A photoacoustic endoscope system

Abstract

The present invention relates to a multi-fiber laser sensor-based photoacoustic endoscope system (1) which is obtained by inscribing fiber grating structures with different reflection wavelengths into multicore fibers for generating three-dimensional images of veins / tissues (X).

Description

[0001] A PHOTOACOUSTIC ENDOSCOPE SYSTEM

[0002] Technical Field

[0003] The present invention relates to a multi-fiber laser sensor-based photoacoustic endoscope system which is obtained by inscribing fiber grating structures with different reflection wavelengths into multicore fibers for generating three- dimensional images of veins / tissues.

[0004] Background of the Invention

[0005] Detection of ultrasonics is a fundamental technique for engineering applications. Optical fiber hydrophones (underwater fiber optical acoustic sensors typically operating at frequencies of <10 kHz) have played an important role in the last twenty years as an alternative to existing piezoelectric sensors due to their high sensitivity, immunity to electromagnetic interference and multiplexing capacity. Interferometric fiber hydrophones with schematics containing Mach-Zehnder, Sagnac or Michelson interferometers have been applied with high sensitivity by taking advantage of the advantages of phase detection. A sensor array can be generated with tens or hundreds of such sensors. Sensor with Extrinsic Fabry- Perot (F-P) structure can detect ultrasonic waves by taking advantage of the pressure-dependent deflection of the diaphragm. Metal-, silicon-based diaphragms and photonic crystal cavities are integrated as pressure-deformable elements at the fiber end. As an alternative, fiber laser hydrophones have shown a great performance in the detection of acoustics. This detection schema can be considered as a derivative of conventional interferometric sensor schemes by placing fiber lasers with a single longitudinal mode at the bare end as detection elements. This detection schema offers great compactness and can maintain intrinsic wavelength multiplexing capacity. Fiber laser sensors can also operate with an alternative coding method. A laser with a sufficiently short cavity length naturally emits monochrome output with two orthogonally polarized modes and provides a pulse signal in the radio frequency field. The pulse signal can respond to external perturbations in terms of frequency variation. On the other hand, the determination of ultrasound waves at frequencies above 1 MHz has been an area of special interest for medical imaging applications. The measurement capacity of conventional piezoelectric sensors is proportional to the detection area. This easily limits applications such as endoscopy where small sensor sizes and high sensitivity are required simultaneously. There is a range of photonic and optical approaches for ultrasound detection that exhibit high sensitivity and small dimensions. Most are based on the detection of the acoustically induced resonance shift of an optical resonator with Fabry-Perot or micro-ring geometry. Taking advantage of the line profile, a high-performance fiber optical ultrasound detector (intrinsic or extrinsic) is required for applications in photoacoustic (PA) endoscopy. Although ultrasonically induced optical delay / birefringence change in an optical fiber was observed decades ago, the application of optical fibers in ultrasonic detection is quite limited. Especially for Photoacoustic Tomography (PAT) and Photoacoustic Microscopy (PAM), the conventional interferometric approach offers relatively poor sensitivity due to the limited effective interaction length. The fiber laser sensor is an important candidate for PAT and PAM as it provides a pressure equivalent to noise of 8-40 Pa over a bandwidth of >50 MHz. Furthermore, the small diameter of the fiber laser, a wide acceptance angle for high-resolution cross-section imaging, and vertical focus can improve sectioning capability and image contrast. Therefore, fiber laser sensors, which can also be focusable, are in an ideal structure to develop a high-resolution linear scanning computed PAT system that provides easy access to patient bodies and high compatibility with handheld ultrasound probes for preclinical / clinical applications. Photoacoustic Imaging (PAI) is a rapidly developing biomedical imaging technology that combines the high contrast of optical imaging with the deep penetration of ultrasound imaging. It is based on the detection of PA signals generated by an acoustic wave that propagates in the medium as a result of a laser- induced thermal expansion process originating from an absorber. PAG, which has rich optical contrast, deep acoustic penetration, high spatial resolution, functional and molecular imaging capabilities, is a hybrid imaging method classified into two main categories: Computerized PAT and PAM.

