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1. Application of Ultrasound and
Biological effect
Presenter :- Yashawant Kumar Yadav
BSc. MIT 3rd yr
NAMS , Bir Hospital
1

2. OUTLINE
• Introduction of Ultrasound
• Modes of Ultrasound with application
• Doppler US and types with application
• Different kinds of probes with medical application
• Biological effect
• References
2

3. Intro…..
• Any sound with a frequency above 20,000 Hz (or 20 kHz)that is, above the
highest audible frequency—is defined to be ultrasound.
• 1Hz = 1 cycle / vibration
• 1kHz = 1000 cycle per second
• 1MHz = 1 million vibrations per second.
3

4. Contd….
• A sound wave can be described as a mechanical, longitudinal wave composed of
cyclic compressions and rarefactions of molecules in a medium.
4

5. Interaction
• Reflection
• Refraction
• Absorption
• Scattering
• Acoustic impedance
• Z = ρv, The units for Z are therefore kg/(m2 · s).
• Matching layer ???
• Z of PZC is 15 times higher than skin
5

6. Parameters
• Amplitude:
• Power :- (joules /s) (A2)
• Intensity :- The energy per unit cross-sectional area in a sound beam,
• Intensity is expressed in joules/second/square centimeter.
• Joule/second = watt
• (w/cm2)
6

7. Contd…
Relative scale intensity is defined in units of the decibel (dB)
In common practice, the lowest-intensity audible sound (10-12 W /M2) is assigned
the value of 0 dB.
10dB = 102 Times of 0dB
So 120 dB = 1012 times
i.e 1 trillion times of 0 dB
7

8. Production of US in Medicine
Piezoelectric US generation.
Natural --
- (quartz, and lead titanate)
Piezoelectric crystals
I. Barium titanate,(BaTiO3) (1st discovered )
II. Rochelle salts, (KNaC4H4O6·4H2O)
III. Potassium niobate (KNbO3)
IV. Ammonium dihydrogen phosphate (ADP)
V. lead zirconate titanate . (Pb[ZRxTi]O3)
VI. Sodium tungstate (N2WO3)
VII. Sodium potassium niobate (NKN) lead free 8

9. Pulse acoustic phenomenon
• Continuous waves are not useful for structural imaging.
• One pulse typically consists of three to five cycles.
Pulse US parameters
• Pulse duration (0.5 to 3 µs).
• Pulse repetition period: ( 0.1 to 1 ms.)
• Spatial pulse length: (0.1 to 1 mm).
• Duty factor (0.1 % to 1 %. )
• Pulse repetition frequency (PRF): (1 OOO to 10,000 Hz )
PRF is inversely proportional to imaging depth.
9

10. Tissues attenuation
• Bone is represented as a very bright
structure and appears ‘hyperechoic’.
• Muscle presents as hypoechoic, with
some internal signals as a result of
collagen fibers.
• Tendon show tightly packed
hyperechoic lines representing the
fibrils of the tendon.
10

11. Contd….
• Nerves as ‘honeycomb’ like structures composed of
hypoechoic spots embedded in a hyperechoic
background.
• Fluid presents has an anechoic appearance on
ultrasound.
• Air bubbles reflect much of the US that engages them and
appear very echo dense (bright).
• Ligament
11

12. Medical application
• Ultrasound is used in medicine for therapy and diagnosis.
In diagnosis :
• Ultrasound have 4 basic mode :-
1. A – amplitude mode
2. B – brightness mode
3. M- motion mode
4. Doppler
12

13. A-amplitude mode (10–20 MHz)
• Mode A is a one-dimensional process, and simplest
type of US .
• Basically used to determine depth of abnormality .
(function of depth )
• Therapeutic ultrasound aimed at a specific tumor or calculus is
also A-mode, to allow for pinpoint accurate focus of the
destructive wave energy.
• As an example on how Mode A can be applied,
• US encephalography, and US ophthalmology
13

14. 14

15. Contd…
In a case where the middle brain structures have been displaced (for
example by the presence of an odd mass in a lobe that pushes them into the
other lobe)
15

