Basics of Chest Sonography and Anatomy of Chest Wall

Basics of Chest Sonography

and Anatomy of Chest Wall

By

Gamal Rabie Agmy , MD , FCCP

Professor of Chest Diseases ,Assiut

University

• U/S probes emit and

receive the energy as

waves to form pictures

Ultrasound Transducer

Speaker

transmits sound pulses

Microphone

receives echoes

• Acts as both speaker & microphone Emits very short sound pulse

Listens a very long time for returning echoes

• Can only do one at a time

• Diagnostic ultrasonography

is the only clinical imaging

technology currently in use

that does not depend on

electromagnetic radiation.

• Immediate bedside availability

• Immediate bedside repeatability

• Rapid goal directed application

• Cost saving

• Reduction in radiation exposure

Advantages of Transthoracic

Ultrasonography

Physical Principles

Cycle • 1 Cycle = 1 repetitive periodic oscillation

Cycle

Frequency

• # of cycles per second

• Measured in Hertz (Hz)

-Human Hearing 20 - 20,000 Hz

-Ultrasound > 20,000 Hz

-Diagnostic Ultrasound 2.5 to 10

MHz

(this is what we use!)

frequency 1 cycle in 1 second = 1Hz

1 second

= 1 Hertz

High Frequency

• High frequency (5-10 MHz)

greater resolution

less penetration

• Shallow structures

Low Frequency

• Low frequency (2-3.5 MHz)

greater penetration

less resolution

• Deep structures

Probes

Wavelength

• The length of one complete cycle

• A measurable distance

Wavelength

Wavelength

Amplitude

• The degree of variance from the normal

Amplitude

The Machine

Ultrasound scanners

• Anatomy of a scanner:

– Transmitter

– Transducer

– Receiver

– Processor

– Display

– Storage

Changing the TGC

Changing the Gain

Displays

• B-mode

– Real time gray scale, 2D

– Flip book- 15-60 images per second

• M-mode

– Echo amplitude and position of moving

targets

– Valves, vessels, chambers

“B” Mode

“M” Mode

A common language: Color Coding

Black Grey White

Image properties

• Echogenicity- amount of energy reflected back from tissue interface

– Hyperechoic - greatest intensity - white

– Anechoic - no signal - black

– Hypoechoic – Intermediate - shades of gray

Hyperechoic

Hypoechoic

Anechoic

Ultrasound Artifacts

• Can be falsely interpreted as real

pathology

• May obscure pathology

• Important to understand and appreciate

Ultrasound Artifacts

• Acoustic enhancement

• Acoustic shadowing

• Lateral cystic shadowing (edge artifact)

• Wide beam artifact

• Side lobe artifact

• Reverberation artifact

• Gain artifact

• Contact artifact

Acoustic Enhancement

• Opposite of acoustic shadowing

• Better ultrasound transmission allows

enhancement of the ultrasound signal

distal to that region

Acoustic Enhancement

Acoustic Shadowing

• Occurs distal to any highly reflective or

highly attenuating surface

• Important diagnostic clue seen in a

large number of medical conditions

– Biliary stones

– Renal stones

– Tissue calcifications

Acoustic Shadowing

• Shadow may be more prominent than

the object causing it

• Failure to visualize the source of a

shadow is usually caused by the object

being outside the plane of the

ultrasound beam

Acoustic Shadowing

Acoustic Shadowing

Lateral Cystic Shadowing

• A type of refraction artifact

• Can be falsely interpreted as an

acoustic shadow (similar to gallstone)

X

Lateral Cystic Shadowing

Beam-Width Artifact

• Gas bubbles in the duodenum can

simulate a gall stone

• Does not assume a dependent posture

• Do not conform precisely to the walls of

the gallbladder

Beam-Width Artifact

Beam-width artifact Gas in the duodenum simulating stones

Side Lobe Artifact

• More than one ultrasound beam is

generated at the transducer head

• The beams other than the central axis

beam are referred to as side lobes

• Side lobes are of low intensity

Side Lobe Artifact

• Occasionally cause

artifacts

• The artifact by be

obviated by

alternating the angle

of the transducer

head

Side Lobe Artifact

Reverberation Artifacts

• Several types

• Caused by the echo bouncing back and

forth between two or more highly

reflective surfaces

Reverberation Artifacts

• On the monitor parallel bands of

reverberation echoes are seen

• This causes a “comet-tail” pattern

• Common reflective layers

– Abdominal wall

– Foreign bodies

– Gas

Reverberation Artifacts

Reverberation Artifacts

Gain Artifact

Contact artifact

• Caused by poor probe-

patient interface

Mirror Artifact

Traditionally, air has been considered the

enemy of ultrasound and the lung has been

considered an organ not amenable to

ultrasonographic examination. Visualizing the

lung is essential to treating patients who are

critically ill.

Lines written on ultrasound in the five

Light‟s editions

43

78

102

122

278

1983 1990 1995 2001 2008

1998 -2008

2009

2010

V SCAN

Probes

A high-resolution linear transducer of 5–10 MHz is suitable for imaging the thorax wall and the parietal pleura (Mathis 2004). More recently introduced probes of 10–13 MHz are excellent for evaluating lymph nodes (Gritzmann 2005), pleura and the surface of the lung.

For investigation of the lung a convex or sector probe

of 3–5 MHz provides adequate depth of penetration.

