about the technology, physics and physiology of the different ultrasount and echocardiography transducers or probes.

1. RESOLUTION AND DIFFERENT
TRANSDUCERS
Dr Raghu Kishore Galla

2. RESOLUTION
• Image resolution is the detail an image holds.
• Imaging resolution has three aspects:
1. Detail
2. Contrast
3. Temporal
Contrast and temporal resolutions relate more directly to
instruments. Detail resolution relates more directly to transducers.

3. • If two reflectors are not separated sufficiently, they produce
overlapping (not distinct) echoes that are not separated on the
instrument display. Rather, the echoes merge together and
appear as one.
• Thus the echoes are not resolved. If distinct (separated by a
gap) echoes are not generated initially in the anatomy, the
reflectors will not be separated on the display.
• In ultrasound imaging, the two aspects to detail resolution are
axial and lateral, which depend on the different characteristics
of ultrasound pulses as they travel through tissues.

4. Axial Resolution
• Also known as linear, range, longitudinal, or depth resolution.
• It is the minimum reflector separation required along the
direction of sound travel (along the scan line) to produce
separate echoes.
• The important factor in determining axial resolution is spatial
pulse length.
• Axial resolution is equal to one half the spatial pulse length.
Axial resolution = ½ SPL
• Axial resolution is the minimum reflector separation necessary
to resolve reflectors along scan lines.
• Axial resolution (millimeters) equals spatial pulse length
(millimeters) divided by 2.

6. The SPL is the number of cycles emitted per
pulse by the transducer multiplied by the
wavelength.
Shorter pulses, producing better axial resolution,
can be achieved with greater damping of the
transducer element (to reduce the pulse duration
and number of cycles) or with higher frequency (to
reduce wavelength).

7. Objects spaced closer than ½ SPL will not be resolved

8. • For imaging applications, the ultrasound pulse typically
consists of three cycles.
At 5 MHz (wavelength of 0.31 mm), the SPL is about 3 x
0.31 0.93 mm, which provides an axial resolution of /2(0.93
mm) = 0.47 mm.
• At a given frequency, shorter pulse lengths require
heavy damping and low Q,broad-band width operation.
For a constant damping factor, higher frequencies (shorter
wavelengths) give better axial resolution, but the imaging
depth is reduced.
Axial resolution remains constant with depth.

9. Lateral Resolution
• Also known as Lateral, Angular, Transverse, Azimuthal resolution.
Lateral resolution is the minimum reflector
separation in the direction perpendicular to the beam
direction (that is, across scan lines) that can produce
two separate echoes when the beam is scanned across
the reflectors
• Lateral resolution is equal to the beam width in the scan plane.
Lateral Resolution = Beam Width (mm)

11. For both single
element transducers
and multi element
array transducers,
the beam diameter
determines the
lateral resolution

12. • Since the beam diameter varies with the distance from the
transducer in the near and far field, the lateral resolution is depth
dependent.
• The best lateral resolution occurs at the near field—far field face.
• Lateral resolution is improved by reducing the beam diameter,
that is, by focusing.
• The best resolution is obtained at the focus.
• Diagnostic ultrasound transducers often have better axial
resolution than lateral resolution, although the two may be
comparable in the focal region of strongly focused.

13. • At this depth, the effective beam diameter is approximately
equal to half the transducer diameter.
• In the far field, the beam diverges and substantially reduces
the lateral resolution.
• The typical lateral resolution for an unfocused transducer is
approximately 2 to 5 mm.
• A focused transducer uses an acoustic lens (a curved acoustic
material analogous to an optical lens) to decrease the beam
diameter at a specified distance from the transducer.

14. Section thickness: Elevational resolution
• The Elevational or slice-thickness dimension of the
ultrasound beam is perpendicular to the image plane.
• Can be considered a third aspect of detail resolution
and therefore is sometimes called Elevational
resolution.
• Elevational resolution contributes to section thickness
artifact, also called partial-volume artifact.
• This artifact is a filling in of what should be anechoic
structures such as cysts.

