Principles of ultrasound lecture utd

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  • PSLA Inadequate Depth\n
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  • Principles of ultrasound lecture utd

    1. 1. PRINCIPLES OFULTRASONOGRAPHY Pierre Kory, MPA, MD Assistant Professor, Albert Einstein College of Medicine Pulmonary and Critical Care Division Beth Israel Medical Center, New York
    2. 2. OUTLINE• Evolution of Bedside Ultrasonography• Ultrasound Physics Explained• Image Representation• Image Interpretation• Introduction to Equipment• Image Acquisition and Control (“Knobology”)
    3. 3. EVOLUTION OF CRITICAL CARE ULTRASONOGRAPHY• Ultrasound used in medicine for over 60 years • Now one of the most widely used diagnostic tools in medicine • Traditional domain of radiologists - rapidly changing • U/S guided vascular access now standard of care • ED physicians led point-of-care ultrasound uses • Technology also a factor: • handheld/portable ultrasound with excellent image quality, user friendly interface • High utility for confirming common, easily recognized diagnoses • DVT, hydronephrosis, pleural effusions, pericardial effusions, pulmonary edema are just a few examples
    4. 4. WHAT IS ULTRASOUND?• High frequency sound (pressure) waves • >20,000 HZ (2kHz) upper limit human ear • 2MHz - 10MHz medical diagnostic frequency range • Ultrasound waves are created by a vibrating crystal within a ceramic probe • Waves travel through tissue and are partly reflected at each tissue interface • “Piezoelectric” principle - electric current causes crystal to vibrate, returning waves create electric current
    5. 5. HOW DOES ULTRASOUND WORK?
    6. 6. HOW DOES ULTRASOUND WORK?• Crystal inside probe, wired to power source
    7. 7. HOW DOES ULTRASOUND WORK?• Crystal inside probe, wired to power source• Electric CURRENT thus applied to crystal
    8. 8. HOW DOES ULTRASOUND WORK?• Crystal inside probe, wired to power source• Electric CURRENT thus applied to crystal• Crystal then vibrates = ultrasound wave leaves
    9. 9. HOW DOES ULTRASOUND WORK?• Crystal inside probe, wired to power source• Electric CURRENT thus applied to crystal• Crystal then vibrates = ultrasound wave leaves• Wave propagates into body & through tissue
    10. 10. HOW DOES ULTRASOUND WORK?• Crystal inside probe, wired to power source• Electric CURRENT thus applied to crystal• Crystal then vibrates = ultrasound wave leaves• Wave propagates into body & through tissue• At each tissue plane - a portion of wave reflected • Leaves a “trail” of “echoes”• Each reflection returns and hits crystal
    11. 11. HOW DOES ULTRASOUND WORK?• Crystal inside probe, wired to power source• Electric CURRENT thus applied to crystal• Crystal then vibrates = ultrasound wave leaves• Wave propagates into body & through tissue• At each tissue plane - a portion of wave reflected • Leaves a “trail” of “echoes”• Each reflection returns and hits crystal• Crystal vibrates - creates a CURRENT to unit
    12. 12. HOW DOES ULTRASOUND WORK?• Crystal inside probe, wired to power source• Electric CURRENT thus applied to crystal• Crystal then vibrates = ultrasound wave leaves• Wave propagates into body & through tissue• At each tissue plane - a portion of wave reflected • Leaves a “trail” of “echoes”• Each reflection returns and hits crystal• Crystal vibrates - creates a CURRENT to unit• Echoes have discrete amplitudes and are thus assigned a specific “brightness” and location on a screen!