[0006] In recent years, with the development of new laser and acoustic techniques, PAI has become one of the fastest developing biomedical imaging techniques and has been widely applied in biology, medicine and nanotechnology. However, due to the limited penetration depth of light, it is difficult for PAI to visualize deeply located biological tissues / organ. In addition, the severe attenuation of acoustic waves in air cavities and bones inside rodents enables PAI to be accessible for limited internal tissues / organs. Therefore, the development of photoacoustic endoscopes (PAE), which enable small and targeted regions of interest to be accessed in order to perform imaging of internal tissues / organs, was preferred. The probe design of PAE is more complex than pure optical and acoustic endoscopic probes due to the consideration of acoustic connection and integration. Most of the current PAE systems utilize external scanning mechanisms that are complex and unstable, and the limited optical depth of field severely impacts systemic performance and applicable scenarios of high-resolution photoacoustic imaging.

[0007] The International patent document no. W02022002399, an application included in the state of the art, discloses an endoscope comprising a multicore waveguide, preferably a multicore fiber bundle (MCF). The said multicore waveguide has a distal end and a proximal end. The distal end is directed to a sample to be examined, and the proximal end is kept away from the sample to be examined. The multicore waveguide is selected from the group consisting of a multicore waveguide consisting of individual cores fused in a common cladding and a leached multicore waveguide. Preferably, the system is bending tolerant. Thus, the endoscopic device preferably includes a flexible MCF (multicore fiber) probe that relays the image from the area of interest at the distal fiber side to the proximal side for inspection. The sample to be examined is illuminated with at least one first light source. Preferably, said light source is an LED, preferably with a wavelength in the range of 500-700 nm. The light from the first light source, after having come into contact with the sample to be examined, is coupled into the multicore waveguide and led there through to the proximal end of the thereof, where a first camera is provided. The said camera thus receives the light from said at least one first light source through said multicore waveguide and captures a bright field intensity image of the sample to be examined. The said image is processed in a processing unit, which can be any conventional processing unit such as a desktop computer, laptop etc. Phase imaging can be obtained by generating holographic images of the sample to be examined and using these holographic images for training the DNN.

[0008] Summary of the Invention

[0009] An object of the present invention is to realize a multi-fiber laser sensor-based photoacoustic endoscope system which is obtained by inscribing fiber grating structures with different reflection wavelengths into multicore fibers for generating three-dimensional images of veins / tissues.

[0010] Detailed Description of the Invention

[0011] “A Photoacoustic Endoscope System” realized to fulfil the objective of the present invention is shown in the figures attached, in which:

[0012] Figure 1 is a schematic view of the inventive system. Figure 2 shows the multicore active fiber structures planned to form the fiber laser sensor.

[0013] Figure 3 shows a) tapered conical, b) plane, c) hemispherical concave and d) convex shape of the photoacoustic excitation tips and how these shapes direct the beams sent to the tissue / vein surface.

[0014] The components illustrated in the figures are individually numbered, where the numbers refer to the following:

[0015] 1. Photoacoustic endoscope system

[0016] 2. Multicore active fiber

[0017] 3. Pump laser light source

[0018] 4. Pulsed laser light source

[0019] 5. Fiber optical coupling elements

[0020] 6. Laser combiner

[0021] 7. Fiber laser sensor

[0022] 8. Photoacoustic excitation tip

[0023] 9. Fiber optical isolator

[0024] 10. Polarization controller

[0025] 11. Photo detector

[0026] 12. Signal processing and imaging unit

[0027] 13. Radio frequency spectrum analyzer

[0028] FBG: Fiber bragg grating

[0029] A: Pulsed photoacoustic excitation light

[0030] B : Pump light

[0031] C: Probe light modulated by ultrasonic wave

[0032] D: Optical fiber

[0033] E: Electric cable

[0034] X: Tissue / vein

[0035] Y : Protective cover The inventive multi-fiber laser sensor-based photoacoustic endoscope system (1) which is obtained by inscribing fiber grating structures with different reflection wavelengths into multicore fibers for generating three-dimensional images of veins / tissues (X) and is connected to each other with optical fibers (D) comprises at least one multicore active fiber (2) which has a passive core carrying a marker signal in its center and at least one single-mode active core around which the fiber laser will be generated; at least one pump laser light source (3) which is configured to enable the excitation of multicore active fibers (2); at least one pulsed laser light source (4) which is configured to enable the generation of the acoustic wave through photoacoustic effect by the excitation of the medium whose three-dimensional image will be generated; at least one fiber optical coupling element (5) which is configured to enable the beams (B) coming from the pump laser light source (3) to be transmitted to the vein / tissue (X) medium whose three-dimensional image will be taken and the beams (C) reflected from this medium to be received, and which is located between the pump laser light source (3) and the multicore active fiber (2); at least one laser combiner (6) which is configured to enable different beams (B) coming from the pump laser light source (2) to be directed to each core of the multicore active fiber (MCAF) (2) by gathering them; at least one fiber laser sensor (7) which is located on the multicore active fiber (2) and comprises two fiber Bragg gratings (FBG); at least one photoacoustic excitation tip (8) which is configured to enable the light to be directed 360 degrees and to obtain an instantaneous 3-dimensional image of the internal structure of the vein (X); at least one fiber optical isolator (9) which is configured to enable the light to travel in one direction in the direction of the incidence thereof and to prevent its transmission in the reverse direction; at least one polarization controller (10) which is configured to determine whether the polarization of the laser beam is maintained along the line during the return in order to detect the modulation in the fiber laser cavity created by the acoustic signal detected by the fiber laser sensor (7); at least one photo detector (11) which is configured to enable the light (C) emitted from the polarization controller (10) to be converted into an electrical signal; at least one signal processing and imaging unit (12) which is configured to enable 360-degree 3D images of veins and tissues (X) to be obtained by processing signals from each active fiber laser sensor; and at least one radio frequency spectrum analyzer (13) which is configured to enable the analysis and display of the signal to be detected with microwave frequency that is reduced to the modulated signal microwave (RF) frequency band by filtering while the high-frequency (THz) laser beam (C) modulated by the acoustic wave reflected from the fiber laser sensor (7) to the photo detector (11) is converted into an electrical signal from the photo detector (11).

[0036] The multicore active fiber (2) included in the inventive system (1) is connected at one end to the laser combiner (6) and at the other end to the photoacoustic excitation tip (8). The multicore active fiber (2) has preferably two fiber Bragg gratings (FBG) that form a fiber laser sensor (7) thereon. The signal core diameter of a multicore active fiber (2) may be 100 pm, 125 pm, 250 pm, 400 pm or 600 pm and the diameter of each active core may be in the range of 6-10 pm. The outer diameter of the multicore active fiber (2) may be 250 pm, 400 pm, 600 pm, 625 pm or 875 pm. The centers of the active cores in the multicore active fiber (2) are at a distance of 62.5 pm from the outer surface. The active cores of the multicore active fiber (2) comprise any of highly doped Erbium (Er), Ytterbium (Yb) or Er / Yb atoms. Such fibers have light emission in the 1030-1050 nm or 1540-1560 nm band when excited with light at a wavelength of 915-980 nm. Fiber laser formation is realized in each core within the structure of the multicore active fiber (2). The laser cavity of the multicore active fiber (2) is formed by inscribing fiber Bragg gratings (FBG) into each core. In the formed cavity of the multicore active fiber (2), coherent light is converted into laser beams in the 1030-1050 nm or 1540-1560 nm band by being amplified by multiple reflections and absorptions. In Figure 2, the multicore active fiber (2) structures planned to form fiber laser sensors are shown. In these structures, the structure dimensions change according to the change of the center fiber diameters through which the photoacoustic excitation light will travel.

