WO2019090392A1

WO2019090392A1 - Device, method and system for optical imaging

Info

Publication number: WO2019090392A1
Application number: PCT/AU2018/051206
Authority: WO
Inventors: Shaokoon CHENG; Agisilaos KOURMATZIS; Taye MEKONNEN; Jason AMATOURY
Original assignee: Macquarie University; Neuroscience Research Australia; The University Of Sydney
Priority date: 2017-11-10
Filing date: 2018-11-09
Publication date: 2019-05-16

Abstract

A probe for optically imaging a pathway and associated methods is described. The probe includes a series of optical imaging units that include a beam splitter that rotates about an axis. The beam splitter directs a first portion of sensing light traversing a light path out from the probe in a radial direction onto a wall portion of the pathway and passes a second portion of the sensing light towards an adjacent optical imaging unit of the probe. Returned light from the wall portion of the pathway is received and directed back along the light path.

Description

Device, Method and System for Optical Imaging

Field

The present disclosure generally relates to a device, method and system for optical imaging. Particular embodiments relate to optical imaging of a pathway, for example, a biological lumen.

Background

Some existing techniques for imaging a pathway, for example, a biological lumen, powder hopper, fluized bed or pipe involve taking separate measurements along each point in the pathway at different times. In some situations, a pathway may have a complex geometry or the geometry dynamically changes making it difficult to image using some existing imaging techniques.

Various techniques are available to image a pathway, for example, a biological lumen, including X-rays, MRI, OCT and CT scans. The techniques have respective advantages and disadvantages. For example, certain implementations may be unsafe for repeated measurements, or may not provide sufficiently accurate details of the geometry of the pathway, or may require multiple measurements to be performed along the pathway, or may be time consuming, or may be costly. In certain cases, these multiple measurements may be difficult to perform or do not provide sufficiently accurate details of the transmission and deposition of particles along the pathway. Selecting the most appropriate technique or techniques to adopt for a given subject or application may present a trade-off between these relative advantages and disadvantages, or be limited by what options are available having regard to the resources available at the required time or location. There remains a need for useful choices of techniques for imaging biological lumen. Summary of the disclosure

According to one aspect of the disclosure, there is provided a probe for optically imaging a pathway, the probe including a plurality of optical imaging units arranged along a longitudinal dimension of the probe, the plurality of optical imaging units each including a light path through the optical imaging unit and including: a beam splitter; and a motor configured to rotate the beam splitter about a longitudinal axis of the optical imaging unit; the beam splitter configured to: direct a first portion of sensing light transmitted along the light path out from the probe in a radial direction onto a wall portion of the pathway and pass a second portion of the sensing light towards an adjacent optical imaging unit of the probe; and receive returned light from the wall portion of the pathway and direct the returned light along the light path.

According to another aspect of the disclosure, there is provided a probe for optically imaging a biological lumen, the probe including a plurality of optical imaging units arranged along a longitudinal dimension of the probe, the plurality optical imaging units each including a light path through the optical imaging unit and including: a beam splitter; and a motor configured to rotate the beam splitter about a longitudinal axis of the optical imaging unit; the beam splitter configured to: direct a first portion of sensing light transmitted along the light path out from the probe in a radial direction onto a wall portion of the biological lumen and pass a second portion of the sensing light towards an adjacent optical imaging unit of the probe; and receive returned light from the wall portion of the biological lumen and direct the returned light along the light path.

The motor may have a hollow passage and the light path may be provided within the hollow passage.

The motor may include an optically transparent material and the light path may be provided through the optically transparent material.

The motor may include a stator connected to a rotor that rotates on an optically transparent central shaft.

The motor may include a divergence element that is configured to expand the diameter of the sensing light transmitted along the light path. Each optical imaging unit may further include a focusing element to collimate the light transmitted along the light path towards the beam splitter.

Each optical imaging unit may further include a beam focusing element configured to receive the second portion of sensing light from the beam splitter and direct this sensing light towards the adjacent optical imaging unit. Each optical imaging unit may also be housed in an interior housing formed of rigid and transparent material.

The beam focusing element may direct the second portion of sensing light along a fibre optic cable connecting the interior housings of adjacent optical imaging units. The beam focusing element may be rigidly mounted within the interior housing.

The beam focusing element may be rigidly mounted relative to one or more of: the fibre optic cable, the focusing element, and the beam splitter.

The probe may further include one or more pressure sensors.

The one or more pressure sensors may be Fibre Bragg gratings configured to optically image pressure variations of the biological lumen.

The beam splitters of the plurality of optical imaging units of the probe may rotate simultaneously to each other.

The beam splitters of the plurality of optical imaging units of the probe may rotate separately from one another. The beam splitters of the plurality of optical imaging units of the probe may rotate at a same speed.

The beam splitters of the plurality of optical imaging units of the probe may rotate at different speeds.

According to another aspect of the disclosure, there is provided a system for optically imaging a biological lumen including: a light pipe having a proximal end and a distal end; a light source and a photo detector connected to the proximal end of the light pipe; and a probe, as described above, connected to the distal end of the light pipe, configured to receive the sensing light from the light source and direct the returned light to the photo detector via the light pipe. According to another aspect of the disclosure, there is provided a method including: providing, over a light path, sensing light to a probe inserted within a biological lumen, the probe comprising a plurality of beam splitters along a longitudinal dimension of the probe; at a first beam splitter of the probe, directing a first portion of the sensing light in a radial direction from the probe onto a first wall portion of the biological lumen and passing a second portion of the sensing light onto a second beam splitter of the probe; at the second beam splitter of the probe, directing the second portion of the sensing light in a radial direction from the probe onto a second wall portion of the biological lumen, different from the first wall portion; while the first and second portions of the sensing light are directed onto the first and second wall portions of the biological lumen respectively, rotating the radial directions about respective longitudinal axes; while rotating the radial directions, directing light returned responsive to the first and second portions of the sensing light to a detector for forming an image of the biological lumen.

