Improvements to the acquisition of images of the retina by optical coherence tomography

Abstract

Method for tracking retinal movements based on retinal images acquired by optical coherence tomography. The tracking method comprises the following steps: - obtaining at least one pair of retinal B-scan images, wherein each retinal B-scan image is acquired for a corresponding retinal optical scan during which an illumination beam is projected onto the retina and moved along an optical scan trajectory having a closed curve shape; - identifying, in the B-scan images of the selected pair of images, paired feature areas having similar speckle patterns; - calculating, based on the positions of the feature areas in the retinal B-scan images of the selected pair of images, tracking data indicative of retinal movements.

Description

Technical Field

[0001] This invention relates to the field of image acquisition systems via optical coherence tomography (OCT). More specifically, this invention relates to a method for tracking retinal movement based on images of the retina acquired via OCT. In another aspect, this invention relates to an apparatus capable of acquiring images of the retina (e.g., C-scan images or angiographic images of the retina) via OCT. Background Technology

[0002] As is known, optical coherence tomography (OCT), also known as phase-sensitive optical coherence tomography, is a technique that allows for the acquisition of high-resolution images (on the order of μm) of samples (e.g., biological tissue) in real time. Reconstructed information relating to the structure of the sample is obtained from the backscattered light radiation from the individual regions of the sample, based on their optical properties. Many examples of devices for examining the fundus via optical coherence tomography are known. These systems typically include a light source (e.g., a laser) and an interferometer optically coupled to the aforementioned light source.

[0003] The aforementioned interferometric device is arranged to provide an interferometric optical signal as an output, which is obtained by detecting the optical interference between the light radiation reflected by the retina of the eye and an optical reference point illuminated by a suitable illumination beam from a light source.

[0004] This type of examination device is typically used to obtain the volume of the retina. C scan Images or angiography images.

[0005] As is well known, images acquired by these devices are often affected by motion artifacts due to unwanted movement of the retina during image acquisition and processing. These motion artifacts typically manifest as streaks or bright areas, which can actually hinder or greatly limit observation of the retina. To mitigate this problem, devices for examining the fundus have been developed that incorporate retinal imaging equipment (e.g., fundus cameras) in addition to systems for acquiring images via optical coherence tomography.

[0006] The additional imaging device is advantageously configured to acquire images of the retina (e.g., video) while acquiring images via optical coherence tomography.

[0007] The images of the retina provided by the additional imaging device are processed to obtain tracking information indicating the movement of the retina during image acquisition via optical coherence tomography.

[0008] These tracking data may include, for example, data indicating the degree of retinal movement, the direction of retinal movement, and / or the speed of retinal movement.

[0009] This type of inspection device is characterized by its relatively large size and high industrial cost due to the presence of additional imaging equipment.

[0010] Furthermore, experience shows that these inspection devices are capable of providing retinal images at a relatively low maximum frequency (approximately 25 Hz). In practice, processing images provided by the additional imaging equipment requires a significant amount of time, which greatly impacts the overall performance of the inspection device. To overcome this problem, the installed computing resources could be appropriately increased. However, such a solution could lead to an unacceptably high increase in total industrial costs.

[0011] The above content clearly demonstrates the great need for innovative solutions in the existing technology that can overcome or mitigate the aforementioned problems.

[0012] The present invention aims to meet this need by providing a method for tracking retinal movement according to the appended claim 1 and related dependent claims. Summary of the Invention

[0013] In its general definition, the method for tracking retinal movement according to the present invention includes the following steps: - Obtain at least one pair of retinas B-scan Images, in which each retina is acquired for a corresponding retinal optical scan. B-scan The image, during the corresponding retinal optical scan, shows an illumination beam projected onto the retina and moving along an optical scan trajectory with a closed curve shape; - In the at least one pair of images thus obtained B-scan Identify paired feature regions with similar speckle patterns in an image; - Based on the feature regions in the retina of the at least one pair of images thus obtained B-scan The location in the image is used to calculate tracking data that indicates the movement of the retina.

[0014] Preferably, the tracking data includes one or more of the following: an estimate of the relative movement of the retina, an estimate of the direction of movement of the retina, an estimate of the speed of movement of the retina, and an estimate of the change in the speed of movement of the retina.

[0015] Preferably, the retina is acquired for the corresponding retinal optical scan included in the retinal optical scan group. B scanning The image, retinal optical scan group, consists of at least two retinal optical scans performed sequentially on each other.

[0016] Preferably, the retina is acquired for the corresponding retinal optical scan included in the retinal optical scan group. B scanning The image, the retinal optical scan group, includes at least two retinal optical scans, during which the illumination beam moves along the same optical scan trajectory.

[0017] According to one aspect of the invention, the step of calculating the tracking data includes calculating each retina B-scan The relative distance between a pair of feature regions in an image.

[0018] According to one aspect of the invention, the step of calculating the tracking data includes calculating each retina B-scan The position of the plane of symmetry between a pair of feature regions in an image.

