Photoacoustic imaging method using focusing LED light source

Abstract

The invention provides a photoacoustic imaging method using a focusing LED light source. The photoacoustic imaging method solves the problems that high-quality photoacoustic imaging cannot be achieved due to insufficient light intensity of the LED light source, electromagnetic interference is serious, and irradiation in liquid and tissue is difficult. The imaging method comprises the following steps: a driving circuit emits a periodic pulse signal with driving capability, and controls an LED array to periodically emit pulse light; the 3D printing assembly is fixed to the upper portion of the LED array, and the hole positions correspond to the LED positions; an optical fiber penetrates through the 3D printing assembly, and the input end of the optical fiber is coupled with the light-emitting part of the LED; light of a plurality of strands of optical fibers is combined into one beam at the output end of the optical fibers through an optical fiber beam combiner, pulsed light emitted by a plurality of LEDs is overlapped together, the focusing effect is achieved, and high-strength pulsed light can be obtained at the output end of the beam combiner; high-intensity pulsed light at the output end of the beam combiner is used for irradiating an imaging target, an ultrasonic probe is used for receiving a sound pressure signal, and photoacoustic imaging is achieved through an algorithm.

Description

Technical Field

[0001] The invention relates to a photoacoustic imaging method, and in particular to a photoacoustic imaging method using a focused LED light source. Background Art

[0002] Photoacoustic imaging is a medical imaging method developed in recent years. It has the characteristics of high resolution, safety and reliability. The principle of photoacoustic imaging is the photoacoustic phenomenon. When a beam of pulsed light is irradiated on the surface of the imaging object, the internal tissue will produce photoacoustic phenomenon and stimulate the sound pressure signal. The ultrasonic transducer periodically receives the sound pressure signal stimulated by each light pulse, and these sound waves are processed to reconstruct the photoacoustic image.

[0003] The selection and design of the light source is an important part of photoacoustic imaging. Current high-resolution photoacoustic imaging generally uses a pump laser as the light source. However, this type of laser is expensive and has a low pulse repetition frequency, which means that real-time imaging is difficult to achieve. LED pulse light source is a low-cost, higher-safety photoacoustic light source. Since high-speed LEDs can emit pulsed light at a higher frequency, using them as photoacoustic light sources can achieve real-time imaging. However, the higher repetition frequency and nanosecond pulse width mean that LEDs will produce more serious electromagnetic interference. When the frequency of this interference is close to the center frequency of the ultrasound probe, it will interfere with the signal received by the ultrasound probe. At the same time, the LED array light source used in existing LED photoacoustic imaging technology is difficult to achieve irradiation in liquids and endoscopic irradiation in biological tissues, which limits the application scenarios of LED light sources in photoacoustic imaging. Summary of the invention

[0004] Purpose of the invention: The technical problem to be solved by the present invention is that the light source used in the existing LED photoacoustic imaging technology has low illumination intensity and a large divergence angle, making it difficult to focus.

[0005] In order to solve the above technical problems, the present invention discloses a photoacoustic imaging method using a focused LED light source, the photoacoustic imaging method is applied to a photoacoustic imaging system, the photoacoustic imaging system includes a pulse drive circuit, an LED array, a 3D printing component installed above the LED array, an optical fiber, a fiber combiner, an imaging target and an ultrasonic transducer, the photoacoustic imaging method includes the following steps:

[0006] Step 1, connecting the pulse driving circuit to the LED array through a transmission line, wherein the pulse driving circuit emits a periodic pulse signal with driving capability to control the LED to work periodically, wherein in each working cycle, the continuous conduction time of the LED is in the nanosecond level, and the LED is kept in the off state at other times, and pulse light is periodically emitted;

[0007] Step 2, fixing the 3D printed component above the LED array, with the hole position corresponding to each LED position of the LED array;

[0008] Step 3, passing the optical fiber through the hole of the 3D printed component, so that the input end of the optical fiber is aligned with and close to the light-emitting part of the LED and coupled;