The method may also include rotating the first and second beam splitters and directing the returned light over one or more deformation cycles of the biological lumen.

The method may also include rotating the first and second beam splitters through at least several full revolutions during each of the one or more deformation cycles.

The method may further include: at the first beam splitter of the probe, passing a third portion of the sensing light onto the second beam splitter of the probe; at the second beam splitter of the probe, passing the third portion of the sensing light onto a further optical element of the probe. The method may further include: at the further optical element of the probe, directing the third portion of the sensing light in a radial direction onto a third wall portion of the biological lumen, different from the first wall portion and the second wall portion; while the third portion of the sensing light is radially directed onto the third wall portion, rotating the radial direction about a longitudinal axis. The method may further include: at the further optical element of the probe, passing the third portion of the sensing light pass a Fibre Bragg grating that affects the third portion of the sensing light dependent on an applied pressure at the Fibre Bragg grating; returning light passing the Fibre Bragg grating to a detector, for forming an image pressure within the biological lumen. According to another aspect of the disclosure, there is provided a method including: providing, over a light path, sensing light to a probe inserted within a pathway; at a first optical element within the probe: generating a first measurement signal indicative of the shape of the first wall portion of the pathway by directing a first portion of the sensing light in a radial direction from the probe onto the first wall portion and receiving light reflected back from the first wall portion; and passing a second portion of the sensing light along the probe to a second optical element within the probe, at the second optical element within the probe, generating a second measurement signal, wherein the second measurement signal is indicative of: the shape of a second wall portion, different from the first wall portion; or a pressure within the pathway at the second optical element.

According to another aspect of the disclosure, there is provided a probe for insertion into a lumen, the probe including a first optical imaging unit, the first optical imaging unit including: a light path traversing a longitudinal axis of the optical imaging unit; a beam splitter located along the light path; and a motor configured to rotate the beam splitter about the longitudinal axis of the optical imaging unit; wherein the beam splitter is configured to: direct a first portion of sensing light transmitted to the beam splitter along a light path out from the probe in a radial direction and pass a second portion of the sensing light towards a second optical imaging unit of the probe; and receive light returned to the probe from said radial direction and direct the returned light along the light path.

According to another aspect of the disclosure, there is provided a method including providing sensing light to a probe inserted within a pathway carrying a fluid including suspended particles. At a first optical element within probe the method includes generating a first measurement signal indicative of a time that a particle travels past the first optical element by directing a first portion of the sensing light in a radial direction outwards from the probe and receiving light reflected back from the particle and passing a second portion of the sensing light along the probe to a second optical element located at a predetermined distance from the first optical element. At the second optical element within the probe, the method includes generating a second measurement signal indicative of a further time that the particle travels past the second optical element by directing a second portion of the sensing light in a radial direction outwards from the probe and receiving light reflected back from the particle. A speed of the particle is determined based on the first and second measurement signals and the predetermined distance.

According to another aspect of the disclosure, there is provided a method including providing sensing light to a probe inserted within a pathway carrying a fluid including suspended particle and generating, at an optical element within the probe, a first measurement signal at a first time, the first measurement signal indicative of a first optical path length by directing a first portion of the sensing light in a radial direction outwards from the probe and receiving light reflected back from a particle deposition layer on the pathway. A thickness of the particle deposition layer at the first time is determined from the first measurement signal.

The method may be repeated, for example to determine a rate of deposition over time.

It will be appreciated that embodiments of the disclosed probe may be used in the disclosed methods.

Further aspects of the present invention and further embodiments of the aspects described in the preceding paragraphs will become apparent from the following description, given by way of example and with reference to the accompanying drawings.

Brief description of the drawings Figure 1 is a diagram of a first system for optically imaging a sample;

Figure 2a is a diagram of an optical imaging device for use in the system of Figure 1 in accordance with one embodiment;

Figure 2b is a partial diagram of an optical imaging device for use in the system of Figure 1 in accordance with another embodiment; Figure 3 is a diagram of an example of a distribution of sensing light projected from an optical imaging device, for example the device of Figure 2a;

Figure 4 is a diagram of a beam focusing unit for an optical imaging device, for example the device of Figure 2a; Figure 5a is a diagram of a motor of an optical imaging device, for example the optical imaging device of Figure 2a;

Figure 5b is a diagram of another motor of an optical imaging device, for example the optical imaging device of Figure 2a; Figure 6 is a diagram of control circuitry for an optical imaging system, for example the optical imaging system of Figure 1 ;

Figure 7a is a diagram of a second system for optically imaging a sample;

Figure 7b is a diagram of a circulator shown in Figure 7a; and

Figure 8 is a diagram of a particle source for use in the second system of Figures 7a-7b.

Detailed description of the embodiments

According to some embodiments of the present disclosure, an in-situ technique provides real-time information on the geometry occurring at multiple locations along a pathway. In some embodiments of the present disclosure, an in-situ technique provides real-time information on the characteristics of particles travelling in a fluid along a pathway. In one example, these characteristics include the transmission or deposition of the particles travelling in the fluid along the pathway. In some examples, the pathway may be a powder hopper, a fluidised bed, a pipe, or a biological lumen. The information may be obtained over a period of time, to indicate changes in geometry or changes to the transmission or deposition of particles over the time period. In one example, the time period may be a deformation cycle. For example the geometry information may be of the upper respiratory tract during one or more breathing cycles. Certain embodiments provide real-time information on the pressure that is associated with this deformation, again over a period of time, for example during over a deformation cycle. In another example, the time period may be the time it takes for a particle to travel between specific locations along the pathway.