[0037] The pump laser light source (3) included in the inventive system (1) is a laser source with a wavelength of 915-980 nm. The pump laser light source (3) is configured to operate in continuous wave mode. The pump laser light source (3) is configured in such a way that it has an energy in the mW-W range. The pump laser light source (3) is configured in such a way that it is couplable by free space or optical fiber. Each beam emitted from the pump laser light source (3) is directed to the optical combiner (6) by means of the optical coupling elements (5).

[0038] The beams (A) emitted from the pulsed laser light source (4) included in the inventive system (1) are transmitted directly to the multicore active fiber (2) structure by means of the laser combiner (6) and from there to the medium whose 3 -dimensional image will be taken. The pulsed laser light source (4) is a laser source with any of the wavelengths of 320-405-530-980-1064-1310-1550 nm. The pulsed laser light source (4) operates in pulsed mode and has a pulse width of femtosecond or picosecond or nanosecond. The pulsed laser light source (4) has a pulse energy in the pJ-mJ range. The tissues must be stimulated with pulsed laser beams to create the photoacoustic effect in the medium. High energy beams with a low duty cycle are absorbed by the tissues and a rapid increase in temperature occurs in the medium. Since the laser pulse width is very low, this increase takes place locally without propagating in the medium and then immediate cooling takes place. During heating and cooling, a mechanical sound wave is generated. The generated sound wave contains detailed information about the medium.

[0039] The fiber optical coupling element (5) included in the inventive system (1) is configured to transmit the beams (B) emitted from the pump laser source (3) to the laser combiner (6) and to receive the beams (C) reflected back from the end of the fiber laser sensor (7) from the laser combiner (6) and to transmit them to the fiber optic isolator (9). The fiber optical coupling element (5) can operate as single-mode or multimode. The fiber optical coupling element (5) consists of fiber optic circulators or couplers having 3 or 4 ports. The fiber optical coupling element (5) is configured in such a way to be at least as many as the number of cores of the multicore active fiber (2).

[0040] The laser combiner (6) included in the inventive system (1) is configured in such a way that it has at least as many pump laser inputs as the number of cores from which the fiber laser is to be generated, and at least one signal input for a photoacoustic excitation pulsed laser. The laser combiner (6) is configured in such a way that it enables single-mode (SM) or multimode (MM) fibers to be connected to the pump ends. The laser combiner (6) is configured in such a way that the fiber diameters at the pump and signal input ends are 6-10 pm for singlemode and 100 pm, 125 pm, 250 pm, 400 pm or 600 pm for multimode. The laser combiner (6) is configured in such a way that its output diameter is compatible with the multicore fiber diameter.

[0041] The fiber laser sensor (7) included in the inventive system (1) has two fiber Bragg gratings (FBG) having 1mm- 10cm distance between them, and the fiber Bragg gratings (FBG) are configured in such a way that their reflectivity ratio is 90- 99.9%. The fiber laser sensor (7) is configured in such a way that it is located between the laser combiner (6) and the photoacoustic excitation tip (8). The fiber laser sensor (7) is configured in such a way to be at least as many as the number of cores of the multicore active fiber (2).

