Event related optical signal neuroimaging and analysis system for monitoring activity of a subject's brain

1 . A system for monitoring a subject's brain, the system comprising:

a first wavelength-swept light source configured to provide wavelength-swept emission of coherent light; and

a plurality of light detectors;

wherein the first wavelength-swept light source is arranged to both: (i) deliver the light towards the subject's brain tissue to be scattered to the detectors, and (ii) deliver the light to each of the detectors via one or more reference channels;

wherein each of the light detectors comprises:

a first input port arranged to receive scattered light from the subject's brain tissue;

a second input port coupled to one of the reference channels to receive reference light from the first light source;

a light combiner connected to both the first input port and the second input port for combining the scattered light received from the subject's brain tissue with the reference light received from the reference channel to provide a combined light signal comprising a component at a beat frequency for the scattered and reference light; and

signal processing circuitry configured to provide an indication of effects in the subject's brain tissue based on changes in a distribution of a plurality of components at different beat frequencies of the combined light signal.

2 . The system of claim 1 , wherein the system comprises a reference light splitter arranged to receive the reference light from the first light source to be delivered to each of the detectors.

3 . The system of claim 2 , wherein the reference light splitter is configured to split the reference light from the first light source between: (i) a first reference channel connected to the second input port of a first detector of the plurality of detectors, and (ii) a second reference channel connected to the second input port of a second detector of the plurality of detectors.

4 . The system of claim 1 , wherein first light source is configured to emit coherent light at each of a plurality of different wavelengths during one wavelength sweep; and

wherein, for each wavelength of light emitted by the first light source, each detector is configured to combine said reference light received from the light source with the scattered light from the subject's brain to provide a combined light signal, so that a plurality of different combined light signals are obtained during one wavelength sweep.

5 . The system of claim 4 , wherein the signal processing circuitry of each detector is configured to provide the indication based on the plurality of obtained combined light signals.

6 . The system of claim 5 , wherein the system is configured to provide the indication based on an indication of a value of the beat frequencies in the obtained combined light signals and/or an indication of a change in value of the beat frequencies.

7 . The system of claim 6 , wherein the system is configured to provide the indication based on timing data for each of the different wavelengths emitted by the first light source, and wherein the timing data comprises an indication of a sweep rate of the light source.

8 . The system of claim 1 , wherein the system comprises a second wavelength-swept light source configured to provide wavelength-swept emission of coherent light; and

wherein the second wavelength-swept light source is arranged to both: (i) deliver light towards the subject's brain tissue to be scattered to the detectors, and (ii) deliver reference light to each of the detectors via the one or more reference channels.

9 . The system of claim 8 , wherein for each of the light detectors, the light combiner is configured to combine the scattered light received from the subject's brain tissue with at least one of: (i) the reference light received from the first light source via the reference channel, and (ii) the reference light received from the second light source via the reference channel, to provide the combined light signal.

10 . The system of claim 8 , wherein the system is arranged so that reference light from the first light source travels less far to reach the detectors than reference light from the second light source.

11 . The system of claim 10 , wherein the system is arranged so that the difference in distance for reference light to travel to the detectors from the first and second light sources is selected so that beat frequencies generated by scattered light from the first light source and reference light from the first light source have no, or minimal, spectral overlap with beat frequencies generated by scattered light from the second light source and reference light from the second light source.

12 . The system of claim 8 , wherein the system is configured to control operation of the first and second light sources so that the two light sources do not emit light of the same wavelength at the same time and/or so that the first light source emits light that is incoherent with light from the second light source.

13 . The system of claim 8 , wherein the system is configured to control the light sources to operate sequentially so that the first light source emits light for a first time period while the second light source does not emit light, and then the second light source emits light for a second time period while the first light source does not emit light, and wherein at least one of the first and second time periods encompasses two or more wavelength sweeps.

