SYSTEM FOR CAPTURING AND VISUALIZING OCT SIGNALS

Description

Subject matter of the invention

[0001] The present invention relates to a system for acquiring and visualizing OCT signals, in particular for acquiring time-resolved OCT signals and for visualizing the OCT signals in the form of time-resolved OCT images. The present invention further relates to a method for acquiring and visualizing OCT signals. Technological background

[0002] The use of technological aids is an integral part of modern medicine. Imaging techniques and robotic systems are now used as routinely in surgery as in diagnostics. The use of imaging techniques allows for the visualization and differentiation of diverse structures within the patient, and the image data obtained from the patient can be advantageously used in diagnostics as well as in therapeutic and surgical procedures.

[0003] For example, a surgeon can use image data of a patient to better plan a surgical procedure and also receive support during the procedure itself. Robotic visualization systems are used to support surgeons during surgical procedures. These systems typically have at least one camera for capturing images of the area to be operated on, which is supported by a tripod with an articulated structure. The tripod allows the camera to be positioned relative to the patient through translational and / or rotational movements in order to capture images of a desired field of view ( field of view - FOV to capture the area to be operated on. The use of optical stereo cameras enables the acquisition of 3D image data.

[0004] In addition to capturing surface information of a desired field of view, for example using reflected or backscattered visible light, methods now also exist for capturing depth information of the field of view. These methods include optical coherence tomography ( optical coherence tomography, OCT Optical coherence tomography (OCT) is a three-dimensional microscopic imaging technique that allows for the imaging of optically transparent and / or reflective objects, thus enabling the acquisition of volumetric images of biological tissue within the field of view. OCT is essentially an interferometric method using broadband light with a short coherence length. Systems for acquiring OCT data therefore include an interferometer and a broadband light source with a spectral width greater than 1% of the central wavelength.

[0005] OCT data acquisition can be performed sequentially or in parallel. Sequential acquisition of OCT data is achieved, for example, by splitting a low-coherence source light beam into a sample beam and a reference beam using a beam splitter. These beams are then directed through two arms of an interferometer, with a movable reference mirror in the reference beam path and the object under investigation in the sample beam path. By moving the reference mirror, the path difference between the sample and reference beams, and thus the measured depth, can be adjusted. A mirror in the sample beam path scans the sample beam two-dimensionally, resulting in a three-dimensional scan of the sample.

[0006] When OCT data is captured in the time domain in this way ( time domain OCT - TD OCTThe spectral width of the light source Δλ corresponds to a coherence length LC of LC = λ* / Δλ. The axial resolution of an OCT system corresponds to the coherence length LC of the light source and denotes the resolving power of objects that are at least the coherence length apart along the optical axis. For example, a near-infrared light source 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 therefore has an axial resolution of approximately 1–10 µm. The transverse resolution of an OCT system is determined by the optics used in the optical path, in particular by the objective lens that focuses the light onto the object under investigation.

[0007] Sequential acquisition of OCT data is also possible in the frequency domain ( frequency domain OCT - FD OCT ), whereby a distinction is usually made between the use of a tunable source ( swept source OCT ) and the use of a dispersive detector ( spectral domain OCT- SD OCT ) is distinguished. In the swept source OCT The frequency of the excitation light source, often a laser, is tuned, allowing the path difference between the sample and reference beams, and thus the sampled depth, to be varied even without a movable reference mirror. In SD (sensitization and scanning), this is achieved by adjusting the frequency of the excitation light source, often a laser, thereby varying the path difference between the sample and reference beams and thus the sampled depth. OCT A broadband light source is also used, but the frequency components of the interference signal are separated before detection, for example by an optical grating.

[0008] Optical coherence tomography (OCT) allows for the acquisition of cross-sectional and volumetric data of biological tissue, significantly increasing the information available to surgeons. Therefore, integrating OCT into surgical microscopes is desirable to display both video data of the surface within a desired field of view and depth and / or cross-sectional images of that field. While current surgical systems are capable of producing volumetric OCT images, their acquisition time is relatively long, and rendering is limited to post-processing due to time and resource constraints. Real-time volumetric imaging during surgery has thus far been impossible.

[0009] With further advances in OCT technology and the increased capacity and speed of graphics processing units (GPUs), faster OCT methods for intraoperative imaging are becoming available. The resulting ability to display OCT volume images in real time opens up a wide range of possibilities for visualizing the acquired OCT signals, but suitable methods for this are not yet available. In particular, methods that provide a display of OCT signals optimized for medical or surgical applications are lacking. The use of suboptimal methods carries the risk of overwhelming or distracting the user, which can have serious consequences, especially for surgeons.

[0010] US 2021 / 169320 A1 and US 2021 / 169324 A1 disclose systems for accompanying ophthalmic procedures with an integrated stereoscopic visualization camera and an OCT system, whereby data from different imaging modes are to be fused to provide a synthesized representation of an object for a user, wherein this representation includes oblique views.

[0011] US 2022 / 117696 A1 discloses an operating microscope system that is intended to enable the registration of two-dimensional video image data and three-dimensional OCT data.

[0012] US 2012 / 092615 A1 describes a surgical microscope with two microscope imaging paths and an OCT unit with a beam splitter arranged in at least one of the microscope imaging paths, which directs part of the light coming from the sample (patient's eye) to one microscope imaging path and another part of the same light to the OCT unit.

[0013] The object of the present invention is to overcome or at least reduce the disadvantages of the prior art and to provide an improved system and an improved method for acquiring and visualizing OCT signals. Description of the invention

[0014] The problem according to the invention is solved by the subject matter of the independent claims. Preferred embodiments are the subject matter of the dependent claims.

[0015] A first aspect of the present disclosure relates to a system for capturing and visualizing OCT signals, in particular for capturing and visualizing such signals using a medical device, for example, an operating microscope.

[0016] The system according to the present disclosure comprises an OCT system. The OCT system preferably comprises 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 ultrashort pulse laser. A tunable laser can be a narrowband light source at a given time, but its central frequency can be varied over time, or it can be composed of multiple narrowband light sources. However, other broadband sources can also be used, such as a superluminescent diode, for example, in a FD-OCT.

[0017] The OCT system further preferably comprises an interferometer designed for generating and superimposing a sample beam and a reference beam, for example, a Michelson, Mach-Zehner, or Koster interferometer. The interferometer preferably includes a beam splitter for generating and superimposing the sample and reference beams from the light of the broadband source, a reference beam path, and a sample beam path. The interferometer further preferably includes means for setting a sample depth under investigation. Depending on the measurement method, these means can be a means for generating a path difference (such as a mirror movable in the reference beam in SD-OCT), a means for separating light with a specific path difference (such as an optical grating in FD-OCT), or a means for generating light with a specific path difference (such as a tunable source in a swept source -OCT).

[0018] The OCT system further comprises a scanning mechanism designed to scan the sample with the sample beam. The scanning mechanism is specifically designed to scan the sample beam across the sample in two dimensions. Preferably, the scanning mechanism is a scanning mirror; however, other scanning mechanisms, such as a fiber optic scanner, a prism scanner, a Palmer scanner, or the like, can also be used. A scanning mechanism is unnecessary in an OCT system configured for full-field OCT.

