Ultrasonic continuous wave blood flowmeter using Doppler effect analysis

Claim 2

An ultrasonic continuous wave blood flowmeter using Doppler effect analysis on ultransonic signals echoed from a living body, comprising: transducing means, having a transmission element and a reception element, for outputting an ultrasonic signal to irradiate the living body and for transducing a reflected ultrasonic signal from the living body into an electric reception signal; detecting means, operatively connecting to said transducing means, for orthogonally detecting the electric reception signal and for outputting a Doppler detection signal; "filter means, operatively connected to said detecting means, for cutting high frequency components of the Doppler detection" signal above a cut-off frequency and for outputting an analog signal; converting means, operatively connected to said filter means, for converting the analog signal of said filter means to a digital signal based on a Doppler sampling frequency having a continuous wave; transforming means, operatively connected to said converting means, for analyzing the digital signal to obtain a Doppler frequency spectrum based on a Fourier transform method, the Doppler frequency spectrum including a representation of bloodstream distribution in the living body; and control means, operatively connected to said filter means, for controlling the cut-off frequency based on the Doppler sampling frequency and a zero shift value decided manually, the zero shift value determining an extent of the Doppler frequency spectrum to be displayed.

Claim 3

An ultrasonic continuous wave blood flowmeter using Doppler effect analysis on ultransonic signals echoed from a living body, comprising: transducing means, having a transmission element and a reception element, for outputting an ultrasonic signal to irradiate the living body and for transducing a reflected ultrasonic signal from the living body into an electric reception signal; detecting means, operatively connected to said transducing means, for orthogonally detecting the electric reception signal and for outputting a Doppler detection signal; filter means, operatively connected to said detecting means, for cutting high frequency components of the Doppler detection signal above a cut-off frequency and for outputting an analog signal; converting means, operatively connected to said filter means, for converting the analog signal of said filter means to a digital signal based on a Doppler sampling frequency having a continuous wave; transforming means, operatively connected to said converting means, for analyzing the digital signal to obtain a Doppler frequency spectrum based on a Fourier transform method; and control means, operatively connected to said filter means, for controlling the cut-off frequency based on the Doppler sampling frequency and a zero shift value decided manually, said control means comprising: a first register for temporarily storing the zero shift value; a second register for temporarily storing the Doppler sampling frequency; an erasable programmable read only memory, operatively connected to said first and second registers, for storing a relationship to convert from the zero shift value and the Doppler sampling frequency to a digital value representing the cut-off frequency; and a digital-to-analog converter, operatively connected to said erasable programmable read only memory and said filter means, for converting the digital value to an analog voltage for controlling said filter means.

Claim 4

An ultrasonic continuous wave blood flowmeter using Doppler effect analysis on ultransonic signals echoed from a living body, comprising: transducing means, having a transmission element and a reception element, for outputting an ultrasonic signal to irradiate the living body and for transducing a reflected ultrasonic signal from the living body into an electric reception signal; detecting means, operatively connected to said transducing means, for orthogonally detecting the electric reception signal and for outputting a Doppler detection signal; filter means, operatively connected to said detecting means, for cutting high frequency components of the Doppler detection signal above a cut-off frequency and for outputting an analog signal; converting means, operatively connected to said filter means, for converting the analog signal of said filter means to a digital signal based on a Doppler sampling frequency having a continuous wave; transforming means, operatively connected to said converting means, for analyzing the digital signal to obtain a Doppler frequency spectrum based on a Fourier transform method; and control means, operatively connected to said filter means, for controlling the cut-off frequency based on the Doppler sampling frequency and a zero shift value decided manually, said control means comprising: a first register for temporarily storing the zero shift value; a second register for temporarily storing the Doppler sampling frequency; an erasable programmable read only memory, operatively connected to said first and second registers, for storing a relationship to convert from the zero shift value and the Doppler sampling frequency to a digital value representing the cut-off frequency; and a digital-to-analog converter, operatively connected to said erasable programmable read only memory and said filter means, for converting the digital value to an analog voltage for controlling said filter means.

Claim 5

An ultrasonic continuous wave blood flowmeter for detecting blood flow in a living body, comprising: control means including means for storing a Doppler sampling frequency and a zero shift value, both manually set by an operator; Doppler signal means for irradiating the living body with an ultransonic signal and for detecting echoes of the ultrasonic signal emanating from the living body to produce a Doppler detection signal; filter means for cutting high frequency components of the Doppler detection signal above a cut-off frequency determined in dependence upon the Doppler sampling frequency and the zero shift value to produce a filtered signal; and analysis means for analyzing the filtered signal to obtain a Doppler frequency spectrum including a representation of bloodstream distribution in the living body, the Doppler frequency spectrum having a range partially determined by the zero shift value.

Claim 6

An ultrasonic continuous wave blood flowmeter for detecting blood flow in a living body, comprising: control means including means for storing a Doppler sampling frequency and a zero shift value, both manually set by an operator; Doppler signal means for irradiating the living body with an ultransonic signal and for detecting echoes of the ultrasonic signal emanating from the living body to produce a Doppler detection signal; filter means for cutting high frequency components of the Doppler detection signal above a cut-off frequency determined in dependence upon the Doppler sampling frequency and the zero shift value to produce a filtered signal; and analysis means for analyzing the filtered signal to obtain a Doppler frequency spectrum including a representation of bloodstream distribution in the living body, the Doppler frequency spectrum having a range partially determined by the zero shift value.

Claim 7

An ultransonic continuous wave blood flowmeter as claimed in claim 3, wherein said filter means comprises: converter means for converting the Doppler sampling frequency and the zero shift value into an analog voltage; and low-pass filter means for filtering the high frequency components of the Doppler detection signal above the cut-off frequency, selected in dependence upon the analog voltage.

Claim 8

An ultrasonic continuous wave blood flowmeter as claimed in claim 4, wherein said low-pass filter means comprises: operational amplifier means for amplifying the Doppler detection signal to produce an amplified signal; at least one voltage controlled attenuator, operatively connected to said control means, said operational amplifier means and said analysis means, for attenuating the amplified signal by a gain determined in dependence upon the analog voltage to produce the filtered signal; and feedback means for controlling frequency response provided by said operational amplifier means in dependence upon the filtered signal.