    13. 13. • or “Brightness Mode”) (B- MODE/ 2D ULTRASONAGRAPHY • multiple lines of interrogation over wide area, each returning echo is assigned a brightness on a grey scale and a location on the screen • Screen location of “brightness”/echo - depends on TIME wave took to return and DIRECTION it returned from
    14. 14. IMAGE CREATION• “SWEEPING” waves across a sector to form 2D image • “TALKING” • Sends out pulses side-by-side aimed (“steered”) from a curvilinear probe face - covers a wide “arc” - allows for wide image from a small “window” • “LISTENING” • waits to receive the returning “echoes” (probe is actually listening 99% of the time)
    15. 15. IMAGE CREATION• “Echoes” have a wide range of amplitudes (“strengths”) • compressed into log format so can be displayed using a finite “gray scale” (range is too wide otherwise) • Allows for very weak signals to be represented alongside strong signals• Each amplitude is assigned a level on a “gray” scale for representation on the screen (256 color scale)• Reflections from objects far from transducer are amplified (they are too weak/dampened otherwise)
    16. 16. IMAGE CREATION• Image on screen is thus a PLOT of all the tiny reflections that return• PLOT is constantly “refreshed” for real-time imaging of moving organs (i.e heart) • screen is refreshed 25-50 times per second (fps - frames per second or “frame rate”
    17. 17. IMAGE INTERPRETATION• “ WHITE” areas represent “echogenic” structures • represent structures that transmit & reflect waves • Soft Tissue - muscles, fat, vessels, nodes, masses• “BLACK” areas represent areas that are anechoic • Fluid – transmits but does not reflect sound waves• “GREY” helps widen the representative scale of black/ white “brightnesses”• LINES – occur at boundary of two markedly different tissue reflectors - clear delineation of structures -
    18. 18. Tissue Characteristics of Ultrasound• Air – near total reflector (scatter reflector)• Fluid – near total propagation (no reflection)• Bone – near total reflection• Soft Tissue- partial propagator, partial reflector • reflects every time tissue impedance changes - every “interface” • ideal for ultrasound imaging!
    19. 19. EQUIPMENT• Portable Ultrasound Unit, Cart, Transducers, Conducting Gel --prevents air b/w skin/transducer • TRANSDUCERS - low and high frequency ranges, linear and phased array • 1.0 - 5.0 MHZ – general use, cardiac, lung, abdomen (“phased array” sector scanning) • 5.0 – 10 MHZ- superficial structures (vessels), linear images, no sector scanning 1 - 5 MHZ 5-10 MHZ range range
    20. 20. PROBE FREQUENCIES• determines optimal depth of penetration • HIGHER FREQUENCIES (> 5.0 MHZ) • lose energy faster so have less depth of penetration • provides much greater image resolution • SO, higher frequency (i.e 7.5 MHZ) better at short depths - good for vessels (superficial), “vascular probe” (linear) • Lower frequency (3.5MHZ) good for deeper depths - abdomen, heart - “general probe”
    21. 21. TRANSDUCER CONTROL• Pencil hold• Body position• Hand stabilization
    22. 22. TRANSDUCER/SCREEN MARKERS• Marker on probe corresponds to marker on screen • Probe marker determines edge of image on screen• Top part of screen image represents body part closest to probe • Sides of screen image depend on how probe is oriented (superior/inferior
    23. 23. SCREEN MARKER ORIENTATION• LUNG, ABDOMINAL,VASCULAR SCANNING • Screen Marker – UPPER LEFT • Probe Marker: – Lung – cephalad (12:00) – Abdominal, Vascular – cephalad or to patient’s right (12:00 or 9:00)• CARDIAC** • Screen Marker -- UPPER RIGHT • Probe marker : – multiple orientations, must memorize – always pointing cephalad or to pt’s left
    24. 24. Mini QUIZ - what happens to the Ultrasound Wave when it hits....
    25. 25. Mini QUIZ - what happens to the Ultrasound Wave when it hits.... • AIR ?
    26. 26. Mini QUIZ - what happens to the Ultrasound Wave when it hits.... • AIR ? • A LINES!! - COMPLETELY REFLECTED BACK TO PROBE - CANNOT “SEE” PAST AIR - You will see “A” lines or “Air Lines” - a reverberation artifact
    27. 27. Mini QUIZ - what happens to the Ultrasound Wave when it hits.... • AIR ? • A LINES!! - COMPLETELY REFLECTED BACK TO PROBE - CANNOT “SEE” PAST AIR - You will see “A” lines or “Air Lines” - a reverberation artifact • FLUID ?
