Ultrasound Physics Review Flashcards

Terms Definitions
thousandth
milli
Period
Frequency
Amplitude
power
Intensity
Wavelength
Propagation speed
Seven acoustic parameters
NARROW BEAMS=??
BETTER IMAGES
What does in-vitro dentoe?
Outside
Averaging sequential frames together
Persistance
increases
When frequency increases, attenuation _______.
Doppler shift produces information about what?
Velocity
Damping the transducer improves:
axial resolution
Minimum reflector seperation perpindicular to the sound path that is required ti produce seperate echos
Lateral resolution
PRF IS (RELATED/UNRELATED) TO FREQUENCY?
UNRELATED
attenuation
decrease in intensity, power, and amplitude as sound propagates through a medium
sterilization
the complete destruction of all micro-organisms
11. In oblique incidence, if the propagation speed of the 2 medium are equal, their will be no reflection
a. trueb. false
What is sound?
A mechanical longitudinal wave
Density and speed = ______ directions
opposite
Reverberations
Multiple eches appearing on the display as a result of US bouncing between two reflectors.
1. Multiple
2. Equally spaced
3. parallel to the sound beam
4. Deeper and along a straight line

Assumption # 1 Sound travels in a straight line
During an abdominal ultrasound exam, you encounter all of the following interactions of ultrasound and tissue. Which of the following will not cause redirection of ultrasound energy? Reflection, Scattering, Divergence, Absorption, Refraction
Absorption
Which statement about intensity is most correct:
a. intensity is proportional to amplitude
b. intensity is uniform over the beam area
c. intensity depends upon both power and beam area
d. intensity varies as it travels, creating 5 multiple intensities
C
What transducer factor characterizes the frequency bandwith of the transmitted ultrasound wave?
The Q-Value
True or False: Compensation processes all reflected signals in a similar manner?
False
Granular appearance of images and spectral displays that is caused by the interference of echoes from the distribution of scatterers in tissue
Speckle
B mode presentation of changing reflector position versus time
M-mode
Combinations of positive and or negative pressures
Interference
T/F
AMPLITUDE MAY BE EXPRESSED IN DECIBELS, dB.
TRUE
RANGE OF FREQUENCIES BETWEEN THE HIGHEST AND THE LOWEST FREQ. EMITTED FROM THE TRANSDUCER.
BANDWIDTH
every 13µs signifies 1cm of depth
13µs rule
Density
Describes the relative weight  of a material, weighs more
PZTcasewirematching layerdamping elementradiofrequency shieldacoustic insulator
7 parts of the transducer
Define Axial resolution.
The minimum reflector separation necessary to resolve reflectors ALONG a scan line
What is spacial pulse length analogus to?
wavelength
The amount of attenuation per centimeter is termed:

units: dB/cm
attenuation coefficient.
What is the range of frequencies involved in a pulse?
Bandwidth
Intensity
equals the concentration of energy or power per unit area. The unit for intensity is watts per square cm. the intensity is a useful parameter to help predict the signal strength as well as the risk of bioeffects
During the performance of an ultrasound exam, you decide to adjust the system parameters to improve the image. Which of the following parameters is not adjustable by operator control on ultrasound system: Frequency, Prop speed, power, intensity, or echo s
Prop speed
If the stiffness of a medium increases, the prop speed will:
a. increase
b. decrease
c. reamin constant
A
Which system control adjusts the intensity of the sound beam:
power output
Which of the following transducer types is best suited for cardiac imaging: Mechanical, Linear, Phased, Convex, or Annular
Phased array
True or False: Power doppler displays existence of flow but no direction information?
True
flow towards the transeducer is displayed _____ the O baseline.

