ESP US physics pt 1
The angle between an ultrasound pulse and the boundary between two media is 56*(degrees). This is called?
Oblique incidence
Refraction only occurs if there are:
Oblique incidence and different propagation speeds
The angle between an ultrasound pulse and the boundary between 2 media is 90*. What is this called?
Orthogonal incidence
_______ is the time to complete one cycle.
Period
What happens to the speed of sound in a medium when the bulk modulus of the medium decreases?
Slower
Which transducer would be best to image superficial structures?
Small diameter, high frequency
Put in decreasing order of propagation speed A) gas B) liquid C) solid
Solid, liquid, gas
T/F: The sonographer cannot change, directly or indirectly, the duty factor of an ultrasound machine
F
T/F: There have not been biological effects from US found in the laboratory.
F
T/F: With normal incidence the angle is 180 degrees.
F
T/F: With right angle incidence, reflections are always generated at a boundary if the propagation speeds of the media are different
F
What improves signal-to-noise ratio? A. frame averaging B. gray scale C. edge enhancement D. receiver gain E. dynamic range
Frame averaging
The region from the transducer to the minimum beam cross-sectional area is the
Fresnel zone
Where are harmonics created?
In the tissue
If the frequency of US is increased from 0.77 MHz to 1.54 MHz, what happens to the wavelength?
Halved
If the frequency of an US wave is doubled, what happens to the period?
Halved
If the intensity of a sound beam remains unchanged while the beam area is reduced in half, what has happened to the power?
Halved
When the ultrasound machine displays only strong reflecting objects and nothing else, the sonographer should
Increase output power
Which is not an acoustic variable? Density Pressure Distance Intensity
Intensity
A single element transducer is focused
by the manufacturer
While scanning in a water tank, what location in a sound beam has the highest intensity?
focal point
The units of PRF are
per minute
Impedance is the ______ of _____ and _____
product; propagation speed & density
_______ resolution is determined by the SPL
radial or axial
Which of the following choices best describes an ideal epidemiologic bio effects study? A.Randomized and prospective B. benefits outweighs the risks C. retrospective and optimized D. ideal and non-biased E. prudent and safe
randomized and prospective
Snell's law describes the physics of
refraction
What are attenuations three components?
scattering, reflection, absorption
In which of these biologic tissues will sound waves propagate most quickly? Tendon, blood, lung, fat, amniotic fluid
tendon
T/F: Lateral resolution is also called axial
F
T/F: Lateral resolution is also called range
F
A pulse is emitted by a transducer and is traveling in soft tissue. The go-return time or time of flight of a sound pulse is 130microseconds. What is the reflector depth?
10 cm
A sound wave's frequency is 10 MHz. The wave is traveling in soft tissue. What is its wavelength?
.15 mm
What is the approximate attenuation coefficient of 1 MHz US in soft tissue?
.5 dB/cm
What is the minimum value of the duty factor?
0.0%
What is the frequency of a wave with 1msec period?
1 kHz
The most likely amount of selection at a boundary between soft tissues is:
1%
The speed of US in soft tissue is closest to: 1,540 m/s 1.54 km/ms 1,500 m/s 1,540 mm/sec
1,500 m/s (1,540)
The duty factor for continuous wave ultrasound is
1.0
Sound intensity is decreased by 75%. How many decibels of attenuation is this?
1.25MHz
Biologic effects have not been documented below what intensity? (SPTA)
100mW/cm2
Which has the correct order? Mega-mili-kilo-micro
10^6 10^-3 10^3 10^-6
The frequency closest to the lower limit of US is: a. 19,000 kHz b. 10,000 MHz c. 20,000 msec d. 15,000 Hz
15,000 Hz
decimal uses a base of 10, binary uses a base of
2
Which of the following sound waves is ultrasonic and least useful in diagnostic imaging? A. 30 kHZ B. 8 MHz C. 3,000 kHz D. 15 Hz E. 8,000 Hz
30 kHz
How many bits are needed to represent 16 shades of gray?
