# Shared Flashcard Set

## Details

Physics Final Review
Questions from test
225
Physics
Not Applicable
11/29/2010

Term
 Put these metric prefixes in order from largest to smallest:   nano, mega, centi, milli, kilo, micro     *know how to convert these also*
Definition
 mega - 106 - million  (M) kilo - 103 - thousand  (k) centi - 10-2 - hundredth  (c) milli - 10-3 - thousandth  (m) micro - 10-6 - millionth  (µ) nano - 10-9 - billionth  (n)
Term
 Name an appropriate unit for area.
Definition
 cm2,  ft2
Term
 Sound is a ___________ wave in which particles in the medium move.
Definition
 mechanical
Term
 Can sound travel in a vacuum?
Definition
 NO, it must have a medium
Term
 In a sound wave, molecules are alternately squeezed together and then stretched apart, or _________ and then ___________.
Definition
 compressed, rarefied
Term
 Are sound waves transverse or longitudinal waves?
Definition
 Longitudinal waves
Term
 Name the 3 acoustic variables that identify sound waves.
Definition
 pressure density distance
Term
 Define Pressure.   Units?
Definition
 concentration of force in an area   units: pascals (Pa)
Term
 Define density.   Units?
Definition
 concentration of mass in a volume.   units: kg/cm3
Term
 Define distance.   Units?
Definition
 Measure of particle motion.   Units: cm, mm, feet, etc.
Term
 List the 7 acoustic parameters used to describe the wave's features.
Definition
 Period Frequency Amplitude Power Intensity Wavelength Propagation speed
Term
 Which direction do particles move in a transverse wave?
Definition
 perpindicular to the direction that the wave propagates
Term
 What direction do particles in a longitudinal wave move?
Definition
 parallel, or in the same direction that the wave propagates
Term
 When is a wave considered to be "in-phase"?
Definition
 When their peaks and troughs occur at the same time and the same location.
Term
 When is a wave considered to be "out-of-phase"?
Definition
 When their peaks and troughs occur at different times.
Term
 Define interference.
Definition
 When multiple waves arrive at the same location at exactly the same time.
Term
 When does constructive interference happen?
Definition
 When a pair of "in-phase" waves combine to form 1 wave which has greater amplitude than either of the original waves.
Term
 When does destructive interference happen?
Definition
 When a pair of "out-of-phase" waves combine and result in the formation of 1 wave which has smaller amplitude than the original waves.
Term
 Destructive interference takes place with _______________ waves.
Definition
 Out-of-phase
Term
 Constructive interference takes place with __________ waves.
Definition
 In-phase
Term
 What happens when waves of different frequencies interfere?
Definition
 Both constructive and destructive interference occur     *see Fig. 2.7 pg. 15*
Term
 Define period.   Units?
Definition
 The time from the start of one cycle to the start of the next cycle.   Units: seconds (s), milliseconds (ms), hours, other units of time.
Term
 What determines period?
Definition
 sound source (txr) only
Term
 Can the sonographer adjust the period?
Definition
 No.
Term
 Define frequency.   Units?
Definition
 The number of cycles that occur in one second.   Units: hertz (Hz) "per second"
Term
 What is the typical frequency of an ultrasound transducer?
Definition
 2 MHz to 10 MHz
Term
 What determines frequency of a sound wave?
Definition
 sound source only
Term
 Is the frequency of a transducer adjustable by the sonographer?
Definition
 No.
Term
 What is ultrasonic (ultrasound) frequency?
Definition
 greater than 20kHz or 20,000 Hz
Term
 What is the frequency of audible sound?
Definition
 between 20 Hz and 20,000 Hz
Term
 What is the frequency of infrasound?
Definition
 less that 20 Hz
Term
 Frequency affects _______ and image _________.
Definition
 penetration, quality
Term
 Period and frequency are _________ related to each other.
Definition
 inversely   *as frequency increases, period decreases *as frequency decreases, period increases   -also they are reciprocals of each other period x frequency = 1
Term
 Name the 3 "bigness" parameters.
Definition
 amplitude power intensity
Term
 Define amplitude.   Units?
Definition
 The difference between the maximum value and the average value of a wave.   Units:decibels (dB)
Term
 What is the typical value of amplitude in clinical imaging?
Definition
 1 MPa to 3 MPa (million pascals)
Term
 Amplitude is determined by
Definition
 sound source (txr) initially....then medium because it decrease as it propagates through the body
Term
 Is the amplitude adjustable by the sonographer?
