Methods for analyzing and displaying OCT signals

Abstract

The present invention relates to a method for analyzing and displaying OCT signals (19), which comprises determining (S100) acquired OCT signals (19) of a selected field of view (66) of an anatomical structure (65), wherein the OCT signals (19) comprise a plurality of A-scans along a depth direction of the anatomical structure (65). Furthermore, the method comprises segmenting (S200) anatomical substructures (63, 64) along the depth direction of the anatomical structure (65) in the plurality of A-scans and determining (S300) distances (1, 2) between a segmented first anatomical substructure (63) and a segmented second anatomical substructure (64) in the plurality of A-scans along the depth direction.As further steps, the method comprises determining (S400) a two-dimensional representation (31) of the selected field of view (66) based on the acquired OCT signals (19) and the determined distances (1, 2), and outputting (S500) the two-dimensional representation (31) on a display means (30). The invention further relates to a system (100) for analyzing and displaying OCT signals (19), comprising a display means (30) designed for the time-resolved display of at least two-dimensional representations and images, and a control unit (40) configured to execute the method according to the invention.

Description

The present invention relates to a method for the analysis and display of OCT signals of the eye, for example for the analysis and visualization of time-resolved OCT signals in the form of time-resolved OCT images, wherein the visualized OCT signals are displayed superimposed with the results of the analysis of the OCT signals. The present invention further relates to a system for analyzing and visualizing OCT signals.Technological BackgroundThe use of technological auxiliaries is a constituent of modern medicine. Both imaging methods and robotic systems are now used in surgery as well as in diagnostics, of course. The use of imaging methods allows the representation and discrimination of a variety of structures in the patient and the image data obtained from the patient can be used advantageously in diagnostics as well as in therapeutic and surgical methods.For example, an operator can better plan a surgical procedure on the basis of image data of a patient and can also be assisted in carrying out the procedure. Robotic visualization systems are used to aid surgeons in performing surgical procedures. These usually have at least one camera for recording images of the region to be operated on, which is carried by a stand having a joint structure. The stand allows the camera to be positioned relative to the subject by translation and / or rotational movements to capture images of a desired field of view (FOV) of the area to be operated. The use of optical stereo cameras makes it possible to capture 3D image data.In addition to the acquisition of surface information of a desired field of view, for example on the basis of reflected or backscattered visible light, methods for acquiring depth information of the field of view also exist in the meantime. These methods comprise optical coherence tomography (OCT), which allows three-dimensional microscopic imaging of optically transparent and / or reflecting objects and thus the recording of volume images of the biological tissue in the field of view under consideration. Optical coherence tomography (OCT) is essentially an interferometric method using broadband light with a short coherence length. Systems for acquiring OCT data therefore generally have an interferometer and a broadband light source with a spectral width of more than 1% of the central wavelength.The acquisition of OCT data can be performed sequentially or in parallel. The sequential acquisition of OCT data takes place, for example, by splitting a low-coherence source light beam at a beam splitter into a sample beam and a reference beam, which are sent through two arms of an interferometer, wherein a movable reference mirror is arranged in the reference beam path and the object to be examined is arranged in the object beam path. By displacing the reference mirror, a path difference between object beam and reference beam and thus the measured depth can be adjusted. By means of a mirror in the object beam path, the object beam is scanned two-dimensionally over the sample, which as a result enables a three-dimensional scanning of the sample.In such a time domain OCT (TD OCT) data acquisition, the spectral width of the light source Δλ corresponds to a coherence length L C of L C= λ* / Δλ. The axial resolution of an OCT system corresponds to the coherence length L C of the light used and denotes the resolution capability of objects which have a distance along the optical axis of at least the coherence length. For example, a light source in the near infrared range with a central wavelength of 800 nm and a spectral width of 80 nm has a coherence length of 7 μm and an OCT system with such a source thus has an axial resolution of approximately 1-10 μm. The transverse resolution of an OCT system is determined by the optics used in the object beam path, in particular by the object lens focusing the light onto the object to be examined.Sequential acquisition of OCT data is also possible in the frequency domain (frequency domain OCT-FD OCT), wherein a distinction is generally made between the use of a tunable source (swept source OCT) and the use of a dispersive detector (spectral domain OCT-SD OCT). In the swept source OCT, the frequency of the excitation light source, for example a laser, is tuned, as a result of which a path difference between the sample beam and the reference beam and thus the scanned sample depth can be varied even without a displaceable reference mirror. In SD OCT, a wide band light source is also used, but the frequency components of the interference signal are separated before detection, for example by an optical grating.By means of OCT, slice and volume data of biological tissue can be detected and the information content for an operator can be clearly increased. Thus, integration of OCT in surgical microscopes is desirable in order to be able to represent video data of the surface of a desired field of view as well as depth and / or sectional images of the field of view, for example simultaneously and / or superimposed. However, the combined display of intraoperative OCT imaging and conventional (3D) imaging in surgical microscopes is complex and presents new challenges to the operator. Insofar as operating systems have hitherto been able to deliver volumetric OCT images, their recording time is relatively high and rendering is additionally restricted solely to post-processing for reasons of time and resources. Volume imaging in real time during the operation has therefore not been possible up to now.However, with further advances in OCT technology, as well as the capacity and speed of graphics processing processors (GPUs), faster OCT methods become available for intraoperative imaging. However, the display of OCT volume images in real time that is possible as a result can disadvantageously lead to an overrequest or distraction of the operator, in particular if OCT and conventional video data are displayed on different screens or different screen regions or a switching between the modalities is not readily possible.In addition, by means of OCT imaging, different structures of the human eye cannot be visualized or can only be visualized poorly before or during a surgical procedure. For example, regions below a medical instrument are generally completely shaded and a 2D plan view ("en face" view) is produced from OCT data as a rule by accumulation of signal intensities along the scanning direction of at least one A scan. Defects or voids in the fabric are thus not visualizable, in particular if the OCT scan range exceeds an overall thickness of the fabric. Ophthalmic Visual Devices (OVDs), which are frequently used in eye surgery, for example in order to maintain the volume and shape of the anterior chamber of the eye and to protect the intraocular tissue, are generally not recognizable in an OCT "en face" view, since these are clear gel-like materials which cannot contribute to the calculated signal intensity along the scanning direction of an A scan.The object of the present invention is therefore to provide an improved method and an improved system for analyzing and visualizing OCT signals, which overcomes or at least reduces the disadvantages of the prior art and increases the information content of OCT images for an operator in an application-specific manner.DESCRIPTION OF THE INVENTIONThe object according to the invention is achieved by the subject matter of the independent claims. Preferred refinements are the subject matter of dependent claims which refer back.A first aspect of the present disclosure relates to a method for the analysis and representation of OCT signals, preferably of OCT signals of an OCT system integrated into a medical device. The medical device is, for example, a surgical microscope. The medical device is preferably designed for multimodal image acquisition and image