[0019] In another aspect, the invention also relates to a method for acquiring images of the retina (e.g., images of the retina) via optical coherence tomography according to claim 8 and related dependent claims. C scan Devices that can display angiographic images (or angiographic images). Attached Figure Description

[0020] Further features and advantages of the invention will become clearer with reference to the description provided below and the accompanying drawings, which are provided purely as non-limiting examples, wherein: - Figure 1 An example of an embodiment of the device for examining the fundus according to the present invention is illustrated schematically; - Figures 2-4 Some steps of the method for tracking retinal movement according to the present invention are schematically illustrated; and - Figures 5-7 The operation of the device for examining the fundus according to the present invention is illustrated schematically. Detailed Implementation

[0021] The present invention relates to a method 100 for tracking retinal movement by optical coherence tomography (OCT).

[0022] The tracking method 100 is envisioned to be performed by a device used for examining the fundus via OCT.

[0023] Figure 1 The illustration schematically depicts an example of a device for examining the fundus, arranged to provide the patient's eye with OCT. E retina R The image.

[0024] Depending on the OCT technology used, device 1 can be of different types. For example, it can be arranged to use SD-OCT ( Spectral OCT ) or SS-OCT ( OCT sweep frequency source Optical coherence tomography (OCT) is used to acquire images of the retina.

[0025] Device 1 includes a light source 2, preferably configured to emit coherent electromagnetic radiation. For the application of interest, this light source may be, for example, a laser or a diode (…). Superluminescent diode or SLD It is configured to emit light with wavelengths in the infrared range.

[0026] In some applications (SS-OCT), the light source 2 is configured to emit an illumination beam according to a sequence of emission cycles, during which the emitted radiation has a very narrow bandwidth and its wavelength varies very rapidly and gradually within a predefined wavelength range. For example, for applications of interest, the light source can be configured to emit radiation with a wavelength that varies periodically within a wavelength range centered at approximately 1060 nm, with amplitudes on the order of 100 nm, and a repetition frequency on the order of tens or hundreds of kHz.

[0027] In other types of applications (e.g., SD-OCT type), light source 2 is configured to emit broadband light radiation.

[0028] The device 1 includes an optical detection unit 3, which is optically coupled to the light source 2, for example, via an optical fiber or other known optical coupling means.

[0029] The optical detection unit 3 is configured to receive light radiation from the light source 2. L S and provides measurement of the beam L M and reference beam L R Optical interference signals obtained from optical interference between I L As output.

[0030] Measuring beam L M From the retina R Reflected light radiation forms the retina R The first illumination beam formed by light radiation from the light source L illumination.

[0031] Reference beam L R By the second illumination beam L 2 The light radiation reflected from the optical reference point of the illumination forms the second illumination beam. L 2 It is formed by light radiation from a light source.

[0032] In practice, the optical detection unit 3 constitutes an interference structure that can be manufactured based on known structures (e.g., Michelson or Mach-Zehnder structures).

[0033] The optical detection unit 3 includes an interferometric measurement arm 4 and an interferometric reference arm 6 optically coupled to the light source 2.

[0034] Interferometric arm 4 is configured to receive the first illumination beam. L As input, and provide the measurement beam L M As output.

[0035] First illumination beam L Including light radiation from light source 2 L S The first part, and the measuring beam L M Including the retina R illuminated by the first beam of light L After illumination from the retina R Backscattered light radiation.

[0036] Interferometric arm 4 preferably includes a first optical path 40, along which a first illumination beam... L Transmitted toward the patient's eyes E and measuring the beam L M They are transported in the opposite direction.

[0037] Generally, the first optical path 40 has a variable optical length, which essentially depends on the length of the patient's eye.

[0038] Interference reference arm 6 is configured to receive the second illumination beam. L 2 As input, and providing a reference beam L R As output.

[0039] Second illumination beam L 2 Including light radiation from light source 2 L S The second part, while the reference beam L R Including optical reference point T (For example, a reflective element included in the interferometric reference arm) is illuminated by a second illumination beam. L 2 After illumination, by optical reference point T Reflected light radiation.

[0040] Interference reference arm 6 preferably includes a second optical path 60, along which the second illumination beam... L 2 Transmitted toward the optical reference point T and reference beam L R They are transported in the opposite direction.

[0041] Preferably, the second optical path 60 has an adjustable optical length. During use of the device, this optical length advantageously varies relative to the length of the optical path 40 in the interferometric arm 4.

[0042] Preferably, the optical detection unit 3 includes an optical fiber array 7 configured to optically couple the interferometric measurement arm 4 and the interferometric reference arm 6 to each other and to the light source 2.

[0043] Fiber optic array 7 is configured to receive light radiation from light source 2. L S The first part of the light radiation L The beam is directed toward the interferometric arm 4 to form the first illumination beam. L and the second part of the light radiation L 2 The beam is directed toward the interference reference arm 6 to form a second illumination beam.

[0044] Fiber optic array 7 is configured to receive the measurement beam from interferometric arm 4. L M The beam is directed toward the output port and interferometrically linked with the reference beam from interferometric reference arm 6. L R combination.

