PulsedWaveDoppler

PulsedWaveDoppler is a Doppler ultrasound technique that uses short-duration acoustic pulses to sample blood flow velocities at a specific location along the ultrasound beam. Often referred to as Pulsed Wave Doppler (PWD), it provides depth-resolved velocity information, unlike continuous-wave Doppler which samples along the entire beam.

Operation relies on time-gated reception. The transducer emits pulses and, after a short listening period, processes echoes from a chosen depth, known as the sampling volume or gate. The Doppler frequency shift between transmitted and received signals is proportional to the velocity component along the beam, and is displayed as a spectral trace over time. The apparent velocity depends on the angle between the blood flow and the ultrasound beam.

Key parameters include the sampling gate location, the pulse repetition frequency (PRF), and the Nyquist limit, which constrains measurable velocities to avoid aliasing. By adjusting depth and gate size, clinicians can sample flow in vessels or cardiac chambers and quantify peak systolic and end-diastolic velocities, as well as flow patterns.

Clinical applications encompass cardiovascular and peripheral vascular assessment. In cardiology, PulsedWaveDoppler evaluates valvular stenosis and regurgitation, diastolic function via transmitral flow, and intracardiac flow patterns. In peripheral vessels, it quantifies stenosis and assesses flow in carotid, renal, and limb arteries.

Limitations include angle dependence, as only the velocity component along the beam is measured; aliasing at high velocities when PRF is insufficient; reliance on operator technique for accurate angle and gate placement; and lower sensitivity to very slow flows. Safety is governed by ultrasound exposure guidelines; PulsedWaveDoppler is non-ionizing and widely used in clinical imaging.