basics of ultrasound, history, physics, applications of ultrasound in anesthesia practice

1. Ultrasound Basics, Troubleshooting
And Outline Of Uses In Anaesthesia
Presenter Dr Gowri Shankar B
Moderator Dr Naresh babu

2. Outline
 History ofultrasound
 Physics of echo
 Ultrasound waveand itsinteractions
 Ultrasound machine anditsparts
 ArtifactsAndTheir ClinicalImportance
 DopplerUltrasound
 Current And Potential Applications Of Ultrasound
 Bioeffects
 Conclusion

3. Introduction
• Anesthesiologists require quick and accurate diagnostic tools for the
effective management of emergencies
• Ultrasound (US) is a safe, easily accessible point-of- care imaging
modality
• US being increasingly adopted in modern anesthesiology practice
• Anesthesiologists are aware of the expanding applications of this
technology and the status of its use.

4. So What is ultrasound?
 Ultrasound or ultrasonography is a medical imaging technique that uses
high frequency sound waves to obtain cross sectional images of the
body.
 Also known as ‘pulse echo’ technique

5. History
• In 1794 Spallanzani performed studies on bats that concluded
that they could navigate using sound rather than sight.
• In 1915 Inspired by the sinking of the Titanic, Physicist Paul
Langevin invented a hydrophone – what the World Congress
Ultrasound in Medical Education refers to as the “first
transducer”
• 1920s-1940s Sonography was used to treat members of
European soccer teams as a form of physical therapy, to
appease arthritic pain and eczema
• In 1942 Neurologist Karl Dussik is credited with being the first to
use sonography for medical diagnoses

9. Physics of echo
 Sound
• Sound is a mechanical energy that travels through matter, as
a result of vibration of the particles of the medium through
which the sound wave is moving.
• Transport the energy through medium > pressure wave
• Change in pressure > sinusoidal waveform
• Medical ultrasound Megahertz range(2-15 MHz)

10. • Velocity
• Speed at which a sound wave travels through a medium
• Determined by density and stiffness of media
• Slowest in air/gas
• Fastest in solids
• Average speed of ultrasound in body is 1540m/sec
Physics of echo

12. Frequency
• Number of cycles per second, Units are Hertz
• Ultrasound imaging frequency range 2-15Mhz
• Low the frequency, higher the penetration and lower the resolution
Higher the frequency, lower the penetration and higher the resolution
Physics of echo

13.  Amplitude
• The strength/intensityof a sound waveatanygiven time
• Represented as height of thewave
• Decreases with increasingdepth
• Amplitude determines brightness ofimage
• The highertheamplitude, the brighter the
imageand vice-versa
Physics of echo

14. Electrical energy converted to sound waves Thesound waves are reflected by tissues
Reflected sound waves are convertedto electrical
signals and later toImage
Physics of echo

15. • Image Formation
 Electrical signal produces ‘dots’ on thescreen
 Brightness of the dot is proportional to the strength of the
returning echoes
 Location of the dot is determined by travel time
Physics of echo

16. PrincipleOFULTRASOUND
 Ultrasoundworksontheprincipleof piezoelectriceffect.
 When acrystal is subjected to mechanical pressure, electric voltage is
generatedand viceversa.

18. Interactions of ultrasound
• Transmission
• Reflection
• Refraction
• Scattering
• Attenuation

19. Interactions of ultrasound
Transmission
 Not all the sound wave is reflected, some continues deeper into
thebody
 These waves will reflect from deeper tissue structures

20. Interactions of ultrasound
Reflection
 Occurs at a boundary between 2 adjacent tissues or media
 The amount of reflection depends on differences in acoustic
impedance (z) between media
 The ultrasound image is formed from reflected echoes
 Acoustic impedance=density of medium x velocity

21. Reflection
• Iftwo materialshavesameimpedance,no echoproduced.
• Ifthedifferenceinacousticimpedanceis:
• Small–weakechoisproducedandmostof the soundwaveswill continue in
second medium
• Large-strongechoisproduced
• Verylarge- all soundwaveswill betotally reflectedback.Example:ce 99%ofbeam
isreflectedback.
Interactions of ultrasound