Definition
 Yes, but it is not recommended.
Term
 How is amplitude measured?
Definition
 from the baseline to the maximum, or baseline to minimum
Term
 Define Peak-to-peak amplitude
Definition
 the difference between maximum and minimum values of an acoustic variable.   *twice the value of amplitude
Term
 Define power.   units?
Definition
 the rate of energy transfer or the rate at which work is performed.   Units: watts
Term
 How are amplitude and power related?
Definition
 When power increases, so does amplitude. When power decreases, so does amplitude.   power ∞ amplitude2   *(∞ = proportional, I couldn't find the real sign on here)
Term
 A sonographer increases the amplitude of a wave by a factor of 3. How has the power changed?
Definition
 Power is increase by 9     *power ∞ amplitude2, therefore 3x3=9*
Term
 If a sonographer decreases the amplitude of a wave to 1/2 of its original value, how has the power changed?
Definition
 Power is decrease by 1/4 or 25% of its original value.     *power ∞ amplitude2, therefore 1/2 x 1/2 = 1/4*
Term
 Define intensity.   Units?
Definition
 The concentration of energy in a sound beam.   Units: W/cm2
Term
 What is the formula to calculate intensity?
Definition
 Intensity (W/cm2) = power(w) / area (cm2)
Term
 What is the relationship between intensity and power?
Definition
 intensity is propertional to power (intensity ∞ power)   *if a waves power is doubled, intensity is doubled
Term
 What is the relationship between intensity and amplitude?
Definition
 intensity ∞ amplitude2   *if a waves amplitud is doubled, the intensity is increased 4 times its original value
Term
 Define Wavelength.   Units?
Definition
 The distance or length of one complete cycle.   Units: mm, meters
Term
 What determines wavelength?
Definition
 sound source AND medium   *only parameter determined by both*
Term
 How are wavelength and frequency related?
Definition
 Inversely   *as frequency increases, wavelength decreases *the lower the frequency the shorter the wavelength
Term
 In soft tissue, sound with a frequency of 1 MHz has a wavelength of ______.
Definition
 1.54 mm
Term
 In soft tissue, sound with a frequency of 2 MHz has a wavelength of ________.
Definition
 .77 mm
Term
 What is the formula to find the wavelength of a sound wave in soft tissue?
Definition
 wavelength (mm) = 1.54mm / frequency (MHz)
Term
 Shorter __________ sound usually produces higher quality images with greater detail.
Definition
 wavelength
Term
 Should sonographers use high or low frequency transducers?
Definition
 High frequency because high frequency produces shorter wavelength, superior quality
Term
 Define propagation speed.   Units?
Definition
 The distance that a sound wave travels through a medium in 1 second.   Units: mm/µs
Term
 What determines speed in a sound wave?
Definition
 Only the medium it is traveling through.
Term
 What is the speed of sound in soft tissue?
Definition
 1540 m/s (1.54 mm/μs, or 1.54 km/s)
Term
 What is the speed of sound in lung tissue?
Definition
 500 m/s
Term
 What is the speed of sound in fat?
Definition
 1450 m/s
Term
 What is the speed of sound in liver?
Definition
 1560 m/s
Term
 What is the speed of sound in bone?
Definition
 3500 m/s
Term
 What is the speed of sound in air?
Definition
 330 m/s
Term
 What is the speed of sound in water?
Definition
 1480 m/s
Term
 Put these in order of speed from slowest to fastest.   lung, soft tissue, bone, fat, air
Definition
 air, lung, fat, soft tissue, bone
Term
 What two characteristics of a medium affect the speed of sound?
Definition
 stiffness and density
Term
 Using Edelman's "rule of thumb", how are stiffness and speed and density and speed related?
Definition
 Stiffness and Speed are directly related, if one goes up so does the other.   Density and Speed are inversely related, if one goes up the other goes down
Term
 What other words can be used to describe stiffness?
Definition
 elasticity or compressability   **note: these are opposite of stiff, they mean non-stiff   **bulk modulus means stiff
Term
 The effects of tissue on sound waves are called _____?
Definition
 Acoustic propagation properties
Term
 What are the 5 additional parameters are used to describe pulsed sound waves?
Definition
 pulse duration pulse repitition period pulse repitition frequency duty factor spatial pulse length
Term
 Does imaging use continuous or pulsed ultrasound to create images?