15. • This filling in occurs when the section thickness is larger than the size
of the structure. Thus echoes from outside the structure are included
in the image, and the structure appears to be echoic.
• The thinner the section thickness, the less is its negative impact on
sonographic images.
• Focusing in the section-thickness plane reduces section thickness
artifacts.
• Slice thickness is typically the worst measure of resolution for array
transducers.
• Use of a fixed focaI length lens across the entire surface of the array
provides improved elevational resolution at the focal distance.

16. Elevational
resolution is
dependent on the
transducer
element height in
much the same
way that the
lateral resolution
is dependent on
the transducer
element width.
Multiple linear array transducers with five to seven rows, known
as 1.5-dimensional (1.5-D) transducer arrays, have the ability to
steer and focus the beam in the elevational dimension.

17. The axial,
lateral, and
elevational (slice
thickness)
dimensions
determine the
minimal volume
element.

18. Contrast resolution
• It is the ability of a gray-scale display to distinguish between
echoes of slightly different intensities.
• Contrast resolution depends on the number of bits per pixel in
the image memory.
• Increasing the number of bits per pixel (more gray shades)
improves contrast resolution.
• ULS pulses DO NOT have a constant amplitude ,Overlapping
occurs.
Better Contrast Resolution = Better Detail Resolution
• An image with many shades of gray has better contrast
resolution.
• An image with less shades of gray degrades contrast resolution.
• It is your final production,what you are looking at the display
screen.

19. Temporal resolution
• The ability of a display to distinguish closely spaced
events in time.
• Improves with increasing frame rate.
• Frame is made of scan lines/individual
• When a frame is frozen, keeps the temporal resolution
of the frame when generated.
PRF = # focuses x lines per frame x frame rate

20. • # of focuses increase - PRF increase
• Lines/frame increase - PRF increase
• Frame rate increase - PRF increase
• Penetration increase - PRF decrease
• Frame rate decrease- displayed depth increase

21. Spatial resolution
• More lines per frame, therefore decrease spatial
resolution and great detail Ability to image fine detail
and distinguish two closely spaced structures.
• Overall detail of image.
• Line density determines spatial resolution
• Low line density: lines spaced far apart meaning less
lines per frame, therefore increase spatial resolution
and poor detail.
• High line density: lines closely packed meaning.

22. TRANSDUCERS

23. • TRANSDUCERS - have the ability to convert one form of energy
to another.
• Ultrasound transducers perform two functions
1.During transmission, electrical energy from the system is
converted into sound.
2.During reception, the reflected sound pulse is converted
into electricity.
• Ultrasound is produced and detected with a transducer,
composed of one or more ceramic elements with
electromechanical (piezoelectric) properties.

24. Piezoelectricity
• This effect describes the property of certain materials to
create a voltage (evp) when they are mechanically deformed
by a pressure.
• These materials change shape when voltage is applied.
Piezoelectric Effect
• Ability of a certain material to convert electrical energy to
mechanical energy and vice versa.
• Describes property of certain materials to create a voltage
when they are mechanically deformed or when pressure is
applied.
• When a pressure is applied the material expands and
contracts.

25. Piezoelectric Material (PZT)
1. Natural material
Quartz
Tourmaline
2. Synthesized Material
PZT
Lead Zirconate Titanate
Forms of ceramics
• TRANSDUCER - is also known as ceramic, active element
cristal, Element, Disc.
• PROBE - is the assembly that holds all the components in.
Often referred to as the Transducer.

26. • Over the past several decades, the transducer assembly has
evolved considerably in design, function, and capability, from
a single-element resonance crystal to a broadband
transducer array of hundreds of individual elements.
• A simple single-element, plane-piston source transducer has
major components including the
• Piezoelectric material
• Matching layer
• Backing block
• Acoustic absorber
• Insulating cover
• Sensor electrodes and
• Transducer housing.

