US4569356A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method and apparatus for detecting fetal heart rate by autocorrelation
Assignee: Nihon Kohden Corp
•
Filing: 1984-11-05
•
Granted: 1986-02-11
•
Expires: 2004-11-05
Abstract
Abstract A fetal heartbeat signal detected by the principle of an ultrasonic Doppler effect is autocorrelated, and a fetal heart rate is detected from the periodicity of peaks of a determined autocorrelation function. In such a process, peaks of the autocorrelation function are detected, and a peak truly indicative of the fetal heart rate is detected from closeness of righthand inclindations of the peaks to a righthand inclination of the origin of the autocorrelation function.
Inventors
- 👤 Shigeyuki Kyozuka
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 15:26
CPC Classifications
A; A61; A61B; A61B8/00; A61B8/02; A61B8/08; A61B8/0866; G; G01; G01S; G01S7/00; G01S7/52; G01S7/52017; G01S7/52023; G01S7/52025; G01S7/52026
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
130 words
A method of detecting a fetal heart rate, comprising the steps of: (a) emitting an ultrasonic wave to a fetal heart and converting a signal reflected by the fetal heart into an electric signal with a transducer; (b) detecting a frequency-shifted signal from the converted electric signal as a fetal heartbeat signal; (c) forming an autocorrelation function of the detected fetal heartbeat signal; (d) detecting peaks of the autocorrelation function; (e) calculating a righthand inclination of the origin of the autocorrelation function and righthand inclinations of the detected peaks; (f) detecting one of the peaks which has an inclination close to that of the origin and is closest to said origin; and (g) issuing a signal indicative of a delay time of said closest peak with respect to said origin.
Claim 2
Independent Claim
130 words
A method of detecting a fetal heart rate, comprising the steps of: (a) emitting an ultrasonic wave to a fetal heart and converting a signal reflected by the fetal heart into an electric signal with a transducer; (b) detecting a frequency-shifted signal from the converted electric signal as a fetal heartbeat signal; (c) forming an autocorrelation function of the detected fetal heartbeat signal; (d) detecting peaks of the autocorrelation function; (e) calculating a righthand inclination of the origin of the autocorrelation function and righthand inclinations of the detected peaks; (f) detecting one of the peaks which has an inclination close to that of the origin and is closest to said origin; and (g) issuing a signal indicative of a delay time of said closest peak with respect to said origin.
Claim 3
Dependent Claim
26 words
A method according to claim 1, including the step of effecting screening based on an additional decision standard prior to said step of issuing the signal.
Claim 4
Independent Claim
193 words
An apparatus for detecting a fetal heart rate, comprising: (a) a transducer for receiving an ultrasonic signal reflected by a fetal heart and converting the same into an electric signal; (b) pre-processor means for generating a fetal heartbeat signal by effecting AM detection on a frequency-shifted signal in the signal detected by said transducer; (c) an autocorrelator for forming an autocorrelation function of an output signal from said pre-processor means as a digital signal; (d) memory means for storing the autocorrelation function signal issued periodically from said autocorrelator into an address corresponding to its delay time; (e) means for detecting peaks of the signal stored in said memory means; (f) means for calculating a righthand inclination of the origin of the autocorrelation function and righthand inclinations of the detected peaks; (g) means for comparing the righthand inclination of said origin and the righthand inclinations of the peaks to detect said address of the peak within a predetermined error; and (h) means for issuing an address signal of a true peak closest to the address of said origin among said addresses detected by said detecting means as a signal indicative of a heartbeat interval.
Claim 5
Independent Claim
193 words
An apparatus for detecting a fetal heart rate, comprising: (a) a transducer for receiving an ultrasonic signal reflected by a fetal heart and converting the same into an electric signal; (b) pre-processor means for generating a fetal heartbeat signal by effecting AM detection on a frequency-shifted signal in the signal detected by said transducer; (c) an autocorrelator for forming an autocorrelation function of an output signal from said pre-processor means as a digital signal; (d) memory means for storing the autocorrelation function signal issued periodically from said autocorrelator into an address corresponding to its delay time; (e) means for detecting peaks of the signal stored in said memory means; (f) means for calculating a righthand inclination of the origin of the autocorrelation function and righthand inclinations of the detected peaks; (g) means for comparing the righthand inclination of said origin and the righthand inclinations of the peaks to detect said address of the peak within a predetermined error; and (h) means for issuing an address signal of a true peak closest to the address of said origin among said addresses detected by said detecting means as a signal indicative of a heartbeat interval.
Claim 6
Dependent Claim
38 words
An apparatus according to claim 3, wherein said peak detecting means includes means for comparing a plurality of peak patterns which can be of a true peak and are stored in another memory with said autocorrelation function signal.
Claim 7
Dependent Claim
37 words
An apparatus according to claim 3, wherein said issuing means includes screening means for determining the address of the true peak closest to the address of the origin before the address of the true peak is issued.
Claim 8
Dependent Claim
37 words
An apparatus according to claim 3, 4, or 5, further including D/A converter means for converting the peak address signal issued from said issuing means into an analog signal and supplying said analog signal to a recorder.