[0042] The photoacoustic excitation tip (8) included in the inventive system (1) is configured in such a way that it has a structure that enables the nanosecond pulsed photoacoustic signal to be generated and the excitation laser pulses to be directed to the vein (X) walls that are in line with the fiber laser sensor (7) by back reflection after exiting from the photoacoustic excitation tip (8). By means of this structure, a 3 -dimensional image of the inside of the vein (X) can be obtained without the use of mechanical scanning elements. The photoacoustic excitation tip (8) is located at the end of the multicore active fiber (2) where the laser coupler (6) is not present and is obtained by means of coating a part at the end of the multicore active fiber (2) structure with glass. This part will allow for a wider reflection area by widening the angle of propagation after the light exits the multicore active fiber (2). The glass structure of the photoacoustic excitation tip (8) is produced with any of the materials such as silica, quartz, borosilicate, CaCCh, NaiCCh. A mirror structure is located at the continuation of the glass part of the photoacoustic excitation tip (8) and is configured in such a way that it enables the beams passing through the glass to be reflected back. The end of the mirror structure of the photoacoustic excitation tip (8) is configured to be any of tapered conical, plane, hemispherical concave and convex mirrors. In one embodiment of the invention, the photoacoustic excitation tip (8) is configured to be directly connected to the end of the multicore active fiber (2) without using a glass portion in the case of a tapered conical mirror structure is used. The photoacoustic excitation tip (8) is configured in such a way that it has a cone solid angle (apex angle) in the range of 80°-85° that enables back reflection to occur in a tapered cone-shaped mirror structure. The photoacoustic excitation tip (8) is configured to have a protective structure whose top is made of a biocompatible material, used both to prevent the multicore active fiber (2) tip from being damaged by any impact as it travels through the vein (X) and to prevent the tip from damaging the walls of the vein (X). The photoacoustic excitation tip (8) is configured in such a way that it is attached to the multicore active fiber (2) by means of epoxy adhesives thereof. The photoacoustic excitation tip (8) is configured in such a way that it has protective covers (Y) at its end. By means of the uniquely designed photoacoustic excitation tips (8) shown in Figure 3, the beams sent within the system (1) are reflected back to the parts of the tissues and veins (X) aligned with the laser cavity inscribed in the multicore active fiber (2) and the generated photoacoustic signal is enabled to modulate the light in the laser cavity. Each tip design is customized according to the areas where the light is desired to be reduced.

[0043] The fiber optic isolator (9) included in the inventive system (1) is configured to enable the beams (C) coming from the fiber optical coupling element (5) to go only to the polarization controller (10), and to prevent the beams reflected in the fibers from damaging the pump and pulsed laser light sources (3, 4) by preventing the light from traveling in the reverse direction. The fiber optic isolator (9) is configured in such a way to operate in single-mode or multimode mode. The fiber optic isolator (9) is configured in such a way to be at least as many as the number of cores of the multicore active fiber (2).

[0044] The polarization controller (10) included in the inventive system (1) is configured in such a way that it is in a fiber-couplable format or in a manual or motorized assembly obtained by winding the external fiber on certain spools. The polarization controller (10) is configured in such a way that it is capable of converting linear, circular and elliptical polarized beams into one another. The polarization controller (10) is configured in such a way to be at least as many as the number of cores of the multicore fiber.

[0045] The photo detector (11) included in the inventive system (1) may be composed of different photo diodes and photomultiplier tubes and is configured in such a way to be at least as many as the number of cores of the multicore fiber. The photo detector (11) is in connection with the signal processing and imaging unit (12) and the radio frequency spectrum analyzer (13) by means of the electrical cables (E).

[0046] The signal processing and imaging unit (12) included in the inventive system (1) is configured to enable artificial intelligence and machine learning algorithms to be used in order to increase the resolution of the obtained images. The signal processing and imaging unit (12) is configured to enable the data processing stages and control stages to be applied by the respective processors and to be applied by the respective computer program product / products comprising a computer-usable medium having computer-usable program code that is embodied in the algorithms.

[0047] The radio frequency spectrum analyzer (13) included in the inventive system (1) is configured in such a way that its frequency range is from 1 KHz to 6 GHz. The radio frequency spectrum analyzer (13) is configured in such a way that its signal bandwidth is from IKHz to 1 GHz. The radio frequency spectrum analyzer (13) is configured in such a way that it has an internal AM / FM demodulation. The radio frequency spectrum analyzer (13) is configured in such a way that it has different signal measurement functions. The radio frequency spectrum analyzer (13) is configured in such a way that it has an internal preamplifier.

