Sound Wave Parameters: Period
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Questions and Answers

What happens to intensity when there is a decrease in area?

  • It becomes zero
  • It remains the same
  • It decreases
  • It increases (correct)

    • What is the term for the weakening of an ultrasound pulse as it travels through a medium?

  • Diffraction
  • Refraction
  • Frequency shift
  • Attenuation (correct)

    • What is amplitude in the context of sound waves?

  • The total amount of variation that occurs in an acoustic variable
  • The average amount of variation that occurs in an acoustic variable
  • The minimum amount of variation that occurs in an acoustic variable
  • The maximum amount of variation that occurs in an acoustic variable (correct)

    • What is the purpose of the 'dead time' in pulsed ultrasound?

    <p>To receive the echoes</p> Signup and view all the answers

    What is the term for the 'on' or 'transmit' time in pulsed ultrasound?

    <p>Cycle</p> Signup and view all the answers

    What is the frequency bandwidth in pulsed ultrasound?

    <p>A range of frequencies</p> Signup and view all the answers

    What type of ultrasound is predominantly used in echocardiography?

    <p>Continuous wave</p> Signup and view all the answers

    What is the period of a sound wave if one cycle takes 0.2 μs to occur?

    <p>0.2 μs</p> Signup and view all the answers

    What type of images can pulsed wave transducers generate?

    <p>Both real-time and static images</p> Signup and view all the answers

    What is the unit of measurement for wavelength?

    <p>Meters</p> Signup and view all the answers

    What is the frequency of a sound wave if one cycle takes 0.2 μs to occur?

    <p>5 MHz</p> Signup and view all the answers

    What determines the period of a sound wave?

    <p>The sound source</p> Signup and view all the answers

    What is the wavelength of a sound wave if the speed of sound is 1.54 mm/μs and the frequency is 5 MHz?

    <p>0.31 mm</p> Signup and view all the answers

    What is the effect of shorter-wavelength sound waves on ultrasound images?

    <p>They increase the spatial resolution</p> Signup and view all the answers

    What is the propagation speed of a sound wave dependent on?

    <p>The medium it is traveling through</p> Signup and view all the answers

    Can the wavelength of a sound wave be controlled by the sonographer?

    <p>No</p> Signup and view all the answers

    What is the material in which the average propagation speed of sound is the fastest?

    <p>Bone</p> Signup and view all the answers

    What is the amplitude of a sound wave indicative of?

    <p>The strength or intensity of a sound wave</p> Signup and view all the answers

    What is the unit of power in diagnostic ultrasound?

    <p>Milliwatts (mW)</p> Signup and view all the answers

    What happens to the intensity of a sound wave when the area is increased?

    <p>It decreases</p> Signup and view all the answers

    What is the unit of intensity in ultrasound?

    <p>Milliwatts per centimeter squared (mW/cm2)</p> Signup and view all the answers

    What is the purpose of the power of a sound wave in ultrasound?

    <p>To facilitate the displacement of particles within the medium</p> Signup and view all the answers

    What is the relationship between the power of a sound wave and its ability to displace particles?

    <p>The higher the power, the greater the wave's capacity to displace particles</p> Signup and view all the answers

    What is the rate at which energy passes through a unit area in ultrasound?

    <p>Intensity</p> Signup and view all the answers

    What is the unit of Pulse Repetition Period (PRP)?

    <p>Milliseconds (ms) or any unit of time</p> Signup and view all the answers

    What is the effect of increasing the imaging depth on Pulse Repetition Frequency (PRF)?

    <p>PRF decreases</p> Signup and view all the answers

    What is the relationship between Pulse Repetition Period (PRP) and Pulse Repetition Frequency (PRF)?

    <p>PRP is inversely proportional to PRF</p> Signup and view all the answers

    What is the typical range of Pulse Repetition Period (PRP) values in clinical imaging?

    <p>100 microseconds to 1 millisecond</p> Signup and view all the answers

    What is the formula to calculate Pulse Duration (PD)?

    <p>PD = n × T</p> Signup and view all the answers

    What is the effect of decreasing the number of cycles in a pulse on Pulse Duration (PD)?

    <p>PD decreases</p> Signup and view all the answers

    What is the duty factor (DF) of an ultrasound system?

    <p>The fraction of the PRP that the sound is on</p> Signup and view all the answers

    What is the formula to calculate the period of a pulse?

    <p>Period = 1 ÷ frequency</p> Signup and view all the answers

    What is the purpose of the listening time in pulsed ultrasound systems?

    <p>To receive echoes that will form a scan line on the instrument display</p> Signup and view all the answers

    What is the typical range of duty factors for sonography?

    <p>0.1% to 1.0%</p> Signup and view all the answers

    What is the formula to calculate the duty factor (DF)?

    <p>DF = Pulse duration / Pulse repetition period</p> Signup and view all the answers

    What is the duty factor for an ultrasound examination with a pulse duration of 2 µs and a pulse repetition period of 1 ms?