display, in particular for acquisition of OCT signals and image signals.In a first step of the method according to the present disclosure, acquired OCT signals of a selected field of view of an anatomical structure are ascertained. The anatomical structure is, for example, an operating area of a patient, and ophthalmological operations are, in particular, an eye. However, the anatomical structure can also be any other surgical areas, such as, for example, brain tissue in neurosurgery, tissue located in the HNO region in HNO surgery or gums, calculi or dental nerves in dental surgery. It can also be any other tissue or preparation (in vivo, in vitro or in situ). The selected field of view is preferably the region of interest (Rol) to be examined which has the part of the anatomical structure to be examined.The determination preferably comprises a reading of the OCT signals from a received message and / or from a memory. Furthermore, the method preferably comprises, as a further step, a detection of the OCT signals. The OCT signals are preferably acquired by generating a light signal and partially guiding it as a sample beam onto the selected field of view of the anatomical structure by means of an interferometer of the OCT system and then superimposing it in the interferometer with a reference beam likewise generated from the light signal in order to generate an interference pattern. The OCT signal is preferably an interference signal, wherein the modulation of the envelope of the interference signal encodes reflection or scattering properties of the anatomical structure / sub-structures. By means of a scanning mechanism, a selected field of view of a sample can be scanned two-dimensionally at a depth set via the path difference of reference beam and sample beam. The OCT signal therefore encodes information about the selected field of view of the anatomical structure, on the basis of which a time-resolved OCT image can be generated mathematically, for example by means of volume rendering, ray tracing and / or ray marching. Methods for generating OCT images from OCT signals are known to the person skilled in the art.The OCT signals comprise a plurality of A-scans along a depth direction of the anatomical structure. An A-scan, in the sense of this disclosure, is preferably a signal scanned at a single scanning point along the depth direction (the optical axis). The A-scan therefore shows the reflection profile of the anatomical structure in the depth direction. If A scans are carried out on several or all scan points along a line, this is referred to as a B scan or line scan. A B-scan shows in particular a reflection profile of a section through the anatomical structure in the depth direction. The plurality of A-scans preferably has a plurality of B-scans along a scanning direction, wherein scanning directions of the plurality of B-scans are each shifted with respect to one another in a lateral direction. In other words, the OCT signals preferably have a volume scan (C-scan) over part or the entire volume of the selected field of view.In a further step of the method, a segmenting of anatomical sub-structures along the depth direction of the anatomical structure takes place in the plurality of A scans. In other words, in this step, a plurality of anatomical sub-structures are identified within the anatomical structure, in particular in a plurality of the plurality of A-scans. The segmenting is preferably carried out on the basis of the reflection or scattering properties of the anatomical sub-structures in the plurality of A scans of the OCT signals. Likewise preferably, at least one OCT image is created based on the OCT signals and the segmenting is carried out on the basis of the at least one OCT image. Various algorithms are known to those skilled in the art for automatically segmenting objects into image data and these algorithms are used in the present case to determine anatomical sub-structures. These algorithms include traditional threshold based image processing algorithms, edge detection algorithms such as Canny, Sobel, and Roberts, which can be used to detect boundaries between different regions in the image, as well as newer machine learning based 2D and 3D segmentation networks (e.g., a U-net segmentation network).The method comprises as a further step determining distances between a segmented first anatomical substructure and a segmented second anatomical substructure in the plurality of A-scans along the depth direction. In other words, for each A-scan, which has a part of the segmented first anatomical substructure and a part of the segmented second anatomical substructure, the distance between the two sub-structures is determined. This preferably includes identifying the at least two sub-structures in at least some of the A-scans, which can also be carried out, for example, taking into account A-sacns at adjacent scan points. A correlation of A-scans of adjacent A-scans enables, for example, the determination of contiguous anatomical sub-structures.In a further step of the method, a two-dimensional representation of the selected field of view is determined on the basis of the detected OCT signals and the determined distances. The two-dimensional representation is preferably determined as a plan view ("en face") of the selected field of view. The two-dimensional representation preferably has markings of the distances determined. A point of the two-dimensional representation is preferably marked on the basis of the distance which was determined in the associated A scan, i.e. one which was carried out at this point in the depth direction.As a further step, the method comprises outputting the two-dimensional representation on a display means.Advantageously, localized information about distances between anatomical sub-structures can be clearly shown with the method according to the invention, which information can be advantageously used in particular for diagnostic, monitoring and operation planning purposes.In a preferred embodiment of the method, an intensity of the OCT signals between the first anatomical substructure and the second anatomical substructure falls below a first predetermined limit value. Preferably, the method comprises, as a further step, a comparison of the intensity of the OCT signals between the first anatomical substructure and the second anatomical substructure with a first predetermined limit value, wherein the distances are determined only when the intensity falls below the first predetermined limit value. The first limit value is preferably predetermined such that it is at the lowest intensity which would still have assumed human tissue when the OCT signal was analyzed. In other words, distances are calculated only when a gas- and / or liquid-filled cavity is located between the anatomical sub-structures. The distances are preferably determined only when the intensity of the OCT signals between the first anatomical substructure and the second anatomical substructure is zero. The distances are thus determined in particular as regions without an OCT signal between slice boundaries of two different anatomical sub-structures, in particular sub-structures adjoining one another.According to this embodiment, advantageously localized information about cavities between anatomical sub-structures can thus be clearly shown, which can be used advantageously in particular for diagnostic, monitoring and operation planning purposes.In a further preferred embodiment of the method, an ophthalmic visual device, OVD, is located between the first anatomical substructure ( 63) and the second anatomical substructure ( 64). The method in this embodiment is thus preferably used during an intervention in which OVDs are used, such as, for example, in cataract, corneal, glaucoma, eye trauma and / or vitreoretinal surgery. OVDs are a class of clear gel-like materials used in eye surgery to preserve the volume and shape of the anterior chamber of the eye and to protect the intraocular tissue, particularly the corneal endothelium, during surgery, for example from mechanical trauma. The consistency of the OVD makes them passable for surgical instruments, at the same time OVDs do not flow under low shear stress and maintain their shape, so that collapse of the anterior chamber is prevented. The preferred embodiment of the method according to the invention advantageously makes it possible to detect the dimensions and the position of an introduced OVD and thus optionally to detect and / or compensate for incorrect positioning and / or an OVD excess or deficiency. After an operation using an OVD, it must generally be completely removed, since OVDs can cause excessive postoperative intraocular pressure, in particular if a residue remains in the eye after the operation. By means of the method in the preferred embodiment described here, it is advantageously possible to detect the residueless removal of the OVD.In a further preferred embodiment, the anatomical structure comprises a front eye section, the first anatomical substructure comprises a cornea and the second anatomical substructure comprises a transplant structure, an iris and / or a conjunctiva. In other