A photoacoustic imaging method using a focused LED light source

Abstract

The application provides a photoacoustic imaging method using a focused LED light source, solves the problems of insufficient light intensity of the LED light source, inability to realize high-quality photoacoustic imaging, serious electromagnetic interference and difficulty in irradiation in liquid and tissue. The imaging method comprises the following steps: a driving circuit emits a periodic pulse signal with driving capacity, and controls an LED array to periodically emit pulsed light; a 3D printing component is fixed above the LED array, and a hole position corresponds to an LED position; an optical fiber is passed through the 3D printing component, and an input end of the optical fiber is coupled with a light-emitting part of the LED; a plurality of optical fibers are combined into one bundle at the output end of the optical fiber by using an optical fiber combiner, the pulsed light emitted by the plurality of LEDs is superimposed together, the focusing effect is achieved, and high-intensity pulsed light can be obtained at the output end of the combiner; the imaging target is irradiated by using the high-intensity pulsed light at the output end of the combiner, an ultrasonic probe receives an acoustic pressure signal, and photoacoustic imaging is realized through an algorithm.

Description

Technical Field

[0001] This invention relates to a photoacoustic imaging method, and more particularly to a photoacoustic imaging method using a focused LED light source. Background Technology

[0002] Photoacoustic imaging is a medical imaging method that has been developed in recent years. It features high resolution and high safety and reliability. The principle of photoacoustic imaging is based on the photoacoustic phenomenon. When a pulsed light beam shines on the surface of the object being imaged, the internal tissue will produce a photoacoustic phenomenon, which will excite a sound pressure signal. An ultrasonic transducer periodically receives the sound pressure signal excited by each light pulse. By processing these sound waves, a photoacoustic image can be reconstructed.

[0003] The selection and design of the light source is a crucial aspect of photoacoustic imaging. Current high-resolution photoacoustic imaging generally uses pump lasers as the light source; however, these lasers are expensive and have low pulse repetition frequencies, making real-time imaging difficult. LED pulsed light sources are a low-cost and safer option. Because high-speed LEDs can emit pulsed light at high frequencies, they can be used for real-time imaging. However, the high repetition frequency and nanosecond-level pulse width mean that LEDs generate significant electromagnetic interference. When the frequency of this interference is close to the center frequency of the ultrasound probe, it can interfere with the signal received by the probe. Furthermore, existing LED photoacoustic imaging technologies using LED arrays are difficult to apply to liquids and endoscopic imaging of biological tissues, limiting 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 light intensity and large divergence angle, making it difficult to focus.

[0005] To address the aforementioned technical problems, this invention discloses a photoacoustic imaging method using a focused LED light source. This photoacoustic imaging method is applied to a photoacoustic imaging system, which includes a pulse driving circuit, an LED array, a 3D-printed component mounted above the LED array, an optical fiber, an optical fiber combiner, an imaging target, and an ultrasonic transducer. The photoacoustic imaging method includes the following steps:

[0006] Step 1: Connect the pulse driving circuit to the LED array via a transmission line. The pulse driving circuit emits a periodic pulse signal with driving capability to control the LED to work periodically. In each working cycle, the LED is continuously on for nanoseconds and remains off at other times, periodically emitting pulse light.

[0007] Step 2: Fix the 3D printed component above the LED array, with the holes corresponding to the positions of each LED in the LED array;

[0008] Step 3: Pass the optical fiber through the hole in the 3D printed component, align the input end of the optical fiber with and couple it to the light-emitting part of the LED;

[0009] Step 4: At the output end of the optical fiber, several optical fibers are coupled to the input end of the optical fiber combiner, so that the pulse light in the several optical fibers is combined into one, and high-intensity pulse light is obtained at the output end of the optical fiber combiner.

[0010] Step 5: Place the imaging target in air or water, irradiate the target from the side or inside using the output end of the fiber optic combiner, receive the sound pressure signal generated by the photoacoustic effect on the surface of the imaging target using the ultrasonic transducer, and process the received signal using a reconstruction algorithm to obtain a photoacoustic reconstructed image.

[0011] Specifically, the driving circuit has a repetition frequency on the order of kHz and a relatively high pulse output voltage. The driving circuit drives multiple LEDs, causing the LED array circuit to emit pulsed light at a specific frequency. The driving circuit also controls all LEDs in the LED array to simultaneously turn on and off.

