Physics 2 Final Exam Flashcards
What is the frequency of a transducer if the period is 25 million cycles/ sec?
25 MHz
Pg. 21
What are the ranges for audible, ultrasound, and infrasound?
Infrasound - less than 20Hz
Audible - 20Hz - 20 kHz
Ultrasound - greater than 20kHz
Pg. 22
What are the ultrasound parameters? Which are determined by only the sound source and which are determined by both the sound source and the medium?
Sound Source: Period Frequency Amplitude Power Intensity Pg.40 Pulse duration PRP PRF Duty Factor Pg 63
Sound Source & Medium: Wavelength Pg. 40 Spatial Pulse Length Pg. 63
If intensity remains the same, while power is doubled, what happens to the beam area?
Doubled
Pg 44
What are the acoustic variables?
Pressure (pascals)
Density (kg/cm^3)
Distance (cm,mm)
Pg 12
What would create the longest wavelength?
The lower the frequency, the longer the wavelength
pg. 34
What is the term used to describe from the start of a pulse to the end of a pulse?
Pulse duration
Pg 49
What scale do we use for decibels?
Logarithmic
Pg 77
What will intensity do if you have 3 dBs?
Intensity is doubled at 3dB
Pg 78
If initial intensity is less than the final intensity, then what will the gain in decibels be?
Positive, the beam’s intensity is increasing
pg. 79
Rayleigh scattering is related to ___.
Frequency^4
Soft tissue attenuation coefficient is directly related to ___.
Frequency
Attenuation coefficient= 0.5dB/cm/MHz
pg. 85
What are the different speeds and attenuation we will find in different mediums?
Medium, Attenuation, speed
water, extremely low, 1480m/s
blood/urine/biological fluids, low, 1560m/s
fat, low 1450m/s
soft tissue, intermediate 1540m/s
muscle, higher, 1600m/s
bong and lung, even higher, 3500m/s (bone) 500m/s (lung)
air, extremely high, 300m/s
pg. 86 and 37
If two PZT are made from the same material, the thicker crystal will make a pulsed transducer that is ___.
Lower frequency
pg. 127
What happens when we exceed the Curie point?
Depolarization
Pg 120
Which component of a transducer reduces ringing of a pulse?
Backing material
“Damping element”
Pg 115
Know all about crystals and what they may produce (thick/thin crystals, high/low speeds).
Materials which convert sound into electricity and vice versa
Names: Piezoelectric, ferroelectric, PZT, lead zirconate titanate, ceramic, active element, & crystal
High frequency transducer: thinner PZT with higher speeds
Low frequency transducer: thicker PZT with lower speeds
pg. 113 & 125)
What resolution is improved by damping material?
Axial
Pg 115
Longitudinal
pg. 126
The voltage of a pulsed transducer is 6 MHz, what will the frequency be?
Cannot be determined by electrical signal
pg. 126
Frequency is given for a continuous wave probe is 6 MHz, what is the operating frequency? (what is the relationship between these two)
Identical (6MHz)
pg. 127
What is the order of impedences from greatest to least? (matching layer, skin, gel, PZT)
PZT > matching layer > gel > skin
pg. 116
Which component of a transducer contains cork?
Acoustic insulator
Pg 115
What does the matching layer do?
Increases the percentage of transmitted sound between the active element and the skin; protects the active element
pg. 115-116
How are frequency and near zone length related?
Directly
Pg 135
Anatomy of a sound wave (5 questions)
- Focus/ focal point= where the beam is narrowest
- Near Zone/field, Fresnel Zone= distance from the transducer to the focus
- Near zone length/focal zone length/ focal depth= distance from the transducer face to the focus
- Far zone/ field, Fraunhoffer zone= region deeper than the focus, where the sound beam diverges
- Focal zone= region around the focus where the beam is relatively narrow, where the most accurate images come from
pg. 131
How is the focal length of a sound beam determined?
