastinum and its pathology e.g.
Mediastinal mass, Thoracic wall and basal consolidation can be better
visualized.
Lateral Decubitus - 1.Specialized projection used to demonstrate small pleural
effusions or pneumothorax.

6. A-P VIEW FILM VS P-A VIEW FILM
Points PA view AP view
Clavicle Over the lung fields Above lung apex
Scapulae Away from lung fields Over lung fields
Ribs Posterior ribs distinct Anterior ribs distinct
Heart Close to the anatomical size Relatively enlarged

7. LATERAL DECUBITUS VIEW
 200ml or more fluid is needed to see blunting of costophrenic angle on
Postero-Anterior view.
 Lateral view X-ray can show blunting of costophrenic angle when there is
100ml of pleural fluid.
 Lateral decubitus view can show free flowing fluid in the pleura <50ml

8. EXPOSURE OF THE FILM TO
RADIATION/PENETRATION
• On an adequately exposed chest radiograph ,the lower thoracic vertebrae are visible
through the heart and the Broncho-vascular markings(trachea ,aortic arch , etc.)
must be seen.

9. GOOD INSPIRATORY FILM:
• On a proper Inspiratory chest radiograph:
 First 6 Anterior ribs are visible.
 First 10 Posterior ribs are visible.

10. ROTATION
• If the spinous process of vertebral body is equidistant from the medial ends of clavicle, there is NO
rotation.
• Rotation results in reduced distance on the side in front.
Here, reduced
distance is on
the left
meaning the
left side is in
front. Hence,
the patient is
rotated
towards right.
NO Rotation

11. INTERPRETING CHEST X-RAYS

12. ABCDEFGHI APPROACH
• Airway
• Bones and Soft tissue
• Cardiac Shadow
• Diaphragm
• Effusions(Pleura)
• Fields(Lungs)
• Gastric Bubble (Fundic gas)
• Hila and Mediastinum
• Impressions (of tubes or pacemakers)
For studying it is easier to follow ABCDEFGHI approach however for exams Outside to inside approach
will be a faster method.

13. FIRST LET’S LOOK AT DIFFERENT STRUCTURES AND THEIR
NORMAL ANATOMY WITHIN THE RADIOGRAPHIC FILM
POSTERO-ANTERIOR
VIEW
A- Costo-phrenic
angle
B-Diaphragm
C-Heart
D-Aortic knob
E-Trachea
F- Hilum and
Pulmonary artery
G-Carina
H- Fundic gas
J-SVC

14. LATERAL VIEW
A- Costo-phrenic
angle
B-Diaphragm
C-Heart
D-Aortic knob
E-Trachea
F- Hilum and
Pulmonary artery
G-Carina
H- Fundic gas
J-SVC

15. INTERFACES IN THE CHEST RADIOGRAPH
• An interface is formed when two structures of significantly variable densities are in front
of one another .
• In Chest X-ray , interface lines are seen on the lung fields due to variable densities of the
lung(gas) and other organs(soft tissues).

17. SILHOUETTE SIGN:
• The X-ray image will depend on the sum of various densities encountered by
the X-ray beam as it courses through the body.
• If the structures of similar densities are juxtaposed then the anatomical soft
tissue border(interface lines) will not be visible. This is called SILHOUETTE
SIGN.
Here, there is juxtaposition of heart and
consolidated lung which are of similar
densities. Hence, the left heart border is
not visible.

18. AIRWAY
PA
VIEW
LATERAL
VIEW
CARIN
A

19. AIRWAY
• Trachea lies centrally and appears as a vertical black rectangle.
Slight tracheal deviation towards right is Normal.
Extension : Larynx(C6) to Carina(T4/T5) Length: 10-12cm
Bifurcates at the level of sternal angle.
Transverse diameter : approx. 19.5mm in male and 17.5mm in
female
Deviation towards the lesion Deviation away from lesion
Lobar collapse(esp. upper
lobe),Pneumonectomy
Large Pleural Effusion
Pulmonary Fibrosis Tension Pneumothorax
Some
Mediastinal
Masses may also
cause Tracheal
Deviation.

