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What are the two different types of ultrasound?
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What is diagnostic ultrasound?
short bursts of ultrasound
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Does diagnostic ultrasound cause damage to tissue?
no
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What is therapeutic ultrasound?
constant wave of sound?
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What is the purpose of therapeutic ultrasound?
used to breakdown tissue
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What is the nature of sound?
wave of mechanical pressure
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What is ultrasound transmitted through?
a medium - air, metal, body
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What is a frequency?
cycles per second
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What is frequency measured in?
- 1 hertz (Hz) = 1 cycle per second
- 1 megahertz (MHz) = 1,000,000 cycles/second
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What ranges of frequency are used in veterinary medicine? What are the common frequencies used?
- range from 2.5 - 12 MHz
- commonly used: 3.5 MHz, 5 MHz, 7.5 MHz
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Can people hear the frequency of an ultrasound?
no
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What frequency can people hear? Dogs?
- people: 20 - 20,000 Hz
- dogs: 70 - 100,000 Hz
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What is velocity?
speed of transmission of the sound wave
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What is the formula for velocity?
velocity = wavelength x frequency
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the velocity of ultrasound in the patient's body is a _____.
constant
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As frequency increases, wavelength _____.
decreases
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As frequency decreases, wavelength _____.
increase
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How do we get shorter sound waves?
use higher frequency transducer (7.5 MHz) or setting
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Short sound waves give _____ image resolution
- increased
- clear, detailed picture
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Shorter sound waves give _____ patient penetration.
decreased
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What are some examples of what we can use shorter sound waves on?
- abdomen in cats and small dogs
- eyes
- tendons of horses
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Longer sound waves give _____ patient penetration
increased
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Longer sound waves _____ image resolution.
- decreased
- more grainy, less detail
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What would we use longer sound waves to exam?
- deeper structures
- abdominal ultrasound in medium and large size dogs
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How is the image of an ultrasound formed?
by the pattern, intensity, and depth of the reflected sound waves (echos)
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Echos or sound waves are _____ in proportion to tissue density.
reflected
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Does ultrasound penetrate air?
no
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What color is air on an ultrasound?
white
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What does ultrasound not penetrate air?
because there is such a great change in density between air and tissue
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Ultrasound cannot see past air _____, _____, and _____.
- trapped in hair coat
- pockets in the GI system (stomach, intestines)
- in normal lungs
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Can ultrasound tell anything about a structure behind or surrounded by air?
no
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What color is bone on an ultrasound?
white
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Can ultrasound tell us anything about a structure behind or surrounded by air?
no
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Does ultrasound penetrate fluid well?
yes
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What color is fluid on an ultrasound?
black
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An ultrasound image will appear _____ if fluid has particles in it?
textured
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What are the intermediate tissues in the body?
- muscles
- liver
- kidneys
- most body tissues
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What color are intermediate tissues on an ultrasound?
gray
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What is echogenicity?
- how much does the matter reflect echos
- quality of the echo produced by ultrasound waves in different matter
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What are the different echogenicity?
- anechoic
- hypoechoic
- isoechoic
- hyperechoic
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How many echos does anechoic produce?
none
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What color is anechoic?
black
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Where do we see anechoic?
pure water
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How many echos does hypoechoic produce?
few echos
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Where do we does hypoechoic?
water or fluid with particles, urine, blood
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What color is hypoechoic?
dark gray to black
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How many echos does isoechoic produce?
about the same number of echos
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What color is isoechoic?
shades of gray on screen
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What is isoechoic?
soft tissue densities
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How many echos are hyperechoic?
excessive echos
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What does hyperechoic look like?
white
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What things are hyperechoic?
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Can we use barium for an ultrasound? Why or why not?
no - it reflects
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What kind of contrast material can we use for an ultrasound?
can inject bolus of saline with little air bubbles into the jugular vein to watch it go through the heart
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Is ultrasound safe?
yes - no ionizing radiation and can be used repeatedly
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Is ultrasound invasive?
no
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Does ultrasound require sedation?
- no
- not painful, no strange positions, patient tolerates it well, decreases cost
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Other than looking at structures, what can ultrasound be good for?
- permits guided aspiration or biopsy of lesions in internal organs
- place needle correctly
- avoid vital structures (example - large blood vessels)
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What are some disadvantages to using ultrasound?
- takes time to learn to use and evaluate
- ultrasound shows cross sections - need to learn to interpret
- equipment is expensive
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Are we able to distinguish between soft tissue densities and liquid densities using ultrasound? Xrays?
- Ultrasound: yes
- X-rays: no
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Is ultrasound hazardous? X-ray?
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Can you examine the internal structures of organ using ultrasound? X-ray?
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Are we able to examine structure in real time using ultrasound? X-ray?
