Vein imaging device and vein imaging method

Abstract

To visualize a blood vessel to allow assessing the state of a vein without using a contrasting agent such as indocyanine green (ICG).SOLUTION: The present invention provides a vein imaging device comprising illumination and a near-IR camera. The illumination radiates light having a wavelength belonging to a range of 1040 nm to 1100 nm inclusive. The near-IR camera has a semiconductor light-receiving element array in which potential barriers are formed between adjacent elements, and detects reflected light from the light having a wavelength belonging to a range of 1040 nm to 1100 nm inclusive, radiated by the illumination.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a vein imaging device and a vein imaging method for visualizing the state of veins. [Background technology]

[0002] Patent documents 1 to 12 disclose technologies relating to devices, imaging systems, and image display systems that display veins by imaging the body surface, with the aim of depicting blood vessels with a diameter of approximately 5 mm that are large enough to serve as routes for administering medicines or taking blood, and also provide information on lighting, cameras, and imaging systems suitable for this technology.

[0003] Devices have been developed to improve the visibility of subcutaneous veins that are thick enough to serve as routes for drug administration or blood sampling. Patent documents 1 to 3 describe devices for visualizing veins. These devices detect veins located up to 10 mm deep from the epidermis and project the course of veins that can be used as routes for drug administration or blood sampling directly onto the skin surface in real time. Each device emits near-infrared light with a wavelength of 900 nm or less, and an array detector captures the light absorbed by hemoglobin in the blood and the light reflected by the surrounding tissue. A computer processes the detection results using an image enhancement algorithm to generate a digitally enhanced grayscale image. A projector then displays the location information of veins that can be used as routes for drug administration or blood sampling on the skin surface.

[0004] The devices based on Patent Documents 1 and 2 capture blood vessels that serve as routes for drug administration and blood sampling by enhancing the contrast between veins and the surrounding interstitium. The device based on Patent Document 3 also enables exactly the same thing as the devices based on Patent Documents 1 and 2.

[0005] The devices and methods for visualizing subcutaneous blood vessels based on Patent Documents 1 to 3 use near-infrared light and a conventional silicon CCD for its detection, as shown in Patent Document 4. Near-infrared light and its detection using a conventional silicon CCD is used to visualize the course of veins using a near-infrared light wavelength range of 700 to 900 nm, as shown in Patent Document 5, and assists in procedures targeting veins, such as drug administration and blood sampling, as shown in Patent Document 6.

[0006] Patent Documents 5 and 6 refer to subcutaneous veins with a diameter of less than 1 mm, which cannot be used as a route for drug administration or blood collection, as "venules." The smallest needles used for general blood collection and drug administration are 24-gauge needles (outer diameter 0.46±0.02 mm) to 26-gauge needles (outer diameter 0.56±0.02 mm), but they are difficult to insert accurately into venules. In addition, administering a sufficient amount of drug is also difficult. Furthermore, the collected blood is hemolyzed, making them difficult to use for blood collection. For these reasons, the devices based on Patent Documents 1 to 3 do not display veins with a diameter of approximately 1 mm on the skin surface using a projector.

[0007] A conventional silicon CCD camera can be used to visualize veins in the subcutaneous tissue that are large enough to serve as a route for drug administration or blood sampling (veins with a diameter exceeding 1 mm and suitable for drug administration or blood sampling). In this case, as shown in Patent Document 7, for example, using a filter that transmits light with wavelengths of 650 to 1100 nm can improve visibility.

[0008] Patent Document 8 provides a device used when inserting an injection needle for the purpose of blood collection, etc. Patent Document 8 describes that the use of illumination with a wavelength of 600 to 1200 nm improves the visibility of blood vessels large enough to serve as routes for drug administration or blood collection, or veins large enough to be inserted with an injection needle.

[0009] Patent Document 9 discloses a means for visualizing veins with a diameter that can be punctured with an injection needle, which can serve as a route for administering medicines or collecting blood. Patent Document 9 indicates that in a device using a conventional silicon CCD camera, administering ICG (indocyanine green) or the like to visualize the veins is useful for detecting blood vessels that meet the purpose.

[0010] Patent Document 10 shows that when a conventional silicon CCD camera, which is used to detect veins that can be punctured with an injection needle and serve as a route for administering medicine or drawing blood, uses light with a wavelength of 1100 nm as illumination, the light absorption efficiency of the silicon responsible for photoelectric conversion becomes close to zero. Patent Document 10 also discloses that imaging in the wavelength range exceeding 1000 nm requires the use of a sensor equipped with InGaAs, InSb, or HgCdTe focal plane arrays.

[0011] Patent Document 11 discloses one form of a method for measuring blood flow using the magnitude of light scattering caused by the movement of red blood cells in the bloodstream. More specifically, the method of Patent Document 11 extracts information derived from red blood cells moving within microvessels from the Doppler shift detected in an area where the shape of blood vessels cannot be visualized, among the Doppler shifts caused by scattering of laser light irradiated onto the epidermis, and determines the state of peripheral blood flow.

