|Title of Invention||
"AN IMPROVED APPARTUS FOR ULTRASONOGRAPHY USING A CONTINUOUS WAVE DOPPLER SYSTEM.'
|Abstract||This invention relates to an improved apparatus for ultrasonography using a continuous wave Doppler system which is capable of diagnostic assessment in a low budget environment. This apparatus comprises an oscillator, a transducer for issuing ultrasonic signal to blood vessel, an analog to digital converter and an spectrum analyser.|
|Full Text||-2 -
The present invention relates to an improved apparatus for ultrasonography using a continuous wave Doppler system which is capable of diagnostic assessment in a low budget environment.
In existing ultrasonography apparatus, pulsed wave and continuous wave Doppler systems are used. The hardware cost of pulsed wave Doppler system is such higher compared to systems using continuous wave. Multitarget Doppler system using pulsed wave and continuous wave has the added advantage of imaging along with spectogram which is not opossible in systems using continuous wave alone as continuous wave gives spectogram only.
In existing ultrasonography apparatus, the interpretation of the spectogram obtained from the spectrum analyser and the interpretation of the images are solely dependent on the knowledge of the human expert.
One objective of the present invention therefore, is to
provide a cost effective ultrasonography apparatus. Using a
continuous wave Doppler system the hardware overhead is
Another objective of the present invention is to do the speed spectrum analysis at high speed.
Yet another objective of the present invention is to provide automatic clinical interpretation of the spectrum and diagnosis
with the help of built-in expert system or medical knowledge base. Of course the expert can always upgrade the medical knowledge base built in the system and make his own clinical interpretation based on his knowledge.
According to the present invention, a cost effective continuous wave doppler system is used which can do high speed spectrum analysis by using a fast Fourier transform (FFT) unit the architecture of which is based on a rnultiplierless coordinate rotation digital, computer (CORDIC) for better spectrum analysis and for preventing data loss- The FFT unit is implemented by application specific integrated circuit (ASIC) using field programmable gate arrays CFPGA)- Due to its reconfigurable capability, FPGA realization is very much useful and effective.
Thus the present invention provides an improved apparatus for ultrasonography using a continuous wave Doppler system,comprising an oscillator and transducer for issuing ultrasonic signal to the blood vessel, a plurality of oscillators and mixers for down converting the carrier frequency of the Doppler shifted modulated signal to about 20 KHz, an analog to digital CA/D) converter for converting analog data to digitized data, a spectrum analyser comprising a fast Fourier transform (FFT) unit and random access memories RAM I and RAM II for accessing data from said A/B converter and from said FFT unit in a time sharing mode for displaying the power spectrum in a display unit characterized in
that the architecture of said FFT unit is based on a multiplierless CORDIC unit (16) implemented by ASIC using field programmable gate arrays.
The invention can now be explained in detail with the help of accompanying drawings, where:
Figure 1 is a schematic block diagram of the present invention, the continuous wave Dappler ultrasonography system;
Figure 2 shows the FPBA implementation of the spectrum analyser of the present invention.
As shown in Fig. I, an ultrasonic signal generated by the oscillator 3 and issued from the transducer 2 is passed to the blood vessel 1. The transducer 2 is piezoelectric crystal (PZT)-The backscattered signal is received at the detector of the transducer 2- Doppler shift is introduced by the moving blood cells. The backscattered signal is modulated by the Doppler shifted frequency (?f) over the incident frequency (fo). To detect the Doppler shifted frequency the modulating signal is extracted in a stepwise procedure-The Doppler shifted frequency is in the audio range and the carrier frequency is S MHz. Direct extraction of Doppler frequency from the modulated signal may lead to unwanted complications. A superheterodyne structure is used for the amplitude modulation (AM) detection of the Doppler shifted frequency- The carrier frequency of the modulated signal at the transducer output is down converted in steps to 20 KHz through 455 KHz by means of local oscillators 5 and 9 and mixers 6 and 8.
After passing through the low pass filter 10 and amplifier 11, the a-nalog data at the frontal end is digitized in an analog to digital (A/D) converter.
