Ultrasound Physics- World Travelers of the 7 Continents
Ultrasound Physics World Travelers Mind Map
1. Chapter 1_The Basics
1.1. Graphs
1.1.1. The horizontal axis
1.1.1.1. runs side to side
1.1.2. The vertical axis
1.1.2.1. runs up and down
1.2. Terms
1.2.1. Unrelated
1.2.1.1. Two items: not associated
1.2.2. Related/ Proportional
1.2.2.1. Two items: associated/ affiliated, the relationship between items does not have to be secified
1.2.3. Directly related/ Directly proportional
1.2.3.1. Two items: associated, one item increase and the other increase
1.2.3.2. Graph: lower left --> upper right
1.2.4. Inversely related/ Inversely proportional
1.2.4.1. Two items: associated, one item increase and the other decrease
1.2.4.2. Graph: upper left --> lower right
1.2.5. Reciprocal relationship
1.2.5.1. Two numbers are multiplied -> the result is one
1.2.5.2. Special form of inverse relationship: one increase and other decrease
1.3. Units
1.3.1. Typical Dimensional Units
1.3.1.1. Length
1.3.1.1.1. Distance or circumference (cm, feet)
1.3.1.2. Area
1.3.1.2.1. Ellipse used to measure (cm^2, ft^2)
1.3.1.3. Volume
1.3.1.3.1. (cm^3, ft^3)
