# US 11,026,608 B2 · Cerebral oximetry using time-gated direct sequence spread spectrum > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,026,608 B2 - Document ID: US11026608B2 - Status: Granted - Kind: B2 - Application number: 15/864,177 - Filed: 2018-01-08 - Published: 2018-07-12 - Granted: 2021-06-08 - Earliest claimed: 2017-01-09 - Assignees: Vox Biomedical LLC - Applicants: Kurt J. Linden; Laurence B. Milstein - Inventors: Kurt J. Linden; Laurence B. Milstein - Web page: https://patentgrep.com/patent/US11026608B2 ## CPC - A61B 5/14553: {specially adapted for cerebral tissue} - A61B 5/14552: {Details of sensors specially adapted therefor} - A61B 5/7203: {for noise prevention, reduction or removal} - A61B 5/7225: {Details of analogue processing, e.g. isolation amplifier, gain or sensitivity adjustment, filtering, baseline or drift compensation (input circuits for detecting, measuring, or recording bioelectric or biomagnetic signals A61B5/30; specific diagnostic methods using bioelectric or biomagnetic signals A61B5/316)} - A61B 5/7228: {Signal modulation applied to the input signal sent to patient or subject; Demodulation to recover the physiological signal} - A61B 5/7246: {using correlation, e.g. template matching or determination of similarity} - A61B 5/725: {using specific filters therefor, e.g. Kalman or adaptive filters (specific diagnostics methods using using bioelectric or biomagnetic signals A61B5/316)} - A61B 5/7257: {using Fourier transforms} - A61B 2562/0238: Optical sensor arrangements for performing transmission measurements on body tissue - A61B 2562/043: in a linear array - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) ## Abstract A cerebral oximeter includes a first light source for emitting light in response to a first electrical signal, a second light source for emitting light in response to a second electrical signal, a first photodetector for detecting at least a portion of the light emitted from the first light source, and a second photodetector for detecting at least a portion of the light emitted from the second light source. The cerebral oximeter further includes a pseudonoise (PN) code modulator for modulating the first electrical signal and the second electrical signal using a spreading sequence to occupy an electrical bandwidth greater than necessary to send optical signal pulse amplitude information to a photodetector, and a time gate for filtering a first detection signal from the first photodetector and a second detection signal from the second photodetector based on a desired time-of-arrival. ## Claims ### Claim 1 A cerebral oximeter comprising: a first light source configured to emit light within a first range of wavelengths in response to a first electrical signal; a second light source configured to emit light within a second range of wavelengths in response to a second electrical signal; a first photodetector configured to detect at least a portion of the light emitted from the first light source; a second photodetector configured to detect at least a portion of the light emitted from the second light source; a pseudonoise (PN) code modulator configured to modulate the first electrical signal and the second electrical signal using a spreading sequence to occupy an electrical bandwidth greater than necessary to send optical signal pulse amplitude information to a photodetector; a correlator or a matched filter operably coupled to an output of the first photodetector and an output of the second photodetector and configured to output detected light signal intensity as a function of light path time delay; and a time gate operably coupled to an output of the correlator or the matched filter and configured to filter a first detected signal intensity from the first photodetector and a second detected signal intensity from the second photodetector based on a desired time-of-arrival. ### Claim 2 (depends on 1) The cerebral oximeter of claim 1, wherein the first photodetector and the second photodetector have an electrical bandwidth sufficient to detect the pseudonoise (PN) code modulated spread spectrum light signals. ### Claim 3 (depends on 1) The cerebral oximeter of claim 1, wherein the first photodetector and the second photodetector are configured to receive light signals from the first light source and the second light source in addition to thermal noise and external interference. ### Claim 4 (depends on 1) The cerebral oximeter of claim 1, further comprising: detection circuitry with sufficient electrical bandwidth so that an autocorrelation function of the spreading sequence has a main lobe that is narrower than a time separation of a desired signal and at least one multipath signal. ### Claim 5 (depends on 1) The cerebral oximeter of claim 1, further comprising a processor configured to: measure characteristics of an optical channel traversed by the light emitted by the first light source or the light emitted