Measurement of blood flow

Claim 1

An apparatus for measuring instantaneous velocity or acceleration of blood in a blood vessel, the apparatus comprising

Claim 2

An apparatus for measuring instantaneous velocity or acceleration of blood in a blood vessel, the apparatus comprising

Claim 5

the apparatus being characterised by having means (110 or 302 to 316) for tracking a predetermined portion of the spectrum, provided that, when the predetermined portion is a high frequency edge of the spectrum, the Doppler signal is modulated up to a frequency above 100 kHz, to obtain a tracking signal representative of velocity,

Claim 6

the apparatus being characterised by having means (110 or 302 to 316) for tracking a predetermined portion of the spectrum, provided that, when the predetermined portion is a high frequency edge of the spectrum, the Doppler signal is modulated up to a frequency above 100 kHz, to obtain a tracking signal representative of velocity,

Claim 12

An apparatus for non-invasively measuring blood flow in a blood vessel comprising: ultrasonic probing means for obtaining a Doppler signal having a frequency spectrum including an audio frequency portion caused by Doppler shifting due to reflection of ultrasonic energy from moving components of the blood in the blood vessel; means for producing a signal representative in value to the instantaneous velocity of the blood components including an automatic frequency control circuit employing a local oscillator producing a signal of a frequency greater than 100 kHz.

Claim 13

An apparatus for non-invasively measuring blood flow in a blood vessel comprising: ultrasonic probing means for obtaining a Doppler signal having a frequency spectrum including an audio frequency portion caused by Doppler shifting due to reflection of ultrasonic energy from moving components of the blood in the blood vessel; means for producing a signal representative in value to the instantaneous velocity of the blood components including an automatic frequency control circuit employing a local oscillator producing a signal of a frequency greater than 100 kHz.

Claim 14

An apparatus for measuring blood flow through a blood vessel comprising: means for obtaining a Doppler signal produced by Doppler shifting an ultrasonic signal by reflection from moving blood in the blood vessel; an automatic gain control circuit for normalizing the power in the frequency spectrum of the Doppler signal during the heartbeat while preserving the frequency distribution in the spectrum, including means for summing the Doppler signal with a sinusoidal signal having a frequency lower than any Doppler frequency shift to be evaluated, and maintaining the peak to peak amplitude of the summed signal at an approximately constant value; and means for tracking Doppler frequency shift in the Doppler signal as it varies during the heartbeat and producing a signal representative in value of a blood flow parameter.

Claim 15

An apparatus for measuring blood flow through a blood vessel comprising: means for obtaining a Doppler signal produced by Doppler shifting an ultrasonic signal by reflection from moving blood in the blood vessel; an automatic gain control circuit for normalizing the power in the frequency spectrum of the Doppler signal during the heartbeat while preserving the frequency distribution in the spectrum, including means for summing the Doppler signal with a sinusoidal signal having a frequency lower than any Doppler frequency shift to be evaluated, and maintaining the peak to peak amplitude of the summed signal at an approximately constant value; and means for tracking Doppler frequency shift in the Doppler signal as it varies during the heartbeat and producing a signal representative in value of a blood flow parameter.

Claim 16

An apparatus for measing the mean velocity of blood flowing in a blood vessel comprising: transducer means for producing ultrasonic energy directed at blood flowing in the blood vessel; means for receiving ultrasonic reflected by blood components flowing in the blood vessel and for electronically extracting audio frequency Doppler shift signals from the reflected and received ultrasonic energy; a first electronically controlled filter a second electronically controlled filter, wherein the Doppler shift signal is applied to each of the electronically controlled filters and wherein said filters selectively pass different portions of the audio frequency spectrum of the Doppler shift signal; feedback circuit means for providing a signal for controlling the first and second filter so that the portion of the Doppler shift signal passed by each filter maintain a predetermined relationship to one another, said feedback signal being related in value to the instantaneous mean velocity of moving, reflecting components of the blood in the blood vessel.

Claim 17

An apparatus for measing the mean velocity of blood flowing in a blood vessel comprising: transducer means for producing ultrasonic energy directed at blood flowing in the blood vessel; means for receiving ultrasonic reflected by blood components flowing in the blood vessel and for electronically extracting audio frequency Doppler shift signals from the reflected and received ultrasonic energy; a first electronically controlled filter a second electronically controlled filter, wherein the Doppler shift signal is applied to each of the electronically controlled filters and wherein said filters selectively pass different portions of the audio frequency spectrum of the Doppler shift signal; feedback circuit means for providing a signal for controlling the first and second filter so that the portion of the Doppler shift signal passed by each filter maintain a predetermined relationship to one another, said feedback signal being related in value to the instantaneous mean velocity of moving, reflecting components of the blood in the blood vessel.