Certain embodiments utilise optical imaging of the sample. In particular, techniques that use optical coherence tomography (OCT) are disclosed. The OCT may be performed in either the time-domain or the frequency domain. An example lumen to which a probe of the present disclosure may be applied for optical imaging is the upper airway of an animal, for example a human. The probe may have application to a method for creating an image of, or related to, the geometry of the upper airway. The geometry of the upper airway is affected by several muscles, including the tongue. In one application, the probe may be used to characterise tongue movement over a period of time.

In some embodiments the disclosed probe provides geometry information around substantially the entirety of an internal periphery of the lumen. In some embodiments the disclosed probe simultaneously provides geometry information at two, three, four, or more locations along the biological lumen. Each location may be associated with a channel of the OCT. Each channel may be specified by wavelength. Measurement may cycle through the wavelengths through wavelength division multiplexing. In some embodiments the simultaneous geometry information at locations along the biological lumen includes geometry information around substantially the entirety of the internal periphery of the lumen. In some embodiments pressure information is simultaneously provided by the probe with the geometry information and/or particle information.

First system overview

An embodiment of a first system 100 for performing multi-channel OCT of a pathway, for example, a biological lumen 102 is shown in Figure 1 . The biological lumen 102 may be, for example, the pulmonary tract, gastrointestinal tract or an artery of a subject.

The exemplary system 100 shown in Figure 1 includes a light source 104 for emitting light of multiple wavelengths or across a range of wavelengths over a light conduit 106, for example an optical fibre. The light source 104 emits light within wavelength ranges that are suitable for OCT such as 800 nm -1300 nm. The light conduit 106 is in optical communication with a beam splitter 108, which splits the received light into sensing light and reference light. The reference light is directed to a reference path 1 10 to provide reference arm 1 12, while the sensing light travels along a sensing path 1 14 for forwarding to a probe for insertion into a biological lumen, the probe providing an optical imaging device 1 18. In embodiments in which the multichannel OCT is implemented by wavelength division multiplexing, a MUX-DEMUX unit 1 1 6 is provided, for example between the beam splitter 1 08 and the optical imaging device 1 1 8.

In general, an embodiment of an optical imaging device 1 1 8 includes a plurality of optical imaging units distributed along a length of the optical imaging device 1 1 8. Figure 1 shows a probe with three optical imaging units 1 22a, 1 22b and 1 22c. Each of these optical imaging units 1 22a, 1 22b, 1 22c project a portion of the sensing light from the optical imaging device 1 1 8, as indicated by reference numerals 1 21 a, 1 21 b and 1 21 c, respectively. Each wavelength range of light has a bandwidth of Δλι- Δλ_η that corresponds to a centre wavelength A λ_η. Each optical imaging will direct a wavelength portion of the sensing light towards the biological lumen and pass remaining wavelengths towards an adjacent optical imaging unit.

In one embodiment the optical imaging unit 122a projects light at λι and passes light at A₂ to λ_η, the optical imaging unit 122b projects light at A₂ and passes light at A₃ to λ_η and the optical imaging unit 1 22c projects light at A_n. The projected light is generally transverse to the length of the optical imaging device 1 1 8. Accordingly, each of these optical imaging units 122a, 122b, 122c also receives reflected light from the biological lumen and returns the reflected light to the beam splitter 108, via the MUX-DEMUX unit 1 1 6.

In the embodiment shown in Figure 1 , the MUX-DEMUX unit 1 1 6 is located between the beam splitter 1 08 and the optical imaging device 1 1 8 to perform wavelength de-multiplexing and multiplexing. The de-multiplexing function of the MUX- DEMUX unit 1 1 6 performs wavelength de-multiplexing of the received sensing light by directing the light to a selected one of the channels 1 30. In particular, the wavelength de-multiplexing creates n channels, corresponding to the n optical imaging units, with a centre frequency of a channel corresponding to one of Ai to A_n. The channels 1 30 have different optical path delays, which compensate for the different optical path lengths 1 23a, 123b, 123c to each optical imaging unit 1 22a, 122b, 122c respectively. In Figure 1 the extent of the optical delay is represented graphically by delay elements 1 32, which are selected to equalise the path length for each channel. The multiplexing function of the MUX-DEMUX unit 1 16 directs light of the selected channel 1 30 to the optical imaging device 1 1 8. The MUX-DEMUX unit 1 16 further receives the reflected light from the optical imaging units 122a, 122b, 122c and returns it over the same channel 130 to the beam splitter 108. The reflected light returned from the multiplexer 1 16 and reflected light returned from the reference mirror 1 12 is received and interfered by the beam splitter 108, with the interfered light being detected by detector 124, for example an array of photo-detectors or a spectrometer with an associated data acquisition device (DAQ) 126 and data processor 128 that constructs multi-dimensional images of the sample 102. The data processor 128 either controls or is synchronised with a controller 600 that may be part of the processor 128 or implemented separately from the processor 128. In one embodiment, the controller 600 controls the MUX-DEMUX unit 1 16, to enable identification of which optical imaging unit 122a, 122b, 122c is in operation.

It will be appreciated that in OCT optical delays to ensure the required interference pattern is formed may be introduced at other locations and/or by other means. For example the optical delays may be introduced in the optical path from the beam splitter 108 to the reference arm 1 12. In another example an optical component of the reference arm, for example a mirror, may be physically moved to create different path lengths.

Optical imaging device

An embodiment of an optical imaging device 1 18 is shown in further detail in Figure 2A. The optical imaging device 1 18 includes a plurality of optical imaging units, with two optical imaging units 122a and 122b shown in detail in the Figure. The optical imaging units are located within an exterior housing 202. The exterior housing 202 of the optical imaging device 1 18 may be any suitable housing that minimises or prevents the optical imaging units 122a, 122b coming in contact with the biological lumen or biological fluid associated with the biological lumen. The exterior housing 202 is formed from any suitable material that facilitates the transmission of light from the optical imaging units 122a, 122b and which is flexible enough to be inserted in a biological lumen. In one example, the exterior housing 202 is a transparent and flexible catheter.