Definition
 pulsed
Term
 A pulse of ultrasound is a collection of ______ that travel together and moves as a single unit.
Definition
 cycles
Term
 What are the 2 components of pulsed ultrasound?
Definition
 transmit, talking, or "on" time   receive, listening, or "off" time
Term
 Define pulse duration.   Units?
Definition
 The actual time from the start of a pulse to the end of that pulse. (only the "on" time)   Units: time (seconds, ms, μs)
Term
 Pulse duration is determined by the _________ only.
Definition
 sound source
Term
 What characteristics create a long pulse duration?
Definition
 many cycles in the pulse, or individual cycles with long periods
Term
 What characteristics will create a short pulse duration?
Definition
 few cycles in the pulse, or individual cycles with short periods
Term
 In clinical imaging, how many cycles does a pulse typically contain?
Definition
 2 - 4 cycles
Term
 Define spatial pulse length.   Units?
Definition
 the distance that a pulse occupies in space from the start to the end   Units: mm, m, other units of distance
Term
 Spatial pulse length is determined by
Definition
 both the source and the medium
Term
 What type of pulse is more desireable in diagnostic imaging?
Definition
 Shorter duration pulses are desireable because they create images of greater accuracy.
Term
 Define pulse repitition period.   Units?
Definition
 the time from the start of one pulse to the start of the next pulse. (includes one "on" time and one "off" time)   units of time: seconds, ms
Term
 How can a sonographer change the pulse repitition period?
Definition
 adjust the depth of view   **shallow depths, short pulse repitition period **deep depths, longer prp
Term
 Pulse repitition period and imaging depth are _________ related.
Definition
 directly.   **as depth increases, prp increases (listening time and talking time lengthen) **as depth decrease, prp decreases (listening time and talking time shorten) (see pg. 53 for images)
Term
 Define pulse repitition frequency.   Units?
Definition
 the number of pulse that an ultrasound system transmits into the body each second.   Units: Hz
Term
 Pulse repitition frequency and depth of view are ________ related.
Definition
 inversely   *as depth increases, PRF decreases *as depth decreases, PRF increases
Term
 An ultrasound machine is imaging to a depth of 2 cm. Would the pulse repetition frequency be described as high or low?
Definition
 High, with shallow depth the system only waits a short time before it creates a new pulse.
Term
 Pulse repetition period (PRP) and pulse repetition frequency (PRF) are ________ related to each other.
Definition
 inversely   *also they are reciprocals PRF x PRP = 1
Term
 Which of these four values for pulse repetition frequency would have the longest pulse repition period?   A. 2 kHz B. 4,000 Hz C. 6 Hz D. 1 kHz
Definition
 C. 6 Hz
Term
 Define Duty factor.     units?
Definition
 the percentage or fraction of time that the system is transmitting a pulse.   Units: NONE (percentage)
Term
 What is the typical value of duty factor in imaging?
Definition
 .1 - 1% (.001 - .01)   *very little talking, lots of listening
Term
 How can the sonographer change the duty factor?
Definition
Term
 Duty factor and imaging depth are _________ related.
Definition
 inversely   *duty factor is higher when imaging at shallow depths
Term
 What is the maximum value for duty factor and how is it achieved?
Definition
 1, or 100% This value is only achieved with continuous wave sound
Term
 What is the minimum value for duty factor?
Definition
 0% Exists only when the transducer is silent (machine turned off)
Term
 Shallow imaging creates _____ listening time, ________PRP, _______ PRF, and _______ duty factor.
Definition
 less listening time shorter PRP higher PRF higher duty factor
Term
 Deeper imaging creates ________ listening, ________ PRP, _______ PRF, and _______ duty factor.
Definition
 more listening longer PRP lower PRF lower duty factor
Term
 What are the five key words related to reporting intensities of pulsed waves?
Definition
 Spatial (refers to distance or space) Peak (the max value) Average Temporal (all time, transmit and recieve) Pulsed (only the transmit time)
Term
 Does an ultrasound beam have the same intensity at different locations?
Definition
 No.
Term
 SPTA is important regarding _______ ____________.
Definition
 thermal bio-effects
Term
 All intensities have units of ________.     * #4 of the "Ten Commandments" of Intensity pg. 72*
Definition
 watts/cm2
Term
 Rank these intensities from largest to smallest: SPTP, SATP, SPTA, SATA, SPPA, SAPA
Definition
 SPTP > SPPA > SPTA> SATP > SAPA > SATA   hints: *spatial peaks come before averages *I'd rather be a PA than a TA, and you have to have TP!