16. Contd….
16

17. B – Brightness mode
• The B-mode is a two-dimensional (2D) image
of the area that is simultaneously scanned by a
linear array of 100–300 piezoelectric elements
rather than a single one as in A-mode
• B-Mode composed of bright dots representing
the ultrasound echoes.
• The brightness of each dot is determined by
the amplitude of the returned echo signal.
17

18. 18

19. M- Motion Mode
• A continuous B-mode display. Displays one
scan line versus time.
• Allows for a high frame rate, accuracy of
linear measurements, and tracking of motion
of reflectors
(x-axis: time; y-axis: reflector depth)..
• M-mode is used extensively in cardiac and
fetal cardiac imaging.
• Its an application of B - mode imaging
19

20. Doppler mode
• The Doppler effect is defined as the change in
the frequency of sound emitted or reflected by a
moving object. The amount of change is termed
the Doppler shift.
20

21. Th is angle is known as the angle of
insonation.
21

22. Contd…
• The highest Doppler frequency shift from any specific vessel occurs
when the vessel and the beam are aligned; that is, when the angle of
insonation is zero and the cosine function has the value of 1.0.
• The least desirable situation occurs when the angle approaches 90° as
then the Doppler frequency shift will be minimum.
• In clinical practice it is often not possible to align the beam and the
vessel.
• As a rule, provided the angle is less than about 60°, good-quality
spectral waveforms can be obtained. 22

23. Application of doppler
1. Peripheral vascular system - Arteries and veins of the extremities
2. Central arteries / veins - Abdominal aorta, IVC, mesenteric vessels
3. Cerebrovascular system -
4. Cardiology
5. Obstetrics and Gynecology - IUGR, Uterine arteries, Ovarian torsion
6. Renovascular hypertension
7. Male infertility / erectile dysfunction, testicular torsion
8. Tumors, AV malformations.
23

24. Contd…
There are five methods of imaging by employing Doppler principle.
a) Continuous wave doppler
b) Pulsed wave Doppler
c) Color Doppler
d) Power Doppler
e) Spectral Doppler or Duplex scanning
24

25. CONTINIOUS WAVE DOPPLER
• This employs two piezoelectric crystals, both contained
in a single head. One crystal transmits a continuous
sonic signal at a known frequency (3-8 MHz).
• The other crystal receives the returning echoes and
records their frequency.
• It is employed in detection of blood flow but does not
give information of depth, direction and velocity of
flow.
• From a practical standpoint, continuous wave Doppler
should be used when measuring velocities > 1.2 m/s.
(e.g., regurgitant jets, stenotic valves).
• No depth resolution
25

26. 26

27. Contd…
Pulsed wave Doppler (PW):-
Provide depth information , variable depth can be acquired by changing beam
frequency (low for high penetration and high for low penetration)
 Three factors affects PWD To evaluate mobile structure
I. High pulse repetition frequency
II. Optimum transducer frequency
III. Insonation angle (less than 600)
It is customarily combined with a B mode / 2-Dimensional mode imaging, which is
then called duplex scanning.
measuring relatively low-flow velocities ( < ~ 1.2 m/s) in specific areas of interest
(e.g., pulmonary vein flow, mitral valve inflow). 27

28. Contd..
• Because sampling is intermittent, the pulse repetition frequency limits the
maximum Doppler shift (and thus maximum velocity) that can be measured
accurately.
• Velocities higher than this maximum velocity will appear to wrap around on the
display, a phenomenon known as aliasing.
• The Doppler frequency shift at which aliasing occurs, equal to PRF divided by 2,
is termed the Nyquist limit.
28

29. Contd..
• Doppler shift (expressed in Hz) = (2 · v · Fi cosine ϴ)/c (if ϴ= 0/180 =1/-1)
Doppler shift= (v· Fi)/770
v = 770· (Doppler shift/Fi)
• if a 5-MHz transducer can only send out about 15,000 pulses per second, the
Nyquist limit is 7500 Hz (15,000/2).
• Using the velocity equation shown earlier, the maximum velocity that can be
measured without aliasing is about 1.15m/s (770 X (7500/5,000,000)).
29

30. 30

31. Color doppler(Also called color flow imaging (CFI) or color velocity imaging (CVI) )
• Ten or more pulse packets are used to
produce an estimate of mean velocity of all
reflectors.
• This data is assigned color by the machine
and is superimposed on B mode data from
stationary structures.
31