[0019] The OCT system also includes a detector designed to detect an interference pattern generated by the superposition of the sample beam and the reference beam. This detector can be, for example, a line detector, a two-dimensional detector array, a photodetector, or a dispersive detector. The detector may be, for example, a CCD or a CMOS detector.

[0020] The system according to the present disclosure further comprises a display device configured for the time-resolved display of stereoscopic image data. The display device is preferably configured for displaying image data with different (e.g., orthogonal) polarizations, in combination with polarizing glasses. Equally preferred is the encoding of the stereoscopic image data by means of color filtering and a combination with 3D glasses with color filters. However, the display device can also be a 3D screen, for example, a light field monitor or the like. The display device is preferably one or more screens, for example, at least one screen of an operating microscope, a screen permanently installed in an operating room, or a head-mounted display (HMD), for example, video glasses.The screen should preferably be a 4K and / or 8K capable screen.

[0021] The system according to the present disclosure further comprises a control unit that is connected to the OCT system and the display device, in particular for one-way or two-way data transmission. The control unit is configured to enable the OCT system to acquire a time-resolved OCT signal of a selected field of view ( region of interest - ROI) to target a sample. The sample is, for example, a patient's surgical site, or, in ophthalmic surgery, specifically an eye. However, the sample can also be any other surgical site, such as brain tissue in neurosurgery, tissue in the ear, nose, and throat region in ENT surgery, or gums, tartar, or dental nerves in dental surgery. Likewise, it can be any other tissue or specimen (in vivo, in vitro, or in situ). The field of view is preferably selected by a user. The time-resolved OCT signal is preferably acquired by generating a light signal and partially directing it as a sample beam onto the sample using the interferometer. Within the interferometer, this sample beam is superimposed with a reference beam, also generated from the light signal, to create an interference pattern.

[0022] The control unit of the system according to the present disclosure is further configured to determine a time-resolved first OCT image and a time-resolved second OCT image based on the acquired time-resolved OCT signal, a predefinable virtual viewing direction, and a stereo angle α. The OCT signal is an interference signal, wherein the modulation of the envelope of the interference signal encodes reflection properties of the sample. The scan mechanism allows the sample to be scanned two-dimensionally at a sample depth set via the path difference.The scanning mechanism used, the means employed to select or generate the path difference (e.g., an adjustable mirror in the reference beam, an optical grating in front of the detector, or a tunable broadband light source), and the detector's refresh rate determine a clock frequency (frame rate) for the time-resolved OCT signal. The control unit computationally generates time-resolved OCT images from the OCT signal, for example, using volume rendering, ray tracing, and / or ray marching. To do this, the control unit first determines a virtual viewing direction and takes this virtual viewing direction into account when generating the OCT image using volume rendering, ray tracing, and / or ray marching.Thus, according to the present disclosure, the system determines an OCT image based on the OCT signal and a predefined virtual viewing direction, thereby advantageously utilizing a degree of freedom provided by the OCT system for the perspective determination of the OCT image. The virtual viewing direction is fundamentally different from a user's actual viewing direction. Rather, the virtual viewing direction represents a spatial direction that can be predefined by the user as described below and / or determined based on device parameters as described below, and which serves as the basis for calculating the OCT image.

[0023] The control unit of the system according to the present disclosure is further configured to display the acquired time-resolved OCT images stereoscopically on the display device. The display is advantageously performed in the virtual viewing direction. The virtual viewing direction is preferably set for a defined period. It is also preferably the case that the virtual viewing direction is set in the form of a sequence and changes, for example, automatically after a predefined time has elapsed, upon detection of a predefined user input (e.g., actuation of a foot pedal), upon detection of a change in the state or position of a medical device, upon detection of a change in a device parameter, and / or upon detection of a change in the phase of a performed operation.The virtual gaze direction also preferably follows user input continuously or discontinuously, for example, based on a captured actual gaze direction of the user. Thus, for instance, the tilt of the user's head can be detected, and the OCT image can be created with a corresponding tilt and displayed on the screen. The system according to the present disclosure thus advantageously enables optimal visualization of the OCT signal according to the user's needs, thereby optimally utilizing the potential of the OCT signal and providing the user with maximum information content.

[0024] The control unit according to the invention is thus configured to determine a time-resolved first OCT image and a time-resolved second OCT image based on the time-resolved OCT signal, the virtual viewing direction, and the stereo angle, and to display the first and second OCT images stereoscopically on the display device. The stereo angle is crucial for the depth perception in the image visualization on the display device. In a stereo camera, the stereo angle corresponds to the angle between the optical axes of the individual cameras of the stereo camera and therefore depends on the distance between the cameras as well as the working distance of the cameras to the object (sample). Such a stereo angle is used computationally as a basis for generating the stereoscopic OCT images, which allows for variable adjustment of the stereo angle.A large stereo angle generally corresponds to a strong depth perception (as with the perception of nearby objects by the human eye), and a small stereo angle generally corresponds to a weak depth perception (as with the perception of distant objects by the human eye). Thus, according to the present disclosure, the system advantageously enables the display of OCT images with variable depth perception.

[0025] The control unit is further configured to determine the phase of a performed operation and to calculate the stereo angle based on this phase. For this purpose, the control unit is preferably connected to a memory containing a trained machine learning algorithm, such as a convolutional neural network (CNN) or similar. This algorithm was preferably trained using a large number of video image data and / or OCT images or image signals and / or OCT signals, to which a corresponding phase of an operation was assigned as a classification during training. Consequently, the trained algorithm is able to independently recognize a phase of an operation as a classification based on video image data and / or OCT images or image signals and / or OCT signals.Preferably, the control unit according to this embodiment is configured to select a stereo angle corresponding to the determined phase of the operation. The stereo data suitable for different phases of the operation are preferably stored in a look-up table (LUT) in memory or are also determined using a machine learning algorithm. This algorithm can be trained, for example, by assigning a corresponding phase of an operation and / or a corresponding stereo angle as one or more classifications to a large number of video image data and / or OCT images or image signals and / or OCT signals during training.

[0026] In cataract surgery, the surgical phases may include, for example: resting, incision, injection of the ophthalmic visco-surgical device (OVD), capsulorhexis, hydrodissection, phacoemulsification, irrigation / aspiration, intraocular lens implantation, wound closure / moistening, and non-surgical rest. In refractive surgery, the surgical phases may include, for example: idle rest, docking, applanation, occlusion / CG rotation, lens incision, lateral lens incision, cap incision, cap lateral incision, eye release, transition to the OPMI, OPMI positioning, incision opening, plane determination, cap bed separation, lens bed separation, lens removal and / or inspection, wiping, irrigation, slit lamp examination, and speculum removal. In dental surgery, the surgical phases may include, for example: access, extirpation, debridement, drying, obturation, and restoration.It should be noted that all or only some of these phases may be part of the respective operation, and that further operational phases may also be present and / or some phases may be omitted.

[0027] In a preferred embodiment of the system according to the present disclosure, the virtual viewing direction is defined by an azimuth angle and an elevation angle relative to the optical axis of the OCT system. The optical axis of the OCT system preferably corresponds to an optical axis of a (subsequently described) surgical microscopy system of the system according to the present disclosure and / or is preferably perpendicular to a surface of the sample. The azimuth angle preferably denotes an angle between 0° and 360° in a plane perpendicular to the optical axis, preferably in the plane of the sample surface. The azimuth angle is a plane angle and is measured between a zero point and a projection of the virtual viewing direction onto this plane. The azimuth angle thus defines a virtual viewing direction in the narrower sense.The elevation angle preferably denotes an angle between 0° and 90° in a plane containing the optical axis, preferably in a plane orthogonal to the sample surface. The elevation angle is a plane angle and is measured, for example, between the virtual viewing direction and the sample surface. The elevation angle thus defines a vertical viewing angle.

