Chest x ray and other imaging investigations of chest, Basics of Chest Xray, PA view, Lateral view, CT chest, HRCT Chest, MRI Chest, USG Chest, PET/CT Chest, V/Q Scan, Silhouette sign, Cervicothoracic sign, Abdominothoracic sign, Golden S sign, Luftsichel sign, Air Bronchogram

1. Chest X-Ray and other
Imaging investigations of
Chest
Dr Bishnu Khatiwada
MD Resident
Radiodiagnosis, NAMS

2. Methods of Investigations
• Chest X-ray
• CT scanning
• MRI
• PET-CT Scan
• Ultrasound
• Image-guided biopsy
• Ventilation/Perfusion scan (V/Q scan)
• Pulmonary angiography

3. CHEST X-RAY

4. Recommended projections
Basic –PA erect
Alternative - AP erect/supine/semi-erect
Supplementary
Lateral
Decubitus
Oblique
Apical
Lordotic
Inspiratory-Expiratory

5. PA over AP view
• Pros Vs Cons:
Pros:
 Easy positioning
 Heart magnification
low
 Breast compression-
low radiation
 Thyroid- low radiation
Cons:
 Mediastinal & heart
shadow-obscure lung
field
 Other hidden areas

6. Suggested Scheme for viewing
Chest X-Ray PA film
• PATIENT INFORMATION
• TECHNICAL ASPECTS
• TRACHEA
• MEDIASTINUM & HEART
• DIAPHRAGM
• LUNGS
• HILA
• COSTOPHRENIC AND CARDIOPHRENIC
ANGLES
• HIDDEN AREAS
• BONY STRUCTUTRES
• SOFT TISSUE

7. TECHNICAL ASPECTS
• Exposure factors: kVp, mAs, FFD,
exposure time, Focal spot size, Cassette
size, Grid
• Collimation
• Centering/rotation
• Penetration
• Degree of inspiration
• Side markers

8. Low kVp versus high kVp
technique ??
Low kVp: miliary shadows and
calcifications clear,
High kVp: Hidden areas clear, Movement
blur minimized, decreases radiation dose

9. Rotation
• To say no rotation, medial end of both the
clavicles should be equidistant from
vertebral spinous process at the level of T4
or T5.

10. Penetration
• With a low kV film,
the vertebral bodies
and disc spaces
should be just
visible down to the
T8/9 level through
the cardiac shadow.

11. 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

12. On expiration, the heart shadow is larger and there is basal
opacity due to crowding of the normal vascular markings.
Pulmonary diseases such as fibrosing alveolitis are associated
with reduced pulmonary compliance, which may result in
reduced inflation with elevation of the diaphragms.
Inspiration

13. TRACHEA
• Should be examined for:
– Narrowing
– Displacement
– Intraluminal lesions
• Position: Central, slightly deviated towards right
around the aortic knuckle
• Calibre:
– Even
– Translucency decreasing caudally
– Max. Coronal: 25mm(M), 21mm(F)

14. • Azygos vein
– Position: angle between right main
bronchus and trachea
– Less than 10mm diameter-erect position
– Causes of enlargement ?? Supine position, Enlarged
subcarinal LNs, Pregnancy, Portal HTN, SVC/IVC obstruction,
Right heart failure, Constrictive pericarditis
• Carinal angle
– Normal: 60-750
– Causes of widening ?? Enlarged left atrium,
Subcarinal LNs

15. MEDIASTINUM & HEART
• Central dense shadow is formed by:
– Heart
– Mediastinum
– Sternum
– Spine
• Good centring:
– Heart:
• 2/3 left,
• 1/3 right
• In chest x-ray, heart examined for size,
shape, position, silhouette.

