What term is defined as two items that are not associated or affiliated with each other?

Unrelated

What term is defined as two items that are associated or affiliated with one another?

Related or Proportional

Directly Related or Directly Proportional

What type of relationship is defined as two variables that are associated such that when one variable increases, the other item decreases?

Inversely Related or Inversely Proportional

What type of inverse relationship is defined as when two numbers are multiplied together the result is one?

Reciprocal Relationship

How are acoustic propagation properties defined?

The effects of the medium upon the sound wave.

T/F -  Sound can travel through a vacuum.

False

What is a basic definition of sound waves?

Sound waves are mechanical, longitudinal, waves which must travel through a medium in a straight line. 

What can be described as a disturbance in a medium where the individual particles of the medium cycle back-&-forth/up-&-down and energy is carried from one place to another?

Basic definition of a wave.

What are the 4 acoustic variables?

1-Pressure (Pascal-Pa),

2-Density (kg/cm3),

3-Temperature (degrees)

4- Distance (cm)

What are the 7 acoustic parameters which can be used to describe sound waves?

1-Period

2-Frequency

3-Amplitude

4-Power

5-Intensity

6-Wavelength

7-Propagation Speed

Which type of wave travels such that the particles oscillate in a direction that is perpendicular to the direction that the wave propagates?

Transverse Wave

ex: ocean wave

What is the basic definition of a longitudinal wave?

Particles which oscillate in the same direction (parallel) to the direction that the wave propagates.

EX: a slinky

What is basic wave interference? 

When 2 waves overlap at the same location at the same instant that they combine together forming 1 single wave which can be constructive or destructive.

T/F -  Sound waves can have constructive interference at one moment and destructive interference at a different moment.

TRUE – When sound waves of different frequencies interfere with each other the wave may result in constructive interference at one moment and destructive interference at a different moment.

What will happen when 2 sine waves which are in-phase are combined?  What type of interference is this called?

1-A stronger wave (higher amplitude) is produced.

2-constructive interference

What type of relationship can be described as whenever A & B are directly related and whenever the value of A changes (↑or ↓), the value of B changes in the same direction, but not by the same percent?

Direct Non-Linear Proportionality

What will happen when 2 sine waves which are out of phase are combined?  What type of interference is this called?

1-A weaker wave (lower amplitude) is produced. 

2-destructive interference

What is the definition of period?

The time it takes a single wave to vibrate within a single cycle or the time from the start of a cycle to the start of the next cycle.

What are the units associated with period?

Units of time (secs, ms)

T/F- Period is determined by the sound source only and not by the medium.

TRUE

T/F- The sonographer can adjust the period while using an ultrasound system with a particular transducer.

False.

What term is described as the number of particular events that occur in a specific duration of time?

Frequency

What is the frequency of a wave?

The number of cycles that occurs in one second.

What units are associated with frequency?

Units of per second

T/F- In clinical imaging, frequency ranges approximately form 2MHz – 10MHz.

TRUE

T/F- The frequency of a sound wave is determined by the medium only.

FALSE – The sound source only.

T/F- Frequency of a sound wave can be changed by the sonographer while using a particular ultrasound system or transducer.

FALSE – It cannot be changed.

What frequency term of sound waves are less than 20Hz which is below the threshold of human hearing?

INFRASONIC

What frequency term of sound waves which range from 20Hz – 20kHz can be heard by humans?

AUDIBLE

ULTRASONIC

Why is frequency important in diagnostic sonography?

It affects penetration and image quality.

What is the relationship between period and frequency?

INVERSELY RELATED

What happens if you multiply period and frequency together?  What is the name of this relationship?

1-The result is 1. 

2-Reciprocal relationship

List 3 parameters which describe the size or magnitude, or strength of a sound wave.

1-Amplitude

2-Power

3-Intensity

Describes the “bigness” of a wave.  It is the difference between the maximum value and the average or undisturbed value of an acoustic variable.  Also is the difference between the minimum value and the average value of the acoustic variable.