by the second light source; and enhance an accuracy of a mathematical model used to model propagation of light from the first light source to the first photodetector. ### Claim 6 (depends on 1) The cerebral oximeter of claim 1, wherein the matched filter is a passive filter. ### Claim 7 (depends on 6) The cerebral oximeter of claim 6, wherein the passive filter is matched to the spreading sequence. ### Claim 8 (depends on 7) The cerebral oximeter of claim 7, wherein the only input to the passive filter is received from the first photodetector or the second photodetector. ### Claim 9 (depends on 7) The cerebral oximeter of claim 7, further comprising a processor configured to generate a time-of-arrival spectrum, which grows more precise with increasing number of detected laser pulses. ### Claim 10 A method of performing cerebral oximetry comprising: emitting light within a first range of wavelengths in response to a first electrical signal; emitting light within a second range of wavelengths in response to a second electrical signal; detecting at least a portion of the light emitted from a first light source; detecting at least a portion of the light emitted from a second light source; modulating the first electrical signal and the second electrical signal using a spreading sequence to occupy an electrical bandwidth greater than necessary to send optical signal pulse amplitude information to a photodetector; processing a first detection signal from a first photodetector and a second detection signal from a second photodetector with a correlator or a matched filter, wherein each of the processed first and second detection signals indicative of a function of light path time delay; and filtering the processed first and second detection signals with a time gate based on a desired time of arrival. ### Claim 11 (depends on 10) The method of claim 10, wherein the electrical bandwidth is sufficient to send a pseudonoise (PN) code modulated spread spectrum light signal. ### Claim 12 (depends on 10) The method of claim 10, wherein the first photodetector and the second photodetector are configured to receive light signals from the first light source and the second light source in addition to thermal noise and external interference. ### Claim 13 (depends on 10) The method of claim 10, further comprising determining an autocorrelation function of the spreading sequence including a main lobe that is narrower than a time separation of a desired signal and at least one multipath signal. ### Claim 14 (depends on 10) The method of claim 10, further comprising: measuring characteristics of an optical channel traversed by the light emitted from the first light source or the light emitted from the second light source; and enhancing an accuracy of a mathematical model used to model propagation of light from the first light source to the first photodetector based at least in part on the measured characteristics of the optical channel. ### Claim 15 (depends on 10) The method of claim 10, wherein processing the first detection signal and the second detection signal includes receiving an output from the matched filter, wherein the matched filter is a passive filter. ### Claim 16 (depends on 15) The method of claim 15, wherein the passive filter is matched to the spreading sequence. ### Claim 17 (depends on 16) The method of claim 16, wherein the only input to the passive filter is received from the first photodetector or the second photodetector. ### Claim 18 (depends on 10) The method of claim 10, further comprising generating a time-of-arrival spectrum based on detecting the light emitted from the first light source and the second light source. ### Claim 19 A cerebral oximeter comprising: first emitting means for emitting light within a first range of wavelengths in response to a first electrical signal; second emitting means for emitting light within a second range of wavelengths in response to a second electrical signal; a detecting means for detecting at least a portion of the light emitted from the first emitting means and for detecting at least a portion of the light emitted from the second emitting means; modulating means for modulating the first electrical signal and the second electrical signal using a spreading sequence to occupy an electrical bandwidth greater than necessary to send optical signal pulse amplitude information to the detecting means; a correlating means for determining a detection light signal intensity of a function of a light path time delay based on detected light from the detecting means; and filtering means configured to filter a first detection light signal intensity from the correlating means and a second detection light signal intensity from the correlating means based on a desired time-of-arrival. ### Claim 20 (depends on 19) The cerebral oximeter of claim 19 wherein the detecting means includes a first photodetector and a second photodetector.