About the ultrasound

1. Ultrasonography in Animals

2. Ultrasonography in Animals

3. Ultrasonography in Animals
• Ultrasonography is the second most
commonly used imaging format in veterinary
practice.
• It uses ultrasonic sound waves in the
frequency range of 1.5–15 megahertz (MHz)
to create images of body structures based on
the pattern of echoes reflected from the
tissues and organs being imaged.

4. • Several types of image formats can be
displayed.
• The most familiar one (and the one that
creates the actual image of anatomy) is B-
mode grayscale scanning.
• The sound beam is produced by a transducer
placed in contact with and acoustically
coupled by means of a transmission gel to the
animal.

5. • An ultrashort pulse of sound is directed into
the animal, after which the transducer
switches to the receive mode.
• Echoes occur as the sound beam changes
velocity while passing from a tissue of one
density to one of another density, even when
the change occurs at nearly microscopic
levels.
• The greater the change in velocity, the greater
the strength of the echo.

6. • In modern scanning systems, the sound beam
is swept through the body many times per
second, producing a dynamic, real-time image
that changes as the transducer is moved
across the body.
• This real-time image is easier to interpret and
allows the examiner to scan continuously until
a satisfactory image is obtained.
• The image may then be frozen and recorded
in a digital format, which also allows for
recording of short segments of the real-time
scan.

7. • Sonographic imaging is also limited in
regard to the depth of tissue that can be
examined. Most scanners will display
tissues to a depth of ~24 cm, but the image
is often quite noisy at that depth. This is
because most tissue echoes do not return
directly to the transducer but are reflected
in some other direction. By a depth of 24
cm, the loss of energy from the sound
beam results in echoes so weak the
scanner cannot separate the returning
echoes from the background electronic.

8. • There is much less loss of beam
intensity in fluid media such as the
urinary bladder, so if the beam
passes through such a fluid media,
the maximum scanning depth may
be increased at the expense of
temporal resolution.

9. • Although ultrasound can be used to
evaluate most soft tissues, including
muscles, tendons, and ligaments, the
heart and abdominal organs still
constitute the majority of examinations
performed in small animals.
• In scanning of the abdomen, the
abdominal structures should be
systematically evaluated.

10. • Changes in the size and shape of organs,
tissues, and structures are evident in most
cases, but evaluation of the echo pattern is
based on comparison with that of other
organs and tissues the examiner has scanned
in other animals. The person evaluating the
scan must have a firm idea, developed from
experience and comparison with known
normals, of the normal echo pattern for each
organ scanned with each transducer.

11. • Diseased organs may be either uniformly altered
in echogenicity or exhibit focal or multifocal
changes. Focal changes are usually easier to
detect than uniform changes.
• Sonographic lesions are sometimes quite
characteristic of a given disease process, but
more often the changes are nonspecific.
Although ultrasonography can be quite sensitive
to detection of disease, the changes are not
specific for a given disease in most cases unless a
characteristic change in anatomic presentation is
detected along with changes in echogenicity.

12. • Ultrasound is the second most popular imaging
modality in veterinary medicine. Multiple
clinical studies have proven that
ultrasonography has clear advantages over
radiography when diagnosing abdominal organ
pathology, non-abdominal soft-tissue
conditions, fluid build-up, heart disease, and
countless others.
• Ultrasound is also used in non-diagnostic
applications such as safely guiding needles for
cysto centesis and cytology and tissue samples.

13. How Does Ultrasound Work
• Every ultrasound system has a CPU (computer,
central processing unit), which acts as the
brain of the machine. The CPU transmits
electrical currents to the transducer (probe),
which contains multiple piezo electric crystals.
• These crystals change shape rapidly and
vibrate when exposed to an electric current.
These vibrations produce sound waves, which
travel into the animal’s body.

14. How Does Ultrasound Work

15. • The sound waves interact with tissues and
eventually hit boundaries between tissues –
such as the interface between the liver and
gallbladder, bone and soft tissue, or between
fluid and soft tissue. Some of the sound waves
echo back to the transducer while others
travel farther until they reach another
boundary and get reflected back.

16. • When the reflected sound waves reach the
transducer, the same piezoelectric crystals
that created the outgoing wave are similarly
stimulated as they absorb the reflected wave,
and when they are, they emit electrical
currents, which are transmitted to the CPU to
form an image.

17. • The CPU calculates the intensity of the echoes
(which determines the brightness or darkness
of the images) and the distance between the
boundaries (e.g. soft tissue, bone, fluid), thus
determining depth information. These forces
and distances are displayed on the screen in a
two-dimensional image.

18. Different Types of Transducers
(Probes)
• Transducers, often called probes, are available
in varying sizes and shapes for different
applications. Different probes offer varying
fields of view and sound wave frequencies,
which determine how deep the sound waves
penetrate and the detail of images, termed
resolution.

20. • Most probes are designed to move across the
surface of an animal’s body. The shapes offer
different “fields of view” which are best suited for
certain applications or imaging specific organs.
• The two most common probes used in veterinary
ultrasound are micro-convex and linear array
transducers. Some specialized transducers are
designed to enter openings in the body, such as
the esophagus and rectum, to get closer to
specific organs. These are more common in large
animal reproductive ultrasound and in human
medicine.

