sauter - ultrasoundppt

7/29/2019 Sauter - Ultrasoundppt

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A. R. SauterRikshospitalet University Hospital

Ultrasound -

Theoretical and practical background

SOundNavigation And Ranging

Ultrasound image generation anddevice operations

Technical principles

20Hz 20kHz 200MHz

Infra-sound Ultrasound

Audiblesound

1-17MHzMedica

ultrasound

+ -electrical energy

electrical energy

Piezoelectric effect

Velocity (depending on the density):

Impedance:product of density and velocity

air 330 m/s

water 1450 m/s

fat 1450 1462-1473 m/s

muscle 1580 m/s

bone 4080 m/s

Technical principles

Sauter 2010 - Ultrasound


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Differences in impedance (interface)give reflections

Strong differences in impedancegive strong reflections

hyperechoic

Small differences in impedance givetransmission of the US beamhypoechoic

Technical principlesAcoustic coupling medium

Transducers Transducers

! Frequeny

" Frequeny

! Resolution

" Resolution

" Penetration

! Penetration

Transducers

Axial resolution

Lateral resolution

Spatial resolution

Resolution

Axial resolution



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Lateral resolution TGC - Time Gain Compensation

AT

TENUATION

Reflection

Scatter

Refraction

Absorption

ENERGY

DISTANCE

TGC - Time Gain Compensation

ENERGY

DISTANCE

ATTEN

UATION

Amplified signal



Near

Far

Overall

Time gain control

Focus and Depth

Sites 2008



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Doppler sonography Doppler sonography

increased frequency

decreased frequency

Practical aspects

Ultrasound imaging

pressure

alignment

rotation

tilting



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Ultrasound imaging

Short axis Long axis

Ultrasound imaging

In-plane Out-of-plane

In-plane needle insertion

Out-of-plane needle insertion

short axis / in-plane

short axis / out-of-plane

long axis / in-plane

long axis / out-of-plane

Ultrasound imaging



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Ultrasound imaging

Visualization of nerves:

Visualization of nerves:-honeycomb structure- hypoechoic or anechoic

Bigeleisen 2006

Ultrasound imaging

Visualization of local anesthetics:

Pitfalls and artifacts



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Characterizing novice behavior associated with learningultrasound-guided peripheral regional anesthesia.Sites BD, Spence BC, Gallagher JD, Wiley CW, Bertrand ML, Blike GT.Reg Anesth Pain Med 2007;32:107-15.

Video documentation of USG nerve blocksperformed by 6 anesthesia residents

398 committed errors in 520 blocks

Characterizing novice behavior associated with learningultrasound-guided peripheral regional anesthesia.Sites BD, Spence BC, Gallagher JD, Wiley CW, Bertrand ML, Blike GT.Reg Anesth Pain Med 2007;32:107-15.

1) failure to recognize the maldistributionof localanesthesia

2) failure to recognize the location of the needletip before injection

3) fatigue

4) failure to correctly correlate the sidedness of the

patient with the sidedness of the ultrasoundimage

5) poor choice of needle-insertion site and angle with

respect to the probe preventing accurateneedlevisualization.

Intravascular needle placement Intraneural needle placement

Pneumothorax

Koscielniak-Nielsen 2008

Ultrasound-guided PNB



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