What are the units which are associated with amplitude?

Can have the units of any of the acoustic variables: 

Ex: Pressure – Pascals, Density – g/cm3, Particle motion - cm, inches – any distance, & decibels (dB).

What happens to amplitude as it travels through the body?

Amplitude decreases as it travels through the body.  The rate at which amplitude decreases as sound propagates depends on the characteristics of both the sound wave and the medium.

T/F – Initially, amplitude is determined only by the sound source, the ultrasound system.

TRUE

T/F – A control on ultrasound systems allows the sonographer to alter initial amplitude.

TRUE

How is amplitude measured?

Amplitude is measured from the baseline to the maximum value or from the baseline to the minimum value.

How is peak-to-peak amplitude measured?

Peak-to-Peak amplitude is the difference between maximum and minimum values of an acoustic variable.  Therefore, it is twice the value of the amplitude.

Define power.

Power is the rate of energy transfer or the rate at which work is performed.

What units are associated with power?

Units of Watts

How are amplitude and power related?

Directly proportional (α = proportional to)

Power α Amplitude squared

What happens to power as it travels through the body?

Power decreases as sound propagates through the body.  The rate at which power decreases as sound propagates depends on the characteristics of the medium and the wave.

T/F – Initially, power is determined only by the medium.

FALSE – Determined by the sound source (the ultrasound system) only.

T/F – Initial power, like amplitude cannot be changed by the ultrasound system.

FALSE – A control on the ultrasound systems allows the sonographer to alter the initial power of a wave.

A sonographer increases the amplitude of a wave by a factor of 4. How has the power changed?

4 x 4 = 16

Power α Amplitude Squared.  Thus, the power is increased 16-fold.

 A sonographer decreases the amplitude of a wave by a factor of ¼. How has the power changed?

¼ x ¼ = ⅛

Power α Amplitude 2.  Thus, the power is decreased by ⅛.

Define intensity.

Intensity is the concentration of energy in a sound beam.

How is intensity calculated?

Divide the beam’s power by the beam’s cross-sectional area.  It relates to how the power in a wave spreads or is distributed in space.  Therefore, intensity depends on both the power in the beam and the area over which the power is applied.

What units are associated with intensity?

Watts/square centimeter, or W/cm2. (watts from power and cm2 from beam area)

What happens as intensity travels through the body?

Intensity changes as sound propagates through the body.  The rate at which intensity changes as sound propagates depends on the characteristics of the medium and the shape of the sound beam.

T/F – Initially intensity is determined only by the sound source, the ultrasound system.

TRUE

How are intensity and power and amplitude related?

Directly proportional

Intensity α Power α Amplitude Squared

What term describes the distance or length of one complete cycle?

Wavelength

What units are associated with wavelength?

Units of mm, meters, or any other unit of length

What is unique about how wavelength is determined?

Wavelength is the only parameter that is determined by both the source and the medium.

Can a sonographer adjust the wavelength by using a particular transducer?

No, wavelength is not adjustable.

What is the relationship between wavelength and frequency?

As long as a wave remains in one medium wavelength and frequency are inversely related.  Ex: longer the wavelength, the lower the frequency.

What is the rule that defines the relationship between frequency and wavelength of sound in soft tissue?

To find the wavelength of a sound wave in soft tissue divide 1.54mm by the frequency in MHz.  or   

 λ(mm) = ­­­1.54mm/μs  

                    frequency(MHz)

Why is wavelength important in diagnostic ultrasound?

Shorter wavelength sound usually produces higher quality images with greater detail.  Higher freq. transducers produce shorter λ sound = creates images of superior quality.

What is the definition of propagation speed?

The distance that a sound wave travels through a medium in one second.

What units are associated with propagation speed?

Units of meters per sec or any distance divided by time

What is the typical value range of propagation speed of sound?

500m/s – 4000m/s  Depends on the tissue through which it is traveling.

How is propagation speed determined?

Speed is determined only by the medium through which it is traveling.  All sound, regardless, of frequency, travels at the same speed through any specific medium.

