Ultrasound Flashcards
What does an ultrasound do?
Generate images that allow for evaluation of the texture of organs and providing real-time visualization of the functional ability of organs
Ultrasound imaging is based on the _______
conversion of energy
How does the ultrasound produce the images on the screen?
electrical energy is applied in pulses to a probe & is then converted to sound waves by crystals w/in the probe. Those sound waves are directed into the patient. The specific rate of the sound waves depends on the direction of the wave and density of the components that the waves encounter. The waves can be absorbed, scattered, or reflected back as an echo to the transducer
Sound waves are described by their _____ & _____
frequency & wavelength
Amplitude
height of the waves
Taller waves = ____ sound waves
louder
Wavelength
Distance between each of the bands
Frequency
The number of wave cycles that occur each second
Hertz (Hz)
The unit of measurement of frequency
One wave cycle per second is equal to ______ hertz
1
Most procedures in diagnostic ultrasound uses frequencies with a range between
2-15 MHz
Frequency and wavelength are ______ related when the speed through which the sound travels through a medium is _______
inversely; constant
Greater resolution is obtained with ____ wavelengths
shorter (same as w/ xrays)
Higher frequency of the shorter wavelength ______ penetrating power of the sound
reduces
Anechoic
areas that don’t generate an echo
How do anechoic areas appear?
Appear black on the final image & represent fluid-filled structures
Hyperechoic
areas w/ high intensity echo
How do hyperechoic areas appear?
appear very bright
Hypoechoic
Little returning echo
How do hypoechoic areas appear?
darker gray
Isoechoic
Areas w/ returning echoes that are the same as the surrounding tissues
What are the basic components of an ultrasound machine?
power source, transducer, control panel
What is a transducer consisted of?
Piezoelectric crystals that are arranged in a specific configuration (array)
What is the transducer?
Probe
Generates the sound waves & serves to receive the returning echoes
How does the transducer work?
The piezoelectric crystals w/in the probe being to vibrate and emit sound when electrical energy is applied to the probe
The range of frequencies the transducer can generate varies depending on what?
Thickness of the crystals
The frequency the transducer can generate is based on the _____ of the crystals
size
What are examples of different types of transducers?
sector array, linear array, curvilinear array, phased array, annular array
What does the configuration of the array in the probe dictate?
the application it is used for as well as the appearance of the image on the monitor
What does a sector array transducer produce?
produces a wedge or pie shaped image
What does a linear array transducer produce?
A rectangular shaped image
Useful when assessing blood flow
What is the most common transducer?
Linear array
What does a curvilinear array produce?
It is a type of linear array that is arranged into a convex curve
What is the ideal use of microconvex versions of the curvilinear transducer?
most small animal patients & ideal for abdominal imaging
What is a phased array transducer?
A transducer that has the crystals aligned linearly that are activated in sequence
Commonly used for cardiac studies
What are annular array transducers?
Transducers characterized by crystals aligned in rings
Not in common use
What does the control panel do?
Adjust the power, gain, time-gain compensation, brightness, contrast
What does the power control on the control panel do?
alters the intensity of the sound wave (amplitude) generated by increasing the voltage to the transducer
What happens when you apply a higher voltage to the transducer?
It generates sound pulses that are louder
Louder pulses generate _________
louder echoes = brighter image
What does the pulse repetition frequency control?
it can change the frequency or rate at which pulses are released
Echoes from deeper tissues take ______ to return to the transducer than more superficial structures
longer
The ultrasound waves lose ______ as they travel through tissues
amplitude (attenuated)
What is used to determine the tissue characteristics?
The amplitude of the returning echo
What does the gain control do?
Modify the strength of the returning echo
What does time-gain compensation do?
Compensates for the difference in strength of the returning echo depending on the depth of the tissue.
It also allows the ultrasound image to be modified so that the inherent brightness of more superficial structures as compared to deeper structures is minimized
What are the three primary display modes?
A mode
B mode
M mode
What is a mode?
Amplitude Mode
Least commonly used
Displays returning echoes as peaks that designate their intensity
What are the primary uses of A mode?
ophthalmology evaluations and measurement of subcutaneous fat in production animals (swine)
What is B mode?
Brightness mode
Most commonly used
Displays returning echoes as bright dots on the monitor w/ varying degrees of brightness corresponding to the intensity of the returning signal
What is M mode?
Motion mode
Creates a B mode image in motion
What is the primary use of M mode?
Echocardiography
What is a doppler ultrasound used for?
Evaluating blood flow
The velocity and direction of the flow of blood & other fluids can be determined as well
How does a doppler ultrasound work?
the sound waves generated are reflected back to the probe when they encounter cells
What are the varying types of doppler methods?
color, powder, pulse wave, continuous wave
What are the primary uses of ultrasound in large animal medicine?
Pregnancy diagnosis and monitoring of fetal development
What are other uses of ultrasound in large animal medicine?
Useful for detection of pleural fluid in horses & is ideal for detecting injuries to tendons and ligaments in performance horses
Evaluation of back fat in swine used for meat production
What is the ultrasound used for in both large & small animal medicine?
Centesis and tissue biopsy
What is an AFAST?
abdominal focused assessment w/ sonography for trauma
It detects and scores free fluid in the peritoneal cavity, which is a common feature in abdominal trauma
True or False: Sound waves can travel through air
False
How are large animals usually evaluated w/ the ultrasound?
In standing position
What from the patient can cause artifacts into the images?
Movement, panting, tensing of muscles, struggling
What position should the patient be in for an aFAST?
right lateral recumbency
What position should the patient be in that has respiratory or cardiac compromise for an ultrasound?
Standing or sternal
What are artifacts?
any result that does not reflect the actual characteristics of the tissue or organ being images
True or False: Artifacts can either aid in diagnosis or complicate or confuse diagnosis
True
What are examples of different artifacts that can be present on ultrasound?
Comet tail, acoustic shadowing, distance enhancement, edge shadowing, slice thickness, reverberation, mirror image, side lobe
