Imaging system and method

Abstract

The present invention provides a system, which includes: a medical device, which is configured to be at least partially located in a scattering medium, and the medical device includes at least one optical fiber or other waveguide, and the at least one optical fiber or other waveguide has a plurality of light-emitting areas arranged along at least a portion of its length; a pulsed light source, which is configured to transmit pulsed light to the proximal end of the at least one optical fiber or other waveguide, so that the pulsed light is guided along the at least one optical fiber or other waveguide to the light-emitting area and emitted by the light-emitting area to the scattering medium; at least one detector, which is configured to receive photons of the pulsed light that have passed through the scattering medium; and a processor, which is configured to: select signals corresponding to at least some of the received photons; determine the respective positions of each light-emitting area based on the selected signals; and determine the path of at least a portion of the medical device based on the determined positions.

Description

Technical Field

[0001] The present invention relates to systems and methods for determining the position of a medical device located within a scattering medium, such as within human or animal tissue. Background Art

[0002] Fiber-optic based endoscopes are increasingly used for imaging and sensing inside the human body. While a large volume endoscope can often be guided to a specific area of ​​an internal organ by a steering mechanism, a narrow fiber-optic endoscope may have been pushed out of the working channel of the large volume endoscope, out of reach of conventional systems. Alternatively, a narrow fiber-based endoscope may be inserted without any guidance of the large volume endoscope at all.

[0003] In some cases, the final position of the endoscope can be estimated based on knowledge of insertion of a large volume endoscope, the manual feel of the clinician, and / or the visible structures in the very limited (e.g., less than 1 mm) field of view of a fiber-based endoscopic imaging system. In some cases, stereotactic techniques can be used to estimate the position of the fiber endoscope tip. X-ray or electromagnetic techniques can be used to view the metal end tip that may be on the end of the endoscope. However, X-ray or electromagnetic techniques may be expensive and / or require large volume devices. In addition, using X-rays to determine the position of the endoscope may expose the patient to undesirable radiation.

[0004] It is known to use enteral feeding tubes such as nasogastric (NG) tubes to provide nutrition to patients. Typically, NG tubes are placed blindly. For example, the insertion process of the NG tube can be performed without any imaging process during insertion. Subsequently, an X-ray examination can be used to confirm the position of the NG tube.

[0005] In some cases, misplacement of the bowel may occur. Misplacement of a bowel tube (e.g., a nasogastric tube) may cause various problems. A misplaced bowel tube may result, for example, in direct feeding into the lungs or feeding into the esophagus and subsequent aspiration pneumonia. Pulmonary complications may result in death or disability.

[0006] The feeding regimen using an NG tube can be continuous or intermittent. Typically, the position of the distal end of the NG tube is checked before feeding. Currently, fluid aspiration and pH indicator strips are used. Fluid can be aspirated from the NG tube (e.g., using a syringe), and the aspirated fluid can be tested using a pH indicator strip to determine the acidity of the aspirated fluid. It can be considered that a low pH (e.g., a pH below 4) indicates that the NG tube has been correctly placed. However, in some cases, the pH of the aspirated fluid may be confused due to the simultaneous use of antacids, other medications, or failure of the test indicator.

[0007] A chest X-ray can be used to check the position of the NG tube. However, chest X-rays are often difficult to interpret. Chest X-rays require the use of ionizing radiation. Chest X-rays generally provide static images. A chest X-ray may require moving the patient to the radiology department or to a portable radiographer.

[0008] Current practice can be considered suboptimal. Many deaths and complications continue to occur due to bowel misalignment. Summary of the invention

[0009] In a first aspect, a system is provided, comprising: a medical device configured to be at least partially located within a scattering medium, the medical device comprising at least one optical fiber or other waveguide having a plurality of light emitting regions arranged along at least a portion of its length; a pulsed light source configured to transmit pulsed light to a proximal end of the at least one optical fiber or other waveguide so that the pulsed light is guided along the at least one optical fiber or other waveguide to the light emitting regions and emitted by the light emitting regions into the scattering medium; at least one detector configured to receive photons of the pulsed light that have passed through the scattering medium; and a processor configured to: select signals corresponding to at least some of the received photons; determine the respective positions of each light emitting region based on the selected signals; and determine the path of at least a portion of the medical device based on the determined positions.

[0010] The scattering medium may include at least a portion of a body, which may be the body of a human or animal subject (eg, a patient).The scattering medium may include tissue and / or fluid.

[0011] The medical device may include an endoscope. The medical device may include a tube. The tube may include an enteral tube, such as a nasogastric tube.

[0012] Determining the path of at least a portion of a medical device can enable a clinician to determine the orientation of the medical device. For example, a clinician can determine whether an endoscope or a bowel tube has been misplaced during insertion. Misplacement events can be reduced, which can reduce the incidence of misplacement consequences (such as aspiration pneumonia).

[0013] Determining the location of the light emitting region by providing pulsed light via at least one optical fiber or other waveguide can allow the path of at least a portion of a medical device to be determined without using other methods that may expose the patient or other subject to undesirable radiation. For example, it may be desirable to minimize the use of ionizing radiation in the case of children. Movement of a medical device over time can be determined and / or positioning of a medical device can be checked without repeatedly or continuously exposing the patient to ionizing radiation.

[0014] Determining the location of the light emitting area by providing pulsed light via at least one optical fiber or other waveguide can allow the path of at least a portion of a medical device to be determined without bringing the patient (who may be frail) to an X-ray machine or without bringing a portable X-ray machine to the patient.

[0015] The light emitting regions may be localized. The light emitting regions may act as point sources. Determining the respective position of each light emitting region may include assuming that the light emitting region is a point source.

[0016] The light emitting regions may be regularly spaced along the length of at least a portion of at least one optical fiber or other waveguide. The spacing of the light emitting regions may be uniform. The light emitting regions may be separated by substantially non-light emitting regions of at least one optical fiber or other waveguide.

[0017] The light emitting areas may be arranged more densely in a target area of ​​the medical device. The target area may be considered a critical area. The target area may be located at or near the distal end of the medical device. In some cases, the position of the distal end of the medical device may be less certain than the proximal end. Providing a greater density of light emitting areas near the distal end may allow for better determination of the position of the distal end.

[0018] The spacing between adjacent light emitting regions along the length of at least one optical fiber or other waveguide may be at least 0.1 cm, optionally at least 0.5 cm, further optionally at least 1 cm. The spacing between adjacent light emitting regions along the length of at least one optical fiber or other waveguide may be less than 5 cm, optionally less than 2 cm, further optionally less than 1 cm.

[0019] The at least one optical fiber may include a plurality of optical fibers. Each light emitting region may include a tip of a respective one of the plurality of optical fibers.

[0020] Each light emitting region may include a region in which at least one physical property of the core and / or cladding of at least one optical fiber or other waveguide is altered such that light is emitted from the light emitting region into a scattering medium.

[0021] Each light emitting region may include at least one of a long period fiber Bragg grating, a tilted fiber Bragg grating, and a core damage region. Each light emitting region may be configured to shift the wavelength of the pulsed light. Each light emitting region may be configured to shift the wavelength of the pulsed light by a respective value, so that different light emitting regions emit light having different wavelengths.

[0022] Each light emitting area may be angled to direct light outwardly from the medical device. Each light emitting area may be altered to direct light outwardly from the medical device.

[0023] Different light emitting regions may be configured to transmit and / or scatter different wavelengths of light.

[0024] Each light emitting region may include a scattering material. At least one property of the core and / or cladding may be configured to scatter light into the scattering medium. The scattering material may be configured to scatter light in a direction substantially perpendicular to the length of the medical device.

[0025] At least one property of the material of the medical device may be configured to scatter light into a scattering medium, such as a property of the material of a tube, sheath, or coating.

[0026] At least one optical fiber or other waveguide may be formed of glass. At least one optical fiber or other waveguide may be formed of plastic. At least one optical fiber or other waveguide may be formed of silica.

[0027] The or each optical fiber may have commercially standard dimensions. The or each optical fiber may have a core diameter of approximately 10 μm. The or each optical fiber may have a cladding diameter of approximately 125 μm. The or each optical fiber may have a plurality of cores, each core having a core diameter of approximately 50 μm or approximately 62.5 μm and a cladding diameter of approximately 125 μm. The or each optical fiber may comprise a plastic fiber having a core diameter of approximately 1 mm.

[0028] The or each optical fiber may have a core diameter greater than 1 μm, optionally greater than 3 μm, further optionally greater than 5 μm, further optionally greater than 10 μm, further optionally greater than 50 μm. The or each optical fiber may have a core diameter less than 1 mm, optionally less than 200 μm, optionally less than 100 μm, further optionally less than 50 μm, further optionally less than 20 μm, further optionally less than 10 μm, further optionally less than 5 μm. The or each optical fiber may have a cladding diameter greater than 50 μm, optionally greater than 100 μm, further optionally greater than 500 μm. The or each optical fiber may have a cladding diameter less than 1000 μm, optionally less than 500 μm, further optionally less than 200 μm.

[0029] The at least one optical fiber or other waveguide may include a plurality of optical fibers or other waveguides.Each light emitting region may be located at the tip of a respective one of the optical fibers or other waveguides.

[0030] A plurality of optical fibers or other waveguides may be packaged together, for example in a sheath. A plurality of optical fibers may be packaged together to form a composite fiber bundle. A plurality of optical fibers or other waveguides may include at least 10, optionally at least 20, further optionally at least 50, further optionally at least 100 optical fibers or other waveguides.

[0031] The medical device may include a tube. The composite fiber bundle may be located within a lumen of the tube. The composite fiber bundle may be integrated into the tube material of the tube.

[0032] The plurality of optical fibers or other waveguides may have different lengths. The plurality of optical fibers or other waveguides may be arranged such that the proximal ends of the optical fibers are aligned. The plurality of optical fibers or other waveguides may be arranged such that the distal ends of the optical fibers or other waveguides are spaced apart along the length of at least a portion of the medical device.