Term
 What is logarithm, or log?
Definition
 The number of times that 10 has to be multiplied to create the original number.
Term
 What is the log of 100?
Definition
 2
Term
 What is the log of 1,000,000?
Definition
 6     *count the zeros*
Term
 Decibel (dB) notation is _________.
Definition
 logarithmic
Term
 Decibels report _______ changes, but do not give you an absolute value.
Definition
 relative
Term
 How many intensitys are required to use decibels?
Definition
 2
Term
 Decibels are a ______.   The ________ level is divided by the ________ level.
Definition
 ratio.   actual / starting
Term
 Describe the 3 decibel rule for positive numbers.
Definition
 When a wave's intensity doubles, the relative change is 3 dB.   *3 dB = 2 times bigger *6 dB = 4 times bigger *9 dB = 6 times bigger
Term
 A component of the ultrasound system increases power from 5 to 10 watts. How is this expressed in decibels?
Definition
 3 dB, power doubled
Term
 A wave's initial intensity is 2 watts/cm2. There is an increase of 9 dB. What is the final intensity?
Definition
 16 watts/cm2
Term
 When the intensity increases 10-fold, the relative change is ______.
Definition
 10 dB   *10 dB = 10 times bigger *20 dB = 100 times bigger *30 dB = 1000 times bigger
Term
 When the intensity of of a wave is reduced to 1/2 its original value, the relative change is ______.
Definition
 -3 dB   *-3 dB = 1/2 of original strength *-6 dB = 1/4 of original strength *-9 dB = 1/6 of original strength
Term
 When the intensity is decrease by 1/10 its original value, the relative change is  ______.
Definition
 -10 dB     *-10 dB = 1/10 of original strength *-20 dB = 1/100 of original strength *-30 dB = 1/1000 of original strength
Term
 The acoustic power on the ultrasound machine indicates -6dB. The system is pulsing at _____ of its original power.
Definition
 1/4 or 25%
Term
 What 3 processes contribute to attenuation?
Definition
 reflection scattering absorption
Term
 high frequency = ________ attenuation = ______ penetration
Definition
 high frequency = greater attenuation = less penetration
Term
 Define reflection.
Definition
 sound energy hits something and some of the sound comes back
Term
 Define absorption.
Definition
 sound energy is converted into heat
Term
 Define scattering.
Definition
 the random redirection of sound in many directions
Term
 Put these attenuators in order from the biggest attenuator to the smallest:   water, bone, soft tissue, air, lung
Definition
 air bone lung soft tissue water
Term
 What does not go back to the transducer?   A. scattering B. absorption C. reflection
Definition
 B. absorption
Term
 Diffuse Reflection "backscatter" "non-specular"
Definition
 sound returning back to the transducer in a disorganized fashion due to rough boundaries   *only a portion returns to the txr
Term
 Define Rayleigh scattering.
Definition
 the sound energy is diverted in all directions in an organized fashion   *some sound energy returns to txr
Term
 What is the only coefficient/ factor with units?
Definition
 Attenuation coefficient
Term
 formula for total attenuation
Definition
 total attenuation (dB)= attenuation coeff (dB/cm) x distance (cm)
Term
 Attenuation coefficient is ______ of the frequency.
Definition
 1/2   atten. coeff. (db/cm) = frequency (MHz)/ 2
Term
 In soft tissue, the attenuation coefficient is approximately ______
Definition
 0.5 dB/cm MHz
Term
 What is a high attenuator?
Definition
 air
Term
 In soft tissue, a 4 MHz ultrasonic wave starts with an intensity of 8 watts/cm2. What is the total attenuation after traveling a depth of 10cm?
Definition
 total attenuation = 20 dB   *you must find attenuation coefficient first, then x distance
Term
 How do you calculate impedence?
Definition
 impendence (rayles) (z) = density (kg/m3) x speed (m/s)
Term
 Define Impedence.
Definition
 the acoustic resistance to sound traveling in a medium   *We depend on the differences in impedences to produce a pictue.
Term
 What is the typical value of impedence?
Definition
 1,250,000 - 1,750,000 rayls or 1.25 - 1.75 Mrayls
Term
 As the path length increases, the attenuatin of ultrasound in soft tissue _________.
