Operation method of surgical system, surgical system, and operation program of surgical system

Abstract

To provide means for using a faint fluorescence source for fluorescence-guided surgery, in particular for open abdominal surgery.SOLUTION: In an operation method of a surgical system, a control device of the surgical system includes the steps of: emitting excitation light from an excitation light source onto a surgical area which contains a fluorescence source and onto which white light from a white light source is radiated; capturing one or more fluorescence images of the surgical field at a wavelength range of fluorescence light emitted by the fluorescence source as well as capturing one or more white light images; performing image processing by creating one or more false colour fluorescence images from the one or more fluorescence images, wherein a contrast between the fluorescence light emitted by the fluorescence source and background is increased; and creating one or more composite images by overlaying the one or more false colour fluorescence images over the one or more white light images.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a method for operating a surgical system for visualization of weak fluorescence in surgery, particularly in open surgery, a surgical system, and an operating program for the surgical system. [Background technology]

[0002] Fluorescence-guided surgery using fluorescent dyes is known in the art: a fluorescent dye, such as indocyanine green (ICG), is injected into the tissue to be examined or operated on, and once the fluorescent dye has penetrated the tissue, fluorescent excitation light is irradiated onto the dye-injected tissue, causing the fluorescent dye to emit fluorescent light (also called fluorescent light for short).

[0003] The basic principle of induced fluorescence is that the molecules that make up a fluorescent dye have an excitation wavelength spectrum within which they capture excitation light, absorb the energy of the captured excitation light, and transition to an excited state. The excited energy state of a fluorescent molecule is not stable. After a while, excess energy is released from the molecule in the form of de-excitation light (also called fluorescence light), and the fluorescent molecule returns to its basic energy state again. Fluorescence light has slightly lower energy than excitation light, which means that the excitation spectrum of the fluorescent dye is slightly shifted to a smaller wavelength relative to its fluorescence spectrum.

[0004] Thus, the excitation light used to excite the fluorescence of a fluorochrome has a wavelength slightly offset toward a smaller wavelength than the light of the observed fluorescence. This is useful because the amount of excitation light reflected from tissue into which the fluorochrome has been injected is orders of magnitude stronger than the resulting fluorescence itself, making it impossible to detect the fluorescence light in the presence of all the reflected excitation light. This slight wavelength shift is exploited by blocking the reflected excitation light from entering the camera using a wavelength filter configured to pass light at the wavelength of the fluorescence light.

[0005] Fluorescent dyes are not the only source of fluorescence in body tissues. Other sources include fluorescent probes used to label specific tissue types, such as cancerous tissue, and autofluorescent tissues, such as the parathyroid gland. The parathyroid gland contains naturally occurring fluorescent molecules that emit fluorescent light in the near-infrared spectrum when excited by an appropriate wavelength of excitation light. However, compared to the above-mentioned fluorescent dyes, the fluorescence signal emitted by autofluorescence is orders of magnitude weaker, i.e., it is easily brightened by other light sources, such as the excitation light or ambient light, which has components within the spectral region of the autofluorescence.

[0006] The autofluorescence of the parathyroid gland is excited in the wavelength range of about 785 nm and emits at about 820 nm to 830 nm, which overlaps with that of ICG, for example, which emits in the range of 800 nm to 830 nm and is excited around 780 nm.

[0007] Autofluorescent colon tissue and colon cancer also exists in the UV and visible spectrum, as exemplified by Li BH, Xie SS, "Autofluorescence Excitation-Emission Matrix for Diagnosis of Colon Cancer," World J Gastroenterol. 2005 Jul. 7;11(25):3931-4, or Bhaskar Banerjee MD et al., "Tryptophan Autofluorescence Imaging of Human Colon Tumors," J. Biomed. Opt. 17(1)016003 (Feb. 1, 2012).

[0008] The same applies to fluorescent probes used to label tissue types, such as cancerous tissue: such probes and markers generate a weak fluorescent signal comparable to the autofluorescence of the parathyroid gland, which is orders of magnitude smaller than the fluorescent dyes commonly used in fluorescence-guided surgery.

