physics exam 2 - Pulsed Wave Doppler

pulsed wave doppler used the ___-ranging technique

echo

Pulsed wave utilizes ___ crystal

one

In Pulsed wave doppler the doppler pulse duration is __-__ cycles is usually longer than in B-mode which is __-__ cycles

5-30, 2-3

Pulsed wave doppler provides good ___ resolution

range

Pulsed wave doppler allows signals to be recieved from specific ____

locations

Pulsed wave doppler: ___ pulses with ___ cycles give more info and are what we want

long, more

Pulsed wave doppler: can have up to ___ cycles per pulse

30

PW doppler gate = allows ___ and ___ switching

on, off

gate = _____ _____

sample volume

"Sample volume" = the site where the __ signal originates

doppler

____ ____ allows for the sonographer to determine the depth, velocities, and location of blood flow sampling

sample volume

_____ outside of the sample volume are not assessed nor displayed

velocities

Sample volume ___ and ___ can be adjusted by the sonographer

width, size

the pulsed wave doppler voltage generator has a ____

Gate

PW doppler generator provides continuous ____ to drive the transducer

voltage

The "gate" converts the continuous ____ into ____ ____

voltage, voltage pulses

PRF = # of ____ / ____ emitted by the transducer

pulses / sec

The deeper the sample volume the ____ the transducer waits to receive the returning echoes

longer

The deeper the sample volume the ___ the time interval between ___

longer, pulses

The deeper the sample volume the ____ the PRF

lower

increase in depth = ____ in time and ____ in PRF

increase, decrease

Limitations on Velocity Detection: minimally ___ pulses are needed to define the beat frequency unambiguously

2

Max Doppler shift that can be detected is related to the sampling ___ and or ___

rate or PRF

a ___ PRF is required to measure structures moving at high velocities and produce and high DS

high

A high PRF limits the ___ of sampling

depth

DS is depended on the transducer ____

frequency

Vmax = ___^2 / 8 __ x ___ x cos theta

c, f, d

If depth is increased then the maximum velocity measured is ____

decreased

Lower frequency transducers allow _____ velocities to be detected

higher

If the doppler angle is increased the maximum velocity limit is ____

increased

The maximum measurable velocity / "the highest frequency in a sampled signal that can be represented unambiguously" = ___ ___

Nyquist Limit

Nyquist Limit = 1/2 (___)

PRF

___ and transducer ____ play a role in determining maximum velocity that can be measured

PRF, frequency

Nyquist Limit ___ with increased sample volume depth

increases

Higher velocity measurements requires a proportionally higher ____

PRF

When PRF increases that causes the Nyquist limit to ____

increase

____ occurs when velocity exceeds the Nyquist limit or when it exceed 1/2PRF

Aliasing

A ___ wave is used to plot a doppler signal and each pulse is determined by an ____

sine, arrow

The frequency needs to be ___ than the actual doppler signal

lower

Aliasing is heaving associated with _____

stenosis

Aliasing is an ____

artifact

Aliasing causes ___ around of the spectrum, so the signal appears ___ in frequency than the actual signal

wrapping, lower

Aliasing: The PRF is __x the doppler frequency being sampled, so it exceeds the ____ ____

2, nyquist limit

Eliminating Aliasing: adjusting the sample volume ____ to be as superficial as possible, this ___ the PRF

depth, increases

Eliminating Aliasing: use a ____ frequency transducer which gives a ___ frequency doppler shift for a given velocity

lower, lower

Eliminating Aliasing: adjust ____ scale

velocity

Eliminating Aliasing: Adjust zero ____ to double the displayed maximum frequency or velocity

baseline

lower frequency detects ____ velocities

higher

Higher PRF = ____ Nyquist Limit

Higher

Eliminating Aliasing: ___ the doppler angle

increase

Eliminating Aliasing: use ___ wave doppler mode

continuous

Eliminating Aliasing: Use ___ PRF mode

higher

High Pulse Repetition Frequency (HPRF) allows for more than ___ pulse traveling through tissue at a time

one

HPRF provides more than one ___ volume or ___ on the image

sample, gate

If 2 gates are placed in 2 separate vessels, then ___ ___ will occur in a PW Doppler

range ambiguity

High PRF Doppler allows the detection of ___ Doppler Shifts

high