Física básica del ultrasonido

 DEFINICIONES  MODO PW
 HISTORIA  MODO COLOR
 TRANSDUCTORES  POWER DOPPLER
 MODOS DE IMAGEN  MODO POWER
 MODO A DIRECCIONAL
 MODO M  IMAGEN
 MODO B PANORAMICA
 MODO DOPPLER  3D/4D
 MODO CW

DEPARTAMENTO DE VENTAS

CONCEPTOS BÁSICOS DEL
SONIDO


 Sonido es una onda
mecánica
longitudinal que se
propaga a través de
un medio elástico.


Compresión: Región de alta presión.

Rarefacción: Zonas de baja presión.

Las compresiones y rarefacciones se
alternan a través del medio en la
misma forma que las partículas de aire
individuales oscilan de un lado a otro
en la dirección de la propagación de la
onda.


 AMPLITUD: Es el valor máximo
del movimiento de una onda.

 PERIODO: Tiempo que se tarda
en realizar un ciclo completo. Se
mide en segundos (s).

 FRECUENCIA: Es el número de
ciclos que se realizan en un
segundo. Es, por tanto, la
inversa del período:
f=1/T
Se mide en ciclos por
segundo (cps), que se
denomina normalmente
hercios (Hz).


 LONGITUD DE ONDA: La
distancia que recorre una
onda sonora en el tiempo
de un período es lo que se
llama longitud de onda (λ).

 VELOCIDAD DEL SONIDO:
Es la velocidad con que
se desplazan las ondas
sonoras. Su dirección
es perpendicular a la
superficie vibrante bajo
forma de ondas.
Velocidad = Distancia recorrida / tiempo

c=λ*f


Medium Velocity (m/s) Medium Velocity (m/s)

Air 330 Liver 1549

Water 1480 Kidney 1561

Fat 1450 Muscle 1585


 FRECUENCIAS
20Hz 20kHz
Infrasound Audible Sound Ultrasound
Low High

For medical diagnostic imaging
1MHz 20MHz


Piezoelectricity crystal


1910s Ultrasound sonar theory was developed in France
1942 A mode was invented in Austria for brain scanning

1950s M mode was invented
USA invented B mode in clinical application
1956 CW mode was invented in Japan for heart valve
application
1959 PW mode was invented

1983 Color Doppler mode was invented in Japan

1990 Kretz, an Austria company made the first commercial 3D
ultrasound scanner


1910s


DESCRIPCION DE CADA UNO
DE ELLOS


 A=AMPLITUD

SOLO SE REGISTRA LA
INTENSIDAD DE LA SEÑAL DEL
ECO.


M: Motion
displayed over time

Time

Depth

Function: to display tissue motion 1950s

B: Brightness
• displayed as dots
on screen
• stronger signal,
brighter dot

B mode is also
called 2D mode.

Function: to display tissue structure 1950s

Convex Linear

Convex Probe Linear probe Phased array probe


 Austria
 Physicist and
mathematician
 Born in 1803 in Salzburg
 Found Doppler Principle
in 1842
 Died in 1853 in Venice


Sound source: NOT moving Sound source: moving


Blood cell NOT moving Blood cell moving forward/backward


2  f  v  cos 
fD 
f + fD c
fD: Doppler shift of the frequency
θ f: Transmitted frequency
v: Velocity of the blood
θ: Angle of incidence between the
v ultrasound beam and the direction of the
flow
c: speed of sound in tissue


Color Doppler: Color Doppler
1. Color: Color Doppler
2. Power: Power Doppler:
3. Directional Power Doppler
Spectral Doppler
Spectral Doppler:
1. CW: continuous wave Doppler
2. PW: Pulse wave Doppler


Color Doppler:
Pixels assigned color
based on mean
velocity

Red towards probe
Blue away from probe

Color mode is also
called CDFI mode
(Color Doppler Flow
Imaging) or CFM (color
flow mapping)

Function: to display direction of blood flow 1983

Power Doppler:
Pixels assigned color
based on mean
power

Power mode is
also called CPA
mode. (Color
Power Angio)

Function: to display volume of blood flow, especially at low velocity

B mode Color mode Power mode

Gray Scale Velocity Variance Power Directional
Power


B mode - colorized Color mode
Whole image is colorized. Only blood flow is colorized.
Tissue is monochrome.

Color Power DirPower
Direction Yes No Yes

Angle Yes No No
dependent
Velocity Yes No No

Sensitivity Normal High High

Application Normal velocity Low velocity Low velocity

Power Doppler displays amplitude of signal (how much)
Color Doppler displays velocity (how fast)


Color mode Power mode

vertical oblique

Angle Dependent Yes No

At perpendicular angle No flow displayed Displayed normally


Some elements are
transmitting sound waves.

The others are receiving.

The transmitting and
receiving of sound waves
are JUST in the same time.

There is NO Sample Volume.
But there is a sensitive
region.


Sample Line

Sensitive Region

Angle Correction

Gray scale stands for:
the amount of all objects
in that velocity
along the sample line.


CW: Continuous-Wave
Doppler
speed of blood cells
displayed on a
time/velocity graph

Time

Velocity

Function: to measure velocity of blood flow, especially in heart 1956

Elements are both
transmitting and receiving
sound waves.

The transmitting and
receiving of sound waves
are NOT in the same time.

There is a Sample Volume.

PRF: Pulse Repetition
Transmit Receive Transmit Receive … Frequency


Sample Line

Sample Volume

Angle Correction

Gray scale stands for:
the amount of all objects
in that velocity
in the sample volume.

PW: Pulse-Wave
Doppler

Velocity

Time

Function: to measure velocity of blood flow 1959

Sample Line
PW mode CW mode Sample Line

Principle Pulsed-wave Continuous wave

All elements are Some elements are
transmitting and receiving transmitting sound waves.
Sensitive Region
Sample Volume
sound waves. The others are receiving.
Angle Correction Angle Correction
Probe All Phased array, pencil, other

Velocity Low High

Locate Sample volume Sample line

Window Yes No

Application All Cardiology


PW mode M mode
Principle Doppler Pulse-echo

Y-axial Velocity (cm/s, m/s) Depth (cm, mm)
frequency shift (kHz)

Object Hemodynamics Tissue motion

Locate Sample volume Sample line

Application Cardiology, vascular Cardiology


Anatomical M mode

Along sound beam

Conventional M mode


Linear

Fan

1990

Diagnostic Center

Verification Doctor DICOM Printer Print

Network

Reception DICOM Server

Imaging System 1 Imaging System 3
Storage Worklist
Imaging System 2


Física básica del ultrasonido

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