[0012] Patent Document 12 detects the difference in optical absorption between heme and oxidized heme contained in muscle tissue and blood vessels using light at wavelengths of 740, 780, 850, and 940 nm. Patent Document 12 calculates oxygen saturation without distinguishing between intramuscular and intravascular oxygen saturation, and presents a tissue oxygen saturation map based on the course of blood vessels with a diameter of approximately 5 mm used for drug administration. However, the oxygen saturation is calculated without providing the positional information of blood vessels with a diameter of approximately 1 mm that are not used for drug administration. The oxygen saturation used in Patent Document 12 is the sum of values ​​derived from veins, which are the route for drug administration and blood collection, and values ​​derived from myoglobin present in muscle cells and myofibroblasts that make up the interstitium.

[0013] Light with wavelengths of 1000 to 1300 nm has lower optical absorption and tissue scattering than light with wavelengths less than 1000 nm, and is less attenuated, allowing it to reach deeper subcutaneous tissue. Non-Patent Document 1 introduces glucose concentration measurements in the skin and subcutaneous tissue using wavelengths greater than 1000 nm. Non-Patent Document 1 shows the results of measurements of tissue penetration of light with wavelengths of 1000 to 1300 nm. Historically, modules for measuring optical absorption of glucose in the near-infrared wavelength range greater than 1000 nm (over 1000 nm wavelength range) have often been made with InGaAs elements (Non-Patent Document 2). Non-Patent Document 1 uses InGaAs elements to measure the optical absorption of glucose, which has weaker optical absorption than hemoglobin, and calculates the glucose concentration.

[0014] Non-Patent Document 3 explains non-invasive bioinstrumentation methods that capture various biological phenomena inside the body by observing them from outside the body. Non-Patent Document 3 introduces the potential of spectroscopic measurement technology that uses light with wavelengths of 700 to 900 nm, which is less scattered and absorbed by interstitial tissues, as a non-invasive bioinstrumentation method that uses light.

[0015] A specific example of a non-invasive bioinstrumentation method using light is the pulse oximeter, which measures the oxygen saturation of arterial blood using wavelengths in the 700-900 nm range, where absorption differs depending on the oxygenated and deoxygenated states of hemoglobin.

[0016] Glucose values ​​measured by non-invasive bioinstrumentation methods can be judged to be related to blood glucose levels if they are derived from an area where venous flow is captured as an image. In contrast, glucose values ​​derived from an area where venous flow cannot be captured are mostly derived from adipocytes, fibrocytes, muscle cells, myofibroblasts, and interstitial tissue fluid, taking into account the area occupied by this area, and are judged to have little contribution from the concentration of sugar present in venules and capillaries.

[0017] Non-Patent Document 4 presents data showing that silicon charge-coupled device (CCD) cameras are insensitive in the wavelength range of 1000 to 1350 nm, and clarifies that the quantum efficiency of InGaAs cameras is superior to that of silicon cameras in the wavelength range longer than 900 nm. Non-Patent Document 4 also concludes that the wavelength range of 1000 to 1350 nm is the second window suitable for biological imaging.

[0018] Non-patent document 5 shows that single-walled carbon nanotubes emit fluorescence at wavelengths longer than 1080 nm, and that by administering them into the blood vessels of mice, angiography can be performed, and that by observing them from outside the body using an InGaAs camera, the aorta located deep within the body can be visualized.

[0019] Non-Patent Documents 4 and 6 present fluorescent substances that can be used for imaging at wavelengths of 1050 nm or longer, including rare-earth-containing ceramic nanoparticles, quantum dots, single-walled carbon nanotubes, and low-molecular-weight organic fluorescent dyes. However, there are no reports of successful video imaging.

[0020] Patent Document 13 discloses a technology that supports the identification of biological tissues by using an illumination unit that emits light at multiple wavelengths in the infrared region and an infrared camera that is sensitive to light at wavelengths in the infrared region. Patent Document 14 discloses a technology related to a compound semiconductor light-receiving element array that reduces crosstalk between adjacent elements. Non-Patent Document 7 discloses blood tests for D-dimers and the like, and ultrasonic Doppler testing for thrombi formed in large veins. [Prior art documents] [Patent documents]

[0021] [Patent Document 1] U.S. Patent No. 5,969,754 [Patent Document 2] U.S. Patent No. 6,556,858 [Patent Document 3] U.S. Patent No. 8,463,364 [Patent Document 4] U.S. Patent No. 4,817,622 [Patent Document 5] U.S. Patent No. 5,519,208 [Patent Document 6] U.S. Patent No. 5,608,210 [Patent Document 7] US Patent Application Publication No. 2003 / 0018271 [Patent Document 8] Japanese Patent Application Laid-Open No. 2004-237051 [Patent Document 9] U.S. Patent No. 6,178,340 [Patent Document 10] US Patent Application Publication No. 2009 / 0018414 [Patent Document 11] U.S. Patent No. 6,263,227 [Patent Document 12] U.S. Patent No. 9,968,285 [Patent Document 13] International Publication No. 2014 / 192876 [Patent Document 14] International Publication No. 2011 / 089949 [Non-patent literature]

