Chapter 5 Flashcards
As the transducer emits pulses, it causes _
large fluctuations of intensity in the region through which the pulses move.
Each pulse consists of multiple cycles that produce _
intensity variations within the pulse itself.
Intensity is the ultrasound beam’s _
power divided by area
Five key words are related to the intensities of pulsed waves:
- Spatial
- Peak
- Average
- Temporal
- Pulsed
Spatial refers to
Distance or space
Does an ultrasound beam have the same intensity at different locations within the beam?
No
Temporal refers to
all time, transmit and receive.
Does a pulsed ultrasound beam have to same intensity at different time?
No
Peak refers to
The maximum value
Average refers to
The mathematical middle value
Pulsed refers to
only to the transmit time (pulse duration)
Does a pulsed ultrasound beam have the same intensity at different times during the pulse.
No
Pulsed average is the _
average intensity for the pulse duration only (ignoring listening time)
MEASURING AND REPORTING SOUND BEAM INTENSITY:
The strength of a sound beam varies depending on _
the measurement point within the beam.
MEASURING AND REPORTING SOUND BEAM INTENSITY: Intensity also varies over time in pulsed ultrasound depending on
whether the system is transmitting or receiving.
SPATIAL CONSIDERATIONS: The intensity of a sound beam varies depending on
the location of the measurement
The beam’s intensity at the location where it is maximum.
Spatial peak intensity (Isp)
the average intensity across the beam’s entire cross-sectional area.
Spatial average intensity (Isa)
TEMPORAL CONSIDERATIONS: In addition to location within the beam, sound wave intensities also vary
Over time
There are _ different methods of measuring intensity in pulsed ultrasound.
4
The intensity of the beam at the instant in time of its maximal value.
Temporal peak intensity (Itp)
The time-averaged intensity over the largest half-cycle in the pulse at the spatial peak.
Maximum Intensity (Imor Imax)
The average intensity during the pulse duration (the transmit time).
Pulse average intensity (Ipa
The average intensity during the entire pulse repetition period (both transmit and receive times).
Temporal average intensity (Ita)
Temporal Intensities from largest to smallest:
- Temporal Peak Intensity
- Maximum Intensity (Imax)
- Pulse Average Intensity
- Temporal Average Intensity
COMBINING SPATIAL AND TEMPORAL FACTORS: For the study of bioeffects, the intensity characteristics of sound must be described accurately with regard to
Time and space
COMBINING SPATIAL AND TEMPORAL FACTORS: Spatial Peak Temporal Peak (Isptp): measured at the location where _
ntensity is maximum and the instant in time when the most powerful part of the pulse passes
COMBINING SPATIAL AND TEMPORAL FACTORS: Spatial Peak Pulse Average (Isppa): measured at the location where
ntensity is maximum, averaged over the transmit time (pulse duration)
COMBINING SPATIAL AND TEMPORAL FACTORS: Spatial Peak Temporal Average (Ispta): measured at the location where
ntensity is maximum and averaged over all time, both the transmit and receive times.
COMBINING SPATIAL AND TEMPORAL FACTORS: Spatial Average Temporal Average (Isata): measured
over the entire cross-sectional area of the sound beam, and over all time.
SPTP
Highest peak value
Spatial peak, temopral peak
SATP
Spatial average, temporal peak
SPTA
Most important for thermal bioeffects
Spatial peak, temporal average
SATA
Lowest value
Spatial average, temporal average
SPPA
Spatial peak, pulse average
SAPA
Spatial average, pulse average
