Ultrasound uses sound waves to create images of internal organs. When sound waves hit tissues, they are reflected, refracted, scattered, or absorbed depending on the acoustic impedance of the tissues. Differences in acoustic impedance between tissues lead to echoes that appear on the screen. Lung ultrasound can detect consolidation, edema, pneumothorax, and pleural fluid. A normal lung shows the pleural line and A lines, while edema appears as B lines originating at the pleura. Pneumonia appears as irregular hypoechoic consolidation with air bronchograms. Atelectasis can be differentiated based on findings of pleural effusion and air bronchograms. Diffuse B lines indicate interstitial syndrome while focal B

2. Chest Ultrasound
Dr. Haitham Salah
Lecturer of Pulmonary medicine
Ain shams University
Organized by Dr. Mohammed Fathi El Bagalaty
Assistant lecturer of pulmonary medicine

3. CHAPTER – I
Physics of Chest Ultrasonography

4. How is the
image of the
examined
object created
on the screen
:-
 When a pulse of ultrasound energy is
incident upon the body, it interacts with
the tissue in a variety of ways:-
(1)The time delay between the energy going
into the body and returning to the
ultrasound probe determines the depth from
which the signal arises, with longer times
corresponding to greater depths. This
information is used in the creation of an
image.
(2) Other factors that make the tissues
distinguishable on a screen are their slightly
different acoustical properties; one is known
as the acoustic impedance.

5. How is the image of the
examined object created on
the screen :-
(3) Acoustic impedance mismatches
across the variant interfaces between
different structures.
At the boundary between two different
tissue types (interfaces) the sound
waves can be:-
(a) Reflected.
(b) Refracted.
(c) Scattered.
(d) Attenuated or absorbed.

6. How is the image of the examined
object created on the screen :-
 Acoustic shadowing:-
 Is so common in ultrasound images that it is sometimes
called an artifact.
 It is the result of the energy (of transmitted sound) that is
being decreased by reflection and/or absorption.
 The shadowing behind gas is due to strong reflections at
gas/tissue interfaces.
 The reflected pulse interacts with interfaces in front of
the gas causing secondary reflections, which leads to low
level echoes, causing ‘dirty’ images.
 However, the shadowing that occurs behind stones,
calcifications and bones is reduced by sound absorption,
resulting in only minimal secondary reflection, and
therefore ‘clean’ images with a distinctly bordered lack of
echoes posterior to the calcified density.

7. Posterior acoustic shadowing:
o Ultrasound wave hits a substance that causes near
total reflection .
o Everything behind the blocking structure appears
black (since no energy is getting through)
o Common causes
o Bone (rib) ,gallstones, calcification
Posterior acoustic enhancement:
o Ultrasound waves pass through an area of low
resistance with little attenuation (ie little loss of
energy)
o As it hits a denser substance behind it, the energy
is dispersed and “lights up” the deeper tissues
o Common causes Cyst, Gallbladder, Bladder Ovarian cyst
Gallbladder stone

8. Degree of Echogenicity: -
 Is determined by the ability of an object to produce or generate echo
reflections.
The more reflection of the echoes, the
more data is received,
the more echogenicity of the image
received from the examined object.

10.  Degree of such reflections dose not
depend only on the nature or the
consistency of the examined objects it
self, but it depends largely on the
degree of the difference between
echo velocities between two different
kinds of medias (Acoustic
impedance mismatches).
 Echo velocity is maximum in bone,
lesser in tissues, lesser in fluid and
least in the air media.
Degree of Echogenicity: -

11. So, Lung appears echogenic due to
large difference (i.e. more echo
reflections) of echo velocity
between soft tissue of the lung
parenchyma and the inside air.
 Pleural line appears echogenic
due to the large difference of echo
velocity between soft tissue of
chest wall and the inside of the
pleural cavity and then between the
inside of the pleural cavity and soft
tissue of the lung.
Degree of Echogenicity: -

12.  Pleural effusion appears anechoic as the
echoes dose not exhibit any change in its
velocity while traveling through out the
pleural fluid
(i.e. no echoes is reflected) no echoes is
reflected from the homogenous medias.
Degree of
Echogenicity: -
 Lung collapse, consolidation or tumors
appearing relatively echogenic due to less
echo velocity difference (i.e. less echo
reflections) between these pathologies and
surrounding normal lung parenchyma.

13. Technique of lung ultrasound:-
 In the supine position, the anterior and lateral
lung areas can be easily scanned, but the
patient may have to be turned to a lateral
decubitus position for scanning posteriorly.
 Seven regions, delineated by the anterior and
posterior axillary lines should be systematically
examined: upper and lower parts of the
(Anterior, Lateral and Posterior chest wall.)

