Ultrasound Wavelength and Frequency
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Questions and Answers

What does Pulse Repetition Frequency (PRF) refer to?

  • The percentage of time the ultrasound system transmits sound
  • The time it takes for one pulse to occur
  • The time between two consecutive sound pulses
  • The number of sound pulses generated per second (correct)
  • What happens to PRF when imaging depth increases?

  • It becomes irrelevant
  • It increases
  • It remains constant
  • It decreases (correct)
  • What is the relationship between PRP and PRF?

  • PRP is directly proportional to PRF
  • PRP is the square root of PRF
  • PRP is the reciprocal of PRF (correct)
  • PRP is the square of PRF
  • What is the unit of Pulse Repetition Period (PRP)?

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

    What determines Pulse Duration (PD)?

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

    What happens to Pulse Duration (PD) if the frequency is increased?

    <p>It decreases</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 duty factor (DF)?

    <p>The percentage of time the ultrasound system transmits sound</p> Signup and view all the answers

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

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

    What happens to intensity when the area of an ultrasound pulse is decreased?

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

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

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

    What is the maximum amount of variation that occurs in an acoustic variable?

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

    What is the definition of a pulse in ultrasound?

    <p>A wave with a distinct beginning and end</p> Signup and view all the answers

    What are the two main components of pulsed ultrasound?

    <p>The Cycle and the Dead Time</p> Signup and view all the answers

    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 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 limitation of continuous wave ultrasound?

    <p>It is incapable of creating anatomic images</p> Signup and view all the answers

    What is the frequency of a cycle that takes 0.2 millionths of a second to occur?

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

    What is the unit of measurement for wavelength?

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

    Can the wavelength be modified by the sonographer?

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

    What is the formula to calculate wavelength?

    <p>Wavelength = Speed ÷ Frequency</p> Signup and view all the answers

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

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

    What is the propagation speed of sound waves in a medium?

    <p>It is the same for all frequencies</p> Signup and view all the answers

    What determines the speed of sound wave propagation?

    <p>Medium through which it travels</p> Signup and view all the answers

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

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

    Why is wavelength an important parameter in ultrasound imaging?

    <p>It influences the diagnostic quality of ultrasound images</p> Signup and view all the answers

    What is the characteristic of normal incidence in ultrasound?

    <p>The ultrasound path is perpendicular to the boundary.</p> Signup and view all the answers

    What factor affects the degree of reflection and refraction in ultrasound?

    <p>Acoustic impedance differences of the two media.</p> Signup and view all the answers

    What is the process of conversion of sound energy into heat within a medium called?

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

    What is the result of slower molecular relaxation in a medium?

    <p>Increased absorption</p> Signup and view all the answers

    What type of reflection occurs at large and smooth interfaces?

    <p>Specular reflection</p> Signup and view all the answers

    What is the result of higher frequencies in ultrasound?

    <p>More heat production</p> Signup and view all the answers

    What is the characteristic of non-specular reflection?

    <p>The ultrasound beam is scattered in multiple directions.</p> Signup and view all the answers

    What is the result of the acoustic impedance difference between two media?

    <p>Increased reflection</p> Signup and view all the answers

    What is the characteristic of specular reflection in ultrasound imaging?

    <p>The image is hyperechoic (brighter).</p> Signup and view all the answers

    What is the result of less uniform tissue in diffuse reflection?

    <p>A more hypoechoic image</p> Signup and view all the answers

    What is the reason for the bright signal in the sonogram of the bone?

    <p>The bone is highly reflective of sound waves</p> Signup and view all the answers

    What is the term for the image artifacts produced by backscatter?

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

    What is the condition for refraction to occur?

    <p>The sound wave hits the boundary at an oblique angle</p> Signup and view all the answers

    What is the law that defines the refraction of sound waves?

    <p>Snell's Law</p> Signup and view all the answers

    What is the term for the way sound waves spread out in different directions?

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

    What is the result of the difference in propagation speeds of sound in different media?

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

    What is the factor that determines the direction of the refracted beam?

    <p>The speed of sound in the second medium</p> Signup and view all the answers

    What is the term for the reflection of ultrasound waves back to the transducer?

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

    Study Notes

    Sound Wave Parameters

    • A cycle takes 0.2 millionths of a second to occur, which means 5 million cycles occur in 1 second, resulting in a frequency of 5 MHz.
    • Wavelength (λ) is the length of a cycle in space and is typically measured in meters, millimeters, or any standard unit of length.
    • Wavelength ranges from 0.1 to 0.8 mm in soft tissue and cannot be modified by the sonographer.
    • Wavelength is calculated as Speed divided by Frequency: λ (mm) = c (mm/μs) ÷ f (MHz).
    • Wavelength is a crucial parameter that influences the diagnostic quality of ultrasound images, with shorter-wavelength sound waves having superior spatial resolution but less penetration.

    Propagation Speed

    • Propagation speed (c) refers to the rate at which a sound wave moves through a medium.
    • Sound waves travel at a consistent speed within a specific medium, regardless of their frequency.
    • The speed of sound wave propagation varies across different mediums.
    • A decrease in area (focusing) increases intensity because power is more concentrated.
    • Attenuation is the weakening of an ultrasound pulse as it travels through a medium.

    Pulsed Wave

    • A pulse, by definition, must have 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 wave transducers are responsible for generating all types of ultrasound diagnostic images, including both real-time and static.
    • The frequency bandwidth of a pulsed transducer emits ultrasound waves that span a variety of frequencies.

    Continuous Wave (CW)

    • Continuous wave (CW) ultrasound is predominantly employed in echocardiography for acquiring CW Doppler information.
    • Continuous wave sound is incapable of creating anatomic images.

    Pulse Repetition Frequency (PRF) and Pulse Repetition Period (PRP)

    • Pulse Repetition Frequency (PRF) refers to the number of sound pulses generated by the transducer per second.
    • There is an inverse relationship between imaging depth and PRF, meaning as imaging depth increases, PRF decreases.
    • Pulse Repetition Period (PRP) is the time from the beginning of one pulse to the beginning of the next one and is the reciprocal of PRF: PRP = 1 / PRF.
    • The determination of PRP is influenced by the sound source and 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(μs) = n × T(μs).
    • 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.

    Types of Incidence

    • Normal Incidence occurs when the ultrasound path is perpendicular to the boundary.
    • Oblique Incidence occurs when the ultrasound beam strikes the interface between two media at an angle other than 90°.

    Incident Sound in Ultrasound

    • The degree of reflection and refraction is influenced by the acoustic impedance differences of the two media.

    Factors Contributing to Attenuation

    • Absorption is the conversion of sound energy into heat within a medium.
    • Factors affecting absorption include relaxation time and frequency.
    • Reflection is the redirection of part of the ultrasound wave back towards the source.
    • The degree of reflection is influenced by the acoustic impedance difference between the two media.
    • Scattering refers to the way sound waves spread out in different directions when they encounter tissues with irregular surfaces or interfaces similar in size to the wavelength of the sound.
    • Refraction is the change in direction of a sound wave as it passes across a boundary between two different media at an oblique angle, not perpendicular to the boundary.

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    Description

    Quiz about ultrasound wavelengths, frequencies, and their relationships in soft tissue, including units of measurement and factors influencing wavelength.

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