[0033] Each light emitting region may comprise a change in a respective one of a plurality of optical fibres or other waveguides. The optical fibres may be changed before being packaged together.

[0034] Multiple light emitting regions may be provided along at least a portion of the length of a single optical fiber or other waveguide. Light emitting regions may be provided along the length of a single optical fiber core. Each light emitting region may comprise a respective change of the optical fiber core.

[0035] The plurality of light emitting regions may be arranged on the plurality of cores of the multi-core optical fiber. Each light emitting region may comprise a variation of the respective core of the multi-core optical fiber.

[0036] The core may include a plurality of subsets of cores, wherein for each subset, the cores in the subset have a corresponding light emitting region.Each core in a subset may have a light emitting region at the same position along the length of the multi-core optical fiber as the other cores in the subset.

[0037] The cores of the multi-core fiber may be separated by a distance greater than the diameter of each core in the cross-sectional plane of the multi-core fiber. The cores may be separated by a separation distance similar to the diameter of each core in the cross-sectional plane of the multi-core fiber. The separation distance may be less than 100 μm, optionally less than 50 μm, further optionally less than 20 μm, further optionally less than 10 μm. The separation distance may be greater than 1 μm, optionally greater than 10 μm, further optionally greater than 20 μm, further optionally greater than 50 μm.

[0038] The medical device may comprise a tube. The medical device may comprise an intestinal tube, optionally a nasogastric tube. At least one optical fiber or other waveguide may be located within the lumen of the tube. At least one optical fiber or other waveguide may be integrated into the tube material of the tube.

[0039] The tube may include at least two lumens. At least one optical fiber or other waveguide may be located in a first lumen of the at least two lumens. A second lumen of the at least two lumens may be configured to supply liquid, such as a feeding liquid. A second lumen of the lumen may be configured to supply liquid to and / or obtain liquid from a human or animal subject.

[0040] At least one detector may be located outside the scattering medium. The selection of signals may be based on the arrival time of the received photons at at least one detector. By selecting signals based on the arrival time, a signal may be selected that represents a photon that has not undergone scattering or has undergone a lesser amount of scattering than most photons. A signal may be selected that represents a photon that has undergone a certain degree of scattering that does not significantly reduce the amount of position information provided by the photon. A signal may be selected that represents a photon that has undergone a certain degree of scattering that does not significantly reduce the amount of position information provided by the photon that exceeds the available limit. Position information may be provided by each photon. For each photon, the position information provided by the photon may include information about the position from which the photon was emitted.

[0041] Position information may be provided by each of the plurality of sets of photons. A set of photons may include photons collected at specific time intervals in a specific detector or detector element. For each set of photons, the position information provided by the set of photons may include information about the position from which the set of photons was emitted.

[0042] The location may include a location on an optical fiber or other waveguide. The location may include the location of a light emitting region from which a photon was emitted. The location may include the location of a light emitting region from which a set of photons was missed. The location information provided by the photons may include information about the locations of multiple light emitting regions.

[0043] A signal may be selected that represents photons that have been substantially scattered toward at least one detector.Such a signal may provide a better location of the light emitting region than a signal that is not selected based on arrival time.

[0044] Determining the position of each light emitting region based on the selected signal may include forming at least one image using the selected signal, and determining the position of each light emitting region based on the at least one image.

[0045] The at least one image may include a respective image of each light emitting region.Determining the position of each light transmitting feature may be based on the image of the light transmitting feature.

[0046] Each position may be determined automatically. Each position may be determined manually. Each position may be determined by processing the image or a respective one of the images using image processing techniques. Each position may be determined by finding a portion of the image or a respective one of the images having a high intensity (e.g., the pixel of the image having the maximum intensity).

[0047] The selection may include selecting a signal corresponding to a ballistic photon. A ballistic photon may include a photon that has not experienced scattering in a scattering medium and / or a photon that has experienced a small number of scattering events compared to most photons. A ballistic photon may include a first photon of a pulse of light to be received at at least one detector. A ballistic photon may include a photon received within a first time bin.

[0048] The selection may include selecting a signal corresponding to a serpentine photon. A serpentine photon may include a photon that arrives later than a ballistic photon but retains some position information. A serpentine photon may include a photon that has been scattered along a more direct path toward at least one detector.

[0049] For each serpentine photon, the position information provided by the photon may include information about the position from which the photon was emitted. For each set of serpentine photons, the position information provided by the serpentine set of serpentine photons may include information about the position from which the set of serpentine photons was emitted.

[0050] The location may include a location on an optical fiber or other waveguide. The location may include the location of a light emitting region from which a photon was emitted. The location may include the location of a light emitting region from which a set of photons was emitted. The location information provided by the serpentine photons may include information about the locations of multiple light emitting regions.

[0051] For each photon, the arrival time of the photon can be determined by measuring the difference between the time when the at least one detector receives the photon and the time when the pulsed light source emits a light pulse thereby triggering the emission of the photon from the optical fiber or other waveguide.

[0052] The selection of signals may include selecting signals having an arrival time below a threshold. The threshold may be expressed relative to the shortest detected arrival time. The selection of signals may include selecting signals that arrive no more than 10 nanoseconds, optionally no more than 5 nanoseconds, further optionally no more than 2 nanoseconds, further optionally no more than 1 nanosecond after the shortest detected arrival time. The selection of signals may include selecting signals that arrive no more than 500 picoseconds, optionally no more than 100 picoseconds, further optionally no more than 50 picoseconds after the shortest detected arrival time.

[0053] The selection of signals may include selecting signals whose arrival times are within a certain time interval. The selection of signals may include selecting signals within one or more time bins.

[0054] The selecting of the signals may include selecting a first group of signals whose arrival times are within a first time bin; selecting a second group of signals whose arrival times are within a second time bin; and comparing the first group of signals to the second group of signals.

[0055] The first time bin may include the first 50 picoseconds after the shortest detected arrival time. The second time bin may include the next 50 picoseconds after the first time bin.

[0056] The first time bin may include the first 100 picoseconds after the shortest detected arrival time. The second time bin may include the next 100 picoseconds after the first time bin.

[0057] The selection of signals may include selecting a first group of signals having arrival times below a first threshold; selecting a second group of signals having arrival times above the first threshold but below a second threshold; and comparing the first group of signals to the second group of signals. The selection of signals may include selecting signals between a number of thresholds and comparing those signals. The selection of signals may include selecting multiple groups of signals, each group of signals including signals having arrival times between different thresholds, and comparing at least some of the multiple groups of signals to each other.

[0058] The selection of signals may include selecting a plurality of groups of signals, each group of signals including signals having arrival times within respective time bins. The time bins may include 50 picosecond time bins. The time bins may include 100 picoseconds. The plurality of groups of signals may include signals within a total range of 1 nanosecond arrival times. The plurality of groups of signals may include signals within a total range of 5 nanosecond arrival times.

[0059] The position of at least one detector and / or the incident position of the light may be varied to create an image by scanning the light across a scanning medium (eg, across a patient).

[0060] Determining the path of at least a portion of the medical device may include applying shape-based image processing techniques. An expected shape of the medical device and / or an expected shape of at least one optical fiber or other waveguide may be used to determine the path of the medical device. For example, it is known that the medical device may be continuous. It may be assumed that the medical device will take a curved shape. It may be assumed that the curvature of the medical device is within predetermined limits.

[0061] Determining the path of at least a portion of the medical device may include using prior knowledge of the spacing of the light emitting areas.

[0062] The pulsed light may include narrowband laser light. The pulsed light may include short pulsed laser light. The pulsed light may include pulses having a length of less than 1000 ps, ​​optionally less than 500 ps, ​​further optionally less than 100 ps, ​​further optionally less than 10 ps, ​​further optionally less than 1 ps.

[0063] The pulsed light may have a pulse frequency of up to 1000 MHz, optionally up to 200 MHz, further optionally up to 100 MHz, further optionally up to 10 MHz. The pulsed light may have a pulse frequency of 10 to 100 MHz. The pulsed light may have a pulse frequency of about 80 MHz. The pulsed light may have a pulse frequency of 1 to 10 MHz.

[0064] The pulsed light source may have an illumination power of less than 100 mW, optionally less than 50 mW, optionally less than 20 mW, optionally less than 10 mW, optionally less than 1 mW.

[0065] The system may further comprise a filter configured to filter received photons. The filter may be configured to transmit photons at a pulsed light wavelength. The filter may be configured to transmit photons at a pulsed light wavelength as offset by at least one light emitting region.

[0066] At least one detector may include a detector array. At least one detector may include a scanning detector. At least one detector may include a single photon detector. The single photon detector may include at least one SPAD (single photon avalanche diode). At least one detector may include at least one of the following: APD (avalanche photodiode detector), ultrafast scanning camera, time gate enhanced camera with CCD detector array (ICCD), photomultiplier tube (PMT), superconducting single photon detector.

[0067] The system may further comprise at least one focusing assembly, wherein the at least one focusing assembly is configured to focus the received photons onto at least one detector. The at least one focusing assembly may comprise at least one lens.

[0068] Transmitting the pulsed light to the scattering medium may include individually illuminating each light emitting region. Individually illuminating each light emitting region may include sequentially illuminating each light transmitting feature. Individually illuminating each light emitting region may include illuminating each light emitting region using a respective different wavelength. Individually illuminating each light emitting region may include individually illuminating each of a plurality of cores of at least one optical fiber. Individually illuminating each light emitting region may include sequentially illuminating at least one optical fiber or other waveguide using a different wavelength, wherein each light emitting region is configured to transmit a selected one of the different wavelengths.

[0069] Transmitting the pulsed light into the scattering medium may include illuminating a plurality of light emitting regions simultaneously. Transmitting the pulsed light into the scattering medium may include illuminating all light emitting regions simultaneously.

[0070] Determining the position of the light emitting area may be performed repeatedly. Determining the position of the light emitting area may be performed repeatedly while moving at least a portion of the medical device relative to the scattering medium. The movement of the medical device may be automatic. The movement of the medical device may be performed in predetermined increments.

