Patent Application
20240268638
The present disclosure relates to an attachment optics for a camera head and a system for fluorescence imaging in open surgery.
A medical application of fluorescence imaging, a subtype of molecular imaging, is fluorescent image-guided surgery, a medical imaging technique used to detect fluorescently labelled structures during surgery with the purpose of guiding the surgical procedure and providing the surgeon with real time visualization of the operating field, both in open surgery and in endoscopic procedures. Fluorescent dyes (fluorophores) commonly used in fluorescent image-guided surgery for different applications include indocyanine green (ICG) and others fluorescing in the visible and near infrared spectrum. The visible spectrum is defined by what a typical human eye will perceive, which ranges from about 380 nm to about 750 nm, possible individual deviations from these typical numbers notwithstanding. The boundaries are not sharply defined and may vary with the conditions under which light is perceived.
In the context of the present application, the terms visible spectrum, far red or near infrared are not to be understood as hard boundaries, but to generally conform to the human perception, which does not suddenly stop at 740 nm, but fades out gradually towards longer wavelengths. Likewise, most image sensors' spectral sensitivity distributions have similarly sloped edges.
In terms of fluorescent dyes, or fluorophores, that are used in medical fluorescence imaging, ICG, for example, has an excitation wavelength of between 740 nm and 800 nm and emission wavelength in the range of 800 nm to 860 nm, thereby being at the edge of the visible spectrum in the far red and generally extending into the near infrared spectrum.
One or more light sources are used to excite and illuminate the sample containing the chosen fluorescent dye. Light is collected using optical filters that match the emission spectrum of the chosen fluorescent dye. Imaging lenses and digital cameras having, e.g., CCD, CMOS or InGaAs image sensors are used to produce the final images.
In fluorescence imaging guided surgery, the surgeon gets to view a composite image with an overlay of the fluorescent image over a non-fluorescent background image for easy localization of the fluorescent areas within its surroundings. There are different ways to achieve such an overlay image. One option is that the background image and the overlay image are recorded simultaneously with different video chips and the recorded images are then electronically merged. In this case, the additional chip for the fluorescence is usually sensitive in a wavelength range outside the visible spectrum at wavelengths >700 nm.
Another option is to record a white light image and a fluorescent image alternating with the same video chip by also changing the illumination between white light and excitation light.
If the images may be recorded simultaneously and a camera head with three CCD or CMOS video chips for the blue, green and red channels are used also the blue and green video chips can be used for the white light image and the red video chip can be used for the fluorescent image in the near infrared.
One type of medical imaging systems comprises a camera head with exchangeable optical imaging units that are designed for endoscopic or open surgery applications. A camera head usually comprises one or more optical sensors as well as a cone adapter connecting and securing the ocular cones of optical imaging units to the camera head. Such optical imaging units may be devices for endoscopic procedures, such as rigid telescope type endoscopes having an optical assembly at their distal tip for forming an image of the specified field of view, and one or more relay lens units for relaying the image to the endoscope's ocular for view with the unaided eye, or alternatively, the camera head. For this purpose, the camera head comprises imaging optics that focus on the location of the virtual image projected by the ocular lens of the attached telescopes at their own focal length. This focal length is standardized between different types of telescopes, since they have to be usable with the unaided eye.
For the purpose of capturing the operating area for open surgery, the optical imaging units are often designed to create a virtual image of the operating area with a predefined field of view at a predefined working distance. A typical example is the so-called exoscope, which resembles a short endoscope with an objective lens, a set of relay lens units and an eyepiece. The optical properties of the objective lens are quite different from those of objective lenses of endoscopes because of their very different focal lengths, since, unlike an endoscope, an exoscope is designed to operate outside a human body instead of inside the human body.
In order to illuminate the operating area, the medical imaging systems usually comprise an illumination light generating unit comprising one or more light sources generating the illumination light. The illumination light is transported from the illumination light generating unit to the distal end of an optical imaging unit through a fiber bundle, where it exits the fiber bundle. Although they may have light shaping units such as lenses, endoscopes and exoscopes usually do not comprise any light shaping units at the tip, so that the irradiance distribution at the field of operation is mainly defined by the irradiance distribution with which the light enters the fiber bundle from the light source.
Modern medical imaging systems implement the above-described versatility of endoscopic or open surgery imaging with various telescopes and exoscopes for different applications that can be attached to the system's camera head, which is controlled by a central control unit (CCU). The telescopes and endoscopes may have an illumination light connector to be connected to an illumination light generating unit of the medical imaging system via light fibers. Such systems may furthermore implement fluorescence imaging for fluorescence imaging guided surgery.