[0028] In a further preferred embodiment of the system according to the present disclosure, the control unit is configured to determine the time-resolved OCT image as a three-dimensional volume image in perspective from the virtual viewing direction. In addition to displaying OCT images in "en face"The control unit thus also enables the perspective display of OCT signals, i.e., in a top view. Furthermore, the control unit is preferably designed to display the OCT signals as cross-sectional images along a vertical dimension of the sample (so-called B-scans). Displaying the time-resolved OCT images as three-dimensional and perspective volume images from different viewpoints advantageously allows for obtaining maximum depth information about the object. In particular, the direct view from a bird's-eye perspective (top view, "en face"), from various virtual viewing directions (azimuth and elevation angles), as well as cross-sectional images (B-scans) along different lines of intersection can be useful, for example, to obtain the relevant information about the sample during different phases of a procedure.

[0029] In other words, particularly in medical (e.g., ophthalmological) applications, the most suitable virtual viewing direction can vary depending on the application and surgical situation. For example, it may be useful to initially display time-resolved OCT images (4D-iOCT) from the technical viewing direction of a video from an operating microscope (where the technical viewing direction is determined, for example, by a device parameter) to provide the user with the best overview. However, as the application or operation progresses, other virtual viewing directions, such as lateral ones, can provide significantly better depth information. The resulting perspective also more closely resembles the natural perspective of the human eye and therefore offers an advantage for microsurgical work.

[0030] The system according to the present disclosure preferably has an interface for capturing user input. The interface is preferably a hand switch or a foot switch. Equally preferably, the interface is a means for detecting head and / or eye movement or an actual direction of gaze, for example, integrated into video glasses or a Head-mounted display, HMD. The interface can also be designed to capture voice commands and may include at least one microphone for this purpose. Preferably, the interface is a keyboard, joystick, mouse, touchscreen, or a combination thereof.

[0031] According to this preferred embodiment, the control unit is further configured to control the interface for capturing user input. Preferably, the user input is preceded by an input prompt, which is, for example, displayed to the user via the output device. Also preferably, the user input is a selection from a plurality of predefined input options, which specify, for example, a virtual viewing direction, an operation to be performed, and / or an intervention to be carried out. Also preferably, the user input is freely definable by the user within a predefined framework. Also preferably, the control unit is configured to support the user during input, for example, by displaying a plurality of dialogs for the targeted querying of specific user inputs.

[0032] According to this embodiment, the control unit is further configured to determine the virtual viewing direction based on user input. The user can thus advantageously select the virtual viewing direction deemed optimal. Particularly preferably, the interface captures user input specifying the azimuth and elevation angles, for example, after a corresponding prompt to the user. Equally preferred are the azimuth and elevation angles derived from the user input, for example, from a viewing direction directly specified by the user via head and / or eye control.

[0033] Alternatively or additionally, the system also features a device interface designed to acquire a device parameter. This device interface is preferably an interface for connecting an operating microscope system, as described in detail below. Equally preferably, however, the device interface is also an interface for connecting any other imaging system. The device interface can also be an interface for connecting a medical instrument. Equally preferably, a system for tracking a medical or medical instrument can be connected via the device interface, whereby the tracking system can also be the operating microscope system or another imaging system.The medical instrument in question is, for example, a pointer, a probe, tweezers, an awl, a phacoemulsification tip, an endoscope, an endo-LED of a gripper, or the like. According to this embodiment, the control unit is preferably configured to communicate with the device interface, in particular to communicate bidirectionally, and furthermore to control the device interface for acquiring a device parameter of a device connected via the interface.

[0034] According to this embodiment, the control unit is further configured to determine the virtual viewing direction based on a device parameter acquired via the device interface. Preferably, a technical viewing direction of the operating microscope system or other imaging system can be determined based on the device parameters of a connected operating microscope system or other imaging system, and the virtual viewing direction can be set to the same technical viewing direction. This enables multimodal image acquisition and display, whereby a virtual viewing direction of the OCT image advantageously coincides with a (technical) viewing direction of the other image data.

[0035] Preferably, the device parameter describes the location, position, and / or state of a connected or tracked medical instrument (or a tracked medical instrument), and the virtual viewing direction is determined based on the location, position, and / or state of the medical instrument. For example, the virtual viewing direction can be determined according to the location of a pointer (possibly along the pointer's longitudinal axis) or according to the state of a gripper. The spatial orientation of the medical instrument can be determined by the instrument itself and / or by a tracking system.A medical instrument need not have any electronics of its own; its properties can be determined solely by the tracking system, possibly supported by markers placed on the medical instrument. Equally preferred is the (image) recognition of the medical instrument initiated by user input, which can be made on the instrument itself or otherwise.

[0036] A device parameter received via the device interface regarding the state of a connected medical device preferably also includes the actuation of an input device of the medical device, so that in this case the device parameter simultaneously represents a user input. It is also preferable to consider various device parameters together, such as the position of the medical device (for example, determined by the instrument itself and / or by a tracking system) and the actuation of an input device of the medical device. Thus, for example, a sequence of virtual viewing directions corresponding to a sequence of positions of the instrument can be advantageously captured. A device parameter describing the medical or medical device can be received via the device interface from the instrument itself or from a tracking system.Furthermore, the azimuth and elevation angles of the virtual viewing direction are preferably derived from a received device parameter, as described above.

[0037] In a preferred embodiment of the system according to the present disclosure, an OCT signal comprises a plurality of (first) tuples, each comprising (or representing) a volume element of the sample and a scattering intensity. The volume element of the sample is preferably defined by three spatial coordinates (for example, x , y and z) represents and can, for example, be interpreted as a sample voxel. In addition to the scattering intensity, the tuple can have other values. According to this embodiment, the display has a plurality of pixels, and the control unit is configured to determine the time-resolved OCT images based on the (first) tuples, the resolution of the display, and the virtual viewing direction such that specific pixels correspond to specific volume elements, i.e., that specific pixels display specific volume elements of the sample. In other words, the control unit determines an assignment of pixels of the display and volume elements of the sample. This assignment can depend on further settings, such as the raster resolution of the scanning mechanism used, but is preferably constant over time for a given selection of settings, such as virtual viewing direction, zoom level, and stereo angle.The control unit thus implements a local registration between pixels of the display device and the OCT signals or the determined OCT images.

[0038] Furthermore, the control unit is preferably configured to spatially register the OCT signals acquired by the OCT system based on acquisition parameters of the OCT system. Spatial registration of these signals refers to the correct correlation of these signals with a reference coordinate system, for example, the patient's coordinate system during a procedure, and enables a unique mapping of patient space coordinates to corresponding signal space coordinates. Signal registration preferably requires calibration of the OCT system. The acquisition parameters of the OCT system preferably include calibration parameters. The acquisition parameters of the OCT system preferably take into account the scan mechanism and / or the detector of the OCT system.Based on the local registration using the acquisition parameters, structures of the patient located at defined coordinates of the patient's space can be advantageously displayed correctly at the corresponding coordinates in the image space of the OCT images, especially with correct relative positions to each other.