14. CHAPTER- II
Diagnostic Thoracic Ultrasonography

15. The Normal Thorax:-
With a high-resolution linear probe:
 the visceral and parietal pleura can be seen
as two distinct echogenic lines, with the latter
seemingly thinner in appearance.
 The two layers can be seen to slide over each
other during inspiration and expiration.
 The respiratory movement of the lung
relative to the chest wall is visible with both
probes and is called the ‘lung sliding’ sign.
 Its presence on real-time US is strong
evidence against the presence of a
pneumothorax.
The typical appearance of a normal chest on US. S: Skin, CW: chest
wall, P: pleura, Pp: parietal pleura, Pv: visceral Pleura, L: lung, R:
reverberation artifact.

17. Normal appearance of longitudinal
ultrasonographic view of the lung.

18. M-mode placed through the pleural line generates the sea-shore sign.
This is equivalent to the presence of sliding lung

19. Important Findings of Lung
Ultrasonography:-
 Lung ultrasonography is superior to standard supine
radiography and similar to chest CT in detecting many
findings that are important to the Intensivists.
 It is able to detect lung consolidation, alveolar-
interstitial fluid accumulation, normal aeration pattern,
pneumothorax and pleural fluid

20. Lung Sliding:-
 A lung image obtained with a 3.5-MHz
transducer.
 The depth has been adjusted to
examine the pleural interface.
 The transducer is held perpendicular
to the skin surface in a longitudinal
orientation and centered between
intercostal spaces.
 The rib shadows are present on
either side of the image and the pleural
line appears as a horizontally orientated
hyperechoic line approximately 0.5 cm
deep to the origin of the rib shadows.

21. Lung
Sliding:-
 The pleural line represents the interface of
the visceral and parietal pleural surfaces.
Normally, the two pleural surfaces move
across each other during the respiratory
cycle.
 This causes the finding of lung sliding,
which is seen as movement of the pleural
line in synchrony with the respiratory cycle
 The chest wall is immobile and separated
from the underlying lung aeration pattern
by the mobile pleural line. In addition to
lung sliding that occurs with the respiratory
cycle, the pleural line may move in
synchrony with cardiac pulsation.

22. Lung Sliding:-
 The absence of sliding lung may be
caused by pneumothorax, but it has
other causes as well.
 For example, apnea ablates sliding
lung.
- Selective main stem bronchial
intubation with blockage of the
contralateral main stem by the
endotracheal tube cuff.,
- As well as any other cause for main
stem occlusion (e.g. mucous plug,
tumor, blood clot, foreign body), will
cause loss of lung sliding on the side
of the blockage.
Parietal and visceral Pleura

23. A Lines:-
 Lung that is normally aerated has a
characteristic pattern of air artifact
designated as A lines. A-lines indicate
air, whether physiologic or pathologic.
 A lines are horizontally orientated
hyperechoic lines seen deep to the
pleural line.
 They represent reverberation artifacts
from ultrasound reflection between
the pleural surface and the outer
surface of the chest wall.
 Therefore, their depth is a
multiplicative of the distance between
the skin surface and the pleural line.

24. B Lines:-
 Lung that is edematous has a characteristic pattern of air artifact
designated as B lines. B lines are strictly defined as one or more mobile
hyperechoic vertically orientated lines that originate at the pleural
interface. They must efface A lines where the two intersect.
 They always extend in a ray-like
fashion to the bottom of the
viewing screen (does not
fades), and they generally
move synchronously with lung
sliding, and are absent in the
normal lung.

25. B Lines:-
 These artifacts result from the fluid-rich subpleural interlobular septae that, in a
pathologic condition defined as alveolar interstitial syndrome. Computed
tomographic correlations showed that B lines are related to the presence of
interstitial or interstitial-alveolar edema (ground glass or reticular pattern
abnormality), and are characteristic of lung edema.
 They may, however, be immobile in
the absence of pleural movement. B
lines are also lung rockets. B lines are
caused by ring-down artifact derived
from small subpleural fluid
collections or tissue densities. Their
presence excludes pneumothorax.

26. In contrast, comet tail artifacts
are fading away. Comet-tail
artifacts frequently occur in
patients with atelectasis due to
effusion or when the pleural line
is shredded due to inflammation,
fibrosis, or infiltration.
Numerous comet-tail artifacts originating near from the
diaphragmatic pleura. Given the existing pleural effusion,
the comet-tail artifacts are likely due to a partial collapse
of the lung and not an expression of an interstitial
pathology of the lung

27. CHAPTER – III
Parenchymal Pathology Ultrasonography

28. Pneumonia:-
 Pneumonia is characterized by
an irregular, serrated and
somewhat blurred margin.
 In early congestive stage of
pneumonia, the echo texture of
the consolidated lung is similar
to the liver.
 The criterion to determine the
echographic diagnosis of
pneumonia was the finding of
sub-pleural lung consolidation
with evidence of static or
dynamic air bronchograms.