[0045] Fiber optic array 7 therefore provides optical interference signals I L (also known as " Measurement interferogram "), the optical interference signal I L By measuring beam L M (from the illuminated retina) R (Reflected and backscattered radiation) and reference beam L R (From the illuminated optical reference point) T Optical interference is generated between reflected radiation.

[0046] The optical interference signal indicates that it is illuminated by the first beam of light. L The reflectance distribution of the illuminated retinal portion as a function of the axial depth.

[0047] Preferably, the inspection device 1 includes (e.g., via optical fiber) optically coupled to the optical detection unit 3 and is configured to transmit interference signals. I L Converted into corresponding electrical detection signals I e Conversion unit 8. In the inspection device is SD-OCT In the case of a system, conversion unit 8 may include a spectrometer, or in the case of an inspection device. SS-OCT In the case of a system, the conversion unit 8 may include a photodiode assembly.

[0048] In the production of industrial-scale inspection devices, the conversion unit 8 can be physically integrated with the optical inspection unit.

[0049] The inspection device 1 includes a control unit 5 that is operatively coupled to the conversion unit 8 (according to known methods).

[0050] The control unit 5 is advantageously configured to perform control functions on the operation of the optical inspection unit 3. Naturally, the control unit can also be configured to control the operation of other components of the inspection device 1 (e.g., the conversion unit 8 and the light source 2).

[0051] Preferably, according to a known method, the control unit 5 includes at least one control module 51 electrically connected to the component to be controlled. The control module 51 is configured to provide appropriate control signals for the component to be controlled as outputs, receive appropriate detection signals sent by other devices (sensors, local control units, etc.) as inputs, and execute appropriate control algorithms, cooperating with other modules of the control unit when necessary.

[0052] Control unit 5 is also configured to perform data and signal processing functions to process the electrical detection signal provided as output by conversion unit 8. I e And based on this signal, one or more images of the retina are obtained.

[0053] Preferably, the control unit 5 includes an interface module 52 configured to receive an interference electrical detection signal. I e The signal is then sampled using known data and signal processing algorithms.

[0054] Preferably, the control unit 5 includes at least one data processing module 53, which is configured to process the sampled data provided by the interface module 52 and obtain one or more images of the retina. For this purpose, the data processing module 53 may be configured to execute known data and image processing algorithms.

[0055] The control module 51, interface module 52, and data processing module 53 can be industrially manufactured based on known solutions. For example, they may include suitable microprocessor circuitry. FPGA Or other types of electronic circuits mounted on a suitable circuit board.

[0056] During operation of the device, modules 51, 52, and 53 cooperate to perform the required functions. Furthermore, in the production of industrial-scale inspection devices, these modules can be physically integrated with each other.

[0057] In principle, the images that can be obtained from the retina can be of different types, for example A scan , B-scan or C scan Image. As will be seen below, the present invention is advantageously aimed at obtaining volumetric images of the retina. Q For example, C-scan images of the retina or angiography images.

[0058] As mentioned above, here is... Figure 1 The description of the inspection apparatus in the embodiments is purely illustrative and is not intended to limit the scope of the invention in any way. The tracking method 100 according to the invention can actually be performed by different types of inspection apparatus, and in principle can be performed by using… OCT Any device (of known type) that uses technology to acquire images of the retina can perform this action.

[0059] Tracking method 100 includes obtaining at least one pair of retinas B-scan image W 1 , W 2 The steps.

[0060] For each retina, an optical scan is performed to acquire the corresponding retina. B-scan Image, during the corresponding retinal optical scan, illumination beam L It is projected onto the retina and moves along an optical scan trajectory with a closed curve shape.

[0061] Preferably, the optical scanning trajectory has a circular shape.

[0062] Preferably, the obtained retina B-scan image W 1 , W 2 This relates to retinal optical scans included in a group of retinal optical scans, which comprises at least two retinal optical scans performed consecutively with each other.

[0063] Preferably, the retina is acquired for retinal optical scans included in the retinal optical scan group. B-scan image W 1 , W 2 The retinal optical scan group includes at least two retinal optical scans, during which the illumination beam... L Move along the same optical scan trajectory.

[0064] Tracking method 100 involves tracking based on the retina B-scan image W 1 , W 2 of Scattered pattern The above tracking information was obtained through analysis.

[0065] As is well known, based on the optical scan trajectory, the retina B-scan The image shows a two-dimensional portion of the retina, with dimensions along the surface of the retina and an axial depth along the retina (referencing the illumination beam). L The dimension of the axis (the plane of the retina), which in practice is perpendicular to the surface of the retina.

[0066] Any of the retina B-scan The image is characterized by a speckle pattern, that is, the distribution of small bright and dark areas on the background of the image.

[0067] retina B-scan The speckle pattern in an image is an optical interference phenomenon that is essentially dependent on the illuminated light beam. L The physical characteristics of the illuminated retinal portion. In practice, it clearly identifies the portion illuminated during optical scanning and acquired. B-scan The image shows the (two-dimensional) portion of the retina.