[0039] In a particularly preferred embodiment of the system according to the present disclosure, it further comprises a surgical microscopy system designed to acquire a time-resolved image signal of the selected field of view of the sample. The surgical microscopy system preferably includes optics, in particular for acquiring light reflected or backscattered from the sample, for example, visible light. The optics comprise, for example, an objective lens and an eyepiece, but may also include further components, in particular further lenses, mirrors, beam splitters, and / or the like. The surgical microscopy system further comprises an image sensor designed to acquire a time-resolved image signal of the selected field of view ( region of interest - ROIThe control unit is designed to be integrated into a sample. The optics and the image sensor are preferably integrated, for example, as components of a camera in a surgical microscope. According to this embodiment, the control unit is further designed and configured to determine video image data corresponding to the acquired time-resolved image signal. The time-resolved image signal is, in particular, a multitude of signals assigned to surface elements of the sample, which are acquired sequentially or simultaneously for a specific grid on the sample surface, the grid being determined by a scanning mechanism and / or the image sensor. The time-resolved image signal also has a clock frequency (frame rate) that is determined by a scanning mechanism and / or the image sensor. The control unit generates video image data from this image signal with a grid (resolution) and a frame rate suitable for display on the display device.The control unit is also designed to display the video image data using the display device.

[0040] In the system according to the present disclosure, an image signal preferably comprises a plurality of (second) tuples. Each (second) tuple includes (or represents) a surface element of the sample and at least one grayscale value. The surface element of the sample is preferably represented by two lateral spatial coordinates (for example, x and y) and can, for example, be interpreted as a sample pixel. In addition to the grayscale value, which ultimately results from a detected intensity, each (second) tuple can also represent color values, for example, when detecting intensities for different colors using color filters placed upstream of the image sensor. According to this embodiment, the control unit is also configured to determine the video image data based on the (second) tuples and a resolution of the display means such that specific pixels display specific surface elements of the sample.In other words, the control unit determines a (second) mapping of pixels of the display and surface elements of the sample, in addition to the (first) mapping of pixels of the display and volume elements of the sample. This (second) mapping can depend on further settings, such as a zoom level of the surgical microscope system, but is preferably constant over time for given settings. The (second) mapping preferably corresponds to the (first) mapping. The control unit thus also implements a spatial registration between pixels of the display and image signals (video image data) of the surgical microscope system.

[0041] Furthermore, the control unit is preferably configured to spatially register the image signals acquired by the surgical microscopy system based on acquisition parameters of the surgical microscopy system. Registration of the signals preferably requires calibration of the surgical microscopy system. The acquisition parameters of the surgical microscopy system thus preferably include calibration parameters and / or optical settings of the surgical microscopy system, such as a focus length and / or a zoom level of an optical system (camera). In addition, the acquisition parameters preferably also include a set of intrinsic parameters of the surgical microscopy system. The intrinsic parameters define 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, where "imaging sensor" refers to both the sensor itself and the optics employed. For example, in a Tsai camera calibration, the intrinsic parameters include an effective focal length, the coordinates of a principal point (center of distortion) of an image signal, a first scaling factor, and / or a first radial lens aberration coefficient (distortion coefficient). Alternatively, other intrinsic parameters can be used for a Tsai camera calibration, such as those used for a Zhang camera calibration (see, for example, [reference]). "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).

[0042] The local registration of the OCT signals, together with the local registration of the video signals, advantageously enables the generation and display of the OCT images and the video image data, such that the generated time-resolved OCT image corresponds to at least a portion of the displayed video image data. Preferably, an OCT signal is acquired from the entire field of view, and an OCT image is created from at least a portion of the field of view. Equally preferably, an OCT signal is acquired from a portion of the field of view, and an OCT image is created from at least a portion of that portion. The control unit is further configured to display the time-resolved OCT image at the position of the corresponding portion of the video image data on the display device. Preferably, video image data and an OCT image are generated from the entire field of view and each is displayed on the entire display device.Preferably, an OCT image is generated of a section of the visual field and displayed on the display device at the position of the video data corresponding to that section. In other words, video image data and OCT images corresponding to the same section of the sample are displayed at the same location on the display device. The system according to the present disclosure thus enables seamless integration of video image data and OCT images on the display device, thereby allowing a user to view the multimodal image data more easily. The multimodal image data can thus be viewed without moving the head or eyes, which is particularly advantageous for the surgeon's attention during surgical imaging.

[0043] The system's control unit is preferably configured to display the video image data and the time-resolved OCT image simultaneously on the display device. This particularly allows a user to view both image modalities at the same time. To still enable differentiation between the different image data, the control unit is further preferably configured to display the video image data with a first transparency level and the time-resolved OCT image with a second transparency level. The first and second transparency levels preferably differ. It is also preferably the case that the first and second transparency levels vary over time. For example, the video signal is initially displayed with 0% transparency, while the OCT image is displayed with 100% transparency.Over time, the transparency of the video signal is continuously adjusted from 0% to 100%, while simultaneously the transparency of the OCT image is adjusted from 100% to 0%. This ensures a seamless transition between the display of the video image and the OCT image.

[0044] In a further preferred embodiment of the system according to the present disclosure, the control unit is configured to spatially register the video image data and OCT images by means of image analysis. Spatial registration of this image data refers to the correct linking of these images in a common image coordinate system. Registration based on the image data thus enables a relative linking of the image data for the most congruent possible representation of identical structures. For example, structural or tissue boundaries in the video image data and the OCT images can be detected and compared using image analysis, such as edge detection or the like. These structures can then be superimposed on the display device by translational shift, rotation, and / or scaling.Preferably, the local registration of the image data is carried out in addition to a local registration of the captured signals, as described above.

[0045] In a further preferred embodiment of the system according to the present disclosure, the control unit is configured to display the video image data and the time-resolved OCT image sequentially on the display means. In other words, at least at a certain location on the display means, only one of the video image data and OCT images is displayed at any given time. This advantageously enables a clear distinction between video image data and OCT data and also advantageously allows the simultaneous display of the different image data at different locations on the display means.

[0046] The control unit is preferably configured to display the video image data and the time-resolved OCT image with the same magnification, perspective, and / or stereo angle. This preferably enables perfect overlay of both image data when both video image data are displayed simultaneously at the same location on the display device and can advantageously allow for a display with optimized contrast. In sequential display, the transition between the spatially registered image data preferably results in a display with the same magnification, perspective, and / or stereo angle. This ensures a smooth transition between the display of the image data. For the video image data, only a surface view (top view) is possible. This corresponds, for example, to a "en face"OCT image. Once a transition from video image data to an OCT image has taken place, the magnification, perspective, and / or stereo angle can preferably be adjusted to advantageously enable an improved view with optimal depth perception. In particular, from the initial "en face" The view can be switched to a perspective representation, for example through a continuous transition of the virtual viewing direction, or to a sectional view (OCT-B scan). This ensures the perfect view at various stages.

[0047] In a preferred embodiment of the system according to the present disclosure, the control unit is configured to determine the stereo angle based on user input acquired via the interface. Thus, a user, for example an operator, can advantageously adjust the stereo angle individually, so that subjective preferences can also be advantageously taken into account by considering the user input when determining the stereo angle.