14 . The system of claim 8 , wherein the system comprises a carrier channel combiner arranged to receive reference light from each of the first and second light sources; and

wherein the carrier channel combiner is configured to combine the reference light from both the first light source and the second light source onto a carrier channel.

15 . The system of claim 14 , wherein the system comprises a carrier channel separator connected to the carrier channel and to reference channels connected to each of the detectors; and

wherein the carrier channel separator is configured to separate light from the carrier channel into its constituent parts so that the reference light from the first light source is provided to each of the detectors via the reference channels and the reference light from the second light source is provided to each of the detectors via the reference channels.

16 . The system of claim 1 , wherein the first light source comprises an output light splitter configured to split the coherent light so that some of the light is delivered towards the subject's brain tissue and some of the light is delivered as reference light to each detector via the one or more reference channels.

17 . The system of claim 1 , wherein the first light source comprises a plurality of signal delivery channels arranged to receive the emitted light and to deliver said light towards the surface of the subject's head.

18 . The system of claim 17 , wherein the first light source comprises an optical switch configured to selectively apply light to each individual signal delivery channel in turn.

19 . The system of claim 18 , wherein the system is configured to control the optical switch to apply the light to a first of the signal delivery channels for a first time block, and to then apply the light to a second of the signal delivery channels for a second time block, and wherein the system is configured to control the optical switch so that at least one of the first time block and the second time block encompasses two or more wavelength sweeps.

20 . The system of claim 1 , wherein the system comprises a membrane arranged for attachment to the subject's head, and wherein each of the reference channels is coupled to the membrane, and wherein each of the reference channels is mechanically supported by the membrane.

21 . The system of claim 1 , wherein for each detector, the first input port, the second input port and the light combiner are provided on one integrated circuit.

22 . A method for monitoring a subject's brain, the method comprising:

using a first light source to provide wavelength-swept emission of light and to deliver said wavelength-swept light towards the subject's brain tissue; and

using a plurality of detectors to detect light scattered back from the subject's brain tissue at a plurality of different locations;

wherein the first light source is operated to deliver some of the wavelength-swept light it provides to each of the plurality of detectors as reference light via one or more reference channels;

wherein each of the detectors is operated to combine the reference light received from the first light source via the reference channel with the scattered light received from the subject's brain tissue to provide a combined light signal comprising a component at a beat frequency for the scattered and reference light; and

wherein the method comprises providing an indication of effects in the subject's brain tissue based on changes in a distribution of a plurality of components at different beat frequencies of the combined light signal.

23 . The method of claim 22 , wherein the method further comprises using a second wavelength-swept light source to deliver wavelength-swept light both: (i) towards the subject's brain tissue, and (ii) to each of the detectors as reference light via one or more of the reference channels; and

wherein each of the detectors is operated to combine the scattered light received from the subject's brain with at least one of: (i) the reference light received from the first light source via the one or more reference channels, and (ii) the reference light received from the second light source via the one or more reference channels, to provide the combined light signal.

24 . The method of claim 22 , wherein using the first light source to direct light towards the subject's brain tissue comprises sequentially providing the light to each of a plurality of different signal delivery channels which direct the light towards different regions of the subject's head.

25 . A tangible non-transitory computer readable storage medium storing computer program instructions configured to, when executed, cause a controller to perform a method for monitoring a subject's brain, the method comprising:

using a first light source to provide wavelength-swept emission of light and to deliver said wavelength-swept light towards the subject's brain tissue; and

using a plurality of detectors to detect light scattered back from the subject's brain tissue at a plurality of different locations;

wherein the first light source is operated to deliver some of the wavelength-swept light it provides to each of the plurality of detectors as reference light via one or more reference channels;

wherein each of the detectors is operated to combine the reference light received from the first light source via the reference channel with the scattered light received from the subject's brain tissue to provide a combined light signal comprising a component at a beat frequency for the scattered and reference light; and

wherein the method comprises providing an indication of effects in the subject's brain tissue based on changes in a distribution of a plurality of components at different beat frequencies of the combined light signal.