[0071] The medical device may comprise or form part of at least one medical instrument. The medical device may be co-located with at least one medical instrument.

[0072] The medical instrument may include at least one of an endoscope, a guidewire, a catheter, a catheter delivery system, a scalpel, and an energy source for tissue ablation or modification.

[0073] The processor may be further configured to determine a position of at least a portion of the medical instrument based on the determined path of at least a portion of the medical device.

[0074] The medical device may be located at least partially inside a human or animal body.Determining the path of at least a portion of the medical device may include determining the path of at least a portion of the medical device inside the human or animal body.

[0075] The medical device and / or medical instrument may be placed inside a human or animal body using an automated procedure. Determining the path of at least a portion of the medical device may include validating the automated procedure.

[0076] At least a portion of the medical device may be located inside a human or animal subject. The scattering medium may include tissue of at least one of the lungs, upper digestive tract, lower digestive tract, urinary tract, bone tissue, organ tissue.

[0077] At least a portion of the medical device may be located within the esophagus of the subject.The processor may be configured to determine the position of the tube within the esophagus of the subject using the determined path of at least a portion of the medical device.

[0078] The processor may be further configured to use the selected photons to determine a tissue type of at least a portion of the human or animal tissue. Determining the tissue type of at least a portion of the human or animal tissue may include determining whether the tissue is healthy or diseased. Determining the tissue type may include determining a degree of scattering of the photons corresponding to the selected signal, and determining the tissue type based on the determined degree of scattering.

[0079] In another aspect (which may be provided independently), a medical device is provided, the medical device being configured to be at least partially located within a scattering medium, the medical device comprising at least one optical fiber or other waveguide having a plurality of light emitting regions arranged along at least a portion of its length such that light transmitted to a proximal end of the at least one optical fiber or other waveguide is guided along the at least one optical fiber or other waveguide to the light emitting regions and emitted by the light emitting regions.

[0080] In another aspect (which may be provided independently), a method for determining a path of at least a portion of a medical device is provided, the medical device comprising at least one optical fiber or other waveguide having a plurality of light emitting regions arranged along at least a portion of the length of the at least one optical fiber. The method comprises: positioning the medical device at least partially within a scattering medium; transmitting pulsed light to the at least one optical fiber or other waveguide so that the pulsed light is guided along the at least one optical fiber or other waveguide to the light emitting region and emitted by the light emitting region into the scattering medium; receiving photons of the pulsed light that have passed through the scattering medium by at least one detector; selecting signals corresponding to at least some of the received photons; determining the respective positions of each light emitting region based on the selected signals; and determining the path of at least a portion of the medical device based on the determined positions.

[0081] In another aspect (which may be provided independently), a computer program product is provided, the computer program product comprising computer-readable instructions executable by a processor to select signals corresponding to received photons of pulsed light that have passed through a scattering medium, to determine the respective positions of each of a plurality of light-emitting areas based on the selected signals, and to determine a path of a medical device based on the determined positions.

[0082] The scattering medium may include at least a portion of a body of a human or animal subject.The processor may be further configured to compare the determined position of the medical device to an expected anatomy of the subject.

[0083] The processor may be further configured to determine an expected anatomical structure of the subject. Determining the expected anatomical structure may include obtaining at least one medical image of at least a portion of the subject's body. Determining the expected anatomical structure may include processing at least one medical image to identify at least one anatomical structure. The at least one anatomical structure may include an esophagus. The at least one anatomical structure may include a bronchus. The at least one anatomical structure may include a pyloric plane of the subject. The at least one anatomical structure may include at least one intercostal space of the subject. The at least one anatomical structure may include at least one vertebra of the subject.

[0084] Comparing the position of the medical device to the expected anatomy of the subject may include determining the position of the medical device relative to the esophagus and / or bronchi.

[0085] Comparing the position of the medical device to the expected anatomy of the subject may include overlaying a medical image of the subject with the determined position of the or each light transmission feature and / or the determined position of the medical device. Comparing the position of the medical device to the expected anatomy of the subject may include overlaying at least one anatomical landmark with the determined position of the or each light transmission feature and / or the determined position of the medical device.

[0086] The processor may be configured to identify at least one anatomical feature in the medical image and use the identified at least one anatomical feature for comparing the position of the medical device to an expected anatomy of the subject. Identifying the at least one anatomical feature may include segmenting and / or labeling the at least one anatomical feature.

[0087] In another aspect (which may be provided independently), a graphical user interface is provided that is configured to display the position of each of a plurality of light-emitting regions based on a selected signal, display signals corresponding to received photons of pulsed light that have passed through a scattering medium, and / or display a path of a medical device that has been determined using the positions of the plurality of light-emitting regions.

[0088] In another aspect (which may be provided independently), a system is provided, comprising: a medical device, the medical device being configured to be at least partially located within a scattering medium, the medical device comprising at least one optical fiber or other waveguide, the at least one optical fiber or other waveguide having a plurality of light-receiving regions arranged along at least a portion of its length; a pulsed light source, the pulsed light source being outside the scattering medium and being configured to transmit pulsed light into the scattering medium; at least one detector, the at least one detector being coupled to a proximal end of the at least one optical fiber or other waveguide, wherein the at least one detector is configured to receive photons of the pulsed light that have passed through the scattering medium and have been received by the light-receiving regions and guided along the at least one optical fiber or other waveguide to the at least one detector; and a processor, the processor being configured to: select signals corresponding to at least some of the received photons; determine a respective position of each of the light-receiving regions based on the selected signals; and determine a path of at least a portion of the medical device based on the determined positions.

[0089] Transmitting the pulsed light to the scattering medium may include changing the position of the light source relative to the scattering medium and / or changing the incident position of the pulsed light from the light source on the scattering medium.

[0090] In another aspect (which may be provided independently), a method of forming a medical device is provided, the method comprising providing at least one optical fiber or other waveguide and manufacturing a plurality of light emitting regions in the at least one optical fiber or other waveguide arranged along at least a portion of the length of the at least one optical fiber or other waveguide.

[0091] The manufacturing of the plurality of light emitting regions may include using a laser, such as a femtosecond laser or a UV laser. The forming of the plurality of light emitting regions may include using UV light. Each of the plurality of light emitting regions may include at least one of a long period fiber Bragg grating, a tilted fiber Bragg grating, and a core damaged region.

[0092] The light emitting regions may be differentiated to transmit and / or scatter light of different wavelengths.

[0093] The at least one optical fiber may include a single core optical fiber. The fabrication of the light emitting regions may include fabricating a plurality of light emitting regions along the core of the single core optical fiber.

[0094] The at least one optical fiber may include a multi-core optical fiber. The fabrication of the light emitting region may include fabricating the light emitting region on a plurality of cores of the multi-core optical fiber.

[0095] In another aspect (which may be provided independently), a method of forming a medical device is provided, the method comprising providing at least one optical fiber or other waveguide, and manufacturing a plurality of light receiving regions in the at least one optical fiber or other waveguide arranged along at least a portion of the length of the at least one optical fiber or other waveguide.

[0096] In another aspect, a system is provided, the system comprising an intestinal tube, the intestinal tube being configured to be at least partially located inside the body of a human or animal subject. The intestinal tube comprises or at least partially contains at least one optical fiber or other waveguide, the at least one optical fiber or other waveguide comprising at least one light emitting area. The system also comprises a pulsed light source, the pulsed light source being configured to transmit pulsed light to the proximal end of at least one optical fiber or other waveguide, so that the pulsed light is guided along the at least one optical fiber or other waveguide to one or more light emitting areas and emitted to the subject's body by the one or more light emitting areas. The system also comprises at least one detector, the at least one detector being configured to receive photons of the pulsed light that have passed through the subject's body; and a processor, the processor being configured to: select signals corresponding to at least some of the received photons; determine the position of the or each light emitting area based on the selected signal; and determine the position of the intestinal tube based on one or more determined positions.

[0097] Using light emissions to determine the position of the bowel tube can reduce instances of misplacement. Clinicians may be able to determine if the bowel tube is properly placed. The position of the bowel tube can be determined without subjecting the subject to radiation.

[0098] The intestinal tube may include a nasogastric tube.At least one optical fiber may be integrated into the wall of the intestinal tube.

[0099] At least one optical fiber or other waveguide may be at least partially contained within the lumen of the intestinal tube.

[0100] Determining the position of the or each light emitting area may be performed repeatedly.Determining the position of the or each light emitting area may be performed repeatedly while moving at least a portion of the intestine relative to the body of the human or animal subject.

[0101] Determining the position of the or each light emitting area may be performed repeatedly while moving at least one optical fiber or other waveguide relative to the intestinal tube. Moving at least one optical fiber or other waveguide relative to the intestinal tube may be automatic. Moving at least one optical fiber or other waveguide relative to the intestinal tube may be performed in predetermined increments.

[0102] The processor may be further configured to compare the determined position of the bowel tube with the expected anatomical structure of the subject.The processor may be configured to repeatedly determine the position of the bowel tube over time and repeatedly compare the determined position of the bowel tube with the expected anatomical structure, for example to determine whether the bowel tube is correctly inserted.

[0103] There may be provided a method, apparatus or system substantially as described herein with reference to the accompanying drawings.

[0104] Appropriately, features in one aspect may be provided as features in any other aspect. For example, features of a method may be provided as features of an apparatus, and vice versa. Any one or more features in one aspect may be provided in combination with any suitable one or more features in any other aspect. DETAILED DESCRIPTION OF THE INVENTION

[0106] Embodiments of the invention will now be described by way of non-limiting examples and are shown in the accompanying drawings, in which:

[0107] Figure 1 is a schematic diagram of a fiber and detector arrangement according to one embodiment;

[0108] Figure 2 is a schematic diagram of a distal end of a medical device according to one embodiment;

[0109] Figure 3 is a schematic diagram of a cross section of a modified fiber according to one embodiment;

[0110] Figure 4 is a schematic diagram of a cross section of a modified multi-core fiber according to one embodiment;

[0111] Figure 5 is a graph of photon counts versus time for a test probe placed in the lung; and

[0112] Figure 6 is a plot of photon counts versus time for a test probe placed in the stomach.