[0009] Step 4, at the output end of the optical fiber, coupling a plurality of the optical fibers with the input end of the optical fiber combiner, so that the pulsed light in the plurality of the optical fibers is combined into one, and a high-intensity pulsed light is obtained at the output end of the optical fiber combiner;

[0010] Step 5, placing the imaging target still in the air or water, irradiating the target on the side or inside of the imaging target with the output end of the fiber combiner, receiving the sound pressure signal generated by the photoacoustic effect on the surface of the imaging target using the ultrasonic transducer, and processing the received signal through a reconstruction algorithm to obtain a photoacoustic reconstructed image.

[0011] Specifically, the repetition frequency of the driving circuit is in the kHZ range, the pulse output voltage is relatively high, the driving circuit is used to drive multiple LEDs, so that the LED array circuit emits pulse light at a specific frequency. The driving circuit controls all LEDs in the LED array to turn on and off at the same time.

[0012] Specifically, the LED array is a hard circuit board that is not easily deformed, has screw fixing holes at four corners, and has a certain distance between the LEDs in both the horizontal and vertical directions to ensure that the optical fibers do not interfere with each other after being coupled with the LEDs.

[0013] Specifically, the LEDs in the LED array are of the same model, the LED packages are smaller, the LED rated power is higher, the rise time and fall time are in the nanosecond order, the radiation intensity is higher, and the light emission wavelength of the LED is within the wavelength range that can produce photoacoustic phenomena.

[0014] Specifically, the 3D printed component is not easily deformed and has a certain thickness. The length and width of the 3D printed component are equal to the LED array. The four corners have screw fixing holes corresponding to the LED array and of equal size. The 3D printed component is punched at a position corresponding to each LED of the LED array, and the punching diameter is equivalent to the length and width of the LED package. The 3D printed component and the LED array are fixed together by screws passing through the four corner holes.

[0015] Specifically, the optical fiber is a quartz optical fiber, the input end and the output end are both ground and polished, have a certain bending ability, the optical fiber core diameter is relatively large, the optical fiber outer diameter is slightly smaller than the hole of the 3D printed component, the light receiving angle is relatively large, and the number of the optical fibers is the same as the number of LEDs in the LED array. The optical fiber can pass through the hole of the 3D printed component, the optical fiber input end is in close contact with the light-emitting part of the LED, the optical fiber and the light-emitting part of the LED are coupled using a refractive index matching liquid, and the optical fiber is fixed to the 3D printed component by glue.

[0016] Specifically, the input end of the fiber combiner is connected to the output end of the optical fiber using a PC-type fiber optic connector. There are two fiber combiners, each of which is coupled with a plurality of the optical fibers, and the connection gaps are coupled by a refractive index matching liquid.

[0017] Specifically, if the side irradiation method is adopted, the output ends of the two fiber combiners are respectively located on both sides of the imaging target, and the output ends of the fiber combiners are perpendicular to the side irradiation of the imaging target, and the distance between the two is small; if the internal irradiation of the target tissue is adopted, the output end optical fiber of the fiber combiner should be introduced into the tissue to irradiate the target area. The ultrasonic transducer is perpendicular to the surface of the imaging target, and the distance between the two is less than the receiving depth of the transducer. The transducer and the target surface are coupled with water or ultrasonic coupling agent.

[0018] Beneficial effects:

[0019] The present invention proposes a photoacoustic imaging method using a focused LED light source, which includes designing a high-speed LED array, driving the array to emit periodic pulsed light, designing a 3D printed component adapted to the LED array, and fixing the component above the LED array, passing the optical fiber through the 3D printed component to closely attach and couple with the light-emitting part of the LED, and then fixing the optical fiber on the 3D printed component, after the pulsed light emitted by the LED is led out from the optical fiber, coupling the output ends of several optical fibers with a fiber combiner to achieve pulsed light superposition and focusing, irradiating the target object with the high-intensity pulsed light obtained at the output end of the fiber combiner, and receiving the sound pressure signal through the ultrasonic transducer for image reconstruction. By guiding the light away from the LED array circuit through the optical fiber, electromagnetic interference near the LED is avoided, and at the same time, relying on the bendability and waterproof characteristics of the optical fiber, the light source proposed by the present invention can realize the endoscopic irradiation of the target in the liquid and the inside of the biological tissue by the LED light. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments, and the above and other advantages of the present invention will become more clear.