Definition
 increases
Term
 Impedence is a characteristic of __________.
Definition
 only the medium
Term
 Normal incidence is also called...
Definition
 perpendicular orthogonal right angle ninety degress normal   *PORNN
Term
 What are the 3 types of angles?
Definition
 Acute - less than 90 degrees Right - exactly 90 degrees Obtuse - greater than 90 degrees
Term
 A sound wave with intensity of 50 W/cm2 strikes a boundary and is totally reflected. What is the intensity relection coefficient?   A. 50 W/cm2 B. 25 W/cm2 C. 0 W/cm2 D. 100% E. 0
Definition
 D. 100%     *IRC is the intensity that bounces back when a beam strikes the boundary between 2 media
Term
 A sound wave with intensity of 50 W/cm2 strikes a boundary and is totally reflected. What is the reflected intensity?   A. 50 W/cm2 B. 25 W/cm2 C. 0 W/cm2 D. 100% E. 0
Definition
 A. 50 W/cm2
Term
 IRC + ITC = ?
Definition
 100%   *conservation of energy at a boundary   IRC = intensity bounced back ITC = intensity transmitted
Term
 Only ___% or less of the incident sound beam is relected at a boundary between 2 soft tissue media.
Definition
 1%   * 99% or more of incident energy is transmitted
Term
 At an air - tissue interface, ____% of incident energy is reflected.
Definition
 99%
Term
 At a bone - tissue interface, ___% of the incident energy is reflected.
Definition
 50%
Term
 Which of the following terms do not belong with the others?   A. orthogonal B. oblique C. normal D. perpendicular
Definition
 B. Oblique   *remember PORNN
Term
 With normal incidence, reflections occur only when the impedences of the two media at the interface are _________.
Definition
 different   *high impedence = high reflection similar impedence = little reflection no impedence = no reflection
Term
 When a beam strikes a boundary obliquely, reflection may or may not occur. If it does occur, reflection angle will ______ the incident angle.
Definition
 equal
Term
 What is Snell's Law?
Definition
 sin (transmission angle) = speed of medium 2 sin(incident angle)           speed of medium 1       *transmission angle > incident angle when speed of medium 2 > speed of medium 1 (bends downward)   *transmission angle < incident angle when speed of medium 2 < speed of medium 1 (bends upward)
Term
 What 2 conditions are needed for refraction?
Definition
 oblique angle different propagation speeds
Term
 How is refraction related to impedence?
Definition
 unrelated!
Term
 The impedence of medium 1 is 8 rayls and the propagation speed is 1450 m/s. The impedence of medium 2 is 6 rayls and the propagation speed is 1.8dd km/s. A sound beam strikes the boundary between the media and is both partially transmitted and reflected. The angle of the incident beam is 30 degrees. What is the reflection angle?
Definition
 30 degrees   *angle of reflection = angle of incidence, everything else is distractors!
Term
 Time of flight is ________
Definition
 measured
Term
 Time of flight and distance are __________ related.
Definition
 directly   *increase distance = increase time of flight (increased by a factor of 2) *decrease distance = decrease time of flight
Term
 Every ___ μs of go-return time means the reflector is __ cm deep.
Definition
 13, 1cm   *total distance traveled = 2cm
Term
 A sound wave is created by a transducer, reflects off an object, and returns to the transducer. The depth of the reflector is 10 cm in soft tissue. What is the go-return time?   A. 13 μs B. 1.3 μs C. 65 μs D. 130 μs
Definition
 D. 130 μs   *time of flight = depth x 13 μs
Term
 What is the piezoelectric effect?
Definition
 describes the property of certain materials to create a voltage when mechanically deformed (squeezed)
Term
 Name some man-made (ferroelectric) materials used in clinical transducers.
Definition
Term
 The PZT is also referred to as:
Definition
 ceramic, active element or crystal
Term
 What is the Curie point?
Definition
 approx. 360 degrees   * if crystal is heated above this point, it will lose piezoelectric properties and be "depolarized" FOREVER
Term
 What is the proper sterile technique to use with ultrasound transducers?
Definition
 use sterile probe cover
Term
 Define disinfection
Definition
 refers to the application of a chemical agent to reduce or eliminate infectious organisms on the txr.   *our txrs are disinfected using t-spray or cidex
Term
 What protects the internal components of the txr from damage and insulates the patient from electrical shock?