[0022] [Non-Patent Document 1] Maruo, K., et al., Noninvasive blood glucose using a newly developed near-infrared assay system. Ieee Journal of Selected Topics in Quantum Electronics, 2003. [Non-patent document 2] Nishimura, I. Prospects for near-infrared biospectroscopy - Potential of the 1 μm wavelength range. Angiology: Journal of the Japanese College of Angiology, 2009. [Non-patent document 3] Iwane, H. and T. Hamaoka, Measurement of in vivo oxygen dynamics using near-infrared spectroscopy. Physical Fitness and Sports Science, 1995. [Non-patent document 4] Smith, AM, MC Mancini, and S. Nie, Bioimaging: second window for in vivo imaging. Nat Nanotechnol, 2009. [Non-patent document 5] Iizumi, Y., et al., Oxygen-doped carbon nanotubes for near-infrared fluorescent labels and imaging probes. Sci Rep, 2018. [Non-patent document 6] Uemura, M. and Soga, K.: Development of in vivo imaging method using near-infrared fluorescent probes. Analysis, 2019. [Non-Patent Document 7] Ackermann, M., et al., Pulmonary Vascular Endothelialitis, Thrombosis, and Angiogenesis in Covid-19. N Engl J Med, 2020. Summary of the Invention [Problem to be solved by the invention]

[0023] The Doppler method is used to measure blood flow in real time, but this is a tomographic imaging method that requires a blood vessel diameter of approximately 5 mm, and blood flow cannot be measured in venules less than 1 mm in diameter because they cannot be imaged.

[0024] To evaluate whether microthrombi are formed and grow, a technique that allows continuous observation over a period of several minutes to several hours is required. Evaluation of vascular blood flow using indocyanine green (ICG) angiography can be used for this purpose. However, to prevent side effects of ICG, the administration dose must be kept as low as possible. Furthermore, because ICG is washed away by the bloodstream, observation with a single shot lasts only a few seconds. Therefore, a technique that allows continuous observation over a period of several minutes to several hours is further needed.

[0025] In ICG angiography, a silicon camera is used to detect fluorescence at a wavelength of 835 nm. However, the silicon camera is sensitive to light from fluorescent lamps and LED lighting used in indoor lighting, making it difficult to obtain good images of blood vessels less than 1 mm in diameter without using a darkroom or other light-blocking techniques.

[0026] Furthermore, it is impossible to accurately capture blood vessels less than 1 mm in diameter using an indwelling needle for continuous infusion of ICG solution. For this reason, ICG is usually administered into larger blood vessels and visualized as it flows into peripheral blood vessels less than 1 mm in diameter. Therefore, the observation time for peripheral blood vessels less than 1 mm in diameter is limited to a few seconds. There is no method for directly observing or recording the reversible or irreversible increase, decrease, or interruption of blood flow in peripheral blood vessels less than 1 mm in diameter over a period of tens of seconds, minutes, or even hours.

[0027] The spread of novel coronavirus (COVID-19) infection has drawn attention to systemic thrombus formation and its worsening severity, leading to the use of blood tests such as D-dimer and ultrasound Doppler imaging to detect thrombi formed in large veins (Non-Patent Document 7). However, these methods and ICG imaging cannot be used to assess the reduction in blood flow due to thrombus formation in peripheral blood vessels less than 1 mm in diameter, where thrombus formation begins in COVID-19 infection. For this reason, no effective means have been established for monitoring thrombus formation initiated by COVID-19 infection and enabling early diagnosis.

[0028] Thrombotic microangiopathy after bone marrow transplantation, similar to COVID-19 infection, begins with thrombus formation in small venules less than 1 mm in diameter. However, there is no established method for assessing the reduction in blood flow due to thrombus formation. There is a need for a method that can continuously observe and record the vascular status over several hours in peripheral blood vessels less than 1 mm in diameter, where thrombus formation begins, and evaluate the reversible or irreversible dynamics that can be used to determine the pathological condition.

[0029] The wavelength range of 1000–1350 nm is the second window suitable for biological imaging, and the quantum efficiency of InGaAs cameras is superior to that of silicon in this wavelength range. Therefore, for extracorporeal vein observation, imaging with near-infrared light illumination at a wavelength of approximately 1050 nm and an InGaAs camera is superior to imaging with illumination at a wavelength of 900 nm and a silicon camera. Therefore, it has been hoped that imaging with near-infrared light illumination at a wavelength of approximately 1050 nm and an InGaAs camera could obtain images similar to those obtained with indocyanine green (ICG) venography. However, this requires a wide dynamic range, and images similar to the distribution of blood vessels less than 1 mm in diameter obtained with ICG venography have not yet been obtained.