[0048] In a further preferred embodiment of the system according to the present disclosure, the control unit is further configured to determine the stereo angle based on optical parameters of the surgical microscope system. The optical parameters of the surgical microscope system are acquired or read in by the control unit of the system according to the present disclosure in the form of metadata. Thus, the control unit is advantageously always informed about variable as well as fixed optical parameters of the surgical microscope system. The fixed optical parameters preferably characterize components of the surgical microscope system, such as lenses, eyepieces, or the like, and the variable optical parameters preferably characterize adjustable values, such as a field of view, a resolution, an inclination of the optical axis, and the like.Taking into account the optical parameters of the operating microscope system advantageously enables simultaneous display of OCT images and video image data with optimal adaptation of the image data to each other, as well as sequential display of OCT images and video image data with optimal transition.

[0049] In a particularly preferred embodiment of the system according to the present disclosure, the surgical microscope system comprises a stereo camera with a first stereo lens (in combination with a first image sensor) arranged along a first optical axis and configured to capture a first image signal of the field of view, and a second stereo lens (in combination with a second image sensor) arranged along a second optical axis and configured to capture a second image signal of the field of view. The surgical microscope system is thus configured to capture stereoscopic, time-resolved image signals.The first and second optical axes of the surgical microscope system form an angle with each other, and this angle between the optical axes, together with the working distance between the sample and the objectives, determines the stereo angle of the stereoscopic image acquisition in the surgical microscope system. According to this embodiment, the control unit is preferably configured to determine the stereo angle used for the acquisition of the first and second OCT images according to the stereo angle of the surgical microscope system. Furthermore, the control unit is preferably configured to determine first video image data from the first image signal and second video image data from the second image signal. This embodiment thus advantageously enables a stereoscopic display of both the video image data and the OCT images with a corresponding stereo angle.This advantageously enables both simultaneous stereoscopic imaging with minimal deviations and sequential stereoscopic imaging with optimal transitions between different image modes (video and OCT image data). According to this embodiment, the optical parameters of the surgical microscopy system are or include at least those parameters that influence its stereo angle.

[0050] In another preferred embodiment, the control unit is configured to determine the stereo angle based on a zoom level and / or a working distance of the stereo camera. The distance between the cameras of the stereo camera is preferably fixed, so that the stereo angle depends solely on the working distance of the cameras to the sample. This working distance can preferably be determined based on the zoom level, for example, in combination with the size of a displayed field of view or a marker. If the distance between the cameras of the stereo camera is variable, for example, in the case of cameras that can be positioned by camera movement, the distance between the cameras is preferably also taken into account when determining the stereo angle.According to this embodiment, the control unit is preferably designed to determine the stereo angle of the operating microscope system at least on the basis of the zoom level and / or the working distance and to use this stereo angle for the OCT images as well.

[0051] In another preferred embodiment, the zoom level is also taken into account independently of the working distance. For example, when displaying a field of view with the surgical microscope system at a low zoom level, the use of a small stereo angle is preferred. A small zoom level generally corresponds to a large field of view, where a strong depth perception is usually not desired. Conversely, when displaying a field of view with the surgical microscope system at a high zoom level, the use of a larger stereo angle is preferred. A large zoom level corresponds to a small field of view, in which a detailed representation with a strong depth perception is often desired. Thus, at high magnifications, the depth perception in the display of the acquired OCT images is also advantageously increased.

[0052] In a further preferred embodiment of the system according to the present disclosure, it further comprises a medical device. The medical device is, for example, a probe, a pointer, tweezers, an awl, a phacoemulsification tip, an endoscope, an endo-LED, or the like.

[0053] According to this embodiment, the control unit is further configured to determine the position, type, and / or state of the medical instrument. The type of the medical instrument can preferably be determined via a device interface for connecting the medical instrument, by means of a tracking system (for example, by recognizing a target ID), and / or by input via a user interface. Equally preferred is the identification of the type of medical instrument placed in the field of view of the surgical microscope system by image analysis of the video image data, for example, by means of segmentation and object recognition. The position of the medical instrument is preferably determined by detecting a marker and / or a target comprising multiple markers, wherein the marker can be a marking on or a structure of the medical instrument.The detection of the marker and / or the target is preferably carried out using the operating microscope system and, if necessary, with the use of additional light sources (e.g., infrared LEDs) and / or after registration / calibration of the medical instrument (e.g., by positioning one tip of the medical instrument at a defined location).

[0054] The state of a medical instrument placed within the field of view of the operating microscope system is preferably determined by analyzing the video image data. For example, the image data can reveal whether forceps are open or closed. Furthermore, user input to change a state can be read by the control unit; for instance, user input to activate a phacoemulsification tip signals a change in its state. Additionally, a sensor attached to the medical instrument can detect changes in its state, such as the closing of forceps, and transmit a corresponding sensor signal to the control unit.

[0055] According to this preferred embodiment, the control unit is further configured to determine a stereo angle for generating stereoscopic OCT images based on the position, type, and / or condition of the medical instrument. A change in the condition of a medical instrument of a specific type and / or at a specific location is preferably indicative of a particular phase of an operation. Thus, the optimal display mode for this phase can be selected based on the detection of the position, type, and / or condition of the medical instrument. In addition to selecting the stereo angle, this optionally includes changing other display parameters of the OCT image data, such as a zoom level, a virtual viewing direction, a displayed depth, and / or a sectioning direction.

[0056] Based on the aforementioned information, the control unit is able, for example, to automatically or based on user input, to determine that a procedure performed is a membrane peel using tweezers, and in this case, furthermore to determine a distance or position of the tweezers relative to the eye and, depending on the aforementioned determinations, to adjust or set a virtual viewing direction and / or a stereo angle for the display of the OCT images.In another example, the control unit is preferably able to automatically or based on user input determine that a procedure being performed is a subretinal injection of a "bleb" or a placement of a retinal stent, and based on this, adjust a virtual viewing direction and / or stereo angle so that a user is optimally supported in positioning the needle or stent, for example by selecting a perspective view with a large depth impression (stereo angle).

[0057] The functionalities of the control unit according to the invention can be implemented by electrical or electronic components (hardware), by firmware (ASIC), and / or by executing a suitable program (software). Preferably, the functionalities of the control unit according to the invention are implemented by a combination of hardware, firmware, and / or software. For example, individual components of the control unit according to the invention are designed as separate integrated circuits for executing individual functionalities or are arranged on a common integrated circuit.

[0058] The individual functionalities of the control unit according to the invention are preferably configured as one or more processes that run on one or more processors in one or more electronic computing devices and are generated during the execution of 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 device, to realize the functionalities of the system according to the invention described herein. It is also apparent to those skilled in the art that the functionalities of several computers (data processing devices, control units, control devices) can be combined or combined in a single device, or that the functionality of a specific data processing device can be distributed across a plurality of devices to realize the functionalities of the control unit according to the invention.

[0059] In a particularly preferred embodiment of the system according to the invention, it is integrated into a surgical microscope. The surgical microscope preferably comprises an OCT system as described above. Furthermore, the surgical microscope preferably has an interface for user input and a display device, or is connected to such. Preferably, the surgical microscope also comprises a surgical microscopy system as described above, wherein the image sensor and optics are part of a camera, in particular a main observation camera or a peripheral camera of the surgical microscope. The control unit of the surgical microscope is preferably designed as the control unit of the system according to the invention and is particularly configured to carry out the method according to the invention, as described below, based on commands stored on a memory unit of the surgical microscope.