Definition
 case
Term
 The matching layer is ______ thick.
Definition
 1/4 wavelength
Term
 Know image of basic transducer construction. Pg 118   including: case, wire, matching layer, backing material
Definition
Term
 The matching layer was created because...
Definition
 the impedence of the PZT is about 20 times greater than the impedence of the skin so the intensity would be reflected back instead of enter the body.   matching layer decreases reflections at the skin's boundary
Term
 Put these in decreasing order of impedence:   matching layer, PZT, skin, gel
Definition
 PZT > matching layer > gel > skin
Term
 What is the damping element made of?
Definition
 epoxy resin impregnanted with tungsten
Term
 What are the advantages of backing material?
Definition
 Shortens SPL, pulse duration (limits ringing) increases picture accuracy improves axial resolution (LARRD)
Term
 What are the consequences of using backing material?
Definition
 decreased sensitivity wide bandwidth low "Q" factor
Term
 What is bandwidth?
Definition
 the range, or difference, between the highest and the lowest frequencies in the pulse.   bandwidth (Hz) = max. frequency - min frequency
Term
 Transducers used in therapeutic ultrasound do not contain _________ _______.
Definition
 backing material   *they are high-Q and narrow bandwidth
Term
 The number of _______ in a pulse of an imaging txr is the same as the quality factor.
Definition
 cycles
Term
 Q-factor is ________ related to bandwidth.
Definition
 inversely   *wide bandwidth = low Q-factor
Term
 Pulse duration is ________ related to bandwidth.
Definition
 inversely
Term
 In continuous wave transducers, the frequency of the voltage applied to the crystal _______ the sound wave's frequency.
Definition
 equals   *electrical frequency = acoustic frequency
Term
 What characteristics of the active element determine the frequency of sound created by a pulse wave txr?
Definition
 1. speed of sound in the PZT 2. thickness of the PZT   *high speed = high frequency *thich crystal = low frequency (think of thick guitar string = low tone)
Term
 Imaging transducers are _____-Q
Definition
 low
Term
 A pulse with a long pulse duration is going to have a ________ bandwidth.
Definition
 narrow
Term
 The damping material improves the _________ resolution.
Definition
 LARRD
Term
 The impedence of a transducer active element is 1,900,0000 Rayls, and the impedence of the skin is 1,400,000 Rayls. What is an acceptable impedence for the matching layer?   A. 1,200,000 Rayls B. 1,400,000 Rayls C. 1,726,000 Rayls D. 1,950,000 Rayls
Definition
 C. The impedence of the matching layer should be between that of the PZT and the skin.
Term
 The sound beam used for board exams is created by a single, disc-shaped, ___________ PZT crystal operating on a continuous wave mode.
Definition
 un-focused
Term
 The near zone is the ________ from the transducer to the focus.   Also called?
Definition
 region   also called: Fresnel zone, near field
Term
 The far zone is the region starting at the focus and extending deeper. It is also referred to as ___________.
Definition
 Fraunhofer zone, or far field
Term
 Define focal zone.
Definition
 the region or zone surrounding the focus, where the beam is narrow and image is relatively good
Term
 At the end of one near zone length, the beam diameter is ______ of the PZT diameter.
Definition
 1/2
Term
 At 2 near zone lengths, the beam diameter is ________ the original diameter.
Definition
 equal to
Term
 What 2 factors determine focal depth?
Definition
 txr diameter frequency of sound wave   *bigger diameter = deeper focus *higher frequency = deeper focus (neglecting attenuation)
Term
 What 2 factors determine sound beam divergence?
Definition
 transducer diameter frequency of sound   *larger diameter = less divergence in far field *higher frequency = less divergence in far field
Term
 Describe Huygen's Principle
Definition
 One large PZT is made up of teeny, tiny, multiple crystals Each tiny crystal produces a diffraction (v-shaped) pattern Hourglass shaped beam results from interference of waves
Term
 V-shaped waves are also referred to as:
Definition
 spherical waves, diffraction patterns, or Huygen's wavelets
Term
 Axial Resolution is also called
Definition
 LARRD Resolution   L- longitudinal A- axial R- range R- radial D- depth
Term
 Do we want a large or small axial resolution?
Definition
 as small as possible
Term
 Anything at or above the numerical value of LARRD resolution will be displays as...
Definition
 2 separate structures
Term
 If structures are 2 mm apart and longitudinal resolution is 4 mm, will they be displayed as 2 separate structures?