 Can propagation speed be adjusted by a sonographer?

NO – speed changes only when the wave travels from one medium to a different medium.

What is the speed of sound in soft tissue?

1540m/s or 1.54mm/μs or 1.54km/s

What characteristics of a medium determine the speed of sound in that medium?

Stiffness & Density

What is the definition of stiffness?

The ability of an object to resist compression.

How does stiffness affect speed?

As materials become stiffer, the speed of sound in that material increases.

Directly related

What 2 terms describe the degree of stiffness?

Elasticity or Compressibility

Opposites of Stiffness

What term describes the relative weight of a material?

DENSITY

What is the relationship between density and speed?

Inversely Related

As materials become denser (heavier), the speed of sound in the material decreases.

List the 5 additional parameters which are needed to describe pulsed sound.

1-Pulse Duration (PD)

2-Pulse Repetition Period (PRP)

3-Pulse Repetition Frequency (PRF)

4-Duty Factor (DF)

5-Spatial Pulse Length (SPL)

How is pulsed sound defined?

A pulse of ultrasound which is a collection of cycles that travel together.  Must have a beginning and an ending and the entire pulse travels as a single unit.

What are 2 components of pulsed ultrasound?

1-“ON” TIME, TRANSMIT, TALKING

2-“OFF” TIME, RECEIVE, LISTENING

How is pulse duration defined?

The actual time from the start of a pulse to the end of the pulse.  A single transmit, talking, or “on” time

What are the units which are associated with pulse duration?

UNITS OF TIME (μs, ms, sec)

T/F- Pulse duration is determined by the sound source only.

TRUE

T/F- The sonographer cannot alter pulse duration while using a particular ultrasound system and transducer.

TRUE

What 2 equations will express pulse duration mathematically?

PD (μs) = (# Cycles) (Period)

                  OR

PD (μs) = __#Cycles_____

                Frequency (MHz)            

DIRECTLY PROPORTIONAL

What is the relationship between PD and Period?

DIRECTLY PROPORTIONAL

INVERSELY PROPORTIONAL

T/F- Longer duration pulses are desirable for imaging because they create images of greater accuracy.

FALSE – SHORTER DURATION PULSES

Which term is defined as the distance that a pulse occupies in space from the start to the end of a pulse?

SPATIAL PULSE LENGTH (SPL)

List the units of spatial pulse length.

UNITS OF DISTANCE (mm)

T/F- Spatial pulse length is determined by both the sound source and the medium.

TRUE

T/F- A sonographer can alter pulse length.

FALSE – IN A PARTICULAR MEDIUM, A TRANSDUCER’S PULSE HAS A FIXED LENGTH THAT CANNOT CHANGE.

      SPL (mm) = (#Cycles) (λ –in mm)

What is the relationship between SPL and #Cycles in a pulse?

DIRECTLY PROPORTIONAL

What is the relationship between SPL and λ?

DIRECTLY PROPORTIONAL

What is the relationship between SPL and Frequency?

INVERSELY PROPORTIONAL

What is the difference between pulse duration (PD) and spatial pulse length (SPL)?

PD = time that a pulse is “on” and measured in microsecs (μs)

SPL = distance of the pulse end to end and measured in (mm)

List 2 characteristics which create long pulses.

1-Many cycles in a pulse

2-Cycles with longer λ

List 2 characteristics which create short pulses.

1-Few cycles in a pulse

2-Cycles with shorter λ

______________   ____________  _____________ is the time from the start of one pulse to the start of the next pulse.  It includes one PD and one listening time.

PULSE REPETITION PERIOD (PRP)

What units are associated with PRP?

UNITS OF TIME (ms)

What determines the PRP?

SOUND SOURCE & IMAGING DEPTH

T/F- A sonographer can alter the PRP.

FALSE – PRP is altered when a sonographer adjusts the imaging depth.

T/F- PRP is related to period and depth of view.

