Principles & Instruments PT 1 Flashcards by Maddie Mebruer

2D image is composed of

pixels

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3D image elements

voxels

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an ellipse can be used to measure

area

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comet tail and ring down are

reverberation artifacts

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contrast res =

dynamic range / shades

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What is the contrast res for a system with a 4 bit memory and 32 dB dynamic range?

2 dB/shade

4 bit memory will use 16 shades of gray (2x2x2x2)
contrast res = dynamic range over shades
32 dB / 16 shades = 2 dB/shade

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advantage of virtual beam forming (VBF) over traditional pulse echo imaging (PEI)

VBF allows for simultaneous real-time gray scale, color, and spectral doppler display

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why can VBF display info collected in all 3 modes?

it allows for very fast frame rates

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in traditional PEI, the gray scale and color image

is frozen or refreshes very slowly while doppler tracings are displayed

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VBF uses ______ to improve detail resolution across the whole image, ______ is not needed

receive focusing

transmit focusing

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Pulse-echo systems use strength and _____ of received signals to create the gray scale image. Magnitude and _____ of the received signal are used to create the doppler display

time of flight

direction

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gain =

ratio of amplifier output to the electric power input (measured in dB)

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increasing the number of bits per pixel in an image memory will improve the

contrast resolution

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the ability of a display to distinguish between echoes of different intensities

contrast resolution

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increased pixel number with higher numbers of bits per pixel will demonstrate

the best contrast res on a digital display

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bit density and contrast res relationship

direct

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more bits per pixel = more shades of gray =

improved contrast res

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spatial compounding can reduce

artifacts like enhancement or shadowing

shut this function off to make a stone more evident

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reducing rejection or increasing dynamic range will _____ the number of grays on the image

increase

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pulse duration

time it takes for one pulse to occur

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System control that simultaneously enhances far field echoes and diminishes near field echoes

time gain compensation

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increases amplitude of all reflections to create image

overall gain

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transducer component that reduces sensitivity and efficiency of the US system

damping layer by preventing the lowest intensities from forming

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circumference =
area =
volume =

cm
cm^2
cm^3

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8 bit of memory has how many shades of gray?

256 shades of gray 8 bit memory has 2^8 = # of shades of gray = 2x2x2x2x2x2x2x2 = 256 shades of gray

removes low amplitude signals and noise from the image

increasing rejection

increases the # of shades of gray displayed on the image, including low level echoes and noise

increasing compression

amplification of the received signal occurs in the

beam former

the beam former generates

the voltages applied to the transducer

the beam former determines

PRF, frequency, and intensity of the beam

scanning, focusing, and apodization are functions of the

beam former

US system component responsible for changing PRF with changes in depth

pulser

adjusts timing of voltage applied to crystal to adjust PRF

pulser

allows focusing at multiple depths on the image

dynamic receive focusing (NOT ADJUSTABLE)

System component responsible for 3D image acquisition and presentation

image processor

____ is predominant factor causing attenuation of the US beam and can be counteracted by ____

sound absorption increasing TCG settings in the far field

tissue harmonic imaging

reduces grating lobe and side lobe artifacts

cine is

postprocessing that allows for review of the stored image data from the last few seconds of real time scanning

M-Mode horizontal axis and vertical axis

time (horizontal) | distance (vertical)

2D imaging is best when the US beam strike the specular interface at what angle?

90 degrees

perpendicular angle of incidence increases

specular reflection

system control to improve anterior aortic wall

center beam perpendicular to vessel wall

contrast resolution (dB/shade) =

dynamic range / # of shades of gray

converts scan line data into image format for display

image processor

period of 5 MHz transducer

.2 microseconds 5 MHz = 5,000,000 Hz period = 1 / frequency = 1/5,000,000 = .0000002 s

graphic representation of the motion of a structure over time

M-Mode

reducing sector size will reduce # of scan lines produced and increase frame rate, increasing

temporal resolution

converts received signal from radio frequency form to amplitude (video) form

detection or demodulation

sector angle and frame rate relationship

inverse

sector size and # of scan lines relationship

direct

adjusts # of gray levels to maintain gray scale within range of human vision

compression

larger dynamic range =

improved ability to see subtle differences between tissues

smaller dynamic range =

more black and white image

amount of compensation necessary for different echoes varies with reflector ____

depth

input power = .05 mW output power = 500 mW gain = ?