Each optical imaging unit 122a, 122b is located within the exterior housing 202 of the optical imaging device 1 18. Adjacent units are connected together by an optical fibre 204. Each optical imaging unit 122a, 122b includes an interior housing 206 for housing a motor 208, a scanning unit 212 and a beam focusing unit 214, for example an objective lens. The interior housing 206 of each optical imaging unit 122a, 122b includes a portion that extends over the scanning unit 212 and at least in that portion is formed from any suitable material that facilitates the transmission of light from the optical imaging units 122a, 122b, towards the biological lumen 102. The interior housings 206 may also be formed of rigid material, such as a rigid polymer material. The rigidity provides a fixed spatial relationship between the optical components, allowing for example light passed by the scanning units 212 to be focussed onto an inlet aperture of the optical fibre 204.

With reference to the optical imaging device 122a shown in Figure 2a, the motor 208 includes a stator 216 and a rotor 218. The stator 216 of the motor 208 is connected to an electrical power supply 134 (see Fig 1 ) via electrical cable 220. In one embodiment the electrical cable is located between the exterior housing 202 and the interior housing 206. The motor 208 is configured to transmit light from the light source 104 to the scanning unit 212. In one embodiment, the motor 212 transmits light by being formed of transparent material as described in more detail in relation to Figure 5b. In the embodiment shown in Figure 2a, the motor 208 includes a hollow passage 222 for receiving a fibre-optic cable 224 through a first opening 226 in the interior housing 206. As shown in Figure 2a, light emitted from the light source 104 travels along the fibre- optic cable 224 located in the hollow passage 222 of the motor 216 towards the scanning unit 212. The fibre-optic cable 224 is fixed in place within the hollow passage 222, so as to not impact the rotor 218. The fibre-optic cable 224 may be a single mode fibre. Light from the light source 104 exits the fibre-optic cable 224 at a location spaced apart from the scanning unit 202. A divergence member 228 and a focussing element 230 function to expand the diameter of the light beam and collimate the beam, for passing to the scanning unit 212. The properties of the divergence member 228 and focusing element 230 and the working distance of each imaging unit may be used to control the spot size (e.g. cross-sectional diameter) of the sensing light beam directed to the biological lumen and the lateral resolution. As shown in Figure 2b, the working distance is the sum of the distances between the focusing element 230 and the wavelength dependent beam splitter 232 as indicated by x and the distance between the wavelength dependent beam splitter 232 and the biological lumen as indicated by y. The distances x and y are controlled by varying the widths of the divergence member 228 and the focal distance of the focusing element 230. In one example, the divergence member 228 is a glass spacer and the focussing element 230 is a Graded Index (GRIN) lens. In some embodiments the fibre-optic cable 224 and the focusing element 230 to have a similar refractive index in order to minimise back-reflections or back-scattering at the interface located between the fibre-optic cable 224 and focusing element 230. In one example, a similar refractive index is obtained by the divergence member 228 being a hollow rod without a core or cladding and the fibre- optic cable being a solid core. In one embodiment the divergence member 228 and focussing element 230 are mounted to the rotor 218. In the embodiment shown in Figure 2b, the focussing element 230 collimates the beam and transmits this over the free-air space 240 located between the focussing element 230 and wavelength dependent beam splitter 232.

The scanning unit 212 is mounted to the rotor 218, whereby rotation of the rotor 218 causes the scanning unit 212 to rotate. In this way circumferential scanning of the surrounding biological lumen is achieved. Simultaneous rotation of the scanning units 202, either synchronously or asynchronously, allows for simultaneous measurement at multiple locations along the biological lumen.

The scanning unit 212 includes a wavelength dependent beam splitter 232. The wavelength dependent beam splitter 232 receives sensing light transmitted from the light source 104. The wavelength dependent beam splitter 232 reflects light of certain wavelengths and projects that light out of the scanning unit 212 in a radial direction as indicated by reference numeral 121 a in Figures 1 and 2a. The wavelength dependent beam splitter 232 receives reflected light (e.g. back-scattered or back-reflected light) from the biological lumen, where this reflected light includes at least one optical property that has been influenced by the biological lumen. In the embodiment shown in Figure 2A, the wavelength dependent beam splitter 232 is angled at a 45 degree angle to a longitudinal axis of the optical imaging unit 122a to reflect an approximately perpendicular sensing light beam 121 a towards the sample. The wavelength dependent beam splitter 232 may be dichroic filter or prism.

The wavelength dependent beam splitter 232 transmits other wavelengths of light, for example, as indicated by reference numerals 122b and 122c of Figure 1 towards a beam focusing unit 214. The beam focusing unit 214 is rigidly mounted relative to the exit aperture of the fibre-optic cable 224, the focussing element 230 and the wavelength dependent beam splitter 232. In one embodiment the beam focusing unit 214 is mounted within the interior housing 206, which provides the required rigidity. Another optical fibre 204 is rigidly mounted relative to the focussing element 230. The focussing element 230 is configured to focus light passed by the wavelength dependent beam splitter 232 into the optical fibre 204. For example, the beam focusing unit 214 focuses the light onto a second opening 236 of the interior housing 206, which opening serves as an entrance aperture for the optical fibre 204.