FALSE – UNRELATED to PERIOD

RELATED TO DEPTH OF VIEW

Define depth of view?

DESCRIBES THE MAXIMUM DISTANCE INTO BODY THAT AN ULTRASOUND SYSTEM IS IMAGING.

What is the relationship between PRP and depth of view?

DIRECTLY RELATED

↑DEPTH      ↑PRP

↓DEPTH      ↓PRP

What are the 2 components of PRP?  Which one can a sonographer change?

1-      TRANSMIT TIME

2-      RECEIVE TIME

RECEIVE TIME (LISTENING TIME) CHANGES WITH IMAGING DEPTH

________________  ______________  ______________ is the number of pulses that an ultrasound system transmits into the body each second.

PULSE REPETITION FREQUENCY (PRF)

List the units which are associated with PRF.

UNITS OF HERTZ (Hz) OR PER SEC.

PRF is determined only by the ________ _________, not by the ___________ through which sound travels.

SOUND SOURCE, MEDIUM

T/F- A sonographer can change PRF by adjusting the frequency of the transducer.

FALSE – PRF is UNRELATED to frequency

How are pulse repetition frequency and depth of view related?

INVERSELY RELATED

↑DEPTH     ↓PRF

↓DEPTH     ↑PRF

T/F- A sonographer adjusts the depth of view from 3cm to 10cm, the resulting PRF is now lower.

TRUE

How are PRP & PRF related?

INVERSELY RELATED

↑PRP      ↓PRF

↓PRP      ↑PRF

T/F- Just like period and frequency, PRP and PRF have a reciprocal relationship.

TRUE

What term is defined as the percentage or fraction of time that the system is transmitting a pulse?

DUTY FACTOR (DF)

What units are associated with duty factor?

NONE – it is a percentage & is dimensionless

What is the duty factor for continuous wave (CW) sound & why?

100%   or   1.0

ALWAYS TRANSMITTING

T/F- Only the sound source determines duty factor.

TRUE

How is duty factor (DF) related to imaging depth?

INVERSELY RELATED

↑DF        ↓DEPTH

↓DF        ↑DEPTH

How can duty factor be represented mathematically?

DF (%) = PD       X 100

PRP

What is the duty factor when the transducer is silent?

    0%

When is a duty factor of 0.2% used by ultrasound systems?

   WHILE CREATING ANATOMIC IMAGES

How does a sonographer change duty factor?

By altering the imaging depth.  As imaging depth increases, transmit time remains constant while listening time is prolonged.

List 3 pulsed wave (PW) parameters which are related to depth of view.

   1-      PRP

   2-      PRF

  3-        DF

Why are pulse duration (PD) and spatial pulse length (SPL) not adjustable by the sonographer?

      They are characteristics of the pulse itself and are inherent in the design of the transducer system.

Define spatial.

REFERS TO DISTANCE OR SPACE

Define peak in regards to intensity.

Define average.

THE MATHEMATICAL MIDDLE VALUE

Define temporal in regards to intensity.

Define pulsed in regards to intensity.

   THE AVERAGE INTENSITY FOR PULSE DURATION/TRANSMIT TIME ONLY (IGNORE LISTENING TIME)

What term is defined as the beam’s intensity at the location where it is maximum, usually at the center?

SPATIAL PEAK INTENSITY

Define temporal peak intensity.

THE GREATEST INTENSITY IN A PULSE AS IT PASSES BY WHICH IS ALWAYS > THE AVERAGE, BUT DOES NOT INCLUDE PULSES “OFF” TIME.

ONLY in CW is TP =TA because never resting

What is the intensity measurement which determines the average intensity during the most intense half cycle?

I_max

or

I_m

What is the highest intensity measurement used in diagnostic ultrasound?

SPTP

Define temporal average (TA).

AVERAGE INTENSITY ACROSS PRP WHICH INCLUDES “ON” & “OFF” TIME

ONLY in CW is TP = TA because never resting

AVERAGE INTENSITY IN SOUND FIELD

List 5 terms which characterize intensity.