[0068] Based on the above, it is clear that if the illumination beam illuminates the same retinal portion, then the retinal image obtained by continuously performing retinal optical scans (during which the illumination beam moves along the same trajectory) will be... B-scan Images must have similar speckle patterns.

[0069] Conversely, if the illumination beams illuminate different parts of the retina, then the retina... B-scan The images will have speckle patterns that are different from each other.

[0070] For clarity, it is stipulated that if these retinas B-scan Image or B-scan The speckle patterns in parts of the image are highly correlated with each other (in practice, if these...). B-scan Image or B-scan(If the location and intensity of the bright and dark areas in the partial speckle pattern of the image have a high level of correspondence, then the retina...) B-scan Image or B-scan Parts of the image have "similar" speckle patterns.

[0071] Retinas compared to each other B-scan Image or B-scan The similarity between speckle patterns in parts of an image can be calculated in B-scan Image or B-scan A quantitative assessment is performed by using appropriate correlation indices between parts of the image and comparing the calculated correlation indices with appropriate thresholds.

[0072] Tracking method 100 utilizes this principle to obtain tracking information of retinal movement.

[0073] Figure 2 The illustration shows a portion of the retina illuminated during two consecutive retinal optical scans (preferably consecutive to each other). R 1 , R 2 During each scan, the illumination beam L It is projected onto the retina and preferably moves along the same circular trajectory.

[0074] Figure 3 It shows in Figure 2 The retina shown in the middle diagram R 1 , R 2 Based on whether it is parallel to or coincides with the illumination beam L Further views of the axis of observation.

[0075] As can be seen from the above figures, the retinal portion R 1 , R 2 Each of them has dimensions along the surface of the retina and a depth along the axial direction (i.e., along the illumination beam). L The dimension on the axis (which in practice is perpendicular to the surface of the retina).

[0076] Given that the optical scan trajectory is circular, each retinal segment R 1 , R 2 It has a basically tubular shape, which is along the corresponding longitudinal axis of symmetry. A 1 , A 2 extend.

[0077] If the retina remains stationary during continuous optical scanning, then the illuminated portion of the retina... R 1 , R 2 They will perfectly overlap and superimpose on each other.

[0078] However, as mentioned above, the retina is usually subjected to unwanted movement, which is usually caused by intentional or unintentional movement of the retina (saccadic retinal movement).

[0079] In the latter case, the illuminated portion of the retina R 1 , R 2 They are different from each other, and as in Figure 2 The figures shown are intertwined.

[0080] However, given that the optical scan trajectory has the shape of a closed curve (circle), the illuminated portion of the retina... R 1 , R 2 In a pair of overlapping regions R 12 , R 21 The areas partially overlap each other, and the overlapping areas are illuminated during both optical scans described above.

[0081] This naturally occurs with relatively limited retinal movement between one optical scan and the next. Nevertheless, considering the retina... B-scan The fact that image acquisition is typically completed within milliseconds is almost always true.

[0082] refer to Figure 3 Assuming the retina moves between one optical scan and the next according to the displacement vector... d Movement occurred. Clearly, it was in the illuminated portion of the retina. R 1 , R 2 Overlapping areas R 12 , R 21 How to locate depends on the displacement vector. d modulus (axis of symmetry) A 1 , A 2 (distance between) and direction (displacement angle) ).

[0083] Figure 4 A schematic diagram of the retina B-scan Image pairs W 1 , W 2 It shows the illuminated portion of the retina during two consecutive optical scans (preferably consecutive to each other). R 1 , R 2 .

[0084] Each B-scan The image can be referenced with the optical scan angle on the horizontal axis (according to the circular trajectory) and the retinal thickness on the vertical axis (along the illumination beam). L The same reference frame as the axis.

[0085] As discussed above, each B-scan The image is characterized by a speckled pattern.

[0086] Given the portion of the retina illuminated during continuous optical scanning R 1 , R 2 They are different from each other and in a pair of overlapping regions R 12 , R 21 Overlapping areas, retina B-scan image W 1 , W 2 They have speckle patterns that are generally different from each other. However, they are similar in characteristic areas. W 12 , W 21 The area has a similar speckle pattern, and this characteristic region corresponds to the aforementioned portion of the retina. R 1 , R 2 Overlapping areas R 12 , R 21 .

[0087] For clear geometric reasons, given that the optical scan path is circular, each B-scan image W 1 , W 2 Feature regions W 12 , W 21 Having the same plane of symmetryD (from a surface perpendicular to the retina and according to its displacement vector) d (Identified by the oriented plane).

[0088] Furthermore, given the retina B-scan image W 1 , W 2 With reference to the same frame of reference, each retina B-scan image W 1 , W 2 Feature regions W 12 , W 21 They are positioned at different relative distances a , b This is because the retina moves during the execution of continuous optical scanning.

[0089] Based on the above, it is clear that for each retina... B-scan image W 1 , W 2 Feature regions W 12 , W 21 Observations can provide tracking information that allows for tracking retinal movement between one optical scan and the next.