1) Transducer diameter
2) Frequency of sound
pg. 135
What is the spread of a sound beam in the far field?
Divergence
pg. 139
What will create the best lateral resolution based on frequency and diameter?
The largest diameter and highest frequency
pg. 153
LARRD (multiple questions)
Longitudinal Axial Range Radial Depth -parallel to beam's axis -best with less ringing and high frequency pg. 146
LATA (multiple questions)
Lateral Angular Transverse Azimuthal - perpendicular to beam's axis - best with decrease FOV and at focus pg. 153
What is lateral resolution?
the ability to distinguish 2 structures perpendicular to beam
pg. 151
Which intensity is most important when it comes to biological effects?
SPTA
pg. 74
Which intensity is considered the maximum?
Peak
Pg 69
What are the units for intensity?
W/cm^2
pg. 73
What are the six different kinds of intensity?
spatial peak average temporal pulsed pg 69 only found 5
What is an incident of a sound wave?
The angle at which the wave strikes the boundary.
Normal (PORNN) perpendicular orthogonal right 90
Oblique=anything other than 90degree
What is the difference between transmission, reflection, and incident intensity? (6 questions)
incident intensity= the sound wave’s intensity immediately before it strikes a boundary
reflected intensity= percentage of intensity that returns , after striking the boundary
transmitted intensity=the percentage of intensity that continues forward after the boundary
pg 92
What is the half value layer thickness?
the distance sound travels in a tissue that reduces te intensity of sound to 1/2 of its original value.
pg 87
What is the angle degree for normal incidence?
90
What is the intensity reflection coefficient? (3 questions)
the percentage of the intensity that bounces back when a sound beam strikes the boundary between 2 media.
in clinical imaging, very little of the sound wave’s intensity is reflected at the boundary between 2 soft tissues.
greater percentage of the wave is reflected when it strikes a boundary between soft tissue and bode or air.
pg 93
To have normal incidence, you have to have different what?
difference in acoustic impedance.
pg 88
Specular reflections arise from what?
The sound is reflected in only one direction in an organized manner.
When it strikes a smooth boundary.
pg 81
What is the term used to describe transmission with a bend?
refraction
pg 100
What can happen with both oblique incidence and different propagation speeds?
Refraction
pg 101
Snell’s Law describes what?
The physics of refraction
pg. 102
What is it called when two sound waves are traveling towards something and they both arrive at the same time?
Interference
Pg 18
Thumbs up and thumbs down rule (stiffness and density)
Stiffness directly related to speed
Density inversely related to speed
pg. 39
What is attenuation?
a decrease in intensity, power and amplitude as the sound travels through the medium
pg 80
Impedence is a characteristic of what?
Medium only
pg 88
What type of transducer and frequency do we use on different parts of the body?
Small parts: Linear, High frequency
Abdomen: Convex, Lower frequency
What is the ability to distinguish between two structures?
resolution
pg. 149
What is the best choice for attenuation coefficient in soft tissue?
one-half of the frequency
pg 85
Attenuation is determined by what two factors?
path length
frequency
pg 80
What is the term used to describe the redirection of sound in many directions?
Scattering
pg 82
What do we consider a rough boundary?
most interfaces in the body
pg. 82
What is time of flight?
the elapsed time from pulse creation to pulse reception
pg. 107
What is Q-factor?
Q-factor = main frequency/bandwidth
Imaging probes have a low-Q
pg. 119
All the different names used to describe time of flight
Go return time
pg. 107
What is the 13 microsecond rule?
When sound travels through soft tissue, for every 13 microseconds of go-return time, the object creating the reflection is 1 cm deeper
pg. 108
When you change your depth, what happens to PRP?
Doubles
Per Game Review
Shallow Depth = Short PRP
pg. 109
Axial resolution deals with structures that are located where on the sound beam?
Parallel
Per Game Review pg. 145
What happens to the numerical value of LARRD as frequency increases?