1-      SPATIAL

2-      TEMPORAL

3-      PEAK

4-      AVERAGED

5-      PULSED

Which 2 intensity measurements are used in only in PW ultrasound?

SPPA & SAPA

What is the lowest intensity measurement used in diagnostic ultrasound?

SATA

Define pulse average intensity.

The intensity averaged during pulse duration (the transmit time).

Which intensity is most relevant with respect to tissue heating?

SPTA

When pulsed and continuous wave sound beams have the same SATP intensities, which sound beam has the higher SATA intensity?

CONTINUOUS WAVE SOUND BEAM

When pulsed and continuous wave sound beams have the same SATP intensities, which sound beam has the higher SATA intensity?

CONTINUOUS WAVE SOUND BEAM

Why does SPTA = SPPA & SATA = SAPA for continuous wave sound beams?

The sound beam is always “on” and the pulse average and temporal average intensities are the same.

What is the difference between frequency and period?

FREQUENCY = how often something happens & measures cycles/sec.

PERIOD = the time it takes for something to happen & measures sec/cycle

List 3 different basic types of mediums can sound waves travel in and which medium is the fastest?

1- SLOWEST IN GASES (AIR, LUNG)

2- FASTER IN LIQUIDS (WATER, BLOOD)

3- FASTEST IN SOLIDS (TISSUE, METAL, BONE)

What is the average speed of sound in blood?

1570m/sec

What is the average speed of sound in liver?

1550m/sec

What term is defined as the number of 10’s multiplied together to get that number & is a way to rank numbers?

LOGARITHM

What are decibels (dB)?

A unit of measure that compares the ratio of 2 intensities or amplitudes of sound waves and uses a logarithmic scale

Why are decibels used?  What purpose do they perform?

1- Decibels take a wide range of values and reduce the values to a smaller range. 

2- They are used to express a large change.

T/F- Decibels do not represent absolute values, but instead only gives the relationship between 2 values.

TRUE

____________ Decibels describe signals that are increasing in strength, or getting larger.

POSITIVE

____________ Decibels describe signals that are decreasing in strength, or getting smaller.

NEGATIVE

↑8x      or    ↓1/8

What is the average speed of sound in fat?

1450m/sec

 How much increase or decrease is 6dB?

↓1/4      or    ↑4x

How much increase or decrease is 10dB?

↑10x     or    ↓1/10

What is the average speed of sound in kidney?

1560m/sec

What is the average speed of sound in bone?

4000m/sec

What is the average speed of sound in water?

1480m/sec

↑2x      or     ↓1/2

What is the average speed of sound in muscle?

1580m/sec

How much increase or decrease is 20dB?

↑100x        or      ↓1/100

How much increase or decrease is 30dB?

↑1,000x     or      ↓1/1,000

What is the average speed of sound in brain tissue?

1520m/sec

How much increase or decrease is 40dB?

↑10,000x       or      ↓1/10,000

What is the relationship between attenuation and freq.?

DIRECTLY RELATED

↑ ATTENUATION          ↑FREQ.

↓ ATTENUATION          ↓FREQ.

What is the relationship between attenuation and distance?

DIRECTLY RELATED

↑DISTANCE                ↑ATTENUATION

↓DISTANCE                ↓ATTENUATION

What units are associated with attenuation?

DECIBELS (dB)

Define attenuation.

The degree of intensity, power, and amplitude of a sound wave weakens as it propagates in a medium.

List 2 factors which determine attenuation.

1-      PATH LENGTH

2-      FREQUNCY OF SOUND

List 3 processes which contribute to attenuation.

1-      REFLECTION

2-      SCATTERING

3-      ABSORPTION

What term describes the portion of a sound wave’s energy which may be redirected back to the sound source after it strikes a large boundary?

REFLECTION

List 2 forms of reflection which are created in soft tissue, depending on the nature of the interface that a sound wave strikes.