[0113] In some cases, it can be generally observed that light can pass through tissue. For example, a bright white flashlight held against a hand or finger can be observed as a red light on the opposing surface of the hand or finger. Embodiments of the present invention use light passing through tissue (or through any other suitable scattering medium) to determine the path of a medical device within tissue (or other scattering medium).

[0114] Figure 1 An apparatus according to one embodiment is schematically shown. The apparatus comprises a medical device 10, a light source 14, a detector 16, a filter 17, a lens 18 and a processor 20.

[0115] The light source 14 is coupled to the proximal end of the medical device 10 and is configured to deliver pulsed light to the medical device 10. In the present embodiment, the light source 14 is a narrow-band short-pulse laser.

[0116] The medical device 10 is configured to transmit light from the light source 14 to a distal end of the medical device 10 . Figure 1 The medical device 10 is shown positioned inside a patient's lung 12. In other embodiments, the medical device 10 can be positioned inside a different part of a human or animal body, such as the gastrointestinal tract or the urinary tract. In further embodiments, the medical device 10 can be positioned inside any suitable scattering medium. The scattering medium can be, for example, a tissue, a body, or an organ. The scattering medium can be a gas. The scattering medium can be a liquid, such as a turbid liquid. The scattering medium can be referred to as a sample, wherein at least the tip of the medical device 10 is positioned inside the sample.

[0117] Detector 16 (which may be referred to as a camera) is located outside the patient's body. Detector 16 is configured to receive photons and generate an electrical signal corresponding to each received photon. In the present embodiment, detector 16 is a detector array comprising a plurality of detector elements. Detector 16 is a time-resolved single-photon imaging system. In this case, the time-resolved single-photon imaging system includes a 32x 32 array of SPADs (single-photon avalanche diodes). The time-resolved single-photon imaging system operates by time-correlated single-photon counting (TCSPC). In other embodiments, any suitable time-resolved detector may be used. The time-resolved detector may be a time-resolved detector capable of detecting low levels of light (e.g., capable of detecting single photons). The time-resolved detector may include an APD (avalanche photodiode) detector or an ultrafast scanning camera. The time-resolved detector may include a time-gate enhanced camera with a CCD detector array (ICCD). The time-resolved detector may include a plurality of photomultiplier tubes (PMTs) or superconducting single-photon detectors. In some embodiments, a plurality of detectors 16 may be used. In some embodiments, a single-element detector may be used in combination with an optical scanning system to produce an image.

[0118] In this embodiment, the detector 16 is mounted on an arm (not shown) that can be located at any suitable position relative to the patient's body. In other embodiments, any suitable mounting of the detector 16 can be used. For example, the detector 16 can be mounted on the ceiling of a room where the procedure of positioning the medical device 10 inside the patient is performed, such as the ceiling of a hospital room or operating room. In some embodiments, the detector 16 can be mounted on the head or body of a clinician, assistant, or other user to provide intuitive feedback to the clinician, assistant, or other user.

[0119] The lens 18 is located between the detector 16 and the patient's body. The detector 16 and the lens 18 are arranged so that the detector 16 is focused on the patient's body. In other embodiments, an alternative focusing assembly may be used in place of the lens 18, or no focusing assembly may be used.

[0120] Filter 17 is located in front of detector 16. In the present embodiment, filter 17 is located between detector 16 and lens 18. In the present embodiment, filter 17 is a narrow line bandpass filter. Filter 17 is configured to block any photons that are not within the spectral band of laser source 14. In other embodiments, alternative filters may be used, or no filter may be used.

[0121] Detector 16 is connected to processor 20, and described processor 20 is configured to receive signal from detector 16 and analyze signal.Processor 20 can comprise any suitable processing equipment, for example computer equipment, such as desktop PC, notebook computer or mobile device.Although detector 16 and processor 20 are separate components in the present embodiment, in other embodiments, the function of detector 16 and processor 20 can be combined in single component.The function described as being performed by detector 16 can be performed by processor 20, and vice versa.

[0122] Figure 2 yes Figure 1 Schematic diagram of the distal end of the medical device 10. Figure 2 The diagrams are schematic and not drawn to scale.

[0123] Figure 2 The medical device 10 includes a catheter 30, which may also be referred to as a tube. Multiple optical fibers 32 are each individually fed inside the lumen of the catheter 30 to form the medical device 10. Each optical fiber 32 terminates at a different distance down the catheter, so that the distal end of each optical fiber 32 acts as a point light source at a different point along the catheter 30. The tip of the optical fiber 32 can be described as a termination point, a light emitter, or a light emitting area.

[0124] exist Figure 2 In some embodiments, the termination points of the optical fibers 32 are spaced evenly apart by 1 cm. In other embodiments, the spacing of the fibers may be closer along the length of the device. In other embodiments, the spacing of the termination points of the fibers may not be even. For example, the distribution of the termination points along the length of the device may become denser as it approaches the tip of the device.

[0125] exist Figure 2 In some embodiments, the individual fibers have standard dimensions. The individual fibers have a core diameter of approximately 10 μm and a cladding diameter of approximately 125 μm. In other embodiments, any suitable fiber size may be used. The optical fiber may be formed of glass or plastic.

[0126] For each optical fiber 32, the end of the optical fiber can be considered to act as a local light source. The end of the optical fiber can be considered to act as a single point source of pulsed light. If the number of optical fibers is N, then Figure 2 The method allows the generation of N point-like light sources. The N point-like light sources are distributed along at least a portion of the length of the medical device 10. In some embodiments, the number of optical fibers N can be at least 10, at least 20, at least 50, or at least 100.

[0127] exist Figure 2In an embodiment, the tips of the optical fibers 32 terminate so as to direct light outward from the medical device 10. For example, a scattering element (not shown) may be located at the tip of each optical fiber 32 and / or the tips of the optical fibers 32 may be angled to direct light outward from the medical device 10 (e.g., out the side of the medical device 10).

[0128] In other embodiments, the optical fiber can be bundled or otherwise contained in a sheath, which can be referred to as a packaging sheath. The optical fiber can be coated with a coating. The material of the sheath or coating can be intentionally highly scattering to direct light out of the medical device 10.

[0129] In other embodiments, any medical device comprising at least one optical fiber may be used. Figure 3 Embodiments in which the medical device comprises a single optical fiber are described and are referred to below. Figure 4 Embodiments are described in which the optical device comprises a multi-core optical fiber.

[0130] We turn again to Figure 1 and 2 In operation, light emitted from each termination point of the optical fiber 32 is used to track the length of the optical fiber. Since the termination points are arranged along the length of the medical device 10, the location of the termination points can be used to track the length of the optical fiber. An extended portion of the medical device 10 can be located, not just a single point (e.g., the tip).

[0131] Tanner et al. (MG Tanner, TRChoudhary, TH Craven, B. Mills, M. Bradley, RK Henderson, K. Dhaliwal, and RR Tomson, "Ballistic and snake photon imaging for locating optical endomicroscopy fibres" Biomed. Opt. Express 8, 4077-4095 (2017)) describes a method for determining the position of a light emitter in a scattering medium using time-correlated single photon counting (TCSPC) and is summarized below. Tanner et al. describe a method for locating a point light at the tip of an optical fiber. The following method applies the positioning method of Tanner et al. to each termination point.

[0132] For example, L. Wang, P. P. Ho, C. Liu, G. Zhang, and R. R. Alfano, “Ballistic 2-d imaging through scattering walls using an ultrafast optical kerr gate,” Science 253, 769–71 (1991); V. Ntziachristos, “Going deeper than microscopy: the optical imaging frontier in biology,” Nat. Methods 7, 603–614 (2010); V. Gopal, S. Mujumdar, H. Ramachandran, and A. K. Sood, “Imaging in turbid media using quasi-ballistic Photon transit times are also discussed in “Imaging in turbid media using quasi-ballistic photons,” Opt. Commun. 170, 331–345 (1999); and A. Lyons, A. Boccolini, F. Tonolini, A. Repetti, Z. Chen, R. Henderson, Y. Wiaux, and D. Faccio, “Computational time-of-flight diffuse optical tomography,” arXiv:1808.01135 (2018).

[0133] For example, as part of an endoscopic procedure, the medical device 10 is introduced into the patient's lungs 12. In other embodiments, the medical device 10 can be introduced into any suitable anatomical structure. For example, the medical device can form part of an enteral feeding tube and can be introduced into the esophagus.

[0134] A short pulse (in this embodiment, with a pulse length of <500ps and a pulse frequency of 20MHz) narrowband laser is injected into the first optical fiber in the optical fiber 32 by the light source 14. In other embodiments, any pulsed light with a repeatable leading edge can be used. In this embodiment, the illumination power of the laser source 14 is a few mW, which is known to be safe in tissue. The wavelength of the laser source 14 can be selected to have low scattering and absorption in tissue.

[0135] exist Figure 2In an embodiment, individual light sources can be turned on and off at will from the proximal end.

[0136] Over a period of time that may be seconds or minutes, laser light is injected into the first fiber of optical fiber 32. Each laser pulse propagates down the length of optical fiber 32 and is emitted from the distal tip of optical fiber 32 as a large number of photons (at Figure 1 22). The emission time of the light pulse from the distal tip of optical fiber 10 can be designated as t=0. Only a small number of photons emitted from the distal tip of optical fiber 32 can escape from the body. Many of the photons emitted by optical fiber 32 are absorbed in the tissue. Most of the photons that escape from the body (and can therefore be observed by detector 16) may have experienced a lot of scattering from the disordered tissue structure of the body. The time it takes for each photon to travel through the tissue can depend on how many times the photon has been scattered while traveling through the tissue.

[0137] Photons that pass through tissue and exit the body may include ballistic photons, serpentine photons, and / or highly scattered photons.