21. When Does an Animal Need an
Ultrasound
• Ultrasound enables DVMs to see inside an
animal’s body without the risks associated
with other imaging modalities. Although in
human medicine ultrasound is primarily used
for pregnancy diagnosis, it has many, many
other uses in veterinary medicine.
• The following are common indications :

22. • Unexplained weight loss
• Persistent diarrhea or vomiting
• Pregnancy
• Fluid build-up in the abdomen
• Abnormal blood-work results
• Chronic infections
• Abnormal urinary habits
• Suspected heart failure
• Ligament or tendon tears
• Evaluate the animal before surgery
• Evaluate geriatric patients’ baseline health

23. Why Do Animals Have to Be Shaved
Before Ultrasound
• Ultrasound does not travel through air. Hair traps
air and disrupts sound waves which affects the
clarity of ultrasound images. Shaving the animal
and using a gel-coupling medium improves
contact between the patient’s skin and the
ultrasound probe, which enhances the quality of
images.
• Remember, ultrasound must travel into and out
of the patient in the most efficient way possible
to produce the most diagnostic image possible!

24. Echocardiography in Animals
• Echocardiography is ultrasonic evaluation of the
heart. In the past, it was done using the M-mode
format of displaying ultrasound information. A
narrow beam of sound is projected into the
heart, and the echo pattern and strength are
displayed onto a persistence screen, with the x-
axis of the display representing time (y-axis is
depth), similar to the familiar format of an ECG.
The pattern and amplitude of movement of the
walls of the chambers of the heart and valves can
be evaluated, as well as the size of the respective
structures along the path of the sound beam.

25. • The M-mode format has very high temporal
resolution and thus is especially suited to
evaluation of rapidly moving structures such
as heart valve leaflets. Considerable
experience is required to obtain and interpret
diagnostic studies. The M-mode examination
has been coupled with real-time B-mode
studies to improve the accuracy of beam
placement and add additional information,
such as shape of the chamber.

26. • Ultrasonographic images are also used to acquire
quantitative information about cardiac function.
Measurement of specified parameters may be
made on either the M-mode scan or on the two-
dimensional B-mode image. Some advanced
systems have the ability to produce a three-
dimensional image of heart structures.
Mathematical formulas are then applied to
determine values for cardiac output, ventricular
contractility, ejection fraction, ventricular wall
stiffness, and other cardiac functions.

27. Doppler ultrasound
• makes use of the familiar phenomenon that
sound emitted from a moving object such as a
train has a different apparent frequency to
someone standing still relative to the moving
object. If the object is moving away from the
observer, the frequency of the sound is lower;
conversely, if the emitter is moving toward the
observer, the frequency of the sound is higher.
The same is true of diagnostic ultrasound. Echoes
from moving RBCs change the frequency of the
sound reflected back to the transducer.

28. • The amount by which the frequency is shifted is
proportional to the velocity of the RBCs; whether it is a
positive or negative frequency shift is used to
determine blood flow direction. This is used to identify
valvular regurgitation (insufficiency), increased flow
velocity (as in stenosis), or abnormal movement of the
blood in the heart or vessels elsewhere in the body.
• Doppler signals may be displayed in two formats. In the
first, spectral Doppler, a sound beam is used to
evaluate a specific small volume within the vessel of
interest.

29. • This display resembles the M-mode display, except that the
frequency shift, or velocity, is substituted on the y-axis. It
also shares high temporal resolution (millisecond)
capabilities of the M-mode format. The second way to
display Doppler frequency shifts is to select a larger area of
the scan on a real time B-mode image, encoding the
velocities and direction as a color spectrum. The color
(usually red or blue) depicts blood flow direction, and the
hue depicts mean flow velocity. This allows evaluation of
larger areas, but at the price of lower temporal resolution.
For this reason, color-encoded B-mode flow studies are
used to guide placement of spectral sample volumes to
acquire more accurate and complete information.

30. • Thus, Doppler studies complement and
improve the accuracy and specificity of
echocardiograms. Quantitative evaluation of
spectral Doppler studies also allows the
examiner to determine values such as
pressure gradients across valves and stenotic
areas or resistance to flow of blood entering
an organ. In some cases, abnormal blood flow
patterns can be detected before obvious
anatomic lesions are present.

31. • Doppler evaluation of blood flow is not limited
to the heart. It is often used to assess blood
flow of vessels in the abdomen and other
locations. It is the most specific way to do this
and can be useful in detection of arterial or
venous thrombosis or malformation.

32. Contrast Ultrasonography in Animals
• Ultrasound contrast agents increase the
reflectivity of blood and any tissue through
which blood flows.
• Enhancement of blood reflectivity is usually
accomplished by injection or formation of
transient microscopic bubbles in the
plasma. The increase in echogenicity is
related to the amount of blood flowing
through the tissue.

33. • The bubbles are quickly absorbed into
the plasma and therefore do not
constitute an embolism hazard.
• The ability to evaluate the vascularity of
a tissue provides additional information
about the type of lesion present.

34. • For instance, granulomas generally have
poorer blood flow than normal tissue
and do not enhance as much as the
surrounding tissue, whereas tumors may
enhance more and retain the contrast for
a longer time than the surrounding
tissue.

35. • Contrast agents hold great promise for
improving both the sensitivity and
specificity of ultrasonographic
examinations. However, they are
extremely expensive, which precludes
their use in all but special instances or
funded research.

36. Difference Between CT , X -ary and
Mri
• X-rays and CT scans both use a small dose of
ionizing radiation to produce images.
• An MRI scan, however, doesn’t work this way.
It uses powerful magnets and radio waves to
create the images instead of ionizing
radiation.
• So, you are not exposed to radiation when
you have an MRI scan, unlike a CT scan or x-
ray.

37. • The MRI applies a magnetic field, lining up
each of the protons in your body.
• The radio waves are applied in short bursts to
these protons, relaying a signal the MRI
scanner picks up.
• Then the computer processes this signal and
creates a 3D image of the examined body
areas.

38. • The diagnostic images of a CT scan are taken
typically quicker than an MRI scan.
• For instance, a CT scan, as with x-rays, often
takes five minutes or less while MRIs can
take 30 minutes or more.