[0009] For these reasons, fluorescence-guided surgery based on a weak fluorescence source, such as a fluorescent probe that images the autofluorescence of the parathyroid gland or fluorescent light of a weak intensity similar to the aforementioned autofluorescence, cannot be used. [Prior art documents] [Non-patent literature]

[0010] [Non-Patent Document 1] Li BH, Xie SS, "Autofluorescence excitation-emission matrix for the diagnosis of colon cancer," World J Gastroenterol. 2005 July 7, 11(25):3931-4 [Non-patent document 2] Bhaskar Banerjee MD et al., "Tryptophan Autofluorescence Imaging of Human Colon Tumors," J. Biomed. Opt. 17(1)016003 (1 February 2012) Summary of the Invention [Problem to be solved by the invention]

[0011] It is an object of the present invention to provide a means for utilizing a weak fluorescent light source for fluorescence-guided surgery, particularly open surgery. [Means for solving the problem]

[0012] This object is achieved by a method for operating a surgical system for visualizing fluorescence in open surgery, in which a control device of the surgical system includes a fluorescence source that is a parathyroid tissue that emits autofluorescence and / or a fluorescent probe that emits fluorescence of an intensity similar to that of the autofluorescence, emits excitation light from an excitation light source onto a surgical area illuminated with white light from a white light source, captures one or more fluorescence images of the surgical area in the wavelength range of the fluorescent light emitted by the fluorescence source and one or more white-light images, creates one or more false-color fluorescence images from the one or more fluorescence images, performs image processing that increases the contrast between the fluorescent light emitted from the fluorescence source and a background, and creates one or more composite images by superimposing the one or more false-color fluorescence images on the one or more white-light images.

[0013] The method of operation of the surgical system is applicable to both still images and image sequences, such as video images. Increasing the contrast between the fluorescent light emitted by a weak fluorescent source and the background allows the weak fluorescent signal to be visible above the background, which can then be masked.

[0014] Preferably, the fluorescence image is captured using an image sensor at a high gain setting. The high gain setting causes the image sensor to become saturated in portions of the image with medium to high light intensity, while darker regions are enhanced and occupy the dynamic range of the image. However, weak fluorescence signals will occupy the lower part of the dynamic spectrum.

[0015] In embodiments, the contrast between the fluorescent light emitted by the fluorescent source and the background is increased by applying inverse gamma correction, which is a nonlinear transformation of brightness values ​​in a video or still image system that darkens relatively dark areas in the image while relatively bright areas of the image maintain their relatively bright intensity.

[0016] In this case, however, it is the dark parts of the fluorescence image that need contrast enhancement, so it is useful to use the inverse exponent of the logarithm function, hence the name "inverse gamma correction." Inverse gamma correction can also be called decoded gamma or gamma expansion.

[0017] Depending on the settings and the nature of the fluorescent light, the white light and fluorescent images are captured simultaneously or alternately in embodiments. Simultaneous capture of white light and fluorescent images is feasible when the fluorescent signal is outside the visible light spectrum captured in the white light image and an image capture device with an image sensor sensitive to the white light region on the one hand and the fluorescent signal region on the other is available.

[0018] On the other hand, if the wavelength of the fluorescent light falls within the white light spectrum, it is not possible to capture white light and fluorescent images simultaneously because the white light illumination will drown out the fluorescent signal. In such cases, it is possible to alternate between white light and fluorescent illumination and provide a composite image using a pair of a white light image and an immediately captured fluorescent light image, or vice versa.

[0019] It is also possible to intersperse fluorescent image captures between uninterrupted white-light image sequences and overlay the captured fluorescent images on each white-light image sequence if the sequence does not exhibit rapid motion, or if such motion is identified and the positions of the intermittent fluorescent images are adjusted to accommodate the motion and overlaid on the correct spots on each white-light image. Such intermittent capture of fluorescent images has the added advantage of reducing illumination flicker in the surgical field. Motion can be compensated for by the methods described with respect to readjusting the virtual region of interest.

