Physics 111 Chapter 4 Flashcards
The rule that states that it takes 13 ms for sound to travel 1 cm in soft tissue
13 ms rule
Amplitude mode; the height of the spike on the image is related to the strength (amplitude) of the echo generated by the reflector
A-Mode
As low as reasonably achievable; the principle that states one should always use the lowest power and shortest scanning time possible to reduce potential exposure to the patient
ALARA
The part of the receiver that increases or decreases the received echoes equally, regardless of depth.
Amplification
The maximum or minimum deviation of an acoustic variable from the average value of that variable; the strength of the reflector.
Amplitude
The part of the digital scan converter that converts the analog signals from the receiver to binary for processing by the computer
Analog-to-digital (A-to-D) converter
Without echoes or black
Anechoic
The technique that varies the voltage to the individual elements to reduce grating lobes
Apodization
Echoes on the screen that are not representative of actual anatomy, or reflectors in the body that are not displayed on the screen
Artifacts
Brightness mode; the brightness of the dots is proportional to the strength of the echo generated by the reflector
B-Mode
The instrument that shapes and steers the beam on the transmit end
Beam Former
The digital language of zeroes and ones
Binary
Black and white image
Bistable
The smallest unit of memory in a digital device
Bit
Eight bits of memory
Byte
Display that uses an electron gun to produce a stream of electrons toward a phosphor-coated screen
Cathode ray tube (CRT)
A way of processing the pulse to improve contrast resolution and reduce speckle
Coded excitation
A type of reverberation artifact caused by small reflectors
Comet tail
The function of the receiver that changes the brightness of the echo amplitudes to compensate for attenuation with depth
Compensation
The function of the receiver that decreases the range of signal amplitudes present with the machines receiver; opposite of dynamic range
Compression
The ability to differentiate one shade of gray from another
Contrast resolution
The function of the receiver that makes the signal easier to process by performing rectification and smoothing
Demodulation
Part of the digital scan converter that converts the binary signals from computer memory to analog for display and storage
Digital-to-analog (D to A) converter
The series of echo amplitudes present within the signal
Dynamic range
Refraction artifact caused by the curved surface of the reflector
Edge shadowing
Arc-like bands that occur when the machine is too close to an unshielded electrical device
Electrical interference
An artifact caused by sound passing through an area of lower attenuation
Enhancement
One half of a frame on the display
Field
Places pixels where there is no signal information based on adjacent scan lines
Fill-in interpolation
One complete ultrasound image
Frame
Averages the frequencies across the image to improve contrast resolution and reduce speckel
Frequency compounding
The operating or resonating frequency emitted by the transducer
Fundamental frequency
An artifact caused by extraneous sound not along primary beam path; occurs with arrays; reduced or eliminated by apodization, subdicing and tissue harmonics
Grating lobes
Displayed echoes that are relatively brighter than the surrounding tissue; may also be referred to as echogenic
Hyperechoic
Displayed echoes that are relatively darker than the surrounding tissue
Hypoechoic
Display that uses the twisting and untwisting of liquid crystals in front of a light source
Liquid crystal display (LCD)
Motion mode; used to display motion of the reflectors
M-Mode
The timing component of the ultrasound machine that notes how long it takes for signals to return from reflectors
Master synchronizer
An artifact caused by sound bouncing off of a strong reflector and causing a structure to appear on both sides of the reflector
Mirror image
An artifact caused by the beam bouncing off of several reflectors before returning to the transducer
Multipath
Principle that pressure waves change in shape as they travel deeper, through in a disproportionate way
Nonlinear propagation
Waves that are not pure sine waves
Nonsinusoidal
Output power; strength of sound entering the patient
Output
Receiver function that increases or decreases all the echo amplitudes equally
Overall gain
Picture archiving and communication system; a type of display and storage device commonly used in ultrasound and other imaging modalities
PACS
The smallest component of a 2D digital iamge
Pixel (picture element)
Occurs in the A to D converter; The image must be live
Preprocessing
Occurs in the D-to -A converter; the image must be frozen
Postprocessing
Part of the beam former that controls the amount of energy in the pulse
Pulser
Equation used to calculate the distance to the reflector; in soft tissue, d=0.77t where “d” is the depth of the reflector and “t” represents the round trip time of the pulse
Range equation
The type of magnification performed in the D to A converter (postprocessing) that magnifies the image by enlarging the pixels
Read zone
The component of the machine that processes the signals coming back from the patient
Receiver
The part of the receiver that inverts the negative voltages to positives
Rectification
Function of the receiver that is used to reduce image noise; sets a threshold below which the signal will not be displayed
Rejection
An artifact caused by the beam bouncing between two strong reflectors
Reverberation
A type of reverberation artifact caused by air
Ring down
The part of the ultrasound machine that processes the signals from the receiver; consist of the A - to - D converter, computer memory, and D - to - A converter
Scan converter
Created when one or more pulses of sound return from the tissue containing information related to the depth and amplitude of the reflectors
Scan line
An artifact caused by the failure of sound to pass through a strong attenuator
Shadowing
An artifact caused by extraneous sound that is not found along the primary beam path; occurs with single-element transducers
Side lobes
Part of the demodulation component of the receiver; an “envelope” is wrapped around the signal to eliminate the “humps”
Smoothing
Algorithm used in signal processing to reduce the amount of acoustic speckle
Speckle reduction
Dividing the piezoelectric elements into very small pieces to reduce grating lobes
Subdicing
Harmonic signal produced by the patient and is a multiple of the fundamental frequency; also referred to as native tissue harmonic imaging
Tissue harmonics
Time gain compensation; Compensation
TGC
The smallest component of a 3D image
Voxel (volume element)
The type of magnification performed in the A -to- D converter (postprocessing) that magnifies the image by redrawing it before it is stored in memory
Write zoom
the plane that is perpendicular to the beam path
X-Axis
The plane that is parallel to the beam path
Y-Axis
The brightness, or amplitude, of the dots on the display
Z-Axis
Having two possible states
Bistable
Sequential display of all the frames stored in memory at a controllable frame rate
Cine loop
A sophisticated form of transmission in which the driving voltage pulses have intrapulse variations in amplitude, frequency, and/or phase
Coded excitation
A single one or two way path for transmitting electric signals, in distribution from other parallel paths; an independent transmission delay line and transducer element path; an independent reception transducer element , amplifier, analog - to - digital converter, and delay line path
Channel
Conversion of voltage pulses from radio frequency to video form. Also called demodulation , amplitude detection and envelope detection.
Detection
Imaging tissue stiffness by tracking movement under mechanical stress
Elastography
A backlighted rectangular matrix of thousands of liquid crystal elements
Flat panel display
Constant display of one of the frames in memory
Freeze
