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Define bandwith.

The range of frequencies contained within a pulse

What is better Narrow or broad bandwidth?

Broad due to the larger spectrum of frequencies

What is the main pulse that is emitted from the transducer termed?

Operating/Resonance

What is the process that increases the range of frequencies called?

Damping

Define Velocity.

Speed with direction of motion specified

What is velocity determined by?

Density and stiffness

What is the formula for propagation speed?

C=wavelength X Freq

What 2 variables determine the mediums properties?

Stiffness-resistance of a material to compression, and Density-concentration of mass per unit of volume

What is the rule of thumb regarding propagation speed?

Prop speed increase=Stiffness increase=Density decrease

What are the ranges for PRF?

1000-10,000Hz

Define PRF.

Number of electrical pulses per second

What is the typical range for pulse duration?

.5-3 microseconds

What are the units for duty factor and pulsed ultrasound?

Unitless

What happens to duty factor when PRP increases?

DF decreases

What happens to duty factor when Imaging depth increases?

DF decreases

What happens to duty factor when Pulse duration increases?

DF increases

What happens to duty factor when PRF increases?

DF increases

What are the 2 types of detail resolution?

Axial and Lateral

Define Axial resolution.

The minimum reflector separation necessary to resolve reflectors ALONG a scan line

Define Lateral resolution.

The minimum reflector separation necessary to resolve reflectors ACROSS a scan line

What are the 3 modes of focusing for a mechanical transducer?

Lens, Curved element, Mirrors

Define wavelength.

The length of space over which one cycle occurs

What is the formula for wavelength?

wavelenght=c/f

What 2 things determine a wavelength?

Frequency and propagation speed

What does wavelength influence?

Axial/longitudinal resolution

If frequencyy is doubled what happens to the wavelength?

It is halved

What are the effects of ultrasound on tissue termed?

Bioeffects

What are the 2 types of bioeffects to mammalian tissue?

Heating and Mechanical

What are the units for wavelength?

mm

The level at which signals are not transmitted through an ultrasound receiver is termed what?

Rejection

How long is the typical pulsed duration?

.5-3 microseconds

What is spacial pulse length analogus to?

wavelength

Define beam steering.

Movement of the transducer over the area of interest

What does lateral resolution equal?

Beam diameter

Axial resolution = what?

spl/2

Is the following operator adjustable: compensation and rejection?

Yes

Is the following operator adjustable: amplification and compensation?

yes

Is the following operator adjustable: demodulation and compression

no

Is the following operator adjustable: rejection and amplification?

yes

Define pixel.

Unit which imaging information is divided for storage and display in a digital instrument

Define dead zone.

Distance between the transducer face and the 1st rod, no image, area very close to the transducer

Define M mode.

B mode presentation of changing reflector position, time, motion, and amplitude

Define B mode

Information displayed as brightness

Define matching layer.

Material attached to the front of a transducer to reduce the reflections at the transducer element

Define damping material.

Material attached to the rear of the transducer to reduce the pulse duration

Define Q factor.

Recriprical of fractional bandwidth

Define Linear array.

Array made of rectangular elements arranged in a line

Define Sequential array.

Array of elements which are activated one at a time

Define Annular array.

Array of crystals arragned in a circular symmetry.

What is the equation for: Prop speed?

C=1540m/s

What is the equation for: Intensity formula?

I(mw/cm2)=P(mw)/A(cm2)

What is the equation for: spatial pulse length?

spl=number of cycles X wavelength

What is the equation for: Impedance formula?

Z(rayls)=density X prop speed

What is the equation for: Wavelength?

Wavelength=prop.speed / frequency

What is the equation for: Pulse Duration?

pd=number of cycles X period

Define: Grating lobes?

Additional, weaker beams of sound traveling in directions different from the primary beam

Define: Slice thickness.

Also called sectional thickness, Echoes from adjacent tissues filling what should be anechoic

Define: refraction.

Change of sound direction on passing from one medium to another

What is a type of imaging that relates to the height of the vertical defection?

A-mode

What is a type of imaging that relates to time and motion?

M-mode

What is a type of imaging that relates to the brightness of the returning echo?

B-mode

Define duty factor?

The fraction of time the pulsed ultrasound is on

What is the typical duty factor in pulsed echo?

.1-1.0

What is the typical duty factor in continuous wave?

100%

Define: Attenuation.

Reductin of power or intensity as sound travels through a medium

What are the units of attenuation?

dB/cm/MHz

What is attenuation coefficient?

