Understanding Ultrasound Physics: chpt 4
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Created by:
CarrieMines on August 27, 2010
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Description:
Pulsed ultrasound, pulsed duration, spatial pulse length pulse repetition period and frequency
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25 terms
Terms | Definitions |
|---|---|
 pulsed sound | a collection of cycles that travel together |
| two components of pulsed untrasound | transmitting and receiving |
| pulse duration is | not adjustable, reported in units of time, determined by sound source, typical duration is .3-2 μs |
| pulse duration = | # cycles x period |
| pulse duration = | # cylces x frequency |
| pulse duration is | -directly proportional to the # of cylces in the pulse -directly proportional to period -inversely proportional to the frequency |
| a pulse typically contains | 2-4 cycles |
| which type of pulses create greater accuracy? | shorter duration pulses |
| spatial pulse length is | not adjustable, has units of distance, is determined by both the source and medium, typically ranges from .1-1 mm |
| spatial length is | -directly proportional to the # of cycles in the pulse -directly proportional to wavelength - inversely proportional to frequency |
| pulse repetition period | includes one pulse duration plus one listening time |
| pulse repetition is | adjustable by depth of the view, is reported in units of time, determined by the sound source and the imaging depth, is generally 100-1,000 x longer than pulse duration |
| the time from one pulse to the next is shorter when | imaging shallow depths |
| the time from one pulse to the next is longer when | imaging more deeply |
| the markers along the edge of an image indicate | depth |
| pulse repetition and imaging depth are | directly related |
| two components of pulse repetition period (PRP) | transmit time, receive time |
| by changing the imaging depth, sonographers alter | -PRP -PRF -duty factor |
| pulse repetition frequency (PRF) | is the # of pulses that is transmitted into the body each second |
| pulse repetion frequency is | adjustable by depth of the view, reported in units of Hz, is determined by sound source, typcial value is 1,000-10,000 Hz |
| PRF is only related to | depth of view |
| the relationship between PRF and depth is they are | inverserly related |
| the relationship between PRP and PRF is they are | recipricols |
| duty factor is | adjustable by depth of th view, is reported as a % of time, is determined by the sound source, ranges from .2%-.5% (100% for CW) |
| the relationship between duty factor and imaging depth is they are | inversely related |
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