[0030] In conventional InGaAs cameras, problems caused by crosstalk between elements have been pointed out, and for near-infrared light with a wavelength of 1050 nm, the 2 The dynamic range can only be set within a range that fits within the range. For example, Patent Document 13 points out that the light that directly passes through the periphery of the subject (specimen) is too strong, saturating the image captured by an infrared camera or the like, making it impossible to acquire image information. Therefore, Patent Document 13 states that image analysis is not possible unless measures are taken to attenuate the light by passing it through so that only weak light is incident on the infrared camera.

[0031] In conventional InGaAs infrared cameras, the dynamic range is limited by a capacitance placed in the feedback path of the charge integrator circuit, preventing photoexcited carriers from leaking into adjacent pixels. Because the dynamic range is limited to a small value, imaging using an aperture is not possible, and only blood vessels at a certain depth are visualized. This means that the blood vessels that can be inspected are limited to a subset of the blood vessels distributed from the superficial to the deep layers.

[0032] In order to solve the above-mentioned problems, the present invention aims to visualize blood vessels so that the condition of the veins can be determined without using a contrast agent such as ICG (indocyanine green). [Means for solving the problem]

[0033] The vein imaging device of the present invention includes an illumination device and a near-infrared camera. The illumination device emits light having a wavelength in the range of 1040 nm to 1100 nm. The near-infrared camera has a semiconductor light-receiving element array with a potential barrier formed between adjacent elements, and detects reflected light of the light emitted by the illumination device and having a wavelength in the range of 1040 nm to 1100 nm. [Effects of the Invention]

[0034] The present invention uses a wavelength that is easily absorbed by oxygenated hemoglobin but not easily absorbed by reduced hemoglobin. Furthermore, a potential barrier is formed between adjacent elements, reducing crosstalk between pixels and widening the dynamic range of the near-infrared camera. Therefore, information dependent on oxygenated hemoglobin in veins can be visualized without the use of contrast agents such as ICG (indocyanine green). Therefore, the vein imaging device of the present invention can visualize, for example, the state of oxygen continuously supplied to peripheral tissues over a long period of time, making it easier to determine the state of thrombus formation. [Brief explanation of the drawings]

[0035] [Figure 1] FIG. 1 is a diagram showing an outline of a vein imaging device. [Figure 2] FIG. 2 is a diagram showing a first specific example of the positional relationship between a near-infrared camera and a visible light camera in a vein imaging device. [Figure 3] FIG. 10 is a diagram showing a second specific example of the positional relationship between the near-infrared camera and the visible light camera of the vein imaging device. [Figure 4] FIG. 10 is a diagram showing an image of a vein imaging device that also has a dark box. [Figure 5] FIG. 10 is a diagram showing an image of a vein imaging device that also has a rotating arm. [Figure 6]FIG. 10 is a diagram showing an example of a processing flow of the vein imaging device. [Figure 7] FIG. 1 shows the structure of an InGaAs photodiode array. [Figure 8] FIG. 3 is a diagram showing examples of conditions that can be set in the near-infrared camera 1. [Figure 9] FIG. 2 is a diagram showing the configuration when measuring the photoelectric conversion characteristics of the near-infrared camera 1. [Figure 10] 3 is a diagram showing the relationship between the illuminance per unit area at the installation position of the near-infrared camera 1 and the digital output value of the near-infrared camera 1. FIG. [Figure 11] FIG. 10 is a diagram showing the output of each element in an InGaAs semiconductor photodetector array in which a potential barrier is formed. [Figure 12] FIG. 1 shows the configuration of an experimental device for comparing a near-infrared camera 1 using a light-receiving element array in which a potential barrier is formed with a near-infrared camera 34 using a light-receiving element array in which a potential barrier is not formed. [Figure 13] 10 is a diagram showing the results of an experiment comparing a near-infrared camera 1 using a light-receiving element array in which a potential barrier is formed with a near-infrared camera 34 using a light-receiving element array in which a potential barrier is not formed. [Figure 14] FIG. 10 is a diagram showing an example of imaging blood vessels in a finger using a vein imaging device. DETAILED DESCRIPTION OF THE INVENTION

[0036] Hereinafter, embodiments of the present invention will be described in detail. Components having the same functions are given the same numbers, and duplicated explanations will be omitted. [Example]

[0037] <Vein imaging device> FIG. 1 is a diagram showing an outline of a vein imaging device, FIG. 2 is a diagram showing a first specific example of the positional relationship between the near-infrared camera and the visible camera of the vein imaging device, FIG. 3 is a diagram showing a second specific example of the positional relationship between the near-infrared camera and the visible camera of the vein imaging device, FIG. 4 is a diagram showing an image of a vein imaging device that also has a dark box, FIG. 5 is a diagram showing an image of a vein imaging device that also has a rotating arm, and FIG. 6 is a diagram showing an example of the processing flow of the vein imaging device.

