2 Ch. 4: Describing Pulsed Waves Flashcards
(45 cards)
In diagnostic u/s, ___ wave sound cannot create anatomic images.
continuous
Define ‘pulsed sound’.
Short bursts of acoustic energy produced by imaging systems to create anatomic pictures; a collection of cycles that travel together.
Pulse duration is…
the actual time from the start of a pulse to the end of that pulse aka transmit/talking/”on” time.
Pulse duration is reported in units of…
time, such as microseconds.
Pulse duration is determined by the…
sound source only.
Is pulse duration adjustable?
No.
Pulse duration is equal is the ___ in each pulse multiplied by the ___of each cycle.
number of cycles/period
Pulse duration is ___ proportional to the # of cycles in the pulse.
directly. The more cycles, the longer the duration.
Pulse duration is ___ proportional to the period.
directly. The longer the individual period of the cycles, the longer the duration.
Pulse duration is ___ proportional to the frequency.
inversely. The higher the frequency, the shorter the duration must be.
What two characteristics create pulses of LONG duration?
Pulses of long duration have either 1) many cycles in the pulse or 2) individual cycles with long periods.
What two characteristics create pulses of SHORT duration?
Pulses of short duration have either 1) few cycles in the pulse or 2) individual cycles of short period.
(Shorter/Longer) duration pulses are desirable for imaging because they create images of greater accuracy.
shorter
Define ‘spatial pulse length’.
The distance that a pulse ocupies in sace from the start to the end of a pulse.
Spatial pulse length is reported in units of…
distance, such as mm.
Spatial pulse length is determined by…
both the source and the medium (because the wavelength of each cycle is determined by both, so is spatial pulse length).
Is spatial pulse length adjustable?
No.
Spatial pulse length is equal is the ___ in each pulse multiplied by the ___of each cycle.
of cyles/wavelength
Spatial pulse length is ___ proportional to the # of cycles in each pulse.
directly. The more cycles, the longer the length.
Spatial pulse length is ___ proportional to wavelength.
directly. The longer the individual wavelengths, the longer the pulse length.
Spatial pulse length is ___ proportional to frequency.
inversely. The higher the frequency, the shorter the length must be.
What two characteristics create long pulses?
Long pulses have either 1) many cycles in the pulse or 2) cycles with longer wavelengths.
What two characteristics create short pulses?
Short pulses have either 1) fewer cycles in the pulse or 2) cycles with shorter wavelengths.
Define ‘pulse repetition period’.
The time from the start of one pulse to the start of the next pulse (one ‘on’ time and one ‘off’ time).