[0090] Therefore, the tracking method 100 includes the acquired retinal image W 1 , W 2 Identify feature regions with similar speckle patterns in the middle. W 12 , W 21 The steps, and subsequently based on each selected retina. B-scan image W 1 , W 2 Medium feature region W 12 , W 21 The position is used to calculate tracking data indicating retinal movement. Z The steps.

[0091] Identify and recognize the retina B-scan image W 1 ,W 2 Feature regions in W 12 , W 21 And calculate tracking data Z It can be advantageously performed using suitable image processing algorithms (which are also of known types).

[0092] Preferably, the tracking method 100 includes calculating each retina B-scan image W 1 , W 2 Feature regions in W 12 , W 21 relative distance between a , b .

[0093] Preferably, the tracking method 100 further includes calculating each retina B-scan image W 1 , W 2 Feature regions W 12 , W 21 The plane of symmetry between D Location . Plane of symmetry D Location Advantageously, it is the angular position measured relative to a reference value indicating the starting point of the first retinal optical scan being performed.

[0094] Preferably, tracking data of retinal movement. Z Includes one or more of the following: estimates of the relative movement of the retina, estimates of the direction of movement of the retina, estimates of the velocity of movement of the retina, and estimates of the change in the velocity of movement of the retina.

[0095] Advantageously, these estimates can be based on indicators of the retina. B-scan image W 1 , W 2 Feature regions in W 12 , W 21 Data on the relative positions between a , b , To calculate ( Figures 3-4 ).

[0096] For example, estimates of the relative movement of the retina. s 1 (displacement vector) d The modulus can be calculated based on the following relationship:

[0097] in a , b In each retina B-scan image W 1 , W 2 Feature regions in W 12 , W 21 The relative distance between them.

[0098] As yet another example, the estimate indicating the direction of relative movement of the retina. s 2 (displacement vector) d The angle can be calculated based on the following relationship:

[0099] in The plane of symmetry is measured relative to a reference indicating the starting point of the first retinal optical scan being performed. D The angular position.

[0100] As yet another example, the estimated velocity of the relative movement of the retina. s 3 (displacement vector) d The change in the modulus per unit time can be calculated based on the following relationship:

[0101] in a , b In each retina B-scan image W 1 , W 2 Feature regions in W 12 , W 21 The relative distance between them, and T s It is the optical scanning period (i.e., the time interval between two consecutive retinal optical scans).

[0102] As yet another example, the estimated value of the change in the velocity of retinal movement. It can be done in a relatively simple way based on the selected continuum. B-scan Estimates of retinal movement velocity calculated from image pairs s 3 To calculate.

[0103] Advantageously, the tracking data of retinal movement Z This may include further estimates suitable for describing the kinematic behavior of the retina during continuous optical scanning. For example, tracking data. Z This may include estimates indicating the speed of movement along the Cartesian axis of the reference frame in use, estimates indicating the change in speed of movement along the Cartesian axis of the reference frame in use, etc.

[0104] For simplicity, the above specifically refers to the case of performing continuous retinal optical scans along a circular optical scan trajectory. Figures 2-4 The tracking method 100 is described. This is not intended to limit the scope of the invention in any way. The tracking method 100 also allows for tracking of the retina based on optical scans performed along optical scan trajectories having different types of closed shapes (e.g., elliptical or oval). B-scan Image analysis to obtain tracking data indicating any movement of the retina. Z Naturally, in these cases, the estimate indicating retinal movement (tracking data) Z The calculation of ) is performed based on a different mathematical relationship than the above.

[0105] Because it is based on the retina, which can be naturally acquired by devices used to examine the fundus via optical coherence tomography. B-scan Image processing and tracking method 100 can be easily integrated with the retinal image acquisition process via optical coherence tomography.

[0106] Tracking method 100 allows information indicating retinal movement to be obtained very quickly. Therefore, it is particularly suitable for applications requiring automated retinal tracking processing that can be performed in real time to adjust the optical scan of the retina to account for any movement of the retina.

[0107] However, the tracking method 100 can also be used only to identify any movement of the retina during the acquisition of a volumetric image of the retina (e.g., a C-scan image or angiography image of the retina).

[0108] Tracking data Z can be used to verify any retina acquired. B-scan Whether the image is affected by motion artifacts so that the retina identified in this way can be repeatedly acquired. B-scan image.

[0109] The tracking data Z can also be used during post-processing to construct a retinal volumetric image without motion artifacts.

[0110] In another aspect, the present invention relates to an apparatus for examining the fundus by optical coherence tomography, for example... Figure 1 The type of inspection device shown in the diagram.

[0111] Preferably, the examination device is configured to perform a retinal image acquisition process 200, which includes the above-described process of acquiring a retinal image. B-scan The method of simultaneously tracking retinal movement in an image has 100 steps.

[0112] The acquisition process 200 includes performing a series of retinal optical scans. During each retinal optical scan, an illumination beam... L It is projected onto the retina and along the same optical scanning path. T The optical scanning path moves between one optical scan and the next. T According to the predefined translation direction D T It translates along the surface of the retina.

[0113] Figures 5-7 The illustration schematically depicts the execution of a series of retinal optical scans, during which the illumination beam... L Projected onto the retina and along the same optical scanning path T move.