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Does ultrasound give us a large, over-all picture? X-ray?
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Why do we need to prep the patient for an ultrasound?
to prevent the presence of air between the patient and transducer
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How do we prep the patient for ultrasound?
- clip closely to remove hair
- apply contact gel
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Why do we need to clip the hair before ultrasound?
hair holds air next to the skin and clipping the hair removes scales, dirt and debris
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Why do we use contact gel for ultrasound?
- for better skin contact
- air displacement
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What is the transducer?
hand-held probe
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What does the transducer contain?
piezoelectric crystals
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What are the piezoelectric crystals for?
when electricity is passed through the crystal, the crystal vibrates and produces ultrasound waves
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What are the different types of transducers?
- linear array
- sector scanners
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What is a linear array transducer?
several crystals placed side by side
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What kind of image does a linear array transducer produce?
rectangular image
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What does the linear array transducer look like?
"in line" or "T" shaped
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Linear array has a large _____.
footprint or contact area
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What is a linear array transducer good for?
transrectal reproductive exams in cattle and horses
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What is a sector scanner?
the crystal sweeps back and forth across the area
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What does a sector scanner image look like?
wedge shaped image
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What does a sector scanner look like?
probe shape - rod or cone shaped
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What size footprint does a sector scanner have?
small
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What is the sector scanner commonly used for?
- can put between ribs
- commonly used in small animals
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Why do we use different transducers or change the settings?
to get different frequencies of ultrasound waves
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Different frequencies have different size _____.
crystals
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What is the 3.5 MHz frequency used for?
- deep penetration
- less resolution
- big dog, horse abdomen
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What is the the 5 MHz frequency used for?
- medium penetration
- medium resolution
- medium to big dog abdomen
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What is the 7.5 MHz frequency used for?
- shallow penetration
- very good resolution
- cat and small dog abdomens, eyes, tendons of horse
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What does the transducer do?
- transmits and receives sound waves
- integrates picture and displays it on the screen
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Transducer transmits about _____ of the time. Transducer receives about _____ of the time.
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Returning sound is converterd to _____.
electrical energy
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What are the different types of display modes?
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What is the B-mode?
brightness mode
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What does the B-mode produce?
- most recognizable images
- "real time" or "static" images
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What are "real time" images?
sees structures as they are at that moment
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What does "real time" allow us to do?
view and evaluate the motion of a structure
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What is a "static" image?
can freeze a frame of a real time image
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What is M-mode?
motion mode
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What scanner is used for M-mode?
sector scanner
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What do the crystals in the sector scanner do?
crystals stays still, sees things moving past it
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What kind of images does the M-mode produce?
rectangular image with squiggly lines
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Is the M-mode used often in veterinary medicine?
no
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What is the M-mode mainly used for?
echocardiography
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What does the M-mode measure in echocardiography?
thickness of heart walls, valves, and great vessels
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What are the different ultrasound artifacts?
- acoustic shadowing
- acoustic enhancement
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What is acoustic shadowing?
area of darkness occurring deep to a dense structure
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What is acoustic enhancement?
area of brightness occurring deep to a fluid-filled structure
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How do we clean the ultrasound equipment?
wipe off probes and units as needed with water or mild disinfectants
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Can we clean the ultrasound equipment with alcohol?
no because it will damage the surface
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What are some clinical uses for ultrasound?
- tendon evaluation
- thoracic
- reproductive
- cardiac
- abdominal
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What kind of animals do we usually use ultrasound to evaluate tendons?
horses
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What happens to tendons when they are injured?
the parallel fibers pull apart and fill with blood
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What do we need in order to look into the thorax?
"acoustic window"
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Where do we look between or beneath to see structures in the thorax?
between or beneath the ribs
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What can you detect in the thorax using ultrasound?
- consolidtaed lung
- fluid in or around lungs
- collapsed lung
- masses in lung if not surrounded by air
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When can you use ultrasound to diagnose pregnancy in mares? Dogs?
- mares: day 14
- dogs: day 18 - 20
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What do we evaluate about the fetus during an ultrasound?
- heart beat
- bone formation
- gas (cause - decomposition of dead tissue)
- count fetuses
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What do we evaluate about the heart during an ultrasound?
- see valves move
- measure thickness of walls
- measure contractility
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What do we evaluate about abdominal organs during an ultrasound?
- masses in liver
- calculi in bladder
- ovarian cysts
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What kind of mass evaluation do we do with ultrasound?
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What do we evaluate about the eye during an ultrasound?
- detached retina
- mass behind eye
- prolapsed lens
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Other than evaluating structures, what can we use ultrasound for?
- guidance for fine needle aspiration (example - cysto)
- guidance for biopsy
- guidance for culture
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