    28. 28. Mini QUIZ - what happens to the Ultrasound Wave when it hits.... • AIR ? • A LINES!! - COMPLETELY REFLECTED BACK TO PROBE - CANNOT “SEE” PAST AIR - You will see “A” lines or “Air Lines” - a reverberation artifact • FLUID ? • BLACK!! - PROPAGATES THROUGH - thus, is a great window to see behind and around fluid
    29. 29. Mini QUIZ - what happens to the Ultrasound Wave when it hits.... • AIR ? • A LINES!! - COMPLETELY REFLECTED BACK TO PROBE - CANNOT “SEE” PAST AIR - You will see “A” lines or “Air Lines” - a reverberation artifact • FLUID ? • BLACK!! - PROPAGATES THROUGH - thus, is a great window to see behind and around fluid • BONE–
    30. 30. Mini QUIZ - what happens to the Ultrasound Wave when it hits.... • AIR ? • A LINES!! - COMPLETELY REFLECTED BACK TO PROBE - CANNOT “SEE” PAST AIR - You will see “A” lines or “Air Lines” - a reverberation artifact • FLUID ? • BLACK!! - PROPAGATES THROUGH - thus, is a great window to see behind and around fluid • BONE– • WHITE LEADING EDGE, then shadow - Near total reflection
    31. 31. Mini QUIZ - what happens to the Ultrasound Wave when it hits.... • AIR ? • A LINES!! - COMPLETELY REFLECTED BACK TO PROBE - CANNOT “SEE” PAST AIR - You will see “A” lines or “Air Lines” - a reverberation artifact • FLUID ? • BLACK!! - PROPAGATES THROUGH - thus, is a great window to see behind and around fluid • BONE– • WHITE LEADING EDGE, then shadow - Near total reflection • SOFT TISSUE?
    32. 32. Mini QUIZ - what happens to the Ultrasound Wave when it hits.... • AIR ? • A LINES!! - COMPLETELY REFLECTED BACK TO PROBE - CANNOT “SEE” PAST AIR - You will see “A” lines or “Air Lines” - a reverberation artifact • FLUID ? • BLACK!! - PROPAGATES THROUGH - thus, is a great window to see behind and around fluid • BONE– • WHITE LEADING EDGE, then shadow - Near total reflection • SOFT TISSUE? • White/Grey/Black of planes, layers, boundaries - - PROPAGATION AND REFLECTION
    33. 33. Mini QUIZ - what happens to the Ultrasound Wave when it hits.... • AIR ? • A LINES!! - COMPLETELY REFLECTED BACK TO PROBE - CANNOT “SEE” PAST AIR - You will see “A” lines or “Air Lines” - a reverberation artifact • FLUID ? • BLACK!! - PROPAGATES THROUGH - thus, is a great window to see behind and around fluid • BONE– • WHITE LEADING EDGE, then shadow - Near total reflection • SOFT TISSUE? • White/Grey/Black of planes, layers, boundaries - - PROPAGATION AND REFLECTION • **Precisely why ultrasound has such phenomenal applicability in medicine (fact, not opinion) --- ideal for creating images of internal organs!
    34. 34. “KNOBOLOGY”• MACHINE CONTROLS Zoom ,Freeze,Measure, Playback Orientation ,Gain, Depth,
    35. 35. KNOBOLOGY• GAIN – changes the brightness or “loudness” of echoes • Find brightness which allows for maximal contrast resolution -specific to type of tissue being imaged • novices tend to make entire image too bright/”loud”! (ALWAYS UNDERGAIN)• TIME GAIN COMPENSATION - (near/far gain) • term referring to uniform gain from near to far field • rarely have to do adjust near/far
    36. 36. “KNOBOLOGY”• MACHINE CONTROLS Zoom ,Freeze,Measure, Playback Orientation ,Gain, Depth,
    37. 37. What would you change in this image? (Gain, depth, orientation, or TGC?)• PERFECTLY GAINED IMAGE
    38. 38. How would you change the gain?• TOO LITTLE DEPTH
    39. 39. How would you change the gain?• Overgained heart
    40. 40. How would you change the gain?
