Blood flow measurement device and method
First Claim
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1. An apparatus for measuring instantaneous peak velocity in blood flow through a blood vessel, comprisingmeans for obtaining a Doppler signal having a frequency spectrum determined by Doppler shifting of an ultrasonic signal caused by relative movement of components of the blood in the blood vessel;
- andmeans for tracking a high frequency edge of said frequency spectrum to produce a signal representative in value to the instantaneous peak velocity of the blood components, said tracking means including means for modulating said Doppler signal up to a frequency above 100 kHz.
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Abstract
The disclosure relates to systems for measuring blood flow by detecting Doppler shift of ultrasound reflected by blood components moving in a blood vessel. The systems employ electronic techniques for providing accurate tracking of portions of the frequency spectra of Doppler shift signals to determine peak and means velocity and acceleration.
65 Citations
27 Claims
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1. An apparatus for measuring instantaneous peak velocity in blood flow through a blood vessel, comprising
means for obtaining a Doppler signal having a frequency spectrum determined by Doppler shifting of an ultrasonic signal caused by relative movement of components of the blood in the blood vessel; - and
means for tracking a high frequency edge of said frequency spectrum to produce a signal representative in value to the instantaneous peak velocity of the blood components, said tracking means including means for modulating said Doppler signal up to a frequency above 100 kHz. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method for measuring instantaneous peak acceleration in blood flow through a blood vessel, comprising the steps of:
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(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 filter; 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. - View Dependent Claims (10)
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11. An apparatus for noninvasively measuring blood flow in a blood vessel comprising:
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ultrasonic probing means for obtaining a Doppler signal caused by Doppler shifting due to reflection of ultrasonic energy from moving components of the blood in the blood vessel including means for demodulating the Doppler signal to produce an audio frequency Doppler signal; and means for receiving said audio frequency Doppler signal and for producing a signal representative in value to the instantaneous peak velocity of the blood components including modulation means employing a local oscillator producing a signal of a frequency greater than 100 kHz.
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12. An apparatus for measuring blood flow through a blood vessel comprising:
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means for obtaining a Doppler signal produced by Doppler shifting of an ultrasonic signal by reflection from moving blood in the blood vessel; an automatic gain control circuit for receiving said Dopper signal and for normalizing the power in the frequency spectrum of said Doppler signal during the heart beat 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. - View Dependent Claims (13, 14, 15, 16)
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17. A method for measuring blood flow through a blood vessel, comprising the steps of:
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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 heart beat; and electronically tracking frequency components of the approximately constant amplitude signal to produce a signal representative in value of the velocity of the blood. - View Dependent Claims (18, 19, 20, 21)
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22. An apparatus for measuring the mean velocity of blood flowing in a blood vessel comprising:
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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.
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- 23. The apparatus of claim 23 wherein the said audio frequency Doppler signal is band-limited and the spectrum of the band-limited signal is divided into a high pass portion and a low pass portion by the first and second filters, respectively.
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24. The apparatus of claim 24 wherein the lower boundary frequency of the high pass portion is substantially equal to the upper boundary frequency of the low-pass portion.
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26. The apparatus of claim 26 further comprising means for differentiating the feedback control signal to obtain a signal related in value to the instantaneous mean acceleration of the reflection components of the blood.
Specification