[0038] The vein imaging device 100 includes at least an illumination device 3 and a near-infrared camera 1. The illumination device 3 emits light having a wavelength in the range of 1040 nm to 1100 nm. "Light having a wavelength in the range of 1040 nm to 1100 nm" means that the light may include some wavelengths within this range. For example, if the illumination device 3 includes an LED that emits light at a wavelength of 1050 nm, this corresponds to "light having a wavelength in the range of 1040 nm to 1100 nm." Light outside this range may also be included. For example, the illumination device 3 may include an LED that emits light at a wavelength of 1050 nm and an LED that emits light in the visible wavelength range. When two or more types of LEDs are included, the illumination device 3 may be configured with two or more housings. The position of the illumination device 3 may be fixed or may be slidable. The emitted light is reflected by the inspection object 6.

[0039] The near-infrared camera 1 has a semiconductor light-receiving element array with a potential barrier formed between adjacent elements, and detects reflected light of light irradiated by the illumination and having a wavelength in the range of 1040 nm to 1100 nm. If the semiconductor light-receiving element array of the near-infrared camera 1 has an InGaAs photosensitive layer, it is easy to detect light having a wavelength in the range of 1040 nm to 1100 nm. The near-infrared camera 1 may also detect light outside the wavelength range of 1040 nm to 1100 nm. However, when used while irradiating visible light, a filter (not shown in FIGS. 1 and 2) may be placed so that the near-infrared camera 1 does not detect visible light. For example, the dichroic mirror 7 shown in FIG. 3 may be used as the filter. Furthermore, if the near-infrared camera 1 is set to continuously detect reflected light at predetermined time intervals, it is possible to continuously capture images of veins over a long period of time.

[0040] The vein imaging device 100 may further include a visible light camera 2 that detects visible light, a control device 4 that outputs an image obtained by superimposing an image acquired by the near-infrared camera and an image acquired by the visible light camera 2, and a display device 5 that displays the image output by the control device 4. If the near-infrared camera 1 and the visible light camera 2 are positioned so that they can capture images of approximately the same range of the object 6 to be inspected, it is easy to superimpose the images.

[0041] Blood vessels are distributed spatially. It is desirable that the near-infrared camera 1 has an aperture function so that it can acquire clear images of blood vessels. This is because images can be acquired within the range of focal depth ensured by the aperture function. However, the vein imaging device 100 uses light in the wavelength range of 1040 nm to 1100 nm, which reaches deep subcutaneous tissue. Since the illuminance of light reflected near the skin and that of light reflected at deeper positions differ greatly, the near-infrared camera 1 is required to have a wide dynamic range of illuminance. Specifically, the dynamic range of illuminance is required to be 0.007 μW / cm 2 More than 92μW / cm 2 With such a wide dynamic range, it is easy to capture blood vessels that have a spatial spread within the imageable range. If the target of imaging is a vein with a diameter of about 1 mm, the near-infrared camera 1 should have an illuminance of 0.007 μW / cm 2 More than 92μW / cm 2 It is desirable that the vein contour does not change by more than 100 μm within the following range. Note that the allowable length varies depending on the thickness of the vein to be imaged. In general, the contour also changes depending on the aperture, but the near-infrared camera can achieve this within 100 μm when the illuminance is 92 μW / cm. 2 In this case, it is sufficient that the outline of a light-emitting or light-reflecting object does not change by more than a predetermined length depending on the aperture. In other words, it is sufficient that the difference in the outline between when the aperture is open and when it is closed is equal to or less than a predetermined length. The "predetermined length" can be determined appropriately depending on the application. Generally, a resolution of 1.56 million pixels or more is sufficient for the visible light camera 2. However, the resolution can be selected to suit the purpose of the image capture.

[0042] The control device 4 collects and processes the venous system depicted with near-infrared light acquired by the near-infrared camera 1 and the positional and spatial information of the object to be examined acquired by the visible camera 2, and performs image processing to display the collected information as a real-time video or still image. When puncturing a blood vessel or performing a vascular biopsy based on the video or still image acquired by the near-infrared camera 1, the control device 4 corrects the positional and spatial information of the video or still image acquired by the visible camera 2, and displays the video or still image on the display device 5 as a parallel screen or by superimposing or covering the video or still image.

[0043] The example in Figure 2 shows how a near-infrared camera 1 and a visible light camera 2 are installed at positions 12 degrees apart, and how they capture images or videos of the inspection object. Figure 3 shows how the optical path is split by a dichroic mirror 7 according to the difference in wavelength, and how images are captured by the near-infrared camera 1 and the visible light camera 2, respectively.