Fluorescence imaging is a form of molecular imaging, which generally encompasses imaging methods for visualizing and/or tracking of molecules having specific properties that are used for molecular imaging. Such molecules can be substances that are endogenous to the body, or dyes or contrast agents that are injected into the patient. MRI and CT, for example, therefore, also fall under the term “molecular imaging”. Fluorescence imaging as a variant of molecular imaging uses the property of certain molecules (fluorophores), which emit light of certain wavelengths when excited/absorbed by light of certain wavelengths.
For the purpose of fluorescence imaging, the system's camera head includes sensors that are sensitive in the visible spectrum and in the near infrared spectrum, with wavelengths between ca. 400 nm and ca. 1.000 nm, while the system's illumination light generating unit has a light source for white light to illuminate the operating area with white light as well as at least one excitation light source designed to illuminate the operating area with light that includes an excitation wavelength capable of exciting a fluorescent substance or dye that has been injected into the operating area, to return fluorescence emission. The excitation light source may comprise a laser or a light emitting diode, the wavelength depending on the dye used. For indocyanine green (ICG), e.g., which emits fluorescence light between 750 nm and 950 nm, an excitation wavelength may be between 600 nm and 800 nm. After being excited, the dyes shed the excitation energy by emitting light at slightly longer wavelengths than that of the excitation light. Other wavelengths may be used as excitation wavelengths depending on the type of dye used. This can include wavelengths that are further inside the visible spectrum.
While the above-described exoscopes are useful for documenting open surgery, their usefulness for fluorescence imaging in open surgery is limited due to their relatively small distal aperture, limiting the amount of light, in particular the weak fluorescence light, they can take in and transfer to the image sensor or image sensors of the optical system.
An object is to provide improved means for fluorescence imaging in open surgery.
Such object can be solved by an attachment optics for a camera head for fluorescence imaging in open surgery, with an optical system comprising, in progression from distal to proximal, a distal group of two meniscus lenses, of which one is a negative meniscus and the other a positive meniscus, a biplanar glass rod and single meniscus lens, wherein the two meniscus lenses of the distal group of meniscus lenses are made from different glass types having Abbé numbers γ1, γ2 with
Such an attachment optics can be configured to be attached to a camera head of a medical imaging system. Since the camera head has its own imaging optics, the attachment optics, which can be comparable to a head lens, can be attached to the camera head's cone adapter that provides the combined optical system of the attachment lens system and the camera head's optical imaging system with the focal length and other optical properties necessary for viewing and recording the operating area.
The imaging optics of the camera head can be configured to have its focus at a location where the typically attached endoscopes project a virtual image to be viewed with the naked eye through the eyepiece. The eyepieces of endoscopes are usually adjusted so that the virtual image can be about one meter in front of the eyepiece (−1 diopter). The exit pupil of the endoscopes can be configured to approximately match the entrance pupil of the camera head. By itself, it is not adapted to provide a suitable overview of the operating area in open surgery. The optical system of the attachment optics, or “head lens”, decreases the focal length of the combined optical system of head lens and camera head and thereby enlarges its field of view, without introducing noticeable optical aberrations that worsen optical performance, thus rendering it suitable for observing and imaging the operating field. The rather simple combination of a distal group or pair of meniscus lenses, a biplanar glass rod and a proximal meniscus lens provides this longer focus in front of the camera head optics system.
In the attachment optics' optical system, glass types, thicknesses and radii of the surfaces of the meniscus lenses can be chosen appropriately for the desired optical specifications of the system, such as the desired focal length, which can be done by specialists with the aid of dedicated simulation software. With the optical system as described above, the number of variables can be quite manageable.
Still, since the optical system can be used for a wide range in the optical wavelengths to be transmitted, ranging from the visible spectrum to the near infrared, it can be challenging to avoid optical aberrations, such as chromatic aberrations, within the wide wavelength range. Best results are obtained if the Abbé numbers and refractive indices of the glass types used for the two meniscus lenses of the distal group are not too different, as expressed in the above-listed in equations. One of the meniscus lenses of the distal group being a positive meniscus lens, i.e., being thicker at the center than at the edges, and the other one being a negative meniscus lens, i.e., being thinner at the center than at the edges, ensures that chromatic aberrations can be compensated more accurately and finely.