16. • Size measurement:
– CT ratio: <50% in PA
view
– Transverse cardiac
diameter:
• <15.5cm (M),
• <14.5cm (F)
• Heart size appears
enlarged in: Short FFD,
on expiration, Supine
film, AP film & when
diaphragms are elevated

17. Right & Left heart borders

18. Thymus
• In babies &young children upto 3yrs
• Normally triangular sail shaped with well
defined borders projecting from one or both
sides of mediastinum
• Borders may be wavy due to indentation by
costal cartilage –wave sign of Mulvey
• Right border straighter than left which may
be rounded
• Causes of decrease in size ?? Inspiration, Severe
infection, Major surgery, Corticosteroid treatment
• Causes of enlargement ?? recovery from illness

19. Thymic wave sign and sail sign in a 5-month-old girl with mild respiratory distress.

20. • In the mediastinum, search should be made for
Abnormal densities
Fluid level
Mediastinal emphysema
Calcifications
• Mediastinum divided into:
– Anterior
– Middle
– Posterior

22. HILA
• Formed by superior
pulmonary vein &
basal pulmonary
artery (radiological
hilum)
• 97%-Left higher
(Why??)
• 3%-Same level
• Hila should be of equal
density, similar size &
clearly defined
concave lateral borders

23. • Structures in the hilum:
1.Pulmonary arteries & upper lobe veins-
significant contribution to hilar shadow
2.Normal LN-not seen in plain radiography
3.Bronchi- walls seen end on

24. • Anterior segment bronchus of upper lobe is
seen as a Ring shadow adjacent to the
upper hilum- Left side in 55% , Right side in
45% cases
• Normally there is less than 5 mm of soft
tissue lateral to this bronchus.
• Thickening of this soft tissue suggests the
presence of abnormal pathology such as
malignancy.

25. Ring shadow of the anterior segment bronchus of the left
upper lobe seen end-on.

26. • The right main bronchus is shorter,
steeper and wider than the left,
bifurcating earlier
• Right upper lobe bronchus arises 2.5 cm
below the carina and is higher than the left
upper lobe bronchus which arises after 5
cm.

27. PULMONARY VESSELS
• Left pulmonary artery –above left main
bronchus
• Right pulmonary artery-anterior to
bronchus
• Diameter-16mm M
-15mm F
• At first intercostal space –normal vessels
not more than 3mm in diameter
• Erect-lower lobe vessels prominent
• Supine-equalize

28. Pulmonary arteries versus pulmonary
veins in CXR ??
Pulmonary veins- Do not follow the bronchi; Fewer
branches; Larger, straighter & less well defined

29. DIAPHRAGM
• Right dome is higher than the left (Why??)
• May lie in same level
• Left higher than the right (3% cases)
• Elevated hemidiaphragm- difference in
height > 3 cm
• Respiratory movement: 3-6cm
• On inspiration, dome of diaphragm are at
the level of- 6th
rib anteriorly, 10th
rib
posteriorly (erect film)

30. • Thickness: 2-3 mm
• In left side, diaphragm and stomach wall
forms a linear density 5-8mm thick
• In right side, thickness cannot be assessed
unless the inferior surface is outlined by
free intraperitoneal gas
• Causes of thickening ?? Tumors of diaphragm,
stomach & pleura, subpulmonary fluid, diaphragmatic
humps, Abdominal lesions (Subphrenic abscess,
hepatomegaly, splenomegaly)

31. • Both domes form gentle curves-
steepen towards posterior angles
• The upper borders are clearly defined
except where heart rests & anterior
cardiophrenic angles (fat pad)
• Loss of outline –indicates the adjacent
tissue doesnot contain air - s/o
consolidation or pleural effusion

32. Normal Variants of
Diaphragm
1. SCALLOPING-Right side; short curves
convex upwards
2. MUSCLE SLIPS-Right side; short curves
concave upwards
3. DIAPHRAGM HUMP &
DROMEDARY DIAPHRAGM-Right
side anteriorly
4. EVENTRATION- Left side, Mediastinal
shift is present
5. ACCESSORY DIAPHRAGM- rare;
asymptomatic; usually right sided

34. Costophrenic Angles
• Acute and well defined
• Obliterated when diaphragms are flat
• Frequently, CP angles contain low density ill
defined opacity caused by fat pads.

35. LUNGS
• Zones: 3 zones
• Lobes: Right- 3 lobes,
Left- 2 lobes
• Should be bilaterally
symmetrical with
normal in
translucency and
bronchovascular
markings

36. • Composite shadow: formed by
superimposed normal structures eg.
Vessels, bones or costal cartilages
• If any radio-opacity is present, look for:
Size, Shape, Location, Calcification,
Cavitation

37. FISSURES
Main fissures:
• Right: Horizontal,
Oblique
• Left: Oblique
Accessory fissures:
• Azygos fissure
• Superior accessory
fissure
• Inferior accessory
fissure
• Left sided horizontal
fissure

38. Main Fissures
• Separate the lobes of the lung but are
usually incomplete allowing collateral air
drift to occur between adjacent lobes.
• Visualised when the X-ray beam is
tangential.
• Horizontal fissure is seen, often
incompletely, on the PA film running from
the hilum to the region of the sixth rib
in the axillary line, and may he straight
or have a slight downward curve.