[0044] The vein imaging device 100 may include a dark box 8 as shown in FIG. 4. The dark box 8 may also be included when the dichroic mirror 7 shown in FIG. 3 is included. By including the dark box 8, the near-infrared camera 1, visible light camera 2, and lighting 3 can be coordinated to capture video or still images of the inspection object 6. For example, the process flow shown in FIG. 6 may be performed. The inspection object 6 is positioned by the visible light camera 2 (S101). Next, images are captured by the near-infrared camera 1 and the visible light camera 2 in a dark state (S102). Light with a wavelength of 1040 nm to 1100 nm is then irradiated and images are captured by the near-infrared camera 1 (S103). In step S103, oxygenated hemoglobin in the vein can be captured. Next, a visible light image is captured by the visible light camera 2 (S104). The control device 4 outputs an image in which the oxygenated hemoglobin image and the visible light image are superimposed, and the image is displayed on the display device 5 (S105).

[0045] Figure 5 shows an example of a structure in which a near-infrared camera 1, a visible light camera 2, and a light source 3 are integrated. The near-infrared camera 1 and the visible light camera 2 are integrated by dividing the optical path with a dichroic mirror 7 as shown in Figure 3, thereby constituting a macro microscope 12. Furthermore, the light source 10 arranged in a ring shape around the lens 11 is capable of irradiating light in the wavelength range of 1040 nm to 1100 nm and light in the visible wavelength range.

[0046] The vein imaging device in Fig. 5 is attached to a rotary arm 13 and a linear motion mechanism 14, and can capture continuous video or still images while rotating and moving linearly around the object under test 6. Images captured by such a device can also be displayed as stereoscopic images.

[0047] <Near-infrared camera> FIG. 7 shows the structure of an InGaAs photodiode array. FIG. 7(A) is a schematic diagram of an InGaAs photodiode with a potential barrier, similar to FIG. 4 of Patent Document 14. FIG. 7(B) shows the potential distribution along line AA for the structure of FIG. 7(A). FIG. 7(C) is a schematic diagram of an InGaAs photodiode without a potential barrier, similar to FIG. 5 of Patent Document 14. FIG. 7(D) shows the potential distribution along line BB for the structure of FIG. 7(C). The method described in Patent Document 14 can be used to form a potential barrier in the device. Both the photodiode arrays of FIG. 7(A) and FIG. 7(C) are photodiode arrays formed on a substrate 21. In both photodiode arrays, a photosensitive layer 22 with a narrow bandgap energy is sandwiched between a window layer 23 and a barrier layer 28 with a wide bandgap. A reverse bias voltage is applied between an N-side electrode 26 and a P-side electrode 27. Both light receiving element arrays photoelectrically convert light incident on the photosensitive layer 22 and detect the generated charges. Note that 25 in Fig. 7(C) is a P-type diffusion layer.

[0048] Patent Document 14 describes the characteristic that, compared to the photodetector array of FIG. 7(C), photoexcited electrons tend to remain in a specific pixel until the potential difference between adjacent pixels exceeds the potential barrier of the potential barrier layer 24. In a semiconductor photodetector array in which a potential barrier is formed between adjacent elements, the photodetectors constituting the pixels are surrounded by a potential barrier layer 24 formed by P-type selective diffusion. Therefore, a potential barrier (approximately 0.3 eV) equivalent to the diffusion potential is generated in the conduction band along the adjacent pixel. Therefore, photoexcited electrons generated in a specific pixel cannot move to an adjacent pixel, demonstrating excellent pixel isolation characteristics. The near-infrared camera 1 has a semiconductor photodetector array in which a potential barrier like that shown in FIG. 7(A) is formed.

[0049] Figure 8 shows examples of conditions that can be set for the near-infrared camera 1. These conditions are set for the near-infrared camera 1, and it can operate, for example, to capture 30 frames per second with an exposure time of 16 milliseconds. Since the distance from the epidermal surface to blood vessels present in subcutaneous tissue varies depending on the part of the body, the degree of obesity, etc., it is sufficient to select conditions that provide good visibility from the settings shown in Figure 8.

[0050] Figure 9 shows the configuration used when measuring the photoelectric conversion characteristics of the near-infrared camera 1. For this measurement, an NVU3VL-2 model manufactured by IR Specs Inc., equipped with an imaging lens (OK002-Monf / 2.8, focal length 30.8 mm) manufactured by Shibuya Optical Co., Ltd., was used as the near-infrared camera 1. 1050 nm LEDs were arranged in the LED matrix 32, and the diffuser 31 used was the diffuser SS180 manufactured by Sekisui Plastics Co., Ltd. The illuminance per unit area at the position where the near-infrared camera 1 was installed was μW / cm. 2 The illuminance meter 30 used to measure the illuminance was a photodetector manufactured by Hamamatsu Photonics (G12181-230K, Φ3 mm, cutoff 1.85 μm).

[0051] The illuminance was adjusted by changing the drive current, and the digital output value (16 bits) from the near-infrared camera 1 was recorded and plotted on a graph to compare the photoelectric conversion characteristics that differ depending on the setting conditions. Figure 10 shows the relationship between the illuminance per unit area at the installation position of the near-infrared camera 1 and the digital output value of the near-infrared camera 1. The horizontal axis is the illuminance per unit area μW / cm 2 The vertical axis is the digital output value (ADC output) from the near-infrared camera 1. Different results were obtained for each of the settings (1) to (3) shown in Figure 8. It can be seen that different characteristics can be obtained by changing the settings.