Claim 9
Independent Claim
137 words
A method of detecting a fetal heart rate, comprising the steps of: (a) emitting an ultrasonic wave to a fetal heart and converting a signal reflected by the fetal heart into an electric signal with a transducer; (b) detecting a frequency-shifted signal from the converted electrical signal as a fetal heartbeat signal; (c) forming an autocorrelation function of the detected fetal heartbeat signal; (d) detecting peaks of the autocorrelation function; (e) calculating the slope at a predetermined point of the origin of the autocorrelation function and the slope at a corresponding point of the detected peaks; (f) detecting one of the peaks which has a slope similar to that of the origin and is closest to said origin; and (g) issuing a signal indicative of a time delay of said closest peak with respect to said origin.
Claim 10
Independent Claim
137 words
A method of detecting a fetal heart rate, comprising the steps of: (a) emitting an ultrasonic wave to a fetal heart and converting a signal reflected by the fetal heart into an electric signal with a transducer; (b) detecting a frequency-shifted signal from the converted electrical signal as a fetal heartbeat signal; (c) forming an autocorrelation function of the detected fetal heartbeat signal; (d) detecting peaks of the autocorrelation function; (e) calculating the slope at a predetermined point of the origin of the autocorrelation function and the slope at a corresponding point of the detected peaks; (f) detecting one of the peaks which has a slope similar to that of the origin and is closest to said origin; and (g) issuing a signal indicative of a time delay of said closest peak with respect to said origin.
Claim 11
Dependent Claim
16 words
The invention in accordance with claim 7 wherein the slope is determined at a post-peak point.
Claim 12
Dependent Claim
27 words
The invention in accordance with claim 8 wherein screening is provided by the use of an additional decision standard prior to the step of issuing a signal.
Claim 13
Independent Claim
197 words
An apparatus for detecting a fetal heart rate, comprising: (a) a transducer for receiving an ultrasonic signal reflected by a fetal heart and converting the same into an electric signal; (b) pre-processor means for generating a fetal hearbeat signal by effecting AM detection of a frequency-shifted signal and the signal detected by said transducer; (c) autocorrelator for forming an autocorrelation function of an output signal from said pre-processor means as a digital signal; (d) memory means for storing the autocorrelation function signal issued periodically from said autocorrelator into an address corresponding to its delay time; (e) means for detecting peaks of the signal stored in said memory means; (f) means for calculating the slope of a predetermined point of the origin of the autocorrelation function and the slope of corresponding predetermined points of the detected peaks; (g) means for comparing the slope of said origin and the slopes of the peaks to detect the address of the peak within a predetermined error; and (h) means for issuing an address signal of a true peak closest to the address of said origin among said addresses detected by said detecting means as a signal indicative of a heartbeat interval.
Claim 14
Independent Claim
197 words
An apparatus for detecting a fetal heart rate, comprising: (a) a transducer for receiving an ultrasonic signal reflected by a fetal heart and converting the same into an electric signal; (b) pre-processor means for generating a fetal hearbeat signal by effecting AM detection of a frequency-shifted signal and the signal detected by said transducer; (c) autocorrelator for forming an autocorrelation function of an output signal from said pre-processor means as a digital signal; (d) memory means for storing the autocorrelation function signal issued periodically from said autocorrelator into an address corresponding to its delay time; (e) means for detecting peaks of the signal stored in said memory means; (f) means for calculating the slope of a predetermined point of the origin of the autocorrelation function and the slope of corresponding predetermined points of the detected peaks; (g) means for comparing the slope of said origin and the slopes of the peaks to detect the address of the peak within a predetermined error; and (h) means for issuing an address signal of a true peak closest to the address of said origin among said addresses detected by said detecting means as a signal indicative of a heartbeat interval.
Claim 15
Dependent Claim
25 words
The invention in accordance with claim 10 wherein the slope is determined at a post-peak point with respect to said origin and said detected peaks.
Claim 16
Dependent Claim
30 words
The invention in accordance with claim 11 wherein said peak detecting means includes means for comparing a plurality of peak patterns stored in a memory with said autocorrelation function signal.
Claim 17
Dependent Claim
60 words
The invention in accordance with claim 12 wherein the screening means determines if the address of the true peak closest to the address of the origin is in the range of from approximately 50-210 beats per minute and thereafter subtracts the address of the previous peak and determines if the difference is in the range of ±15 beats per minute.
Claim 18
Dependent Claim
36 words
The invention in accordance with claim 11 wherein D/A converter means is provided for converting the peak address system issued from said issuing means into an analog signal and supplying said analog signal to a recorder.
Claim 19
Dependent Claim
38 words
The invention in accordance with claim 10 wherein said issuing means includes screening means for determining the address of the true peak closest to the address of the origin before the address of the true peak is issued.
References Cited (Backward Citations)
US3157781A
Cited
US3717756A
Cited
US3991365A
Cited
SU522507A1
Cited
US3982528A
Cited
US4037151A
Cited
US4346840A
Cited
US4403184A
Cited
US4239048A
Cited
US4494213A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-02-10 | 1989-08-12 | 1990-02-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-02-10 | 1993-08-12 | 1994-02-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-02-10 | 1997-08-12 | 1998-02-11 | $7700.00 | Window Closed / Lapsed |