[0138] A ballistic photon may be a photon that travels through a scattering medium in a straight line substantially without scattering. Such a photon may be considered to have not collided with atoms of the scattering medium, or to have experienced a very small number of scattering collisions. A ballistic photon may be substantially coherent.

[0139] Slightly scattered photons may be referred to as serpentine photons. Serpentine photons may be those photons that have experienced a small number of scattering events in tissue (more than those designated as ballistic) but may still provide useful position information. Serpentine photons may maintain a certain degree of coherence. Serpentine photons may arrive slightly delayed than ballistic photons.

[0140] Photons that experience a greater degree of scattering may be referred to as highly scattered photons, very scattered photons, or randomly scattered photons.

[0141] Photons that pass out of the body may include ballistic photons, serpentine photons, and highly scattered photons. Some photons that pass out of the body travel in the direction of the detector 16 and are focused onto the detector 16 by the lens 18. Any photons that are not within the spectral band of the laser source 14 may be blocked by a narrow line bandpass filter 17 in front of the detector 16. The ballistic photons arrive first, followed by the serpentine photons, and then the highly scattered photons.

[0142] In practice, the number of photons from each pulse that arrive at the detector 16 can be very small. In particular, only a small number of ballistic and / or serpentine photons can be obtained from each pulse. Therefore, photons from a large number of pulses are collected by the detector 16, and the results are summarized as described below.

[0143] The detector 16 converts each detected photon into an electrical signal. In the present embodiment, the detector 16 operates in a start-stop mode by time-correlated single photon counting (TCSPC). There is synchronization between the light source 14 and the detector 16 via an electrical connection. When the laser source 14 generates a light pulse, it also sends an electrical pulse to the detector 16. When the detector 16 receives the electrical pulse, it starts timing. When the detector 16 observes a photon (for example, when a detector element of a detector array observes a photon), the detector stops timing. The electrical signal representing the detected photon includes an arrival time, which represents the difference between the transmission time of the pulse and the time when the photon arrives at the detector 16.

[0144] In other embodiments, the detector 16 starts timing when it detects a photon and stops timing when it receives the next electrical pulse (reverse start-stop mode). Since the time between pulses is known, the arrival time can be determined. In other embodiments, any suitable method for determining the arrival time can be used.

[0145] In this embodiment, the electrical signal representing the detected photon also includes a position. The position is determined based on which array element(s) in the 32x32 array detected the photon.

[0146] In other embodiments, any suitable method of determining the time of arrival and / or position of each detected photon may be used.The time of arrival and / or position of each photon may be represented by any suitable signal or combination of signals.

[0147] The electrical signals are passed to processor 20. Since the arrival time of each photon is determined relative to the transmission time of its respective pulse, the results can be combined between multiple pulses. Processor 20 combines the electrical signals via a histogram. In other embodiments, processor 20 can combine the electrical signals in any suitable manner. In other embodiments, the electrical signals can be combined in the circuit of detector 16.

[0148] The processor 20 records the photon arrivals in time bins, which in this embodiment are 50 ps time bins. In other embodiments, any suitable time bin size may be used. The processor 20 selects electrical signals whose determined arrival times are within the desired time bins (e.g., within the first 50 ps time bin). In other embodiments, the processor may select electrical signals based on any suitable one or more time thresholds. The selected electrical signals may correspond only to ballistic photons, or to both ballistic photons and serpentine photons, or to any photon that arrives at the detector earlier than a more scattered photon.

[0149] In some embodiments, the processor 20 may select an electrical signal whose arrival time is no more than 100ps, no more than 200ps, or no more than 500ps. In other embodiments, the processor 20 may select an electrical signal whose arrival time is no more than 1ns or no more than 5ns. In other embodiments, the processor 20 may compare signals in different time bins. For example, the processor 20 may compare a signal in a first 50ps time bin with a signal in a second 50ps time bin. The processor 20 may compare a signal in a first 100ps time bin with a signal in a second 100ps time bin. The processor 20 may compare signals in multiple time bins, for example, by comparing signals in each 50ps time bin in a 1ns or 5ns interval. In some embodiments, multiple or different timing windows may be used.

[0150] The processor 20 forms an image from the selected signal, which in this embodiment is a signal that falls within a selected time bin. In this embodiment, the image comprises one pixel for each element of the detector array 16. The detector array 16 comprises 32 x 32 elements, so the image formed is a 32 x 32 pixel image. The intensity of each pixel in the image represents the number of photons whose arrival time is within the selected time bin, which are received by the corresponding array element during the time bin. Each detector element of the detector array can detect light having a different angular origin relative to the detector array.

[0151] Processor 20 determines the position of the tip of optical fiber 32 by processing an image formed by the selected signals. In this embodiment, processor 20 automatically determines the position of the tip of optical fiber 32 using the intensity of each pixel of the image, which represents the number of photons received by each element of the detector array.

[0152] Each received photon provides information about the end point of transmitting it. In this embodiment, the set of photon arrivals is considered when determining the position information. A photon set can be a group of photons that fall into the same time bin and / or pixel. Each of the received photon sets can provide position information about the end point of the photons in the emitted photon set.

[0153] The position determined from the image is a position in a plane, which may be designated as the xy plane, defined by the orientation of the detector array 16. In some embodiments, the position of the medical device 10 in z is also determined by determining the distance between the detector 16 and the tip of the medical device 10 using the time of flight of photons received by the detector 16 (e.g., the time of flight of ballistic photons).

[0154] Laser light is then injected into a second one of the optical fibers 32 and the position of the tip of the second optical fiber 32 is determined as described above. The injection of laser light into the optical fiber 32 and the determination of the position of the tip of the optical fiber 32 are repeated until a respective position has been determined for each optical fiber termination point.

[0155] In this embodiment, the optical fibers 32 are illuminated individually, with only one optical fiber 32 being illuminated at a time. In other embodiments, more than one optical fiber 32 may be illuminated. In some embodiments, all optical fibers 32 are illuminated at once.

[0156] The determined locations of the endpoints are used to determine a path for the medical device 10. Determining the path for the medical device 10 may include determining a line or other elongated geometric structure that follows a longitudinal dimension of the medical device 10. The path may be determined for a portion of the medical device 10, such as a portion located within a patient's body.

[0157] By determining the path of a medical device, a clinician can obtain information regarding whether the medical device has been properly placed (eg, in the lungs or gastrointestinal tract). Various medical applications are further described below.

[0158] Any automatic or semi-automatic method can be used to determine the path of the medical device 10. In some embodiments, knowledge of the spacing between the end points and / or the uniform spacing of the end points is used to determine the path. For example, processing of one or more images obtained from the transmitted light can take into account the expected spacing between light emitters.

[0159] In some embodiments, prior knowledge that the medical device 10 is an elongated device with gentle bends can allow the use of advanced image processing techniques to reconstruct an accurate image of the location of the fiber lengths. For example, image processing techniques can include methods based on probability maps and / or optimization of constrained curve fitting.

[0160] In some embodiments, the computer program is installed on the processor 20, which may include or form a part of any suitable computing device. The computer program is configured to determine the location of the termination point and thereby determine the path of the medical device 10 installed on the processor 20. The computer program is configured to determine the location of the termination point using the electrical signal representing the received photons.

[0161] The computer program can be configured to display a graphical user interface. The graphical user interface can be displayed on a display screen. The graphical user interface can allow a user (e.g., a clinician) to view the determined location of the endpoint and / or the determined path of the medical device 10. By viewing the endpoint and / or the path, the user can obtain information about the location of the medical device 10. The graphical user interface can allow the user to input information, such as information about the subject, the medical device 10, or the procedure being performed. The graphical user interface can allow the user to control or adjust the method for determining the location of the endpoint and / or the path of the device.

[0162] In the above reference Figure 2 In the described embodiment, the fibers 32 are individually inserted into the catheter 30. In other embodiments, the fibers are packaged together in a tube or sheath. Then, the tube or sheath is inserted into a medical instrument (e.g., an intestinal tube or an endoscope). In other embodiments, the packaged fibers are supplied to the medical instrument at an appropriate position and then extracted after positioning. For example, in some embodiments, the packaged fibers are initially located in the working channel of the catheter. If left in place, the packaged fibers may hinder normal use. Therefore, after the catheter is placed in the subject's body and before the catheter is used, the packaged fibers are extracted from the working channel of the catheter. Similar considerations can be applied to any embodiment in which at least one optical fiber is initially located in a medical instrument and then extracted.

[0163] In some embodiments, the medical tubing of the catheter is made of plastic, and the optical fiber is integrated into the plastic of the medical tubing during manufacturing. In other embodiments, the fibers are bundled together with controlled tip spacing and coated to form a single composite fiber bundle. The single composite fiber bundle is then placed in the medical device or tubing. In some embodiments, the composite fiber bundle is integrated into the plastic of the medical tubing or medical device during manufacturing.

[0164] In some embodiments, the medical tubing contains two channels. One channel accommodates the optical fiber. The other channel is used for normal operations (e.g., feeding, drug delivery, and / or sample aspiration).

[0165] exist Figure 2 In some embodiments, the individual fibers are sequentially illuminated by using an optical switch. An optical switch can be a switch that enables a signal in an optical fiber to be selectively switched from one fiber to another, such as described in Federal Standard 1037C, Telecommunications: Glossary of Telecommunication Terms, August 7, 1996.

[0166] In some embodiments, optical fibers are bundled together and illuminated sequentially. The bundled fibers can be illuminated sequentially by a controlled illumination pattern by a digital micromirror device.

[0167] In some embodiments, simultaneous irradiation Figure 2 All optical fibers 32 of the medical device 10 are illuminated simultaneously at the proximal ends resulting in emission at the distal ends of the optical fibers 32, which occurs sequentially from the shortest optical fiber 32 to the longest optical fiber 32, delayed due to propagation along the length of the fiber.

[0168] Reference above Figure 2 The method outlined uses N fibers. Figure 2 The N fibers are co-packaged and carefully placed in a clinically approved package.