Decreases
Per Game Review pg. 148
If you are given a frequency, what will have the best axial resolution? # of cycles
High frequency
Fewer cycles per pulse
pg. 148
Why is it difficult to study biological effects in living tissue?
Absorption (biggest reason), scattering and reflection
pg. 170
What is the empirical approach?
Based on the acquisition and review of information from patients and animals exposed to ultrasound. Searches for a relationship between exposure and response
pg. 407
What is the difference between stable cavitation and transient cavitation?
Stable
oscillating bubble
microstreamng and shear stresses
lower MI
Transient (normal, inertial)
bursting bubble
shock waves and very high temperatures
higher MI
pg. 411
What is the primary investigative technique used in epidemiology?
Reviewing of the charts
Per Game Review
What is the most common intensity that is involved with tissue heating?
SPTA
pg. 74
How do we study biological effects of non-living things?
in vitro
pg. 405
Which will have the least amount of temperature elevation, focused or unfocused sound beams?
Focused sound beams
per Game Review
What should we do if we find a broken housing or a frayed wire on an ultrasound machine?
Do not use it
When is it okay to perform an ultrasound on a patient?
When the benefits outweigh the risks
pg. 405
What is the x-axis and y-axis on A, B, and M Mode?
A-mode: x=depth, y=amplitude z=none
B-mode: x=depth, y=none, z=amplitude
M-mode: x=time, y=depth, z=none
pg. 163
A Mode
Amplitude Mode appearing as a series of upward spikes (big city skyline)
pg. 159-160
B Mode
Brightness Mode appearing as a line of dots of varying brightness, first form of gray scale imaging
pg. 161
M Mode
Motion Mode appearing as a group of horizontal wavy lines (heart rate)
pg. 162
What must we have to have gray scale imaging?
scan converter
Per Game Review
What is the difference between pre-processing and post-processing?
Pre-processing is manipulation of image data before storage
Post-processing is manipulation of image data after stoarge
pg. 249
What is spatial compouding?
method of using sonographic information from several different imaging angles to produce 1 single image
pg. 254
What is fill-in interpolation?
method of constructing new simulated data points to fill in the gaps
pg. 257
What is persistence?
AKA temporal compounding or averaging
image processing technique that continues to display information from older images, which smooths the image
pg. 256
What is edge enhancement?
image processing method that makes pictures look sharper
pg. 255
What are the advantages of the PACS system?
virtually instant access to archived studies
no degradation of data
ability to electronically transmit images and reports to remote sites “store and forward”
pg. 259
When sending the signal from the transducer to the receiver, what form is the information in? (refer to the analog to digital diagram on pg. 247)
analog to digital form
pg. 247
What do contrast agents need to be?
Safe Metabolically inert Long lasting Strong reflector of ultrasound Small enough to pass through capillaries pg. 278
What is harmonic imaging? (convert harmonic frequency to fundamental frequency)
harmonic imaging is the creatioin of an image from sound reflections at twice the frequency of the transmitted sound
pg. 269
What is the difference between pulsatile and phasic flow?
Pulsatile flow occurs when blood moves with a variable velocity (arterial)
Phasic flow occurs when blood moves with a variable velocity (venous)
pg. 286
What are the different types of laminar flow?
Plug flow: all layers and blood cells travel at the same velocity
Parabolic flow: flow has bullet-shaped profile
pg. 287.vr t
What is the Reynold’s number for turbulent flow?
greater than 2000
pg. 288
What are the effects of a stenosis?
change in flow direction increased velocity as vessel narrows turbulence downstream from the stenosis pressure gradient across the stenosis loss of pulsatility pg. 292
What is the hyrdrostatic pressure in different parts of the body while standing and laying supine?
Standing: Finger in air: -50 mmHg Heart: 0 mmHg Waist: 50 mmHg Knee: 75 mmHg Ankle: 100 mmHg pg. 298
Supine:
0 mmHg everywhere
pg. 297
What is coaptation?