words, distances in the anterior eye section between the cornea and the transplant structure, between the cornea and the iris and / or between the cornea and the conjunctiva are preferably determined and output as a two-dimensional representation. Thus, the method can be advantageously carried out on an eye in order to detect delamination of a membrane transplant, for example during or after a Descemet Membrane Endothelial Keratoplasty (DMEK), or fluid-filled cavities, for example during or after a trabeculectomy.Particularly preferably, distances between the cornea and the iris are determined in the method, in particular if the method is used during an intervention in which OVDs are used, such as, for example, in cataract, cornea, glaucoma, eye trauma and / or vitreoretinal surgery. The preferred embodiment thus advantageously makes it possible to detect the dimensions and the position of an introduced OVD between the cornea and the iris and thus to detect and / or compensate, if appropriate, for an incorrect positioning and / or an OVD excess or deficiency. It is also advantageously possible to detect the complete removal of the OVD, for example between iris and cerebral skin.In a further preferred embodiment, the method comprises, as a further step, a time-resolved image signal of the selected field of view of the anatomical structure being acquired by means of at least one image sensor. The time-resolved image signal is preferably a multiplicity of signals assigned to surface elements of the anatomical structure, which signals are captured sequentially or simultaneously for a specific grid of the surface of the anatomical structure, wherein the grid is determined by a scanning mechanism and / or the image sensor. The time-resolved image signal furthermore preferably has a clock frequency (image repetition rate) which is determined by a scanning mechanism and / or the image sensor.As a further step, the preferred embodiment comprises determining a two-dimensional image of the selected field of view from the time-resolved image signal. Preferably, image data corresponding to the captured time-resolved image signal is determined and a two-dimensional image is generated therefrom. Furthermore, preferably, video image data with a raster (resolution) and an image repetition rate are generated from the time-resolved image signal, which video image data are suitable for display on the display means. The two-dimensional image is preferably generated such that the generated two-dimensional representation corresponds at least to a section of the generated two-dimensional image.In a further step, the two-dimensional image is preferably displayed together with the two-dimensional display on the display means. Preferably, the two-dimensional representation is displayed at the position of the corresponding section of the two-dimensional image on the display means. In other words, the data of the two-dimensional representation and of the two-dimensional image corresponding to the same section of the selected field of view are displayed at the same location of the display means.A likewise preferred embodiment of the method provides that the at least one image sensor is part of an operation microscopic system.The likewise preferred embodiment comprises, as a further step, registering the time-resolved image signal and the OCT signals on the basis of detection parameters of the OCT system and of the surgical microscope system.A registration of the OCT signals and the time-resolved image signal thereby denotes a correct linking of these signals to a reference coordinate system, for example the coordinate system of the patient during an intervention, and enables a clear mapping (mapping) of coordinates of the patient space to corresponding coordinates of the signal space. Thus, the data of the two-dimensional display and of the two-dimensional image can be displayed on the display means in a particularly simple manner superimposed on one another, in particular with correct relative positions with respect to one another, since they are linked to the same coordinate system.Registration of the signals preferably requires calibration of the OCT system. The acquisition parameters of the OCT system preferably comprise calibration parameters. The detection parameters of the OCT system preferably take account of the scanning mechanism and / or the detector of the OCT system.Registration of the image signal preferably requires calibration of the surgical microscope system. The acquisition parameters of the surgical microscope system thus preferably comprise calibration parameters and / or optical settings of the surgical microscope system, such as, for example, a focal length and / or a zoom stage of an optical unit (camera) used. In addition, the acquisition parameters preferably also comprise a set of intrinsic parameters of the surgical microscope system. The intrinsic parameters determine a relationship between the coordinate system of an image signal and the coordinate system of the associated imaging sensor. The type of intrinsic parameters depends in particular on the type of imaging sensor used, wherein the imaging sensor here denotes both the actual sensor and the optical system used. The intrinsic parameters comprise, for example, an effective focal length in a camera calibration according to Tsai, the coordinates of an image main point (center of distortion) of an image signal, a first scaling factor and / or a first radial lens error coefficient (distortion coefficient). Alternatively to the aforementioned intrinsic parameters, other intrinsic parameters can also be used, for example for a camera calibration according to Zhang (cf., for example, "A practical comparison between Zhang's and Tsai's calibration approaches", Li et al., Proceedings of the 29th International Conference on Image and Vision Computing New Zealand, November 2014 Pages 166-171, DOI:10.1145 / 2683405.2683443).Alternatively or additionally, the two-dimensional image and the two-dimensional representation are preferably registered by means of image analysis. For example, structure or tissue boundaries in the two-dimensional image and the two-dimensional representation can be recognized and compared with one another by means of image analysis, for example edge recognition or the like. By means of translatory displacement, rotation and / or scaling, these structures can then be brought into superposition with one another on the display means.The preferred execution forms described above thus enable seamless integration of image data and cavity display on the display means, thereby enabling a user to view the multimodal image data more easily. Thus, the multimodal image data can be viewed without moving the head or the eyes, which has an advantageous effect on the attention of the operator, in particular during imaging during surgical interventions. A further advantage is that the information from the two-dimensional representation can be communicated to the user in a particularly illustrative manner, since he can easily identify on the display means which part of the surface of the eye is under which cavities are located. It is also conceivable to superimpose the two-dimensional representation directly on the selected field of view, for example by projecting the two-dimensional representation onto the surface of the anatomical structure.A further preferred embodiment of the method comprises, as a further step, determining, for each A-scan, whether the distance between the first anatomical substructure and the second anatomical substructure determined therein exceeds a second predetermined limit value. In other words, each determined distance is compared with the second predetermined limit value and in this case in each case it is determined whether the determined distance is greater than the second predetermined limit value.In a further step, the two-dimensional representation of the selected field of view is then determined in such a way that a distance indicator is displayed for each A scan in which the determined distance exceeds the second predetermined limit value. Preferably, a pixel of the two-dimensional representation is created for each surface coordinate from which an A scan has been carried out in the depth direction, wherein the pixel preferably has a distance indicator, such as a predetermined color, if the second predetermined limit value has been exceeded. Thus, on the basis of the two-dimensional representation, the planar extent and position of a cavity below the surface can advantageously be detected without any circumstances.In a particularly preferred embodiment, the second predetermined limit value corresponds to the desired (upper limit of a) thickness of an OVD or the desired (upper limit of a) total thickness of an OVD and a aqueous chamber. In this embodiment, it is particularly preferably also determined for each A-scan whether the distance between the first anatomical substructure and the second anatomical substructure determined therein falls below a third predetermined limit value. The interval between the second predetermined limit value and the third predetermined limit value preferably