Physics Flashcards by Heather Sholey

propagation

movement of the soundwave

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bioeffects

Any damage to the human tissue or cell

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digital scan converter

a device that stores computer data and convert it to an image on the ultrasound monitor

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transducer

an instrument that converts one form of energy into another

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unit of frequency

Hertz (Hz)

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unit of pressure

Mm/mg, pascals

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unit of temperature

Celcius, Kelvin, Farenheit

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longitudinal wave

particles of the medium move in the same direction. An example is sound.

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amplitude mode

displayed the amplitude of the sound wave, no longer used

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motion (M) mode

used to measure fetal heart rates

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medium

what sound waves must have to travel

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ALARA

The method of scanning used that includes shortened exam times, low power settings on the ultrasound machine, and limited use of color Doppler and spectral Doppler. Reduces bioeffects for our patients.

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HIFU

a type of ultrasound used for destruction of cancerous tumors within certain organs

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PZT

a man made substance that is used for the crystals in the transducer.

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attenuation

a weakening of the sound wave as it passes through the body, usually in the form of heat.

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Dual image refers to

allows the display screen to be split in two for easy comparison of the image

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output power:

can be changed by the sonographer

determined by the Pulser voltage

as the output power increases, the noise decreases, increasing the signal-to-noise ratio

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temporal resolution is most important in what clinical setting?

fetal echo (heart) - moving structures

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annotation refers to:

labeling of the image as to organ, probe orientation, patient position

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List 5 components of a transducer and their function:

1) matching layer-increases the efficiency of sound energy between the body and the PZT
2) PZT-crystals that produce the soundwaves
3) case-holds all components, protects the components
4) wire-provides power to the crystals, one wire for each crystal
5) damping layer-stops the vibrations, decreases noise for a better picture

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Order of the functions of the receiver

Amplification

Compensation

Compression

Demodulation

Reject

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What is Hertz (Hz)?

the standard unit of frequency

equal to one cycle per second

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Diagnostic ultrasound uses frequencies:

between 2MHz and 12MHz

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Ultrasound travels best through what medium?

Solids

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A transducer that is contained within a sheath and attached to the end of a catheter is an example of:

Intravascular ultrasound

Used for selective destruction of tissue masses is an example of:

HIFU

Therapeutic ultrasound uses frequencies

between .5 and 3MHz

Sound wave propagation is

change in location of energy concentration per time

Waves can be classified as

mechanical and electromagnetic

Examples of electromagnetic waves are:

Light X-rays Gamma rays

Bioeffects refers to:

damage to a cell or tissue

Examples of acoustic variables are

particle motion temperature pressure

Electromagnetic waves need a medium to travel

False

Mechanical waves include sound waves

True

Mechanical waves can be further classified into transverse and longitudinal waves

True

In a longitudinal wave, the particles move parallel to the wave

True

Ultrasound waves can travel through space

False

Ultrasound waves are audible by the human ear

False

Ultrasound waves are produced by piezoelectric crystals found within the transducer

True

As a sound wave vibrates the tissue, heat is produced

True

Heat units are Kelvin, Fahrenheit, and Celsius

True

Ultrasound waves travel by a series of compressions and rarefactions

True

The units of density is kg per meter cubed

False

Pressure is a concentration of force in an area

True

Units of Pressure are cm, feet, miles, and mm

False

ALARA principle is not folled in ultrasound, only when using x-rays

False

Oscillation

to vibrate back and forth

Propagation

to travel

Attenuation

to lose energy as the wave travels through the tissue units are dB

Absorption

a conversion of energy from the sound wave into heat within the tissue

Reflection

the sound wave changes direction and returns to the source

Refraction

the sound wave bends due to a change in the propagation velocity at an angle other than 90 degrees

Hyperechoic

above, or high level echoes as compared with surrounding tissue

Hypoechoic

below, or low level echoes as compared with surrounding tissue

Calcified

strongly echogenic with acoustic shadowing

Anechoic

without echoes

Complex

mixed echogenicity, can have anechoic areas as well as calcifications and/or low level echoes

Transducer

a device which converts energy from one form to another

Hertz

standard unit of frequency

M-mode

type of display used to measure fetal heart rates

Real time B mode

a display of a rapid series of images

What are five operations performed by the receiver?

Amplification Compensation Compression Demodulation Reject

What is the function of the electrical cord on the transducer?

The electrical cord provides power to the crystals in the transducer

What is the function of the housing on the transducer?

The housing protects the components in the transducer

What is the function of the damping layer?

It stops the vibrations, keeps the crystals from producing one long continuous vibration

What is the purpose of using ultrasound gel on patients?

The gel allows the soundwaves to move through the patient more effectively

What does TGC stand for?

Time gain compensation

What does the overall gain do?

It changes the overall brightness of the image

Can the sonographer change the acoustic power of the sound wave?

Yes

Does Color Doppler increase the MI and TI to the patient?

Yes

Name two natural piezoelectric materials

quartz, tourmaline, salt crystals

What is the function of the TGC?

to compensate the returning echoes due to attenuation

Why is PZT used as the element in the transducer over a natural piezoelectric material?

man made easily reproduceable in a controlled setting

Digital Scan converters have replced Analog Scan converters making ultrasound machines more portable

True

Transducers are normally made up of many crystals

True

The thickness of the crystal determines the frequency of the transducer

True

In real time imaging, the crystal is continuously emitting sound waves

False

Therapy was the first medical use of ultrasound

True

Dynamic Range of the image refers to the number of grays that is displayed

True

Write magnification produces a better quality image than Read magnification when using a magnification tool

True

The average speed of sound in soft tissue is 1540 m/sec

True

Explain the round trip effect and give an example.

The round trip effect is the total distance it takes for the soundwave to get to the obect being scanned and back to the transducer. For example, the liver is 6cm deep, but it is another 6cm to return. So, the total distance the sound travels would be 12cm.