22. Interactions of ultrasound
Refraction
 This occurs when an ultrasound beam passes at an angle other than
90 degrees, from one tissue into another with change in velocity
 It increase with the increasing angle of incidence
 It passes deeper into the body where it gives rise to artifacts

23. Interactions of ultrasound

24. Interactions of ultrasound
Scattering
 Redirection of sound in several directions
 Caused by interaction with small reflector or rough surface
 Only portion of sound wave returns to transducer

25. Interactions of ultrasound
Attenuation
• The decrease in the intensity of the ultrasound wave as they pass
through tissues
• Results from absorption , reflection , scattering and beam divergence

26. Low attenuationHigh attenuation
Artifacts

27. Ultrasound machine and itsparts
 A basic ultrasound machine
1.Display
2.CPU
3.Transducer probes
4.Keyboard/control panel
5.Disc storage device
6.Printer

28. Ultrasound machine and itsparts

29. Ultrasound machine and itsparts
 Machine orientation:
• -presets
• -features
• -save and print
 Machine features:
• -Quality
• -Mode
• -Tools

30. Mode
 2D/B mode
 Doppler
-Color doppler
-continuous wave doppler
-pulse wave doppler
 M-mode
 3D
 4D
Ultrasound machine and itsparts

31. Freeze
Trackball
Caliper
Toggle key
Text key
Ultrasound machine and itsparts

36. Current and potential applications of
ultrasound
 Regional Anesthesia
 Neuraxial And Chronic Pain Procedures
 Vascular Access
 Airway Assessment
 Lung Ultrasound
 Gastric Ultrasound
 Focused Transthoracic Echo (TTE)
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37. Regional Anaesthesia
Direct
Observation
Of The
Nerves
Surrounding
Structures
Direct
Observation
Of Local
Anesthetic
Spread
Faster
Onset
21
3 4

38. Improves
Block
Quality
Allows
Dose
Reduction
Safety
76 8
Longer
Duration
5
Regional Anaesthesia

39. Neuraxial And Chronic Pain Procedures
 Neuraxial Blocks
 Nerve Root Blocks (E.G., Cervical And Lumbar);
 Stellate Ganglion Block
 US Guidance For Peripheral Nerve Stimulator Implantation
 Interventional Procedures For Patients With Chronic Pelvic
Pain (E.G., Pudendal Neuralgia, Piriformis Syndrome , And
“Border Nerve” Syndrome).

40. Vascular Access
• Identification of the vein
• Detection of variable anatomy, intravascular
thrombosis
• Avoidance of inadvertent arterial puncture
• Safer and less time consuming than the traditional
landmark technique
• Patients with underlying coagulopathy or platelet
dysfunction

41. A new 4- dimensional imaging (real-time
3-dimensional imaging) approach, using
a matrix arrays transducer, for central
venous cannulation, prevents
“overshooting” the needle and provides
better visualization of anatomy.
• High-frequency (50mhz) micro-
ultrasound (HFMU) may allow better
visualization for the sub-10mm space.
This could be a valuable tool for difficult
vascular access in pediatric patients

42. Airway Assessment
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visualize with US
tongue
oropharynx
hypopharynx
epiglottis
Larynx & vocal cords
cricoid cartilage
cricothyroid membrane
trachea
Cervical esophagus
NOT Visualize with US
posterior pharynx
Posterior commissure,
posterior wall of the trachea

43. Airway Assessment
Prediction of difficult airway
Confirmation of proper endotracheal tube placement and
ventilation
Prediction of obstructive sleep apnea
Airway Related nerve blocks
Prediction of size of endotracheal, endobronchial, and
tracheostomy tubes
Assessing and guidance for proper percutaneous
dilatational tracheostomy (PDT);
Evaluation of airway pathologies :Mandate urgent
securing of airway (e.G., Epiglottitis);

45. The probe is placed under the
submandibular area in a
longitudinal orientation
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Post injection sonography.
(1)Superior border of the thyroid cartilage.
(2)Greater horn of the hyoid bone.
(3)Thyrohyoid muscle.
(4)Thyrohyoid membrane.
(5)Thyroid cartilage lamina
The probe is placed under the
submandibular area in a
longitudinal orientation
Post injection sonography.
(1)Superior border of the thyroid cartilage.
(2)Greater horn of the hyoid bone.
(3)Thyrohyoid muscle.
(4)Thyrohyoid membrane.
(5)Thyroid cartilage lamina

