# Shared Flashcard Set

## Details

Understanding Ultrasound Physics Ch.4-5
Ultrasound Physics Ch. 4-5 Chapter Questions
15
Physics
Not Applicable
05/04/2016

Term
 What is a pulsed sound?
Definition
 A collection of cycles that travel together.
Term
 What characteristics distinguish pulses with long duration from those with short duration?
Definition
 Long duration:  Many cycles in the pulse, or individual cycles with long periods. Short duration:  Few cycles in the pulse, or individual cycles with short pulses.       In clinical imaging, a pulse typically contains 2-4 cycles.
Term
 Which type of pulse is more desirable in diagnostic imaging, and why?
Definition
 Shorter pulse durations.  They create images of greater accuracy.
Term
 What is the difference between pulse duration & spatial pulse length?
Definition
 Pulse Duration: The time that a pulse is “on”. Measured in microseconds (us). PD (us) = # cycles x P (us)   OR    PD (us)  = # cycles                                                                                  F                                                                Spatial Pulse Length: The distance of the pulse end to end.  Measured in millimeters (mm).   SPL (mm) = # cycles x λ (mm)
Term
 Which characteristics distinguish pulses with long pulse length from those with short length?
Definition
 Long:  1. Many cycles in the pulse.  2. Cycles with longer wavelengths.   Short:  1. Fewer cycles in the pulse.  2. Cycles with shorter wavelengths.
Term
 Which type of pulse is more desirable in diagnostic imaging, and why?
Definition
 Short.  They create better pictures.
Term
 What is depth of view?
Definition
 The maximum distance into the body that an ultrasound system is imaging. (Controlled by the sonographer.)
Term
 How are pulse repetition period and depth of view related?
Definition
 Directly related.  ↑ Depth = ↑ PRP              Depth (mm) ȣ   PRP (us)                                           PRF (MHz)
Term
 What are the 2 components of PRP?  Which one can the sonographer change?
Definition
 Transmit time (aka: Pulse Duration) & receive time.      The sonographer can alter the receiving time by adjusting the imaging depth.
Term
 How are PRF (transmit time) and depth of view related?
Definition
 Inversely related.  ↑ Depth = ↓ PRF The deeper (increase) the depth, the fewer (decrease) pulses transmit into the body. Depth (mm) ȣ   PRP (us)                                PRF (MHz)
Term
 How is Duty Factor calculated?
Definition
 DF (%)  =    PD (us)     x  100                 PRP (us)
Term
 What are the maximum & minimum values for duty factor?
Definition
 Maximum:  100% or 1.0.  Only with continuous waves. Minimum:   0% (off time) Typical Value:  0.2% with anatomic imaging.
Term
 How does the sonographer change duty factor?
Definition
 By changing the imaging depth.
Term
 Of the 4 temporal (time-related) intensity measurements, which has the highest value?
Definition
 Temporal Peak
Term
 Rank the 5 intensities from largest to smallest.
Definition
 1. SPTP  2. Im  3. SPPA  4. SPTA   5. SATA
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