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SPI Chapter 5
Intensities
Question | Answer |
---|---|
What is intensity? | a beam's power divided by its area |
What are the 5 terms related to the intensities of pulsed waves? | spatial, peak, average, temporal, pulsed |
What is spatial? | distance or space |
What is peak? | maximum value |
What is average? | middle value |
What is temporal? | time, transmit and receive |
What is pulsed? | only transmit time |
Does an ultrasound beam have the same intensity at different depths or different side-to-side locations within the beam? | No |
What are the 2 spatial considerations? | spatial peak intensity (Isp) and spatial average intensity (Isa) |
What is spatial peak intensity (Isp)? | the beam's intensity at the location where it is maximum |
What is spatial average intensity (Isa)? | the average intensity across the beam's entire cross-sectional area |
Which on is always higher than the other, Isp or Isa? | Isp |
During pulsed ultrasound is the transducer receiving, then it is transmitting? | Yes |
What is temporal peak intensity (Itp)? | measuring the intensity of the beam at the instant time of its maximum value |
What is (Imax)? | measuring the half cycle |
What is pulse average intensity (Ipa)? | pulse duration or the transmit time |
What is temporal average Intensity (Ita)? | PRP or both transmit and receive time |
What are the 4 temporal considerations from largest to smallest intensities? | Itp, Imax, Ipa, Ita |
What is Isptp? | measured at location where intensity is maximum and the time of the most powerful pulse passes |
What is Isppa? | measured at location where intensity is maximum and averaged over time (both transmit and receive times) |
What is Isata? | measured over entire cross-sectional area of sound beam and over all time |
How many different methods to measure and report intensities are there? | 6 |
What is the unit that all intensities have? | W/cm^3 |
Intensities may be reported in various ways in respect to what? | time and space |
The different measurements of intensities are important in what study? | bioeffects |
Which intensity measurement id the most relevant intensity with respect to tissue heating? | SPTA |
Which intensity measurements have the highest value? | SPTP |
Which intensity measurements have the lowest value? | SATA |
What is beam uniformity coefficient? (also called SP/SA factor) | a number that describes the spread of a beam in space, the SP/SA factor is unitless w/ value of 1 or greater |
The duty factor describes... | the relationship of beam intensities with time, it is unitless and has a value between 0 and 1 |
For continuous wave the beam is always "on" therefore... | pulse average and temporal average intensities are the same, SPTA = SPPA and SATA = SAPA |
When pulsed and continuous wave sound beams have the same STPT intensities, the continuous wave beam has which higher intensity? | SPTA |
When pulsed and continuous wave sound beams have the same SATP intensities, the continuous wave beam has which higher intensity? | SATA |
Rank the intensities from largest to smallest. | SPTP, Imax, SPPA, SPTA, SATA |