39. The left image shows the right horizontal fissure (A) and
the inferior borders (B) of the oblique fissures
bilaterally. The right image shows the superior border of
the oblique fissures (B) bilaterally.

40. • All fissures are clearly seen on the lateral
film.
• The horizontal fissure runs anteriorly from
hilum and often slightly downward.
• Both oblique fissures commence posteriorly
at the level of T4 or T5, passing through the
hilum.
• The left is steeper and finishes 5 cm behind
the anterior costophrenic angle, whereas the
right ends just behind the angle.

41. Figure 2. Normal major fissures.

42. Accessory fissures
• Azygos fissure: Formed by laterally displaced azygos vein
creating deep pleural fissure in RUL during embryonic devt.
– comma shaped
– almost always right sided
– forms in apex of lungs
– Consists of parietal &visceral pleura with azygos vein
which has failed to migrate normally
– incidence-0.4%(radiologically), 1%( postmortem)
– when left sided, contain hemi-azygos vein

43. • Superior accessory fissure
– Separates apical from basal segments of
lower lobe
– Common in Right side
– 5% incidence in post-mortem
– On PA film, resembles horizontal fissure
but in lateral film can be differentiated as
it runs posteriorly from hilum.

44. • Inferior accessory fissure:
– separates medial basal from other basal
segments
– appears as an oblique line –from cardiophrenic
angle towards hilum
– Common in Right side
– incidence 5-8% on chest film
• Lt sided horizontal fissure:
- separates lingula from other upper lobe
segments
-8% of postmortem specimens

46. HIDDEN AREAS
1. Apices: partially obscured by ribs, costal
cartilage, clavicles & soft tissues
2. Central lesions obscured by Mediastinum
and hila
3. Posterior & lateral basal segments of
lower lobes are obscured by the
downward curve of the posterior
diaphragm
4. Posterior sulcus
5. Hidden areas due to Bones or costal
cartilages

47. THE BONES
• STERNUM
• CLAVICLES
• SCAPULA
• RIBS
• SPINE

48. • Sternum:
– Ossification centres and parasternal ossicles may be
confused with lung masses
• Clavicles:
– Rhomboid fossa- irregular notch at the site of
attachment of costoclavicular ligament, lies upto 3cm
from medial end of clavicle inferiorly and has well
corticated margins
– Superior companion shadow
– Medial epiphysis-fuses at 25 yrs –appear as lung
nodule occasionally

49. • Scapula:
– In PA film, spine seems to be pleural shadow
– In Lateral film, inferior angle seems to be lung
mass
• Ribs:
– Companion shadows –common in upper ribs
– Costal cartilage calcification
• Spines:
– In PA film, end of transverse process-may
simulate a lung nodule
– In neonates, vertebral bodies have a sandwich
appearance due to large venous sinuses

50. SOFT TISSUE
• General survey in chest wall, shoulders & lower neck.
• Breast shadows- absence u/l or b/l
• Nipple shadows- how to differentiate??
• Skin folds- may simulate pneumothorax
• Anterior axillary fold- curvilinear,axilla to lung field
(DD: Consolidation)
• Apices-opacity of sternocleidomastoid (DD: Cavity or
Bulla)
• Floor of supra clavicular fossa- often resembles fluid
level
• Apical pleural thickening ~the apical cap ~has a
reported incidence of 7%- most commonly on the left
side

51. LATERAL VIEW
• Routinely left lateral film obtained
(Why??)
• In specific lesion, the side of the interest is
positioned adjacent to the film
• Confirmation of intrapulmonary nature of
a lesion
• Hilar & Mediastinal masses

52. Suggested scheme for viewing Lateral film
• CLEAR SPACES
• VERTEBRAL TRANSLUCENCY
• DIAPHRAGM OUTLINE
• FISSURES
• TRACHEA- bifurcates at T6/7 level
• HEART
• SHADOWS OF AXILLRY FOLDS &
SCAPULA
• STERNUM