[0012] Specifically, the LED array is a rigid circuit board that is not easily deformed, and has screw holes at the four corners. The LEDs are spaced apart both horizontally and vertically to ensure that the optical fibers do not interfere with each other after they are coupled to the LEDs.

[0013] Specifically, the LEDs in the LED array are of the same type, the LED packages are small, the LEDs have high rated power, rise and fall times are in the nanosecond range, the radiation intensity is high, and the light emission wavelength of the LEDs is within the wavelength range that can produce photoacoustic phenomena.

[0014] Specifically, the 3D-printed component is not easily deformed, has a certain thickness, and its length and width are equal to those of the LED array. It has screw holes of the same size at each of the four corners, corresponding to the LED array. The 3D-printed component drills holes at positions corresponding to each LED in the LED array, with hole diameters approximately equal 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, with both the input and output ends being ground and polished to provide a certain degree of flexibility. The fiber core diameter is relatively large, while the outer diameter is slightly smaller than the perforation in the 3D-printed component, resulting in a large light reception angle. The number of optical fibers is the same as the number of LEDs in the LED array. The optical fiber can pass through the perforation in the 3D-printed component, with the input end of the fiber in close contact with the light-emitting portion of the LED. A refractive index matching fluid is used for coupling between the optical fiber and the light-emitting portion of the LED. The optical fiber is fixed to the 3D-printed component with adhesive.

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

[0017] Specifically, if side illumination is used, the output ends of the two fiber optic combiners are located on either side of the imaging target, with the output ends of the fiber optic combiners illuminating the side of the imaging target perpendicularly, and the distance between them is small. If internal tissue illumination is used, the output fibers of the fiber optic combiners should be guided into the tissue to irradiate the target area. The ultrasonic transducer is perpendicular to the surface of the imaging target, and the distance between them is less than the receiving depth of the transducer. The transducer is coupled to the target surface with water or an ultrasonic coupling agent.

[0018] Beneficial effects:

[0019] This invention proposes a photoacoustic imaging method using a focused LED light source. A high-speed LED array is designed to emit periodic pulsed light. A 3D-printed component adapted to the LED array is designed and fixed above the array. An optical fiber is passed through the 3D-printed component and coupled tightly to the light-emitting part of the LED, then fixed to the 3D-printed component. The pulsed light emitted by the LED is guided out of the optical fiber, and the output ends of several optical fibers are coupled to an optical fiber combiner to achieve pulsed light superposition and focusing. The high-intensity pulsed light obtained from the output end of the optical fiber combiner is used to illuminate the target object, and the sound pressure signal is received by an ultrasonic transducer for image reconstruction. By guiding the light away from the LED array circuit through optical fibers, electromagnetic interference near the LED is avoided. Furthermore, thanks to the flexibility and waterproof properties of optical fibers, the light source proposed in this invention can achieve endoscopic illumination of targets in liquids and inside biological tissues using LED light. Attached Figure Description

[0020] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention as described above or otherwise will become clearer.

[0021] Figure 1This is a schematic diagram of the underwater photoacoustic imaging system provided in the first embodiment of the present invention.

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

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

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

[0025] The reference numerals in the attached diagram are as follows: 1. Pulse drive circuit; 2. LED array; 21. LED; 22. Screw hole; 3. 3D printed component; 31. Hole corresponding to the LED; 32. Screw hole; 4. Optical fiber; 5. Optical fiber combiner; 51. PC type optical fiber connector; 52. Input end of optical fiber combiner; 53. Output end of optical fiber combiner; 6. Imaging target; 7. Ultrasonic transducer. Detailed Implementation

[0026] Example 1

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

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

[0029] See now Figure 2 The LEDs 21 are connected in series, allowing them to simultaneously turn on and off, emitting pulsed light. The LED array 2 measures 4cm x 4cm and contains 16 LEDs 21. Each LED 21 has a 1.6mm x 1.6mm package, a wavelength of 940nm, a divergence angle of 70°, a light-emitting area of ​​0.73mm x 0.73mm, a rise time of 940nm, a fall time of 16ns, a forward instantaneous voltage drop of 3.4V, a maximum forward instantaneous current of 2A, and a radiation intensity of 680mW / sr. The LED array 2 is arranged in a 4x4 square, with a lateral and longitudinal distance of 5mm between the centers of adjacent LEDs 21. The four corners of the LED array 2 have holes 22 for mounting screws.

