04-10-2014, 02:30 PM
Implementation of zoom FFT in ultrasonic blood flow analysis using VLSI
technology
IMPLEMENTATION.pdf (Size: 768 KB / Downloads: 13)
AB STRACT
An adequate blood flow supply is necessary for all organs of the body. Analysis of the blood
flow finds its importance in the diagnoses of diseases. There are many techniques for
analyzing the blood flow. These techniques are not affordable by the poor people because of
their high expense. So we have implemented a technique called Zoom-FFT. This technique
is simple and affordable to detect the blood clots and other diseases. Here a specific
application will be dealt i.e., ultrasonic blood flow analyzer using ZOOM FFT. The
implementation must be achieved with a single VLSI chip in order for the system to be both
cost-effective and power efficient and thus widely accepted.
Introduction
Blood flow analysis[1] is done by passing a high frequency
ultrasonic wave in the blood vessels through a transducer
(transmitter). The reflected signal from the receiver Transducer
has a different frequency due to the Doppler principle. This
signal is passed to a MATLAB Simulink input to find the
frequency spectrum. Because of the high frequency of the
ultrasonic wave, the resolution of the frequency spectrum output
will not be good. Therefore we go for advanced Zoom FFT
technique, wherein a very small frequency change due to the clot
formation can be obtained with a good resolution. It can be used
to locate the initial presence of a blood clot. All of these tasks
must be achieved with a single VLSI chip for the system to be
both cost-effective and power efficient.
Doppler Effect Phenomenon:
A shift in frequency (f) of the wave will be expected due to
the source and observers motion relative to each other[1]. If the
distance between them is reduced or increased. That shift in
frequency depends on the velocity of sound which also depends
on density of the medium, in which it propagates. When a
small object (eg.Blood clot) is situated in the path of the sound
wave, the wave will be resisted (scattered). A direct
measurement of this velocity will provide useful information
Real Blood Flow Analysis:
In an Ultrasonic blood flow analysis, a beam of ultrasonic
energy is directed through a blood vessel at a shallow angle and
its transit time is then measured[1]. Morecommon are the
ultrasonic analyzers based on the Doppler principle. An
oscillator, operating at a frequency of several Mega Hertz,
excites a piezoelectric transducer[6]. This transducer is coupled
to the wall of an exposed blood vessel and sends an ultrasonic
beam with a frequency F into the flowing blood. A small part of
the transmitted energy is scattered back and is received by a
second transducer arranged opposite the first one as shown in
Fig.2. Because the scattering occurs mainly as a result of the
moving blood cells. The reflected signal has a different
frequency due to a Doppler effect.
Conclusion:
Currently the paper has been tested on the simulation basis,
the output of the simulations are satisfactory Fig.8.(a),(b). Real
time experimentation is being done, using the Piezo electric
ultrasonic transducer for verification purpose. Our plan is to
implement in to a single VLSI chip.