40 dB

gain =

ratio of amplifier output to electric power input

can change the image data displayed on an archived exam on the US system

change the gray map

reduces appearance of posterior shadowing and enhancement

spatial compounding

each returning reflection is made stronger/larger for additional processing and storage

amplifier

overall gain adjustment does not improve

SNR

amplification is adjusted by

overall gain control

harmonic frequencies are generated

as sound travels through the medium

sound moves slightly faster in areas of ____ and slightly slower in areas of ____

compression | rarefaction

edge enhancement, pixel interpolation, persistence, and 3D image acquisition are all types of

preprocessing

process performed in beam former where the output voltage is varied to decrease the formation of lobe artifacts

apodization

doubling sector width BUT halving line density will cause ____ for temporal res

no change

beam former parts (in order) to produce and receive sound waves

pulser-->pulse delays-->transmit/receive switch-->amplifier-->analog to digital convertor-->echo delays-->summer

low frequency, high amplitude sound waves will cause

an increase in MI and risk for cavitation

activation of B-color improves

contrast resolution

focusing of the transmitted and received beam occurs in the

beam former

when evaluative heavily calcified arteries, what system setting should be increased to improve to demonstration of flow in the vessels

persistence and sensitivity

instrument control the sonographer uses to adjust amplitude of a reflected sound wave

receiver gain

POSTprocessing assignment of color instead of gray

B color

harmonic imaging primarily improves

spatial resolution with the greatest affect (improvement) on lateral resolution

M-mode vertical axis

depth

changes element back and forth from transmit to receive

beam former

system control that reduces noise and smooths the image using frame averaging

persistence

when using virtual beam forming the US beam is

laser thin

beam former component that protests the sensitive circuitry of the amplifier

transmit receive switch

of pulses in a scan line will affect

of focal zones

console setting that can be changed to adjust the propagation speed of the transmitted wave

there is no way to adjust this; propagation speed is determined by properties of the media it travels through

in order to improve spatial res and SNR, ____ uses frequency modulation to manipulate the transmitted beam

coded excitation

3D images displayed in real time

4D imaging

RIS (radiology information system)

refers to a software program that stores medical records and patient info

increased frequency improves

axial res, lateral res, and beam width

spatial high pass filter used to emphasize changes in brightness across the image to make boundaries of vessels more prominent

edge enhancment

increasing edge enhancment

increases image contrast and decreases contrast res

filter and compression are functions of the ______

signal processor

type of receive focusing; uses more crystals to receive deeper reflections than to receive shallow reflections; reduces appearance of lobe artifact

dynamic aperture

necessary machine setting when performing contrast eval of the heart

MI set below 0.3 | High MI will cause premature bursting of microbubbles

coded excitation improves

contrast res

leads to misregistration of data and incorrectly placed pixels deeper than the normal location

US system is calibrated to 1450 m/s as speed of sound in ST; | reflected info will appear to take longer causing pixel placement deeper than normal location

part of beam former that creates a digital echo signal that is sent to the signal processor

analog to digital convertor

distance to reflector = velocity x 1/2 (time of flight)

range equation

13 microsecond rule

distance in cm = time of flight / 13 microseconds

PRF of pulser is ____ PRF of US system

equal to

control that adjusts the image contrast

dynamic range

control that affects power of the beam

transmit gain

If you are scanning an abd but accidentally select carotid preset

depth setting will be very superficial causing potential nonvisualiztion of the abdominal structures

disadvantage to increased edge enhancement

amplifies noise and speckle = reduced SNR

what region of the TCG curve is the deepest region attenuation compensation can occur

the knee

the strength of a received echo determines the ___ on the display

brightness of the pixel

performs bandpass filtering, amplitude detection/demodulation and compression

signal processor

field of view size and frame rate relationship

indirect

Frequency compounding effect on image

improves SNR, spatial res, and image quality, reduces speckle and clutter artifact

PACS

picture archiving communication system

even and odd harmonic frequencies are created by

nonlinear behavior sound beams

created by tissue boundaries during transmission of fundamental frequency through the tissue; result of nonlinear behavior

harmonic frequencies

resulting harmonic beam is

narrower, smaller side lobes, better lateral res, and less clutter with improved contrast resolution

second harmonic frequency =

2 x fundamental frequency

demodulation is only necessary when

TV monitor is used

removes carrier signals and reconstructs the signal envelope

demodulation

to increase amplitude of the US pulse produced by the transducer

voltage amplitude form the pulser must increase