Which Doppler method employs individual frequencies displayed by the FFT (Fast Fourier Transform) method?

The correct answer, spectral analysis, is a method that utilizes the Fast Fourier Transform (FFT) to analyze the frequency components of the Doppler signal. When blood is flowing, the Doppler effect causes the frequency of the echoes received by the ultrasound transducer to change according to the velocity of the moving blood cells. Spectral analysis, through FFT, breaks down these echoes into their constituent frequencies, allowing for a detailed representation of flow velocity and direction over time.

This technique is particularly useful in assessing vascular flow patterns and allows for the visualization of various components of the flow, such as peak velocities and the presence of turbulence. By converting the time domain signal into frequency domain data, spectral analysis provides a graph (the spectral Doppler waveform) that displays the velocity of blood flow as a function of time, making it an essential tool in vascular ultrasound assessments.

The other methods mentioned play different roles in Doppler ultrasound. Color Doppler represents blood flow information through color coding, Pulse Wave Doppler uses discrete sampling to measure blood flow at a specific depth, and Continuous Wave Doppler measures high-velocity flow but does not provide spectral analysis as it does not use FFT. Understanding the purpose and function of each method clarifies how spectral analysis uniquely fits this role.