Física básica del ultrasonido

DEPARTAMENTO DE VENTAS


DEFINICIONES

HISTORIA

TRANSDUCTORES

MODOS DE IMAGEN

MODO A

MODO M

MODO B

MODO DOPPLER

MODO CW

MODO PW

MODO COLOR

POWER DOPPLER

MODO POWER DIRECCIONAL

IMAGEN PANORAMICA

3D/4D


CONCEPTOS BÁSICOS DEL SONIDO


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

http://www.monografias.com/trabajos12/moviunid/moviunid.shtml


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


Infrasound Audible Sound Ultrasound 20Hz 20kHz

For medical diagnostic imaging

1MHz 20MHz

Low High

FRECUENCIAS


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 DEPARTAMENTO DE VENTAS

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

Function: to display tissue structure

B mode is also called 2D mode.

1950s DEPARTAMENTO DE VENTAS

Convex Probe

Linear Convex

Phased array probe Linear probe



DESCRIPCION DE CADA UNO DE ELLOS

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


θ

v

f f + fD c

cos2D

vff

fD: Doppler shift of the frequency

f: Transmitted frequency

v: Velocity of the blood

θ: Angle of incidence between the

ultrasound beam and the direction of the

flow

c: speed of sound in tissue


Color Doppler:

1. Color: Color Doppler

2. Power: Power Doppler:

3. Directional Power Doppler

Spectral Doppler:

1. CW: continuous wave Doppler

2. PW: Pulse wave Doppler

Color Doppler

Spectral Doppler


Color Doppler: Pixels assigned color based on mean velocity

Function: to display direction of blood flow

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

Red towards probe Blue away from probe

1983 DEPARTAMENTO DE VENTAS

Power Doppler: Pixels assigned color based on mean power

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

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



Gray Scale Velocity Variance Power Directional Power

B mode Color mode Power mode

B mode - colorized Color mode

Whole image is colorized. Only blood flow is colorized. Tissue is monochrome.


Sensitivity

Direction

Velocity

Angle dependent

Application

Yes

Yes

Yes

Normal velocity

No

No

No

Low velocity

Normal High

Color Power

Yes

No

No

Low velocity

High

DirPower

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


Color mode

vertical oblique

Power mode

Angle Dependent Yes No

At perpendicular angle No flow displayed Displayed normally


Some elements are transmitting sound waves.

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

But there is a sensitive region.

The others are receiving.

There is NO Sample Volume.



Sensitive Region

Angle Correction

Sample Line

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

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

Time

Velocity


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 Frequency Transmit Receive Transmit Receive …



Sample Volume

Angle Correction

Sample Line

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

PW: Pulse-Wave Doppler

Function: to measure velocity of blood flow

Time

Velocity



Principle

Probe

Velocity

Locate

Window

Application

All elements are transmitting and receiving sound waves.

All

Low

Sample volume

Yes

All

Phased array, pencil, other

High

Sample line

No

Cardiology

Pulsed-wave Continuous wave

PW mode CW mode

Some elements are transmitting sound waves. The others are receiving.

Sample Volume

Angle Correction

Sample Line

Sensitive Region

Angle Correction

Sample Line

Principle

Y-axial

Object

Locate

Application

Velocity (cm/s, m/s) frequency shift (kHz)

Hemodynamics

Sample volume

Cardiology, vascular

Depth (cm, mm)

Tissue motion

Sample line

Cardiology

Doppler Pulse-echo

PW mode M mode


Conventional M mode

Anatomical M mode

Along sound beam


Fan

Linear



Network

Imaging System 1

Imaging System 2

Imaging System 3

Reception

DICOM PrinterDoctor

DICOM Server

Diagnostic Center

Verification

Storage Worklist

Print

Física básica del ultrasonido

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