4
Depth calibration of a machine measures 100mm spaced wires to be 90mm apart. Scanning reflectors 50mm apart, what will the machine calculate the distance to be?
45mm
The fundamental frequency of a transducer is 2.5 MHZ. What is the second harmonic frequency?
5 MHz
How many cm are in 60 millimeters?
6
For Doppler, which incident angle results in no shift?
90 degrees
The most typical amount of transmission at a boundary in biologic media is:
99%
What best describes a sound beam
A collection of mechanical vibrations in the form of compressions and rarefactions
What is the standard communication between medical imaging computers?
A to D conversion
Which of the following is associated with power mode doppler? A. Poor temporal res and flash artifact B. Lower sensitivity and good temporal res C. High sensitivity and high frame rates D. Flash artifact and reduced sensitivity E. Good temporal res and flash artifact
A. Poor temporal resolution and flash artifact
All the following are true except: A. Two waves with identical frequencies must interfere constructively B. Constructive interference is associated with waves that are in-phase C. Out-of-phase waves interfere destructively D. Waves of different frequencies may exhibit both constructive and destructive interference at different times
A. Two waves with identical frequencies must interfere constructively
Under which of the following conditions is axial resolution improved? A. decreased SPL B. Decreased pulse amplitude C. Decreased pixel size D. decreased imaging depth E.decreased beam diameter
A. decreased SPL
A transducer with more than one active element is called
Array
The effects of soft tissue on an US are called
Acoustic propagation properties
Reject is used to
Adjust the appearance of lowly reflective objects
** If a 5 MHZ sound is traveling in the tissues listed below, which will have the shortest wavelength? Fat Air Muscle Bone
Air (the speed of sound is lowest in air)
An ultrasound machine has a digital scan converter but has an analog input signal. The machine needs to have a ____________.
Analog to scan converter
Which has the greatest amount of attenuation?
Bone
** If a 5 MHZ sound is traveling in the tissues listed below, which will have the longest wavelength? Fat Air Muscle Bone
Bone (speed of sound is highest in bone)
Circumference may be measured in units of
Cm
T/F: Doppler shifts always occur if the sound source and receiver are in motion
F
Put in decreasing order: A) deca B) deci C) micro D) centi
Deca, deci, centi, micro
Compression is used to
Decrease the range of amplitudes
As a result of ____ the propagation speed increases
Decreasing compressibility, decreasing density
What best describes the features of a sound wave and medium that determine the speed of sound in the medium?
Density of the medium and stiffness of the medium
What is the accuracy of reflector depth position on an A-mode, B-mode or M-mode display called?
Depth calibration
If a reflector is moved twice as far away from the transducer, how will this affect the time-of-flight of a sound pulse?
Double it
(t/f) lateral resolution is also called longitudinal
F
What happens to the speed of sound in a medium when the bulk modulus of the medium increases?
Faster
Sound waves are:
Longitudinal and mechanical
Which of the following will result in the highest MI? A. High frequency and low power B. High intensity and high frequency C. Low frequency and high signal impedance D. Low intensity and low frequency
Low frequency and high signal impedance
Under which circumstance is cavitation most likely to occur? A. High frequency, low power B. High intensity, high frequency C. Low intensity, low frequency D. Low frequency, high signal amplitude
Low frequency, high signal amplitude
Under which circumstance is the MI highest? A.High frequency, low power B. High intensity, high frequency C. Low intensity, low frequency D. Low frequency, high signal amplitude
Low frequency, high signal amplitude
How is range ambiguity artifact eliminated?
Lower the PRF
How is lateral resolution measured if this test object is scanned from the top?
Measure the length of line B
With normal incidence, what factors affect refraction of US? A) propagation speeds B) frequencies C) attenuation coefficients D) none of the above
None of the above
Which of the following is not a beam steering technique for a mechanical scanhead?
Phased beam
The time from the beginning of a pulse until its end is ______?
Pulse duration
If a wave's amplitude is doubled, what happens to the power?
