Sonography Flashcards
sound waves beyond audible range use frequency of
1-10 MHz
transmission of high frequency mechanical vibrations
greater than 20 kHz
desciribed by the Curie brothers in 1880
principle by which the ultrasound beam is produced
states that when certain crystals undergo mechanical deformation, a potential difference develops across the two surfaces of the crystals
piezoelectric effect
descibes the property of certain crystals such as quartz, expading and contracting in response to the application of electircal filed
pressure electric
device that converts energy from one form ot another
converts electrical energy fo ultrasonic energy
ultrasound transducer
measures the ability to distinguish between adjacent structures
resolution
a propgation of energy that moves back and forth or vibrates at a steady rate
acoustice wave
ultrasonic wave can be focused, refracted, reflected, or scattered between different media
a factor in determing what happens to an ultrasound beam at interfaces with different media
acoutic imedance
reduction of acoustic amplitude along propagation pathway as a result of diffraction, absorption, scattering, reflections or any other process that redirects the signal away from the receiver
attenuation
sound waves that reflected by internal structures back to the transducer
echoes
is a propagation of energy that moves back and forth or vibrates in a steady rate
acoutic wave
are mechanical oscillation that are transmitted by particles in gas, liquid, or solid medium
sound waves
referes to sound waves beyond the audible range of 16,000 - 20,000 hz
ultrasound
diagnostic ultrasound uses
1-10 MHz
bending wave fronts
refraction
acoutic energy relected from a structure that interferes with the expected path
reflection
diffusion or redirection of sound in different directions
scattered
to concentrate the sound beam into a smaller beam area than would exist without focusing
focused
determined by the density and elastic properties of the medium
velocity of sound
impedes sound transmission (lungs, stomach, bowel)
air
attenuates sound
bone
sound varies slightly from one tissue to another
soft tissue
multiple frames per second over selected areas of the body
ability to visualize structures as they change position such as peristalsis in the bowel and stomach & pulsatile vascular and cardiac structures
real time imaging
a change in frequency when the motion of laminar or turblent flow is detected within a vascular structure
makes possible the determination of velocity and direction of flow of blood
doppler effect
techinique that assings a color scale to the change in frequency or dopple shift
color-flow doppler
signifies direction of flow towards the tranducer
red
shift away from the transducer
blue
is used inside transducer, behind the piezoelectic element to absorb useless vibration
damping material or backing