corresponds to an optimum range for a thickness of an OVD or a total thickness of an OVD and a aqueous chamber. Furthermore, the two-dimensional representation of the selected field of view is preferably determined in such a way that for each A-scan in which the determined distance falls below the third predetermined limit value, a distance indicator is displayed, particularly preferably a second distance indicator, which has a second color, for example. Preferably, if the second limit value is exceeded, a warning about an OVD excess and / or if the third limit value is undershot, a warning about an OVD deficiency is additionally output on the display means, for example in text form or by means of a warning symbol. Thus, on the basis of the two-dimensional representation, an OVD excess or OVD deficiency can advantageously be recognized without any circumstances.A further preferred embodiment provides that for each A-scan an absolute value of the distance between the first anatomical substructure and the second anatomical substructure determined therein is determined. The two-dimensional representation of the selected field of view is preferably determined in such a way that distance indicators corresponding to the determined absolute values are displayed. Preferably, a pixel of the two-dimensional representation is created for each surface coordinate from which an A scan was carried out in the depth direction, wherein the pixel preferably has a distance indicator corresponding to the determined absolute value. The distance indicator is preferably a color which corresponds to the determined absolute value from a continuous color profile which is assigned to the value range of the distance values. Preferably, the distance indicator is only displayed if the second predetermined limit value has been exceeded. Thus, on the basis of the two-dimensional representation, the volumetric extent and position of a cavity below the surface can advantageously be detected without any circumstances.In a further preferred embodiment, for each A-scan, a position of the distance determined therein along a depth direction of the anatomical structure is determined. The position of the determined distance is preferably the position of the center point or of another point within the determined distance. Alternatively preferably, the position of the determined distance is the position of an edge of the distance, i.e. in other words the position of the edge of the first anatomical substructure or of the second anatomical substructure. The position of the distance is preferably determined on the basis of a characteristic point of a surface of the anatomical structure, for example an apex. The determination of such a characteristic point optionally requires the execution of a plurality of line scans as described above. Likewise preferably, the position of the distance is determined relative to the surface of the anatomical structure and / or relative to the selected field of view.The two-dimensional representation of the selected field of view is preferably determined in such a way that for each A scan, a depth indicator corresponding to the determined position is displayed. Preferably, a pixel of the two-dimensional representation is created for each surface coordinate from which an A scan was carried out in the depth direction, wherein the pixel preferably has a depth indicator corresponding to the determined position. The depth indicator is preferably a color and / or a color intensity which corresponds to the determined position and was determined from a continuous or discrete color or color intensity profile which is assigned to the value range of the position values. Thus, on the basis of the two-dimensional representation, the position of a cavity below the surface in the depth direction can advantageously be detected without any circumstances.The display means is preferably designed to display stereoscopic images, integrated into smart glasses and / or integrated into the eyepiece of an surgical microscope system. This has the advantage that the information output on the display means can be easily and quickly detected by a user.In a likewise preferred embodiment, the method comprises controlling a medical instrument. The medical instrument is preferably robotic and designed for a tapping movement, an OVD being introduced and / or removed and / or a liquid being removed. The medical instrument is, for example, a probe, a pointer, a tweezer, a cannula, an ahl, a phako tip, an endoscope, an endo-LED or the like.The medical instrument is preferably controlled to the position of an A-scan for which a distance between the first anatomical substructure and the second anatomical substructure of greater than zero has been determined. The medical instrument is preferably controlled to the position of an A-scan for which a distance has been determined which is greater than the second predetermined limit value. The medical instrument is likewise preferably controlled to the position of an A-scan for which a distance has been determined which is less than the third predetermined limit value. Particularly preferably, the medical instrument is controlled to the determined position of the determined distance along the depth direction of the anatomical structure as described above.In this embodiment, the site in the anatomical structure that requires treatment can be advantageously determined with the method and, in addition, the instrument required for treatment can be guided directly to the determined site.Another aspect of the present disclosure relates to a system for analyzing and displaying OCT signals.The system according to the invention has a display means designed for the time-resolved display of at least two-dimensional representations and images. The display means is preferably one or more screens, for example at least one screen of a surgical microscope, a screen fixedly installed in a surgical room or a head-mounted display (HMD), for example smart glasses. The screen is preferably a 4K and / or 8K capable screen and / or a 3D screen configured for stereoscopic display.The system according to the present disclosure further comprises a control unit connected to the display means, in particular for one or two-way data transmission.The control unit is configured to receive OCT signals, preferably time-resolved OCT signals, of a selected field of view of an anatomical structure from an OCT system. The OCT signals comprise a plurality of A-scans along a depth direction of the anatomical structure. The OCT signals have preferably been detected by generating a light signal and partially guiding it as a sample beam onto the anatomical structure by means of the interferometer and then superimposing it in the interferometer with a reference beam likewise generated from the light signal in order to generate an interference pattern.The control unit is further configured to segment anatomical sub-structures along the depth direction of the anatomical structure in the plurality of A-scans. In other words, in this step, a plurality of anatomical sub-structures within the anatomical structure are categorized by the control unit. The segmenting is preferably carried out on the basis of the reflection or scattering properties of the anatomical sub-structures in the plurality of A scans of the OCT signals.The control unit is likewise preferably designed to generate at least one OCT image on the basis of the OCT signals and to carry out the segmenting on the basis of the at least one OCT image. Methods for generating OCT images from OCT signals are known to the person skilled in the art. Furthermore, various algorithms are known to the person skilled in the art for automatically segmenting objects into image data and these algorithms are used in the present case by the control unit in order to determine anatomical sub-structures. These algorithms include traditional threshold based image processing algorithms, edge detection algorithms such as Canny, Sobel, and Roberts, which can be used to detect boundaries between different regions in the image, as well as newer machine learning based 2D and 3D segmentation networks (e.g., a U-net segmentation network). The control unit is likewise preferably designed to take into account the sub-structures segmented in A-scans of an adjacent scan point when segmenting anatomical sub-structures along an A-scan, for example in order to check the continuity of a sub-structure. Thus, it can be advantageously avoided that non-identical anatomical sub-structures in different A-scans are erroneously segmented as a same sub-structure.Furthermore, the control unit is configured to determine distances along the depth direction between a segmented first anatomical substructure and a segmented second anatomical substructure in the plurality of A-scans. The control unit is preferably further configured to compare an intensity of the OCT signals between the first anatomical substructure and the second anatomical substructure with a first predetermined limit value, preferably a first predetermined limit value, as described above. The control unit is likewise preferably designed to determine