1.3.1.4. Percent is not a unit.
1.3.1.5. Increase by a factor
1.3.1.5.1. Means multiply by that number
1.3.1.6. Decrease by a factor
1.3.1.6.1. Means divide by that number
1.3.2. Metric System
1.3.2.1. Giga (G) = billion = 10^9 = 1,000,000,000
1.3.2.2. Mega (M) = million = 10^6 = 1,000,000
1.3.2.3. Kilo (K) = thousand = 10^3 = 1,000
1.3.2.4. Hecto (h) = hundred = 10^2 = 100
1.3.2.5. Deca (Da) = ten = 10^1 = 10
1.3.2.6. Meter (M) - Liter (L) - Gram (G) = zero = 0
1.3.2.7. Deci (d) = tenth = 10^(-1) = .1
1.3.2.8. Centi (c) = hundredth = 10^(-2) = .01
1.3.2.9. Milli (m) = thousandth = 10^(-3) = .001
1.3.2.10. Micro (μ) = millionth = 10^(-6) = .0000001
1.3.2.11. Nano (n) = billionth = 10^(-9) = .000 000 0001
1.3.3. Complementary Metric Units
1.3.3.1. Think of these pairs as belonging together
1.3.3.2. Giga-nano = G & n = billions & billionths
1.3.3.3. Mega-micro= M & μ = millions & millionths
1.3.3.4. Hecto-centi = h & c = hundreds & hundredths
1.3.3.5. Deca-deci = da & d = tens & tenths
1.3.4. Powers of Ten
1.3.4.1. Scientific or Engineering Notation
1.3.4.1.1. Shorthand for very large or very small numbers
1.3.4.2. Rule
1.3.4.2.1. Shift the decimal point so the resulting number is between one and ten
1.3.4.2.2. Multiply by the appropriate power of 10
1.3.4.3. Note
1.3.4.3.1. A positive exponent = greater than 10
1.3.4.3.2. A negative exponent = less than 1
1.3.4.3.3. An exponent of zero = between 1 and 10
2. Chapter 2-Sound
2.1. Sound Waves
2.1.1. All waves CARRY ENERGY from place to place.
2.1.1.1. Heat
2.1.1.2. Sound
2.1.1.3. Magnetic
2.1.1.4. Light
2.1.2. Sound is a MECHANICAL and LONGITUDINAL wave.
2.1.3. Sound travels in a STRAIGHT line.
2.1.4. Sound CANNOT travel through a vacuum.
2.1.4.1. Sound MUST travel though a medium.
2.1.5. A series of
2.1.5.1. Compressions
2.1.5.1.1. Areas of increased pressure and density
2.1.5.2. Rarefactions
2.1.5.2.1. Areas of decreased pressure and density
2.1.6. Biologic Effects
2.1.6.1. The effects of the sound wave upon the biologic tissue.
2.1.7. Acoustic Propagation Properties
2.1.7.1. The effects of the medium upon the sound wave.
2.2. Waves
2.2.1. Transverses Wave
2.2.1.1. Particles move in a direction perpendicular to the direction that the wave propagates.
2.2.2. Longitudinal Wave
2.2.2.1. Particles move in the same direction that the wave propagates.
2.3. Phase Relationships
2.3.1. In phase
2.3.1.1. When PEAKS (max value) occur at the same time and location.
2.3.1.2. When TROUGHS (min value) occur at the same time and location.
2.3.2. Out of phase
2.3.2.1. When PEAKS and TROUGHS occur at different times.
2.4. Interference
2.4.1. Definition
2.4.1.1. When two waves overlap at the same location and time, they combine into a single new wave.
2.4.2. Constructive Interference
2.4.2.1. Occurs when the amplitude of the new, combined wave is GREATER than the original two waves.
2.4.2.2. IN PHASE WAVES interfere constructively
2.4.3. Destructive Interference
2.4.3.1. Occurs when the amplitude of the new, combined wave is LESS than the original waves.
2.4.3.2. OUT PHASE WAVES interfere destructively.
2.4.4. Note
2.4.4.1. With different frequencies, constructive and destructive interference occurs with waves.
2.5. Acoustic Variables
2.5.1. Identify which waves are sound waves.
2.5.1.1. Pressure
2.5.1.1.1. Concentration of force within an area
2.5.1.2. Density
2.5.1.2.1. Concentration of mass within a volume
2.5.1.3. Distance
2.5.1.3.1. Measure of particle motion
2.5.1.4. Temperature
2.5.1.4.1. Measure of heat
2.5.2. When an acoustic variable changes rhythmically in time, a sound wave is present.
2.6. Acoustic Parameters
2.6.1. Describe the features of a particular sound wave.
2.6.2. SEVEN acoustic parameters:
2.6.2.1. Period
2.6.2.2. Frequency
2.6.2.3. Amplitude
2.6.2.4. Power
2.6.2.5. Intensity
2.6.2.6. Wavelength
2.6.2.7. Propagation speed
3. Chapter 7-Range Equation
3.1. TERMS
3.1.1. Range Equation
3.1.1.1. The relationship between round-trip pulse travel time, propagation speed, and distance to a reflector. Total distance the pulse travels is twice the reflector depth.
3.1.1.1.1. Definition
3.1.1.2. depth (mm) = 1.54 mm/μs x go-return time (μs) / 2
3.1.1.2.1. Formula
3.1.1.3. Time of flight and the average speed of sound in soft tissue is known (1.54 mm/μs). Calculate the distance of the object location. Distance to boundary (mm) = go-return time (microsecond) x speed (mm/microsecond) / 2.
3.1.1.3.1. Units
3.1.1.4. Since ultrasound systems measure the time of flight and the average speed of sound in soft tissue is known (1.54 mm/μs), then we can calculate the distance of the object location. Distance to boundary (mm) = go-return time (microsecond) x speed (mm/microsecond) / 2.
3.1.1.4.1. Range Equation: Typical Value
3.1.1.5. Yes, sonographer can adjust the depth.
3.1.1.5.1. Range Equation: Can it be adjusted/changed?
3.1.1.6. What factors is it determined by?
3.1.1.6.1. Ultrasound systems determine reflector depth by measuring a pulse's time-of-flight with a very accurate stopwatch.
3.1.1.7. Relationship to other parameters.
3.1.1.7.1. Since the average speed of sound in soft tissue is known, the time-of-flight and distance that the pulse travels are directly related.
3.1.2. LARRD Resolution
3.1.2.1. For axial resolution, use the mnemonic LARRD: All 5 are needed to completely characterize the LARRD Resolution.
3.1.2.1.1. Longitudinal
3.1.2.1.2. Axial
3.1.2.1.3. Range
3.1.2.1.4. Radial
3.1.2.1.5. Depth
3.1.2.2. Is the ability to distinctly identify two structures that are very close together when they are side-by-side, or perpendicular, to the sound beam's main axis.