The fast Fourier transform (FFT) is performed over the data at the FFT unit which is based on coordinate rotation digital computer(CORDIC) unit 16. The CORDIC FFT unit is implemented through field programmable gate arrays (FPGA). A raultiplierless structure using CORDIC as the basic processing element used for the FFT block makes it less hardware complex circuit than multiplier based circuits-
The block level structure of the spectrum analyzer 13 is shown in Fig.2- The spectrum analyzer 13 (shown in Fig.l) has two random access memory structure, switches and SWII and control the modes of RAM I and RAM II respectively. The data from analog to digital converter 12 and from FFT unit 16 are accessed by the 2-RAM structure in a time sharing mode.
At a particular time instant, the analog to digital converter 12 puts the data in one RAM, say RAM II while the spectrum analyzer 13 takes over the other RAM, say RAM I for FFT computation of the spectrum.
Once RAM I is filled up, the two RAMs are swapped by the
switches SWI and JMU and the spectrum analyzer 13 works on the
new set of data in the other RAM,i.e.RAM I.
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In the present invention 128 point FFT is done and the power spectrum is displayed in display unit 14 in spectogram format. Colour coding is done according to the intensity level of the individual frequencies.
The spectrum analyser 13 can be coupled to a processor 15 through ISA bus (not shown). The spectogram obtained form the display unit 14 of the ultrasonography apparatus of the present invention can be supported by the artificial intelligent system acting as medical knowledge base stored in the processing unit 15 that is capable of automatic interpretation of the spectrogram, The salient features of the spectrogram are analyzed. Feature vector space is mapped to a symptom vector space. This is done for a non-linear hyperspace. Artificial neutral network has been used for the classification of the feature vector space. Features from each spectrogram are extracted and fed to the relevant network. Classification of the network comes on a predefined grouping based on age and region of probing. Suprvised training is used for the network. Diagnostic view about a patient is ex tractable from a set of spectrogram using a Bayesian probabilistic network, Measure of belief (MB) or disbelief (MB) basically a joint probabilistic measure, is calculated from the priori probability assigned for each disease due to the symptoms from the knowledge base. Thus a set of spectrograms from one patient can give the most probable disease(s).
WE CLAIM :
1. An improved apparatus for ultrasonography using a continuous
wave Doppler systent,comprising :
an oscillator (3) and transducer (2) for issuing ultrasonic signal to the blood vessel;
a plurality of oscillators (5,9) and mixers (6,8) for down converting the carrier frequency of the Doppler shifted modulated signal to about 20 KHZ
an analog to digital (A/D) converter (12) for converting analog data to digitized data;
a spectrum analyser (13) comprising a fast Fourier transform
(FFT) unit and random access memories RAM I and RAH II for
accessing data from said A/D converter (12) and from said FFT
unit in a time sharing mode for displaying the power spectrum in
a display unit (14)
characterized in that the architecture of said FFT unit is based on a multiplierless CORDIC unit (16) implemented by ASIC using field programmable gate arrays.
2. The apparatus as claimed in claim I, wherein the ultrasonic
signal is in the range of 3 to 15 MHz,say S MHz.
3. The apparatus as claimed in claim 1, wherein said spectrum
analyser (13) is coupled to a processor unit (15) for clinical
interpretation of spectrograms obtained from said display unit
(14) by medical knowledge base stored in said processing unit
4. An improved apparatus for ultrasonography substantially as
herein described and illustrated in the accompanying drawings.
This invention relates to an improved apparatus for ultrasonography using a continuous wave Doppler system which is capable of diagnostic assessment in a low budget environment. This apparatus comprises an oscillator, a transducer for issuing ultrasonic signal to blood vessel, an analog to digital converter and an spectrum analyser.
|Indian Patent Application Number||00293/CAL/2000|
|PG Journal Number||17/2007|
|Date of Filing||19-May-2000|
|Name of Patentee||"INDIAN INSTITUTE OF TECHNOLOGY"|
|Applicant Address||KHARAGPUR 721 302 AN INDIAN INSTITUTE.|
|PCT International Classification Number||A61B 5/02,|
|PCT International Application Number||N/A|
|PCT International Filing date|