the distances in each case only when the intensity falls below the first predetermined limit value.The control unit is further configured to determine a two-dimensional representation of the selected field of view on the basis of the received OCT signals and the determined distances. The control unit is preferably designed to ascertain the two-dimensional representation as a plan view ("en face") of the selected field of view, which has markings of the ascertained distances. In this case, the control unit preferably marks a point of the two-dimensional representation on the basis of the distance which was determined in the associated A-scan, that is to say that was carried out at this point in the depth direction.The control unit is preferably designed to determine for each A scan whether the distance between the first anatomical substructure and the second anatomical substructure determined therein exceeds a second predetermined limit value. Furthermore, the control unit is preferably designed to determine the two-dimensional representation of the selected field of view in such a way that a distance indicator is displayed for each A scan in which the determined distance exceeds the second predetermined limit value. Furthermore, the control unit is preferably designed to determine for each A scan whether the distance between the first anatomical substructure and the second anatomical substructure determined therein falls below a third predetermined limit value. Furthermore, the control unit is preferably designed to determine the two-dimensional representation of the selected field of view in such a way that the distance indicator or a second distance indicator is displayed for each A scan in which the determined distance falls below the third predetermined limit value. The control unit is likewise preferably designed to determine an absolute value of the distance between the first anatomical substructure and the second anatomical substructure determined therein for each A scan and to determine the two-dimensional representation of the selected field of view in such a way that distance indicators corresponding to the determined absolute values are displayed. Furthermore, the control unit is preferably designed to determine a position of the distance determined therein along a depth direction of the anatomical structure for each A-scan and to determine the two-dimensional representation of the selected field of view in such a way that a depth indicator corresponding to the determined position is displayed for each A-scan.Furthermore, the control unit is designed to output the two-dimensional representation on the display means. Thus, the system according to the invention can advantageously clearly show localized information about distances between anatomical sub-structures, which can be used advantageously in particular for diagnostic, monitoring and operation planning purposes.In a preferred embodiment, the system further comprises an OCT system. The control unit is preferably designed to control the OCT system for detecting a time-resolved OCT signal of the selected region of interest (ROI) of the anatomical structure, wherein the field of view is preferably selected by a user.The OCT system preferably has a broadband light source designed for illuminating a sample. This light source is preferably a tunable laser (swept source), for example a broadband laser, a supercontinuum laser and / or an ultra-short pulse laser. In this case, a tunable laser at a given point in time can be a narrowband light source, the center frequency of which, however, can be varied in a temporally targeted manner or can be formed from a plurality of narrowband light sources. However, other broadband sources can also be used, for example a superluminescent diode, for example in an FD-OCT.The OCT system further preferably has an interferometer designed to generate and superimpose a sample beam and a reference beam, for example a Michelson, Mach-Zehnder or Koster interferometer. The interferometer preferably has a beam splitter for generating and superimposing sample and reference beams from the light of the broadband source, a reference beam path and a sample beam path. Furthermore, the interferometer preferably has means for setting an examined sample depth. Depending on the measurement method, this can be a means for generating a path difference (such as a mirror displaceable in the reference beam in the case of an SD-OCT), a means for separating light of a specific path difference (such as an optical grating in the case of an FD-OCT) or a means for generating light of a specific path difference (such as a tunable source in the case of a swept source OCT).The OCT system preferably further comprises a scanning mechanism configured to raster the sample beam over the selected field of view. The scanning mechanism is in particular configured to raster the sample beam in two dimensions over the selected field of view. The scanning mechanism is preferably a scanning mirror, but other scanning mechanisms, such as a glass fiber scanner, a prism scanner, a Palmer scanner or the like, can also be used. In an OCT system configured for full field OCT, a scanning mechanism can be dispensed with.The OCT system preferably further comprises a detector configured to detect an interference pattern generated by superposition of sample beam and reference beam as a time-resolved OCT signal. The detector is, for example, a line detector, a two-dimensional detector array, a photodetector or a dispersive detector. The detector is designed, for example, as a CCD or as a CMOS detector.The OCT signal is preferably an interference signal, wherein the modulation of the envelope of the interference signal encodes reflection properties of the sample. By means of the scanning mechanism, the selected field of view can be scanned two-dimensionally at a sample depth set via the path difference. On the basis of the scanning mechanism used, the means used for selecting or generating the path difference, for example an adjustable mirror in the reference beam, an optical grating in front of the detector or a tunable broadband light source and the repetition rate of the detector, a clock frequency (image repetition rate) results for the time-resolved OCT signal.In a particularly preferred embodiment of the system according to the present disclosure, it further comprises an operation microscopic system. The surgical microscope system preferably has a real light source and an optical unit which is designed in particular for detecting light of the real light source reflected or backscattered from the anatomical structure. The optics comprise, for example, an objective lens and an eyepiece, preferably a half mirror eyepiece lens, but can additionally comprise further components, in particular further lenses, mirrors, beam splitters and / or the like.The surgical microscope system further comprises an image sensor which is configured to acquire a time-resolved image signal of the selected field of view of the anatomical structure. The optics and the image sensor are preferably integrated, for example as parts of a camera of a surgical microscope. The time-resolved image signal is in particular signals assigned to a plurality of surface elements of the anatomical structure, which are captured sequentially or simultaneously for a specific raster of the sample surface, wherein the raster is determined by a scanning mechanism and / or the image sensor. The time-resolved image signal further has a clock frequency (image repetition rate) which is determined by a scanning mechanism and / or the image sensor.According to this embodiment, the control unit is further configured to determine a two-dimensional image on the basis of the time-resolved image signal acquired by means of the at least one image sensor. For this purpose, the control unit preferably determines image data corresponding to the captured time-resolved image signal and generates a two-dimensional image therefrom. Furthermore, the control unit is preferably designed to generate video image data with a raster (resolution) and an image repetition rate from the time-resolved image signal, which video image data are suitable for display on the display means. The two-dimensional image is preferably generated such that the generated two-dimensional representation corresponds at least to a section of the generated two-dimensional image.The control unit of the system is further preferably configured to display the two-dimensional image together with the two-dimensional display on the display means.In this embodiment, the display means is preferably integrated into the eyepiece of the surgical microscope system. In a likewise preferred embodiment of the system according to the present disclosure, the control unit is further configured to display the two-dimensional representation at the position of the corresponding section of the two-dimensional image on the display means. In other words, the data of the two-dimensional representation and of the two-dimensional image corresponding to the same section of the selected field of view are displayed at the same location of the display