[0114] It is clear how the acquisition process 200 involves executing an optical scanning grating with the same optical scanning path T, which repeatedly moves along the translation direction. D T Translation.

[0115] During each optical scan, by the illumination beam L Followed optical scanning path T It includes two intersecting optical scan tracks, specifically a first optical scan track with a closed curve shape. T 1 Second optical scanning trajectory T 2 .

[0116] Preferably, the first optical scanning trajectory T 1 It has a circular shape.

[0117] Preferably, the second optical scanning trajectory T 2 It has a closed curve shape and includes a pair of straight lines parallel to each other. T21 , T 22 .

[0118] Figure 5 The illustration shows the illumination beam during a normal optical scan in the acquisition process 200. L The example optical scanning path T is followed.

[0119] In this case, the optical scanning path T Including the first optical scan trajectory in a circular shape T 1 and a second optical scan trajectory with a closed curve shape T 2 The closed curve shape includes a pair of straight lines that are parallel to each other. T 21 , T 22 and a pair of opposite parts positioned such that they combine into a straight line. T 21 , T 22 The semi-circular part at the corresponding end T 23 , T 24 .

[0120] However, for the illumination beam L Provided optical scan trajectory T 1 , T 2 It can have a shape different from the shape shown in the figure. For example, the first optical scan trajectory. T 1 It can have an elliptical shape, while the second optical scanning trajectory T 2 It can have a rectangular shape.

[0121] Optical scanning trajectory T 1 , T 2 The relative positions between them may also differ from what is indicated. For example, although they are staggered, the aforementioned optical scan tracks may not be as... Figure 5 They partially overlap as shown in the diagram.

[0122] During each optical scan, a first set of optical scans is performed, comprising multiple (at least two) first optical scan cycles, during which the illumination beam is... L Projected onto the retina and along the first optical scan path T 1 move.

[0123] During each optical scan, a second set of optical scans is also performed, which includes one or more second optical scan cycles, during which the illumination beam is... L Projected onto the retina and along the second optical scan path T 2 move.

[0124] The number of first optical scan cycles and the number of second optical scan cycles performed during the same optical scan are not necessarily correlated.

[0125] For example, in obtaining retinal images C scan In the case of images, during each optical scan, the illumination beam L Can follow the first optical scan trajectory T 1 Move twice and along the second optical scan trajectory T 2 One movement. In this case, each optical scan involves performing two first optical scan cycles and only one second optical scan cycle.

[0126] For example, in acquiring angiographic images of the retina, during each optical scan, the illumination beam... L Can follow the first optical scan trajectory T 1 Move four times and along the second optical scan trajectory T 2 The movement is performed four times. In this case, each optical scan involves performing four first optical scan cycles and four second optical scan cycles.

[0127] During a normal optical scan, the execution order of the first and second optical scan cycles can be arbitrary, depending on the requirements. Therefore, the illumination beam... L It can first be along the first optical scan trajectory T 1 Move and then along the second optical scan trajectory T 2 Move, or vice versa, or even in an alternating manner.

[0128] According to acquisition process 200, the retina is acquired for each first optical scan cycle performed during each retinal optical scan. B-scan image.

[0129] Therefore, the acquisition process 200 involves, during continuous retinal optical scanning, whenever an illumination beam... L Along the first trajectory T 1Acquire retinal images while moving B-scan image.

[0130] Advantageous use of the retina obtained thereby B-scan The set of images is used to calculate tracking data indicating retinal movement according to the tracking method 100 described above. Z .

[0131] In practice, the acquisition process 200 includes: - Obtain one or more retinas for the corresponding consecutive first retinal optical scan cycles. B-scan image W 1 , W 2 right; - Identification is included in each pair of selected images B-scan image W 1 , W 2 Feature areas with similar speckle patterns W 12 , W 21 right; - Retina based on each pair of images B-scan image W 1 , W 2 Feature regions in W 12 , W 21 The location is used to calculate tracking data indicating the movement of the retina. Z .

[0132] Identify and recognize the retina B-scan image W 1 , W 2 Feature regions in W 12 , W 21 And calculate tracking data Z It can be achieved as described above.

[0133] Acquiring tracking data to be processed to calculate indicators of retinal movement. Z retina B-scan Simultaneously with the image acquisition process 200, the acquisition process involves acquiring the image to be processed to obtain the final retinal image. Q (For example, the retina) C scan Retina (images or angiography images) B-scan image.

[0134] The acquisition process 200 includes acquiring at least one retina for each second optical scan cycle. B-scan The image step involves illuminating the beam during the second optical scanning cycle. L Advantageously along the second optical scan trajectory T 2 move.

[0135] According to an embodiment of the present invention, two retinas are acquired for each second optical scanning cycle. B-scan Image. Specifically, whenever the illumination beam... L Along the second optical scan trajectory T 2 The corresponding straight line part T 21 , T 22 Acquire retinal images while moving B scanning image.

[0136] In this case, the illumination beam L Advantageously, it travels at essentially a constant speed along the second optical scan trajectory. T 2 Move so as to allow for each straight section T 21 , T 22 Get B-scan image.

