L18b: equine distal limb ultrasonography

what is ultrasound considered the diagnostic method of choice for assessing in equine?

tendon injuries

frequency

 number of cycles per second of the sound wave

what happens to the wavelength if the frequency of the sound wave is higher?

the wavelength must be shorter

what type of probe do we use to measure the tendons and ligaments of the equine distal limb>

linear probe

what depth does the linear probe penetrate into the tissue?

6cm in depth

what is the correlation between frequency and detail on ultrasound?

high-frequency ultrasound waves pick up more details, but are not able to go far in depth (superficial structures)

what are the properties of sound waves?

1. reflection

2. absorption

3. scattering

4. attenuation

5. refraction

what do biological tissues do to sound waves?

cause impedance which influences the velocity of sound through the tissue

what properties of sound waves contribute to artifacts seen on ultrasound?

1. refraction

2. scattering

attenuation

sound traveling through a medium is weakened by reflection, refraction, scattering, and absorption of heat by tissies

what does time of the returning echoes inform?

how long it takes for the image to appear in relation to the probe tells you the depth of the tissue

what is the depth of the tissue that is closer to the probe?

this tells you it is a more superficial tissue

what are the modes of ultrasound?

1. brightness mode (B-mode)

2. motion mode (M-mode)

3. doppler modes

B-mode ultrasound system

measures the intensity of the returning echoes, which is expressed in terms of pixel brightness on the unit monitor

what are the particular appearance of tissues based on in B-mode ultrasound?

1. normal appearance

2. tissue type

3. density

echogenicity

the characteristic/ability sound waves and produce of a tissue to reflect echoes

hyperechoic appearance

light grey or white

hypoechoic appearance

Low level of gray echoes

anechoic

appears as black

what structure will be the most hyperechoic on ultrasound?

bone or gas

what structure will be most anechoic on ultrasound?

blood/fluids

which structure is more hyperechoic on ultrasound: connective tissue or fat?

connective tisssue

which structure is more hyperechoic on ultrasound: spleen or liver?

spleen

which structure is more hyperechoic on ultrasound: liver or renal cortex?

liver

hypoechoic to

darker than

hyperechoic to

brighter than

from hypoechoic to hyperechoic put the tissues in order

1. medulla

2. cortex

3. liver

4. spleen

5. prostate

what is most echogenic on ultrasound?

bone and gas

what is least echogenic on ultrasound?

fluids

what echotexture is shown?

heterogenous

what echotexture is shown?

homogenous

MCQ: in comparison to the tendons, what is the echogenicity of the liver?

hypoechoic

MCQ: how do gases interact with the ultrasound waves?

strong reflector and strong attenuator

what are the roentgen signs?

1. number

2. size

3. shape

4. position

5. appearance / echogenicity

where on the forelimb should the hair be clipped?

from just below the accessory carpal bone to below the fetlock

where on the hindlimb should the hair be clipped?

from the metatarsal region up to the chestnut

what transducer is used to look at the proximal suspensory ligament?

micro-convex

why do we apply gel when doing an ultrasound?

to remove air to prevent potential artifacts

what is the imaging technique for ultrasound of the distal equine limb?

1. scan from palmar and plantar approaches

2. use both transverse and longitiudinal planes

what is the typical scanning order for equine distal limb ultrasound?

1. start proximal and move distal

2. begin with transverse views, then longitudinal

3. add oblique views as needed

what structure is circled in red?

superficial digital flexor tendon

what structure is circled in yellow?

deep digital flexor tendon

what structure is circled in green?

suspensory ligament

how will tendons appear on a longitudinal scan?

1. uniform striation

2. hyperechoic

3. separated by anechoic spaces

4. uniform heterogenicity

what structure is indicated by the yellow arrows?

superficial digital flexor tendon

what type of ultrasound scan does this show?

longitudinal scan

how do tendons appear on a transverse scan on ultrasound?

1. coarse granular dots

2. hyperechogenic interface

what type of ultrasound scan is shown?

transverse scan

what structure does the pink box indicate?

deep digital flexor tendon

what structure does the blue box indicate?

superficial digital flexor tendon

MCQ: This is a transverse scan of the Mid carpal region of an 8- years-old horse. What is the structure annotated by the arrows?

SDFT

MCQ: Transverse scan of the DDFT at the Mid-MC region appears as a/an

oval structure

what structure is indicated by the green bracket?

suspensory ligament

what structure is indicated by the red bracket?

DDFT

what structure is indicated by the yellow bracket?

SDFT

how may the suspensory ligament in adult and older horses appear on a longitudinal scan?

have a thinner or less marked striation at the origin and proximal body

what is the red circling?

suspensory ligament at proximal MC 3

what is the red circling?

suspensory ligament at the mid MC 3

what is the red circling?

SDFT just below the carpal joint

what is the red circling?

SDFT at the mid MC 3

what is the red circling?

SDFT at the distal MC 3

what is the red circling?

SDFT at proximal fetlock joint

where does the DDFT start on a transverse scan?

dorsolateral to the SDFT

what is the red circling?

DDFT just below the carpal joint

what is the red circling?

DDFT mid MC 3

what is the red circling?

DDFT at proximal fetlock joint

what are the portions of the suspensory ligament on a transverse scan?

1. proximal origin

2. body

3. lateral and medial branches

how does the suspensory ligament appear in younger horses?

mottled, hypoechoic appearance

how is the suspensory ligament appearing at every portion?

bilaterally symmetrical at any level

how does the suspensory ligament appear at the origin and body on transverse scan?

1. rectangular in cross-section

2. body is coarser, more heterogenous, and less echogenic than tendons

how do the medial and lateral branches of the suspensory ligament appear on transverse scan?

both initially start as oval but then become tear drop as the move distally