29. Pneumonia:-
 Pleural line next to the lesion is
hypoechogenic and lung sliding
is reduced or absent.
 Branching echogenic structures
are often visible within the
consolidation representing air
bronchograms and can have an
intrinsic centrifuge movement
with breathing: this finding is
called dynamic air bronchogram
and rules out atelectasis.
 Air trapped in the small airway
creates multiple milli-metric
hyperechogenic spots within the
lesion .

31. The echographic appearance of pneumonia. It is an irregular subpleural
hypoechogenic area with air bronchograms (A, D) or many hyperechogenic spots (B,
C). Pleural line is often hypoechogenic .

32. Air -
Bronchogram:-
 The air- bronchogram is
located inside a
consolidation area and
consists of straight,
branching or variously
shaped hyperechoic blurred
margins.
 According to its status, it is
divided into static and
dynamic air bronchogram.

33. Air -Bronchogram:-
Static air bronchogram
• is usually produced in
• It is caused by entrapped air
inside an area of the lung that is
no longer aerated, thus
static artifacts.
• Static air bronchogram can be
revealed by the absence of
dynamic lung movement
respiration.
Dynamic air bronchogram
• is produced in ventilated areas of the lung and is caused by the presence of air inside bronchi, which then move according to the patient’s breathing.
• It is never produced in atelectasis but it can be seen in 60% of cases of infectious alveolar consolidation or in large pleural effusion with relaxation collapse with partial
reventilation during forced inspiration .

34.  Consolidation found with lung ultrasonography is strongly
correlated with its presence on chest CT.
 The finding of lung consolidation on ultrasonographic
examination does not imply any particular diagnosis.
Pneumonia may result in lung consolidation pattern, but lung
atelectasis of any cause, severe ARDS with dependent
distribution, or an infiltrative tumor (e.g. bronco alveolar
carcinoma) may all result in a consolidation pattern on
ultrasound.
Air -Bronchogram:-

35. The pleural criteria of pneumonia may be divided into:
 Pleural fragmentation,
 Localized pleural effusion,
 Basal pleural effusion.
Pleural fragmentation refers to the ‘pleural line’ corresponding
to the pneumonic lesion.
The line is characterized by its interrupted, thin, mostly
fragmented, and hypoechoic appearance when compared to
pleura covering non-infected lung areas.
Pleural Criteria of Pneumonia:-

37. To Summarize:
Sonographic findings in pneumonia:-
• Liver like in the early stage.
• Dynamic air -bronchogram.
• Blurred and serrated margins.
• Hypoechoic abscess formation.

38. Atelectasis:-
 Atelectasis is a relatively common condition in the ICU, and it is
characterized by the following signs;
(1) A change in the imaging location of the heart;
(2) Abolition of the diaphragm dynamic movement;
(3) Change in the imaging location of the diaphragm, which is
raised by at least 2 cm (in the supine position it corresponds with
the nipple).
(4) The presence of an attendant small pleural effusion of about
250 ml

39. Atelectasis:-
 A crucial problem in radiology is distinguishing between
obstructive atelectasis and passive atelectasis
caused by pleural effusion. Certain radiographic signs, such as
the Golden S sign, facilitate the diagnosis of obstructive
atelectasis caused by a central mass, but this finding is not
common. However, certain ultrasound findings can help
differentiate between these two types of atelectasis.

40. Atelectasis:-
 In passive atelectasis, sonography
demonstrates;
(1) Moderate pleural effusion ;
(2)Wedge shaped consolidation of
the lung parenchyma and
(3) Irregular borders when the lung
is aerated and partial reventilation
during inspiration or after
thoracocentesis.
 In obstructive atelectasis, the
ultrasound imaging demonstrates;
(1) Scant pleural effusion.
(2) Homogenous hypoechoic lung
consolidation.
(3) Focal lesions (caused by liquefaction
,the formation of micro or macro
abscesses, or metastasis)
(4) Static air bronchogram. The image
is similar to that of pneumonia but with
significantly less air bronchograms.

41. Compression atelectasis:
cap-like hypoechoic
transformation of lung
parenchyma.

42. Interstitial Syndrome “B-lines and their
diagnostic value”:-
A normal lung shows B-lines only in rare cases and less than three
B-lines in a single intercostal space when scanning perpendicular
to the direction of the ribs.
The correct scan was intercostal with the maximum extension of
the visible pleural line. The chest wall was divided into 8 areas,
and 1 scan for each area was obtained.
The areas were 2 anterior and 2 lateral per side. The anterior
chest wall was delineated from the sternum to the anterior axillary
line and was subdivided into upper and lower halves
(approximately from clavicle to the second-third intercostal spaces
and from the third space to diaphragm).