[0169] exist Figure 3 In another embodiment shown, a single optical fiber 40 is used. The optical fiber 40 has a single core 42. The core 42 of the optical fiber 40 is modified to a specific length to couple light out of the core, into the cladding and out of the fiber. The modification of the core can be referred to as a light emitting region.

[0170] exist Figure 3 In an embodiment, the interval of change is about 1 cm.

[0171] Figure 3 The coupling of light 44 out of the fiber from a set of changes 46 is schematically shown.

[0172] exist Figure 3 In an embodiment, the change 46 includes structures with different spectral properties. The structures with different spectral properties are made at different points along the fiber. Therefore, the coupling of light 44 out of the core 42 is wavelength dependent.

[0173] exist Figure 3 In some embodiments, the structure 46 made of fiber is a long period fiber Bragg grating (LPG). In other embodiments, the structure 46 is a tilted fiber Bragg grating. In other embodiments, the structure 46 is a damaged line in the cladding of the optical fiber that couples light. In other embodiments, any suitable fiber modification can be used.

[0174] The fiber can be altered using a laser (e.g., a femtosecond laser or UV laser). For example, the fiber can be altered according to Review of femtosecond infrared laser-induced fiber Bragg grating sensors made with a phase mask Stephen J. Mihailov, Dan Grobnic, Christopher W. Smelser, Robert B. Walker, Ping Lu, and Huimin Ding Sensor Review 2011 31:4, 321-327; Donko, Y. Jung, Y. Wang, J. Hayes, S. Alam, G. Brambilla, D. Richardson, and M. Beresna, "Multicore Optical Fiber Components Fabricated Using a Femtosecond Laser Direct Writing," in Frontiers in Optics 2017, OSA Technical Digest (online) (Optical Society of America, 2017), document FW6A.3; or H.S. Roufael, A. Quintela, M. Lomer, and J. Lopez-Higuera, "Stable at High Temperatures LPG's Inscribed by a Femtosecond Fiber Laser," in Workshop on Specialty Optical Fibers and Their Applications, OSA Technical Digest (online) (Optical Society of America, 2015), document WT4A.19. In other embodiments, any suitable method can be used to change the fiber core.

[0175] Laser methods may involve focusing laser radiation through the fiber cladding to focus on the fiber core to change the core. The change may be made by nonlinear light absorption processes of the core material. The change may have wavelength-dependent scattering properties (e.g., long period fiber Bragg gratings (LPGs) or tilted fiber Bragg gratings).

[0176] The Bragg grating may be shaped to direct light in a particular direction. However, the direction of the detector 16 relative to the Bragg grating may be unknown. Scattering materials may be used in combination with the Bragg grating. The use of scattering materials may cause light to be emitted over a wide range of angles.

[0177] In some embodiments, the cladding of the fiber is intentionally made highly scattering to further scatter light out of the fiber cladding toward the detector 16 .

[0178] In use, the wavelength of the light source 14 at the proximal end of the optical fiber 40 is tuned to generate point sources of light at different locations along the fiber. The light source 14 may comprise any tunable light source, such as a tunable pulsed laser or a pulsed white light source with a filter (eg a supercontinuum laser).

[0179] Injecting light of different wavelengths results in different changes in the emitted light 46. As mentioned above Figure 1 and 2 As described, light emitted from the changes 46 can be used to determine the respective position of each change 46.

[0180] Using a single optical fiber can reduce or eliminate the need for co-packaging and careful positioning of fibers. Manufacturing of medical devices can be simplified by providing multiple light emitting areas on a single optical fiber.

[0181] Figure 4 Another embodiment is shown. Figure 4 In an embodiment of the present invention, the medical device comprises an optical fiber 50 having multiple cores 52. Individual cores 52 of the multi-core optical fiber 50 are selectively changed. Different cores are changed at different points down the fiber. Each core can be changed at one or more points on the fiber.

[0182] By exciting different cores at the proximal end, point-like light sources can be generated at different locations down the fiber, thereby outputting light with different changes. The changes can be referred to as light-emitting areas.

[0183] The modification of each core can be performed by any suitable method. For example, each modification can include LPG, tilted FBG or core-specific damage. The modification of the fiber can be performed using a laser (e.g., femtosecond or UV). Femtosecond lasers can provide the possibility of randomly modifying a specific core across the entire cross-section of the fiber.

[0184] The fiber cladding may also be intentionally made highly scattering to further scatter light out of the fiber cladding towards the detector.

[0185] Using multiple cores can avoid the need for tuning the light source wavelength. The same light source wavelength can be used to illuminate all cores.

[0186] In some embodiments, multi-core fiber 50 comprises cores 52 separated by spacings greater than the core diameter. In other embodiments, multi-core fiber 50 comprises a high density of closely spaced cores 52, such as cores 52 having spacings comparable to the core diameter.

[0187] In some embodiments, the changes are directed to one core 52. In other embodiments, the changes are directed to a region of the core 52. In some embodiments, the changes are made by scanning the laser focus across the core 52 while passing through the optical fiber 50 under the laser change system.

[0188] If many core fibers are used, the change can obtain a large number of change positions along the fiber length. In some cases, it can be considered that a large number of change positions form a continuous area of ​​change positions.

[0189] Illumination at the proximal end of a particular core can result in emission of light at any point along the length of the fiber.

[0190] As above reference Figure 1 and 2 As described in the embodiments, an image formed by light emitted from a changed position can be formed and processed.

[0191] In the above reference Figures 1 to 4 In the described embodiments, light is emitted from a medical device located inside the patient's body and received by a detector located outside the patient. However, there are alternative embodiments in which light is emitted by a light source outside the patient and received by a medical device inside the patient.

[0192] In one such embodiment, light from a short pulse laser source is scanned across the patient's body. For example, the light can be scanned across a two-dimensional area of ​​the patient's torso. The medical device is located inside the patient's lungs. Some of the light from the light source passes through the patient's tissue and reaches the medical device through multiple areas that receive light. As described above, the area that receives light can include the fiber tip and / or fiber change.

[0193] A detector is coupled to the proximal end of the medical device (the end outside the patient). The detector can be, for example, a single photon detector. The photons arriving at the medical device are detected by the detector and converted into electrical signals. Their arrival times are recorded. The position of each photon can also be determined based on the position of the scanning light source when transmitting the photon. Photons received from different light-emitting areas can be distinguished by, for example, the optical fiber receiving the photon and / or the wavelength of the received light.

[0194] Signals corresponding to ballistic photons and / or serpentine photons and / or photons that arrive before most of the scattered photons can be selected, for example by time gating or selecting signals in one or more time bins. The selected signals can be used to form one or more images that are used to determine the path of the medical device using the light transmitted into the medical device. In some cases, receiving the photons in darkness (i.e., inside the patient) can be beneficial. In some cases, the noise level can be reduced by transmitting light from outside the patient to inside rather than transmitting light from inside the patient to outside.

[0195] In the above-described embodiments, the path of a medical device in the lungs of a human patient is determined. However, the range of possible applications may be broader. In any suitable medical or veterinary application, the medical device may be located within any human or animal tissue. For example, the medical device may be part of an endoscope delivered to the lungs, upper digestive tract, lower digestive tract, or urinary tract of a human or animal subject. The medical device may be located inside any suitable organ or other tissue. In other embodiments, the medical device may be located inside a scattering material that does not include human or animal tissue.

[0196] In some embodiments, methods of locating an optical fiber using light emitted from the optical fiber (or light received by the optical fiber) can be used to determine the position of a medical instrument in any of a wide variety of medical applications.

[0197] The optical fiber whose position is to be determined can be part of any suitable medical instrument (e.g., an endoscope or catheter delivery system). In some cases, the optical fiber may not be part of the medical instrument, but may be co-located with a portion of the medical instrument. For example, the optical fiber may be placed in a catheter or along a guide wire. The optical fiber may be associated with any placeable device (e.g., any device to be implanted or otherwise delivered to the body). By determining the position of the optical fiber, the position of the medical instrument may also be determined. In one embodiment, the medical instrument comprises an energy source for ablating or changing tissue.

[0198] There are many medical applications in which the position of a medical instrument located within the body can be determined. The above method can be used in any appropriate medical application, such as for training, endoscopic procedures, stent placement, or catheter placement. For example, in training, a method of determining the position of an endoscope using light emitted from a fiber of the endoscope can be used to determine whether the endoscope has been correctly placed by the person being trained.

[0199] In current clinical practice, repeated X-rays can be used to determine the position of a device (such as a catheter) to be placed inside the body. The device can be coated with a radiopaque material so that it is visible on the X-ray. Repeated X-rays expose the patient to X-ray radiation. By using a light-based method to determine the position of the device instead, radiation exposure can be reduced. In some embodiments, the device path determined using light emissions can be overlaid with an X-ray image of the patient.

[0200] In some cases, detector 16 can be used to obtain real-time video of the medical device, which can show the movement of the medical device as it moves within the patient's body. The real-time video can allow instantaneous feeds to be displayed of the location of the medical device. The real-time video can be obtained without irradiating the patient.

[0201] Using the emitted light to obtain the position can increase the confidence of automated procedures (e.g., robotic procedures) performed in vivo. It can be used to determine that the desired position has been reached. In procedures for collecting tissue samples, it can be used to ensure that the sample is collected from the desired sample position. In procedures where multiple samples are to be collected, it can be used to ensure that the spacing of multiple samples is as desired.

[0202] The determined path of the medical device 10 and / or the determined location of the light emitting area can be overlaid with a medical image of the tissue area into which the medical device 10 is inserted. For example, an image obtained from an X-ray or CT scan can be displayed, and the determined path or location can be overlaid with the X-ray or CT scan image. In other embodiments, other types of medical images can be used, such as images obtained from other modalities.

[0203] The medical image overlaid with the determined path and / or position may include anatomical information. For example, anatomical structures may be identified and / or segmented in the medical image.

