Commandments Flashcards
1
Intensities may be reported in various ways with respect to time and space
2
The different measurements of intensities are important in the study of bioeffects. SPTA intensity is the most relevant intensity with respect to tissue heating
3
All intensities have units of watts/cm^2
4
Because peak measurements are larger than average measurents, SPTP intensity has the highest value, and SATA has the lowest value
5
A number called the beam uniformity coefficient (also called SP/SA factor) describes the spread of a beam in space. The SP/ SA factor is unitless, with a value of 1 or greater
6
The duty factor describes the relationship of beam intensities with time. The duty factor is a unitless number with a value of 0 and 1
7
For continuous wave ultrasound, the beam is always “on” and the pulse average and temporal average intensities are the same. Thus . . .
SPTA = SPPA and SATA = SAPA
8
When pulsed and continuous wave sound beams have the same SPTP intensities, the continuous wave beam has the higher SPTA intensity
* When pulsed and continuous wave sound beams have the same SATP intensities, the continuous wave beam has the higher SATA intensity
9
Temporal peak intensity (Itp) is maximum in time
- Im intensity is averaged over the most intense half cycle
- Pulse average intensity (Ipa) is averaged over the most intense half cycle
- Pulse average intensity (Ipa) is averaged only during the pulse duration (“on” time only)
- Temporal average intensity (Ita) is averaged during PRP ( both the “on” and “off” times)
10
Spatial peak intensity (Isp) is the maximum in space
*Spatial average intensity (Isa) is averaged over the cross-sectional area of the beam
Rank of intensities from largest to smallest
SPTP–>Im–>SPPA–>SPTA–>SATA
Intensity measurement methods
SPTP SATP SPTA SATA SPPA SAPA