The attenuation that occurs with each cm the sound wave travels

What is reduced with attenuation?

Power and intensity

Describe the piezoelectric effect?

When electricity is applied the PZT elements converts the electricity into ultrasound pulses

What is the typical man made crystal used in most transducers today?

Lead Zirconat Titante (PZT)

What is the frequency for ultrasound?

> 20,000Hz Greater than audible range

What is infrasound?

<20Hz Less than the audible range

What are the frequencies of audbile sound?

20Hz-20,000Hz

What is sound?

A mechanical longitudinal wave

What is sound made up of?

Compressions and rarerefractions

What are the 3 mechanisms of action for ultrasonid bioeffects?

Heat-Intensity, Radiation force-Exposure time, and Cavitation-mechanical effect to tissue

What type of intensity does heating depend on?

SPTP- Spatial peak Temporal peak

If frequency decreases what happens to the SPL?

It increases

What 2 factors would increase ine intensity of a sound beam?

Increase power, Decrease focusing

What is Q factor?

The recriprical of fractional power

What is optimal Q factor?

Low

Qvalue equals what?

Material prop speed X thickness of the element

WHat factor is the operating crystal dependant on?

Thickness of the element and the mediums prop speed

How long is the round trip time for each cm of distance traveled in soft tissue?

13 microseconds

Define: Huygen's principle.

Each surface of multiple transducer, diffract producing small waves that join together and form one main energy sound beam

Define: Rayleigh's principle.

Scattering caused by RBC

Refraction can only occur if you have what 2 factors?

Oblique incidence, and Different prop speeds

Define: Period.

Time per cycle

Define: PRP.

Time from the beginning of one pulse to the next

Define: PRF.

Number of pulses per second

What are the units for: Period

(ms)

What are the units for: PRP

(ms)

What are the units for: PRF

(KHz)

Why do we use coupling gel?

To provide a good sound path from the transducer to the skin, eliminating the thin layer of air that would reflect the sound

What type of format, beam steering, and beam focusing does the following have: Linear Array.

Rectangular image, Electronic focusing, Mechanical steering

What type of format, beam steering, and beam focusing does the following have: Curved Array.

Convex image, Electronic focusing, Mechanical steering

What type of format, beam steering, and beam focusing does the following have: Phased array.

Sector image, Electronic focusing and steering

What type of format, beam steering, and beam focusing does the following have: Annular array.

Sector image, Mechanical steering, Electronic focusing

What type of format, beam steering, and beam focusing does the following have: Single element.

Pie shape image, Mechanical focusing and steering; Lens mirror

All of the following may be used as units of amplitude except which: Millimeters, Degrees, Pascals, meters per second

m/s

How are the spatial pulse length and the number of cycles in the pulse related?

Directly related

What 2 conditions are necessary for refraction to occur at a boundary between two media?

Different prop speeds and oblique incidence

When red blood cells move away from a transducer, the frequency of the wave returned from the RBC is what?

Less than the emitted frequency

What are the units of impedance?

Rayls

What best describes an angle with a measurement of 133degrees?

Obtuse

The sonographer increases the depth. Which parameter is decreased?

PRF

What is enhancement caused by?

Weakly attenuating structures

Which of the following parameters is determined by the medium: Wavelength, Freq, Period?

Wavelength and Spatial pulse length depend on the sound source and medium

Which of the following contributes most to total attenuation in soft tissue: Absorption, Reflection, Scattering?

Absorption

What are the units of the transmitted intensity of a sound wave?

W/cm2

Which of the following statements is true regarding axial resolution artifiacts: Higher quality images are associated with higher numbers, Axial resolution is reported in units of cm3, Numerically axial resolution equals 1/4 the pulse length, or Too few reflectors appear on the image?

Too few reflectors appear on the image

Which of the following is considered an acoustic variable: Freq, Period, Power, or Pressure?

Pressure

What are the effects of medium upon the ultrasound wave called?

Acoustic propagation properties

What is the acoustic velocity in soft tissue?

1540m/s

What is the power intensity for the following: 0dB, -3dB, -6dB, -9dB?

0=100%, -3=1/2, -6=1/4, -9=1/8

What 3 factors contribute to attenuation?

Absorption, Scattering, and Reflection

What is the formula for impedance?

Density X Prop Speed

What is impedance important in?

Reflection at boundries

What are the general frequencies used in ultrasound imaging and name a type of exam used for the transducers.

2.0-Cardiac, 3.5-OB/Abdominal, 5.0-Vascular, 7.5-Superficial, 10.0-Small parts

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