1-      SPECULAR REFLECTION

2-      DIFFUSE REFLECTION

What type of reflection occurs when the boundary is smooth, large, and flat compared to the wavelength and sound is reflected in only one direction in an organized manner?

What is a limitation of specular reflection?

Once the wave is slightly off-axis, the reflection does not return to the transducer.

What type of reflection occurs when a wave reflects off an irregular surface and it radiates in more than one direction?

DIFFUSE REFLECTION

What is a synonym of diffuse reflection?

BACKSCATTER

What is an advantage of diffuse reflection?

Suboptimal angles to the sound beam can still produce reflections that the transducer will receive.

What is a disadvantage of diffuse reflection?

Backscattered signals have a lower strength than specular reflections.

What is the attenuation coefficient?

The number of decibels of attenuation that occurs when the sound travels one centimeter (cm).

What units are associated with the attenuation coefficient?

dB/cm

What is a synonym of SP/SA FACTOR?

BEAM UNIFORMITY COEFFICIENT (BUC)

List 3 characteristics of the SP/SA FACTOR.

1- DESCRIBES THE DISTRIBUTION OF  A BEAM IN SPACE                               

2- MUST BE > 1

3- RELATES TO SPACE (DISTANCE) AS DUTY FACTOR RELATES TO TIME

List 3 factors which affect the number of pulses/image.

1- # OF PULSES/ SCAN LINE (MULTIPLE VS. SINGLE FOCUS)                                

2- SECTOR SIZE

3- LINE DENSITY OR LINES/ANGLE OF SECTOR

*MORE INFO ALWAYS REDUSES FRAME RATE

List 2 factors which affect frame rate.

1-      SPEED OF SOUND FIXED IN SOFT TISSUE

2-      IMAGING DEPTH (AJUSTABLE BY SONOGRAPHER)

What units are associated with frame rate?

UNITS OF Hz (TIME)

What affects the amount of gray shades in the spectrum?

1-      REFLECTED SIGNAL

2-      # OF RBCS

*LOW RBCS IN ANEMIA

List 4 characteristics which are seen with lower line density.

1-   ↑ FRAME RATE

2- SHORTER TIME/FRAME

3- ↑TEMPORAL RESOLUTION

4-  ↓SPATIAL RESOLUTION

List 5 characteristics which are seen with high frame rates.

1- SHALLOW IMAGING

2- SINGLE FOCUS

3- NARROW SECTOR

4- LOW LINE DENSITY

5- BETTER TEMPORAL RESOLUTION

List 4 characteristics of a high pulser setting.

1- VIBRATION OF ELEMENT  STRONGER

2- STRONGER SIGNAL SENT INTO BODY

3- STRONGER SIGNAL RECEIVED

4- IMAGE IS BRIGHTER

What is the relationship between pulse duration (PD) and image quality?

INVERSELY RELATED

↑ IMAGE QUALITY      ↓ PD

↓ IMAGE QUALITY      ↑ PD

List 4 characteristics of a low pulser setting.

1- VIBRATION OF ELEMENT WEAKER

2-  WEAK SIGNAL SENT INTO BODY

3-   WEAK SIGNALS RECEIVED

4-   IMAGE MAY BE DARK

List 4 characteristics which can create slower frame rates.

1-  DEEPER IMAGING

2- MULTIPLE FOCAL

            -↑ LATERAL RESOLUTION

            -NARROW OVER WIDE RANGE OF DEPTHS

3-    WIDE SECTOR

4-   ↑ LINE DENSITY

      -↑ SPATIAL RESOLUTION

      - MORE DETAIL

List 4 characteristics which are seen with higher line density.

1- LOWER FRAME RATE

    2- LONGER TIME/ FRAME

            3- ↓ TEMPORAL RESOLUTION

4- ↑SPATIAL RESOLUTION

List 4 characteristics of a high pixel density image.

1-      MANY PIXELS / INCH

2-      SMALLER PIXELS

3-      MORE DETAIL

4-      ↑ SPATIAL RESOLUTION

What is the relationship between the Doppler shift and frequency?

