this ppt is on basic principle ofultrasound

1. TOPIC: PRINCIPLES OF ULTRASONOGRAPHY
COLLEGE OF VETERINRY SCIENCE AND ANIMAL
HUSBANDRY MHOW
DEPARTMENT OF VETERINARY GYNAECOLOGY AND
OBSTETRICS
Dr. Madhu Shivhare
Assistant Professor

2. WHAT IS ULTRASONOGRAPHY
• Ultrasonography is the use of high-frequency sound
waves to generate an image.
• It is is relatively safe and noninvasive.
• It has become a useful diagnostic tool in veterinary
and medical field.
• This technique complements other imaging
modalities, such as radiography, and allow more
definitive diagnostic tests (e.g., biopsy, fine-needle
aspiration) to be conducted.
• User dependent.

3. PHYSICAL PROPERTIES OF SOUND
WAVES
• Sound is a wave of energy that transmitted through a
medium.
• Sound waves can be described by their frequency,
wavelength, and velocity.
• The frequency is the number of cycles or waves that are
completed every second. The frequency of the sound
waves used in ultrasonography is well above the limit
of the human ear (20,000 kHz) — usually in the range
of 2 to 12 MHz (2 to 12 million Hz).
• the wavelength is the distance needed to complete one
wave cycle.

4. FREQUENCIES
Frequencies those are used generally
3.5 MHz
5.0 MHz
7.5M Hz
High Frequency
Low Frequency
Low
penetration
Greater Surface
Details
Deep
penetration
Lesser Surface
Details

5. • An inverse relationship exists between the frequency and
the wavelength of a sound wave: the higher the
frequency, the shorter the wavelength.
• This relationship affects the choice of frequency used in
each patient undergoing ultrasonography.
• The velocity of an ultrasound wave is independent of the
frequency but, it changes depending on the medium.
• Velocity of sound in air is 331 m/sec, 4,080 m/sec in
bone. Within the soft tissues of the body, it is considered
to be steady at about 1,540 m/sec.
• Relationship between frequency, wavelength, and
velocity:
Velocity (m/sec) = Frequency (cycles/sec) x Wavelength
(m)

7. IMAGE PRODUCTION
• Two basic principles need to be understood.
• The first is the piezoelectric effect, which explains
how ultrasound is generated from ceramic crystals in
the transducer.
• The second key principle is the pulse-echo
principle, which explains how the image is
generated.

8. BASIC PRINCIPLE OF ULTRASOUND
A pulse is generated by one or more piezoelectric crystal in an
ultrasound transducer. As the transducer is placed in close
contact with the body surface through coupling medium, a
portion of ultrasound beam reflected back towards the source
in the form of echo which is converted into visual image by the
computer of the ultrasound machine.

9. TRANSDUCER (Ultrasound Probe)
PIEZOELECTRIC CRYSTALS HIGH FREQUENCY
(Lead Zirconium Titanate)
EXPANSION AND CONTRACTION
MECHANICAL WAVES Tissues
Propagate Reflect
Received by the
probe
Electric impulses
Displayed on Screen as echogenic
dots
ALTERNATE
VOLTAGE

10. INTERACTON WITH TISSUE
• Ultrasound produced by the transducer interacts with different
tissues in a variety of ways that may help or hinder image
formation.
• Attenuation: This is the gradual weakening of the ultrasound
beam as it passes through tissue.
• Refraction: When ultrasound waves are bounced back to the
transducer for image generation
• Scattering: The redirection of ultrasound waves as they interact
with small, rough, or uneven structures

11. • Absorption: This is occurs when the energy of the
ultrasound beam is converted to heat. This occurs at
the molecular level as the beam passes through the
tissues.
• Reflection: When the ultrasound beam hits a structure
at an oblique angle. The change in tissue density
produces a change in velocity, and this change in
velocity causes the beam to bend, or refract.

12. TYPES OF TRANSDUCERS
• Transducers are first classified as linear or sector,
according to the arrangement (array) of the crystals and
the shape of the imaging field produced on the monitor
• Linear - the crystals are oriented in a straight line,
producing a rectangular image in which both the near
and far fields are wide.
– provide superior resolution of near-field structures.
– Mostly used for equine and bovine reproduction.
• Convex/sector - resolution similar to linear array used in
transabdominal and transvaginal purposes.

14. Ultrasound Machines
• Sector -Pie shaped examining field

15. MODES OF ULTRASOUND
• Information generated from an ultrasound examination can be
displayed in a variety of ways, called modes. The mode used
for display depends on the type of ultrasound unit used, the
information to be obtained, and the organ being examined.
There are three modes of ultrasound machines viz. A mode, B
mode, M mode .
• A mode (amplitude mode): The returning echoes are
displayed on the monitor as spikes originating from a single
vertical or horizontal baseline.

16. • B (Brightness) Mode:
• In B mode, echoes are represented by dots on a line that form the
basis of a two-dimensional image. The brightness of each dot
indicates the amplitude of the returning echo. Its location relative
to the transducer is displayed along the vertical axis of the
monitor, with the top of the monitor representing the transducer.
• Real-time B mode ultrasonography allows a complete, two-
dimensional, cross-sectional image to be generated by using
multiple B-mode lines. This is the mode most commonly used in
veterinary practice. It is a two dimensinal display in the form of
dots.

17. • M (Motion) Mode
• M mode is used in echocardiography and allows the
sonographer to measure the heart to assess cardiac
function and chamber size. M mode uses a single B-
mode line, with the amplitude of the echoes indicated
by the brightness of the displayed dots. The
difference is that the information obtained from that
single line is constantly swept across the monitor so
that the motion of the body part being investigated is
displayed along the horizontal axis.

18. ARTIFACTS
• Artifacts are features of the ultrasound-generated
image that do not truly represent the area being
examined.
• It is important to recognize common artifacts and
understand how and why they occur so that, if
necessary, they can be eliminated through adjustment
of the imaging technique.
• Some artifacts can be helpful, aiding in the diagnostic
potential of ultrasonography.

19. Blockage due to bone, calculi, foreign body, feces
ACOUSTIC SHADOW: The ultrasound beam cannot
penetrate this area, an anechoic shadow appears on the
monitor distal to the area.

20. Reverberation
REVERBERATION:
It occurs when the ultrasound beam bounces back and forth
several times between a highly reflective tissue interface and the
transducer. Each time the returning echo hits the transducer, the
reflecting surface appears twice as deep on the screen.

21. Acoustic enhancement: Acoustic enhancement is an area
of increased echogenicity distal to structures with low
attenuation of ultrasound waves. As noted above,
ultrasound waves are attenuated as they pass through
tissues and thus become weaker. This artifact is useful in
differentiating a fluid-filled structure from an anechoic
solid structure (e.g., a lymph node).

22. Mirror Image:
Mirror image artifact is often seen at rounded, highly reflective
interfaces and leads to the erroneous placement of structures on the
sonographic image. It is most commonly seen during abdominal
ultrasonography when the ultrasound beam travels through the liver
and gallbladder to the diaphragm.
Edge Shadowing:
Edge shadowing is an artifact that appears as an anechoic area
extending distally from the lateral margins of round, fluid-filled
structures like the bladder, gallbladder, and kidneys. It is created by
the change in velocity and resulting refraction of the ultrasound
beam as it passes through the fluid-filled structure. It cannot be
corrected.

23. THANKYOU