Production of sound waves by an ultrasound probe (transducer) and the return of that reflected sound wave (echo)
Ultrasound
An extremely important tool with ultrasound technology because it reduces air between the pt and transducer
Helps with conduction
Ultrasonic gel
Distance a wave must travel
Wavelength
Number of cycles per second
Frequency
Speed at which sound travels through an object
Velocity
Intensity or loudness of a wave
Amplitude
Loss of intensity of the beam as it travels through tissue
Attenuation
What type of material displays absorption attenuation?
Liquids
What type of material displays scattering attenuation?
Uneven surfaces
Ability of tissue to resist transmission of sound
The > the density or elastic difference, the more reflective
Acoustic impedance
Converts energy into electrical impulses
Used to scan pt
Transducer
Within the transducer that converts electrical energy into ultrasound
Can be natural or synthetic
Crystals
Crystals vibrate and produce a wave, wave travels through tissues and crystals switch from sending to listening, echoes are received, and seen on the monitor
Piezoelectric effect
Quality of the ultrasound
Resolution
^ Frequency =
shorter soundwave=better resolution
Less penetration
The ability to distinguish between two objects or echoes that are adjacent to one another yet perpendicular to the sound wave
Lateral spatial
The ability to differentiate between two structures along the beam’s length
Axial
Frequency used for a small dog and cats
7.5 MHz
Frequency used for mid-large size dogs
5 MHz
Frequency used for large animals
3-5 MHz
AKA Sector probe, Convex
Wide field of view - pie-like
Mechanical sector
One of the first probes designed for high resolution
Rectangular view
Linear transducer
Transducer used in cardiac studies
Phased array sector
3D & 4D ultrasounds
Matrix transducer
Amplitude mode
Graphic display, used in ophthalmology
A-mode
Brightness mode
Cross section that gives a 2D image
Most common
B-mode
Motion mode
Straight lines = stationary objects, wavy lines = moving objects
Used in cardiology and in conjunction with B-mode
M-mode
Mode used for moving objects and fluid flow
Useful for <3 dz, shunts, blood flow patterns, thromboembolisms
Doppler
BART
Blue Away Red Towards
Detects velocity of flow
Power Color Doppler
Mode used for large/obese animals
Harmonic
Ability of tissue to bounce soundwaves
Intensity of reflected echoes
Echogenicity
Image appears black, no reflection (fluid filled)
Ex: bladder
Anechoic
Appears darker than surrounding tissue, varying shades of grey
Ex: blood, loose tissue, muscle
Hypoechoic
Appears brighter than surrounding tissues (white)
Ex: solid tissue, bladder stones
Hyperechoic
Equal in appearance to surrounding tissue
Isoechoic
Uniform greys
Ex: liver
Homogeneous
Varying shades of greys
Ex: kidneys
Heterogeneous
Transducer marker is positioned to the cranial or caudal end of the animal
Long axis
|
|
Sagittal
Transducer marker should be 90 degrees to the longitudinal plane
Short axis
——————-
Transverse
Affects the brightness (range of grey scale) of the image
Gain
Every transducer has a set max and min _____________ at which it can send and receive soundwaves
Depth
Allows the operator to selectively adjust the gain at various depths
Time gain compensation
Preinstalled settings
Presets
Maximizes the axial and lateral spatial resolution at the area of interest
Focal Zone Adjustments
Allows the operator to change the frequency within the range of frequencies allowed by the probe
Frequency Selection
Affects the gain setting and the tissue harmonics to obtain the ideal image as the sound beam travels through a particular part of the body
Optimization
Usually examined between the 4th and 5th rib
Start in R lateral recumbency with the transducer coming from underneath
Heart
The heart’s ________ and _________ are echogenic
walls; valves
Most hyperechoic of all organs
Uniform, granular appearance and seen best on pt’s left side
Spleen
Less echogenic than the spleen and echotexture is coarse (grainy and homogeneous)
Liver
Anechoic with a bright wall
Sometimes contains echogenic debris or sludge
Gallbladder
When scanning in lateral recumbency, it is bean shaped;.
When scanning dorsally, it is ovoid
Surrounded by a bright capsule
Kidneys
The cortex of the kidney is
hypoechoic
The medulla of the kidney is
anechoic
Anechoic with a hyperechoic wall
Bladder
Surrounds the urethra and is bilobed with a bright appearance
Larger and more echogenic in an intact male
Prostate
Optimal time for pregnancy detection in small animals
20 days
Optimal time for pregnancy detection in horses
11 days
Can be difficult to image because of gas and walls alternate black and white layers
Stomach and bowels
Adjacent to the duodenum on the right side and between stomach, spleen, and colon on the left
Pancreas
Hypoechoic and uniformly grey
Cranial pole of kidneys
Adrenal glands
Linear echoes caused by an inadequate amount of gel or sound reflected between transducer and strong reflector
Reverberation
Inadequate sound beam penetration (bone, calculi, calcium)
Shadowing
Sound traveling through fluid filled structure without attenuation
Enhancement
Soundwave changes directions causing a hypoechoic band
Refraction
Acoustic enhancement
AKA: Duplicate image
Mirror image
Produced by front and back of strong reflector (air bubble, BB)
Comet tail