Compressing a vessel
Per Beth
What happens to the pressure in different parts of the body while inhaling and exhaling?
Inspiration: Diaphragm moves down Thoracic pressure decreases Abdominal pressure increases Venous return to heart increases Venous flow in legs decreases
Expiration: Diaphragm moves up Thoracic pressure increases Abdominal pressure decreases Venous return to heart decreases Venous flow in legs increases
pg. 301
What is the Doppler shift called when the sound source and the receiver are moving farther apart?
Negative Doppler shift
pg. 305
What is the typical range for a Doppler shift?
20 Hz - 20,000 Hz
pg. 304
What is the phenomenon called when high velocities appear negative?
Aliasing
pg. 315
What are five ways that we can eliminate aliasing? Which is for appearance only?
- Adjust scale to its maximum
- Select a new ultrasonic view with a shallower sample volume
- Select a lower frequency transducer
- Use baseline shift - for appearance only
- Use continuous wave Doppler
pg. 319 and 322
What are the x-axis and y-axis for Doppler on a spectral analysis?
x-axis: time
y-axis: velocity
pg. 307
Doppler shift is inversely related to ___.
Propagation speed
pg. 306
What is unidirection Doppler?
Either flow away or towards the transducer?
pg. 311
If red blood cells are traveling toward the transducer, what kind of Doppler shift is this?
Positive Doppler shift
pg. 304
What is the primary advantage of pulsed Doppler?
Being able to see the exact location where the velocity is being measured
called range resolution, range specificity, or freedom from range ambiguity artifact
pg. 314
What is the primary advantage of continuous wave Doppler?
accurately measures very high velocities
pg. 312
What is the disadvantage of using color Doppler?
aliasing
pg. 325
The area of interrogation on Doppler is called what?
sample volume
pg. 339
What tool has increased sensitivity to low flow states?
Power Doppler
pg. 333
Continuous wave
pg. 313
Know all describing factors of an ultrasound image
Hyperechoic Hypoechoic Anechoic Isoechoic Homogeneous Heterogeneous pg. 356
Why do we have artifacts?
error in imaging from violation of assumptions equipment malfunction/poor design physics of ultrasound operator error pg. 355
Which artifact has equally spaced parallel lines?
Reverberation
pg. 357
Which artifact is unrelated to the dimensions of ultrasound? A. Lateral resolution B. Depth resolution C. Slice Thickness D. Refraction
Refraction
pg. 378
What artifact produces an incorrect number of reflectors? A. Propagation speed error B. Multipath C. Enhancement D. Side Lobes
Side lobe artifact
pg. 377
What is mirror image?
When sound reflects off a strong reflector and is redirected toward a second structure
appears deeper than true reflector on a straight line
pg. 363
What kind of transducer do side lobes and grating lobes come from?
Side lobes created by mechanical probes
Grating lobes created by array transducers
pg. 367
What are axial and lateral resolution artifacts?
Lateral occurs when a pair of side-by-side reflectors are closer than the width of the sound beam and they appear as 1.
Axial occurs when a long pulse strikes 2 closely spaced structures where one is in front of the other they appear as 1.
pg. 370
Where does edge shadow come from?
curved reflector
pg. 360
What is focal banding?
AKA focal enhancement
Hyperechoic side-to-side region from increased intensity at the focus
pg. 362
What is enhancement?
hyperechoic region below structure from the result of too little attenuation
pg. 361
What are speed errors?
When sound wave propagates through a medium at a speed other than that of soft tissue
pg. 364
What is speckle?
Noise resulting from the constructive and destructive interference of small sound wavelets
pg. 374
What is range ambiguity artifact?
Occurs when a reflecting structure is located deeper than the imaging depth of the image; reflector is located shallower on the image
pg. 373
What is cross talk?
mirror image artifact that appears on a spectral Doppler display
pg. 363
What is a tissue equivalent phantom? (2 questions)
Used to evaluate characteristics such as gray scale and tissue texture, and multi-focus and adjustable-focus phased array transducers
Gray scale is evaluated
pg. 382
What are the rules for informed consent?