means. For this purpose, the control unit is preferably designed to locally register the two-dimensional image and the two-dimensional representation as described above.In a likewise preferred embodiment of the system according to the present disclosure, the control unit is configured to determine an OCT image from the OCT signal by means of volume rendering, ray tracing and / or ray marching as a 3D volume image. Particularly preferably, the control unit is configured to determine the time-resolved OCT image as a three-dimensional volume image that is perspective from a virtual viewing direction. The control unit is also preferably designed to display the OCT signals in the form of sectional images in a height direction of the sample (so-called B-scans). Particularly preferably, the control unit is designed to represent the distances determined within the OCT image. In addition to the representation of the (liquid- and / or OVD-filled) cavities in an "en-face" representation, i.e. in a plan view, the control unit thus also enables the perspective representation of the OCT signals. The representation of the time-resolved OCT images as a three-dimensional and perspective volume image from different perspectives advantageously makes it possible to obtain maximum depth information about the object. In particular, both the straight representation from bird's eye view (top view, "en face"), these from different virtual viewing directions (azimuth and elevation angles) and sectional images (B-scans) along different intersecting lines can be expedient, for example in order to obtain the relevant information about the anatomical structure during different phases of an intervention. According to this embodiment, the control unit is further configured to also determine the virtual viewing direction on the basis of a user input, for example, by means of a user input which specifies an azimuth angle and an elevation angle of the viewing direction.In a particularly preferred embodiment of the system according to the invention, the latter is integrated into a surgical microscope. The surgical microscope preferably has an OCT system as described above. Furthermore, the surgical microscope preferably has an interface for user input and a display means or is connected to these. The surgical microscope preferably further comprises an surgical microscope system as described above, wherein the image sensor and the optical unit are part of a camera, in particular of a main observer camera or of a surroundings camera of the surgical microscope. The control unit of the surgical microscope is preferably designed as a control unit of the system according to the invention and is designed in particular to carry out the method according to the invention as described above on the basis of commands stored on a storage unit of the surgical microscope.Within the scope of the present disclosure, a surgical microscope is understood in the broadest sense to mean a microscope suitable for use during surgery. The surgical microscope preferably has a holder which allows imaging of the surgical region independently of the surgeon's head movements. Furthermore, the surgical microscope preferably has at least one device for splitting the observation beam path and at least two eyepieces. Alternatively, the surgical microscope is a pure "digiscope" without eyepieces. The surgical microscope likewise preferably has at least one imaging sensor. Furthermore, the surgical microscope preferably has a main observer camera and a surroundings camera. The surgical microscope can have kinematic or robotic aids for carrying out surgical interventions. Alternatively, a surgical microscope can be referred to as a medical microscope, a medical microscope or a medical microscope.Further preferred embodiments of the system according to the invention correspond to the preferred execution forms of the method according to the invention, as described above. The advantages of the system according to the invention correspond to the advantages of the method according to the invention, as described above.The functionalities of the control unit according to the invention can be implemented by electrical or electronic components or components (hardware), by firmware (ASIC) and / or by executing a suitable program (software). The functionalities of the control unit according to the invention are preferably realized or implemented by a combination of hardware, firmware and / or software. For example, individual components of the control unit according to the invention for carrying out individual functionalities are designed as a separately integrated circuit or are arranged on a common integrated circuit.The individual functionalities of the control unit according to the invention are furthermore preferably designed as one or more processes which run on one or more processors in one or more electronic computing devices and are generated when executing one or more computer programs. The control unit is configured to cooperate with the other components, in particular the user interface, the OCT system and the display means, in order to realize the functionalities of the system according to the invention described herein. It is also apparent to the person skilled in the art that the functionalities of a plurality of computers (data processing devices, control units, control units) can be combined or combined in a single device or that the functionality of a specific data processing device can be distributed over a multiplicity of devices in order to realize the functionalities of the control unit according to the invention. The devices can be arranged centrally or decentrally at different locations. In the case of a decentralized arrangement, suitable communication means are set up between the devices in order to transmit data between these devices which are required for carrying out the respective steps or for providing the respective functions of the individual devices.A further aspect of the present disclosure relates to a computer program comprising instructions which, when executed by a control unit as described above, preferably a control unit of a surgical microscope as described above, cause the system or surgical microscope as described above to execute the method according to the invention as described above. The computer program preferably comprises instructions which, when executed by a control unit as described above, preferably a control unit of a surgical microscope, cause the system or surgical microscope as described above to execute the method according to the invention in accordance with one of the preferred execution forms as described above. The computer program according to the invention is preferably stored in a volatile memory, for example a RAM element, or in a nonvolatile storage medium, such as a CD-ROM, a flash memory or the like.Further preferred embodiments of the invention result from the other features mentioned in the dependent claims and the figures explained below. The various embodiments of the invention mentioned in this application can be combined with one another with advantage unless stated otherwise in the individual case.Brief Description of the InventionThe invention is explained in more detail below with reference to an exemplary embodiment and associated drawings. The figures show: FIG. 1 shows a schematic flow diagram of a method for the analysis and representation of OCT signals according to one embodiment; FIG. 2 is an illustration of a selected field of view of an anatomical structure according to an embodiment; FIG. 3 is a diagram of a segmentation of anatomical sub-structures according to an embodiment; FIG. 4 is a diagram illustrating distance determination according to an embodiment; FIG. 5 is an illustration of determining a two-dimensional representation according to an embodiment; FIG. 6 is an illustration of an output in accordance with one embodiment; FIG. 7 shows a schematic representation of a system for the analysis and representation of OCT signals according to a first embodiment; and FIG. 8 shows a schematic illustration of a system for the analysis and illustration of OCT signals according to a second embodiment.Detailed Description of the FiguresFIG. 