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

[0031] See Figure 3 The 3D printed component 3 is the same size as the LED array 2, with a thickness of 15mm, and has screw holes 32 at its four corners, identical to those on the LED array 2. The 3D printed component 3 has holes 31 drilled at the same positions as each LED 21 on the LED array 2, with a diameter of 1.5mm and a horizontal and vertical distance of 5mm between the centers of adjacent holes 31. The 3D printed component 3 is fixed above the LED array 2 with screws, ensuring the LED 21 positions are perfectly aligned with the holes 31.

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

[0033] See 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 low propagation attenuation for the light emitted by the LED 21.

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

[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 5MHz.

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

[0037] Step 1: Connect the pulse driving circuit 1 to the LED array 2 via a transmission line. 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 LED 21 is continuously turned on for 50ns and remains off at other times, periodically emitting pulse light.

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

[0039] Step 2: Fix the 3D printed component 3 above the LED array 2, with the holes 31 corresponding to the positions of each LED 21 in the LED array 2;

[0040] Step 3: Pass 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 in close contact with 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 through a refractive index matching liquid, the refractive index of which is equivalent to the refractive index of the fiber core 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, several optical fibers 4 are coupled to the input end 52 of the optical fiber combiner, so that the pulse light in the several optical fibers 4 is combined into one, and high-intensity pulse 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. The fiber optic cable 4 is coupled to the PC-type fiber optic connector 51 using a refractive index matching fluid. Before coupling the fiber optic cable 4 to the fiber optic connector 51, the LED array 2 is driven to measure the light intensity at the output end of the fiber optic cable 4. After coupling, the light intensity emitted at the output end 53 of the fiber optic combiner should be approximately eight times that of the output end of the fiber optic cable 4. Using this as a reference, the coupling effect can be verified, and the relative position of the output end of the fiber optic cable 4 and the fiber optic connector 51 can be continuously adjusted to obtain the maximum output light intensity. After coupling, the coupling area is irradiated with an ultraviolet lamp to cure the refractive index matching fluid.

[0044] Step 5: Illuminate the target 6 from the side using the output end 53 of the fiber optic combiner, receive the sound pressure signal generated by the photoacoustic effect above the target 6 using the ultrasonic transducer 7, and process the received signal using a reconstruction algorithm to obtain a photoacoustic reconstructed image.

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

[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 Embodiment 1 of the present invention, the specific process of step (3) is as follows:

[0048] Step 3-1: Pass 16 optical fibers 4 through the holes 31 of the 3D printing component 3 and attach them tightly 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: Drop a refractive index matching liquid between the optical fiber 4 and the LED 21, drive the LED 21 to emit light, measure the light intensity at the output end of the optical fiber 4, and continuously adjust the relative position between 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 at its maximum, which is considered as the optical fiber 4 and the LED 21 being aligned.

[0050] Step 3-2: Use an ultraviolet lamp to irradiate the coupling point between the input end of the optical fiber 4 and the LED 21 to cure the refractive index matching liquid. Use glue to bond the optical fiber 4 and the 3D printing component 3 together, so that the LED array 2, the 3D printing component 3 and the optical fiber 4 are fixed together.

[0051] Example 2

[0052] Unlike Embodiment 1, in this embodiment, the output end (53) of the fiber optic combiner is not used to irradiate the outside of the imaging target (6), but is instead introduced into the inside of the target for endoscopic imaging. The specific process is as follows:

[0053] See Figure 4 The output end (53) of the fiber optic combiner is introduced into the interior of the target (6) so that it illuminates the imaging area. The ultrasonic transducer (7) receives the sound pressure signal generated by the photoacoustic phenomenon on 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 optical fiber (4) groups and the number of optical fiber combiners (5) can be adjusted according to specific experimental requirements.