Claim 18

A method of measuring instantaneous velocity or acceleration of blood in a blood vessel, the method comprising: obtaining (32, 52, 54, 56, 60), from ultrasonic energy, a Doppler signal having a frequency spectrum determined by relative movement of the components of the blood in a blood vessel, tracking (110 or 302 to 316) a predetermined portion of the spectrum, provided that, when the predetermined portion is a high frequency edge of the spectrum, the Doppler signal is modulated up to a frequency above 100 kHz, to obtain a tracking signal representative of velocity, and optionally differentiating (152 or 320) the tracking signal to obtain a signal representative of acceleration.

Claim 19

A method of measuring instantaneous velocity or acceleration of blood in a blood vessel, the method comprising: obtaining (32, 52, 54, 56, 60), from ultrasonic energy, a Doppler signal having a frequency spectrum determined by relative movement of the components of the blood in a blood vessel, tracking (110 or 302 to 316) a predetermined portion of the spectrum, provided that, when the predetermined portion is a high frequency edge of the spectrum, the Doppler signal is modulated up to a frequency above 100 kHz, to obtain a tracking signal representative of velocity, and optionally differentiating (152 or 320) the tracking signal to obtain a signal representative of acceleration.

Claim 20

A method for measuring instantaneous peak acceleration in blood flow through a blood vessel, comprising the steps ' of: (a) directing ultrasonic energy at blood flowing in the blood vessel; (b) receiving ultrasonic energy reflected by blood components flowing in the blood vessel; (c) electronically extracting audio frequency Doppler shift signals from the reflected and received ultrasonic energy; (d) mixing the audio frequency Doppler shift signal with a signal having a frequency greater than 100 kHz generated by a local oscillator; (e) filtering the mixed signal; (f) controlling the local oscillator responsive to said filtered signal to vary the frequency of the local oscillator signal so that a portion of a side band of the mixed signal, corresponding to a high frequency edge of the spectrum of the Doppler shift signal, is maintained in a pass band of the fitter; and (g) differentiating with respect to time the filtered signal to produce a signal representative in value to the instantaneous peak acceleration of the blood flow.

Claim 21

A method for measuring instantaneous peak acceleration in blood flow through a blood vessel, comprising the steps ' of: (a) directing ultrasonic energy at blood flowing in the blood vessel; (b) receiving ultrasonic energy reflected by blood components flowing in the blood vessel; (c) electronically extracting audio frequency Doppler shift signals from the reflected and received ultrasonic energy; (d) mixing the audio frequency Doppler shift signal with a signal having a frequency greater than 100 kHz generated by a local oscillator; (e) filtering the mixed signal; (f) controlling the local oscillator responsive to said filtered signal to vary the frequency of the local oscillator signal so that a portion of a side band of the mixed signal, corresponding to a high frequency edge of the spectrum of the Doppler shift signal, is maintained in a pass band of the fitter; and (g) differentiating with respect to time the filtered signal to produce a signal representative in value to the instantaneous peak acceleration of the blood flow.

Claim 22

A method for measuring blood flow through a blood vessel, comprising the steps of: obtaining a Doppler signal produced by Doppler shifting of an ultrasonic signal by reflection from moving blood in the blood vessel; summing the Doppler signal with a continuous sinusoidal signal having a frequency less than about 1000 Hz; electronically maintaining said summed signal at an approximately constant amplitude during the heartbeat and electronically tracking frequency components of the approximately constant amplitude signal to produce a signal representative in value of the velocity of the blood.

Claim 23

A method for measuring blood flow through a blood vessel, comprising the steps of: obtaining a Doppler signal produced by Doppler shifting of an ultrasonic signal by reflection from moving blood in the blood vessel; summing the Doppler signal with a continuous sinusoidal signal having a frequency less than about 1000 Hz; electronically maintaining said summed signal at an approximately constant amplitude during the heartbeat and electronically tracking frequency components of the approximately constant amplitude signal to produce a signal representative in value of the velocity of the blood.