3.1.2.2.1. LARRD Definition
3.1.2.3. LARRD Formulas:
3.1.2.3.1. axial resolution (mm) = spatial pulse length (mm) / 2
3.1.2.4. Axial resolution is measured in mm or any other units of distance.
3.1.2.4.1. LARRD Units
3.1.2.5. In clinical imaging, axial resolution ranges from 0.1 to 1.0 mm. Lower numberical values indicate shorter pulses and improved image accuracy.
3.1.2.5.1. LARRD Typical Values
3.1.2.6. No. Since the spatial pulse length for a transducer is fixed, the sonographer cannot change axial resolution.
3.1.2.6.1. LARRD, Can it be adjusted/changed?
3.1.2.7. Axial resolution is related to the spatial pulse length. Recall that spatial pulse length is determined by both the sound source and the medium.
3.1.2.7.1. Shorter pulses improve axial resolution.
3.1.2.8. LARRD Parameters relationship.
3.1.2.8.1. Axial: front-to-back / parallel to beam
3.1.2.8.2. Lateral: side-by-side / perpendicular to beam
3.2. The 13-Microsecond Rule
3.2.1. The 13-microsecond rule always applies when sound travels through soft tissue.
3.2.2. For every 13 μs of go-return time, the object creating the reflection is 1 cm deeper in the body.
3.2.3. Parameters related to: Pulse Repetition Period (PRP) and Pulse Repetition Frequency (PRF)
3.2.4. Total Distance Traveled 2 cm 4 cm 6 cm 8 cm 20 cm
3.2.4.1. Reflector Depth 1 cm 2 cm 3 cm 4 cm 10 cm
3.2.4.1.1. Time of Flight 13 μs 26 μs 39 μs 52 μs 130 μs
3.3. Time-of-Flight or Go-Return Time
3.3.1. Definition: The elapsed time from pulse creation to pulse reception.
3.3.2. Relationship to other parameters: Time-of-flight and distance that the pulse travels are directly related.
3.3.3. Greater distances prolong the time-of-flight; lesser distances shorten the time-of-flight.
4. Welcome aboard! First Stop- South America
5. Next Stop Antartica
6. Next Stop -Europe
7. Last Stop -Australia
8. Thanks for flying!
9. Chapter 3-Describing Sound Waves
9.1. 7 Parameters
9.1.1. 1.Period
9.1.1.1. 2.Frequency
9.1.1.1.1. 3. Wavelength
9.1.2. All 7 parameters are needed to completely characterize a sound wave.
9.2. Terms
9.2.1. Period:
9.2.1.1. The time it takes a wave to vibrate a single cycle.
9.2.1.1.1. Determined by sound source ONLY. Sonographer CANNOT change.
9.2.1.1.2. Time: microseconds, seconds, minutes, hours, days, etc.
9.2.1.1.3. .06-.5 microseconds
9.2.2. Frequency:
9.2.2.1. The number of particular events that occur in a specific duration of time.
9.2.2.1.1. Determined by sound source ONLY. Sonographer CANNOT change.
9.2.2.1.2. Hertz
9.2.2.1.3. 2 Mhz-15Mhz
9.2.3. Wavelength:
9.2.3.1. Is the distance or length of one complete cycle.
9.2.3.1.1. Determined by BOTH sound source and medium. Sonographer CANNOT change.
9.2.3.1.2. mm, meters, or any unit of length
9.2.3.1.3. .1-.8mm
9.2.3.2. wavelength= prop speed ( mm/us) / Frequency (MHz)
9.2.4. Speed
9.2.4.1. The rate at which an event occurs.
9.2.5. Amplitude:
9.2.5.1. Is the "bigness" of a wave.
9.2.5.1.1. Initially determined by sound source , however it decreases as it propagates. Sonographer CAN control amplitude.
9.2.5.1.2. Pressure:Pascals Density:g/cm^3 Particle Motion:cm/inches (any measurment)
9.2.5.1.3. 1 Mpa-3 Mpa
9.2.6. Power:
9.2.6.1. The rate of energy transfer or the rate at which work is performed.
9.2.6.1.1. Initially determined by sound source , however it decreases as it propagates. Sonographer CAN control the power.
9.2.6.1.2. Watts
9.2.6.1.3. .004-.090 watts
9.2.7. Intensity:
9.2.7.1. Is the concentration of energy in a sound beam.
9.2.7.1.1. Initially only by a sound source, but changes as it propagates through the body. Sonogrpaher CAN change the intensity.