[0137] According to this solution, two retinas can thus be obtained. B-scan A collection of images: containing images created by moving an illumination beam in one direction (forward). L And obtained B-scan The collection of images and its inclusion are achieved by moving the illumination beam in the opposite direction (backwards). L And obtained B-scan Another set of images.

[0138] Given the trajectory T 2 Forward and return straight sections T 21 , T 22 If they do not overlap, a brief retinal movement will damage two relatively distant parts of the grating.

[0139] As the acquisition continues, even without a command to reacquire the damaged area, the two damaged trace portions of the raster will be naturally reacquired.

[0140] Therefore, the first one obtained in the forward direction B-scan Image collection B-scan Images and the second set obtained in the return direction B-scan Images can be advantageously and selectively combined to exclude image portions affected by visual artifacts. This allows for the formation of the image to be processed in order to obtain the final retinal image. Q High-quality retina B-scan A collection of images.

[0141] According to an alternative embodiment of the invention, only one retina is acquired for each second optical scanning cycle. B-scan Image. Specifically, only when the illumination beam L Along the second optical scan trajectory T 2 straight line portion T 21 or T 22 The retina is only acquired when one of the movements occurs. B-scan image.

[0142] In this case, the illumination beam L It can be advantageously followed along the second optical scan trajectory T 2 It can move at a variable speed. Specifically, it can move at a lower speed along one of the straight sections of the trajectory to allow for higher resolution acquisition. B-scan The image, and another straight section of the trajectory, moves at a higher speed to complete the corresponding second optical scan cycle in a relatively short time.

[0143] This solution allows for the acquisition of images to be processed in a relatively short time to obtain the final retinal image. Q retina B-scan A collection of images.

[0144] Preferably, the acquisition process 200 includes processing tracking data of retinal movement obtained by performing the tracking method 100. Z To identify any retina acquired that is affected by motion artifacts B-scan The steps of image acquisition. In this case, the acquisition process 200 may include reacquiring any retina affected by motion artifacts. B-scan image.

[0145] Preferably, the acquisition process 200 includes tracking data based on indications of retinal movement. Z Processing the retina acquired for the corresponding second retinal optical scan cycle B-scan The steps involved in image processing. This data is obtained by processing retinal images acquired for the corresponding first retinal optical scan cycle. B-scan Obtained from images.

[0146] This step of processing the retinal image can advantageously include tracking data based on the calculations above. Z To select the acquired retina B-scan This allows the use of only retinas unaffected by severe motion artifacts. B-scan Images to obtain the final retinal image Q .

[0147] Treatment of the retina B-scan This step of image processing can also be advantageously performed using suitable image processing algorithms (which are also known types).

[0148] As is clear from the above explanation, method 100 for tracking retinal movement allows for tracking solely based on data obtained via optical coherence tomography. B-scan Images are used to obtain very high-quality retinal volume images, for example C scan Or angiography-type images, without the need for additional imaging equipment.

[0149] However, according to some embodiments of the present invention, the device 1 for examining the fundus is operatively coupled to or includes a configuration for acquiring images of the retina. S 9. Retinal imaging equipment.

[0150] The acquisition of the retinal image S is performed during the acquisition process of the retina 200. B-scan This is performed during image acquisition.

[0151] Preferably, the device 1 for examining the fundus is configured to process retinal images provided by the imaging device 9. S In order to calculate additional tracking data of retinal movement. Z1 .

[0152] Preferably, the device 1 for examining the fundus is configured to also be based on the aforementioned retinal movement tracking data. Z1 To process the retina acquired for the corresponding second retinal optical scan cycle B-scan Images, in order to obtain the final retinal image. Q .

[0153] The device for examining the fundus according to this embodiment of the invention is able to track retinal movement in a very fast and accurate manner.

[0154] However, they require high computing power to process the acquired data in real time. B-scan image.

[0155] Therefore, these machines are able to provide a high level of performance relative to their relatively high industrial costs.

[0156] Advantages of the present invention

[0157] The method 100 for tracking retinal movement according to the present invention offers many advantages compared to available prior art solutions.

[0158] Generally, it allows for data acquisition solely based on optical coherence tomography. B-scan Images to obtain very high-quality retinal images, such as C scan Or angiography-type images, without the need for additional imaging equipment.

[0159] The acquired tracking data of retinal movement can be combined with additional tracking data of retinal movement obtained by processing retinal images provided by a retinal imaging device in any case.

[0160] Because it is based solely on processing the retina B-scan Images, using the method 100 for tracking retinal movement, can acquire tracking data of retinal movement at a very high acquisition frequency (e.g., on the order of hundreds of Hz (tracking data / second)). Z .

[0161] The method 100 for tracking retinal movement according to the present invention is relatively easy to implement on an industrial scale without requiring additional optical, mechanical and electronic components.

[0162] It can be performed by a device used to examine the fundus via optical coherence tomography, which has a very compact structure and is relatively simple and inexpensive to manufacture on an industrial scale through standardized production techniques and processes.