[0021] Figure 1Schematic diagram of the structure of the underwater photoacoustic imaging system provided by the first embodiment of the present invention.

[0022] Figure 2 It is a schematic structural diagram of a driving circuit and an LED array provided in the first embodiment of the present invention.

[0023] Figure 3 This is a physical photo of a 3D printed component adapted for an LED array provided in the first embodiment of the present invention.

[0024] Figure 4 4 is a schematic diagram of the structure of a photoacoustic endoscopic imaging system provided in a second embodiment of the present invention.

[0025] The description of the reference numerals is as follows: 1. pulse drive circuit; 2. LED array; 21. LED; 22. screw hole; 3. 3D printing component; 31. hole corresponding to LED; 32. screw hole; 4. optical fiber; 5. fiber combiner; 51. PC type optical fiber connector; 52. fiber combiner input end; 53. fiber combiner output end; 6. imaging target; 7. ultrasonic transducer. DETAILED DESCRIPTION

[0026] Example 1

[0027] Embodiment 1 of the present invention provides a photoacoustic imaging method using a focused LED light source, and the photoacoustic imaging method is applied to a photoacoustic imaging system.

[0028] See also Figures 1 to 3 The photoacoustic imaging system includes a pulse driving circuit 1, an LED array 2, a 3D printing component 3 installed above the LED array 2, an optical fiber 4, a fiber combiner 5, an imaging target 6 and an ultrasonic transducer 7.

[0029] See now Figure 2 , the LEDs 21 are connected in series so that the LEDs 21 are turned on and off at the same time, and emit pulse light at the same time. The size of the LED array 2 is 4cm×4cm, which contains 16 LEDs 21. The package of the LED 21 is 1.6mm×1.6mm, the emission wavelength is 940nm, the divergence angle is 70°, the size of the light-emitting area is 0.73mm×0.73mm, the rise time is 940nm, the fall time is 16ns, the forward instantaneous conduction voltage drop is 3.4V, the maximum forward instantaneous current can reach 2A, and the radiation intensity is 680mW / sr. The LED array 2 is arranged in a 4×4 square, and the horizontal and vertical distances between the centers of adjacent LEDs 21 are set to 5mm. There are holes 22 for installing fixing screws at the four corners of the LED array 2.

[0030] It should be understood that the number and arrangement of the LEDs 21 in the LED array 2 can be adjusted according to light intensity requirements.

[0031] See also Figure 3 The size of the 3D printed component 3 is equal to that of the LED array 2, the thickness is 15mm, and the four corners have screw fixing holes 32 that are the same as those on the LED array 2. The 3D printed component 3 punches holes 31 at the same position as each LED 21 on the LED array 2, the diameter of the punched holes 31 is 1.5mm, and the horizontal and vertical distances between the centers of adjacent holes 31 are 5mm. The 3D printed component 3 is fixed above the LED array 2 by screws, and the position of the LED 21 is completely aligned with the punched holes 31.

[0032] It should be understood that the number and arrangement of the holes in the 3D printing component 3 can be adjusted according to the number and arrangement of the LEDs 21 .

[0033] See also Figure 1 The core diameter of the optical fiber 4 is 1 mm, which is larger than the light-emitting part of the LED 21 . The outer diameter of the optical fiber 4 is 1.4 mm, which is smaller than the diameter of the hole 31 of the 3D printed component. The optical fiber 4 has a lower propagation attenuation for the light emitted by the LED 21 .