a. above
b. below
a. above
Which operator control affects time frame rate: Amplification, Transmit power, Scan depth, TGC, compression
Scan depth
Electric device that reformats echo data into an image for aimage processing, storage and display
Scan converter
Device that converts energy from one form to another
Transducer
Device that presents a visual image derived from voltages recieved from an image processor
Display
_____IS THE ONLY MODE THAT DISPLAYS THE CHANGEING POSITION OF REFLECTORS WITH RESPECT TO TIME.
M-MODE
A WAVE WITH A FREQUENCY EXCEEDING 20,000 Hz (20kHz). SO HIGH THAT IT IS NOT AUDIBLE.
ULTRASOUND
A UNITLESS NUMBER REPRESENTING THE EXTENT OF DAMPING.
QUALITY FACTOR
total attenuation(-dB) = path length(cm) x attenuation coefficient(dB/cm)
equation for total attenuation
disinfection
the application of a chemical agent to reduce or eliminate infectious organisms on an object
19. If the area is doubled & the power remains the same, intensity is,
a. unchangedb. doubledc. halvedd. area has no direct effect on intensity
Define: Grating lobes?
Additional, weaker beams of sound traveling in directions different from the primary beam
Define: Huygen's principle.
Each surface of multiple transducer, diffract producing small waves that join together and form one main energy sound beam
A sound wave strikes a boundary between two media at a 60degree angle is called what?
Oblique incidence
IN SOFT TISSUE, the attenuation coefficient in dB per cm ranges from ____ to ____ times the ultrasonic frequency in MHz.
0.5 to 1.1
19. If the area is doubled & the power remains the same, intensity is,
a. unchanged
b. doubled
c. halved
d. area has no direct effect on intensity
13kHz can also be expressed as what?
13,000 Hz
Which method of testing considers only the pulser and transducer of the US system:
acoustic output
Focal lesions may occur at intensities greater than:
10W/cm2 SPTA
For a single thansducer to offer multiple frequency scanning selections it must have what?
Wide bandwith
Which type of transducer is best suited for small parts imaging?
Linear array
A commonly used process for determining the direction in a doppler instrument is what?
Phase Quadrate Detection
As scan line density increases, the image quality and detail resolution:

a. increases
b. decreases
a. increases
Electronic noise is reduced in the US system by which of the followng methods: Demodulation, Compenstaion, Rectification, Amplification, or Rejection?
Rejection
Number of frames of echo information stored each second
Frame rate
Unit of power or intensity ratio; the number of decibels is 10 times the logarithm of the power or intensity ratio
Decibal-dB
Distance from a focused transducer to the center of a focal region or to the location fo the spatial peak intensity
Focal Length
WHAT ARE THE THREE ACOUSTIC VARIABLES?
1.PRESSURE
2. DENSITY
3. DISTANCE
NUMBER OF CERTAIN EVENTS THAT OCCUR IN A PARTICULAR TIME DURATION.
FREQUENCY
WHAT DOES SPTA STAND FOR?
SPATIAL PEAK, TEMPORAL AVERAGE
THE CONCENTRATION OF THE POWER IN A BEAM:
INTENSITY
Propagation speed
the distance that a sound wave travels through a medium in 1 second
What is 3-D?
2-D slice images presented in plane orientation; commonly used for OB
What happens to duty factor when Pulse duration increases?
DF increases
Define frequency spectrum.
The range of doppler shift frequencies present in returning echoes
Define beam steering.
Movement of the transducer over the area of interest
What is it called when bandwidth is divided by the operating frequency?
Fractional Bandwidth
What is an example of a specular reflector?
Renal capsule
If the received frequency is greater than the transmitted frequency, what will occur:
positive Doppler shift
What type of focusing decreases the frame rate?
Multiple transmit focusing
If you measure the width on a standard one dimensional linear array transducer, which measure of resolution would be the worst: Axial, Lateral, Elevational, Contrast, or Temporal?
Elevational
In order to increase the Nyquist limit and correct aliasing you would: Increase PRF, not change PRF, or Decrease PRF?
Increase PRF
The color assigned to flow towards the transducer is:

a red
b. blue
a. Red
The number of pulses per second is referred to as:

a. PRP
b. PRF
c. Frame rate
d. Line density
b. PRF
You are scanning an interface with high acoustic impedance mismatch. How will this be displayed on the B mode image?
A bright dot
device that converts voltage amplitude to a number.ADC
Analog to Digital converter
2 CHARECTERISTICS OF A HIGH FREQUENCY TXR:
-THIN CRYSTAL
-FAST PZT
power, intensity, and amplitude
What parameters are likely to have units of dB?
focus or focal point
the location where the sound reaches the narrowest point; the point of maximum intensity
What is a pulse of ultrasound?
A few cycles of ultrasound
What is the range of Doppler shifts commonly measured in clinical exams?
-0.01MHz to 0.01MHz
14. If the incidence angle is 20 degrees in oblique incidence & the propagation speed of medium 1 is 1.7mm/us & the propagation speed of medium 2 is 1.6mm/us, calculate the reflection angle
a. 10 degrees
b. 18.8 degrees
c. 20 degrees
d. 22.5 degrees
What detrermines acoustic impedance?
Density and propagation speed of the medium
Which imaging display commonly utilizes pixel interpolation:
sector

(in sector imaging, scan lines diverge further apart in the far field. Pixel interpolation fills in the missing pixels.)
What is the term for a transducer that an array of rectangular elements are arranged in a straight line?
Linear Array
All three display modes have which of the following in common?

