Ultrasound Flashcards
(30 cards)
effective radiating area (ERA)
a measure of the cross sectional area of the ultrasound beam as it exits the metal end plate, expressed in sq cm
beam nonuninformity ratio (BMR)
should be less than or equal to 6:1
Therapeutic ultrasound application
musculoskeletal tissue healing & pharmacological (phonophoresis)
Thermal effects
Tissue temperature rise
TTR occurs in tissues w/ highest collagen content (tendonds, ligaments, joint capsules, fascia
Thermal effects
Ultrasound compared to superficial heat modalities:
heats deeper tissues greater than superficial heat modalities & heats much smaller areas
Factors that determine TTR
Collagen content
Reflection of US at tissue boundaries
Changes in tissue blood flow
US parameters
Clinical application techniqie
Frequency of ultrasound (3 MHz heats faster than 1 MHz)
Nonthermal effects of US
Mechanical:
Cavitation
Acoustic streaming
Microstreaming
Effect on cellular metabolism
Clinical techniques
Coupling medium
must be formulated to transmit ultrasound
use of:
* gel
* lotion
* water
* solid gel pads
ultrasound technique
Selection of an ultrasound device:
must be calibrated
electrical safety check
BNR no more than 6:1
ERA usually size of sound head
hands on vs hands off
number of different size transducers
BNR setting
no more than 6:1
ERA size
usually size of sound head
Parameters
Frequency
1 MHz for deeper tissues
3MHz for superficial tissues
Parameters
Mode
Continuous ultrasound=greater heating
Pulsed ultrasound=less heating
Parameters
Intensity of continuous ultrasound
total power output (Watts) over the effective radiating area (ERA) in cm = Spatial Average Intensity (SAI)
Paramters
Intensity of pulsed ultrasound
depends on percentage of pulses
ultrasound clinical techniques
- warm sound head and/or gel
- apply gel to sound head
- spread gel on skini
- set parameters
- activate device and immediately begin moving sound head
- move at about 4cm/second
- maintain contact of sound head on skin at all times
Importance of keeping ultrasound transducer head in correct position?
Must keep head perpendicular to the skin surface at all times to limit reflection of sound waves
How large of an area can be treated with ultrasound?
must limit area treated to about 4x the ERA of the transducer sound head
Ultrasound does NOT effectively head large areas of tissue such as:
muscles, neck & back, large joints such as hips and knees
When TTR is desired, how long should ultrasound continue?
For at least 10 minutes after pt reports warmth
Options if patient reports discomfort?
Decrease intensity
Move sound head slightly faster
Apply more coupling agent
Switch to pulses
Discontinue
Options if TTR is desired but no warmth reported
increase intensity
decrease movement speed
check contact of sound on skin
switch to contunious
change frequency
continue until warmth is reported
discontinue
Documentation of ultrasound
- Parameters (continuous or pulsed including duty cycle, frequency, duration)
- Location and/or tissue treated
- Patient’s response
Documentation of intensity during ultrasound?
Usually not documented bc it varies
