basics of chest sonography and anatomy of chest wall
TRANSCRIPT
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