43. Interstitial Syndrome “B-lines and their
diagnostic value”:-
The lateral zone was delineated from the anterior to the
posterior axillary line and was subdivided into upper and
basal halves.
Therefore the sonographic technique ideally consists of
scanning eight regions, but a more rapid anterior two
region scan may be sufficient in some cases.
A positive region (positive scan) is defined by the presence
of three or more B-lines in a longitudinal plane between
two ribs. Such artifact may be distributed focally or
diffusely

44. The areas of thoracic ultrasonography considered in the study. Areas 1
and 2: upper anterior and lower anterior; areas 3 and 4: upper
lateral and basal lateral.
Each area was the same on right and left side. AAL, anterior axillary
line; PAL, posterior axillary line ..

45. Diffuse B
lines
Pulmonary
fibrosis
Non specific UIP
Pulmonary
edema
Alveolar
Cardiogenic
Non-
cardiogenic
Interstitial
Focal B lines

46. I) Diffusely
Arranged
B-Lines:-
The diagnosis of the
diffuse interstitial
syndrome is based
on
3 basic steps
(1) Recognition of B lines, appearing on the screen as laser-like
vertical echogenic artifacts arising from the pleural line,
spreading up without fading to the edge of the screen and
moving synchronous with lung sliding
2) Diagnosis of a positive single scan:- when B lines are
multiple (at least three) and close (no more than 7 mm
apart). Multiple B lines but far from each other is not
significant and
3) Diagnosis of a positive examination: - defined as at least two
positive scans per side. Isolated positive scans identify the focal
interstitial syndrome, which has a different meaning and can be
visualized in the area surrounding alveolar consolidations or
in normal lungs.

47. I) Diffusely Arranged B-Lines:-
Diagnostic Criteria of diffuse parenchymatous lung disease ;
(1) A thickened pleural line;
(2) An irregular, fragmented pleural line .
(3) Subpleural alterations.
Diffuse B-lines is further classified according to the
presence or absence of the following criteria into:
pulmonary edema (alveolar & interstitial)
which not fulfilling the criteria
pulmonary fibrosis (non specific
intestinal pneumonia & UIP) which
fulfilling the criteria.

48. I) Diffusely Arranged B-Lines:-
The pattern of diffuse B-lines in lung
parenchyma with the previous criteria and
less than 3 mm apart is suggestive
of non specific intestinal pneumonia
(Ground Glass).
However if more than 7 mm apart will be suggestive
for UIP (Honey Combing).
The pattern of diffuse B-lines in lung
parenchyma without the previous criteria
and less than 3 mm apart is suggestive
for pulmonary edema either cardiogenic or
non cardiogenic.
However if more than 7 mm apart will be
suggestive
for interstitial pulmonary edema.

49. To differentiate cardiogenic from non cardiogenic
pulmonary edema
Cardiogenic pulmonary edema
(1) Diffuse B-Lines spread over all lung fields
without spared areas;
(2) No Peripheral areas of consolidation;
(3) No Absence or reduction of lung gliding,
(4) Pleural effusion more pronounced and
Criteria of ARDS pattern
(1) Diffuse B-Lines spread over all lung fields with
spared areas;
(2) Peripheral consolidation;
(3) Absent or reduced lung gliding;
(4) Pleural effusion less pronounced

50. Pulm edema

51. Examination with a linear scanner shows an
irregular, fragmented, and thickened pleural line
with numerous B-Line artifacts .

52. idiopathic pulmonary fibrosis shows an irregular
pleural line and an irregularly bordered, hypoechoic
subpleural alteration .

53. Idiopathic pulmonary
fibrosis (Left panel)
diffuse presence of B
lines at lung
ultrasound, together
with thickened and
irregular pleural line.
(Right panel)
Corresponding high-
resolution CT
showing bilateral
thickened interlobular
septa reaching the
whole surface of the
lung, with some right-
sided and peripheral
honeycomb patterns.

54. Diffuse interstitial
pneumonia. (Left panel)
Lung ultrasound pattern
of diffuse AIS. (Right
panel)
Corresponding high-
resolution CT showing
multiple interstitial
reticular thickening,
some ground-glass
areas, and bilateral
pleural effusion

55. Interstitial Fibrosis

56. (II) Focally arranged B-
Line:-
B-lines focally occur in
cases of focal interstitial
syndromes like
pneumonia, pneumonitis,
atelectasis, pulmonary
contusion, infarction, pleural
disease or neoplasia .