Chapter 19: SPI Study Guide Part 2

Doppler doesn't always provide a valid estimate of the speed of blood cells because the shift is related to the ___ of the angle between the direction of the beam and the direction of blood flow.

• sine

• tangent

• cosine

• cotangent

Two otherwise identical Doppler studies are performed, except that the angle between flow and the sound beam is 0 degrees in the first study and 60 degrees in the second. The velocity measured in the first study is 2 m/s. What velocity will be measured in the second study?

• 2 m/s

• 4 m/s

• 1 m/s

• cannot be determined

Answer explanation

Maximum velocities are measured at a zero degree angle. Only one-half of the true velocity is measured when the angle is 60 degrees.

What is true of the Doppler shift when the sound beam is normally incident to the velocity of the red blood cells?

• it is at maximum

• it is half of the maximum

• it is absent

• it is at minimum

A maximum Doppler shift is obtained when the angle between the direction of blood flow and the direction of the sound beam is ___

• 10 degrees

• 90 degrees

• 180 degrees

• 270 degrees

True or False

The appearance of negative velocities on the spectral display of a continuous wave Doppler exam always indicates that red blood cells are moving away from the transducer.

• True

• False

True or False

Regarding the CW Doppler, a minimum of two distinct PZT crystals are in the transducer

• True

• False

True or False

Regarding to CW Doppler, problems with aliasing significantly limits its clinical utility.

• True

• False

True or False

Regarding to CW Doppler, frequencies measured at the transducer are produced from many different locations along the ultrasonic beam

• True

• False

True or False

Regarding to CW Doppler, the duty cycle of the continuous wave is 100%

• True

• False

All of the following are related to dedicated continuous wave Doppler transducers except

• wide bandwidth

• high quality factor

• higher sensitivity

• range ambiguity