    <p>0.002</p> Signup and view all the answers

    What is the spatial pulse length (SPL) dependent on?

    <p>Wavelength and number of cycles in the pulse</p> Signup and view all the answers

    What determines axial resolution in ultrasound imaging?

    <p>Spatial pulse length (SPL)</p> Signup and view all the answers

    What happens to the spatial pulse length (SPL) as frequency increases?

    <p>It decreases</p> Signup and view all the answers

    What is the spatial pulse length (SPL) equal to?

    <p>Wavelength multiplied by the number of cycles in the pulse</p> Signup and view all the answers

    Study Notes

    Sound Wave Parameters: Period

    • The period (T) is determined by the sound source and cannot be altered by the sonographer.
    • Each cycle occurs in a specific time, and the period is the time for one cycle to occur.
    • If one cycle takes 0.2 μs to occur, the frequency is 5 MHz.

    Sound Wave Parameters: Wavelength

    • Wavelength (λ) is the length of a cycle in space.
    • Units for wavelength are measured in meters, millimeters, or any standard unit of length.
    • Typical values in soft tissue range from 0.1 to 0.8 mm.
    • The wavelength cannot be modified by the sonographer.
    • Wavelength is calculated as Speed divided by Frequency (λ = c / f).

    Sound Wave Parameters: Propagation Speed

    • Propagation speed (c) refers to the rate at which a sound wave moves through a medium.
    • Within a specific medium, sound waves travel at a consistent speed, regardless of their frequency.
    • The speed of sound wave propagation varies across different mediums.
    • The average propagation speed of sound in tissues:
      • Air: 330 m/sec
      • Fat: 1450 m/sec
      • Water: 1480 m/sec
      • Soft tissue: 1540 m/sec
      • Bone: 4100 m/sec

    Sound Wave Parameters: Amplitude

    • Amplitude is created by the number of molecules displaced by a vibration.
    • Amplitude is indicative of the strength or intensity of a sound wave.
    • Amplitude is typically measured in units of pressure, such as Mega Pascals (MPa).

    Sound Wave Parameters: Power

    • Power is the rate at which work is performed or energy is transferred.
    • In ultrasound, power refers to the generation of ultrasound waves by the transducer and their propagation through tissues.
    • The standard unit of power is the Watt (W).
    • Power in diagnostic ultrasound is commonly expressed in milliwatts (mW).

    Sound Wave Parameters: Intensity

    • Intensity (I) is the rate at which energy passes through a unit area.
    • Intensity is equal to the power in a wave divided by the area (A) over which the power is spread.
    • Intensity units include milliwatts per centimeter squared (mW/cm²) and watts per centimeter squared (W/cm²).

    Pulsed Wave

    • A pulse has a distinct beginning and end.
    • Pulsed ultrasound comprises two main components: The Cycle (the "on" or "transmit" time) and The Dead Time (the "off" or "receive" time).
    • Pulsed transducers are designed to generate multiple, sequential, short pulses, allowing for the simultaneous use of the same crystal or group of crystals for both sound transmission and echo reception.

    Pulsed Repetition Frequency (PRF)

    • Pulse Repetition Frequency (PRF) refers to the number of sound pulses generated by the transducer per second.
    • The determination of PRF is attributed to the sound source and can be adjusted by the sonographer.
    • There is an inverse relationship between imaging depth and PRF, meaning as imaging depth increases, PRF decreases.

    Pulse Repetition Period (PRP)

    • Pulse-repetition period (PRP) refers to the time from the beginning of one pulse to the beginning of the next one.
    • PRP is the reciprocal of Pulse Repetition Frequency (PRF), expressed in milliseconds or any unit of time (PRP = 1 / PRF).
    • The determination of PRP is influenced by the sound source, and it can be adjusted by the operator.

    Pulse Duration (PD)

    • Pulse duration (PD) is the time that it takes for one pulse to occur.
    • PD is equal to the period (the time for one cycle) times the number of cycles in the pulse (n) and is expressed in microseconds (PD = n × T).
    • Sonographic pulses are typically two or three cycles long, while Doppler pulses are typically 5 to 30 cycles long.

    Duty Factor (DF)

    • The duty factor is the percentage of time that the ultrasound system transmits sound.
    • DF is the fraction of the PRP that the sound is on.
    • Typical DFs for sonography are in the range of 0.1% to 1.0%, and for Doppler ultrasound, the range is 0.5% to 5.0%.
    • The sonographer can adjust the duty factor when changing imaging depth.

    Spatial Pulse Length (SPL)

    • SPL is the length of a pulse from front to back.
    • SPL is equal to the length of each cycle times the number of cycles in the pulse (SPL = n × wavelength).
    • SPL determines axial resolution.
    • Because wavelength decreases with increasing frequency, SPL decreases with increasing frequency.

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    Description

    This quiz covers the concept of period in sound waves, including its representation, calculation, and relation to frequency.

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