53. Clear Spaces
• Retrosternal and Retrocardiac
• Retrosternal space:
– <3cm deep
– Obliteration: Anterior mediastinal mass, RA
enlargement
– Widening: Emphysema

55. Left Vs Right dome of Diaphragm
• Anterior left hemidiaphram is obliterated by the
cardiac contact; right is seen in entirity
• By identifying the fissures: left oblique fissure
contacts diaphragm ~5cm behind the anterior
costophrenic angle
• On left lateral film, the right anterior and posterior
costophrenic sulci should project beyond the
corresponding left sided sulci as a result of x-ray
beam divergence
• By noting fundic gas and splenic flexure below
the left hemidiaphragm

56. Lines and stripes
• Lines: <1mm
• Stripes: thicker
• Formed when structures of different
densities come in contace with one another.
E.g: Right paratracheal stripe, Anterior &
Posterior junctional lines, Right & Left
paraspinal lines, Azygoesophageal recess
• Better seen in high kVp films

57. Anterior junctional line
• Formed by the lungs meeting anteromedially
anterior to the ascending aorta.
• 1 mm thick and, overlying the tracheal
translucency (@A=1)
• Runs downward from below the suprasternal
notch, slightly curving from right to left.
• Seen in 40% of the cases

59. Posterior junctional line
• Form where the lungs meet
posteromedially posterior to the
oesophagus
• Straight or curved line convex to the left
measuring 2 mm wide
• Extend from the lung apices to the aortic
knuckle or below.
• Seen in 32% of the cases

61. • Seen in 60% patients
• Less than 5mm width
• Pathological widening
1.Mediastinal lymphadenopathy
2.Mediastinal tumors
3.Mediastinis
4.Tracheal malignancy
5.Pleural effusion
Left paratracheal stripe-not visualized (Why??)
Right paratracheal stripe

63. Right and Left Paraspinal Lines
• Formed by tangential contact of the lung
and pleura with the posterior mediastinal
fat, paraspinal muscles, and adjacent soft
tissues
• Right: <3mm, Left: <10mm (Why??)
• Causes of enlargement ?? Osteophytes, Tortous
Aorta, Vertebral & adjacent soft tissue masses,
Paravertebral abscess/hematoma, Dilated azygos system

65. Azygo-oesophageal recess
• “Inverted hockey stick” shaped
• Runs from the diaphragm on the left of
midline up and to the right extending to
the tracheobronchial angle where the
azygos vein drains into the IVC.

66. Right Pleuro-oesophageal stripe
• Formed by the lung and right wall of the
oesophagus
• Extends from the lung apex to the azygos
but is only visualised if the oesophagus
contains air.
• The left wall of the oesophagus is not
normally seen.

67. CT Chest
Advantages:
1.Confirmation of exact anatomical location &
extent of disease
2.Mediastinal & chest wall involvement by
pulmonary pathology
3.Ascertaining the solitary nature of a
pulmonary nodule & detection of other
unsuspected nodules
4.Determination of probability of malignancy

68. 5. Staging
6. Monitoring response to treatment
7. CT-guided biopsy

69. High Resolution CT Chest (HRCT)
Principles:
1. Thin sections (1-3mm)
2. Narrow beam collimation
3. Narrow field of vision (i.e. using a field of view
just large enough to encompass the region of
interest)- results in higher definition of appearance
of pulmonary parynchymal disease
4. Bone algorithm for image reconstruction (i.e. high
spatial resolution reconstruction algorithm)

70. Indications:
1.Interstitial lung disase
2.Bronchiectasis
3.Small Airway Disease & Emphysema
4.Miliary Tuberculosis
5.To identify the regions most suitable for
biopsy when CXR is normal

71. MRI
Advantages:
1. To differentiate Mediastinal & hilar masses from
normal or abnormal vessels
2. Evaluation of cranio-caudal extent of large lesions
3. Evaluation of Lung apex, lung base & chest wall
4. Invasion to major vessels & brachial plexus
5. Can be used in patients allergic to iodinated
contrast media

72. PET/CTPET/CT
• Advantages better detection of
mediastinal metastases improving staging
of lung cancers, also to detect occult
extrathoracic metastases and synchronous
extrathoracic primary malignancies
• Principle- Increased Fluorine-18 labelled
FDG uptake by malignant tumors

73. • FDG uptake expressed as standardized uptake
ratio (SUR) to normalize measurements for a
patient's wt & injected dose of radioisotope.
SURs >2.5 have been used by some as a
marker of malignancy.
• For >10mm lesions- Sensitivity 97% &
Specificity 78%
• False negative in :<10mm lesions &
Metabolically hypoactive lesion (Carcinoid,
Adenocarcinoma & BAC).
• False positive in: infective and inflammatory
lesions.

