Chapters 1 & 2 Flashcards
Color-doppler display
color-coded 2d and 3d presentations of doppler info. (Superimposed on gray-scale images.) Flow directions toward and away from the transducer are presented as different colors on the display.
Doppler effect
a change in frequency caused by reflector (The structure that sends the echoes back) motion.
Gray-scale image
image composed of different ranges of brightnesses (gray levels) between white and black.
Image
A reproduction, representation, or imitation of the physical form of a person or thing.
linear image
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Operating principle 1
Positional info is determined by knowledge of the direction of the pulse when it enters the patient and by measurement of the time it takes for each echo to return to the transducer. The proper location to present the echo can then be determined from a starting point on the display (usually at the top). With knowledge of the sound speed, the instrument uses the echo arrival time to determine the depth of the structure that produced that echo.
depth of a structure is determined by the measurement of the time it takes for the echo to return to the transducer
Operating principle 2
sends several pulses of ultrasound through the cross section of anatomy to be imaged but does not produce a one-for-one correspondence of pulse and displayed scan line. Instead, all the echo information from throughout the anatomic cross section sis collected, and then massive computational processes determine the location and strength of each echo produced at each location in the anatomy. This approach is used in recent instruments and produces improved quality compared with principle 1.
sends several pulses and instead of a one-for-one correspondence of pulse and scan line, all the echo info is collected and copmuters determine the location and strength of each echo. New approach. Improved image quality
Pulse-echo technique
Ultrasound imaging in which pulses are reflected and used to produce a display.
Scan line
a line produced on a display that represents ultrasonic echoes returning from the body. A sonographic image is composed of many such lines.
Sector image
An anatomic image presented in a pie slice-shaped format.
Sonography
written sound. The use of ultrasound in medical anatomic and flow imaging. Can be 2D or 3D.
Spectral-doppler display
using doppler info for quantitative analysis. The one that has like the chart. The presentation of Doppler info in a quantitative form of Doppler shift versus time. Visual display of a Doppler spectrum. The location from which the spectral-doppler info was acquired is displayed as well.
Transducer
generates the ultrasound pulses and receives the returning echoes. Converts energy from one form to another (mechanical to electrical in sonography)
Ultrasound
Sound having frequency greater than what humans can hear. Greater than 20khz.
Volume imaging
3D imaging. Is like creating slices and then combining them like in MRI and CT.
Ultrasound instrument
is the system aka the ultrasound machine. Processes the echoes and presents them as visible dots on the display.
Explain the pulse-echo principle used in sonographic imaging
Pulses of ultrasound generated by a transducer are sent into the patient where they produce echoes at organ boundaries and within biological tissues. These echoes return to the transducer where th4ey are detected and presented on the display of a sonographic instruemtn. // Ultrasound pulses are sent into the tissues to interact with them and to obtain info about them. Then echoes return from the tissues providing info that enbables anatomic imaging and observation of motion and flow.
List the differences between operating Principles 1 and 2
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Describe the image formats used in sonography
2D images are presented in linear and/or sector forms.
List the ways in which Doppler information is presented.
Audible, color-doppler, and spectral-doppler forms.
Diagnostic ultrasound is between?
2 MHz-15MHz
The brightness of each dot corresponds to what?
the echo strength.
Absorption
conversion of sound to heat.
Acoustic
having to do with sound.
Acoustic variables
pressure, density, and particle vibration; sound wave quantities that vary in space and time.
Amplitude
maximum variation of an acoustic variable or voltage.
Attenuation
decrease in amplitude and intensity with distance as a wave travels through a medium.
Attenuation coefficient
attenuation per centimeter of wave travel.
Backscatter
sound scattered back in the direction from which it originally came.
Bandwidth
range of frequencies contained in an ultrasound pulse; range of frequencies within which a material, device, or system can operate.
Compression
reduction in differences between small and large amplitudes. Region of high density and pressure in a compressional wave.
Constructive interference
combination of positive or negative pressures.
Continuous wave (CW)
a wave in which cycles repeat indefinitely; not pulsed.
Contrast agent
a suspension of bubbles or particles introduced into circulation to enhance the contrast between anatomic structures, thereby improving their imaging.
