Ch. 5 Physics: Intensities Flashcards
Refers to distance or space.
Spatial (space/location)
True or false:
An US beam has the same intensity at different locations
False. They do not have the same intensity at different locations.
Refers to all time, pulse duration and receiving.
Temporal (time)
True or false:
The pulsed beam does not have the same intensity at different times.
True
Refers to the transmit time only.
(the average intensity of the pulse duration only)
Pulsed
Defines the maximum value of intensity measured at a given time or place.
Peak
Defines the averaged value of intensity that is measured along a beams path (spatial) or during the time it is sent (temporal).
Average
Describes the effects that the intensity of the ultrasound beam will have.
Bioeffects
The intensity of a sound beam will vary depending on _______ and ______ it is measured
Where (spatial/location) and when (temporal/ time)
The intensity of an ultrasound beam varies at different _______ along its path.
depths
The intensity will also be different at varying ____________ locations (center > periphery)
side to side
Pulsed ultrasound is mostly ___________ (receiving) time with a small amount of __________ (transmitting)
listening
talking
Isp
Spatial peak intensity
Isp is the beams intensity at the ___________________________
Location where it is maximum
Isa
Spatial average intensity
Isa is the average intensity across the beams entire ___________________________
Cross sectional area
True or false:
Spatial peak intensity is always higher than the spatial average intensity.
True
Itp
Temporal peak intensity
What does the Itp measure?
the intensity of a beam at the point in time of its maximal value
Imax
Average intensity temporal peak
Measures the average intensity during the most intense half- cycle of a wave. Average intensity of the wave in which the temporal peak was obtained.
Imax
Ipa
Pulse average intensity
Measures the average intensity during the pulse duration only.
Ipa
Ita
Temporal average intensity
Measures the average intensity during the entire PRP including both the transmit and receive times.
Ita
What are the intensities in increasing order?
Ita
Ipa
Imax
Itp
What is the highest intensity?
Itp
What is the second highest intensity?
Imax
What is the third highest intensity?
Ipa
What is the lowest intensity?
Ita
is a measurement at the location of maximum intensity, and the instant in time when the most powerful part of the pulse passes.
SPTP
is a measurement at the location of maximum intensity, averaged over the pulse duration (transmitting time only)
SPPA
is a measurement at the location of maximum intensity, and averaged over the PRP (transmitting and receiving)
SPTA
Is a measurement of the beam cross section area and over all of time.
SATA
Which intensity factor is most closely correlated to tissue heating?
SPTA
What are the units for all intensities?
Watts/cm^2