[0060] For the purposes of this disclosure, an operating microscope is understood in the broadest sense to be a microscope suitable for use during surgery. The operating microscope preferably has a mount that allows imaging of the surgical field independent of the surgeon's head movements. Furthermore, the operating microscope preferably has at least one beam splitter and at least two eyepieces. Alternatively, the operating microscope may be a simple "digiscope" without eyepieces. Also preferably, the operating microscope has at least one imaging sensor. Furthermore, the operating microscope preferably has a main observation camera and a peripheral camera. The operating microscope may include kinematic or robotic aids for performing surgical procedures.Alternatively, an operating microscope can be referred to as a medical-technical microscope, a medically approved microscope, or a medical microscope.

[0061] Another aspect of the present disclosure relates to a method for acquiring and visualizing OCT signals. This method includes the step of acquiring a time-resolved OCT signal from a selected field of view of a sample using an OCT system (as described above). The OCT signal comprises a plurality of tuples, each representing a volume element of the sample and a scattering intensity corresponding to that volume element. The method further includes the steps of determining a predefined virtual viewing direction and generating a time-resolved OCT image based on the tuples, a display resolution, and the virtual viewing direction, as a three-dimensional volume image and a perspective volume image from the virtual viewing direction.In the method according to the present disclosure, the time-resolved OCT image is ultimately displayed on the display device as a perspective volume image from the virtual viewing direction. The method according to the present disclosure realizes the same advantages as the system according to the present disclosure, and in this regard, reference is made to the above explanations.

[0062] In a preferred embodiment of the method according to the present disclosure, it further comprises the step of determining a time-resolved first OCT image and a time-resolved second OCT image. The first and second OCT images are each determined based on the tuples, the resolution of the display device, the viewing direction, and additionally a stereo angle, each as a three-dimensional volume image and a perspective volume image from the virtual viewing direction. According to this embodiment, the time-resolved first OCT image and the time-resolved second OCT image are further displayed stereoscopically on the display device. This advantageously enables stereoscopic display with variable virtual viewing direction and variable stereo angle.

[0063] In a further preferred embodiment of the method according to the present disclosure, it further comprises the step of determining a predetermined virtual viewing direction based on user input captured via an interface and / or based on a device parameter captured via a device interface.

[0064] Further preferred embodiments of the method according to the present disclosure correspond to the further preferred embodiments of the system according to the present disclosure and realize the same advantages as the embodiments.

[0065] Another aspect of the present disclosure relates to a computer program comprising instructions which, when executed by a control unit as described above, preferably an operating microscope as described above, cause the system or operating 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 an operating microscope, cause the system or operating microscope as described above to execute the method according to the invention according to one of the preferred embodiments as described above. The computer program according to the invention is preferably stored in volatile memory, for example a RAM element, or in a non-volatile storage medium, such as a CD-ROM, flash memory, or the like.

[0066] Further preferred embodiments of the invention are evident from the remaining features mentioned in the dependent claims and the figures described below. Unless otherwise specified in a particular case, the various embodiments of the invention mentioned in this application can be advantageously combined with one another. Description of the characters

[0067] The invention is explained below using exemplary embodiments with reference to the accompanying drawings. These show: Figure 1 is a schematic representation of a system according to a first embodiment; Figure 2 is a schematic representation of a system according to a second embodiment; Figure 3 is a schematic representation of a virtual viewing direction; Figure 4 is a schematic representation of a visualization of OCT signals as OCT images depending on a virtual viewing direction; Figure 5 is a schematic representation of a sample and a display device according to one embodiment; Figure 6 is a schematic representation of a display device and a medical instrument according to a further embodiment; and Figure 7 is a schematic flowchart of a method according to one implementation.

[0068] Figure 1 Figure 1 shows a schematic representation of a system 100 for capturing and visualizing OCT signals 19 according to a first embodiment.

[0069] System 100 comprises 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 movable mirror 15 and a beam splitter 14. In the beam splitter 14, the light is split into a sample beam 12 and a reference beam 13. The sample beam 12 is scanned across the sample 65 by means of a scanning mirror 16, scanning at least a section of a selected field of view 66 of the sample 65. The reference beam 13 is directed onto the movable mirror 15 and reflected from it back onto the beam splitter 14. The sample beam 12 interacts with the sample 65, in particular with the volume of the sample 65, and is backscattered by it to the scanning mirror 16 and directed from there onto the beam splitter 14.There, the backscattered sample beam 12 and the reflected reference beam 13 are superimposed, with a path difference between the superimposed beams 12, 13 being 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.

[0070] The time-resolved OCT signal 19 thus acquired is transmitted by the detector 18 to the control unit 40. The control unit 40 also receives user input regarding a desired virtual viewing direction via a user interface 50, which is preferably a head-mounted display (HMD) with means for detecting a user's head and / or eye movement. Alternatively or additionally, the control unit 40 receives a device parameter from a device connected via a device interface 55, for example, an operating microscope system 20, another imaging system, or a medical instrument 70. Furthermore, the device parameter can originate from a tracking system (not shown) connected to the device interface 55 but characterize a medical instrument, for example, its spatial orientation.

[0071] The control unit 40 determines a time-resolved OCT image 31 from the acquired time-resolved OCT signal 19 and based on a predefined virtual viewing direction 60, and transmits the time-resolved OCT image 31 to the display device 30 for presentation. The virtual viewing direction 60 is determined by the control unit 40 based on user input in user interface 50 and / or based on a device parameter determined via the device interface 55. For an explanation regarding the virtual viewing direction 60, please refer to the following description of the Figures 3 and 4 referred.

[0072] Figure 2 Figure 1 shows a schematic representation of a system 100 for acquiring and visualizing OCT signals 19 according to a second embodiment. Identical components are indicated with the same reference numerals as in Figure 1. Figure 1 These components are designated as such, and a repeated description of these components is omitted for reasons of brevity.

[0073] The System 100 of Figure 2 differs from that of the Figure 1 by further comprising an operating microscope system 20 with a first camera 21 with a first optic 211 and a first image sensor 212, and a second camera 22 with a second optic 221 and a second image sensor 222. With each of these cameras 21, 22, the field of view 66 of the sample 65 can be captured along an optical axis, so that a stereoscopic image signal 23 is captured, which comprises a first image signal 231 and a second image signal 232. The cameras 21, 22 are, for example, the two cameras of a main observer camera of an operating microscope designed as a stereo camera.

[0074] According to the embodiment of the Figure 2The control unit 40 determines stereoscopic video image data 32 corresponding to the acquired stereoscopic image signal 23, whereby a stereo angle α between the optical axes 213, 223 of the two cameras 21, 22 determines a depth impression or depth perception of the stereoscopic video image data 32 generated from the stereoscopic image signal 23. The stereoscopic video image data 32 includes first video image data 321 corresponding to the first image signal 231 and second video image data 322 corresponding to the second image signal 232. The stereo angle α depends not only on the distance between the cameras 21, 22 but also on the working distance between the cameras 21, 22 and the sample 65.