29. • An electrical dipole is a molecular entity containing positive
and negative electric charges that has no net charge.
• When mechanically compressed by an externally applied
pressure, the alignment of the dipoles is disturbed from the
equilibrium position to cause an imbalance of the charge
distribution.
• A potential difference (voltage) is created across the element
with one surface maintaining a net positive charge and one
surface a net negative charge.

30. • Surface electrodes measure the voltage, which is
proportional to the incident mechanical pressure
amplitude.
• Conversely, application of an external voltage
through conductors attached to the surface
electrodes induces the mechanical expansion and
contraction of the transducer element.

31. • Ultrasound transducers for medical imaging applications
employ a synthetic piezoelectric ceramic, most often lead-
zirconate-titanate (PZT).
• The piezoelectric attributes are attained after a process of
• Molecular synthesis
• Heating
• Orientation of internal dipole structures with an
applied external voltage,
• Cooling to permanently maintain the dipole orientation
and
• Cutting into a specific shape.

32. • For PZT in its natural state, no piezoelectric properties are
exhibited; however, heating the material past its “Curie
temperature” (i.e., 3280 C to 3650 C) and applying an
external voltage causes the dipoles to align in the ceramic.
• The external voltage is maintained until the material has
cooled to below its Curie temperature.
• Once the material has cooled, the dipoles retain their
alignment.

33. • At equilibrium, there is no net charge on ceramic surfaces.
• When compressed, an imbalance of charge produces a
voltage between the surfaces.
• Similarly, when a voltage is applied between electrodes
attached to both surfaces, mechanical deformation occurs.
• The piezoelectric element is composed of aligned molecular
dipoles.

34. • Under the influence of mechanical pressure from an adjacent
medium (e.g., an ultrasound echo), the element thickness
Contracts (at the peak pressure amplitude),
Achieves equilibrium (with no pressure) or
Expands (at the peak rarefactional pressure),
This causes realignment of the electrical dipoles to produce
positive and negative surface charge.

36. • Surface electrodes measure the voltage as a function
of time.
• An external voltage source applied to the element
surfaces causes compression or expansion from
equilibrium by realignment of the dipoles in
response to the electrical attraction or repulsion
force.

38. Resonance Transducers
• Resonance transducers for pulse echo ultrasound imaging are
manufactured to operate in a “resonance” mode, whereby a
voItage (commonly 150 V) of very short duration (a voltage
spike of 1 msec) is applied, causing the piezoelectric material
to initially contract, and subsequently vibrate at a natural
resonance frequency.
• This frequency is selected by the “thickness cut,” due to the
preferential emission of ultrasound waves whose wavelength
is twice the thickness of the piezoelectric material.

39. • The operating frequency is determined from the
speed of sound in, and the thickness of, the
piezoelectric material.
For example, a 5-MHz transducer will have a
wavelength in PZT (speed of sound in PZT is  4,000 m/sec)
of
mmmeters
m
f
c
80.0108
sec/105
sec/4000 4
6


 


40. A short duration
voltage spike causes
the resonance
piezoelectric
element to vibrate
at its natural
frequency, fo, which
is determined by the
thickness of the
transducer equal to
1/A.

41. • To achieve the 5-MHz resonance frequency, a
transducer element thickness of ½ X 0.8 mm = 0.4
mm is required.
• Higher frequencies are achieved with thinner
elements, and lower frequencies with thicker
elements.
• Resonance transducers transmit and receive
preferentially at a single “center frequency.”

42. Damping Block
• The damping block, layered on the back of the
piezoelectric element, absorbs the backward
directed ultrasound energy and attenuates stray
ultrasound signals from the housing.
• This component also dampens the transducer
vibration to create an ultrasound pulse width and
short spatial pulse length, which is necessary to
preserve detail along he beam axis (axial
resolution).