1 shows a schematic flow diagram of a method for the analysis and representation of OCT signals, in particular of OCT signals of an OCT system integrated into a medical device, according to one embodiment. FIGS. 2 to 6 illustrate steps of the method according to various execution forms.In a first step S 100 of the method, recorded OCT signals of a selected field of view 66 of an anatomical structure 65 are ascertained. FIG. 2 illustrates the selected field of view 66 of the anatomical structure 65. the anatomical structure 65 is an operating region of a patient, in particular an eye.The OCT signals comprise a plurality of A scans along a depth direction z of the anatomical structure 65. An A-scan is in particular a signal scanned at a single scanning point, i.e. a point in the x-y plane along the depth direction z (the optical axis). The A-scan therefore shows the reflection profile of the anatomical structure in the depth direction, for example, if A-scans are carried out at a plurality of or all scanning points along a line, one speaks of a B-scan or line scan. A B-scan shows in particular a reflection profile of a section through the anatomical structure in the depth direction, i.e. for example along an x-z or y-z plane. The plurality of A-scans can furthermore have a plurality of B-scans along a scanning direction, wherein scanning directions of the plurality of B-scans are each shifted with respect to one another in a lateral direction. The OCT signals then comprise a volume scan (C-scan) over part or all of the volume of the selected field of view.In a further step S 200 of the method, a segmenting of anatomical sub-structures 63, 64 along the depth direction z of the anatomical structure 65 takes place in the plurality of A scans. In other words, in this step S 200, a plurality of anatomical sub-structures 63, 64 are categorized within the anatomical structure, which is illustrated in FIG. 3.The method comprises, as a further step S 300, ascertaining distances 1, 2 between a first anatomical substructure 63 segmented in step S 200 and a segmented second anatomical substructure 64 in the plurality of A scans along the depth direction z, which is illustrated in FIG. 4. Here, a section in an x-z plane is shown by way of example. The distances 1, 2 define in particular (liquid- and / or OVD-filled) cavities 3 between the anatomical sub-structures 3 and are shown here only by way of example as a first distance 1 and a second distance 2. In particular, the distances are further compared with a second limit value and marked if they exceed this, as shown in the upper image of FIG. 4. A color corresponding to its absolute value from a color profile can also be assigned to the distances, as is illustrated in the lower image in FIG. 4.In a further step S 400 of the method, a two-dimensional representation 31 of the selected field of view 66 is determined on the basis of the OCT signals received in step S 100 and the distances 1, 2 determined in step S 300. The two-dimensional representation 31 is preferably determined as a plan view ("en face") of the selected field of view 66, which is illustrated in FIG. 5. The two-dimensional representation 31 has in particular markings of the distances 1, 2 or cavities 3 determined. A point (in the x-y plane) of the two-dimensional representation 31 is marked in particular on the basis of the distance 1, 2 which was determined in the associated A scan, i.e. one which was carried out at this point in the depth direction z. The upper image of FIG. 5 shows in particular a two-dimensional representation 31 which has been determined in such a way that a distance indicator is displayed for each A scan in which the determined distance 1, 2 exceeds the second predetermined limit value. The lower image of FIG. 5 shows a two-dimensional representation 31 which has been determined in such a way that for each A scan, a distance indicator corresponding to the determined absolute value of a distance 1, 2, in particular a color from a color profile, is displayed.As a further step S 500, the method comprises outputting the two-dimensional representation 31 on a display means. FIG. 6 shows how the display means, in particular, displays the two-dimensional representation 31 together with a two-dimensional image 32 of the anatomical structure 65 determined in a further method step. The data of the two-dimensional representation 31 and of the two-dimensional image 32 corresponding to the same section of the selected field of view 66 of the anatomical structure 65 are in particular represented at the same location of the display means. For this purpose, in particular, the two-dimensional image 32 and the two-dimensional representation 31 were registered, for example, by means of image analysis.The preferred embodiment shown in Fig. 6 could for example be advantageously applied during a DMEK. An important postoperative complication of DMEK is graft detachment. To minimize the risk of graft detachment, no gap should be left between the donor tissue and the patient's posterior corneal stroma during the graft positioning phase. On the display means, the physician performing the procedure can particularly easily identify possible cavities 3 between the graft and the cornea and also under what part of the surface of the anatomical structure 65, that is to say in particular of the eye 65, they are located. A knocking movement can then be carried out at these sites on the surface of the eye in order to eliminate the gap between the graft and the cornea and thus advantageously reduce the risk of graft detachment.Furthermore, the preferred embodiment shown in Figure 6 could be advantageously applied during an intervention using ophthalmic visual devices (OVDs), such as cataract, corneal, glaucoma, eye trauma and / or vitreoretinal surgery, particularly in phacoemulsification. During phacoemulsification, protection of the endothelium is of great importance. The endothelium, the posterior layer of the cornea, is very susceptible to stress and mechanical damage. If endothelial cells are damaged, this leads to irreversible cell death of these cells. And, as the cells die off, healthy cells of the endothelium migrate into the areas of the endothelium in which cell deficiency has occurred. This results in thinning of the cell density. OVDs contribute to protection of the corneal endothelium during phacoemulsification because they minimize instrument-tissue interaction and absorb shocks during cataract surgery. On the basis of the illustration on the output means shown in FIG. 6, a user can identify whether sufficient OVD is present and whether the endothelium is protected by the localization of the OVD. If necessary, a subsequent injection of OVD can then take place at those locations at which the OVD still does not provide sufficient protection.FIG. 7 shows a schematic illustration of a system 100 for detecting and visualizing OCT signals 19 according to a first embodiment.The system 100 has an OCT system 10 with a broadband light source 11, for example a superluminescent diode. The light from the light source 11 is directed into an interferometer comprising a beam splitter 14 and a movable mirror 15. In the beam splitter 14, the light is divided into a sample beam 12 and a reference beam 13. The sample beam 12 is scanned over the anatomical structure 65 by means of a scanning mirror 16, wherein at least a portion of a selected field of view 66 of the anatomical structure 65 is scanned. The reference beam 13 is directed onto the movable mirror 15 and reflected by the latter back onto the beam splitter 14. The sample beam 12 interacts with the anatomical structure 65, in particular the volume of the anatomical structure 65, and is scattered back by the latter to the scanning mirror 16 and is directed by the latter onto the beam splitter 14. There, the backscattered sample beam 12 and the reflected reference beam 13 are brought to superposition, wherein a path difference between the superposed beams 12, 13 is set by the movable mirror 15. The interference pattern 17 thus generated is detected by means of a detector 18, for example a CCD detector or a CMOS detector.The time-resolved OCT signal 19 acquired in this way is transmitted from the detector 18 to the control unit 40. The control unit 40 is further connected to a user interface 50 for detecting a user input and to a device interface 55 for receiving a device parameter. The device interface 55 serves, for example, for receiving a device parameter of a device connected to the device interface 55, for example an operation microscopic system 20, another imaging system or a medical instrument. Furthermore, the device parameter can originate from a tracking system (not shown) connected to the device interface 55, but characterize the medical instrument, for example its spatial position.The control unit 40 is designed to carry out the method shown in FIG. 1, i.e. in particular to determine a two-dimensional representation 31 of the received time-resolved OCT signal 19 and to transmit it to the display means 30 for representation.FIG. 8 shows a schematic illustration of a system 100 for detecting and visualizing OCT signals 19 according to a second embodiment. Like components are denoted by like reference numerals as in FIG. 1, and thus repeated description of these components is omitted.The system 100 of FIG. 2 differs from that of FIG. 1 in that it further comprises an operation microscopic system 20 with a camera 21. The camera 21 comprises an image sensor 22 and an optics 23 and is configured to capture the field of view 66 of the anatomical structure 65, so that as a result a time-resolved image signal 27 is captured. The camera 21 may be a mono camera or a stereo camera. The anatomical structure 65 is illuminated by means of a real light source 28. the control unit 40 determines a two-dimensional image 32 corresponding to the captured time-resolved image signal 27. The two-dimensional image 32 is displayed simultaneously or sequentially on the display means 30 together with the two-dimensional display 31, wherein a change between the