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.