Bioeffects/Safety Flashcards
Hydrophones are used to measure:
Pressure or intensity
Calorimeter is calibrated to measure:
Total power in sound beam through process of absorption
Thermocouple is a tiny electronic thermometer placed into:
The sound beam and temp is measured
Temperature rise is indirectly related to amount of power.
T/F
False, directly
What is dosimetry?
Science of identifying and measuring the characteristics of an ultrasound beam that are relevant to its potential for producing biological effects
In vivo means:
In the living
In vitro means:
In glass
Pressure is defined as
Forced divided by area
Pressure measured in:
Pascals
Peak pressures are measured with:
Hydrophone
Power is:
Rate at which work is performed
Watts or milliwatts
What can be used to measure power of ultrasound beam?
Calorimeters
RAdiation force devices
Thermocouple devices
Intensity is:
Power divided by area
W/cm^2 or mW/cm^2
Intensity is measured at:
Or:
Peak value
Average value
Radiation force balance or scale measures intensity or power by:
Measuring force the beam exerts on balance/scale
Output of hydrophone is calibrated to:
Indicate pressure or intensity
How big is a hydrophone probe?
Less than 1 mm in diameter
What is SATA?
Spatial average, temporal average
Lowest intensity measurement
Measured during PRP
SPTA
Spatial peak, temporal average
Pulsed ultrasound intensities
Measured during PRP
Used when discussing data concerning bio effects
SAPA
Spatial average, pulse average
Average intensity that occurs in pulse
Measured during PD
SPTP
Spatial peak, temporal peak
Highest values of all intensity measurements
Intensity that exists at the spatial peak when beam is on
Measured during PD
SATP
Spatial average temporal peak
Describes pulsed ultrasound intensities
Measured during pulse duration
SPPA
Measures/calculates average intensity within pulse
Only measured during pulse duration
In continuous wave, SATA = ?
And SPTA = ?
SATA = SATP SPTA = SPTP
Where can you find the SPTA values for various operating modes?
In the operators manual for each machine
Gray scale imaging intensity and power
1-200mW/cm^2
1-20mW
M mode intensity and power mode
70-130 mW/cm^2
1-5 mW
Pulsed Doppler intensity and power
20-290 mW/cm^2
2-20 mW
Color Doppler intensity and power
10-230mW/cm^2
2-20 mW
Thermal index is the ratio of:
Acoustic power produced by transducer to power required to raise tissue temp by 1 degree C