Quadrupled
Which of the following tissues is most likely to create Rayleigh scattering? RBC Muscle Fat Bone
RBC
Which of the following is determined by the source and the medium? A. Frequency B. Period C. Propagation Speed D. Range resolution
Range resolution
As the impedances of two media become vastly different the. A) reflection increases B) transmission increases C) refraction increases D) absorption increases
Reflection increases
If the frequency of US is increased from 0.77 MHz to 1.54 MHz, what happens to the propagation speed?
Remains the same
Which of these intensities is smallest? SATP SPTP SATA
SATA
___ is a redirection of US in many directions as a result of a rough boundary between two media.
Scattering
You are performing a QA study on an US system using a tissue equivalent phantom. You make an adjustment using a knob on the system console that changes the appearance of reflector brightness from fully bright to barely visible. What are you evaluating?
System sensitivity
T/F: A sound wave is a pressure wave made of compressions and rarefactions
T
T/F: A system which was working well now does not display clear images in the far field. This may be a problem with the monitor
T
T/F: A system which was working well now does not display clear images in the far field. This may be a problem with the receiver
T
T/F: A system which was working well now does not display clear images in the far field. This may be a problem with the scan converter
T
T/F: A system which was working well now does not display clear images in the far field. This may be a problem with the transducer
T
T/F: Lateral resolution is also called azimuthal
T
T/F: Shadowing may result from high amounts of reflection of ultrasound energy
T
In which way is an annular phase array transducer different than a linear phased array transducer? A. the linear is steered mechanically B. The linear can have multiple focal zones C. The annular can create a sector shaped image D. The linear has higher PRF E. the annular is steered mechanically
The annular is steered mechanically
Power of sound has units of
Watts
What is not the responsibility of the sonographer? A. clean the filters B. adjust the recorder C. adjust converter matrix D. change the paper
adjust converter matrix
With good images on the display but not on the printer, one should
adjust the recorder
Sound is traveling from medium 1 to medium 2. Propagation speeds of M1 and M2 are 1,600 m/s and 1,500m/s. There is an oblique incidence.
angle of incidence= angle of reflection
To measure the US beam intensity, use a
calibrated hydrophone
Which of these cannot be performed by a sonographer? Adjust overall gain clean VCR recording heads clean pixels adjust TGC
clean pixels
The units of attenuation are ___ : this is a ___ scale A) mm/cm ; parametric B) dB/m ; multiplicative C) none ; relative D) dB ; logarithmic
dB, logarithmic
Under which of the following conditions is lateral resolution improved?
decreased beam diameter
What happens to venous blood flow to the heart during expiration?
decreased.
If the frame rate increases and the lines per frame is unchanged, what else must happen?
depth decreases
The doppler shift is a measure of:
difference between incident and reflected frequency
Which of these factors has the greatest influence on PRP? Display depth A. thickness of the PZT crystal B. attenuation of the sound beam impedance of the medium display's dynamic range
display depth
Post processing occurs when the image:
entered the A/D converter but before display
What increases patient exposure?
exam time
Propagation speed= _______ x wavelength
frequency
For soft tissue, the approximate attenuation coefficient in dB/cm is equal to 1/2 _____ in _____
frequency, MHz
The rayl is the unit of:
impedance
All of the following statements regarding in-vitro bioeffects are true except: A. in vitro bioeffects conclusions are clinically relevant B. in vitro bio effects are always real C. in vitro bioeffects are very important D. In vitro bioeffects may not be applicable to clinical settings
in vitro bioeffects are clinically relevant
A hydrophone is used to measure
intensity or frequency
Which of the following will result in the greatest number of shades of gray in a digital image? A. large pixels with many bits/pixels B. small pixels with few bits/pixels C. many TV lines over frame D. high contrast E. narrow dynamic range
large pixels with many bits/pixels
Which has the correct units? Frequency Speed Intensity Attenuation
mHz m/sec W/cm^2 dB
Images on videotape are stored using:
magnetism
The curie temperature has what effect
the ferroelectric material is depolarized
What information does doppler shift provide?
velocity
What are the units of intensity?
watts/cm2
_____ is the distance covered by one cycle
wavelength
Pre-processing occurs:
when the patient is scanned