9.2.7.1.2. W/cm^2
9.2.7.1.3. .01-300 W/cm^2
9.2.7.2. Intensity= Power (w) / Area (cm^2)
9.2.8. Propagation Speed:
9.2.8.1. Is the rate at which a sound wave travels through a medium.
9.2.8.1.1. Determined ONLY by the medium. Sonographer CANNOT change.
9.2.8.1.2. meters/second or any distance divided by time
9.2.8.1.3. 500 m/s to 4000m/s
9.2.8.1.4. Speed of sound in soft tissue= 1,540 m/s
9.2.8.2. Speed= Frequency (Hz) x Wavelength (m)
9.2.8.2.1. Two characteristics of a medium 1) Stiffness 2) Density
9.2.9. Sound
9.2.9.1. The frequency at which a wave travels.
9.2.10. Medium
9.2.10.1. The tissue through which the sound is traveling.
9.2.11. Hertz:
9.2.11.1. The unit for frequency, another way to say per second.
10. CHAPTER 4 - DESCRIBING PULSED WAVES
10.1. PULSED SOUND HAS 5 PARAMETERS: Pulsed Duration, Pulsed Repetition Period, Pulsed Repetition Frequency, Duty Factor, & Spatial Pulse Length.
10.1.1. Pulse - small bursts of acoustic energy.
10.2. PULSED SOUND HAS 2 COMPONENTS: Transmit (talking time) and Receive (listening time).
10.2.1. NOTE: Pulse is a pulse. Transducer's talking time doesn't change.
10.3. Pulsed duration - time from the start of a pulse to the end of a pulse.
10.3.1. Units = microseconds Value= (time) 0.3 - 2.0
10.3.1.1. Determined by the source only. Not adjusted by the sonographer.
10.3.2. There are 2 formulas: 1.) is equal to the # of cycles divided by the frequency (MHz). 2.) It is equal to the # of cycles in each pulse multiplied by the period of each cycle (microseconds).
10.3.2.1. Can be long or short. Long - many cycles or individual cycles with long periods. Short - few cycles or individual cycles with short periods. Pulse duration is proportional to # of cycles in pulse / period, but inversely to Frequency.
10.3.2.1.1. NOTE: Shorter Pulse Duration is chosen for imaging because of greater accuracy.
10.4. Spatial Pulse Length - is the length or distance that an entire pulse occupies in space.
10.4.1. Units = (distance) m, cm, mm. Value = 0.1 - 1.0 mm.
10.4.1.1. Determined by the sound source / medium. Not adjusted by the sonographer.
10.4.1.1.1. Two characteristics create long pulse length: many cycles in the pulse & cycles with longer wavelengths. Two characteristics that create short pulse length: fewer cycles in the pulse & cycles with shorter wavelengths.
10.4.2. Formula: is the # of cycles multiplied by the wavelength (mm).
10.4.2.1. SPL is directly proportional to the # of cycles in the pulse / wavelength BUT inversely proportional to Frequency.
10.5. Pulse Repetition Period - the time from the start of one pulse to the start of the next pulse.
10.5.1. Units = (time) microseconds Value = 100 microseconds - 1 millisecond.
10.5.1.1. Determined by sound source only. Can be changed by the sonographer (imaging depth that is selected).
10.5.2. Formula: is equal to the pulse duration plus the listening time. (Deeper image is associated with longer PRP).
10.5.2.1. PRP is unrelated to period and only related to depth of view. EX: If PRP increases, imaging depth increases. If PRP decreases, imaging depth decreases.
10.6. Duty Factor - the percentage or fraction of time that the system transmits a pulse.
10.6.1. Expressed in percentage (dimensionless) Value = 0.2 % - 0.5 %
10.6.1.1. Determined by the sound source only. Sonographer can adjust by changing the depth. Duty factor is inversely related to depth.