Coupling medium
a gel used to provide a good sound path between a transducer and the skin by eliminating the air between the two.
Cycle
one complete variation of an acoustic variable.
Decibel (dB)
unit of power or intensity ratio; the number of decibels is 10 times the logarithm of the power or intensity ratio.
Density
mass divided by volume.
Destructive interference
: combination of positive and negative pressures.
Duty factor
fraction of time that pulsed ultrasound is on.
Echo
reflection.
Energy
capability of doing work.
Fractional bandwidth
bandwidth divided by operating frequency.
Frequency
number of cycles per second.
Fundamental frequency
the primary frequency in a collection of frequencies that can include odd and even harmonics and subharmonics.
Harmonics
frequencies that are even and odd multiples of another, commonly called fundamental or operating frequency.
Hertz (Hz)
unit of frequency, one cycle per second; unit of pulse repetition frequency, one pulse per second.
Impedance
density multiplied by the sound propagation speed.
Incidence angle
angle between incident sound direction and a line perpendicular to the boundary of a medium.
Intensity
: power divided by area.
Intensity reflection coefficient
reflected intensity divided by incident intensity; the fraction of incident intensity reflected.
Intensity transmission coefficient
transmitted intensity divided by incident intensity; the faction of incident intensity transmitted into the second medium.
Interference
combinations of positive and/or negative pressures.
Kilohertz (KHz)
one thousand hertz.
Longitudinal wave
wave in which the particle motion is parallel to the direction of wave travel.
Medium
material through which a wave travels.
Megahertz (MHz)
one million hertz.
Nonlinear propagation
sound propagation in which the propagation speed depends on pressure causing the wave shape to change and harmonics to be generated.
Oblique incidence
sound direction that is not perpendicular to media boundaries.
Penetration
imaging depth.
Period
: time per cycle.
Perpendicular
geometrically related by 90 degrees.
Perpendicular Incidence
sound direction that is perpendicular to the boundary between media.
Power
rate at which work is done; rate at which energy is transferred.
Pressure
: force divided by the area in a fluid.
Propagation
progression or travel.
Propagation speed
speed at which a wave moves through a medium.
Pulse
A brief excursion of a quantity from its normal value; a few cycles.
Pulse duration
interval of time from beginning to end of a pulse.
Pulse-repetition frequency
number of pulses per second; sometimes called pulse repetition rate.
Pulse-repetition period
interval of time from the beginning of one pulse to the beginning of the next.
Pulsed ultrasound
ultrasound produced in pulsed form by applying electric pulses or voltages of one or a few cycles to the transducer.
Range equation
relationship between roundtrip pulse travel time, propagation speed, and distance to a reflector.
Rarefaction
region of low density and pressure in a compressional wave.
Rayl
unit of impedance.
Reflection
portion of sound returned from a media boundary; echo.
Reflection angle
angle between the reflected sound direction and a line perpendicular to the media boundary.
Reflector
media boundary that produces a reflection; reflecting surface.
Refraction
change of sound direction on passing from one medium to another.
Scatterer
an object that scatters sound in many directions because of its small size or its surface roughness.
Scattering
diffusion or redirection of sound in several directions upon encountering a particle suspension or a rough surface.
Shear wave
transverse wave.
Sound
traveling wave of acoustic variables.
Spatial pulse length
length of space over which a pulse occurs.
Speckle
the granular appearance of images and spectral displays that is caused by the interference of echoes from the distribution of scatterers in tissue.
Specular reflection
: reflection from a large (relative to wavelength), flat, smooth boundary.
Stiffness
property of a medium; applied pressure divided by the fraction volume change produced by the pressure.
Strength
nonspecific term referring here to amplitude or intensity.
Transmission angle
angle between the transmitted sound direction and a line perpendicular to the media boundary.
Transverse wave
a wave in which the particle motion is perpendicular to the direction of wave travel, also called a shear wave.
Ultrasound
sound having a frequency greater than what humans can hear, that is, greater than 20kHz.
Wave
traveling variation of one or more quantities.
Wavelength
length of space over which a cycle occurs.