[0052] Figure 11 shows the output of each element in an InGaAs semiconductor photodetector array with a potential barrier. The drive current in Figure 11 indicates the current driving the LEDs in the LED matrix 32; the larger the value, the higher the illuminance. The ADC output is the digital output value from the near-infrared camera 1. The results shown in Figure 11 illustrate that when the LED drive current exceeds 500 μA and the illuminance increases, the ADC output value reaches saturation and no change is observed. This state continues even when the drive current reaches 2000 μA. On the other hand, the ADC output of an element located approximately 100 μm away from the element whose ADC output value has reached saturation and no change is observed remains the same as when the drive current is 0 μA, indicating that it is not affected by crosstalk. In other words, when the illuminance is 0.007 μW / cm 2 More than 92μW / cm 2 Even if there is a change within the range below, it is expected that the outline of the object being imaged will not change by more than 100 μm. Furthermore, since only a slight increase is observed even in an element located approximately 15 μm away next to an element where the LED drive current exceeds 500 μA and no change in the ADC output value is observed, the effectiveness of pixel separation (crosstalk reduction) by the potential barrier can be confirmed.

[0053] The results shown in FIG. 11 indicate that when selecting a near-infrared camera 1 to be used in the vein imaging device 100, it is effective in determining whether or not a mechanism exists to prevent blooming, a phenomenon in which strong light is received and the light overflows into surrounding pixels due to saturation of the light receiving element.

[0054] Figure 12 shows the configuration of an experimental setup for comparing a near-infrared camera 1 using a photodetector array with a potential barrier and a near-infrared camera 34 using a photodetector array without a potential barrier. In this experiment, an NVU3VL-2 manufactured by IR Spec Corporation was used as the near-infrared camera 1 using an InGaAs photodetector array with a potential barrier, and an Artcam031T manufactured by Artray was used as the near-infrared camera 34 using an InGaAs photodetector array without a potential barrier. A Kowa Optical Co., Ltd. near-infrared imaging lens (LM35HC-SW) was used for both cameras. An Ushio Epitex LED (L1050 S-66-60) emitting light at a wavelength of 1050 nm was used as the LED 33. The light receiving surfaces of the near-infrared cameras 1 and 34 were positioned 40 cm away from the LED 33. The illuminance was adjusted by the amount of current driving the LED 33. The illuminance per unit area at the light receiving positions of the near-infrared cameras 1 and 34 was μW / cm. 2 The illuminance meter 30 used to measure the illuminance was a photodetector manufactured by Hamamatsu Photonics (G12181-230K, Φ3 mm, cutoff 1.85 μm).

[0055] FIG. 13 shows the results of an experiment comparing a near-infrared camera 1 using a photodetector array with a potential barrier formed and a near-infrared camera 34 using a photodetector array without a potential barrier formed. The shutter speed for both images was 18 msec (1 / 60 sec). FIG. 13(A) shows the results of an experiment comparing a near-infrared camera 1 using a photodetector array with a potential barrier formed and a near-infrared camera 34 using a photodetector array without a potential barrier formed. The shutter speed for both images was 18 msec (1 / 60 sec). The illuminance was 0.007 to 92 μW / cm 2This is a comparison of when the illuminance was changed. The top row shows the results of images taken with near-infrared camera 1 (NVU3VL-2), and the bottom row shows the results of images taken with near-infrared camera 34 (Artcam031T). In the results taken with near-infrared camera 1, the outline shape becomes unclear at high illuminance due to flare in the imaging lens, but it can be seen that the shape of the LED 33 is rendered at all set illuminance levels. On the other hand, in the results taken with near-infrared camera 34, it can be seen that the outline of the LED 33 rendered expands as the illuminance increases.

[0056] Figure 13(B) shows the illuminance at 92 μW / cm 2 The upper row shows the results of imaging with the near-infrared camera 1 (NVU3VL2), and the lower row shows the results of imaging with the near-infrared camera 34 (Artcam031T). In the results of imaging with the near-infrared camera 1, it can be seen that the size of the light-emitting portion of the LED 33 does not change even when the aperture is changed. On the other hand, in the results of imaging with the near-infrared camera 34, it can be seen that the size of the light-emitting portion of the LED 33 is reduced by setting the aperture to a small value. In other words, in order for the near-infrared camera 34 to be able to accurately recognize the size of the LED 33, it is necessary to adjust the aperture appropriately. Note that a wide dynamic range (specifically, 0.007 μW / cm) is required to image veins that are distributed spatially. 2 More than 92μW / cm 2 It is desirable that the illuminance is 92 μW / cm or less. 2 In this case, it is desirable that the outline of the light-emitting or light-reflecting object does not change depending on the aperture. It can be seen that the NVU3VL-2 manufactured by IR Spec is suitable as the near-infrared camera 1.