10.6.2. For imaging: DF in range because creating images takes much more receiving time than transmitting.
10.6.2.1. For Doppler with CW (continuous wave): The DF is 100% because CW is always transmitting / receiving.
10.6.3. Formula: (%) = 1.) PRF = 1 divided by PRP 2.) PRP = 1 divided by PRF 3.) PFR x PRP = 1
10.7. Pulse Repetition frequency - the # of pulses that an ultrasound system transmits into the body each second (NOT cycles)
10.7.1. Units = (per second) Hz Value = 1,000 - 10,000 Hz
10.7.1.1. Determined by sound source ONLY. Sonographer can adjust the depth of view.
10.7.1.1.1. Shallow image = higher PRF Deep Image = lower PRF
10.7.2. Note: PRF is reciprocal to PRP and unrelated to Frequency. PRF and Depth of view are inversely related.
10.7.2.1. Formula: (%) = Pulse Duration divided by Pulse Repetition Period X 100.
10.8. Shallow & Deep Images
10.8.1. Shallow images involve: less listening, shorter PRP, higher PRF, & higher Duty Factor. (Images look better)
10.8.1.1. Deep Images involve: more listening, longer PRP, lower PRF, & lower Duty Factor.
10.9. Important Note: Some parameters are used in both Continuous wave and Pulsed waves.
10.9.1. These include: Period, Frequency, Wavelength, & Propagation Speed.
10.10. * By adjusting image depth, sonographers can change: PRP, PRF, & Duty Factor.
10.11. * Pulse Duration & Spatial Pulse Length are only characteristics of pulse. This cannot be changed by the sonographer.
11. Chapter 6 - Interaction of Sound and Media
11.1. Attenuation- the decrease in intensity, power and amplitude of a sound wave as it travels.
11.1.1. Attenuation is unrelated to speed.
11.1.2. Expressed in units of decibels (dB)
11.1.3. Attenuation is determined by path length and frequency of sound.
11.1.3.1. Distance and Attenuation are directly related.
11.1.3.2. Frequency and attenuation are directly related.
11.1.4. Three processes contribute to attenuation: Reflection, Scattering, and Absorption.
11.1.4.1. Scattering- of ultrasound is the random redirection of sound in many directions.
11.1.4.1.1. Back Scatter- when a wave reflects off an irregular surface, it radiates in more than one direction.
11.1.4.1.2. Rayleigh Scattering- is a special form of scattering that occurs when the structure's dimensions are much smaller than the beam's wavelength
11.1.4.1.3. Scattering is directly related to frequency.
11.1.4.2. Reflection- as sound strikes a boundary, a portion of the wave's energy may be redirected or reflected back to the sound source
11.1.4.2.1. Reflection Angle- the angle between the reflected sound beam and the line perpendicular to the boundary.
11.1.4.2.2. Specular Reflection- when a boundary is smooth, the sound is reflected in only one direction in an organized manner.
11.1.4.2.3. Diffuse Reflection- when a wave reflects off an irregular surface, it radiates in more than one direction causing irregularities.
11.1.4.3. Absorption- occurs when ultrasonic energy is converted into another energy form
11.1.4.3.1. Directly related to frequency.
11.1.5. Attenuation is unrelated to speed.
11.2. Decibels- a unit to measure the intensity of a sound or the power level of an electrical signal by comparing it with a given level on a logarithmic scale.
11.2.1. Decibel notation is a relative measurement, comparison, ratio, and logarithm.
11.2.1.1. Positive Decibels: report signals that are increasing in strength or getting large.
11.2.1.2. Negative Decibels: describe signals that are decreasing in strength or getting smaller.
11.3. Half Value Layer Thickness- the distance sound travels in a tissue that reduces the intensity of sound to one-half its original value.
11.3.1. Typical value: 0.25 to 1.0 cm
11.3.2. Expressed in units of cm (or units of length)
11.3.3. Half value layer thickness depends on the medium, and the frequency of sound.
11.4. Impedance- the acoustic resistance to sound traveling in a medium
11.4.1. impedance (rayls) = density (kg/m^3) x prop. speed (m/s)