[0020] In embodiments, the image processing for the one or more fluorescence images includes at least one of masking specular reflections, noise suppression, and normalization. Specular reflections appear as saturated regions of the image in the white-light image, the fluorescence image, or both. Such saturated regions can be excluded from further image processing in the fluorescence image and masked as background, for example, by setting the luminance values ​​of affected pixels in the fluorescence image to 0, i.e., black.

[0021] Noise suppression is a known technique in image processing and is beneficial in the present context because fluorescent signals from weak fluorescent sources are very weak. Such weak signals have a low signal-to-noise ratio, and in some cases, it can be difficult to separate the weak fluorescent signal from the noise. Known noise suppression techniques involve filtering across neighboring pixels and averaging the brightness of neighboring pixels or pixel clusters. Known noise reduction algorithms reduce or eliminate the visibility of noise by smoothing the entire image, leaving areas near contrast boundaries. While these methods can obscure fine, low-contrast details, in the present context, where the goal is to identify structures and tissues that exhibit weak fluorescence, this trade-off is acceptable in order to initially receive a clear signal that identifies the structure or tissue.

[0022] Normalization, performed during image processing of one or more fluorescence images, is used to create a false-color image representative of the fluorescence image. Normalization means that the dynamic range of the fluorescence image is focused on the interesting portion of the fluorescence image—i.e., in the case of weak fluorescence sources, on the low-intensity portion of the fluorescence image. In embodiments, normalization comprises percentile normalization, specifically clipping the darkest 1-2% and brightest 1-2% of the pixels in the fluorescence image, thereby eliminating saturated regions and signal-free background regions containing only noise. Alternatively or additionally, normalization can involve selecting the lower portion of the luminance spectrum and spreading the luminance information contained therein across the entire luminance spectrum, specifically the lower portion of the luminance spectrum, including 0%-20%, particularly 0%-10%, and especially 0%-5% of the luminance spectrum of the input fluorescence image. The range of the selected region should be adapted to the actual gain settings and signal distribution observed under the specific surgical conditions.

[0023] To optimize visibility of weak fluorescent signals in the composite image, a threshold below which weak fluorescent signals are detected and above which signals are discarded may be adjusted automatically or manually by the surgeon or with the surgeon's assistance. Automatic threshold adjustment can be achieved by automated analysis of the signal amplitude distribution. For example, the normalization algorithm can start with a threshold of 30% of the maximum brightness of the raw fluorescent image, select an isolated spot in the fluorescent image with a maximum intensity below that threshold, and select a new threshold representing the brightness value directly above that relatively brightest spot. Selecting an isolated spot prevents the algorithm from simply reaching the boundary of a saturated region that would have been masked using the initial 30% threshold. However, if other isolated spots enter saturation using a lower threshold, the threshold is increased again until all isolated spots are shown without their centers entering saturation, i.e., until the brightness of the center of each spot is greater than the threshold.

[0024] In an embodiment, image processing includes creating a virtual region of interest in the white light image and / or the fluorescence image, and the fluorescence image is cropped outside the virtual region of interest.

[0025] By creating a virtual region of interest and cropping the fluorescence image outside this virtual region of interest, fluorescence becomes visible only inside the virtual region of interest, while outside the virtual region of interest, the composite image consists of only a white-light image. This makes it much easier for surgeons to identify weak fluorescence sources because fluorescent light from outside the virtual region of interest does not interfere with the fluorescent light from weak fluorescence sources. In particular, the intensity of the false-color fluorescence image is normalized according to the intensity distribution within the virtual region of interest. Typically, fluorescent light from weak fluorescence sources can be easily emitted by other light sources, such as excitation light or ambient light with components in the same spectral region. By limiting the visibility of light in this spectral region to the virtual region of interest, these light sources are significantly suppressed, resulting in significantly greater contrast for weak fluorescence sources.