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

[0056] This invention provides a photoacoustic imaging method using a focused LED light source. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A photoacoustic imaging method using a focused LED light source, characterized by, The imaging method is applied to a photoacoustic imaging system, and the photoacoustic imaging system comprises a pulse driving circuit (1), an LED array (2), a 3D printing assembly (3) installed above the LED array (2), an optical fiber (4), a 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) through a transmission line, the pulse driving circuit (1) emits a periodic pulse signal with driving ability, controls the periodic operation of the LED (21), and in each working period, the LED (21) is continuously turned on for 50 ns and is kept off at other times, and periodically emits pulsed light; Step (2), fixing the 3D printing assembly (3) above the LED array (2), and the hole position corresponds 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 assembly (3), aligning and tightly coupling the input end of the optical fiber (4) with the light-emitting part of the LED (21); Step (4), at the output end of the optical fiber (4), coupling a plurality of optical fibers (4) with the input end (52) of the fiber combiner to synthesize a stream of pulsed light in a plurality of optical fibers, and obtaining high-intensity pulsed light at the output end (53) of the fiber combiner; Step (5), placing the imaging target (6) in air or water, irradiating the target on the side or inside of the imaging target (6) with the output end (53) of the fiber combiner, receiving the sound pressure signal generated by the photoacoustic phenomenon on the surface of the imaging target (6) using the ultrasonic transducer (7), and obtaining the photoacoustic reconstruction image by processing the received signal through a reconstruction algorithm.

2. The photoacoustic imaging method using a focused LED light source according to claim 1, wherein, The repetition frequency of the driving circuit (1) is kHZ, the driving circuit (1) is used for driving a plurality of LEDs, the LED array (2) emits periodic pulsed light, and the driving circuit (1) controls all LEDs (21) of the LED array (2) to be turned on and turned off at the same time.

3. The photoacoustic imaging method using a focused LED light source according to claim 1, wherein, The LED array (2) is a hard circuit board and is not easy to deform, four corners have first screw fixing holes (22), there is a certain distance between the LEDs (21) in the horizontal and vertical directions, so that the optical fibers (4) do not interfere with each other after being coupled with the LEDs (21).

4. The photoacoustic imaging method using a focused LED light source according to claim 3, wherein, The LED (21) in the LED array (2) is of the same type, the rising time and falling time of the LED (21) are nanoseconds, and the light-emitting wavelength of the LED (21) is within the wavelength range capable of generating photoacoustic phenomenon.

5. The method of photoacoustic imaging using a focused LED light source of claim 1, wherein, The 3D printing component (3) is not easy to deform and has a certain thickness. The length and width of the 3D printing component (3) are equal to those of the LED array (2). The four corners have second screw fixing holes (32) corresponding to and equal in size to the LED array (2). The 3D printing component (3) is punched (31) at a position corresponding to each LED (21) of the LED array (2). The diameter of the punch (31) is equivalent to the length and width of the LED package. The 3D printing component (3) and the LED array (2) are fixed together by screws passing through the hole positions in the four corners.

6. The method of photoacoustic imaging using a focused LED light source of claim 1, wherein, The optical fiber (4) is a quartz optical fiber. The input end and the output end are polished and polished. It has a certain bending ability. The outer diameter of the optical fiber (4) is slightly smaller than the punch (31) of the 3D printing component (3). The number of optical fibers (4) is the same as the number of LEDs (21) in the LED array (2). The optical fiber (4) passes through the punch (31) of the 3D printing component (3). The input end of the optical fiber (4) is in close contact with the light-emitting part of the LED (21). The refractive index matching liquid is used to couple between the optical fiber (4) and the light-emitting part of the LED (21). The optical fiber (4) is fixed on the 3D printing component (3) by glue.

7. The method of photoacoustic imaging using a focused LED light source of claim 1, wherein, The input end (52) of the optical fiber combiner is connected with the output end of the optical fiber (4) using a PC type optical fiber connector (51). The optical fiber combiner (5) has two, and each optical fiber combiner (5) is coupled with several optical fibers (4). The connection gap is coupled by refractive index matching liquid.

8. The method of photoacoustic imaging using a focused LED light source of claim 1, wherein, In the side illumination mode, the two optical fiber combiner output ends (53) are located on both sides of the imaging target (6), and the output end (53) of the optical fiber combiner is perpendicular to the side of the imaging target (6) for side illumination. In the internal illumination mode, the output end (53) of the optical fiber combiner is introduced into the internal illumination target area of the tissue. The ultrasonic transducer (7) is perpendicular to the surface of the imaging target (6), and the distance between them is less than the receiving depth of the transducer (7). The transducer (7) and the surface of the target (6) are coupled by water or ultrasonic coupling agent.

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