44. • The “Q factor” describes the bandwidth of the sound
emanating from a transducer as
where fo is the center frequency and the bandwidth is
the width of the frequency distribution.
Bandwidth
f
Q o


45. • A “high Q” transducer has a narrow bandwidth (i.e.,
very little damping) and a corresponding long spatial
pulse length.
• A “low Q” transducer has a wide bandwidth and short
spatial pulse length.
• Imaging applications require a broad bandwidth
transducer in order to achieve high spatial resolution
along the direction of beam travel.
• Imaging applications require a broad bandwidth
transducer in order to achieve high spatial resolution
along the direction of beam travel.

46. • Blood velocity measurements by Doppler
instrumentation require a relatively narrow-band
transducer response in order to preserve velocity
information encoded by changes in the echo
frequency relative to the incident frequency.
• Continuous-wave ultrasound transducers have a
very high Q characteristic.
• While the Q factor is derived from the term quality
factor, a transducer with a low Q does not imply
poor quality in the signal.

47. Matching Layer
• The matching layer provides the interface between the
transducer element and the tissue and minimizes the
acoustic impedance differences between the transducer and
the patient.
• It consists of layers of materials with acoustic impedances
that are intermediate to those of soft tissue and the
transducer material.
• The thickness of each layer is equal to one-fourth the
wavelength, determined from the center operating
frequency of the transducer and speed of sound in the
matching layer.

48. • For example, the wavelength of sound in a matching layer
with a speed of sound of 2,000 m/sec for a 5-MHz ultrasound
beam is 0.4 mm.
The optimal matching layer thickness is equal to ¼ = ¼ x 0.4
mm = 0. 1 mm.
• In addition to the matching layers, acoustic coupling gel (with
acoustic impedance similar to soft tissue) is used between the
transducer and the skin of the patient to eliminate air pockets
that could attenuate and reflect the ultrasound beam.

49. Nonresonance (Broad-Bandwidth)
“Multifrequency” Transducers
• Modern transducer design coupled with digital signal
processing enables “multifrequency or “multihertz”
transducer operation, where by the center frequency can
be adjusted in he transmit mode.
• Unlike the resonance transducer design, the piezoelectric
element is intricately machined into a large number of
small “rods,” and then filled with an epoxy resin to create a
smooth surface.

51. • The acoustic properties are closer to tissue than a pure PZT
material, and thus provide a greater transmission efficiency of
the ultrasound beam without resorting to multiple matching
layers.
• Multifrequency transducers have bandwidths that exceed 80%
of the center frequency.
• Excitation of the multifrequency transducer is accomplished
with a short square wave burst of 150 V with one to three
cycles, unlike the voltage spike used for resonance transducers.
• This allows the center frequency to be selected within the
limits of the transducer bandwidth. Likewise, the broad
bandwidth response permits the reception of echoes within a
wide range of frequencies.

52. • For instance, ultrasound pulses can be produced at a low
frequency, and the echoes received at higher frequency.
“Harmonic imaging” is a recently introduced technique
that uses this ability
• lower frequency ultrasound is transmitted into the patient,
and the higher frequency harmonics (e.g., two times the
transmitted center frequency) created from the interaction
with contrast agents and tissues, are received as echoes.
• Native tissue harmonic imaging has certain advantages
including greater depth of penetration, noise and clutter
removal, and improved lateral spatial resolution.

53. Transducer Arrays
• The majority of ultrasound systems employ
transducers with many individual rectangular
piezoelectric elements arranged in linear or
curvilinear arrays.
• Typically, 128 to 512 individual rectangular
elements compose the transducer assembly.
• Each element has a width typically less than half
the wavelength and a length of several
millimeters.

54. Two modes of
activation are used to
produce a beam.
These are the “linear”
(sequential) and
“phased”
activation/receive
modes.