Definition
 No, the structures have to be at or above the numerical value of LARRD
Term
 Great axial resolution is associated with ______ spatial pulse length ______ pulse duration ______ frequencies _________ wavelength ________ cycles _______ ringing _________ numerical value
Definition
 shorter spatial pulse length shorter pulse duration high frequency short wavelength few cycles less ringing  lower numerical value
Term
 The ability to distinguish 2 structures lying closely together front-to-back or parallel to the sound beam is called ________.
Definition
 LARRD
Term
 Which of the following transducers has the poorest axial resolution?   A. 1.7 MHz and 4 cycles/pulse B. 2.6 MHz and 3 cycles/pulse C. 1.7 MHz and 5 cycles/pulse D. 2.6 MHz and 2 cycles/pulse
Definition
 C.
Term
 Which of the following has the best axial resolution?   A. 1.7 MHz and 4 cycles/pulse B. 2.6 MHz and 3 cycles/pulse C. 1.7 MHz and 5 cycles/pulse D. 2.6 MHz and 2 cycles/pulse
Definition
 D.
Term
 Define lateral resolution
Definition
 the ability to distinctly indentify two structures that are very close together when the structures are side by side, or perpendicular to the sounds main axis
Term
 What is the mnemonic for lateral resolution?
Definition
 LATA   Lateral Angular Transverse Azimuthal
Term
 Lateral resolution is best at the _______.
Definition
 focus, where the beam is narrowest
Term
 Axial resolution is better than lateral resolution. Why?
Definition
 because ultrasound pulses are shorter than they are wide
Term
 What is the relationship between lateral resolution and beam diameter?
Definition
 they are equal
Term
 Lateral resolution is also affected by ________.
Definition
 depth
Term
 What are the 3 methods of focusing?
Definition
 1. external focusing - lens 2. internal focusing - with a curved active element 3. phased array focusing - with the electronics of the system
Term
 Can the focal depth or focus be changed with external and internal focusing?
Definition
 No. *also called fixed focusing (aka mechanical coventional)
Term
 Single crystal transducers are always ________ focus.
Definition
 fixed
Term
 What are the effects of focusing?
Definition
 -a narrow "waist" in the beam - focal depth is shallower - beam diameter in the far zone increases -focal zone is smaller -improves lateral resolution
Term
 The frequency of a continuous wave is determined by...
Definition
 electrical frequency from system
Term
 The frequency of a pulse wave is determined by...
Definition
 thickness of PZT and speed of sound in PZT
Term
 Focal length is determined by...
Definition
 diameter of PZT and frequency of sound
Term
 Beam divergence is determined by...
Definition
 diameter of PZT and frequency of sound
Term
 Lateral resolution is determined by...
Definition
 beam width
Term
 What is the lateral resolution at a depth of 8cm if the diameter of the PZT is 9mm?
Definition
 4.5 mm   *at the end of the near zone, the beam diameter is 1/2 the transducer diameter.
Term
 What is the lateral resolution at a depth of 16cm if the diameter of the PZT is 9mm?
Definition
 9mm   *at a depth of twice the near zone, the beam is as wide as the transducer
Term
 When the number of cycles in a pulse increases while the frequency remains the same, the numerical value of the range remains the same, the numerical value or the range resolution [improves, degrades, or remains the same]?
Definition
 Increases. *with more cycles in a pulse, the pulse becomes longer. the numerical value of the range resolution increases
Term
 When the number of cycles in a pulse increases (more ringing) while the frequency remains the same, the numerical value of the range resolution [improves, degrades, or remains the same].
Definition
 Degrades. *When the number of cycles increases, the spatial pulse length increases and the image quality degrades
Term
 Which of the following transducers has the best lateral resolution deep in the far field?   A. 4 MHz, 4 mm crystal diameter B. 6 MHz, 4 mm crystal diameter C. 4 MHz, 6 mm crystal diameter D. 6 MHz, 6 mm crystal diameter
Definition
 D. - it has the highest frequency and the largest diameter
Term
 The amplitude information of a B-mode is routed into to ___-axis of the CRT.
Definition
 z-axis
Term
 What are the 3 basic modes of display, or formats, are important in viewing ultrasound information?
Definition
 Amplitude mode Brightness mode Motion mode
Term
 ____-modes appear as a line of dots of varying brightness.
Definition
 B-mode
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