Fast Fourier Transform Analysis of Doppler Ultrasound Signals

We evaluated the peak systolic maximum velocity (Vmax) of the right HA, right PV, and HA resistive index (HARI) for the controls and all patients using the FFT analysis of Doppler ultrasound signals just before CEUS. The FFT analysis of the Doppler ultrasound signals was performed as described in previous reports, and the procedure is summarized as follows: The Aplio500 ultrasound scanner (Canon Medical Systems) was used with a 3.5‐MHz convex transducer ultrasound probe. The ultrasound scanning was performed with the patient in the supine position. The Doppler ultrasonography was used initially for the detection of the right HA and right PV, and a Doppler waveform was obtained (Supporting Fig. S1A,B). The Vmax and the end‐diastolic flow velocity (Vmin) were obtained after correcting for the angle of insonation, and then HARI ([Vmax‐Vmin]/Vmax) was calculated.