Physics Flashcards
propagation
movement of the soundwave
bioeffects
Any damage to the human tissue or cell
digital scan converter
a device that stores computer data and convert it to an image on the ultrasound monitor
transducer
an instrument that converts one form of energy into another
unit of frequency
Hertz (Hz)
unit of pressure
Mm/mg, pascals
unit of temperature
Celcius, Kelvin, Farenheit
longitudinal wave
particles of the medium move in the same direction. An example is sound.
amplitude mode
displayed the amplitude of the sound wave, no longer used
motion (M) mode
used to measure fetal heart rates
medium
what sound waves must have to travel
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.
HIFU
a type of ultrasound used for destruction of cancerous tumors within certain organs
PZT
a man made substance that is used for the crystals in the transducer.
attenuation
a weakening of the sound wave as it passes through the body, usually in the form of heat.
Dual image refers to
allows the display screen to be split in two for easy comparison of the image
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
temporal resolution is most important in what clinical setting?
fetal echo (heart) - moving structures
annotation refers to:
labeling of the image as to organ, probe orientation, patient position
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
Order of the functions of the receiver
Amplification
Compensation
Compression
Demodulation
Reject
What is Hertz (Hz)?
the standard unit of frequency
equal to one cycle per second
Diagnostic ultrasound uses frequencies:
between 2MHz and 12MHz
Ultrasound travels best through what medium?
Solids
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.