11.4.2. Expressed in units of rayls & represented by Z.
11.4.3. Typical Values- 1,250,000 to 1,750,000 rayls (1.25 to 1.75 Mrayls)
11.4.4. Determined by the medium. Calculated not measured.
11.5. Normal Incidence- means that the incident sound beam strikes the boundary at 90 degrees.
11.5.1. Incident Angle- angle between incident sound direction and a line perpendicular to the boundary of a medium
11.5.2. Normal incidence is also called perpendicular, orthogonal, right angle and 90 degrees.
11.5.3. Angle must be 90 degrees.
11.5.4. Reflection only occurs if the two media at the boundary have different acoustic impedances.
11.6. Oblique incidence- occurs when the incidence sound beam strikes the boundary at any angle other than 90 degrees.
11.6.1. Acute Angle- angle that is less than 90 degrees.
11.6.2. Obtuse Angle- angle greater than 90 degrees
11.6.3. With Oblique incidence - we can not predict whether sound will reflect or transmit after striking a boundary. When a sound beam strikes a boundary obliquely, reflection/transmission may or may not occur.
11.6.3.1. Two physical principles apply to reflection with oblique incidence: conservation of energy and reflection angle=incident angle.
11.6.3.2. Transmission with oblique incidence- transmission is uncertain.
11.6.3.2.1. Sound beam might bend or change.
11.7. Coefficients
11.7.1. Reported as percentages and are dimensionless.
11.7.2. Intensity Transmission Coefficient- (ITC) is the percentage of intensity that passes in the forward direction when the beam strikes an interface between two media
11.7.2.1. Value of ITC ranges from 0% to 100%
11.7.2.2. Equation: ITC%= transmitted intensity/incident intensity X 100
11.7.3. Intensity Reflection Coefficient- (IRC) is the percentage of intensity that bounces back when a sound beam strikes the boundary between two media.
11.8. Reflection and Transmission
11.8.1. Incident intensity- intensity of the sound wave at the instant prior to striking a boundary.
11.8.2. Reflected intensity- portion of the incident intensity that, after striking a boundary, changes direction and returns back from where it came.
11.8.3. Transmitted intensity- portion of the incident intensity that after striking a boundary, continues on in the same general direction that it was originally traveling.
11.8.4. ALL INTENSITIES ARE UNITS OF W/CM^2
11.9. ATTENUATION COEFFICIENT- the amount of attenuation per centimeter, a way to report attenuation without dealing with distance.
11.9.1. expressed in dB/cm
11.9.2. in soft tissue, the attenuation coefficient is 1/2 of the transducer's frequency
11.9.2.1. 0.5 dB/cm/Mhz
11.9.3. Equation for total attenuation: Total attenuation (dB)= path length (cm) x attenuation coefficient (dB/cm)
12. CHAPTER 5 - Intensity
12.1. Definition
12.1.1. Power/area (W/cm2)
12.2. 10 comandments
12.2.1. 1
12.2.1.1. Intensity is reported in different ways.
12.2.1.1.1. based on
12.2.1.1.2. Ex. SPTP > Im > SPPA > SPTA > SATA
12.2.2. 2.
12.2.2.1. Importance
12.2.2.1.1. In the study of bio effect of ultrasound
12.2.3. 3.
12.2.3.1. SPTA
12.2.3.1.1. Most relevant intensity with respect to tissue heating
12.2.4. 4.
12.2.4.1. Measurements
12.2.4.1.1. Peak > Average
12.2.5. 5.
12.2.5.1. Beam uniformity coefficient
12.2.5.1.1. SP/SA Factor
12.2.6. 6.
12.2.6.1. Duty factor
12.2.6.1.1. Describes the relationship of a beam with time
12.2.7. 7.
12.2.7.1. For Continuous Wave (CW)
12.2.7.1.1. the beam is always "ON"
12.2.8. 8.
12.2.8.1. When Pulse wave (PW) and Continuous wave (CW)
12.2.8.1.1. have the same
12.2.9. 9.
12.2.9.1. Spatial considerations
12.2.9.1.1. SP
12.2.9.1.2. SA
12.2.10. 10.
12.2.10.1. Temporal considerations
12.2.10.1.1. TP
12.2.10.1.2. Im
12.2.10.1.3. PA
12.2.10.1.4. TA
12.3. Terms
12.3.1. Phase difference
12.3.1.1. The relative property to two or more waves.
12.3.1.1.1. The time interval by which a wave leads by or lags by another wave
12.3.1.2. It is calculated between waves that are passing through the same space.
12.3.1.3. This is also called as “Phase angle” or “Phase offset”.