Ultrasound Flashcards
conversion
mechanical energy produced by sound waves absorbed by body tissues and changed to thermal energy
transducer
converts electrical energy into acoustical energy via pizoelectrical effect
transducer head sizes vary from 1-10 cm. what is the most commonly used?
5cm
how do you pick a transducer size?
based on size of treatment area
effective radiating area (ERA)
the area of the transducer from which the ultrasound radiates
what determines the treatment depth?
output frequency
1 MHz output is for _____ tissues and 3 MHz is for ________ tissues.
deep, superficial
is adipose tissue transparent to ultrasound?
yes
does 3 MHz or 1 MHz have more scattering of sound waves?
3, therefore less is available for deeper tissues
what kind of ultrasound is applied to achieve thermal effects? what about non-thermal effects?
continuous
non-continuous
T or F: ultrasound energy is uniformly distributed over the surface of the transducer
F: the center ishotter than the edges, this is why you have to move it around
bean non-uniformity ratio
spatial peak intensity: spatial average intensity
why do you want a low BNR?
more uniform energy and therefore less risk of tissue damage
BNR should be less than ______:1
6
spatial average intensity
total power (watts) / area of transducer head (cm^2)
duty cycle
fraction of time the ultrasound energy is on over one pulse period
a duty cycle of less than ____% is considered pulsed
50
_______ ultrasound is used in subacute and chronic conditions where _______ ultrasound is better for acute stages
continuous
pulsed
temporal peak intensity
peak intensity of ultrasound during the on time phase of the pulse period
temporal average intensity
the ultrasound power averaged over one pulse period
attenuation
reduction of acoustical energy as it passes through soft tissue
what affects attenuation? (3)
absorption
reflection
refraction
what tissues have increased absorption?
tissues with high collagen and protein
ex. bones, muscles, tendons, ligs, capsules
thermal effects of ultrasound
increased tissue temp
pain threshold
collagen tissue extensibility
enzyme activity
tissue perfusion
alteration of NCV
is cavitation an effect of thermal or non-thermal ultrasound?
non-thermal
cavitation
alternating compression and expansion of small gas bubbles in tissue fluids caused by mechanical pressure waves
T or F: stable cavitation results in tissue damage
F: but unstable cavitation does (ex. cancer treatment)
acoustic streaming
movement of fluids along the boundaries of cell membranes resulting from mechanical pressure wave
* may produce cellular changes and accelerate healing
parameters:
1 HMz
100% duty cycle
1.75 w/cm^2
how long would you need to treat?
about 10 minutes to increase temp by 4 degrees C
parameters:
3MHz
100% duty cycle
1.5 w/cm^2
how long would you need to treat?
about 4 minutes to increase temp by 4 degrees C
goals of ultrasound (4)
1 - modulate pain
2- increase tissue extensibility
3 - reduce/eliminate acute inflammation
4 - accelerate healing
precautions of ultrasound
acute inflammation
epiphyseal plates
fractures
breast implants
T or F: symptoms may increase after the initial ultrasound treatment
T
contraindications of ultrasound
acute injuries
impaired circulation
DVT
impaired cognition
impaired sensation
thrombophlebitis
joint cement
plastic components
over cancerous tumors
over vital areas
over pacemakers
over active infection
T or F: ultrasound treats a limited area
T
treatment area should be _______ times the size of the ERA
2-3
direct contact mediums
gel or lotion
*water based only
indirect contact mediums
- water immersion (tap water, saline)
- gel or water bladder
T or F: ultrasound energy can pass through air
F: this is why you need a water based coupling medium
how fast should you move the ultrasound head?
SLOWLY, 4cm/sec
your patient has a rash but you really think they could benefit from ultrasound therapy. what could you do?
put saran wrap on first, then put the gel on top. saran wrap transmits the energy well
when would you use an immersion technique?
for irregularly shaped areas
how do you hold the ultrasound head during immersion technique
about 1 inch away from body part, the water is your medium
ultrasound treatment duration depends on (3)
1 - size of treatment area
2 - output intensity
3 - goals
what sensations are expected during thermal (continuous) ultrasound? what about pulsed?
warmth for thermal
nothing for pulsed
your pt is experiencing some pain during ultrasound treatment. what can you do?
- move the sound head faster
- use a lower duty cycle
- lower the intensity
phonophoresis
use of ultrasound to drive meds through the skin into deeper tissues
ex. lidocane
do you use continuous or pulsed ultrasound for phonophroesis
continuous
ultrasound + e-stim is often used to treat (2)
trigger points
muscle spasms
