REAL-TIME DIGITAL PROCESSING OF DOPPLER ULTRASOUND SIGNALS AND CALCULATION OF FLOW PARAMETERS

Vascular diseases and their complications are responsible for around 2 7% of deaths in Brazil [1]. Doppler ultrasound is a non-invasive techn ique that has been used to study blood flow in intact blood vessels si nce Satomura first reported the potential of the technique in 1959. Be cause it is non-invasive it makes sequential studies and those in norm als feasible. Whereas in contrast angiography only vessel anatomy is d isplayed, Doppler ultrasound produces dynamic information on blood-flo w. It may be used to estimate flow-rates, to image regions of blood fl ow (colour Doppler), and to help in locating sites of arterial disease , thus complementing X-ray examinations [2]. This paper describes a sy stem based on a Digital Signal Processor for real-time spectrum analys is of Doppler ultrasound signals, real-time display of sonograms, and calculation and analysis of three parameters of clinical interest deri ved from the Doppler signal [3]. The system comprises a TMS320C25 deve lopment board, which acquires the signal and performs spectrum analysi s, and a microcomputer, which reads the spectral estimates, displays t hem as a sonogram in real-time and calculates a set of spectral parame ters proposed in the literature. The system permits a maximum sampling frequency of 40.96 kHz, and in the sonogram, 80 power spectra per sec ond (each with 128 frequency bins) are displayed. In a preliminary stu dy, the stability of the haemodynamic parameters and their dependence on a user-defined threshold value is investigated.