a. Lateral resolution
b. Contrast resolution
c. Range equation
d. Lateral Resolution
c. Range resolution
During performance of an abdominal US exam you notice that the temporal resolution is poor. What can you do to improve the temporal resolution: Increasae the number of focal zones, Increase the depth, Increase the scan line density, decrease the acoustic
Decrease scan line density
A diplay device that produced an image by scanning an electron beam over a phosphorcoated screen CRT
Cathode ray tube
LOCATION WHERE THE BEAM REATCHES IT'S MINIMUM DIAMETER
FOCUS OR FOCAL POINT
1 million pascals to 3 million pascals
In clinical imaging, pressure amplitude ranges what?
What is the typical man made crystal used in most transducers today?
Lead Zirconat Titante (PZT)
Two Part Question?
What material has impedance of some intermediate value between those of the transducer elements and the tissue? What does it reduce at the transducer element surface thereby improving sound transmission across it?
1. Matching layer
2. Reflection of ultrasound
During the performance of an abdominal ultrasound examinatioin, you would most expect to encounter refraction in what view?
Transverse view of the gallbladder
Increasing the number of focal zones will:
increase transverse resolution and PRF
What method is used to steer the color beam with a linear array transducer?
Elecrronic time delays
Aliasing is found in all of the flowing imaging modes except:

a. color doppler
b. CW doppler
c. Spectral Pulsed Doppler
d. all of the above shows aliasing
b. Spectral Pulsed Doppler
Yoi are performing an abdominal US exam and select the tissue harmonics operating mode, what advantage will you abtain over conventional imaging?
Improved contrast resolution, and improved signal to noise ration
WHAT IS THE CURIE TEMP?
360 DEGREES C OR 680 DEG. F
-3dB = 1/2 initial strength-6dB = 1/4 initial strength (initial x 1/2 x 1/2)
-3dB rule for negative numbers
What does the damping material in the transducer do?
Increase the spatial pulse length
Pulse duration will be longer when using a new transducer with:
lower frequency (longer period)
more ringing (more cycles in a pulse)
You are scanning an interface at normal incidence in which the acoustic impedance is unchanged from one media to the other. WHat will occur?
There will be no sound reflected
Explain the refraction process
Is a change in direction when a sound pass from one medium to another. Occur with oblique incidence and different velocity
The amplitude of returning signals is dependent upon which factors?
Density of RBCs, blood/tissue signal separation, size of vessels in relation to sample volume size, attenuation
What are the 5 functions of the receiver?
Gain, Compensation (TGC), Compression, Demodulation (Rectification, Sloping, Smoothing), Rejection
SPTP, SPPA, SPTA, SATP, SAPA, SATA
Rank the 6 types of intensities from largest to smallest
Refraction can only occur if you have what 2 factors?
Oblique incidence, and Different prop speeds
All of the following statements correctly describe M-mode EXCEPT:
A. M-mode is a one dimensional display
B. Time is represented on x-axis
C. Motion of the reflector is represented on the vertical axis
D. Obstetrical imaging utilizes M-mode
E. M-mode is a
E. M-mode is a qualitative series of brightness mode pixels
The maximum amount of turbulance is usually detected at:

a. a point proximal to the stenosis
b. at the maximum site of the stenosis
c. distal to the site of the stenosis
c. distal to the site of stenosis
What effect eill you detect in the image if you increase the threshold control?
Decreased appearance of weak echo signals
What region lies beyond a distance of one near-zone length? Name all three names?
1. Far zone2. Far field3. Fraunhofer zone
What is the assumption # for side lobes and grating lobes?
Assumption # 4 Reflections arise from structures positioned alon the beam's main axis
Pulse wave Doppler requires a minimum of:
5 cycles per pulse
(and up to 30 cycles per pulse)
You have chosen to enlarge an US image with read magnificaiton, Which of the following is NOT related to read magnification: pREPROCESSING, iNCREASED PIXEL SIZE, PERFORMANCE ON A FROZEN IMAGE, RESOLUTION LOSS?
Preprocessing - Read magnification is a postprocessing funtion.
THE TIME NEEDED FOR A PULSE TO TRAVEL TO AND FROM THE TRANSDUCER AND THE REFLECTOR IS CALLED:
GO-RETURN TIME OR TIME OF FLIGHT
AS A RULE : DIVIDE ______ BY FREQUENCY IN______ TO AQUIRE THE WAVELENGTH IN SOFT TISSUE.
1.54mm, MHz ( PAY ATTENTION TO THE UNITS!!!!)
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Term:
Definition:
Definition:

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