[0204] Reference above Figures 1 to 4 The devices and methods described or as described by Tanner et al. can be used in the case of nasogastric and enteral feeding tubes. In some embodiments, dynamic time-dependent single photon imaging can be applied to existing NG tubes and enteral feeding tubes.

[0205] In some embodiments, time-correlated single photon imaging is used to observe the dynamic movement of the catheter in a path that follows the expected anatomy of the esophagus of an individual subject.

[0206] Insertion of a catheter (e.g., a nasogastric tube) into a subject is initiated. Pulsed light is injected into at least one optical fiber inserted into or forming part of the catheter. Detection of the pulsed light is used to determine the position of the catheter. The position is determined repeatedly as the catheter insertion is performed.

[0207] For example, in a simple embodiment, light is emitted only from the tip of an optical fiber within the catheter. The location of the point from which the light is emitted is determined and used to determine the location of the catheter tip. As the catheter is inserted into a subject, the tip of the catheter moves further into the subject.

[0208] In other embodiments, light is emitted from multiple light emitting regions of at least one optical fiber within the catheter, and the positions of the multiple light emitting regions are used to determine the path of the catheter.

[0209] The path of the catheter may be determined by determining the positions of multiple light emitting regions along the catheter and / or by repeatedly determining the positions of one or more light emitting regions of the catheter over time as the catheter is inserted.

[0210] The determined position of the catheter may be compared to the expected anatomy of the subject. For example, the subject may have been previously imaged using any suitable imaging method. The path of the esophagus in the subject may have been obtained from previous imaging.

[0211] As described above, the determined path of the medical device 10 can be overlaid on a medical image, such as a photographic image showing anatomical features. Anatomical landmarks can be identified in the medical image. Anatomical structures can be separated in the medical image. By comparing the determined path with the anatomical structures in the image, it can be determined whether the catheter is correctly placed.

[0212] If the determined position of the catheter matches the expected path of the esophagus, it can be determined that the catheter is correctly inserted. Repeated determination of the catheter can allow the user to observe the dynamic movement of the catheter.

[0213] In most individuals, it can be expected that the path of the esophagus will be perpendicular to the oropharynx. A small portion of the esophagus is located behind the sternum. When the light emitter is located in the portion of the esophagus located behind the sternum, additional scattering can be expected to occur due to the presence of high density bone. When the light emitter is located in the portion of the esophagus located behind the sternum, the scattering characteristics of the light received by the detector can be different than when the light emitter is located at other locations in the esophagus.

[0214] It is expected that the tip of the catheter should exit the esophagus in the epigastric region. It is believed that the ideal position where the tip of the catheter should exit the esophagus would be below the pyloric level.

[0215] Therefore, it is expected that the final determined location of the light emitter at the tip of the optical fiber (or the end of a determined path length in other embodiments) can be in the epigastric region and ideally below the pyloric plane.

[0216] It is contemplated that the path of the esophagus (and therefore the path of a catheter inserted into the esophagus) should not involve significant transverse axial displacement around the 4th intercostal space. In some cases, significant transverse axial displacement may be defined as a displacement greater than 10 degrees.

[0217] Significant lateral axial deviation around the fourth intercostal space may indicate the tracheal carina and passage of the catheter into the right or left mainstem bronchus (usually at the level of the fourth thoracic vertebra, which is in line with the sternal angle but may rise to two vertebrae above or below during respiration).

[0218] ..Locating the path of an inserted catheter, such as an inserted nasogastric tube, can avoid ambiguity. If a catheter is mistakenly placed in the lung when it was intended to be placed in the stomach, the final tip position of the incorrectly placed catheter can be very close to the correct position in the stomach. However, determining the path can show that the catheter was inserted through the wrong path, such as through the airway into the lung. If the path of the catheter is essentially straight, it can be clearly seen that the left or right main bronchus in the lung has not made a turn and the catheter has gone straight down the esophagus.

[0219] In the above-described embodiments, light is emitted from the catheter tip to dynamically observe the path.

[0220] In other embodiments, a point along the length of the catheter is imaged simultaneously with light emitted from multiple discrete points along the length of the catheter (e.g., as described above with reference to Figures 1 to 4 In other embodiments, the light is emitted uniformly along the length of the conduit.

[0221] In some embodiments, an internal optical fiber (or a group of optical fibers) is encased in the wall of the catheter. The optical fiber can be formed of glass or plastic.

[0222] In other embodiments, one or more optical fibers are fed down the catheter.The one or more optical fibers may be formed of glass or plastic.

[0223] In some embodiments, the optical fiber is fed down the catheter in specific known incremental steps to map the path of the catheter. The optical fiber can be fed down the catheter while the catheter is in place, such as in the esophagus of a patient. Feeding the optical fiber in known steps can be accomplished using, for example, a graduated electric clamp placed on top of the catheter.

[0224] At each step, the position of the fiber tip is determined using the light emitted from the fiber tip. As described above, the various determined tip positions are used to determine the path of the catheter.

[0225] The imaging may be dynamic. The imaging may be captured such that external anatomical landmarks may be digitally overlaid on the path and tip of the enteral feeding tube. The external anatomical landmarks may include, for example, at least one of the nipple, umbilicus, torso, sternum, upper abdominal region.

[0226] Anatomical triangulation can be used for digitally generated images.A limited number of known anatomical features (eg, anatomical landmarks or external anatomical markers) can be used to mark anatomical structures within the image.

[0227] Imaging of one or more light spots and determination of the position of the catheter can be performed in many situations where desired. Use of the above-described methods can allow proximal withdrawal of a placed catheter and repositioning in situ. For example, pulsed light can be injected into one or more optical fibers of a catheter, wherein the catheter is withdrawn and / or repositioned. Some currently used methods may not be able to determine the catheter position during withdrawal and / or repositioning. For example, conventional medical device positioning may not be performed continuously or repeatedly by X-ray during repositioning because the resulting exposure to ionizing radiation may be unacceptable.

[0228] The above embodiments may describe methods for NG tube insertion and monitoring, such as monitoring prior to daily feedings. The position of the NG tube may be checked during insertion. The position of the tube may be checked prior to each feeding.

[0229] In other embodiments, a similar approach can be taken for any enteral feeding or catheter solution with customized anatomical considerations and external overlaps. For example, the method can be used to place a tube into the trachea and ensure that the tube into the trachea does not move. The method can be used to place an umbilical vein catheter in a newborn. The method can be used to place a central venous line.

[0230] The above-described methods and systems may help reduce misplaced enteral feeding tubes, particularly nasogastric (NG) tubes.

[0231] The method may be particularly meaningful, for example, in frail patients. X-raying of frail patients may be difficult. Positioning the patient may be difficult. The method may be meaningful when the use of ionizing radiation is to be avoided, for example in children.

[0232] In some cases, reinsertion of a nasogastric tube may not be desirable, for example due to difficulty in insertion. The method may be used, for example, to ensure that the position of a NG tube does not change after gastrointestinal surgery.

[0233] In the above embodiments, at least one light emitting region of at least one optical fiber is used to determine the position or path of the medical device. In other embodiments, the or each optical fiber can be replaced with any suitable waveguide. The waveguide can include any suitable elongated structure configured to guide light. The waveguide can be flexible. For example, the waveguide can be configured to bend with the bending of the medical device and / or navigate through the channel of the medical device.

[0234] Reference now Figure 5 and 6 An example of photon transport from the lung and stomach in a relevant size model is discussed. Figure 5 and 6 is a diagram showing time-resolved photon detection of light transmitted from a device placed throughout a pig carcass (pig cadaver).

[0235] A fiber optic integrated test probe is placed in a pig carcass. The fiber optic integrated test probe includes a fiber optic device having one or more light emitting areas as described above. In the example shown, the fiber optic integrated test probe includes one or more individual optical fibers packaged as a single device. A 1 mm plastic sheath contains one or more 200 micron core fibers. Up to 5 fibers are placed in one sheath. The plastic sheath can be formed of PTFE or Pebax (polyether block amide). It is expected that much smaller fibers can be used in embodiments.

[0236] The distal end of each optical fiber is coated with a coating to produce substantially uniform light emission in all directions. In this example, the coating comprises titanium oxide powder mixed with epoxy glue.

[0237] Multiple fibers may be placed so that the locations of the fiber ends are spaced at 1 cm intervals along the length of the test probe. In other examples, the fibers may be placed at intervals of up to 4 cm.

[0238] The fiber-optic integrated test probe was intentionally placed in the lung of a porcine cadaver via bronchoscope. The fiber-optic integrated test probe was placed in the lung to simulate misplacement of a feeding tube. As mentioned above, if a feeding tube is misplaced during insertion, it may enter the lung.

[0239] A CT scanner was used to provide images of the pig cadaver with the fiber-optic integrated test probe in place to confirm device positioning in the lung.

[0240] Pulsed light is transmitted to the proximal end of the fiber-optic integrated test probe. In the example shown, the pulsed light source is a laser source. A laser repetition rate of 80 MHz is used, providing a measurement window of 12.5 nanoseconds. The pulses used have a duration of less than 1 nanosecond or less than 100 picoseconds. The power is less than 10 mW or less than 1 mW.

[0241] By individually illuminating each discrete fiber in turn, light is sequentially emitted from one or more light emitting regions. Photons are observed to leave the tissue of a porcine cadaver. Photons exiting the tissue are detected and analyzed to provide the location of a fiber optic integrated test probe.

[0242] Figure 5 Shown is the time-resolved photon detection of light emitted from a fiber-optic integrated test probe located in the lung, which has traveled through the tissue structure of a pig cadaver to the exterior of the cadaver. Figure 5 The normalized photon counts for each of the multiple image pixels are shown ( Figure 5 The gray lines 60 in the figure can be considered Figure 5 Each line 60 on the graph represents a record of the arrival time of a photon at a respective image pixel. An example of the arrival time of a photon at one image pixel of the detector is highlighted in black, as shown in FIG. Figure 5 Line 62.

[0243] The fiber-optic integrated test probe was also intentionally placed in the stomach of a porcine cadaver via a nasogastric tube. The fiber-optic integrated test probe was placed in the stomach to simulate proper positioning of a feeding tube.