The second optical imaging unit 122b includes a similar structure to the first optical imaging unit 122a described previously, except that the second optical imaging unit 122b will transmit a different wavelength of light 121 b towards the sample than what was projected by the first optical imaging unit 122a. In embodiments where the second optical imaging unit 122b is the final unit of the probe, it need not pass light to another optical imaging unit. Accordingly, the beam splitter 232b may be replaced with a mirror. The wavelength dependent beam splitters 232a, 232b of each optical imaging unit 122a, 122b act as a cascading filter, as shown by example in Figure 3. In this embodiment, the wavelength dependent beam splitter 232a of the first optical imaging unit 122a receives a full-wavelength range of the sensing light and projects a specific subset wavelength of light 121 a towards the biological lumen 102. The remaining wavelengths of light 121 b, 121 c...121 n that were not projected towards the biological lumen 102 by the first optical imaging unit 122a are transmitted to the second optical imaging unit 122b. The second optical imaging unit 122b projects a different subset wavelength of light, for example, as indicated by reference numeral 121 b in Figure 3, than what was projected by the first optical imaging unit 122b. The second optical imaging unit 122b will further transmit the remaining wavelengths of light, for example, 121 c ..121 n to a third optical imaging device 122c. Although the sub-spectrums of light indicated by the individual centre wavelengths of λ-ι-λ_η appear separate in Figure 3, it will be appreciated that there may be overlap at the boundaries between adjacent individual sub-spectrums.

Reflected light (e.g. back-scattered or back-reflected light) returning from the biological lumen may contain light components that have a different wavelength from the sensing light projected towards the biological lumen if the lumen tissue or the fluid located inside the lumen causes inelastic scattering or has fluorescence properties. These different wavelengths may cause noise in the resulting reconstructed images.

Inelastic scattering caused by the lumen tissue or fluids located inside the lumen will decrease with increasing wavelengths and should be minimal at the light source wavelengths of 840 nm and 1300 nm suitable for OCT.

In addition, tissue fluorescence may also create back-scattered or back-reflected light that has a longer wavelength and lower intensity than the sensing light directed towards the biological lumen. The back-reflected or back-scattered light caused as a result of inelastic scattering and tissue florescence will generally have low intensities that, in some embodiments is removed through signal conditioning and pre-processing during image reconstruction, to provide an improved signal-to-noise ratio.

In some embodiments the scanning unit 212 of each of the optical imaging units 122a, 122b, 122c rotates, either simultaneously or separately to one another. Each scanning unit may rotate at the same or at a variable rotation speed as to the remaining scanning units. For example, a scanning unit may rotate at a speed of about 10,000 revolutions per minute. A typical breathing cycle will last 1 -2 seconds and each scanning unit my rotate approximately 167-334 times during that cycle. By using at least two optical imaging units, for example, 121 a, 121 b in the optical imaging device 1 18, simultaneous scanning of different areas along the length of a sample may be performed. For example, two or more optical imaging devices 122a, 122b distributed longitudinally along the length of optical imaging device 1 18 may permit simultaneous scanning of multiple locations of a person's upper respiratory tract in a single breathing cycle. The resulting images may be used to provide real-time, in-situ and in vivo determinations of the geometry of the person's lumen during a deformation cycle, in this instance the upper respiratory tract during a single breathing cycle. These images may also assist in identifying collapse of a person's upper respiratory tract during a breathing cycle. In one embodiment, the optical imaging device 1 18 may detect a marker, such as a biomarker or fluorescent dye, which has been absorbed or is travelling through the biological lumen 102. In one example, detection of biomarkers or fluorescent dye may be used to calculate the rate of fluid flow through the biological lumen 102 by calculating the amount of time that a maker takes to be detected by the first and last optical imaging units.

In another embodiment, the optical imaging device 1 18 may include one or more pressure sensors for detecting pressure variations associated with the biological lumen 102. In one example, these pressure sensors may measure the pressure variations associated with deformation or collapse of a person's respiratory tract during breathing. For example, a Fiber Bragg grating may be provided along the optical imaging device 1 18, configured to provide optical imaging of pressure variations. In particular, as the Fiber Bragg grating is subject to the pressure of a biological lumen, its shape deforms, which in turn affects the light transmission characteristics of the grating. In some embodiments the optical imaging device 1 18 includes a plurality of scanning units as described above and one or more Fiber Bragg gratings. In this way a single optical imaging device 1 18 can measure changes in shape of a biological lumen and changes in pressure within the biological lumen.

It will be appreciated that the optical imaging device may be of any suitable size for imaging a sample. For example, an optical imaging device may have a diameter of 1 .5mm to 2.5 mm in order to image an upper respiratory tract of a person. In another example, the optical imaging device may be made from silicon wafer or silicon oxide materials.

Beam focusing unit

An embodiment of a beam focusing unit 214 of each optical imaging unit 122a, 122b is shown in Figure 4. The beam focusing unit 214 includes a lens 410 and a free- air space 420 located between the lens 410 and a fibre-optic cable 204 connected to an adjacent optical imaging unit. In another embodiment, the space may include an optically transparent glass spacer. In one embodiment, the lens 410 collects the wavelengths of sensing light that were transmitted by a first optical imaging unit and transmits these towards the fibre-optic cable 204 connected to a subsequent optical imaging unit. The lens 410 is positioned from the fibre-optic cable 204 at a distance d that corresponds to the focal plane F of the lens 410.

Motor

In one embodiment, the motor 208 for actuating the scanning unit 212 is a hollow piezoelectric motor 500, for example as shown in Figure 5a. The motor 500 includes a stator 502 formed of a hollow cylinder of piezoelectric material that is attached to an actuator 504. In one example, the actuator is formed from aluminium or steel material.

When each column 502a, 502b of the stator 502 is energized by voltages of different phases, they expand and contract thereby actuating the actuator columns 504a, 504b of the actuator 504 in a backward and forward tangential oscillation. This tangential oscillation transmits a frictional torque to rotate rotor 506.