[0026] Furthermore, the intensity of the fluorescence from weak fluorescent sources within the virtual region of interest can be used to adjust the gain of the imaging sensor, which may be set too low due to the possible presence of specular reflections outside the virtual region of interest. Such bright spots outside the virtual region of interest are ignored, and thus the sensor gain control and / or image processing is focused on the virtual region of interest containing the sought-after weak fluorescent signal.

[0027] The images can be still or video. Using video for both the white light and fluorescent images provides a video feed in which a virtual region of interest containing parathyroid tissue or fluorescent probes is highlighted by providing fluorescent information on top of the white light video feed.

[0028] Preferably, the virtual region of interest is created by using manual control elements to control the placement and / or shape of the virtual region of interest. The manual control elements may be buttons, switches, and / or touchscreen displays. With the help of these manual control elements, the surgeon can select the virtual region of interest. For example, the surgeon can view a white-light image of the surgical region and select the virtual region of interest based on the white-light image. Alternatively, the surgeon can view a composite image in which a false-color fluorescence image is superimposed on the white-light image and select the virtual region of interest based on the composite image, or the surgeon can select the virtual region of interest based solely on the fluorescence image. The virtual region of interest can have any shape and form, such as a circle, an oval, a rectangle, or a shape that matches the outline of an organ or tissue visible in the white-light image.

[0029] The virtual region of interest is preferably automatically repositioned after movement to realign the virtual region of interest relative to the fluorescent source in one or more composite images. The movement can be due to patient movement or movement of the image capture device used to capture the images. Such movement can occur accidentally during surgery, for example, due to slight patient movement or shaking of the image capture device. However, such movement can change the position of the virtual region of interest relative to the faint fluorescent source. This is undesirable because it reduces the visibility of the fluorescence in the composite image and can distract the surgeon during surgery. To compensate for this movement, the virtual region of interest is automatically realigned to the faint fluorescent source. In this way, the movement does not interfere with the surgery.

[0030] According to another embodiment, the virtual region of interest is automatically repositioned by an algorithm trained to recognize the shape of organs containing or consisting of fluorescent sources, and the virtual region of interest is realigned with the organs. The algorithm can be an artificial neural network trained on white-light image data of organs, e.g., parathyroid glands, to reliably detect these organs in the new white-light image. The virtual region of interest is then realigned with the organ to compensate for movement.

[0031] According to another embodiment, the virtual region of interest is automatically repositioned by performing image analysis on the white-light image to identify image regions having a red wavelength spectrum, and the virtual region of interest is realigned with or set as an image region having a red wavelength spectrum. During surgery, the patient is typically draped with a blanket or cloth, with only a small opening around the surgical area. The incision made during open surgery typically appears as a red region in the white-light image, in contrast to the surrounding skin and blanket or cloth. This allows for the identification of the incision by image analysis of the white-light image, which identifies the incision as a region having a predominantly red wavelength spectrum. The region of interest can then be realigned to be centered on or set equal to a region having a predominantly red wavelength spectrum. This is a simple way to compensate for movement during surgery and mask light of the relevant wavelength spectrum from outside the incision.

[0032] According to one embodiment, specular reflections are detected using high intensity information in the white light image, and regions containing specular reflections are removed from the virtual region of interest. These regions also reflect fluorescent light, particularly near-infrared light, which causes undesirable high intensity spots to appear in the fluorescent image. Therefore, these regions are removed from the region of interest, eliminating the fluorescent information from these regions from the composite image.

[0033] This object is further achieved by a surgical system for visualizing fluorescence in open surgery, comprising a control device including an image processing unit, a light source device configured to generate excitation light and white light, and an image capture device configured to capture fluorescence images and white light images, wherein the control device controls the operation of the light source device, the image capture device and the image processing unit to perform a method for operating the surgical system according to one of the aforementioned embodiments.