55. Linear Arrays
• Linear array transducers typically contain 256 to 512
elements; physically these are the largest transducer
assemblies.
• In operation, the simultaneous firing of’ a small group of 
20 adjacent elements produces the ultrasound beam.
• The simultaneous activation produces a synthetic aperture
(effetive transducer width) defined by the number of active
elements.
• Echoes are detected in the receive mode by acquiring signals
from most of the transducer elements.

56. • Subsequent “A-line” acquisition occurs by firing
another group of transducer elements displaced by
one or two elements.
• A rectangular field of view is produced with this
transducer arrangement.
• For a curvilinear array, a trapezoidal field of view is
produced.

57. Phased Arrays
• A phased-array transducer is usually composed of 64 to 128
individual elements in a smaller package than a linear array
transducer.
• All transducer elements are activated nearly (but not exactly)
simultaneously to produce a single ultrasound beam.

58. • By using time delays in the electrical activation of
the discrete elements across the face of the
transducer, the ultrasound beam can be steered and
focused electronically without moving the
transducer.
• During ultrasound signal reception, all of the
transducer elements detect the returning echoes
from the beam path, and sophisticated algorithms
synthesize the image from the detected data.

59. Beam properties
• The ultrasound beam propagates as a longitudinal
wave from the transducer surface into the
propagation medium, and exhibits two distinct
beam patterns
- a slightly converging beam out to a distance
specified by the geometry and frequency of the
transducer (the near field), and
- a diverging beam beyond that point (the far
field).

60. For an
unfocused,
single-element
transducer, the
length of the
near field is
determined by
the transducer
diameter and
the frequency of
the transmitted
sound.

61. • For multiple transducer element arrays, an
“effective” transducer diameter is determined by the
excitation of a group of transducer elements.
• Because of the interactions of each of the individual
beams and the ability to focus and steer the overall
beam, the formulas for a single-element, unfocused
transducer are not directly applicable.

62. The Near Field
• The near field, also known as the Fresnel zone, is adjacent to
the transducer face and has a converging beam profile.
• Beam convergence in the near field occurs because of multiple
constructive and destructive interference patterns of the
ultrasound waves from the transducer surface.
• Huygen’s principle describes a large transducer surface as an
infinite number of point sources of sound energy where each
point is characterized as a radial emitter.
By analogy, a pebble dropped in a quiet pond creates a
radial wave pattern.

63. As individual wave
patterns interact, the
peaks and troughs from
adjacent sources
constructively and
destructively interfere,
causing the beam
profile to be tightly
collimated in the near
field.

64. • The ultrasound beam path is thus largely confined to the
dimensions of the active portion of the transducer surface,
with the beam diameter converging to approximately half the
transducer diameter at the end of the near field.
• The near field length is dependent on the transducer
frequency and diameter:
where d is the transducer diameter, r is the
transducer radius, and  is the wavelength of ultrasound
in the propagation medium.

22
4
rd
lengthfieldNear 

65. • In soft tissue,  = 1.54mm/f(MHz), and the near field
length can be expressed as a function of frequency:
• For a 10-mm-diameter transducer, the near field
extends 5.7 cm at 3.5 MHz and 16.2 cm at 10 MHz in
soft tissue.
• For a 15-mm-diameter transducer, the corresponding
near field lengths are 12.8 and 36.4 cm, respectively.
  
 mm
MHzmmd
lengthfieldNear
22
54.14


66. A higher transducer
frequency (shorter
wavelength) will
result in a longer
near field, as will a
larger diameter
element.

67. • Pressure amplitude characteristics in the near field are
very complex, caused by the constructive and destructive
interference wave patterns of the ultrasound beam.
• Peak ultrasound pressure occurs at the end of the near
field, corresponding to the minimum beam diameter for a
single-element transducer.
• Pressures vary rapidly from peak compression to peak
rarefaction several times during transit through the near
field.
• Only when the far field is reached do the ultrasound
pressure variations decrease continuously.

