Which Doppler technique can provide range resolution and a variable sample size?

The correct choice is Pulsed Doppler because this technique utilizes a series of short bursts or pulses of ultrasound waves, allowing for precise control over the depth at which the Doppler measurements are taken. This characteristic enables range resolution, meaning that it can differentiate between signals coming from different depths, specifically identifying the location of the flow being measured.

Pulsed Doppler's ability to adjust the sample volume provides flexibility in choosing the size of the area from which blood flow data is obtained. This is crucial in vascular studies as it allows the operator to focus on specific regions of interest and adapt the sample size based on the patient’s anatomy or the clinical question at hand.

In contrast, Color Doppler primarily provides spatial information of flow direction and velocity across a larger area, but it does not allow the same level of fine control regarding range and sample size as Pulsed Doppler. Continuous Wave (CW) Doppler, while excellent for measuring high-velocity flows, lacks the ability to provide range resolution, making it difficult to ascertain the exact depth of the signal. Spectral analysis, while related to Doppler techniques, does not inherently provide varying sample sizes or range resolution as it primarily refers to the interpretation and visualization of Doppler signals for assessing blood flow characteristics