OBJECTIVES

  1. List the acoustic variables and their units.

    1. Pressure (Pa), Density: (kg/cm³), Distance: (mm/cm)

  2. List the acoustic parameters and their units

    1. Period (microseconds), Frequency (Hz), Wavelength (mm), Amplitude (dB) , Power (watts, dB), Intensity (W/m²), Speed of Sound (m/s)

  3. Describe the units associated with the acoustic parameters.

    1. Period: microseconds (µs) - the time taken for one complete cycle of the wave. Frequency: (Hz) - the number of cycles per second of the wave. Wavelength: millimeters (mm) - the distance between successive crests of the wave. Amplitude: (Pascals, cm, g/cm³, dB) - a logarithmic measure of the sound intensity. Power: watts (W), decibels (dB) - the rate at which energy is transferred by the sound wave.Intensity: watts per square meter (W/m²) - the power per unit area carried by the wave. Speed of Sound: meters per second (m/s) - the speed at which sound waves propagate through a medium.

  4. Explain the relationship between frequency and period.

    1. Period and frequency are inversely related to each other. As the frequency of a wave increases, the period, which is the time taken for one complete cycle of the wave, decreases.

  5. List the 3 bigness parameter and their units.

    1. Amplitude (dB), Power (W), Intensity (W/cm³)

  6. Compare what happens to amplitude, power, and intensity if one changes.

    1. Power is related to the amplitude squared. Intensity is related to the amplitude squared. Power is related to the intensity.

  7. Describe the relationship between wavelength and frequency.

    1. Wavelength and frequency are inversely related. As the wavelength increases, the frequency decreases, and vice versa.

  8. Summarize speed of sound in various tissues from slowest to fastest and include at least 6 different types of tissues (Ch3).

    1. Air, Lung, Fat, Soft tissue, Tendon, Bone.

  9. Explain the relationship between pulse duration and image quality.

    1. Shorter duration pulses because they create images of greater accuracy.

  10. Describe the relationship between pulse duration and spatial pulse length.

    1. Pulse duration is the time a pulse is “on” and is typically measured in microseconds. Spatial pulse length is the distance of the pulse from end to end, and it is typically measured in millimeters.

  11. Describe the relationship between imaging depth and pulse repetition period (PRP).

    1. Directly related, so when imaging depth increases, PRP decreases.

  12. Describe the relationship between imaging depth and pulse repetition frequency (PRF).

    1. Inversely related. When imaging depth increases, PRF decreases.

  13. Describe the relationship between duty factor and listening time.

    1. Lower duty factor, more listening time, Higher duty factor, less listening.

  14. Produce a list of intensities from highest to lowest and indicate which is related to tissue heating.

    1. SPTP, Imax, SPPA, SPTA, SATA

  15. Explain the 3dB rule and list the numeric values of dB up to 60 dB.

    1. Decibels describe two intensities and their relative chandes.

    2. 3db=2x, 6dB=4x, 9dB=8x, 19dB=10, 20dB=100x, 30dB=1000x, 40dB=10,000x, 60dB=1,000,000x

  16. List the 2 factors of attenuation and list the 3 sources of attenuation.

    1. FACTORS: path length, frequency of sound

    2. SOURCES: absorption, scattering, reflection

  17. List and define the 2 forms of reflection.

    1. Specular (reflects from smooth, large surfaces at an angle), diffuse (reflects non-smooth/ irregular surface, radiates in more than one direction)

  18. Describe impedance mismatch and its importance as it relates to reflection.

    1. Impedance

  19. Explain what must occur in order for reflection to occur.

    1. Different impedances

  20. Explain what must occur in order for refraction to occur.

    1. Oblique incidence and different propagation speeds.

  21. Explain the 13µs rule.

    1. Sound that travels in soft tissue every 13 microseconds.

  22. Describe the piezoelectric effect.

    1. the property of certain materials to create voltage when they are mechanically deformed or when pressure is applied to them.

  23. Explain how the thickness of the element affects the frequency of a transducer.

    1. Thick crystal, low frequency; thin crystal, high frequency

  24. List the 3 consequences of using backing material.

    1. Low Q-factor, decreased sensitivity, and wide bandwidth

  25. Describe how the speed of sound in the PZT and the frequency of the sound beam are related.

    1. Directly related; high-speed PZT, high frequency

  26. Explain the relationship between frequency and thickness of the transducer crystal.

  27. Explain the relationship between crystal diameter and near zone length and/or focal depth. 

    1. smaller diameter PZT, shallower focus and larger diameter PZT, deeper focus

  28. Compare and contrast (long/short) pulse length, (high/low) frequency, and (poor/good) axial resolution.

    1. Short pulse length, high frequency, and good axial resolution, Long pulse length, low frequency, and poor axial resolution.

  29. List the 4 modifications that happen during focusing.

    1. beam diameter in near field and focal zone is reduced

    2. focal depth is shallower

    3. beam diameter in the far zone increases

    4. focal zone is smaller

  30. Define the term axial resolution and lateral resolution.

    1. axial resolution: going along the beam path

    2. lateral resolution: going side-to-side, perpendicular beam path

  31. List what is found on the X, Y and Z axis of an A mode display, B mode display and M-mode display (see page 163-Table 11.1).

    1. A mode: x-axis, depth and y-axis amplitude

    2. B mode: x-axis depth and z-axis amplitude

    3. M mode: x-axis time and y-axis depth

  32. Explain the technique of dynamic aperture.

    1. can be used to make a sound beam narrow over a greater range of depths and thus optimize lateral resolution

  33. Explain slice thickness or elevational resolution.

    1. Slice thickness is measured in a direction perpendicular to the imaging plane.