Claims

1. A method (100) for tracking retinal movement using optical coherence tomography, characterized in that... The method includes the following steps: - Obtain at least one pair of retinas B-scan image( W 1 , W 2 ), where each retina is acquired through a corresponding retinal optical scan. B-scan Image, during the corresponding retinal optical scan, illumination beam ( L The light is projected onto the retina and moves along an optical scanning trajectory with a closed curve shape; - In the obtained B-scan image( W 1 , W 2 Identify paired feature regions with similar speckle patterns in ( ) W 12 , W 21 ); - Based on the feature region ( W 12 , W 21 In the obtained retina B-scan image( W 1 , W 2 The position in the retina is used to calculate tracking data indicating retinal movement. Z ).

2. The method according to claim 1, characterized in that, The retina B-scan image( W 1 , W 2 The retinal optical scan is acquired for a corresponding retinal optical scan included in a retinal optical scan group, which includes at least two retinal optical scans performed sequentially to each other.

3. The method according to one or more of the preceding claims, characterized in that, The retina B-scan image( W 1 , W 2 The illumination beam is acquired for a corresponding retinal optical scan included in a group of retinal optical scans, the group of retinal optical scans comprising at least two retinal optical scans, during which the illumination beam moves along the same optical scan trajectory.

4. The method according to one or more of the preceding claims, characterized in that, Calculate the tracking data ( Z The steps include calculating each retina. B-scan image( W 1 , W 2 A pair of feature regions () W 12 , W 21 The relative distance between them.

5. The method according to one or more of the preceding claims, characterized in that, Calculate the tracking data ( Z The steps include calculating each retina. B-scan image( W 1 , W 2 A pair of feature regions () W 12 , W 21 The plane of symmetry between ) D The position of ).

6. The method according to one or more of the preceding claims, characterized in that, The tracking data ( Z The estimate includes one or more of the following: an estimate indicating the relative movement of the retina, an estimate indicating the direction of movement of the retina, an estimate indicating the speed of movement of the retina, and an estimate indicating the change in the speed of movement of the retina.

7. The method according to one or more of the preceding claims, characterized in that, The optical scanning trajectory is circular.

8. An apparatus (1) for examining the fundus by optical coherence tomography, configured to perform the method (100) for tracking retinal movement according to any one of the preceding claims.

9. The apparatus according to claim 8, characterized in that, The device is configured to perform a retinal image acquisition process (200), which includes the following steps: - Perform a series of retinal optical scans, During each retinal optical scan, the illumination beam ( L ) is projected onto the retina and along the optical scanning path ( T ) moves, the optical scanning path ( T ) including the first optical scan trajectory ( T 1 ) and second optical scanning trajectory ( T 2 ), the first optical scanning trajectory ( T 1 It has a closed curve shape. The optical scanning path ( T ) between one optical scan and the next optical scan along a predefined translation direction ( D T Translation; During each retinal optical scan, a first retinal optical scan cycle is performed, and during each first retinal optical scan cycle, the illumination beam ( L ) is projected onto the retina and along the first optical scan path ( T 1 The illumination beam moves and performs one or more second optical scan cycles, during which the illumination beam ( L ) is projected onto the retina and along the second optical scan path ( T 2 )move; - Acquire retina for each first optical scan cycle B-scan image; - Acquire at least one retina for each second optical scan cycle B-scan image; - Process the retina acquired for the corresponding first optical scanning cycle according to the method (100) for tracking retinal movement. B-scan Images, to calculate tracking data indicating retinal movement ( Z ).

10. The apparatus according to claim 9, characterized in that, The acquisition process (200) includes processing the tracking data (Z) to identify potential retinal artifacts acquired during the second optical scanning cycle and affected by motion artifacts. B scan Description The steps for creating an image.

11. The apparatus according to any one of claims 9 to 10, characterized in that, The acquisition process (200) includes obtaining data based on the tracking data ( Z Processing the retina acquired for the corresponding second retinal optical scan cycle B-scan Images to obtain the final retinal image ( Q The steps are as follows.

12. The apparatus according to one or more of claims 9 to 11, characterized in that, The second optical scanning trajectory ( T 2 It has the shape of a closed curve and includes at least one straight line portion. T 21 , T 22 ), wherein in the illumination beam ( L ) along the at least one straight section ( T 21 , T 22 During movement, at least one retina is acquired for each second optical scan cycle. B-scan image.

13. The apparatus according to one or more of claims 11 to 12, characterized in that, The final retinal image ( Q ) is the retina C scan Images or angiography images.

14. The apparatus according to one or more of claims 9 to 13, characterized in that, The device is operatively coupled to or includes a retinal imaging device (9) configured to acquire retinal images during the performance of the series of retinal optical scans. S ).

15. The apparatus according to claim 14, characterized in that, The device is configured to process retinal images provided by the imaging device (9). S To calculate additional tracking data indicating retinal movement ( Z1 The device is configured to also base its tracking on the additional tracking data ( Z1 To process the retina acquired for the corresponding second retinal optical scan cycle. B-scan Images, in order to obtain the final retinal image ( Q ).

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