Lecture 4

Question 1

Pulsed Ultrasound Technique

Answer 1

• Short burst of sound sent out.
• Wait for sound to bounce off reflector and return to transducer.
• Sound changed into electrical voltage that can be processed by the ultrasound machine.

Question 2

To properly place the echo on the display, the US unit must know:

Answer 2

• The strength or amplitude of the echo. (Mirrors the reflector’s strength or amplitude)
• Anatomic location of the reflector generating the echo.

Question 3

What is a pulse?

Answer 3

• Short burst of sound energy.
• Collection of a number of cycles that travel together.
• Each pulse has a beginning, middle, and end.

Question 4

Pulse Duration

Answer 4

• The time (duration) of the ultrasound pulse.

- PD= Period number of cycles in pulse.

Question 5

Pulse Duration Equation

Answer 5

PD = number of cycles/frequency

Units: microseconds (us)

Question 6

Pulse Duration increases if:

Answer 6

• Period increases.
• # of cycles in pulse increases.
• Frequency decreases.

Question 7

Pulse Repetition Period (PRP)

Answer 7

• The time from the beginning of one pulse to the beginning of the next pulse.
• When depth decreases, PRP decreases.

Question 8

PRP EQUATION

Answer 8

PRP = pulse duration + idle/listening time

Question 9

Pulse Repetition Frequency (PRF)

Answer 9

• Number of pulses of sound the ultrasound transducer emits in 1 sec.
• Units: Hz or kHz
• Typically 1-10 kHz
• When distance decreases, PRF increases.
• Sound source (MFG) determines PRF.

Question 10

Duty Factor (DF)

Answer 10

• The fraction of time the the ultrasound machine is sending out a pulse of sound.
• NO UNITS!