two-dimensional display 31 and the two-dimensional image 32 takes place, for example, on the basis of a user input acquired by means of the user interface 50. The surgical microscope system 20 further comprises a device for splitting the observation beam path 26 which splits the light beam transmitted from the field of view 66 of the anatomical structure 65 to the camera 23 and provides a partial beam via an eyepiece 25 to the eye 24 of an observer. The display means 30 can in particular also be realized within the eyepiece 25.List of reference characters1 First distance 2 Second distance 3 Cavity 10 OCT system 11 Broadband light source 12 Sample beam 13 Reference beam 14 Beam splitter (interferometer) 15 Movable mirror (interferometer) 16 Scanning mechanism (scanning mirror) 17 Interference pattern 18 Detector 19 Time-resolved OCT signal 20 Operation microscopic system 21 Camera 22 Image sensor 23 Optics 24 Eye of a viewer 25 Eyepiece 26 Beam splitter 27 Time-resolved image signal 30 Display means 31 Two-dimensional representation 32 Two-dimensional image 40 Control unit 50 User interface 55 Device interface 63 First anatomical substructure 64 Second anatomical substructure 65 Anatomical structure 66 Field of view 100 System X X direction Y Y direction Z Z direction S 100 First method step S 200 Second method step S 300 Third method step s 400 fourth method step S 500 fifth method stepReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Cited Non-Patent LiteratureA practical comparison between Zhang's and Tsai's calibration approaches", Li et al., Proceedings of the 29th International Conference on Image and Vision Computing New Zealand, November 2014, Pages 166-171, DOI:10.1145 / 2683405.2683443

[0034]

Claims

Method for the analysis and representation of OCT signals (19), the method comprising the method steps: determining (S100) OCT signals (19) of a selected field of view (66) of an anatomical structure (65) acquired by an OCT system (10), wherein the OCT signals (19) comprise a plurality of A scans along a depth direction of the anatomical structure (65); segmenting (S200) anatomical sub-structures (63, 64) along the depth direction of the anatomical structure (65) in the plurality of A scans; determining (S300) distances (1, 2) between a segmented first anatomical sub-structure (63) and a segmented second anatomical sub-structure (64) in the plurality of A scans along the depth direction; determining (S 400) a two-dimensional representation (31) of the selected field of view (66) on the basis of the detected OCT signals (19) and the determined distances (1, 2); and outputting (S 500) the two-dimensional representation (31) on a display means (30).The method of claim 1, wherein an intensity of the OCT signals (19) between the first anatomical substructure (63) and the second anatomical substructure (64) falls below a first predetermined limit value.The method of claim 1 or 2, wherein an ophthalmic visual device, OVD, is located between the first anatomical substructure (63) and the second anatomical substructure (64).The method of claim 1 or 2, wherein the anatomical structure (65) comprises a anterior eye portion, the first anatomical substructure (63) comprises a cornea, and the second anatomical substructure (64) comprises a graft structure, an iris and / or a conjunctiva.Method according to one of the preceding claims, further comprising the steps of: capturing a time-resolved image signal (27) of the selected field of view (66) of the anatomical structure (65) by means of at least one image sensor (22); determining a two-dimensional image (32) of the selected field of view (66) on the basis of the time-resolved image signal (27); and displaying the two-dimensional image (32) together with the two-dimensional display (31) on the display means (30).Method according to claim 4, wherein the at least one image sensor (22) is part of an operation microscopic system (20) and the method comprises the steps of: registering the time-resolved image signal (27) and the OCT signals (19) on the basis of detection parameters of the OCT system (10) and the operation microscopic system (20); and / or registering the two-dimensional image (32) and the two-dimensional representation (31) by means of image analysis.Method according to one of the preceding claims, further comprising the steps of: determining, for each A-scan, whether the distance (1, 2) between the first anatomical substructure (63) and the second anatomical substructure (64) determined therein exceeds a second predetermined limit value and / or falls below a third predetermined limit value; and determining the two-dimensional representation (31) of the selected field of view (66) in such a way that a distance indicator is displayed for each A-scan in which the determined distance (1, 2) exceeds the second predetermined limit value and / or falls below the third predetermined limit value.Method according to any of claims 1 to 5, further comprising the steps of: determining, for each A-scan, an absolute value of the distance (1, 2) between the first anatomical substructure (63) and the second anatomical substructure (64) determined therein; and determining the two-dimensional representation (31) of the selected field of view (66) such that distance indicators corresponding to the determined absolute values are displayed.Method according to one of the preceding claims, further comprising the steps of: determining, for each A-scan, a position of the distance (1, 2) determined therein along a depth direction of the anatomical structure (65); and determining the two-dimensional representation (31) of the selected field of view (66) such that, for each A-scan, a depth indicator corresponding to the determined position is displayed.Method according to one of the preceding claims, wherein the display means (30) is designed to display stereoscopic images, is integrated into smart glasses and / or is integrated into the eyepiece of an operation microscopic system (20).Method according to one of the preceding claims, further comprising the step of: controlling a medical instrument to the position of an A-scan for which a distance (1, 2) between the first anatomical substructure (63) and the second anatomical substructure (64) greater than zero has been determined and preferably to the position determined according to claim 8 of the distance (1, 2) determined therein along the depth direction of the anatomical structure (65).A system (100) for the analysis and representation of OCT signals (19), comprising: a display means (30) configured for the time-resolved display of at least two-dimensional representations and images; and a control unit (40) configured to receive OCT signals (19) of a selected field of view (66) of an anatomical structure (65) comprising a plurality of A-scans along a depth direction of the anatomical structure (65) from an OCT system (10), segment anatomical sub-structures (63, 64) along the depth direction of the anatomical structure (65) in the plurality of A-scans; determine distances (1, 2) between a segmented first anatomical sub-structure (63) and a segmented second anatomical sub-structure (64) in the plurality of A-scans along the depth direction; determining a two-dimensional representation (31) of the selected field of view (66) on the basis of the received OCT signals (19) and the determined distances (1, 2); and outputting the two-dimensional representation (31) on the display means (30).The system (100) according to claim 11 further comprising an OCT system (10) comprising: a broadband light source (11), preferably a tunable laser; an interferometer (14, 15) configured to generate and superimpose a sample beam (12) and a reference beam (13); a scanning mechanism (16) configured to raster the sample beam (12) over the selected field of view (66); and a detector (18) configured to detect an interference pattern (17) generated by superposition of the sample beam (12) and the reference beam (13) as a time-resolved OCT signal (19).The system (100) according to claim 11 or 12, further comprising an operation microscopic system (20), the operation microscopic system (20) comprising: an optical system (23) and at least one image sensor (22) configured to acquire a time-resolved image signal (27) of the selected field of view (66) of the anatomical structure (65), wherein the control unit (40) is further configured to determine a two-dimensional image (32) on the basis of the time-resolved image signal (27) acquired by means of the at least one image sensor (22), and to display the two-dimensional image (32) together with the two-dimensional display (31) on the display means (30).The system according to any one of claims 11 to 13, wherein the control unit (40) is further configured to determine an OCT image as a 3D volume image by means of the OCT signals (19) by means of volume rendering, ray tracing and / or ray marching.A computer program comprising instructions which, when executed by a controller (40) of a system (100) according to any one of claims 11 to 14, cause the system (100) to perform a method according to any one of claims 1 to 10.

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