46. Ultrasound for the
Anesthesiologists
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48. Lung Ultrasound
 In a number of emergency situations:
 Hypoxia
 Pneumothorax
 pulmonary edema
 pulmonary embolism
 ARDS
 ultrasound can be an important tool for diagnosis
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49. LUNG ULTRASOUND
• choice for detecting pleural line
abnormalities
A high frequency
(7.5 to 10MHz)
• diagnose pleural effusions and
lung parenchymal abnormalities
lower frequency
(3.5MHz) convex
and microconvex
• virtual interplay of two elements:
air and fluid.
B- and M-mode
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50. Normal Lung
“Lung sliding” signs are sliding of visceral and
parietal layers of pleura with respiration
Seashore sign is a complex picture of parallel
lines signifying the static thoracic wall and
sandy “granulous” pattern, which reflect the
normal pulmonary parenchyma.
A-lines are a basic artifact of normally aerated
lung
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51. Normal Lung

52. Gastric ultrasound
• Assessment of gastric content and diagnosis of full stomach
• Confirmation of gastric tube placement
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53. Gastric ultrasound

54. Gastric Ultrasound
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55. Focus assessed transthoracic echo
• Focus assessed transthoracic echo (FATE) was introduced by
jensen et al for cardiopulmonary monitoring in ICU
• Basically involves 4 standardized acoustic views for
cardiopulmonary screening and monitoring
• Recent studies show a great impact of FATE in preoperative
assessment
• Significantly alters perioperative management

56. Technological Advances
• Matrix array is a new transducer with
improved resolution.It has a lens that is
placed in front of the piezoelectric
element to allow a mechanical focusing
in the y- and z-planes
• Four-dimensional ultrasound provides
real-time 3d images (the 4th “d” is time)
and currently is used for fetal imaging,
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57. Technological Advances
• Mobile ultrasound guided peripheral
nerve block has been developed
• Sonixgps needle guidance system is a
gps technology with a new needle
tracking system, using sensors in both
the needle and transducer to obtain a
real-time image of needle shaft and tip
position related to the us beam that is
based on the needle trajectory
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58. Conclusion
• Ultrasound is a unique tool which optimization of
perioperative management.
• We believe that ultrasound can be the "third eye" of
the anesthesiologist that helps in the performance of
previously blind procedures and allows discovery of
many hidden spaces to uncover their mysteries
• Anesthesiologists, in the near future, may need to carry
a portable ultrasound around their neck instead of a
stethoscope.
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59. Bioeffects
 Thermal
 Mechanical

60. Thermal bioeffect
• Mechanism - with sound wave attenuation, energy is lost as heat
• Longer use of ultrasound on the tissue  longer the
ultrasound has attenuated in the tissue
• More the tissue attenuates ultrasound  more the bioeffects
• Higher the frequency/power/PRF/pulse duration , more the
attenuation and thus the heating
• NCRP guidelines – in ultrasound examinations, no temperature rise
> 1°C


61. Mechanical bioeffects
• Current USG systems can produce cavitation
• Determines potential for bubble formation in vivo
• Cavitation -
 Stable
 Inertial / Transient

62. Stable cavitation
• A bubble forms as the peak low pressure region of an ultrasound pulse passes
through a nucleation site
• This bubble grows and shrinks with the high pressure and low pressure
region of the ultrasound pulses
• This growing and shrinking of the bubble causes fluid to flow around the
bubble - micro-streaming
• Causes mechanical damage, sometimes cell lysis


63. Inertial/transient cavitation
• Here, the bubbles formed in a similar way but under high pressure or
intensities, they expand very quickly following which they collapse violently
• This collapse produces high temperature and pressure, which damages
cells in the region of the collapse

64. Ultrasound for the
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65. Mechanical index
It is an approximation of mechanical effects
It is a calculated number based on ultrasound
parameters and facts about the machine that
the manufacturer built into the programming
Mechanical index less than 1.9, no mechanical
effects is seen

67. References
 Rumack , Diagnostic Ultrasound , FifthEdition
 WHO Manual of Diagnostic Ultrasound
 Internet