20. • Carina is an important landmark during endotracheal intubation.
• The Endotracheal tube should end 5mm(+/-2mm) above Carina
• Sub carina angle should be less than 90º.
AIRWAY
INTUBATION
End of ETT
Carina
SUB CARINA
ANGLE
RIGHT AND LEFT PRINCIPAL(MAIN
STEM) BRONCHI AND THEIR
BRANCHES

21. BONES AND SOFT TISSUE
• Bones
1. Look at each rib in turn and look for any pathologies.
2. Count the ribs (From posterior to anterior following the arc).
3. Look at the clavicles.
4.Look at the spine.
5. Look for pathologies in other surrounding bones i.e scapula and humerus.
Counting Ribs Right Lateral
Scoliosis

22. RIB NOTCHING
• Deformation in Superior or Inferior surface of the ribs is known as rib notching.
Notice the notches in the inferior aspect of
the ribs shown by arrows.
Superior Rib Notching Inferior Rib Notching
1.Osteogenesis
Imperfecta
2.Poliomyelitis
3.Hyperparathyroidism
4.Collagen Vascular
disease
5.Large
Neurofibromatosis
1.Coarctation of Aorta
2.Superior Vena Caval
Obstruction.
3.Arteriovenous Fistula
4. Following Blalock
Taussig Shunt
5.Neurofibromatosis
Type1
CAUSES:

23. • Soft tissue
1. Thick soft tissue may obscure lung markings
2. Breast tissue may obscure cost-phrenic angle
Breast tissue
LOOK FOR:
1.Enlarged nodes in
Supraclavicular
fossa.
2.Surgical
Emphysema in the
lateral thoracic
wall.
3.Pneumoperitoneum
Under the diaphragm.

24. • Pneumoperitoneum Subcutaneous Emphysema
(Notice the air within the lateral
thoracic wall)

25. CARDIAC SHADOW
• Right and Left radiological heart borders
 The Radiological right heart border is formed by:
1. Right Atrium 2. Part of Superior Vena Cava
 The Radiological left heart border is formed by:
1. Left Atrium 2. Left Ventricle 3. Aortic knuckle(knob) 4. Pulmonary
trunk
 Inferior Radiological border of heart is formed by :
1. Right Ventricle

26. CHAMBERS OF THE HEART ON CHEST X-RAY PA VIEW

27. CARDIO-THORACIC RATIO
• (CR+CL)<(T/2)
• Normal Cardio-Thoracic ratio is less than 0.5 in adults [(CR+CL)/CT<0.5]
T

28. CARDIOMEGALY
• LEFT ATRIAL ENLARGEMENT:
Causes:
1. Mitral Stenosis, Mitral
Regurgitation
2. Left Ventricular Failure
3. Ventricular Septal Defect
4. Patent Ductus Arteriosus
5. Left Atrial Myxoma
RIGHT ATRIAL ENLARGEMENT:
Causes:
1.Pulmonary Hypertension
2. Tricuspid stenosis, Pulmonary
Stenosis
3. Tetralogy of Fallot
4. Cor Pulmonale
5. Rt. Ventricular failure
RIGHT VENTRICULAR ENLARGEMENT:
Causes:
1. Pulmonary Hypertension
2. Tricuspid insufficiency
3. Atrial Septal Defect
LEFT VENTRICULAR ENLARGEMENT:
Causes:
1. Hypertension
2. Aortic Stenosis
3. Ventricular Septal Defect
4. Aortic Regurgitation, Mitral

29. LEFT ATRIAL ENLARGEMENT AND IT’S SIGNS
SEEN IN MITRAL STENOSIS
SIGNS:
1. Cardiothoracic ratio is greater than 0.5 in adult.
2. Double Right Heart Border (Double density) { blue and white lines}
3. Straightening of the left heart border{ red line} [ Later, the straight border may
turn convex outward(third mogul sign)
4. Splaying of carina
( sub carinal angle >90º) due to
elevation of left main stem bronchus
{ yellow }

30. RIGHT ATRIAL ENLARGEMENT
• Cardiomegaly with enlargement towards the right and posteriorly
• Prominent right superior border
• Right Atrial Margin is 5.5cm(or more) away from midline.

31. RIGHT VENTRICULAR HYPERTROPHY IN
TETRALOGY OF FALLOT
• Right Ventricular hypertrophy with upturned cardiac apex. BOOT SHAPED
HEART
• Oligaemic(decreased pulmonary vascular marking) lung fields.

32. LEFT VENTRICULAR ENLARGEMENT
• Cardiomegaly with downturned cardiac apex.
• Depressed left hemi-diaphragm.

33. SOME RADIOLOGICAL SIGNS SEEN IN CARDIAC
DISEASES
Total Anomalous Pulmonary
Venous Drainage
(Snowman Sign)
Partial Anomalous
Pulmonary Venous Drainage
(Scimitar sign)

34. Transpostion of great arteries
(Egg sign)
Ebstein’s Anomaly
(Box sign)

35. Coarctation of Aorta
(3 sign on PA view)
(Reverse 3 on Lateral view)
Thoracic Aortic Aneurysm Tubular heart in COPD.
Also, notice the hyperinflated
lung and lowered down
diaphragm.