[0034] See also Figure 1 The fiber combiner 5 is an eight-in-one combiner, which melts eight quartz optical fibers at the input end 52 into one. The core diameter of the optical fiber at the input end 52 is 1 mm, and the outer diameter is 1.5 mm. The input end 52 is provided with a PC-type optical fiber connector 51 that can be connected to the optical fiber 4. The core diameter of the optical fiber at the output end 53 is 3 mm, and the outer diameter is 4 mm.

[0035] In Embodiment 1 of the present invention, the imaging target 6 is a material or biological tissue that strongly absorbs the light emitted by the LED 21, and the ultrasonic transducer 7 is a linear array transducer with 128 array elements and a center frequency of 5 MHz.

[0036] The photoacoustic imaging method using a focused LED light source provided in Example 1 of the present invention comprises the following steps:

[0037] Step 1, connecting the pulse driving circuit 1 to the LED array 2 through a transmission line, wherein the pulse driving circuit 1 emits a periodic pulse signal with driving capability to control the LED 21 to work periodically. In each working cycle, the continuous on time of the LED 21 is 50ns, and the LED 21 is kept off at other times, and periodically emits pulse light;

[0038] Specifically, the pulse drive circuit is connected to the LED array 2 via a high-frequency signal transmission line, and the transmission line has a shielding layer to reduce interference to the pulse signal. In order to drive the LED array 2 and ensure high-resolution photoacoustic imaging, the peak value of the pulse voltage output by the drive circuit 1 should be greater than 55V, the pulse width is 50ns, and the repetition frequency is 4kHz.

[0039] Step 2, fix the 3D printed component 3 above the LED array 2, and punch holes 31 corresponding to the position of each LED 21 of the LED array 2;

[0040] Step 3, passing the optical fiber 4 through the hole 31 of the 3D printing component, so that the input end of the optical fiber 4 is aligned with and close to the light-emitting part of the LED 21 and coupled;

[0041] Specifically, the input end of the optical fiber 4 is coupled to the LED 21 via a refractive index matching liquid, the refractive index of the refractive index matching liquid being equivalent to the refractive index of the core of the optical fiber 4 , and then the optical fiber 4 is fixed on the 3D printing component 3 .

[0042] Step 4, at the output end of the optical fiber 4, a plurality of the optical fibers 4 are coupled to the input end 52 of the optical fiber combiner, so that the pulsed light in the plurality of the optical fibers 4 is combined into one, and a high-intensity pulsed light is obtained at the output end 53 of the optical fiber combiner;

[0043] Specifically, the PC type fiber optic connector 51 is installed at the input end 52 of the fiber optic combiner, and the optical fiber 4 is coupled to the PC type fiber optic connector 51 using a refractive index matching liquid. Before the optical fiber 4 is coupled to the optical fiber connector 51, the LED array 2 is driven to measure the light intensity at the output end of the optical fiber 4. After coupling, the light intensity emitted at the output end 53 of the fiber optic combiner should be eight times the light intensity at the output end of the optical fiber 4. With this as a reference, the effect of coupling can be verified, and the relative position of the output end of the optical fiber 4 and the optical fiber connector 51 can be continuously adjusted to obtain the maximum output light intensity. After the coupling is completed, an ultraviolet lamp is used to irradiate the coupling to solidify the refractive index matching liquid.

[0044] Step 5, use the output end 53 of the fiber combiner to illuminate the target on the side of the imaging target 6, use the ultrasonic transducer 7 to receive the sound pressure signal generated by the photoacoustic effect above the imaging target 6, and process the received signal through a reconstruction algorithm to obtain a photoacoustic reconstructed image.

[0045] Specifically, the imaging target 6 is placed in water and irradiated externally. The output end 53 of the optical fiber combiner should be close to the imaging target 6, with a distance of less than 5 mm, so that the pulsed light can irradiate deeper tissues of the target 6 and stimulate photoacoustic signals. The ultrasonic transducer 7 is coupled to the imaging target 6 through water or other coupling agents.