DIRECTLY RELATED

↑ DOPPLER SHIFT          ↑FREQ.

↓ DOPPLER SHIFT          ↓FREQ.

What is the relationship between the Doppler shift and velocity of RBCs?

DIRECTLY RELATED

↑ DOPPLER SHIFT           ↑RBCs VELOCITY

↓ DOPPLER SHIFT           ↓RBCs VELOCITY

T/F- Hematocrit may affect the intensity of the Doppler shift.

TRUE

EX: ANEMIA – LESS RBCs = LESS REFLECTORS

What is the relationship between pulse/frame and frame rate?

INVERSELY RELATED

↓ # PULSE/IMAGE           ↑FR

↑ # PULSE/IMAGE           ↓FR

List 4 characteristics which show how focusing alters the sound beam.

1-     BEAM DIAMETER IN NEAR FIELD & FOCAL ZONE NARROWS

2- LENGTH OF NEAR FIELD REDUCED (SHALLOWER FOCUS)

3-  ↑ BEAM DIAMETER IN FAR ZONE  

4-  FOCAL ZONE IS SMALLER

List 5 characteristics are associated with low Q factor.

1-      SHORT RING

2-      BROAD (WIDE) BANDWIDTH

3-      GOOD AXIAL RESOLUTION

4-      PULSED WAVE

5-      DIAGNOSTIC (DX.) ULTRASOUND

What is the relationship between the pulser and PRP?

PRP IS SET BY THE PULSER DECIDING ON TIME BETWEEN PULSES.

What is the relationship between the pulser and PRF?

PRP & PRF ARE RECIPROCALS SO THE PULSER ALSO DETERMINES PRF.  PRP & PRF DETERMINE MAXIMUM  IMAGING DEPTH (DEPTH OF VIEW).

What is the relationship between frame rate and depth?

INVERSELY RELATED

   ↑ DEPTH             ↓ FR

   ↓ DEPTH             ↑ FR

What is the relationship between frame rate and time?

INVERSELY RELATED

↑ TIME          ↓FR

↓ TIME          ↑FR

List 4 characteristics of narrow bandwidth.

1-      PURER FREQ.

2-      LONG DURATION/RINGING TIME

3-      NON-IMAGING TRANSDUCERS USE IN THERAPEUTIC & CW TRANSDUCERS

4-      HIGH Q (QUALITY) FACTOR

What happens to the ringing time when you dampen the transducer crystal?

↓ RINGING TIME

List 4 characteristics of wide bandwidth.

1-      INCLUDES MANY FREQS.

2-      SHORTER DURATION/RINGING TIME

·         DAMPENING PROHIBITS FREE VIBRATION

3-      USED IN PULSED ULTRASOUND

4-      LOW Q (QUALITY) FACTOR

List 4 characteristics of wide dynamic range.

1-      MANY CHOICES

2-      MANY SHADES OF GRAY (20 SHADES)

3-      USED IN MOST GRAY SCALE IMAGING

4-      LOW CONTRAST

How do lower frequency beams impact focusing of the transducer crystal?

BEAMS DIVERGE MORE IN THE FAR ZONE

List 5 characteristics of low pixel density.

1-   FEW PIXELS/INCH

2-   LARGER PIXELS

3-   LESS DETAIL

4-   ↓ SPATIAL RESOLUTION

5-    GRAINY PICTURE

List 4 characteristics of a narrow dynamic range.

1-      FEW CHOICES

2-      BI-STABLE (2 CHOICES) BLACK OR WHITE

3-      FEW SHADES OF GRAY

4-      HIGH CONTRAST

What is the relationship between frequency and beam divergence?

INVERSELY RELATED IN UNFOCUSED DISC SHAPED ELEMENT

What is the relationship between frequency and focal depth with fixed focus?

DIRECTLY RELATED IN UNFOCUSED DISC SHAPED ELEMENT (IF DIAMETER IS UNCHANGED)

T/F- 2 identical probes with different frequencies will focus at different depths.