32. Contd…
• Flow that travels away from the transducer (negative Doppler shift) is depicted in
blue,
• Flow that is traveling toward the transducer (positive Doppler shift) is depicted in
red, with lighter shades of each color denoting higher velocities.
• A third color, usually green or yellow, is often used to denote areas of high flow
turbulence.
Clinical use :-
• overall blood flow to a region of interest. Depiction of the general velocity and
direction of blood flow within the heart and blood vessels.
• It also allows the. generation of unique phenomena such as the fluid color sign
32

33. Contd …
• The fluid color sign is a diagnostic sign to differentiate a pleural
effusion from pleural thickening by means of color Doppler ultrasound.
• In the case of pleural effusion a color signal is seen in the pleural fluid during
respiratory and cardiac movement, whereas this color signal is not seen in the case
of pleural thickening.
33

34. Power Doppler or Energy mode imaging
• An alternative processing method.
which ignores the velocity and simply
estimates the strength/amplitude of
the Doppler signal detected from each
location. And encoded as a color .
• The Energy mode image is
continuous and hence not sensitive to
relative flow direction. It does not
give the absolute values of velocity
but only gives the strength of the
Doppler signal.
34

35. Contd….
• The higher sensitivity to slow
flow.
• Power Doppler is particularly
useful when examining superficial
structures, like thyroid, testis,
renal grafts and subcutaneous
lesions. It may be used to look for
tumor vessels, to evaluate tiny
low-flow vessels and detect subtle
ischemic areas.
35

36. Contd…
Advantages of Power Doppler over Color flow imaging
I. More sensitive to flow states (3-5% more sensitive than
CFD)
II. Angle effects are ignored unless the angle is close to 90°
III. Aliasing is not applicable.
There are disadvantages also
(i) Values of velocity and the direction of blood flow cannot
be assessed.
(ii) Because of more averaging of information at slower
frame rates. slow moving soft tissue signals appear as
flash artifacts
36

37. Spectral doppler
• Spectral Doppler displays the blood flow
measurements graphically, displaying
flow velocities recorded over time.
• For spectral Doppler , the machine
represents the movement of blood via an
audible flow sound, and a graph
depicting flow velocities in relation to
time.
• This mode is ideal for measuring lower
velocities at chosen anatomic locations,
37

38. ULTRASOUND PROBES
• Linear array
• Curvilinear array
• Phased array
• linear array, “L”
• electronic linear scanning, “E”
in the xz plane
• Curve scan “C”
• “E<xz” electronically focus
38

39. Acoustic window’s
An acoustic window is the
location from which
an ultrasound probe makes it's
scan.
39

40. Linear (5-15MHz)
• Designed to make contact with flat surfaces, with the
footprint decreasing in size with increasing frequency.
• Here rectangular and trapezoidal formats provide appropriate
viewing areas. With abdominal imaging, to increase the
viewing area with minimal increases of the contact area
• Use for high-resolution imaging of superficial structures,
40

41. Contd..
• This probe is ideal for ultrasound-guided needle entry (particularly vascular
access),
• evaluation of deep venous thrombosis,
• chest imaging for pleural lines (pneumothorax),
• skin and soft tissue imaging for abscesses.
• Nerve blocks
• Ophthalmologic
• Joint /tendon
• Thyroid/breast
• Evaluation of superficial structure
41

42. Curve linear array (1-8MHz)
• convex arrays designed to make surface contact in
deformable soft areas of the body.
• The curvilinear (convex) array probe is used for scanning
deeper structures,
• The crystal alignment along a curved surface generates a
beam that fans outward. The result is a field of view wider
than the probe’s footprint,
• These probes are most often used in abdominal and pelvic
diagnostic applications. 42

43. Contd….
• These probes are most often used in abdominal and pelvic diagnostic applications.
• Hepatobiliary
• Renal
• Appendix (pediatric )
• Aorta
• Focus assessment in case of trauma
• Fetal heart tones and obstetric complication (pregnancy )
• Emergency lung examination
• Paracentesis and thoracentesis
43