[0034] The image capture device may be a camera. The image capture device may comprise an image capture unit for white light and a separate image capture unit for fluorescent light. The control device may be a controller, in particular a computer. The control device is configured to control the light source device to emit excitation light and white light into the surgical area and to control the image capture device to capture one or more fluorescent images and one or more white light images. The image processing unit performs image processing, in particular creating a virtual region of interest and / or creating a false-color fluorescent image and / or creating a composite image.

[0035] In particular, the light source device comprises an excitation light source and a white light source. The white light source may preferably be a light source that does not emit within the spectral range of the fluorescent signal of the weak fluorescent source, such as an LED or laser source. In particular, the system comprises an illumination and image capture device configured to emit white light and excitation light and to capture white light images and fluorescent images. Thus, light emission and image capture are combined in a single device.

[0036] This object is further achieved by an operation program for a surgical system that causes a control device of the surgical system to execute a method for operating a surgical system according to one of the above-mentioned embodiments.

[0037] The surgical system and operating program for surgical system for visualization of weak fluorescence in surgery embody the same advantages, functions, and characteristics as the method of operating a surgical system described above. Features described with respect to the method of operating a surgical system are explicitly applicable to the surgical system, and vice versa, and are applicable to the operating program of the surgical system that exercises control of the system components.

[0038] Further features of the invention will become apparent from the description of the embodiments according to the invention together with the claims and the included drawings. The embodiments according to the invention can feature individual features or a combination of several features.

[0039] The present invention is described below on the basis of exemplary embodiments, without limiting the general scope of the invention, and explicit reference is made to the drawings for the disclosure of all details according to the invention not described in more detail in the text. [Brief explanation of the drawings]

[0040] [Figure 1] 1 is a simplified schematic diagram of a surgical system for visualizing weak fluorescence during surgery. [Figure 2] 1 is a simplified schematic diagram of another surgical system for visualizing weak fluorescence in surgery. [Figure 3] 1 is a simplified schematic diagram of a composite image of a surgical field overlaid with a white light image and a fluorescent image. [Figure 4] 1 is a flowchart showing a method of operating a surgical system for visualizing weak fluorescence during surgery. DETAILED DESCRIPTION OF THE INVENTION

[0041] In the drawings, elements of the same or similar type or corresponding parts are given the same reference numbers so as not to have to reintroduce the items.

[0042] FIG. 1 shows a simplified schematic diagram of a surgical system 1 for visualizing weak fluorescence during surgery. The surgical system 1 (hereinafter referred to as system 1) includes a control device 3 having an image processing unit 4, which may be implemented as image processing software on a general-purpose computer or as a dedicated image processor configured to process images. The control device 3 is connected to and controls a light source 5 and an image capture device 8. The light source 5 includes both an excitation light source 6 and a white light source 7, and illuminates a surgical field 10. The excitation light 12 emitted by the light source 5 stimulates autofluorescent tissue 30 within the surgical field 10 and fluorescent probes that exhibit fluorescence of a similar intensity to the autofluorescence. Autofluorescent tissue 30, such as parathyroid tissue, emits fluorescent light 14 in a specific wavelength range. This wavelength range is typically in the near-infrared spectrum and does not usually overlap with the white illumination light, allowing the white light to be separated from the fluorescent light 14.

[0043] The image capture device 8 is configured to capture images in this wavelength range as well as white light images. Typically, the image capture device 8 comprises an image capture unit for white light, e.g., an RGB unit, and an image capture unit for fluorescent light 14. The images captured by the image capture device 8 are transmitted to the image processing unit 4 of the control device 3. The image processing unit 4 performs image processing to enhance the visibility of particular features of interest in the surgical field 10.