36. DIAPHRAGM
• Both the domes of the diaphragm should from a sharp contour with the lateral chest wall.
• Costo-phrenic angle must be sharp and usually around 30º.
• Most common cause of blunting of costo-phrenic angle is pleural effusion. Blunting may also
be caused by basal consolidation.
• Pleural effusion first obliterates costo-phrenic angle then cardio-phrenic angle.

37. EFFUSIONS(PLEURA)
• Pleura is only visible on a radiology film when there is a pathology.
• Some common pathologies of pleura are:
1.Pleural Effusion 2.Pneumothorax 3.Pleural thickening
4.Hydropneumothorax

38. PLEURAL EFFUSION
RADIOLOGICAL FINDINGS:
• This is a Chest X-ray PA View showing dense homogeneous opacity on the left lung field throughout
the lower and part of middle zone with a concave margin upwards.
The costo-phrenic angle, cardio-phrenic angle and heart border on the left are obscured.
‘Dense Homogeneous’ is used when the radiographic density of the opacity is same as that of liver.
DIAGNOSIS: Left sided Pleural Effusion.

39. RADIOLOGICAL FINDINGS:
• This is a Chest X-ray showing dense homogeneous opacity throughout the left lung field with
obliterated cardio-phrenic, costo-phrenic angles and left heart border. There is Tracheal and
Mediastinal Deviation towards the right.
DIAGNOSIS: Left Sided Massive Pleural Effusion(with trachea and mediastinal deviation towards
right)
Tracheal
Shift
Exudative causes (having
protein rich fluid)
Transudative causes
1.Pneumonia
2.Tuberculosis
3.Malignancies
4.Pulmonary Embolism
1.Congestive heart
failure
2.Cirrhosis
3.Nephrosis
CRITERIA FOR EXUDATIVE PLEURAL FLUID:
(any 1 of the following criteria must be met)
o Pleural Fluid protein/Serum protein>0.5
o Pleural fluid LDH/Serum LDH>0.6
o Pleural fluid LDH>2/3rd of upper normal serum limit

40. PNEUMOTHORAX
The radiological film shows a Hypertranslucent area on the left lung field near the
apex without any Bronchovascular margin. On close inspection, a visible pleural
margin is seen infero-medially to this area.
DIAGNOSIS: Left sided Pneumothorax
An, expiratory film should be
ordered if someone is suspected of
Pneumothorax which shows the
area clearly.

41. TENSION PNEUMOTHORAX (ONE WAY VALVE)
• When excessive amount of air is trapped within the pleural spaces under positive
pressure causing mediastinal and tracheal shift, it is called tension pneumothorax.
Deviated Trachea with ETT
Tension Pneumothorax

42. PLEURAL THICKENING
• Notice the Peripheral shadowing on the right side with decreased lung field.
Some causes of pleural
thickening:
1. Chronic lung infections
like TB
2. Asbestosis, Silicosis
3. Malignancies such as
Mesothelioma,
Metastasis
4. Post Radiation

43. HYDROPNEUMOTHORAX
• Notice the homogeneous dense opacity on the right lung field with horizontal upper
border and the lack of any bronchovascular markings above it. This is called an Air-fluid
level.
• Most common cause of Hydropneumothorax is Iatrogenic (air is accidently introduced
during drainage of pleural effusion)

44. FIELDS
• ZONES
Upper: superior to the lower margin of 2nd rib anteriorly
Middle: lower margin of 2nd rib to lower margin of 4th rib anteriorly
Lower : Below lower margin of 4th rib anteriorly
Lungs can also be divided by 2 vertical lines into 3 areas .
Medial1/3rd
Middle1/3rd
Lateral1/3rd
Notice, the braonchovascular
markings are clear and well
defined in the medial 1/3rd
Become smaller in the
middle 1/3rd and appear as
fine patterns of branching
lines in the medial most part
of lateral 1/3rd .

45. LOBAR ANATOMY

46. HIDDEN AREAS IN THE LUNG FIELDS
• Some areas in the lung fields are hidden due to the soft tissues or bones
superimposing on them.

