Understanding ultrasound

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Understanding ultrasound

  1. 1. ULTRA SOUND<br />IN<br />MEDICAL IMAGING<br />Mohammad Amir<br />Final Year MBBS<br />JJMMC<br />
  2. 2. WHAT IS MEDICAL IMAGING<br />?<br />
  3. 3. MEDICAL IMAGING: The techniques and processes used to create image of the internal as well as external human body parts for clinical purpose .<br />
  4. 4. Why medical imaging is required?<br /><ul><li>Medical imaging provides a pictorial status of particular organ which is to be treated
  5. 5. It makes a surgical targets more clear and precise
  6. 6. It provides a pictorial status of fetus development right from 4th weak to 36th- 38th week
  7. 7. It make therapeutic targets easy to detect and treat </li></li></ul><li>TYPES OF MEDICAL IMAGING WIDELY USED <br /><ul><li>X-RAY
  8. 8. MAMOGRAPHY
  9. 9. CONTRAST RADIOGRAPHY
  10. 10. ULTRA SOUND
  11. 11. CT SCAN
  12. 12. MRI
  13. 13. SPECT(SINGLE PHOTON EMMISION TOMOGRAPHY)
  14. 14. PET(POSITRON EMISSION TOMOGRAPHY)</li></li></ul><li><ul><li>PIZOELECTRIC IS DEVELOPED BY THE CURIES IN 1880 USING NATURAL QUARTZ
  15. 15. SONAR was first time used in war time 1940
  16. 16. Diagnosis medical application in use since late 1950’s</li></li></ul><li>WHAT IS ULTRA SOUND<br />?<br />
  17. 17. ULTRA SOUND : MEDICAL DEFINATION!!!<br /><ul><li>DIGNOSTIC MEDICAL ULTRASOUND IS THE USE OF HIGH FREQUENCY SOUND TO AID IN DIGNOSIS AND TREATMENT OF PATIENT.
  18. 18. FREQUENCY RANGES USED IN MEDICAL ULTRASOUND ARE 2-15 MHZ</li></li></ul><li>
  19. 19.
  20. 20. Ultrasound Production<br /><ul><li>Transducer contains piezoelectric elements/crystals which produce the ultrasound pulses (transmit 1% of the time)
  21. 21. These elements convert electrical energy into a mechanical ultrasound wave</li></li></ul><li>PULSE<br /><ul><li> Pulse of sounds is send to soft tissues
  22. 22. Sound interaction with soft tissues= bio effect
  23. 23. Pulsing is determined by transducer or probe crystal and ins not operated or control</li></li></ul><li>ECHO<br /><ul><li>ECHO IS PRODUCED BY SOFT TISSUES
  24. 24. TISSUE INTRACTION WITH SOUND = ACOUSTIC PROPAGATION PROPERTIES
  25. 25. ECHOES ARE RECEIVED BY THE TRANSDUCER CRYSTAL
  26. 26. ECHOES ARE INTRPRETED AND PROCESSED BY ULTRA SOUND MACHINE</li></li></ul><li>Refraction<br />reflective<br />refraction<br />Scattered<br />echoes<br />Incident <br />Angle of incidence = angle of reflection<br />
  27. 27. The Returning Echo<br /><ul><li>Reflected echoes return to the scan head where the piezoelectric elements convert the ultrasound wave back into an electrical signal
  28. 28. The electrical signal is then processed by the ultrasound system</li></li></ul><li>FACTORS AFFECTING ULTRASOUND<br /><ul><li>FREQUENCY
  29. 29. WAVELENGTH
  30. 30. BANDWIDTH
  31. 31. ATTENUATION
  32. 32. TIME GAIN COMPENSATION</li></li></ul><li>Piezoelectric Crystals<br /><ul><li>The thickness of the crystal determines the frequency of the scan head</li></ul>High Frequency<br />10 MHz<br />Low Frequency<br />3 MHz<br />
  33. 33. FREQUENCY AND RESOLUTION<br /> HIGH FREQUENCY = HIGH RESOLUTION <br />
  34. 34. DYNAMIC RANGE<br />
  35. 35. M-MODE<br />B-MODE<br />
  36. 36. Power Doppler<br />Color Doppler<br />
  37. 37. MACHINE COMPONENT<br /><ul><li>Keyboard /cursor
  38. 38. Diskstorage device
  39. 39. Printer</li></li></ul><li>
  40. 40.