Transthoracic Sonography

Lungs –normal static findings

Normal lung considered “invisible” to

ultrasonographer

Artefactscan be used to infer normality or

abnormality

A lines

horizontal reverberation artifacts from pleural

line

the only finding in 2/3 of normal lung US

B lines

vertical narrow bands from pleural line to edge

of screen

obliterate the A linme

Multiple B lines = Ultrasound Lung Rockets =

Abnormal lung has characteristics that are

clinically useful

Lungs –normal dynamic findings

Pleural sliding (lung sliding sign)

Pleural line “shimmers” with respiration

Presence of lung sliding rules out pneumothorax

Lung sliding greatest in lower thorax (greatest

expansion)

Absence of lung sliding has a number of causes

Pneumothorax

Apnoea

Pleural adhesions

Mainstembronchial intubation or occlusion

Critical parenchymal lung disease e.g. ARDS,

contusion

Scanning Positions for Chest Sonography

Focused exam – 8 views

Sagittal or coronal views

RIB SHADOWS confirm position and guide you to pleura.

The Regions

1 2

3

4

Volpicelli et al, Am J Emerg Med 2006; 24: 689-696

Region 2 is usually above the nipple

THE BAT VIEW

Chest wall

Pleural line

Rock the probe slightly side to side

until the pleura is in sharp focus

Pleura not at right angles

to probe so indistinct

Correct angle =

sharpest edge.

Interpretation

Normal lung surface

Left panel: Pleural line and A line (real-time). The pleural line is located 0.5 cm below the rib line in the adult. Its visible length between two ribs in the longitudinal scan is approximately 2 cm. The upper rib, pleural line, and lower rib (vertical arrows) outline a characteristic pattern called the bat sign.

A lines = default normal

Horizontal echo reflection at exact

multiples of intervals

from surface to bright reflector.

Dry lung OR PNTX

Decay with depth

Obliterated by B

pleura A

A

A

A

A

A

B lines = fluid in alveolus or

interstitium

Originates from pleural line

Reaches base of

screen OR ALMOST

MORE THAN 2 at once is abnormal

EXCEPT in lung base

Remember as

„Kerley Bs‟

Not exactly the

same.

RIB RIB

B B B B B

B Lines = Crackles

Confluent B lines = Bad Bad

„White‟ or „shining‟ lung

Means increased

severity

Probably indicates thicker fluid in alveoli

eg protein or

inflammatory cells

% space / 10

B x 3 x 2 x 2 = CCF

Makes assumption that „globally‟ wet

lungs are most likely to be CCF

12

the "seashore sign" (Fig.3).

Normal Anatomy

Normal lung surface

Left panel: Pleural line and A line (real-time). The pleural line is located 0.5 cm below the rib line in the adult. Its visible length between two ribs in the longitudinal scan is approximately 2 cm. The upper rib, pleural line, and lower rib (vertical arrows) outline a characteristic pattern called the bat sign.

Normal Chest Ultrasound

Superficial tissues

ribs

Poste

rior a

coustic

shadow

ing

Impure

acoustic

shadow

ing

Pleural line

Muscle

Fat

Pleura

Lung

HEPATISATION VS COLLAPSE

SOLID, NO CHANGE WITH

RESPIRATION COLLAPSE – CONCAVE EDGES, CHANGE WITH RESPIRATION

the "seashore sign" (Fig.3).

Duplex Doppler sonogram of a 5 x 3 cm hypoechoic mass

(adenocarcinoma) in upper lobe of left lung shows blood flow

at margin of tumor near pleura. Spectral waveform reveals

arteriovenous shunting: low-impedance flow with high

systolic and diastolic velocities. Pulsatility index = 0.90,

resistive index = 0.51, peak systolic velocity = 0.47 m/sec, end

diastolic velocity =0.23 m/sec, peak frequency shift = 3.8 kHz,

Duplex Doppler sonogram in 67-year-old man with pulmonary

tuberculosis in lower lobe of left lung shows several blue and

red flow signals in massiike lesion. Spectral waveform reveals

high-impedance flow. Pulsetility index = 4.20, resistive index =

0.93, peak systolic velocity = 0.45 m/sec, end diastolic

velocity = 0.03 m/sec, Doppler angle = 21#{

Alveolar-interstitial

syndrome

Duplex Doppler sonogram of a 5 x 3 cm hypoechoic mass

(adenocarcinoma) in upper lobe of left lung shows blood flow

at margin of tumor near pleura. Spectral waveform reveals

arteriovenous shunting: low-impedance flow with high

systolic and diastolic velocities. Pulsatility index = 0.90,

resistive index = 0.51, peak systolic velocity = 0.47 m/sec, end

diastolic velocity =0.23 m/sec, peak frequency shift = 3.8 kHz,

Duplex Doppler sonogram in 67-year-old man with pulmonary

tuberculosis in lower lobe of left lung shows several blue and

red flow signals in massiike lesion. Spectral waveform reveals

high-impedance flow. Pulsetility index = 4.20, resistive index =

0.93, peak systolic velocity = 0.45 m/sec, end diastolic

velocity = 0.03 m/sec, Doppler angle = 21#{

(Chest. 2008; 133:836-837)

© 2008 American College of Chest

Physicians

Ultrasound: The Pulmonologist’s New

Best Friend

Momen M. Wahidi, MD, FCCP

Durham, NC

Director, Interventional Pulmonology, Duke

University Medical Center, Box 3683,

Durham, NC 27710