47. NORMAL CHEST X-RAY (RED) COMPARED TO
RADIOPAQUE (BLUE) AND HYPERTRANSLUSCENT
(GREEN) FILMS

48. PLETHORIC AND OLIGEMIC LUNG FIELDS
• Plethoric lung field means increased
bronchovascular markings due to increased
pulmonary blood flow.
Causes:
1.Left to right shunts (ASD,VSD,PDA)
2. Transposition of great vessels
3. Partial or Total anomalous pulmonary
venous return
• Oligemic lung field means decreased
bronchovascular markings due to decreased
pulmonary blood flow.
Causes:
1. Tetralogy of fallot
2. Right to left shunt in Pulmonary stenosis or
atresia, Tricuspid atresia
3. Pulmonary Embolism ( Westermark sign)-

49. CONSOLIDATION
Consolidation is an airspace disease that involves filling of the alveolar space with fluid(pulmonary edema), pus( as
in pneumonia), blood or even cells(in carcinomas).
Areas of consolidation appear white most often with ill defined margins.
Air Bronchograms : Air spaces in the alveoli become opacified while the bronchi remain air filled making them
appear as small black thin tubular structures within the white area of consolidation.
Notice the small black
streaks running through
the white area.

50. CONSOLIDATION
• Patterns to look for:
1. Diffuse/ Patchy/ Focal
2. Perihilar/ Peripheral
3.Unilateral/ Bilateral
4.Segmental/ Lobar
• Identify the zones that the consolidation covers.
• For lobe identification on PA View:
1. Upper lobe consolidation lies superior to the major
fissure often producing a sharp margin. It silhouettes with the
superior mediastinum.
2. Middle lobe consolidation silhouettes the right heart
margin.
3. Lower lobe consolidation silhouettes the hemi-
diaphragm.
4. Lingular consolidation appears close to the left heart
border.
Small focal area of
consolidation on the right
lung field in the right
lower zone and peri-hilar
consolidation on the left
lung field typical of
Bronchopneumonia
Patchy consolidation
In the right lower
zone .

51. SOME PRESENTATIONS OF TUBERCULAR CONSOLIDATION
Chronic TB
presenting as
calcified
lesions in the
right middle
and lower
zones and left
middle and
lower zones
close to the
cardiac
shadow.
Patchy reticular
opacities in the
right upper and
middle zones .

52. • INTERSTITIAL PULMONARY EDEMA
Findings:
1.Septal lines( Kerley B Lines)
2. Peribronchial cuffing (small doughnut shaped
rings representing fluids in the thickened bronchial
wall)
3. Pleural effusions and Fluid between fissures
can also be seen.
With increase in extravascular fluid from
pulmonary capillaries to the interstitium the fluid
moves centrally making these signs more
prominent.
PULMONARY EDEMA

53. • ALVEOLAR PULMONARY EDEMA is caused by fluid leaking from the interstitial tissues
into the alveoli and presenting as consolidation.
Alveolar edema radiates symmetrically from hilar regions in a ‘bat’s wing’ appearance.
Cardiogenic causes of alveolar edema most often show enlarged heart shadow.

54. SEPTAL LINES
• Kerley A lines:(White arrows) linear
opacities from periphery to hila caused by
distension of anastomotic channels
between peripheral and central lymphatics
• Kerley B lines:(white arrow heads) short
horizontal lines situated perpendicularly
to the pleural surface close to the lung
base.
• Kerley C lines : (black arrow heads) radial
opacities away from hilum

55. CAVITARY LESION
• Cavitary lesions are seen as an area of radiopaque margin with hypertransluscent
area within it.
• Lung Abscesses are cavitary lesions with radiopaque margin and having an air-fluid
level within it.
• Cavitary lesions can be seen in Malignancies, TB, etc.
Lung abscessCavitary
Lesion

56. GASTRIC BUBBLE

57. HILA
• Hilum is the area on the medial aspect of lungs through which Bronchi, vessels and
nerves enter and exit the lungs.

58. PULMONARY VASCULAR PATTERN
• Normal lung vascular pattern has following features:
1. Arteries and Veins branching vertically to upper and lower lobes.
2. The Upper lobe vessels have smaller diameter than lower lobe vessels on an erect Chest X-
ray.
 In Pulmonary Venous Hypertension, vessels branching upwards have a larger diameter than
the vessels branching downwards. This is known as ‘Cephalization’.

59. IMPRESSIONS OF TUBES OR DEVICES
Chest X-Ray with Left
Ventricular Assist DeviceChest x-ray showing metal suture
wires after Sternotomy

60. PRACTICE QUESTIONS

63. Thank You