Furthermore, since the attachment optics can be attached to a camera head and to be used to observe an operating field during open surgery from a distance, the optical system can be on the one hand compact, on the other hand to have a larger entrance pupil in order to get higher resolution and brightness. This optimization can be expressed in the inequation relating the focal length F and diameter D of the largest diameter meniscus lens of the distal group.
The two meniscus lenses of the distal group can be kitted together, thereby providing stability and easy assembly.
In embodiments, the two meniscus lenses of the distal group can have identical radii of curvature R2 at their common interfacing surfaces. Having identical radii of curvature at their common interfacing surfaces can have several advantages, including reducing of the number variables in the optimization of the optical properties during development and the ease of assembly, since the two interfacing surfaces fit together perfectly and can be easily kitted, if kitting is performed.
In embodiments, the distal one of the two meniscus lenses of the distal group can have a distal surface with radius of curvature R1, the proximal one of the two meniscus lenses of the distal group can have a proximal surface with radius of curvature R3, wherein one or both of the following conditions (1) and (2) are met:
Keeping these inequations during development and optimization of the optical system, where R2 is, again, the identical radius of curvature of the common interfacing surfaces of the two meniscus lenses of the distal group, can further narrow down the available phase space of optical parameters in a way that ensures that the first meniscus lens of the distal group can be a negative meniscus (thinner in the center) and its second meniscus lens a positive meniscus (thicker in the center), thus ensuring that a proper balance can be reached between diverse optical aberrations. Off-axis aberrations, like astigmatism and lateral chromatic aberration, can be reduced effectively in this configuration.
In a further embodiment, the single meniscus lens proximal of the biplanar glass rod can have a distal surface with radius of curvature R4 and a proximal surface with radius of curvature R5, wherein the following condition (3) is met:
This configuration can ensure that the proximal meniscus lens is a positive meniscus, that proper focusing characteristics are reached and that the incident angle of rays on the surface R4 are reduced in order to reduce the optical aberrations caused by nonlinear effects, e.g., spherical aberration and coma aberration.
The optical system can be integrated into a housing adapted to be attached to a camera head by a releasable fixture mechanism in embodiments. Such releasable fixture mechanism can be a locking or clamping mechanism and can be based on the same configuration and principle as the one used for attaching an endoscope or exoscope to the camera head.
Furthermore, the housing can be equipped with a light source or with a light guide, such as light guiding fibers or one or more solid light guides, configured for illuminating an operating field distal of the housing. Such light guide can provide lighting at a front face of the attachment optics, e.g. in the form of a ring light surrounding the optical system of the attachment optics for even and shadow-free illumination of the operating field.
In further embodiments, the meniscus lens of the distal group situated adjacent to the biplanar glass rod can be attached to the biplanar glass rod by direct gluing or by a mask disk coated with glue on both sides and having a central aperture. The glue can be a transparent optical glue or another glue that may not be transparent. In direct gluing as well as in using a mask disk, glue can only be applied to the circumferential region where there can be direct contact between the opposing surfaces of the meniscus lens and the biplanar rod. In the case of the mask disk as well as if nontransparent glue is used, stray light can be minimized while simultaneously not limiting the overall optical performance of the system.
Similarly, in a further embodiment, the single meniscus lens can be attached to the biplanar glass rod by direct gluing or by a mask disk coated with glue on both sides and having a central aperture. Again, stray light can be eliminated, thereby enhancing the optical performance.
The outer diameter can be chosen such as to cover at least the outer diameter of the adjacent meniscus lens. In order to more effectively eliminate stray lights, the mask disk in embodiments can have an outer diameter equal to between 95% and 100% of an outer diameter of the biplanar glass rod.
In embodiments, a distal one of the two meniscus lenses of the distal group and the biplanar glass rod can have the same diameter or similar diameters that deviate from each other by less than 5%. In embodiments, the single meniscus lens can have a diameter that can be between 60% and 100%, such as between 95% and 100%, of the diameter of the biplanar glass rod. These ranges include their end points. Keeping the same or very similar diameters, the attachment optics can have a basically cylindrical shape from front to back, making it easy to handle and center.
Such object can also be achieved by a system for fluorescence imaging in open surgery, comprising a controller comprising hardware, a camera head connected to and controlled by the controller and an above-described attachment optics for fluorescence imaging in open surgery, the camera head and the attachment optics being attached to one another. The system thereby incorporates all features, advantages and characteristics of the above-described attachment optics.
