CHAPTER 4 DESCRIBING PULSED WAVES

To describe pulsed sound we need these 5 parameters

1. Duty Factor

2. Pulsed duration

3. PRF

4. PRP

5. SPL

Which type of wave CANNOT create anatomic images ?

CW

to create every detail of anatomy, what is needed ?

Short burst or pulses of acoustic energy

A collection of cycles that travel together, it needs a beginning and ending

pulse

although a pulse is of individual cycles, how does it move ?

as a single unit

a pulse consist of ______ but propagates as a _____ unit

a pulse consist of individual cycles but propagates as a single unit

a pulse ultrasound consist of 2 components

1. transmit, talking, on time

2. receive, listening, off time

the actual time from the start of that pulse to the end of that pulse is ?

Pulse Duration

how is pulse duration determined ?

sound source

units of pulse duration ?

time (microseconds)

can pulse duration be adjusted?

No

Formula for pulse duration ?

pulse duration = # cycles x period

pulse duration = # cycles / frequency

Pulse duration is directly related to _________ and ________

#cycles of each pulse and period

pulse duration in inversely related to _____

frequency

Long duration pulses consist of :

• many cycles in the pulse

• individual cycles with long periods

short duration pulses consist of :

• few cycles in the pulse

• individual cycles with short periods

in clinical imaging, a pulse typically contains how many pulses?

2-4

which pulse created greater accuracy images ?

short duration pulses

what is SPL

The distance from the start of the pulse to the end of that pulse

what are the units of SPL

mm (distance)

SPL is determined by ?

sound source and medium

can SPL be adjusted ?

no

what is the formula for SPL ?

spl (mm) = #cycles x wavelength (mm)

SPL is directly related too ____and _____

• #of cycles

• wavelength

SPL is inversely related to ______

frequency

which type of length is needed for accurate images?

Shorter length