68. The far field
• The far field is also known as the Fraunhofer zone, and is
where the beam diverges.
• For a large-area single-element transducer, the angle of
ultrasound beam divergence, 0, for the far field is given by
where d is the effective diameter of the transducer
and  is the wavelength; both must have the same units of
distance.
d

 22.1sin 

69. • Less beam divergence occurs with high-frequency,
large-diameter transducers.
• Unlike the near field, where beam intensity varies
from maximum to minimum to maximum in a
converging beam, ultrasound intensity in the far
field decreases monotonically with distance.

70. Transducer Array Beam Formation and Focusing
• In a transducer array, the narrow piezoelectric element width
(typically less than one wavelength) produces a diverging
beam at a distance very close to the transducer face.
• Formation and convergence of the ultrasound beam occurs
with the operation of several or all of the transducer elements
at the same time.
• Transducer elements in a linear array that are fired
simultaneously produce an effective transducer width equal
to the sum of the widths of the individual elements.

71. • Individual beams interact via constructive and destructive
interference to produce a collimated beam that has
properties similar to the properties of a single transducer of
the same size.
• With a phased-array transducer, the beam is formed by
interaction of the individual wave fronts from each
transducer, each with a slight difference in excitation time.
• Minor phase differences of adjacent beams form constructive
and destructive wave summations that steer or focus the
beam profile.

72. Common Transducers used in clinical setting

73. ELECTRICAL AND MECHANICAL TRANSDUCERS
Real – time Transducers
• Scanning of element happens within the assembly
• Performed electronically
• Gives rapid, dynamic imaging
• Imaging with a rapid frame sequence display
• Performed with arrays
• Dominate transducer today

74. MECHANICAL TRANSDUCERS (Fixed focus, Conventional)
• Single element
Disc shaped
Fan or Sector image
Fixed focal depth
• Two ways to focus:
1.External focusing – mirror or acoustic lens
2.Internal focusing – curving the crystal
• Rotating mirror, ducks and wheel
• Defective crystal destroy entire image

76. LINEAR SEQENTIAL ARRAY
• Multiple elements arranged in a line
• Approximately 1 wavelength long
• Display=rectangular image
• Beams go out parallel to each other
• Generally directed straight out from element
• Large footprint
• Big aperture

77. • Elements are stimulated individually in rapid
succession (basic sequential)
- Data is collected = one line of sight (scan line)
- 120-150 elements
- Automatic - no moving parts
- Focused - electronically
• Disadvantage – small crystal size = short narrow near
field with rapidly diverging far field
• Defective crystal – drop out of line, top to bottom

79. Clinical applications
• The straight linear array probe is designed for superficial
imaging.
• The crystals are aligned in a linear fashion within a flat head
and produce sound waves in a straight line.
• The image produced is rectangular in shape.
•This probe has higher frequencies (5–13 MHz), which provides
better resolution and less penetration.
•Therefore, this probe is ideal for imaging superficial structures
and in ultrasound-guided procedures.

80. • Vascular access
• Evaluate for deep venous thrombosis
• Skin and soft tissue for abscess, foreign body
• Musculoskeletal—tendons, bones, muscles

81. LINEAR SEGMENTAL ARRAY
• Elements arranged in a line(linear)
• Group or segment of crystals are stimulated instead
one at the time
• Voltage pulses are applied to groups in succession 1-
4, 2-5, 3-6
• Display =Rectangular Image
• Scan lines are parallel
• Beams sent straight out from element
• Beams are sent out parallel to each other
• Large footprint

82. • Large aperture of assembly
• Only scans across face of probe
- Focusing
- No Steering
• Great penetration
• Real time results if repeated rapidly enough
• Results in a deeper near field – les divergent Far Field
• This type of array is no longer in use

