Ultrasonography Flashcards
Ultrasound is used for
Used to image soft tissues
Cannot image through bone or gas
Can provide anatomical and functional information of organs that are simply gray shapes on radiographs
Why does ultrasound not have the same risks as radiography
Since ultrasound involves sound waves, it is not believed to have the same risks as radiography
The waves involve mechanical energy, not electromagnetic
How does ultrasound work
A beam of high frequency sound waves is sent into a patient
Interacts with different organs and tissues where they primarily are absorbed or reflected
If they are reflected, they are sent back to the ultrasound (u/s) machine
Computer in u/s machine interprets the returning soundwaves and displays a gray-scale image on the monitor
Patient prep for ultrasound
Patient may need to be shaved depending on
Areas being imaged
Patient haircoat
Examination being performed
Patient may require fasting
Patient may require sedation
Echocardiography is
The use of ultrasound in the investigation of the heart and great vessels and the diagnosis of cardiovascular lesions
Echo or Echoes: what the soundwaves are called in ultrasonography or echocardiography
Attenuation is and contributing factors
Reduction in the intensity of sound waves reflected back to transducer
Factors that contribute:
Absorption of some of the sound waves or their strength
Scatter of some of the sound waves in directions other than back to transducer
Reflection back to the transducer
Echogenicity is
Appearance of tissues on u/s based on ability to reflect sound waves
Refers to brightness of tissues
Hyperchoic is
Tissues that reflect basically all u/s waves back to transducer (higher intensity)
Include bone and air
Appear very white or light
Hypoechoic is
Tissues that reflect only some of the u/s waves back to transducer (lower intensity)
Some waves continue to penetrate deeper to be reflected back by other tissues
Appear as varying shades of gray
Isoechoic
Two structures that have relatively similar echogenicity toward each other
Anechoic
Tissues lacking internal echoes (no intensity)
Includes fluids
Appear black on screen
The transducer consists of
Consists of one or more piezoelectric crystals that convert electrical signals into mechanical signals and then back into electrical signals for processing by a computer
Basic principles of ultrasound
u/s uses high frequency soundwaves to generate an image
Frequencies used in diagnostic imaging
2.5-13 MHz
2.5-3.5 MHz used on ultrasound on
LA- heart and abdomen
5.0 MHz used on
LA – heart, abdomen, thorax (lung), reproduction
SA – abdomen and heart (large dogs)
7.5-13MHz used on ultrasound when
LA - tendons, ligaments, eye, superficial structures
SA – abdomen, heart, eye, superficial structures
How does ultrasound work
Short burst of current applied to crystal causing it to vibrate at high frequency
Crystal deforms and emits sound waves
Transducer placed in contact with patient and soundwaves travel through patient
Within tissues, sound waves are either absorbed
Soundwaves eventually reflected back to transducer where they interact with crystal again and are converted back to electric signals
What do the different densities look like in ultrasound
Bone = 100% reflection
Air = scattering of sound waves causing 99% reflection
Soft tissue = reflects small amounts of sound waves but allows others to pass through to deeper tissues
Fluid = 100% transmission of sound waves to deeper tissues
Types of ultrasound
B-Mode
M-Mode
Doppler
B-mode ultrasound is
‘Brightness’ mode
Real time ultrasound
Commonly recognized images produced by ultrasound
2-dimensional display of returning echoes
Amplitude of returning echo is converted to the brightness of a dot on the display
Brighter the dot = stronger the returning echo
Location of dot on display corresponds to location of echo reflector
What does the image look like on b-mode
Single, frozen static image (static B-mode)
Many frames can be acquired and displayed within one second (real time B-mode)
In real-time imaging, each frame is refreshed when next echo pulse sweeps across the tissue cross-section
30-60 pictures/second
Allows evaluation of moving structures
M-mode ultrasound is
‘Motion’ mode
1-dimensional view of depth vs time
M-mode and echocardiography
Single scan line selected from the B-mode image
Displays cardiac structures moving over time
Vertical axis – depth of structure from transducer
Horizontal axis – time
Why use M-mode ultrasound
Used to obtain cardiac measurements
Cardiac chamber
Wall thickness
Used to evaluate valve and wall motion
How does doppler work
Not really a separate type of ultrasound, but more an application of ultrasound properties
Based on Doppler principle of changing frequency of sound related to direction of sound (echo) source
What does doppler detect
When applied to blood flow can detect:
Velocity
Direction
Flow pattern
Two types of doppler
Spectral
Color-flow (CFD)
Spectral doppler is
Wave form display of blood velocity and direction
Displayed over time
Above baseline = towards transducer
Below baseline = away from transducer
Color flow doppler is
Color display superimposed over a 2D image
Usual color display
BART
Blue = Away
Red = Towards
Turbulence = mosaic/mixture of colors
Artifacts in ultrasound
Ultrasound is riddled with them!
Occur as structures that are either:
Not real
Missing
Improperly located
Improper brightness, shape or size
Knowledge of artifacts is important
Make proper analysis
Some helpful, others not
Many artifacts occur because of computer confusion
Uses of ultrasound in vet med
Abdominal
Cardiac
Eye
Musculoskeletal
Non-cardiac thoracic
Reproductive
Biopsies
Foreign bodies/radiolucent objects
When is ultrasound contraindicated
Extremely gas-filled structures
To determine function of organ
Except for the heart