[0048] Industrial Application of the Invention

[0049] The power supplies of all devices in the inventive system (1) are turned on. The pump laser light source (3) is turned on and the lasers and the cooling system are waited to stabilize (25 °C). After the stability is achieved, the multicore active fibers (2) are excited by the pump laser light source (3). The control of the laser formation in the fiber laser sensor (7) is performed by checking the reflections returning from each multicore fiber (2) with the radio frequency spectrum analyzer (13). For the radio frequency spectrum analyzer (13), the parameters (frequency range, bandwidth, resolution, etc.) required for the laser signal to be visible are adjusted. If the laser cannot be seen, the power values of the pump laser light source (3) are adjusted, and the radio frequency spectrum analyzer (13) continues to be monitored. In order to obtain the rotating signal with maximum amplitude, the polarization of the laser signal is adjusted with the polarization controller (10) and observation is performed in the spectrum formed in the radio frequency spectrum analyzer (13). After the formation of the laser signal, the ns- pulsed laser light source for photoacoustic excitation is introduced into the excitation line of the multicore active fiber (2). The beam intensity and energy emitted from the photoacoustic excitation tip (8) are measured and determined to be sufficient, if not, the power values are increased in the pulsed laser light source (4). It is checked that the beams emitted from the photoacoustic excitation tip (8) provide 360° propagation. After the above-mentioned preliminary checks, the power switches of the light sources are turned off, the endoscope is sent into the body to be imaged, and the light sources are turned on again and waited until the lasers are stable. For in-body measurements, the beams emitted from the photoacoustic excitation tip (8) are absorbed by the tissue and vein (X) walls and the acoustic wave is waited to propagate from the tissue to the fiber laser sensor (7). The acoustic signal modulates the beams of the fiber laser sensor (7). The information about the medium is extracted by demodulating the modulated signal in the signal processing and imaging unit (12). After the medium information is extracted from the modulated signals from each line, these signals are processed and combined with various algorithms in the image processing and imaging unit (12) to obtain raw medium images. Parameters such as contrast and resolution of the images are improved with optimization, machine learning and artificial intelligence techniques to obtain high resolution medium images. Obtained final images are displayed through a computer interface.

[0050] Within these basic concepts; it is possible to develop various embodiments of the inventive “A Photoacoustic Endoscope System (1)”; the invention cannot be limited to examples disclosed herein and it is essentially according to claims.

Claims

CLAIMS1. A multi-fiber laser sensor-based photoacoustic endoscope system (1) which is obtained by inscribing fiber grating structures with different reflection wavelengths into multicore fibers for generating three-dimensional images of veins / tissues (X) and is connected to each other with optical fibers (D); characterized in that it comprises at least one multicore active fiber (2) which has a passive core carrying a marker signal in its center and at least one single-mode active core around which the fiber laser will be generated; at least one pump laser light source (3) which is configured to enable the excitation of multicore active fibers (2); at least one pulsed laser light source (4) which is configured to enable the generation of the acoustic wave through photoacoustic effect by the excitation of the medium whose three-dimensional image will be generated; at least one fiber optical coupling element (5) which is configured to enable the beams (B) coming from the pump laser light source (3) to be transmitted to the vein / tissue (X) medium whose three-dimensional image will be taken and the beams (C) reflected from this medium to be received, and which is located between the pump laser light source (3) and the multicore active fiber (2); at least one laser combiner (6) which is configured to enable different beams (B) coming from the pump laser light source (2) to be directed to each core of the multicore active fiber (MCAF) (2) by gathering them; at least one fiber laser sensor (7) which is located on the multicore active fiber (2) and comprises two fiber Bragg gratings (FBG); at least one photoacoustic excitation tip (8) which is configured to enable the light to be directed 360 degrees and to obtain an instantaneous 3-dimensional image of the internal structure of the vein (X); at least one fiber optical isolator (9) which is configured to enable the light to travel in one direction in the direction of the incidence thereof and to prevent its transmission in the reverse direction;at least one polarization controller (10) which is configured to determine whether the polarization of the laser beam is maintained along the line during the return in order to detect the modulation in the fiber laser cavity created by the acoustic signal detected by the fiber laser sensor (7); at least one photo detector (11) which is configured to enable the light (C) emitted from the polarization controller (10) to be converted into an electrical signal; at least one signal processing and imaging unit (12) which is configured to enable 360-degree 3D images of veins and tissues (X) to be obtained by processing signals from each active fiber laser sensor; and at least one radio frequency spectrum analyzer (13) which is configured to enable the analysis and display of the signal to be detected with microwave frequency that is reduced to the modulated signal microwave (RF) frequency band by filtering while the high-frequency (THz) laser beam (C) modulated by the acoustic wave reflected from the fiber laser sensor (7) to the photo detector (11) is converted into an electrical signal from the photo detector (11).