44. Phase array (2-7.5MHz)
• Consisting of 64-128 elements. It is a smaller
assembly .
• The phased array probe is a lower frequency probe.
• Beam can be steer electronically , variable field
shape can be acquired .
• The smaller footprint allows for image acquisition
between the ribs, and the slightly convex surface
produces a fanning beam with a sector-shaped image.
44

45. Contd…..
• This probe is used for echocardiography and thoracic imaging but can be applied
to abdominal and pelvic imaging as well.
• Procedure guide
• Alternative to curvilinear for abdominal structure evaluation
• Pericardiocentesis
• Thoracentesis
45

46. 46

47. Biological effect
• Energy deposition in biological tissue.
• With CW ultrasound, the tissues are irradiated throughout the duration of the
exposure, and the total energy deposited in tissue will be much more in
comparison to PW irradiation over the same total exposure duration,
• Consequences of high intensity, prolonged exposures
1. Elevation of tissue temperature (thermal effect )
2. Cavitation in liquids (non thermal effect )
Interlinked
47

48. Elevation of temperature
• The mechanical energy of ultrasound can be transformed into heat through
absorption in tissue, resulting in the elevation of tissue temperature.
• Temperatures exceeding 4°C above normal body temperature, maintained for
long periods of time, may be harmful to the embryo and fetus, leading to a variety
of biological changes which can result in abortion, fetal death, or developmental
abnormalities,(teratogenic effect )
• These effects have been seen following whole body heating of both the mother
and the offspring, (approx. 0.5°C min−1 )
48

49. Contd..
The World Federation for Ultrasound in Medicine and Biology (WFUMB)
recommends that diagnostic exposures that produce a maximum temperature rise of
1.50 c above the normal physiological level of 37°C
• Ultrasound heating is very rapid . In addition, ultrasound exposures in pregnancy
only subject a small fraction of the maternal volume to a potential temperature
rise, and thus any heating of the embryo is likely to be rapidly dissipated.
49

50. Cavitation in liquids( non thermal effect )
• Cavitation is a phenomenon which takes place in
liquid cavities exposed to very high intensities of
ultrasound
• The presence of gas within the volume of the
liquid may lead to the formation of micro bubbles
during the low pressure phase (rarefaction) of the
ultrasound wave cycle. With changes in pressure,
the bubbles may grow in size. During the high
pressure phase (compression),
• The micro bubbles may collapse a with the
release of large quantities of mechanical energy
which can cause biological damage.
50

51. Contd..
• cavitation can also be the cause of free radical formation.
• Free radicals are highly reactive chemical species which can attack bio molecules
through a chain of chemical reactions, producing toxic bio products.
• This leads to damage of biological matter not only locally, but also remotely
through diffusion of toxic products.
• cavitation is unlikely to occur with PW ultrasound
51

52. Drug delivery (Sonoporation )
• Refers to a technique capable of
controlling drug delivery efficiency by
maximizing the drug permeability of
surrounding tissues or cells using a
reaction mechanism between
microbubbles and ultrasonic waves.
• Injecting microbubbles intravenously can minimize drug side effects that may
cause nonspecific delivery of drugs into healthy organs because the microbubbles
only collapse in specific diseased areas due to focused ultrasound irradiation.
52

53. 53

54. Contd …
• ultrasound-mediated microbubble destruction (UMMD)
• ultrasound-targeted microbubble destruction (UTMD).
54

55. THANK
YOU
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56. References
• https://theultrasoundsite.co.uk/ultrasound-case-studies/starting-article-2-
different-tissues-ultrasound-look-like/
• https://www.nysora.com/foundations-of-regional-
anesthesia/equipment/physics-of-ultrasound/
• https://radiologykey.com/doppler-imaging-2/
• https://radiopaedia.org/articles/phased-array
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6208473/
• Martinoli, C., Pretolesi, F., Crespi, G., Bianchi, S., Gandolfo, N., Valle, M.,
& Derchi, L. E. (1998). Power Doppler sonography: clinical
applications. European journal of radiology, 27 Suppl 2, S133–S140.
https://doi.org/10.1016/s0720-048x(98)00054-0
• https://echocardiographer.org/Echo%20Physics/spectral%20doppler.html
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57. 1. Cavitation effect in microbubble contrast agent ??
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