In embodiments of the system, at least one of the controller, the camera head, the attachment optics and a separate lighting unit can be configured to produce illumination light for fluorescence imaging, such as to be emitted by the attachment optics. Such lighting can include both white illumination lighting and fluorescence excitation lighting for a predetermined selection of fluorescent dyes to be used during fluorescence imaging guided endoscopic and/or open surgery. Fluorescence excitation lighting can be generated by narrow band light sources such as LEDs or appropriately configured or tuned lasers in the far red or near infrared range, but also in the visible spectrum for fluorophores that are excited and emit fluorescence light in the visible spectrum.
Further features will become evident from the description of embodiments, together with the claims and the appended drawings. Embodiments can fulfill individual features or a combination of several features.
The embodiments described below, without restricting the general intent of the invention, based on exemplary embodiments, wherein reference is made expressly to the drawings with regard to the disclosure of all details that are not explained in greater detail in the text.
In the drawings:
In the drawings, the same or similar types of elements or respectively corresponding parts are provided with the same reference numbers in order to prevent the item from needing to be reintroduced.
In order to illuminate the operating area 70 when observing it, the exoscope 2 further comprises illumination optics configured to guide light from the illumination light source unit 5 to an exoscope tip 21 of the exoscope 2. To this end, the light source unit 5, which is further described with reference to
Since the camera head 100 is configured to receive telescope type endoscopes with eyepieces (ocular cones), its adapter 104 may be configured to receive such eyepieces. The imaging optics is configured to have its focus at a location where the typically attached endoscopes project a virtual image to be viewed with the naked eye through the eyepiece. The eyepieces of endoscopes are usually adjusted so that the virtual image is about one meter in front of the eyepiece (−1 diopter). The exit pupil of the endoscopes is configured to approximately match the entrance pupil of the camera head and is located about 7 mm behind the edge of the eyepiece funnel, which is typically inside adapter 104 in the attached state.
The fluorescence imaging adapter 110 provides a head lens or attachment lens in the form of a head lens system 112 having one or more individual lenses whose function it is to change the properties of the imaging optics of camera head 100, thus rendering the camera head 100 capable of viewing the operating field. This is be done, e.g., by decreasing the focal length of the camera head 100 and thereby enlarging its field of view. The fluorescence imaging adapter has a standardized ocular cone 114 on its rear side for the purpose of connecting to the adapter 104 of camera head 100. Furthermore, the fluorescence imaging adapter 110 is equipped with a light guide cable 116 leading towards its front surface 113. The other end of the light guide cable 116 may be connected to an illumination light source unit 5 as shown in
A first exemplary embodiment having a focal length F of 762 mm is shown in the following Table 1 (all units in mm):
In Table 1, each line represents a specific location, starting with an object “Object”, such as an operating field 70. At a distance (“Thickness”) of 200 mm behind this object the distal surface (“1”) of the distal meniscus lens 124 of
Lines “6” and “7” denote the distal and proximal surfaces of the single proximal meniscus lens 130.
This optical system is followed by a camera head, whose optical characteristics are not given in Table 1 but are known when calculating and optimizing attachment optics for a specific camera head.
A second exemplary embodiment having a focal length F of 205 mm is shown in the following Table 2 (all units in mm):
This optical system, calculated for a different camera head having a slightly longer focal length, is more compact than the first exemplary embodiment, both in length and in diameter.
Generally the solid lines represent MTF in the tangential direction, the dashed lines represent MTF in the sagittal direction. MTF 210 represented by a dotted line represents the theoretical ideal case of a diffraction-limited system. As can be seen in
Line 200 denotes the MTF in the center of the image plane, which is the same in the sagittal and tangential directions, and is very close to the theoretical optimum. Lines 202 and 204 denote the MTF at 80% image size in the tangential and sagittal directions, respectively, lines 206 and 208 the MTF at 100% image size, i.e., at the far edge. As can be seen, the MTF stays close to the ideal values in the sagittal direction, whereas it is significantly worse in the tangential direction in both cases.
In the case of the optical system 112 of the attachment optics, shown in
While there has been shown and described what is considered to be embodiments of the invention, it will, of course, be understood that various modifications and changes in form or detail could readily be made without departing from the spirit of the invention. It is therefore intended that the invention be not limited to the exact forms described and illustrated, but should be constructed to cover all modifications that may fall within the scope of the appended claims.
The present application is based upon and claims the benefit of priority from U.S. Provisional Application No. 63/444,626 filed on Feb. 10, 2023, the entire contents of which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63444626 | Feb 2023 | US |