In another embodiment, the motor 208 for actuating the scanning units 212 may be an optically transparent motor 520 as shown in Figure 5b. The optically transparent motor 520 may be an electrostatic motor that includes a stator 522 connected to one or more rotor blades 524 that rotate on a central shaft 526. An electrical voltage applied on the stator 522 causes the rotor 524 to rotate on the central shaft 526. The rotor 524 causes rotation of a scanning unit 212 mounted to the central shaft 526. In order for the motor 520 to be optically transparent, the stator 522, rotor 524 and central shaft 526 may be formed from optically transparent materials, for example, optically transparent glass. In another embodiment, the central shaft 526 may be formed from optically transparent material, while the stator and rotor are formed of optically opaque materials to minimise back-scattered or back-reflected light. In another embodiment, the motor 520 may be formed from an optically transparent silicon substrate by successive masking and etching processes associated with a microelectromechanical based manufacturing process. In one embodiment, a divergence member 228 to expand the diameter of the light beam transmitted through the motor may be located within or outside of the motor, for example, the divergence member may be mounted on the optically transparent central shaft 526 of the motor.

In another embodiment, the optically transparent motor 520 may be integrated onto a silicon substrate by stacking the stator 522, rotor 524 and central shaft 526 onto a silicon substrate. In yet another embodiment, the optically transparent motor 520, scanning unit 212 and beam focusing unit 214 may be integrated onto a silicon substrate.

In comparison to a conventional magnetic motor, the motors shown in Figures 5a and 5b may reduce interference of the light that travels through the motor and towards the scanning unit 212. Furthermore, unlike a conventional magnetic motor, the motors shown in Figures 5a and 5b may permit the optical imaging unit to be formed as a single unit.

Controller

Figure 6 shows a control arrangement for an optical imaging device, for example the optical imaging device 1 18. A controller 600, which may be part of the processor 128 or implemented separately from the processor 128, includes a programmable microcontroller 602 and an amplifier 604. Each motor associated with each optical imaging unit of the optical imaging device 1 18 may be connected in series or parallel to the controller 600. In the embodiment shown in Figure 6, the controller 600 is connected in parallel to each motor 208a, 208b of the optical imaging units 121 a, 121 b via electrical cable 220. In one embodiment, the controller 600 delivers electrical signals simultaneously or singularly to each of the motors 208a, 208b in order to commence their operation.

The electrical cable 220 may be formed of transparent or opaque material. When the electrical cable is formed of opaque material, sensing light projected during each revolution of a scanning unit 212 will interfere with electrical cable 220. In addition, light reflected from the sample and received by each scanning unit 212 will also interference with electrical cable 220. The interference of the sensing and reflected light with the electrical cable 220 will cause interference lines to be formed on the reconstructed images formed by processor 128. In one embodiment, these interference lines are used as reference lines during image reconstruction. In one example, these interference lines indicate a starting and finishing location of a circumferential scan of the sample 102 during one revolution of a scanning unit of an optical imaging unit. In another example, these interference lines may also indicate the position where deformation of the sample 102 began and ended.

Second system overview An embodiment of a second system 700 for performing multi-channel OCT of a pathway is shown in Figure 7a. The pathway may be a channel or conduit having one or more walls and may transmit a solid and/or fluid substance. One example of such a pathway 702 is shown in Figure 7a. .

The exemplary system 700 shown in Figure 7a includes a light source 704 for emitting broadband light or light across a range of wavelengths over a light conduit 706, for example an optical fibre. The light source 704 emits light within wavelength ranges that are suitable for OCT. In one example, light may be emitted within a wavelength range of 800 nm -1300 nm. In another example, light may be emitted within a wavelength range of 800 nm -1500 nm. The light conduit 706 is in optical communication with a coupler 708, which divides the received light into sensing light and reference light. In one example, the coupler 708 is a beam splitter. The reference light is directed to a reference path 710, while the sensing light travels along a sensing path 714 for forwarding to a probe for insertion into the pathway, the probe providing an optical imaging device 718. In some embodiments, a circulator 712 is provided along light conduit 706. The circulator 712 may isolate the reflected light 740 returned from the reference path 710 and the sensing path 712 from the light emitted by the light source 704. During operation, the reflected light 740 may influence the output power and spectral characteristics of the light source 704. As shown in Figure 7b, the circulator may direct light from the light source 704 towards port-1 , while the reflected light 740 returning through port-2 gets redirected to port-3. Optical imaging device 718 has a similar structure to and operates in a similar manner as the optical imaging device 1 18, described with reference to Figures 1 -6.

In some embodiments, a fluid 728 is delivered to the pathway 702 while the optical imaging device 718 is located therein. Particles 730, such as powder particles, are suspended in the fluid. In some embodiments the particles 730 have been delivered to the pathway by a delivery device 800 (see Figure 8). The delivery device 800 may be any suitable device to deliver particles to the pathway, such as an inhaler, nebuliser or the like.

As the particles travel past each optical imaging unit 722a, 722b, 722c they influence the sensing light 721 a, 721 b, 721 c emitted from each respective optical imaging unit. The reflected light (e.g. back-scattered or back-reflected light) from these particles includes at least one optical property that has been influenced by the particles. In one embodiment, the reflected light received from two consecutive imaging units positioned at predetermined locations along the probe may be used to determine the speed of the particles as they travel between these imaging units. For example, the difference in the timing of reflections ti, t_∑ recorded by optical imaging units 722a and 722b and the predetermined distance / may be used to calculate the speed of a particle as it travels between units 722a and 722b.

