1 / 94

Cardiovascular Principles

Cardiovascular Principles. Ultrasound Physics and Instrumentation. Wave. Definition: Disturbance or variation that transfers energy progressively form point to point in a medium. Wave. Key words: Disturbance Variation Transfer of Energy. Sound Wave.

shel
Download Presentation

Cardiovascular Principles

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Cardiovascular Principles Ultrasound Physics and Instrumentation

  2. Wave Definition: Disturbance or variation that transfers energy progressively form point to point in a medium.

  3. Wave • Key words: • Disturbance • Variation • Transfer of Energy

  4. Sound Wave Definition: Mechanical radiant energy that is transmitted by longitudinal pressure waves through a medium.

  5. Sound Wave

  6. Sound Wave • Variables • Acoustic Variables

  7. Acoustic Variables • Pressure • Density • Temperature • Particle Motion = Displacement

  8. Acoustic Variable Variable versus Time High Low Variable Time

  9. Acoustic Variable

  10. Acoustic Variable Variable versus Time Pressure Time

  11. Acoustic Variable Variable versus Time Pressure T Time Period is the time it takes for a sound wave to complete one cycle of oscillation.

  12. Acoustic Variable The period is inversely proportional to the frequency Period = T Frequency = f T = 1 f Period versus Frequency

  13. Acoustic Variable Variable versus Time Pressure T Time

  14. Acoustic Variable Variable versus Time Pressure T Time

  15. Wavelength Variable versus Distance Pressure l Distance

  16. Wavelength Wavelength is the space or distance over which a complete wave cycle occurs.

  17. Wave Equation V = f l V = velocity f = frequency l = wavelength

  18. Wave Equation

  19. Velocity Definition The velocity of sound is the speed with which a particular value of an acoustic variable moves.

  20. Velocity The Velocity is determined by the Bulk Modulus and the density of the medium.

  21. Velocity c = velocity B = Bulk Modulus r = Density

  22. Velocity The Bulk Modulus is a measure of the stiffness of the medium.

  23. Velocity

  24. Range Equation Distance = velocity x time

  25. Range Equation Velocity = speed of sound in soft tissue. Distance = reflector distance. Time = time it takes the sound wave to reach reflector

  26. Range Equation Time that can be measured is the go – return time The actual time = go-return time 2

  27. Range Equation Reflector distance = velocity x go-return time 2

  28. Amplitude Definition: Maximum variation in an acoustic variable. It is the difference between the resting value and the maximum value of an acoustic variable

  29. Amplitude A Pressure Time

  30. Amplitude • Amplitude decreases as the ultrasound wave travels in tissue. Increasing the amplitude • Increases depth of penetration • Increases the sensitivity

  31. Power • The rate of doing work • Units – Watts • Determine by the Ultrasound System • Power is proportional to amplitude squared.

  32. Intensity Intensity is the concentration of power in a sound beam. Intensity = power area

  33. Pulsed Ultrasound A C A = PRP B = Pulse Duration C= Reception Time B

  34. Pulsed Ultrasound Pulsed Duration = period x cycles per pulse PRP = the time form the beginning of one pulse to the beginning of the next. PRP = 1 PRF

  35. Pulsed Ultrasound • # of pulses per second is determined by • Strength of the excitation voltage. • The damping characteristics

  36. Pulsed Ultrasound PRF = # of pulses per second Duty Factor = PD PRP

  37. Pulsed Ultrasound SPL Distance

  38. Pulse Ultrasound Spatial Pulse Length = SPL SPL = wavelength x cycles per pulse SPL determines the axial resolution

  39. Intensity Values The area of the beam is not uniformed. therefore the Intensity in the sound beam is not uniform. Beam Cross-sectional Profile

  40. Intensity Values Spatial – refers to the space variation Temporal – refers to the time variation

  41. Intensity Values Peak – the maximum value Average – the mean value

  42. Intensity Values Spatial Peak Intensity is measured along the central beam axis where the beam area is narrowest. Spatial Average intensity is the average intensity in the sound beam and is usually measured at the transducer surface.

  43. Intensity Value Temporal Peak Intensity is the maximum intensity when the sound is on. Temporal average is the average intensity during the whole pulse cycle. Pulsed Average Intensity is the average intensity during the duration of the pulse only. TP > PA > TA

  44. Pulsed UltrasoundTemporal Intensities C A A = Temporal peak B = Pulse Average C= Temporal Average B

  45. Intensity Values TP SP PA SA TA

  46. Intensity Values

  47. Intensity Value TA Intensity = Pulsed Average Intensity x Duty factor DF = TA/PA For Continuous Wave Ultrasound the DF = 1

  48. Intensity Value The SP/SA factor describes the distribution of intensity in an ultrasound beam in space: SP/SA factor = SP Intensity SA Intensity SP/SA factor = BUR (Beam Uniformity Ratio)

  49. Attenuation Decibel Unit

  50. Logarithm Logarithm to the base 10 of a number is equal to the number of 10 that must be multiplied together to result in that number. Or It is the power to which 10 must be raised to produce that number.

More Related