    41. 41. KNOBOLOGY– DEPTH– can increase or decrease viewing depth • Always limit depth so structure of interest is CENTERED (allows for best resolution and optimal size) • Depth of interrogation is measured by scale on side of screen
    42. 42. SHALLOWER DEPTH =Greater line density = Better resolution
    43. 43. SHALLOWER DEPTH =Greater line density = Better resolution
    44. 44. SHALLOWER DEPTH =Greater line density = Better resolution
    45. 45. SHALLOWER DEPTH =Greater line density = Better resolution
    46. 46. SHALLOWER DEPTH =Greater line density = Better resolution
    47. 47. SHALLOWER DEPTH =Greater line density = Better resolution
    48. 48. SHALLOWER DEPTH =Greater line density = Better resolution
    49. 49. SHALLOWER DEPTH =Greater line density = Better resolution
    50. 50. SHALLOWER DEPTH =Greater line density = Better resolution
    51. 51. SHALLOWER DEPTH =Greater line density = Better resolution
    52. 52. SHALLOWER DEPTH =Greater line density = Better resolution
    53. 53. SHALLOWER DEPTH =Greater line density = Better resolution
    54. 54. SHALLOWER DEPTH =Greater line density = Better resolution
    55. 55. SHALLOWER DEPTH =Greater line density = Better resolution
    56. 56. SHALLOWER DEPTH =Greater line density = Better resolution
    57. 57. SHALLOWER DEPTH =Greater line density = Better resolution
    58. 58. SHALLOWER DEPTH =Greater line density = Better resolution
    59. 59. DEEPER DEPTH = Less line density = Less resolution
    60. 60. DEEPER DEPTH = Less line density = Less resolution
    61. 61. DEEPER DEPTH = Less line density = Less resolution
    62. 62. DEEPER DEPTH = Less line density = Less resolution
    63. 63. DEEPER DEPTH = Less line density = Less resolution
    64. 64. DEEPER DEPTH = Less line density = Less resolution
    65. 65. DEEPER DEPTH = Less line density = Less resolution
    66. 66. DEEPER DEPTH = Less line density = Less resolution
    67. 67. DEEPER DEPTH = Less line density = Less resolution
    68. 68. DEEPER DEPTH = Less line density = Less resolution
    69. 69. DEEPER DEPTH = Less line density = Less resolution
    70. 70. DEEPER DEPTH = Less line density = Less resolution
    71. 71. How would you improve this image?(Gain, depth, orientation, or TGC?)• UNDERGAINED IMAGE
    72. 72. How would you improve this image?(Gain, depth, orientation, or TGC?)• OVERGAIN ED IMAGE
    73. 73. How would you improve this image?(Gain, depth, orientation, or TGC?)
    74. 74. How would you improve this image?(Gain, depth, orientation, or TGC?)• TOO MUCH NEAR GAIN
    75. 75. SUMMARY• Understand these concepts: • piezoelectric principle (current - crystal vibrates- ultrasound wave - penetrates into tissues -reflection returns- crystal vibrates - creates current) • images are made by plotting echoes on a grid (screen) by amplitude (brightness) and time (location) • ultrasound wave behavior in tissues (air/bone- total reflectors, fluid - total transmission, soft tissue - partial reflector, partial transmission • reflective mediums/tissues are represented as “echogenic”/white (i.e muscle/fat) and propagator mediums/fluids are anechoic (black) • importance of setting ideal depth, gain, and orientation to obtain proper image for interpretation • Remember index mark orientation, pencil hold, rest hand on patient for stability
    76. 76. Further Study (if interested)• For an simple and thorough graphical illustration of ultrasound including a detailed explanation of concepts, I recommend the following website:http://folk.ntnu.no/stoylen/strainrate/Ultrasound/#2D

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