[0044] FIG. 2 shows another embodiment of a system 1 for visualizing weak fluorescence in open surgery. In this embodiment, the image capture device 8 and illumination are combined into a single illumination and image capture device 64. The image capture device 64 is connected to a light source 5 via a fiber optic cable 60 to illuminate a surgical area 10 of a parathyroid gland. The surgical area 10 includes a weak fluorescence source 16, e.g., an autofluorescent parathyroid gland. The image capture device 8 captures white-light and fluorescence images of the surgical area 10 and transmits the image information to a control device 3, e.g., an industrial computer, via a data cable 61. The images may be displayed on a display 63. Manual control elements 62, e.g., a keyboard and mouse, may be used by the surgeon to select a virtual region of interest 20 (hereinafter referred to as ROI 20) within the image and / or to perform image processing. Image processing may include increasing the contrast between the signal from the weak fluorescent source 16 and the background, applying inverse gamma correction, masking specular reflections, applying noise suppression, and / or applying normalization.

[0045] FIG. 3 shows a simplified schematic diagram of a composite image 50 created by the image processing unit 4. The composite image 50 can be displayed on the display 63 and consists of a false-color fluorescence image superimposed on a white-light image. The surgical field 10 shown in the composite image 50 includes tissue 40 and several surgical instruments 42 used during open surgery. Fluorescence is represented by diagonal lines in FIG. 3. An autofluorescent organ 31, such as the parathyroid gland, is shown in the center of the image, with certain portions emitting specific fluorescent signals 32 with higher intensities than the fluorescence of other autofluorescent tissues 30. Nevertheless, the intensity of the fluorescent signal 32 is much smaller than the intensity of other light sources, such as excitation light or ambient light, which has a component within the spectral range of the autofluorescence.

[0046] To enhance the contrast of the composite image 50, the surgeon can create or select a region of interest 20 within the image. The region of interest 20 is represented in FIG. 3 as a dashed circle, but can have different shapes and / or sizes. Outside the region of interest 20, the composite image 50 shows only the white light image, with the fluorescence image cropped out. The surgeon can select and position the region of interest 20 using manual controls 62, or can select the region of interest 20 directly on the display 63 showing the composite image 50.

[0047] If the patient or image capture device 8 moves during surgery, the region of interest 20 may no longer be aligned with the organ 31. To compensate for such movement, the system 1 is configured to track the movement and readjust the region of interest 20 accordingly. To track the movement, the image processing unit 4 can perform shape detection on high-intensity information in the white-light image to detect specular reflections. Specular reflections typically result in intensity spikes in the white-light image, which can be used to identify specific regions in the image and correct the position of the region of interest 20. Specular reflections may also be detected by the image capture unit for the fluorescent light 14. Furthermore, the image processing unit 4 can utilize an algorithm trained to recognize the shape of the organ 31, such as the parathyroid gland, to correct the position of the region of interest 20. The image processing unit 4 can also locate regions within the region of interest 20 based on color in the white-light image. Specifically, because tissue in open surgery typically appears red in the white-light image, the region of interest 20 is positioned primarily over an area in the red wavelength range.

[0048] FIG. 4 is a flowchart illustrating a method of operating a surgical system for visualizing weak fluorescence during surgery. In step 101, excitation light 12 is emitted from an excitation light source 6 onto a surgical field 10 containing a weak fluorescent source, e.g., parathyroid tissue exhibiting autofluorescence. In step 102, one or more images of the surgical field 10 in a wavelength range covering the wavelength range of the weak fluorescent source, as well as one or more white-light images, are captured. In step 103, image processing is performed on the captured images. Image processing may include creating a region of interest 20 in the white-light image and / or the fluorescence image. Outside the region of interest 20, image information in the fluorescence image is cropped. Image processing may also include increasing the contrast between the weak fluorescent source 16 and the background, applying inverse gamma correction, masking specular reflections, applying noise suppression, and / or applying normalization. In step 104, a false-color fluorescence image visible in the visible light spectrum is created from the fluorescence image. Next, in step 105, a composite image 50 is created by overlaying the false color fluorescence image on top of the white light image. In this composite image 50, the false color fluorescence is only visible within the region of interest 20.