TRUE –

↑ F = Deeper Focus & ↓ F = Shallow Focus

What is the relationship between image quality and axial resolution?

LOWER NUMERICAL VALUE = BETTER RESOLUTION

SHORTER PULSES

What is the relationship between crystal diameter and beam divergence?

INVERSELY RELATED IN UNFOCUSED DISC SHAPED ELEMENT

List 4 characteristics of a high Q (quality) factor.

1-   LONG RING

2-   NARROW BANDWIDTH

3-   POOR AXIAL RESOLUTION

4-      ALL CW

What is the relationship between transducer diameter and focal depth with a fixed focus?

DIRECTLY RELATED IN UNFOCUSED DISC SHAPED ELEMENT (WHEN FREQ. IS UNCHANGED)

T/F- 2 identical probes with different diameters will focus at the same depth.

FALSE –

            ↑ DIAMETER = DEEPER FOCUS

↓ DIAMETER = SHALLOW FOCUS

List 3 characteristics of fields and frames.

1-      TV IMAGE (CRT) IS MADE OF 525 HORIZONTAL LINES

2-      ODD # ARE WRITTEN 1^ST (ODD FIELD) 1/60 OF A SEC.

3-      THEN EVEN # (EVEN FIELD) ARE WRITTEN 1/60 OF A SEC.

What is the relationship between pressure gradients and blood flow?

↑ PRESSURE GRADIENT WHEN, ↑ FLOW OR ↑ RESISTANCE

       OR

↑ FLOW WHEN, ↑ PRESSURE OR ↓ RESISTANCE

What is the relationship between contrast imaging and the mechanical index (M.I.)?

VALUE OF M.I. indicates the amount of CONTRAST HARMONICS CREATED.

↑ with LOWER FREQ. & STRONGER sound waves or ↑ Pressure Variation

What frequency range will RBCs resonate?

BETWEEN 2 - 4MHZ

List 3 characteristics of a high number packet size.

1-      MANY PULSES/SCAN LINE

2-      LOW FRAME RATES

3-      GOOD COLOR

List 3 characteristics of low number packet size.

1-      FEW PULSES/ SCAN LINE

2-      HIGH FRAME RATE

3-      WEAK OR PATCHY COLOR

How will more bits/pixel affect the ultrasound image?

MORE SHADES OF GRAY

            ↑ CONTRAST RESOLUTION

What is the relationship between dynamic range (DR) and gray scale images?

↑ DR = BLACK & WHITE

↓DR = MANY SHADES OF GRAY

What type of frequency beams diverge less in the far field improving lateral resolution?

HIGHER FREQUENCY BEAMS

How does higher frequencies improve axial and lateral resolution?

1-      AXIAL Resolution - SHORTER λ

2-      LATERAL RESOLUTION – LESS DIVERGENCE in FAR field & beams are NARROWER than LOW freq. beams

List 2 characteristics which creates an unfocused sound beam.

1-      STRAIGHT LINE SPIKE PATTERNS

2-      D-SHAPED OR AN OUTWARD CURVED SPIKE PATTERN

LIST 3 parameters which can cause a resistance/impedence for blood to flow.

Which one will have the greatest resistance?

1-      ↑ VESSEL LENGTH

2-      ↓ VESSEL DIAMETER (GREATEST - 4Xs)

3-      ↑FLUID VISCOSITY

·         BLOOD 50% GREATER VISCOSITY THAN WATER

LIST 4 characteristics which can cause a change in the Doppler shift.

1-      VELOCITY OF REFLECTOR (RBC)

2-      TRANMITTED FREQ.

3-      COS θ OF ANGLE BETWEEN BLOOD FLOW & AXIS OF BEAM

4-      IF DOUBLE VELOCITY, THEN DOUBLE THE CHANGE OF FREQ.

What is the role of the transducer as an ultrasound component?

During TRANSMISSION – transforms ELECTRICAL energy into ACOUSTIC energy

During RECEPTION – converts ACOUSTIC energy into ELECTRICAL energy