[0244] A CT scanner is used to provide an image of a pig carcass with the fiber-optic integrated test probe in place to confirm that the device is positioned in the stomach. Pulsed light is transmitted to the proximal end of the fiber-optic integrated test probe, for example, where the fiber-optic integrated test probe is located in the lung, using a light source and parameters as described above. Light is sequentially emitted from one or more light-emitting areas by irradiating each discrete fiber individually in turn. Photons are observed to leave the tissue. Photons leaving the tissue are detected and analyzed to provide the location of the fiber-optic integrated test probe.

[0245] Figure 6 Shown is the time-resolved photon detection of light emitted from a fiber-optic integrated test probe located in the stomach, which has traveled through the tissue structure of a pig carcass to the exterior of the carcass. Figure 6 The normalized photon counts for each of the multiple image pixels are shown ( Figure 6 The gray lines 70 in the figure can be considered Figure 5 Each line 70 on the graph represents a record of the arrival time of a photon at a respective image pixel. An example of the arrival time of a photon at one image pixel of the detector is highlighted in black, as shown in FIG. Figure 6 Line 72.

[0246] It can be seen that the photon arrival times ( Figure 6 ) is different from the photon arrival time across the detector pixels when the fiber-optic integrated test probe is placed in the lung ( Figure 5 ). The photon arrival time can be used to distinguish different positions of the fiber-optic integrated test probe.

[0247] Although specific embodiments are described above, features of any embodiment may be combined with features of any other embodiment. For example, features of an embodiment in which light is transmitted from a medical device may be combined with features of an embodiment in which light is received by the medical device. Features of any different of the medical devices may be combined. Features described in the context of the intestine may be applied to any other anatomical structure (and vice versa).

[0248] It will be appreciated that the present invention has been described above by way of example only and that modifications of detail may be made within the scope of the invention.

[0249] Each feature disclosed in the description and (where appropriate) the claims and drawings may be provided independently or in any appropriate combination.

Claims

1. A system for determining a path of at least a portion of an elongated medical device within a scattering medium, the system comprising: an elongated medical device configured to be located at least partially within a scattering medium forming at least a portion of a body of a human or animal subject, the elongated medical device comprising at least one optical fiber or other waveguide having a plurality of light emitting regions arranged along a longitudinal dimension of at least a portion of the elongated medical device; a pulsed light source configured to transmit pulsed light to a proximal end of the at least one optical fiber or other waveguide such that the pulsed light is guided along the at least one optical fiber or other waveguide to the light emitting region and emitted outwardly from the medical device by the light emitting region into the scattering medium; at least one single-photon detector configured to receive photons of the pulsed light that have passed through the scattering medium, wherein the detector is configured to generate electrical signals in response to receiving the photons, the generated electrical signals comprising electrical signals corresponding to ballistic photons that pass through the scattering medium without scattering and scattered photons that are scattered by the scattering medium; as well as A processor configured to: selecting some of the generated electrical signals corresponding to some of the received photons based at least on arrival times of the received photons at at least one detector, wherein the arrival time of each photon comprises a difference between a time when the photon is received at the at least one detector and a time when the pulsed light source emits the pulsed light, wherein the selection of the signals comprises selecting signals whose arrival times are within a certain time interval; determining a respective position of each light emitting region based on the selected signal; and determining a path of at least a portion of the elongated medical device within the body of the human or animal subject based on the determined position; Wherein determining the position of each light emitting area based on the selected signal comprises: forming at least one image using the selected signal, and determining the position of each light emitting area based on the at least one image.

2. The system of claim 1 , wherein selecting the signal comprises: selecting a first set of signals having arrival times within a first time interval; selecting a second set of signals having arrival times within a second time interval; and The first set of signals is compared to the second set of signals. 3 . The system of claim 1 , wherein the at least one image includes a respective image of each light-emitting region, and determining the position of each light-emitting region is based on the image of the light-emitting region.

4. The system of claim 1 , wherein determining the path of at least a portion of the elongated medical device comprises applying a shape-based image processing technique using an expected shape of the elongated medical device and / or an expected shape of the at least one optical fiber or other waveguide.

5. The system of claim 1, wherein the processor is further configured to compare the determined position of the elongated medical device to an expected anatomical structure of the human or animal subject.

6. A system according to claim 5, wherein comparing the position of the medical device to the expected anatomical structure of the subject includes determining the position of the medical device relative to at least one of: the subject's esophagus, the subject's bronchus, the subject's pyloric plane, the subject's intercostal space, the subject's vertebrae.

7. The system of claim 1, wherein the light emitting regions are regularly spaced along a length of at least a portion of the at least one optical fiber or other waveguide.

8. The system of claim 1, wherein the at least one optical fiber comprises a plurality of optical fibers, and each light emitting region comprises a tip of a respective one of the plurality of optical fibers.

9. The system of claim 1, wherein each light emitting region is configured to transmit and / or scatter light of a different wavelength.

10. The system of claim 1, wherein each light emitting region comprises at least one of a long period fiber Bragg grating, a tilted fiber Bragg grating, and a core damaged region.

11. The system of claim 1 , wherein transmitting the pulsed light to the scattering medium comprises individually illuminating each light emitting region in turn.

12. The system of claim 1, wherein the elongated medical device comprises an endoscope.

13. The system of claim 1, wherein the elongated medical device comprises a tube.

14. The system of claim 13, wherein the optical fiber or other waveguide is located within the lumen of the tube.

15. The system of claim 13, wherein the optical fiber or other waveguide is integrated into the tube material of the tube.

16. A computer program product comprising computer readable instructions executable by a processor to select signals corresponding to received photons of pulsed light that have passed through a scattering medium forming at least a portion of a body of a human or animal subject to determine a respective position of each of a plurality of light emitting regions based on the selected signals, wherein determining the position of each light emitting region based on the selected signals comprises: At least one image is formed using the selected signals, and the position of each light-emitting area is determined based on the at least one image, wherein the light-emitting areas are arranged along the longitudinal dimension of at least a portion of the slender medical device, and the path of the slender medical device within the body of the human or animal subject is determined based on the determined positions, wherein the photons are received by at least one single-photon detector, and the at least one single-photon detector is configured to receive photons of pulsed light that have passed through the scattering medium and generate an electrical signal corresponding to each received photon, wherein the generated electrical signal includes electrical signals corresponding to received ballistic photons and scattered photons, and wherein selection of signals is based at least on arrival time of the received photons at the at least one single-photon detector, wherein the arrival time of each photon includes the difference between the time when the photon is received at the at least one detector and the time when the pulsed light source emits a light pulse, and wherein selection of signals includes selecting signals whose arrival times are within a certain time interval.

17. A system for determining a path of at least a portion of an elongated medical device within a scattering medium, the system comprising: an elongated medical device configured to be located at least partially within a scattering medium forming at least a portion of a body of a human or animal subject, the elongated medical device comprising at least one optical fiber or other waveguide having a plurality of light receiving regions arranged along a longitudinal dimension of at least a portion of the elongated medical device; a pulse light source configured to be located outside the scattering medium and transmit pulse light into the scattering medium; at least one single-photon detector coupled to a proximal end of the at least one optical fiber or other waveguide, wherein the at least one detector is configured to receive photons of the pulsed light that have passed through the scattering medium and have been received by a light receiving region and guided along the at least one optical fiber or other waveguide to the at least one detector, wherein the detector is configured to generate an electrical signal in response to receiving the photons, the generated electrical signal comprising electrical signals corresponding to ballistic photons that pass through the scattering medium without scattering and scattered photons that are scattered by the scattering medium; as well as a processor configured to: select some of the generated signals corresponding to some of the received photons based at least on a time of arrival of the received photons at at least one detector, wherein the time of arrival of each photon comprises a difference between a time when the photon is received at the at least one detector and a time when the pulsed light source emits the pulsed light, wherein the selection of the signals comprises selecting signals having arrival times within a time interval; determine a respective position of each of the regions where the light was received based on the selected signals; and determine a path of at least a portion of the elongated medical device within the body of the human or animal subject based on the determined positions; Wherein determining the position of each light emitting area based on the selected signal comprises: forming at least one image using the selected signal, and determining the position of each light emitting area based on the at least one image.

18. The system of claim 17, wherein transmitting the pulsed light to the scattering medium comprises changing a position of the light source relative to the scattering medium and / or changing an incident position of the pulsed light from the light source on the scattering medium.

19. A system for determining the position of an intestinal tract located within a scattering medium, the system comprising: a bowel configured to be located at least partially within a scattering medium forming at least a portion of a body of a human or animal subject, wherein the bowel comprises or at least partially contains at least one optical fiber or other waveguide, the at least one optical fiber or other waveguide comprising at least one light emitting region; a pulsed light source configured to transmit pulsed light to the proximal end of the at least one optical fiber or other waveguide so that the pulsed light is guided along the at least one optical fiber or other waveguide to the one or more light emitting regions and emitted outwardly from the intestinal tract into the body of the subject by the one or more light emitting regions; at least one single-photon detector configured to receive photons of the pulsed light that have passed through the subject's body, wherein the detector is configured to generate electrical signals in response to receiving the photons, the generated electrical signals including electrical signals corresponding to ballistic photons that pass through the scattering medium without scattering and scattered photons that are scattered by the scattering medium; as well as A processor configured to: selecting some of the generated signals corresponding to some of the received photons based at least on arrival times of the received photons at at least one detector, wherein the arrival time of each photon comprises a difference between a time when the photon is received at the at least one detector and a time when the pulsed light source emits the pulsed light, wherein the selection of the signals comprises selecting signals whose arrival times are within a time interval; determining a position of each light emitting region based on the selected signal; and determining a location of the intestine within the body of the human or animal subject based on the determined one or more locations; Wherein determining the position of each light emitting area based on the selected signal comprises: forming at least one image using the selected signal, and determining the position of each light emitting area based on the at least one image.

Images