2. A photoacoustic endoscope system (1) according to Claim 1; characterized by the multicore active fiber (2) which is connected at one end to the laser combiner (6) and at the other end to the photoacoustic excitation tip (8).

3. A photoacoustic endoscope system (1) according to Claim 1 or 2; characterized by the multicore active fiber (2) which has two fiber Bragg gratings (FBG) that form a fiber laser sensor (7) thereon.

4. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the multicore active fiber (2) whose signal core diameter is 100 pm, 125 pm, 250 pm, 400 pm or 600 pm; each active core diameter is in the range of 6-10 pm; outer diameter is 250 pm, 400 pm, 600 pm, 625 pm or 875 pm.

5. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the multicore active fiber (2) whose centers of the active cores are at a distance of 62.5 pm from the outer surface.

6. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the multicore active fiber (2) whose active cores comprise any of highly doped Erbium (Er), Ytterbium (Yb) or Er / Yb atoms.

7. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the multicore active fiber (2) in which fiber laser formation is realized in each core within its structure.

8. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the multicore active fiber (2) whose laser cavity is formed by inscribing fiber Bragg gratings (FBG) into each core.

9. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the multicore active fiber (2) which enables coherent light to be converted into laser beams in the 1030-1050 nm or 1540-1560 nm band by being amplified by multiple reflections and absorptions in the formed cavity.

10. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the pump laser light source (3) which is a laser source with a wavelength of 915-980 nm; operates in continuous wave mode; and is configured in such a way that it has an energy in the mW-W range.

11. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the pump laser light source (3) which is configured in such a way that it is couplable by free space or optical fiber.

12. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the pump laser light source (3) which enables each emitted beam to be directed to the optical combiner (6) by means of optical coupling elements (5).

13. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the pulsed laser light source (4) which enables the emitted beams (A) to be transmitted directly to the multicore active fiber (2) structure by means of the laser combiner (6) and from there to the medium whose 3 -dimensional image will be taken.

14. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the pulsed laser light source (4) which is a laser source with any of the wavelengths of 320-405-530-980-1064-1310-1550 nm.

15. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the pulsed laser light source (4) which operates in pulsed mode; has a pulse width of femtosecond or picosecond or nanosecond; and whose pulse energy is in the pJ-mJ range.

16. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the fiber optical coupling element (5) which is configured to transmit the beams (B) emitted from the pump laser source (3) to the laser combiner (6) and to receive the beams (C) reflected back from the end of the fiber laser sensor (7) from the laser combiner (6) and to transmit them to the fiber optic isolator (9).

17. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the fiber optical coupling element (5) which can operate as single-mode or multimode; consists of fiber optic circulators or couplers having3 or 4 ports; and is configured in such a way to be at least as many as the number of cores of the multicore active fiber (2).

18. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the laser combiner (6) which is configured in such a way that it has at least as many pump laser inputs as the number of cores from which the fiber laser is to be generated, and at least one signal input for a photoacoustic excitation pulsed laser.

19. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the laser combiner (6) which is configured in such a way that it enables single-mode (SM) or multimode (MM) fibers to be connected to the pump ends.

20. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the laser combiner (6) which is configured in such a way that the fiber diameters at the pump and signal input ends are 6-10 pm for- single mode and 100 pm, 125 pm, 250 pm, 400 pm or 600 pm for multimode.

21. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the laser combiner (6) which is configured in such a way that its output diameter is compatible with the multicore fiber diameter.

22. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the fiber laser sensor (7) which has two fiber Bragg gratings (FBG) having 1mm- 10cm distance between them, and the fiber Bragg gratings (FBG) are configured in such a way that their reflectivity ratio is 90- 99.9%.

23. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the fiber laser sensor (7) which is configured in such away that it is located between the laser combiner (6) and the photoacoustic excitation tip (8) and to be at least as many as the number of cores of the multicore active fiber (2).

24. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the photoacoustic excitation tip (8) which is configured in such a way that it has a structure that enables the nanosecond pulsed photoacoustic signal to be generated and the excitation laser pulses to be directed to the vein (X) walls that are in line with the fiber laser sensor (7) by back reflection.

25. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the photoacoustic excitation tip (8) which is located at the end of the multicore active fiber (2) where the laser coupler (6) is not present and is obtained by means of coating a part at the end of the multicore active fiber (2) structure with glass.

26. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the photoacoustic excitation tip (8) whose glass structure is produced with any of the materials such as silica, quartz, borosilicate, CaCO3, Na2CO3.

27. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the photoacoustic excitation tip (8) where a mirror structure is located at the continuation of the glass part thereof and is configured in such a way that it enables the beams passing through the glass to be reflected back.

28. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the photoacoustic excitation tip (8) whose mirrorstructure end is configured to be any of tapered conical, plane, hemispherical concave and convex mirrors.

29. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the photoacoustic excitation tip (8) which is configured to be directly connected to the end of the multicore active fiber (2) without using a glass portion in the case of a tapered conical mirror structure is used.

30. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the photoacoustic excitation tip (8) which is configured in such a way that it has a cone solid angle (apex angle) in the range of 80°-85° that enables back reflection to occur in a tapered cone-shaped mirror structure.

31. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the photoacoustic excitation tip (8) which is configured to have a protective structure whose top is made of a biocompatible material, used both to prevent the multicore active fiber (2) tip from being damaged by any impact as it travels through the vein (X) and to prevent the tip from damaging the walls of the vein (X).

32. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the photoacoustic excitation tip (8) which is configured in such a way that it is attached to the multicore active fiber (2) by means of epoxy adhesives thereof.

33. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the photoacoustic excitation tip (8) which is configured in such a way that it has protective covers (Y) at its end.

34. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the fiber optical isolator (9) which is configured toenable the beams (C) coming from the fiber optical coupling element (5) to go only to the polarization controller (10), and to prevent the beams reflected in the fibers from damaging the pump and pulsed laser light sources (3, 4) by preventing the light from traveling in the reverse direction.

35. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the fiber optical isolator (9) which is configured in such a way to operate in single-mode or multimode mode; and to be at least as many as the number of cores of the multicore active fiber (2).

36. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the polarization controller (10) which is configured in such a way that it is in a fiber-couplable format or in a manual or motorized assembly obtained by winding the external fiber on certain spools.

37. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the polarization controller (10) which is configured in such a way that it is capable of converting linear, circular and elliptical polarized beams into one another; and to be at least as many as the number of cores of the multicore fiber.

38. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the photo detector (11) which may be composed of different photo diodes and photomultiplier tubes; and is configured in such a way to be at least as many as the number of cores of the multicore fiber.

39. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the photo detector (11) which is in connection with the signal processing and imaging unit (12) and the radio frequency spectrum analyzer (13) by means of the electrical cables (E).

40. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the signal processing and imaging unit (12) which is configured to enable artificial intelligence and machine learning algorithms to be used in order to increase the resolution of the obtained images.

41. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the signal processing and imaging unit (12) which is configured to enable the data processing stages and control stages to be applied by the respective processors and to be applied by the respective computer program product / products comprising a computer-usable medium having computer-usable program code that is embodied in the algorithms.

42. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the radio frequency spectrum analyzer (13) which is configured in such a way that its frequency range is from 1 KHz to 6 GHz; and that its signal bandwidth is from IKHz to 1 GHz.

43. A photoacoustic endoscope system (1) according to any one of the preceding claims; characterized by the radio frequency spectrum analyzer (13) which is configured in such a way that it has an internal AM / FM demodulation, different signal measurement functions and an internal preamplifier.

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