[0057] In non-invasive bioinstrumentation methods that capture various internal biological phenomena by observing from outside the body, it is necessary to image the distribution of blood vessels at different distances from the body surface, and to do so, it is necessary to deliver a sufficient amount of light to the blood vessels present in the subcutaneous tissue and to ensure the depth of field using an aperture. As shown in Figure 13, near-infrared camera 1, which uses a photodetector array that forms a potential barrier, can capture images over a wide range of illuminance without blooming, making it easy to use in non-invasive bioinstrumentation methods.

[0058] 14 shows an example of imaging blood vessels in a finger using the vein imaging device 100. The near-infrared camera 1 uses a photodetector array with a potential barrier, and is an NVU3VL-2 manufactured by IR Spec Corporation. The data shows a video of blood vessels in a finger captured by illuminating the camera with near-infrared light having a wavelength of 1050 nm. In this way, blood vessels in a finger can be visualized without using a contrast agent such as ICG (indocyanine green), and the image can be recorded for several minutes or more.

[0059] The present invention uses light with wavelengths of 1040 to 1100 nm, which is easily absorbed by oxygenated hemoglobin but not easily absorbed by reduced hemoglobin. Furthermore, a potential barrier is formed between adjacent elements, reducing crosstalk between pixels and widening the dynamic range of the near-infrared camera. Therefore, information dependent on oxygenated hemoglobin in veins can be visualized without the use of contrast agents such as indocyanine green (ICG). In other words, the vein imaging device of the present invention can visualize the state of oxygen continuously supplied to peripheral tissues over long periods of time, making it easier to assess the state of thrombus formation. For example, by continuously capturing and recording images at a speed of less than 100 milliseconds per image, changes in blood vessels with a diameter of approximately 1 mm due to congestion, anemia, blood flow interruption, and other conditions can be detected. It is also possible to record images over time over tens of seconds, minutes, hours, days, or even weeks. Analyzing such recorded information over time can be used to assess not only acute but also chronic progressive lesions, or to assess whether the patient is on the path to recovery.

[0060] It should be noted that the embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is not limited to the embodiments disclosed herein, but is intended to include all modifications within the scope indicated by the claims or the scope equivalent to the claims. [Explanation of symbols]

[0061] 1,34 Near-infrared camera 2 Visible camera 3 Lighting 4 Control equipment 5 Display device 6 Inspection object 7 Dichroic mirror 8 Dark box 10 Lighting 11 Lens 12 Macro microscope 13 Rotating arm 14 Linear motion mechanism 21 Board 22 Photosensitive layer 23 Window layer 24 Potential barrier layer 25 P-type diffusion layer 26 N side electrode 27 P side electrode 28 Barrier layer 30 Illuminance meter 31 Diffuser plate 32 LED matrix 33 LED 100 Vein Imaging Device

Claims

1. an illumination device that includes an LED that emits light at a wavelength of 1050 nm and irradiates light having a wavelength in the range of 1040 nm to 1100 nm; a near-infrared camera having a semiconductor light-receiving element array in which a potential barrier is formed between adjacent elements, having an aperture function, and detecting reflected light of light irradiated by the illumination and having a wavelength in the range of 1040 nm to 1100 nm; A vein imaging device comprising:

2. 2. The vein imaging device according to claim 1, The semiconductor light receiving element array has an InGaAs photosensitive layer. A vein imaging device characterized by:

3. 3. The vein imaging device according to claim 1, The near-infrared camera is equipped with a filter to block visible light detection. A vein imaging device characterized by:

4. 4. The vein imaging device according to claim 1, The near-infrared camera continuously detects reflected light at predetermined time intervals. A vein imaging device characterized by:

5. 5. The vein imaging device according to claim 1, moreover, a visible light camera that detects visible light; A control device that outputs an image obtained by superimposing the image acquired by the near-infrared camera and the image acquired by the visible light camera. The vein imaging device further comprises:

6. 6. The vein imaging device according to claim 1, The near-infrared camera has an illuminance of 92 μW / cm 2 In this case, the outline of a light-emitting or light-reflecting object does not change beyond a predetermined length depending on the aperture. A vein imaging device characterized by:

7. 6. The vein imaging device according to claim 1, The near-infrared camera has an illuminance of 0.007 μW / cm 2 More than 92μW / cm 2 Within the following range, the vein contour does not change by more than 100 μm A vein imaging device characterized by:

8. An LED emitting light with a wavelength of 1050 nm is used to irradiate light with a wavelength in the range of 1040 nm to 1100 nm, The vein is imaged using a near-infrared camera that has a semiconductor light-receiving element array in which a potential barrier is formed between adjacent elements, has an aperture function, and detects reflected light of irradiated light in the wavelength range of 1040 nm to 1100 nm. A vein imaging method comprising:

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