[0046] It should be understood that the ultrasonic transducer 7 and the algorithm used for photoacoustic reconstruction can be adjusted according to the requirements of accuracy and speed.

[0047] In Example 1 of the present invention, the specific process of step (3) is as follows:

[0048] Step 3-1, passing 16 optical fibers 4 through the holes 31 of the 3D printing component 3 and close to the LED 21, with the center of the optical fiber 4 aligned with the light-emitting part of the LED 21;

[0049] Step 3-2, dripping a refractive index matching liquid between the optical fiber 4 and the LED 21, driving the LED 21 to emit light, measuring the light intensity at the output end of the optical fiber 4, and continuously adjusting the relative position of the input end of the optical fiber 4 and the LED 21 until the light intensity at the output end of the optical fiber 4 is the maximum, and the optical fiber 4 is considered to be aligned with the LED 21;

[0050] Step 3-2, use ultraviolet light to irradiate the coupling point between the input end of the optical fiber 4 and the LED 21 to solidify the refractive index matching liquid, and use glue to bond the optical fiber 4 and the 3D printed component 3 at the joint between the two, so that the LED array 2, the 3D printed component 3 and the optical fiber 4 are fixed together.

[0051] Example 2

[0052] Different from the first embodiment, in the present embodiment, the output end (53) of the optical fiber combiner is not irradiated outside the imaging target (6), but is introduced into the target for endoscopic irradiation imaging. The specific process is as follows:

[0053] See also Figure 4 The output end (53) of the optical fiber combiner is introduced into the interior of the target (6) so as to illuminate the imaging area, and the ultrasonic transducer (7) receives the sound pressure signal generated by the photoacoustic phenomenon at the side of the imaging target (6) perpendicular to the surface of the imaging target (6).

[0054] It should be understood that the number of groups of optical fibers (4) and the number of optical fiber combiners (5) can be adjusted according to specific experimental requirements.

[0055] So far, we have obtained high-intensity pulsed infrared light through optical fiber transmission and beam combining, and can use this pulsed light for photoacoustic imaging of phantoms or biological tissues.

[0056] The present invention provides a photoacoustic imaging method using a focused LED light source. There are many methods and ways to implement the technical solution. The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the protection scope of the present invention. All components not specified in this embodiment can be implemented by existing technologies.

Claims

1. A photoacoustic imaging method using a focused LED light source, characterized in that: The imaging method is applied to a photoacoustic imaging system, the photoacoustic imaging system comprising a pulse drive circuit (1), an LED array (2), a 3D printing component (3) installed above the LED array (2), an optical fiber (4), an optical fiber combiner (5), an imaging target (6) and an ultrasonic transducer (7), and the photoacoustic imaging method comprises the following steps: Step (1), connecting the pulse driving circuit (1) and the LED array (2) via a transmission line, wherein the pulse driving circuit (1) emits a periodic pulse signal with driving capability to control the LED (21) to work periodically, wherein in each working cycle, the LED (21) is continuously turned on for 50 ns and remains in an off state for the rest of the time, and periodically emits pulse light; Step (2), fixing the 3D printed component (3) above the LED array (2), with the hole position corresponding to the position of each LED (21) of the LED array (2); Step (3), passing the optical fiber (4) through the hole (31) of the 3D printing component (3), so that the input end of the optical fiber (4) is aligned with and closely attached to the light-emitting part of the LED (21) and coupled; Step (4), at the output end of the optical fiber (4), coupling a plurality of the optical fibers (4) with the input end (52) of the optical fiber combiner, so that the pulsed light in the plurality of the optical fibers is combined into one, and high-intensity pulsed light is obtained at the output end (53) of the optical fiber combiner; Step (5), placing the imaging target (6) in air or water, irradiating the target from the side or inside of the imaging target (6) with the output end (53) of the optical fiber combiner, receiving the sound pressure signal generated by the photoacoustic phenomenon on the surface of the imaging target (6) with the ultrasonic transducer (7), and processing the received signal by a reconstruction algorithm to obtain a photoacoustic reconstructed image.