  41. 41. Transducer Design<br />Size, design and <br />frequency<br />depend upon the<br />examination<br />
  42. 42. Image Formation<br /><ul><li>Electrical signal produces ‘dots’ on the screen
  43. 43. Brightness of the dots is proportional to the strength of the returning echoes
  44. 44. Location of the dots is determined by travel time. The velocity in tissue is assumed constant at 1540m/sec
  45. 45. Distance = Velocity Time</li></li></ul><li>Image Formation<br /> ‘B’ mode<br />
  46. 46. Interactions of Ultrasound with <br />Tissue<br /><ul><li>Acoustic impedance (AI) is dependent on the density of the material in which sound is propagated</li></ul> - the greater the impedance the denser the material.<br /><ul><li>Reflections comes from the interface of different AI’s
  47. 47. greater  of the AI = more signal reflected
  48. 48. works both ways (send and receive directions)</li></li></ul><li>Attenuation & Gain<br />Sound is attenuated by tissue<br />More tissue to penetrate = more attenuation of signal<br />Compensate by adjusting gain based on depth<br />near field / far field<br />AKA: TGC<br />
  49. 49. Ultrasound Gain<br />Gain controls<br />receiver gain only<br />does NOT change power output<br />think: stereo volume<br />Increase gain = brighter<br />Decrease gain = darker<br />
  50. 50. Balanced Gain<br />Gain settings are important to obtaining adequate images.<br />bad far field<br />bad near field<br />balanced<br />
  51. 51. Reflected Echo’s<br />Strong Reflections = White dots<br />Diaphragm, tendons, bone<br /> ‘Hyperechoic’<br />
  52. 52. Reflected Echo’s<br /> Weaker Reflections = <br />Grey dots<br />Most solid organs, <br />thick fluid – ‘isoechoic’ <br />
  53. 53. Reflected Echo’s<br />No Reflections = Black dots<br />Fluid within a cyst, urine, blood<br />‘Hypoechoic’ or echofree<br />
  54. 54. Ultrasound Beam Profile<br />Beam comes out as a slice<br />Beam Profile<br />Approx. 1 mm thick<br />Depth displayed – user controlled<br />Image produced is “2D”<br />tomographic slice<br />assumes no thickness<br />You control the aim<br />1mm<br />
  55. 55. Goal of an Ultrasound System<br />The ultimate goal of any ultrasound system is to make like tissues look the same and unlike tissues look different<br />
  56. 56. Accomplishing this goal depends upon...<br />Resolving capability of the system<br />axial/lateral resolution<br />spatial resolution<br />contrast resolution<br />temporal resolution<br />Processing Power<br />ability to capture, preserve and display the information<br />
  57. 57. Ultrasound Applications<br />Visualisation Tool:<br />Nerves, soft tissue masses <br />Vessels - assessment of position, size, patency<br />Ultrasound Guided Procedures in real time – dynamic imaging; central venous access, nerve blocks<br />
  58. 58. Imaging<br />Know your anatomy – Skin, muscle, tendons, nerves and vessels <br />Recognise normal appearances – compare sides!<br />
  59. 59. Skin, subcutaneous tissue<br />Epidermis<br />Loose connective tissue and subcutaneous fat is hypoechoic<br />Muscle interface<br />Muscle fibres interface<br />Bone<br />
  60. 60.
  61. 61.
  62. 62.
  63. 63. conclusion<br /><ul><li>Imaging tool – Must have the knowledge to understand how the image is formed
  64. 64. Dynamic technique
  65. 65. Acquisition and interpretation dependant upon the skills of the operator.</li></li></ul><li>
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