Key result
Theoretical calculations of the probability distribution density for instantaneous frequency and the variance of mean frequency estimators characterize ultrasonic Doppler signals in blood velocity.
This study provides a mathematical foundation for understanding the probability distribution density of instantaneous frequency in ultrasonic Doppler signals, which is relevant for blood velocity measurements.
May enhance Doppler signal interpretation for blood velocity; leaves open clinical validation in cardiovascular ultrasound.
The relationship between the instantaneous frequency and the mean frequency of ultrasonic Doppler signals in blood velocity measurements is discussed. The probability distribution density for the instantaneous frequency is calculated. The time interval histogram (TIH), which has been used to characterize the Doppler signal, is found to be an approximation of this probability density. The probability density will also describe the output of phase-lock loop analysis of the Doppler signal. The variance of mean frequency estimators is calculated, and the implication of this for practical estimators is discussed. The effect of hard limiting of the signal on the estimator performance is also discussed.
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Bjørn Angelsen (1981) studied Ultrasonic blood velocity Doppler signals. Mean frequency estimators was evaluated. Theoretical calculations of the probability distribution density for instantaneous frequency and the variance of mean frequency estimators characterize ultrasonic Doppler signals in blood velocity.
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