2. A photoacoustic imaging method using a focused LED light source according to claim 1, characterized in that: The repetition frequency of the driving circuit (1) is in the order of kHZ, and the pulse output voltage is relatively high. The driving circuit (1) is used to drive a plurality of LEDs so that the LED array circuit (2) emits pulse light at a specific frequency. The driving circuit (1) controls all LEDs (21) of the LED array (2) to be turned on and off simultaneously.

3. A photoacoustic imaging method using a focused LED light source according to claim 1, characterized in that: The LED array (2) is a hard circuit board that is not easily deformed, and has screw fixing holes (22) at four corners. The LEDs (21) are spaced a certain distance apart in both the horizontal and vertical directions, ensuring that the optical fibers (4) do not interfere with each other after the optical fibers (4) are coupled to the LEDs (21).

4. A method for photoacoustic imaging using a focused LED light source according to claim 3, characterized in that: The LEDs (21) in the LED array (2) are of the same model, the LED (21) packages are small, the LED (21) has a high rated power, a rise time and a fall time of nanoseconds, a high radiation intensity, and the light emission wavelength of the LED (21) is within a wavelength range capable of producing a photoacoustic phenomenon.

5. The photoacoustic imaging method using a focused LED light source according to claim 1, characterized in that: The 3D printed component (3) is not easily deformed and has a certain thickness. The length and width of the 3D printed component (3) are equal to those of the LED array (2). The four corners are provided with screw fixing holes (32) corresponding to the LED array (2) and of equal size. The 3D printed component (3) is punched with holes (31) at positions corresponding to each LED (21) of the LED array (2), and the diameter of the holes (31) is equal to the length and width of the LED package. The 3D printed component (3) and the LED array (2) are fixed together by screws passing through the four corner holes.

6. A method for photoacoustic imaging using a focused LED light source according to claim 1, characterized in that: The optical fiber (4) is a quartz optical fiber, and both the input end and the output end are ground and polished, and have a certain bending ability. The core diameter of the optical fiber (4) is relatively large, and the outer diameter of the optical fiber (4) is slightly smaller than the hole (31) of the 3D printing component (3). The light receiving angle is relatively large, and the number of the optical fibers (4) is the same as the number of LEDs (21) in the LED array (2). The optical fiber (4) passes through the hole (31) of the 3D printing component (3), and the input end of the optical fiber (4) is closely attached to the light-emitting part of the LED (21). The optical fiber (4) and the light-emitting part of the LED (21) are coupled using a refractive index matching liquid, and the optical fiber (4) is fixed to the 3D printing component (3) by glue.

7. A photoacoustic imaging method using a focused LED light source according to claim 1, characterized in that: The input end (52) of the optical fiber combiner is connected to the output end of the optical fiber (4) using a PC type optical fiber connector (51). There are two optical fiber combiners (5), each of which is coupled to a plurality of optical fibers (4), and the connection gap is coupled via a refractive index matching liquid.

8. The photoacoustic imaging method using a focused LED light source according to claim 1, characterized in that: In the side irradiation mode, the two fiber combiner output ends (53) are respectively located on both sides of the imaging target (6), and the fiber combiner output ends (53) are perpendicular to the side of the imaging target (6) for irradiation, and the distance between the two is relatively small; in the internal irradiation mode, the fiber combiner output ends (53) are introduced into the tissue to irradiate the target area. The ultrasonic transducer (7) is perpendicular to the surface of the imaging target (6), and the distance between the two is less than the receiving depth of the transducer (7), and the transducer (7) and the surface of the target (6) are coupled by water or ultrasonic coupling agent.

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