Fetal heart hemodynamics have been investigated in detail using both spectral and color Doppler ultrasound.Both techniques are based on Doppler frequency shift and allow a quantification and visualization of blood flow according to its direction and velocity.Power Doppler ultrasound (PDU) uses the Doppler technique as well but, in contrast to conventional Doppler, the amplitude of the signal rather than the frequency shift is encoded.Therefore, the analyzed signals are not proportional to velocity and direction but to the power inherent to blood cell motion and thus strength of the signal.Recently, several reports on this technique have been published in this Journal as original papers, case reports or pictures of the month.They have shown how this method completes the spectrum of diagnostic tools used in obstetric and gynecological ultrasound.Because PDU is reported to be 3 -5 times more sensitive at signal detection than conventional color Doppler, and due to its relative angle independence, it has mainly been applied in visualizing vessels with tiny diameters, low velocities (e.g. in tumors) or a horizontal course.The main features and possible advantages of PDU are 1 :
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Chaoui et al. (2001) studied this question.
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