Patient must be competent and consent must be voluntary
the goal is to allow patients to be knowledgeable of their health care
pg. 393
A perfect technique for example, MRI or Angio, that would deem 100% accurate with ultrasound is called what?
Gold Standard
Per Beth
What are we testing with quality assurance?
Validates the consistency of ultrasound images and the accuracy of measurement devices
pg. 379
According to the AIUM and FDA bioeffects intensity limits, what is the difference between focused and unfocused sound beams?
Unfocused beam is more likely to cause a rise in temperature because the beam spreads over a broad area
pg. 549
What is the first thing you should do when entering a patient’s room?
greet patient and wash your hands???
What kind of transducer, if it’s crystals get destroyed, will have the whole image compromised?
mechanical
pg 167
What transducer is focused in all planes and at all depths?
Annular Phased Array
Per Game Review
What is the advantage of a 1.5 dimensional array transducer? What type of dimension are we looking at?
3D/4D. Has the advantage of Elevational Resolution.
pg 188
What is the image shape for a vector array?
Trapezoidal
What type of transducer has elements that are in a straight line?
Linear
What transducer has circular rings and a common center?
Annular
pg 179
Which transducer has it’s elements in a bow shape?
Curved
What does phased array mean?
adjustable
pg 170
Dropout of an image from top to bottom is produced by what type of transducer?
Linear Sequential Array
Convex/curve
pg 180
Dropout of an image from side to side is produced by what type of transducer?
Annular phased array
pg 179
Know all about mechanical probes
single crystal sector shaped image mechanical steering fixed focus pg 167
What is dynamic aperture?
the “listening hole” it is a technique used to make a sound beam narrow over a greater range of depths.
pg 194
The ability to accurately locate a moving structure at any point or time is what?
Temporal Resolution
Per Game Review
What will degrade temporal resolution?
low frame rates
pg 372
If we double our depth of view, what happens to the frame rate?
1/2
Per Game Review
What degrades temporal resolution?
low frame rates
pg 372
With a given Hz, how long will it take to make a single frame?
reciprocals, so for example given frequency is 30 Hz, it will take 1/30 sec to create a frame
pg. 214
Lateral resolution will improve with ___.
High frequency
Large Diameter
Per Game Review
The depth of a scan is 15 cm, there are 100 lines in the image. What are the number of pulses that make up the scan?
100 pulses
pg. 213
What is consistent with increased or improved spatial resolution?
high line density
pg 372
Which ultrasound system component organizes and times the functions?
Master Synchronizer
Per Game Review
What component of an ultrasound system creates the electrical signal that excites the PZT?
Pulser
Per Game Review
Know the anatomic areas of the TGC curve
near gain delay slope knee far gain pg 228
On a TGC curve, what location does attenuation take place?
Slope
What creates the firing pattern for a phased array transducer?
Beam Former
Per Game Review
Of receiver functions, which treats signals differently depending on depth?
Compensation
Per Game Review
If an image is too dark or too bright the sonographer should decide between output power and receiver gain keeping what in mind?
ALARA
Per Game Review
Which receiver function affects only the weak signals, leaving the strong signals unchanged?
Reject
Per Game Review
If an image is dark in the near field but you can still see what’s in the far field, what should be adjusted?
TGC
Per Game Review
Which function will affect the strength of every pulse transmitted into the body?
Output Power
Per Game Review
Amplification
Pg. 224
What is signal to noise ratio?
a comparison of the meaningful information (signal) in an image, compared to the amount of contamination (noise)
pg 219
What are the describing words for intensity?
Bigness or spatial peak average temporal pulsed pg 69
What is the dominating contributor to attenuation?
Absorption
pg84
How do you calculate attenuation?
total attenuation= attenuation coefficient x distance pg 85
When can a patient revoke their consent?
Any time
pg. 393
