Final answer:
When using 4.5 MHz continuous wave Doppler, there is no maximum velocity cap; it can measure any high blood flow velocity without the aliasing limitations that affect pulsed wave Doppler.
Step-by-step explanation:
When a sonographer switches to a 4.5 MHz continuous wave (CW) Doppler, they are using a technology that can measure velocities without an upper limit. Therefore, the answer to the question of what the maximum velocity cap will be at a depth of 5 cm, when using continuous wave Doppler is: a. There will not be a maximum velocity cap with CW Doppler. Continuous wave Doppler allows for the measurement of high blood flow velocities that pulsed wave Doppler cannot measure accurately due to the phenomenon known as 'aliasing'. With CW Doppler, high velocities can be measured because it continuously emits and receives ultrasound waves, thus it does not suffer from the same limitations of pulsed wave Doppler.