Intro Quiz 1 Physics Flashcards
A-Mode
Amplitude Modulation
Distance between transducer and structure determines where an echo is seen along hte time axis
1 dimensional image
Not used anymore
Analog Scan Converter
device in which data are represented by variable, measurable, physical quantities. Length, width, voltage or pressure
B-Mode
2D presentation of echo producing interfaces.
A mode signal converted to dots which vary in brightness depending on echo strength
Brightness Modulation
Cavitation
formation of cavities in a body tissue or an organ resulting from the sudden formation and collapse of low pressure bubbles by means of mechanical forces
Digital Scan Converter
image processing device that uses a stable electronic circuit to store and manipulate ultrasonic images in memory. The device then reconstructs and displays these images simultaneously to create one image
Doppler effect
change in observed frequency of a wave. Freq increases as source and observer get closer, decreases as they move apart
Gray Scale Imaging
series of shades from black to white the more shades the more realistically an image can be recorded and displayed
M-Mode
series of B-Mode dots are displayed on moving time base graph to show moving structures
basis of echocariography prior to real time scanning
used in conjunction with real time imaging in adult, pediatric and fetal echo
Piezoelectric Effect
Mechanical deformation occurs when an electrical field is applied to a crystal the crystal vibrates mechanically. When a crystal vibrates mechanically it creates an electrical field
3-D imaging
waves sent from many directions to the returns are used to build a volume image in 3 dimensions
4-D Imaging
3-d imaging with the addition of real time
Ultrasound
sound with freq above the limits of human hearing greater than 20kHz
Transverse Waves
Waves that move in an up and down motoin
Longitudinal Waves
Waves that move in a line
Compression
area of wave that gets closer together
Rarefaction
area of wave that spreads apart
Medium
material through which a wave is transmitted
Accoustic parameters
period
frequency
amplitude
power
intensity
wavelength
propagation
Period of wave
time
frequency of wave
1/time
amplitude of wave
“Bigness” of wave
dofference between peak and avg value of the wave
power
force
rate of energy transfer or rate which work is preformed
intensity
concentration of strength of a wave
Intensity = watts/cm^2
wavelength
distance from one peak to the next
propagation speed
speed wave travels through medium (avg 1540 soft tissue)
Hertz
measurement of frequency
Infrasound
sound below the human hearing level
Audible sound
20-20kHz
DMS frequency
2mHz-12mHz
Bio effects
any damage to tissue
ALARA as low as reasonably achievable
Intravascular Ultrasound
30MHz-40MHz
asses vessel walls characterize plaque morphology
transducer contained in a sheath attached to catheter
no air means high preq usable
Therapeutic Ultrasound
.5MHz-3MHz
beam intensity result in tissue temperature increases
4°C as deep as 5cm
increases blood flow
treats muscle spasms, tendonitis and bursitis
joint swelling
High Intensity Focused Ultrasound
HIFU
used for selective destruction of tissue volumes
cancerous lesions in liver, kidney, breast and prostate
focusing the beam allows energy concentration on affected area while sparing surround tissue
Wave Propagation
Worse in Gas
better in liquid
best in solids
Sound wave propagation
sound traveling pressure variation
regions of compression and rarefraction
particles vibrate back and forth
parallel to the directoin of travel
Mechanical Wave
needs physical interaction
must have medium
longitudinal
transverse
Electromagnetic Waves
travel in medium or vacuum
light, heat, X-rays, gamma rays TV rays
transer of energy through a varying electrical and magnetic field
Acoustic variables
Pressure
Density
Temperature
particle motion
Pressure
concentration of force
Pascals
varies cyclically as sound wave propagates
Density
p=mass/volume
compression increases
rarefraction decreases
non linear imaging Harmonic Imaging
units kg/m3
Temperature
any mechanical movement produces heat
sound wave vibrate the tissue and some wave energy is lost to heat with tissue
important in Bioeffects
Celcius
Kelvin
Fahrenheit
Particel Motion
particels of tissue being imparted with momentum and traveling into the locale of the nearest neighbors
osscillate back and forth about their original location allowing energy to propagate along the wave p[ath
particles DO NOT travel with the wave
ALARA
As Low As Resonably Achievable
short scan time
low power settings
short use of color and spectral
Attenuation
decrease in wave amplitude due to mechanical wave interaction wiht mnedium
units dB
absorption
reflection
refraction
Absorption
conversion of energy from wave to heat within medium
as Freq increases amount of energy lost increases
Reflection
sound wave changes direction and does not continue to travel forward
returns to source
foundtation for diagnostic ultrasound
Ultrasound based on processing these refelctions
Refraction
bending of wave
change in propagation velocity when angle of incidence is other than 0
Anechoic
without echoes
cysts
fluid filled organs
Hypoechoic
low level reflected signals
Hyperechoic
highly echogenic tissues
moderate to high reflected signals
calcified echoes
strongly echoic
usually with acoustic shadows
Complex
mixed echogenicity
with or without shadowing
Transducers
Device that converts energy from one form to another
Transducer components
Crystal
matching layers
Damping material
Transducer case
electronic cable
Crystal
diameter determines beam shape
like beam of flashlight
shape is region in the patient which sound travels
matching layers
provide an acoustic connection between crystals and skin
reduces amount of reflection from large acoustic mismatch
allows wave to travel into the body
gel