[0049] All specified features, including those obtained solely from the drawings, and individual features disclosed in combination with other features, are considered to be essential to the invention both alone and in combination. Embodiments according to the invention can be realized by individual features or by a combination of several features. Features associated with the expression "especially" or "specially" should be treated as preferred embodiments. [Explanation of symbols]

[0050] 1. Surgical System 3. Control device 4 Image Processing Unit 5 Light source device 6. Excitation light source 7 White light source 8 Image capture device 10 Surgical area 12 Excitation light 14 Fluorescent Light 20 Areas of Interest 30 Autofluorescent Tissue 31 Autofluorescent Organs 32 Fluorescent Signals 40 organization 42 Surgical instruments 50 composite images 60 fiber optic cable 61 Data Cable 62 Control Elements 63 Display 64 Image capture device

Claims

1. 1. A method of operating a surgical system for visualizing fluorescence in open surgery, comprising: a control device of the surgical system, a fluorescence source that is a parathyroid tissue that emits autofluorescence and / or a fluorescent probe that emits fluorescence of an intensity similar to that of the autofluorescence, and emitting excitation light from an excitation light source onto a surgical area that is irradiated with white light from a white light source; capturing one or more fluorescence images of the surgical area in a wavelength range of the fluorescent light emitted by the fluorescence source, and one or more white light images; generating one or more false color fluorescence images from the one or more fluorescence images and performing image processing to increase the contrast between the fluorescent light emitted from the fluorescence source and a background; A method of operating a surgical system that causes one or more composite images to be created by overlaying the one or more false color fluorescence images onto the one or more white light images.

2. The method of claim 1 , wherein the fluorescence image is captured using an image sensor at a high gain setting.

3. The method of claim 1 , wherein the contrast between the fluorescent light emitted by the fluorescent source and a background is increased by applying an inverse gamma correction.

4. The method of claim 1 , wherein the white light images and the fluorescent images are captured simultaneously or alternately.

5. The method of claim 1 , wherein the image processing of the one or more fluorescence images includes at least one of specular masking, noise suppression, and normalization.

6. 6. The method of claim 5, wherein the normalization comprises cutting off the bottom 1 to 2% and the top 1 to 2% of pixels of the fluorescence image and / or selecting a lower portion of the luminance spectrum and spreading the luminance information contained therein across the entire luminance spectrum, the lower portion of the luminance spectrum comprising 0% to 20% of the luminance spectrum of the fluorescence image.

7. The method of claim 1 , wherein the image processing includes creating a virtual region of interest in the white light image and / or the fluorescence image, and the fluorescence image is cropped outside the virtual region of interest.

8. The method of claim 7 , wherein the virtual region of interest is created by using manual control elements to control the placement and / or shape of the virtual region of interest.

9. The method of claim 7 , wherein the virtual region of interest is automatically repositioned after movement to realign the virtual region of interest with the fluorescent light source in the composite image.

10. 10. The method of claim 9, wherein the virtual region of interest is automatically repositioned by an algorithm trained to recognize the shape of an organ containing or consisting of the fluorescent source, and the virtual region of interest is realigned with the organ.

11. 10. The method of claim 9, wherein the virtual region of interest is automatically repositioned by performing image analysis on the white light image to identify image regions having a red wavelength spectrum, and the virtual region of interest is realigned relative to the image regions having a red wavelength spectrum or set as the image regions having a red wavelength spectrum.

12. The method of claim 7 , wherein specular reflections are detected using high intensity information in the white light image, and regions containing the specular reflections are removed from the virtual region of interest.

13. 1. A surgical system for visualizing fluorescence in open surgery, comprising: a control device including an image processing unit; a light source device configured to generate excitation light and white light; an image capture device configured to capture a fluorescent image and a white light image; A surgical system that executes the method of claim 1 , wherein the control device controls the operations of the light source device, the image capture device, and the image processing unit.

14. An operation program for a surgical system that causes a control device of the surgical system to execute the operation method for the surgical system according to claim 1.

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