83. LINEAR PHASED ARRAY
• Elements arranged in a line (linear)
• Array=more than one element
• 100-300 elements side by side
• ¼-1/2 wavelength
• Display=sector image
• Beams sent in different directions=steering
• Display lines are not parallel
• Angle large as 90 or as small as 30 degrees results in higher
frame rate and increased in line density.
• Small footprint
• Compact - Small footprint+ Sector Image(steering)=good for
tight spaces
• Automatic –no moving parts

84. • Stimulates all elements at once
• All elements work as one channel
• Electronic steering
• Stimulates each crystal with small time delay
• Variations in pattern steer the beam in various directions
• Time difference is very small <1 microsecond
• Electronic Shaping(focusing)
• Can modify depth of focus
• Allow multi-focusing - Multiple beams down same line of sight
• Sweeping is required
• Defective element – erratic steering and focus

87. ANNULAR PHASED ARRAY
• Elements arranged in Concentric Rings
• Common center
• Display - sector image
• Steers mechanically – reflecting the beam witch
moving mirror, mechanically rotating transducer.
• Cannot steer without mirror!
• Large footprint
• Heavy snow cone
• Due to large aperture must apply great pressure to
get image

88. • Electronic Shaping(focusing)
• Ring shape allows multiple transmit focal zones
• Smaller diameter elements=shallow focus
• Larger diameter elements=deeper focus
• Each ring gets deeper
- Great lateral resolution
- Reduction of section thickness artifacts
- Defective crystal – horizontal dropout

90. CURVILINEAR ARRAY
• Convex, curved, radial
• Send pulses out in different directions from different
points across the curved array surface.
• Operates identical to the linear array, only has curved
construction
• Large footprint
• Lines of site perpendicular to the array surface
• Increase in curved pattern
• Greater time delays between elements
• Moves focus closer to source
• Decrease in curved delay pattern

91. • Shorter delays, less time between elements
• Moves focus far from source
• Consist of 128 – 256 crystals
• Crystals arranged along in arc
• Radius of curve varies between 25-200mm
• Larger radius=larger aperture
• No loss of focus on the edge pulses but limit to depth
• Similar to sector scanning, line density is decreased
at depth with curvilinear – contributing to a loss of
lateral resolution

93. Clinical Applications
• The image generated is sector shaped. These probes
have frequencies ranging between 1 and 8 MHz,
which allows for greater penetration, but less
resolution. These probes are most often used in
abdominal and pelvic applications.
• They are also useful in certain musculoskeletal
evaluations or procedures when deeper anatomy
needs to be imaged or in obese patients.

94. • Abdominal aorta
• Biliary/gallbladder/liver/pancreas
• Abdominal portion of FAST exam
• Kidney and bladder evaluation
• Transabdominal pelvic evaluation

95. ENDOCAVITARY PROBE
• The endocavitary probe also has a curved face, but a much higher
frequency (8–13 MHz) than the curvilinear probe.
• This probe’s elongated shape allows it to be inserted close to the
anatomy being evaluated.
• The curved face creates a wide field of view of almost 180° and its high
frequencies provide superior resolution .
• This probe is used most commonly for gynecological applications, but
can also be used for intraoral evaluation of peritonsillar abscesses.
• Transvaginal ultrasound
• Intraoral

97. VECTOR ARRAY
• Flat top with small footprint – ideal for intercostals scanning
• Sends out pulses in different directions from different starting
points
• Center is perpendicular
• Steer – electronically
• Focus - electronically
• Display – trapezoidal
• Phasing can be applied to each element group in a linear
sequenced array to :
a) Steer pulses in various directions
b) Initiate pulses at various starting points across the array
• Smaller footprint than curved

99. IVUS PROBE
• IVUS is a miniature ultrasound probe positioned at
the tip of a coronary catheter.
• The probe emits ultrasound frequencies, typically
at 20-45 MHz, and the signal is reflected from
surrounding tissue and reconstructed into a real-
time tomographic gray-scale image.

102. Thank you