[0075] A time-resolved OCT signal 17 is used in the system 100 of the Figure 2 recorded in the same way as with regard to Figure 1As already described. However, the control unit 40 uses the OCT signal 17 to determine a first OCT image 311 corresponding to the first video image data 321 and a second OCT image 312 corresponding to the second video image data 321. The first OCT image 311 and the second OCT image 312 are generated, for example, as if they had been captured under the same stereo angle α as the first and second image signals 231, 232. However, the stereo angle of the OCT images 311, 312 can also be set differently based on user input acquired via the interface 50. The first and second video image data 321, 322 are displayed simultaneously or sequentially on the display device 30 together with the first and second OCT images 311, 312, whereby a change between the OCT images 311, 312 and the video image data 321, 322 is made, for example, by means of an input via interface 50.

[0076] Figure 3Figure 1 shows a schematic representation of a virtual viewing direction 60, in particular a first virtual viewing direction 601 and a second virtual viewing direction 602. Each of these virtual viewing directions 601, 602 is defined by an azimuth angle 61 and by an elevation angle 62 relative to an optical axis 63 of the OCT system 10. The optical axis of the OCT system 10 is preferably perpendicular to a surface of the sample 65. The azimuth angle 61 is a plane angle between 0° and 360° in a plane perpendicular to the optical axis 63. The elevation angle 62 is a plane angle between 0° and 90° in a plane containing the optical axis 63. The elevation angle is a plane angle and is measured between the virtual viewing direction 601, 602 and the horizontal (sample) plane. In the representation of Figure 3A first virtual viewing direction 601 is defined by a first azimuth angle α 1 of about 45° and by a first elevation angle β 1 of about 30°, and a second virtual viewing direction 602 is defined by a second azimuth angle α 2 of about 315° and by a second elevation angle β 2 of about 60°.

[0077] Figure 4 shows a schematic representation of a visualization of OCT signals 19 as OCT images 31 depending on a virtual viewing direction 60. Figure 4(A) This shows an OCT image 31 of sample 65 (image of sample "65") from a first virtual viewing direction 601 with the first azimuth angle α 1 and Figure 4(B) Figure 31 shows a different OCT image of sample 65 (image of sample "65") from a second virtual viewing direction 602 with the second azimuth angle α 2. For the sake of clarity, the effect of the different elevation angles β 1 and β 2 has been omitted.

[0078] Figure 5 Figure 1 shows a schematic representation of a sample 65 and a display means 30 according to one embodiment. The sample 65 has a plurality of volume elements 651 and a plurality of surface elements 652, wherein certain volume elements 651 correspond to certain surface elements 652. An exemplary selection of surface elements 652 is shown hatched, and while the majority of the volume elements 651 are shown with dashed lines, the four volume elements 652 corresponding to the hatched surface elements 652 are shown with solid lines. Furthermore, double-sided arrows connect these volume elements 651 with the associated surface elements 652.

[0079] With the OCT system 10 of the system 100 of the Figure 1In particular, the volume of sample 65 can be determined by superimposing short-wavelength light scattered from the sample beam 12 via the scan mirror 16 with the reference beam 17 using the interferometer. The interference pattern 17 thus generated and detected by the detector 18 as a time-resolved OCT signal 19 exhibits a multitude of first tuples 191, where the number of first tuples 191 results, for example, from the number of points scanned on sample 65 by the scan mirror 16. Each of the first tuples 191 corresponds to one of the depicted volume elements 651 and has a scattering intensity value. si Based on a calibration or registration of the OCT system 10 relative to a coordinate system of the sample 65 (patient), three spatial coordinates are further assigned to each of the first tuples 191. xi, yi, zi assigned. In the example shown, a first tuple 191 has the spatial coordinates x 1 , y 1 , z 1and the scattering intensity value s 1 on.

[0080] With the operating microscope system 20 of the system 100 of the Figure 2 The surface of sample 65 can be detected in particular by reflecting or backscattering long-wavelength (visible) light from it via the optics 211, 221 onto the image sensors 212, 222 of the cameras 21, 22. The image signals 321, 322 detected by the image sensors 212, 222 then each exhibit a plurality of second tuples 233, the number of which is determined by the resolution of the corresponding image sensor 212, 222. Each of the second tuples 233 corresponds to one of the depicted surface elements 652 and has a value of one gray level. gion, which corresponds to an intensity of the light reflected back onto the respective image sensors 212, 222. Based on a calibration or registration of the image sensors 212, 222 relative to a coordinate system of the sample 65 (patient), two lateral spatial coordinates are further assigned to each of the second tuples 233. xi, yi assigned. In the example shown, a second tuple 233 has the lateral spatial coordinates x 1 , y 1 and the grayscale value g 1 on.

[0081] The in Figure 5The display device 30 shown further has a plurality of pixels 33, in particular 42 pixels with 7 pixels in the horizontal direction and 6 pixels in the vertical direction. In the example shown, the resolution of the image sensor 12 resulted in the detection of the sample surface by the image signals 23 in 21 surface elements 652 with 7 surface elements 652 in the horizontal direction and 3 surface elements 652 in the vertical direction. Thus, in the video image data 32, one pixel 33 in the horizontal direction corresponds to one surface element 652, and two pixels 33 correspond to one surface element 652 in the vertical direction. Pixels 33 corresponding to the hatched surface elements 652 are also shown hatched, and the assignment is further clarified by arrows.As further illustrated by arrows, the control unit 40 of the system 100 also generates the corresponding OCT image 31 of the volume elements 651 corresponding to the surface elements 652 and displays it in the respective pixels 33 such that video image data 32 of specific surface elements 652 are displayed on specific pixels 33, and OCT images 31 of volume elements 651 corresponding to the surface elements 652 are also displayed on the specific pixels 33. Thus, corresponding OCT images 31 and video image data 31 are displayed at the same location on the display device 30.

[0082] A schematic representation of a display means 30 according to a further embodiment is shown in Figure 6 The system shows 100 as shown. Figure 2 Also shown is a medical instrument 70, in particular tweezers 70. In a Figure 6(A)During the depicted approach phase of the tweezers 70 to the sample 15, the open tweezers 70 and the sample 15 are displayed on the indicator 30 in the form of an OCT image 31. "en face" View (top view), i.e. with a view as in Figure 3 The displayed elevation angle is 90°. As soon as the control unit 40 recognizes, based on sensor values ​​and / or an evaluation of the OCT images 31 or, if applicable, video image data 32, that the tweezers 70 are closed and a vertical distance between a tip of the tweezers 70 and a surface of the sample 65 is equal to a predetermined limit value Δz 1 or less, the control unit 40 switches the display of sample 65 and, if applicable, tweezers 70 on the display medium 30 using the OCT image 31 from the "en face" View (top view) in a different virtual viewing direction 60. In particular, the control unit 40 determines an OCT image 31 as in Figure 6(B)The image shown is a perspective volume representation with a height angle of approximately 45°. In the example shown, the tweezers 70 are used to lift or detach a portion of the surface of the sample 65. As soon as the control unit 40 detects, based on sensor values, the OCT image 31, and / or the video image data 32, that the tweezers 70 are closed and that the vertical distance between a tip of the tweezers 70 and a surface of the sample 65 outside the lifted or detached surface of the sample 65 (e.g., laterally spaced by a minimum distance) is equal to a predetermined limit Δz 2 or greater, the control unit 40 changes the virtual viewing direction 60 of the OCT image 32 display again. As shown in Figure 6(C)The image is now displayed in a lateral perspective, i.e., with an elevation angle of near 0° on the display medium 30. Thus, the interaction between the surgeon and the operating microscope is continuously and objectively improved by the advantageous display of the acquired OCT signal 19, as the virtual viewing direction 60 of the display is enhanced based on user input acquired via the interface 50.