The optical imaging unit also receives reflected light from the walls of the pathway or from deposition of the particles on the one or more walls of the pathway. In one embodiment, the thickness of the deposition of particles on the wall 703 of the pathway 702 is measured by an optical imaging unit, for example, optical imaging units 722a, 722b or 722c, located at a predetermined distance along the probe length. In one example, as the particles deposit on the wall 703, the optical path length of this optical imaging unit will be influenced. In one example, as the particles deposit on the wall 703, the optical path length decreases by twice the thickness of the accumulated particles. In another example, as the particles deposit on the wall 703, the higher refractive index of the accumulated particles will influence the optical path length of the optical imaging unit. In one embodiment, the difference in the measured optical path length and a predetermined optical path length at an optical imaging unit may be used to calculate a thickness of the deposited particles. In another embodiment, changes in the thickness of the deposited particles at various times may be used to calculate a rate of deposition of the particles. For example, at any of the optical imaging units 722a, 722b or 722c, a first thickness di of the deposition layer at time fy and a second thickness d_∑ of the deposition layer at time t₂ may be used to calculate a rate of deposition of the particles on the wall 703.

The distribution of the light from the light source across the optical imaging units of the optical imaging devices, including the optical imaging device 1 18 and the optical imaging device 718 may be selected based on the required application. For example, different configurations may be selected depending on whether or not the optical imaging device is required to sense particles, either on the wall 703 of the pathway 702 or in a fluid traversing the pathway 702. In some embodiments each optical imaging unit emits a portion of the light from the light source at a per channel bandwidth of for example about 10 nm, about 20 nm, about 30 nm, about 40 nm , about 50 nm, about 60 nm, about 70 nm, about 80 nm, about 90 nm or about 100 nm. In applications for sensing particles or particle deposition, the bandwidth may be selected to be about 30 nm or greater, or 40 nm or greater or 50 nm or greater, thereby providing a higher axial resolution measurement. For example, the axial resolution may about 5-10 pm, about 10-15 pm, about 15-20 pm or about 20-25 pm, based on the bandwidth and wavelength selected. An optical delay line scanner 716 is provided along reference path 710. The optical delay line scanner 716 performs one or more scanning oscillations (e.g. back- and-forth motion) of the channels within a predetermined time period. In one embodiment, the predetermined time period corresponds to a time that a particle travels the distance between two consecutive imaging units, for example corresponding to a fastest expected particle speed. In one embodiment, a collimator 724 receives the delayed light of each channel from the optical delay line scanner 716 and focuses this light towards a reference mirror 726. In one embodiment, reflected light returned along sensing path 714 and reference path 710 is received and interfered by the coupler 708 and detected by one or more detector units 730 that are associated with a data acquisition device (DAQ) 732 and data processor 734 that constructs multi-dimensional images of the pathway 702. The data processor 734 constructs images of the interference of the sensing and reflected light. In one example, the data processor 734 performs cross-correlation of the interference of the sensing light and reflected light in order to determine the speed of a particle as it travels between two consecutive imaging units. In another example, the data processor 734 performs calculations to determine the thickness of a layer of deposited particles or the rate of deposition of these particles at an imaging unit. In another embodiment, the coupler 708 transmits the reflected and interfered light to the circulator 712 for detection by the one or more detector units 730, as shown in Figure 7b.

It will be appreciated that in OCT optical delays to ensure the required interference pattern is formed may be introduced at other locations and/or by other means. For example the optical delay line scanner 716 may be provided along the sensing path 714. In another example an optical component of the reference arm, for example the reference mirror 726, may be physically moved to create different path lengths.

It will be understood that the invention disclosed and defined in this specification extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention.

Claims

1 . A probe for optically imaging a pathway, the probe including a plurality of optical imaging units arranged along a longitudinal dimension of the probe, the plurality of optical imaging units each including a light path through the optical imaging unit and including:

a beam splitter; and

a motor configured to rotate the beam splitter about a longitudinal axis of the optical imaging unit;

the beam splitter configured to:

direct a first portion of sensing light transmitted along the light path out from the probe in a radial direction onto a wall portion of the pathway and pass a second portion of the sensing light towards an adjacent optical imaging unit of the probe; and

receive returned light from the wall portion of the pathway and direct the returned light along the light path.

2. The probe of claim 1 , wherein the motor has a hollow passage and the light path is provided within the hollow passage.

3. The probe of claim 1 , wherein the motor includes optically transparent material and the light path is provided through the optically transparent material.

4. The probe of claim 3, wherein the motor includes a stator and a coupled rotor including an optically transparent shaft.

5. The probe of any one of claims 1 -4, wherein the motor includes a divergence element that is configured to expand the diameter of the sensing light transmitted along the light path.

6. The probe of any one of claims 1 -5, wherein each optical imaging unit further includes a focusing element to collimate the light transmitted along the light path towards the beam splitter.

7. The probe of any one of claims 1 -6, wherein each optical imaging unit further includes a beam focusing element configured to receive the second portion of sensing light from the beam splitter and direct this sensing light towards the adjacent optical imaging unit.

8. The probe of any one of claims 1 -7, wherein each optical imaging unit is housed in an interior housing formed of rigid and transparent material.

9. The probe of claim 8, wherein the beam focusing element directs the second portion of sensing light along a fibre optic cable connecting the interior housings of adjacent optical imaging units.

10. The probe of claim 9, wherein the beam focusing element is rigidly mounted

within the interior housing.

1 1 . The probe of claim 9, wherein the beam focusing element is rigidly mounted

relative to one or more of: the fibre optic cable, the focusing element, and the beam splitter.

12. The probe of any one of claims 1 -1 1 , wherein the probe further includes one or more pressure sensors.

13. The probe of claim 12, wherein the one or more pressure sensors are Fibre

Bragg gratings configured to optically image pressure variations of the pathway.

14. The probe of any one of claims 1 -13, wherein the beam splitters of the plurality of optical imaging units of the probe rotate simultaneously to each other.

15. The probe of any one of claims 1 -13, wherein the beam splitters of the plurality of optical imaging units of the probe rotate separately from one another.