74. Ultrasound
• Useful only for assessing and taking
biopsy from superficial pulmonary,
pleural-based and chest wall lesions
• Diagnosis & aspiration of pleural
collections

75. Ventilation-Perfusion scan (V/Q scan
Indications:
1. Suspected pulmonary embolism
2. Assessment of regional lung function in patients with
focal lung disease who may be candidates for surgery
e.g. Lung tumors, Bullous emphysema, Bronchiectasis,
Congenital heart disease
• Perfusion scintigraphy: uses technitium-labelled
albumin particles-trapped in precapillary arterioles
• Ventilation scintigraphy: uses Krypton-81m or
Rubidium-81- radioactive gas with gamma emission

76. • V/Q Match: Perfusion decreased,
Ventilation decreased
• V/Q Mismatch: Perfusion decreased
• V/Q Reverse Mismatch: Ventilation
decreased

77. Pulmonary Angiography
Indications:
1.Diagnosis of Pulmonary embolism
2.Evaluation of pulmonary hypertension
3.Diagnosis of vascular lesions e.g.
Pulmonary artery aneurysm, AVMs
4.Embolisation of pulmonary AVMs

78. Helpful Radiological Signs

79. The Silhouette sign
• Loss of an interface by adjacent disease and
permits localization of a lesion on a film by
studying the diaphragm, cardiac and aortic
outlines.
• These structures are normally seen because the
adjacent lung is aerated and the difference in
radiodensity is demonstrated.
• When air in the alveolar spaces is replaced by
fluid or soft tissue, there is no longer a difference
in radiodensity between that part of the lung and
the adjacent struetures. Therefore the silhoutte is
lost and the ‘silhoette sign' is present.

80. Silhouette Adjacent
Lobe/Segment
Right hemidiaphragm RLL/Basal segments
Right heart margin RML/Medial segment
Ascending aorta RUL/Anterior segment
Aortic knuckle LUL/Apicoposterior segment
Left heart margin Lingula/Inferior segment
Descending aorta LLL/Superior segment
Left hemidiaphragm LLL/Basal segments

81. Localization of lesion in chest x-ray

82. Hilum Overlay Sign
• If the hilum can
be seen through
the mass, it
means that the
mass seen is
either in front
of or behind it.

83. Cervico-Thoracic Sign
• Lesion extending
above the clavicles
with clearly visible
upper borders lies in
posterior mediastinum
• If not clear Cervico-
thoracic lesion (partly
in anterior
mediastinum and
partly in neck)

84. Thoraco-Abdominal Sign
• Lesion extending
below the dome of
diaphragm must be
in posterior sulcus
whereas lesion
terminating at dome
must be anterior.

85. Golden ‘S’ Sign
• When there is
presence of hilar
mass with collapse,
the fissure takes the
shape of an "S".
• The proximal
convexity is due to
a mass, and the
distal concavity is
due to atelectasis.

86. Luftsichel sign (Luft=air, sichel=crescent)
• In LUL collapse,
hyperexpanded
superior segment of
the left lower lobe
produces a crescent
of lucency between
the atelectatic left
upper lobe and the
aortic arch.

87. The Air Bronchogram
• Important sign showing that an opacity is
intrapulmonary.
• The bronchus, if air filled but not fluid
filled, becomes visible when air is displaced
from the surrounding parenchyma.
• Frequently, the air bronchogran is seen as
scattered linear transluceneies rather than
continuous branching structures.

89. Causes of Air Bronchogram
Common
• Expiratory film
• Consolidation
• Pulmonary oedema
• Hyaline membrane
disease
Rare
• Lymphoma
• Alveolar cell
carcinoma
• Sarcoidosis
• Fibrosing alveolitis
• Alveolar proteinosis
• ARDS
• Radiation fibrosis

90. References
• Textbook of Radiology and Imaging, David
Sutton, 7th
edition

91. Thank You!!