[0083] Figure 7Figure 1 shows a schematic flowchart of a procedure according to one implementation form. The procedure has a first step S100 of acquiring a time-resolved OCT signal 19 of a selected field of view 66 of a sample 65 using an OCT system 10, wherein the OCT signal 19 comprises a plurality of tuples 191, each representing a volume element 651 of the sample 65 and a scattering intensity corresponding to the volume element 651. The procedure further has a second step S200 of determining a predefined virtual viewing direction 60. In a third step S300, a time-resolved OCT image 31 is determined from the tuples 191, a resolution of a display device 30, and the virtual viewing direction 60 as a three-dimensional volume image and a perspective volume image from the virtual viewing direction 60. Finally, in a fourth step S400, the time-resolved OCT image 31 is displayed on the display device 30. Reference symbol list

[0084] 10 OCT system 11 Broadband light source 12 Sample beam 13 Reference beam 14 Beam splitter (interferometer) 15 Movable mirror (interferometer) 16 Scan mechanism (scan mirror) 17 Interference pattern 18 Detector 19 Time-resolved OCT signal 191 Tuple (OCT) 20 Surgical microscope system 21 First camera 211 First optics 212 First image sensor 213 First optical axis 22 Second camera 221 Second optics 222 Second image sensor 223 Second optical axis 23 Time-resolved image signal 231 First image signal 232 Second image signal 233 Tuple (image signal) 30 Display device 31 OCT image 311 First OCT image 312 Second OCT image 32 Video image data 321 First video image data 322 Second video image data 33 Pixel 40 Control unit 50 User interface 55 Device interface 60 Virtual viewing direction 601 First virtual viewing direction 602 Second virtual viewing direction 61 Azimuth angle 62 Elevation angle 63 Optical axis of the OCT system 65 Probe 66 Field of view 651 Surface element 652 Volume element 70 Medical instrument

Claims

1. System (100) for acquiring and visualizing OCT signals, comprising: an OCT system (10); a display means (30) designed for the time-resolved display of image data (31) as stereoscopic images; and a control unit (40) configured to drive the OCT system (10) to acquire a time-resolved OCT signal (19) of a selected field of view (66) of the sample (65) and to determine a time-resolved first OCT image (311) and a time-resolved second OCT image (312) on the basis of the acquired time-resolved OCT signal (19), a specifiable virtual viewing direction (60) and a stereo angle α and to stereoscopically display the first time-resolved OCT image (311) and the second time-resolved OCT image (312) on the display means (30), wherein the control unit (40) is further configured to determine a phase of a performed operation and to determine the stereo angle α and / or the virtual viewing direction on the basis of the determined phase of the performed operation.

2. System (100) according to Claim 1, wherein the virtual viewing direction (60) is defined by an azimuth angle (61) and an elevation angle (62) relative to the optical axis (63) of the OCT system (10).

3. System (100) according to Claim 1 or 2, wherein the control unit (40) is configured to determine the time-resolved OCT image (31) as a three-dimensional volume image from the perspective of the virtual viewing direction (60).

4. System according to any of the preceding claims, wherein the system (100) further comprises an interface (50) designed to acquire a user input and the virtual viewing direction is determined on the basis of a user input and / or wherein the system (100) further comprises a device interface (55) designed for acquiring a device parameter and the virtual viewing direction is determined on the basis of a device parameter acquired by means of the device interface (55).

5. System (100) according to any of the preceding claims, wherein the OCT signal (19) contains a multiplicity of tuples (191) each representing a volume element (651) of the sample (65) and a scattering intensity, wherein the display means (30) comprises a multiplicity of pixels (33) and wherein the control unit (40) is configured to determine OCT images (31) in such a way on the basis of the tuples (191), a resolution of the display means (30) and the virtual viewing direction (60) that certain pixels (33) correspond to certain volume elements (651).

6. System (100) according to any of the preceding claims, further comprising: a surgical-microscopic system (20) designed to acquire a time-resolved image signal (23) of the selected field of view (66) of the sample (65), wherein the control unit (40) is further configured to determine corresponding video image data (32) on the basis of the acquired time-resolved image signal (23) and to simultaneously or sequentially display the video image data (32) and the time-resolved OCT image (31) on the display means (30).

7. System (100) according to Claim 6, wherein the control unit (40) is configured to sequentially display the video image data (32) and the time-resolved OCT image (31) on the display means (30) with the same magnification, the same perspective and / or the same stereo angle α.

8. System (100) according to Claim 6, wherein the control unit (40) is configured to simultaneously display the video image data (32) with a first level of transparency and the time-resolved OCT image (31) with a second level of transparency on the display means (30).

9. System (100) according to Claim 1, wherein the control unit (40) is further configured to determine the stereo angle α on the basis of a user input acquired by means of the interface (50).

10. System (100) according to Claim 6, wherein the control unit (40) is further configured to determine the stereo angle α on the basis of optical parameters of the surgical-microscopic system (20).

11. System (100) according to Claim 6, wherein the surgical-microscopic system (20) comprises a stereo camera (21, 22) with a first stereo lens (211) arranged along a first optical axis (213) and a second stereo lens (221) arranged along a second optical axis (223) and the stereo angle α is an angle between the first optical axis (213) and the second optical axis (223), and wherein the control unit (40) is further designed to determine the stereo angle α on the basis of a zoom level and / or a working distance of the stereo camera (21, 22).

12. System (100) according to any of the preceding claims, further comprising a medical instrument (70), wherein the control unit (40) is configured to determine a position, a type and / or a state of the medical instrument (70) and to determine the phase of the performed operation on the basis of the position, the type and / or the state of the medical instrument (70).

13. Method of a control unit of a system (100) for acquiring and visualizing OCT signals, the method including the following method steps: acquiring (S100) a time-resolved OCT signal (19) of a selected field of view (66) of a sample (65) by means of an OCT system (10), wherein the OCT signal (19) comprises a multiplicity of tuples (191) each representing a volume element (651) of the sample (65) and a scattering intensity corresponding to the volume element (651); determining a phase of a performed operation; determining (S200) a given virtual viewing direction (60) and a stereo angle α, wherein the stereo angle α and / or the virtual viewing direction are determined on the basis of the determined phase of the performed operation; determining (S300) a time-resolved first OCT image (311) and a time-resolved second OCT image (312), in each case on the basis of the tuples (191), a resolution of a display means (30), the virtual viewing direction (60) and the stereo angle α, as a three-dimensional volume image from the perspective of the virtual viewing direction (60); and stereoscopically displaying (S400) the time-resolved first OCT image (311) and the time-resolved second OCT image (312) on the display means (30).

14. Method according to Claim 13, wherein a given virtual viewing direction (60) is determined (S200) on the basis of a user input acquired by means of an interface (50) and / or on the basis of a device parameter acquired by means of a device interface (55).

15. Computer program comprising commands which, upon execution by a control unit (40) of a system (100) according to any of Claims 1 to 12, cause the system (100) according to any of Claims 1 to 12 to carry out a method according to either of Claims 13 and 14.