16. The probe of any one of claims 1 -15, wherein the beam splitters of the plurality of optical imaging units of the probe rotate at a same speed.

17. The probe of any one or claims 1 -16, wherein the beam splitters of the plurality of optical imaging units of the probe rotate at different speeds.

18. The probe of any one of claims 1 -17, wherein the pathway is a biological lumen.

19. A system for optically imaging a biological lumen including:

a first light pipe having a proximal end and a distal end;

a light source and a photo detector connected to the proximal end of the first light pipe; and

a probe according to any one of claims 1 to 17 connected to the distal end of the first light pipe, configured to receive the sensing light from the light source and direct the returned light to the photo detector via the first light pipe.

20. The system of claim 19, further including a de-multiplexing unit configured to demultiplex the sensing light into a plurality of channels, each channel being associated with an optical path delay corresponding to an optical path length of an optical imaging unit of the probe.

21 . The system of claim 19, further including an optical delay line scanner located along the first light pipe, wherein the optical delay line scanner is configured to perform at least two scanning oscillations of one or more channels of the sensing light with a predetermined time period.

22. The system of claim 19, further including an optical delay line scanner located along a second light pipe connected to the first light pipe and configured to transmit reference light to a reference mirror, wherein the optical delay line scanner is configured to perform at least two scanning oscillations of one or more channels of the reference light within a predetermined time period.

23. A method including: providing, over a light path, sensing light to a probe inserted within a pathway, the probe comprising a plurality of beam splitters along a longitudinal dimension of the probe;

at a first beam splitter of the probe, directing a first portion of the sensing light in a radial direction from the probe onto a first wall portion of the pathway and passing a second portion of the sensing light onto a second beam splitter of the probe;

at the second beam splitter of the probe, directing the second portion of the sensing light in a radial direction from the probe onto a second wall portion of the pathway, different from the first wall portion;

while the first and second portions of the sensing light are directed onto the first and second wall portions of the pathway respectively, rotating the radial directions about respective longitudinal axes;

while rotating the radial directions, directing light returned responsive to the first and second portions of the sensing light to a detector for forming an image of the pathway.

24. The method of claim 23, further including

at the first beam splitter of the probe, passing a third portion of the sensing light onto the second beam splitter of the probe;

at the second beam splitter of the probe, passing the third portion of the sensing light onto a further optical element of the probe.

25. The method of claim 24, further including:

at the further optical element of the probe, directing the third portion of the sensing light in a radial direction onto a third wall portion of the pathway, different from the first wall portion and the second wall portion;

while the third portion of the sensing light is radially directed onto the third wall portion, rotating the radial direction about a longitudinal axis.

26. The method of claim 25, further including: at the further optical element of the probe, passing the third portion of the sensing light pass a Fibre Bragg grating that affects the third portion of the sensing light dependent on an applied pressure at the Fibre Bragg grating;

returning light passing the Fibre Bragg grating to a detector, for forming an image pressure within the pathway.

27. The method of any one of claims 23-26, wherein the pathway is a biological lumen.

28. The method of claim 27, including rotating the first and second beam splitters and directing the returned light over one or more deformation cycles of the biological lumen.

29. The method of claim 28, including rotating the first and second beam splitters through at least several full revolutions during each of the one or more deformation cycles.

30. A method including:

providing, over a light path, sensing light to a probe inserted within a pathway;

at a first optical element within the probe:

generating a first measurement signal indicative of the shape of the first wall portion of the pathway by directing a first portion of the sensing light in a radial direction from the probe onto the first wall portion and receiving light reflected back from the first wall portion; and

passing a second portion of the sensing light along the probe to a second optical element within the probe,

at the second optical element within the probe, generating a second measurement signal, wherein the second measurement signal is indicative of:

the shape of a second wall portion, different from the first wall portion; or

a pressure within the pathway at the second optical element.

31 . The method of claim 30, wherein the pathway is a biological lumen.

32. A probe for insertion into a lumen, the probe including a first optical imaging unit, the first optical imaging unit including:

a light path traversing a longitudinal axis of the optical imaging unit;

a beam splitter located along the light path; and

a motor configured to rotate the beam splitter about the longitudinal axis of the optical imaging unit;

wherein the beam splitter is configured to:

direct a first portion of sensing light transmitted to the beam splitter along a light path out from the probe in a radial direction and pass a second portion of the sensing light towards a second optical imaging unit of the probe; and

receive light returned to the probe from said radial direction and direct the returned light along the light path.

33. A method including:

providing sensing light to a probe inserted within a pathway carrying a fluid including suspended particles;

at a first optical element within the probe:

generating a first measurement signal indicative of a time that a particle travels past the first optical element by directing a first portion of the sensing light in a radial direction outwards from the probe and receiving light reflected back from the particle; and

passing a second portion of the sensing light along the probe to a second optical element located at a predetermined distance from the first optical element;

at the second optical element within the probe, generating a second measurement signal indicative of a further time that the particle travels past the second optical element by directing a second portion of the sensing light in a radial direction outwards from the probe and receiving light reflected back from the particle; and

determining, based on the first and second measurement signals and the predetermined distance, a speed of the particle.

34. A method including:

at an optical element within the probe, generating a first measurement signal at a first time, the first measurement signal indicative of a first optical path length by directing a first portion of the sensing light in a radial direction outwards from the probe and receiving light reflected back from a particle deposition layer on the pathway;

determining, from the first measurement signal, a thickness of the particle deposition layer at the first time.

35. The method of claim 34 further including:

at the optical element within the probe, generating a second measurement signal at a second time and receiving light reflected back from the particle disposition layer,

determining, from the second measurement signal, a thickness of the particle deposition layer at a second time;

determining a rate of deposition of the particle disposition layer from the thickness of the particle deposition layer at the first and second time.