Laser diode bimodal fusion imaging system and method based on photoacoustic imaging

Abstract

The invention discloses a laser diode bimodal fusion imaging system based on photoacoustic imaging and a method thereof, and belongs to the field of biomedical imaging. The system is characterized in that a touch screen control signal generation module inputs a signal to a driving circuit board so as to control a laser diode and a high numerical aperture integrated laser diode to generate modulation laser; the modulation laser starts optical single-mode imaging / acoustic single-mode imaging / optical and acoustic dual-mode imaging according to a set program; modulated laser irradiates the surface of an object to be measured, generated sound signals are recorded in the data acquisition module through the signal processing circuit by the ultrasonic transducer, and a reconstructed image is generated after program fusion. According to the invention, high-resolution and high-depth photoacoustic image reconstruction is realized, defects caused by a single-mode imaging mode can be made up, and information of the single-mode imaging mode is reserved at the same time.

Description

Technical Field

[0001] The present invention belongs to the technical field of biomedical imaging, and in particular relates to a laser diode dual-modality fusion imaging system based on photoacoustic imaging and a method thereof. Background Art

[0002] Photoacoustic imaging is a non-invasive and low-cost imaging technology that has developed rapidly in recent years and relies on light absorption by biological tissues. It can make up for the defects of existing imaging modes and provide some unobtainable diagnostic information, such as blood oxygen levels in tissues, high-resolution vascular network information, etc. It has broad application prospects in the biomedical field.

[0003] To achieve high-resolution photoacoustic imaging, two types of photoacoustic microscopy can be implemented using broadband ultrasound transducers. In acoustic photoacoustic microscopy (ARPAM), high lateral resolution is achieved by acoustic focusing. To further improve the lateral resolution, optical photoacoustic microscopy (ORPAM) uses tight optical focusing to achieve a resolution of several microns or even submicron scales. High-resolution subcutaneous vascular imaging is essential for the study of peripheral microcirculatory abnormalities and tumor angiogenesis tracking. Although the high lateral resolution of ORPAM is crucial for leading biomedical research such as tumor angiogenesis imaging and melanoma cell imaging, when photon propagation changes to an optical diffusion state (1 mm below human skin), optical focusing is ineffective and the high resolution beyond the soft depth limit drops significantly.

[0004] High spatial resolution can be achieved by using ultrasonic transducers with high center frequency, wide bandwidth, and high numerical aperture (NA). However, high resolution still faces challenges in ARPAM. First, although high spatial resolution can be achieved by detecting photoacoustic waves at high center frequency and wide bandwidth, high-frequency photoacoustic waves are sharply attenuated in the skin, which results in high resolution only at a limited imaging depth when imaging subcutaneous blood vessels. Second, disadvantages are also introduced by increasing the high numerical aperture. Since the depth of focus (DOF) decreases rapidly with the increase of numerical aperture, the use of high numerical aperture transducers will greatly sacrifice the in-focus imaging range. In addition, the short working distance of high numerical aperture sensors may even cause physical obstacles to subcutaneous imaging.

[0005] Therefore, there is an urgent need for a photoacoustic imaging method that combines the advantages of the two modalities and can achieve high-resolution and high-depth imaging quality requirements. Summary of the invention

[0006] The purpose of the present invention is to provide a laser diode dual-modality fusion imaging system based on photoacoustic imaging and a method thereof, to provide a low-cost and efficient small device for existing medical imaging systems, to make up for the defects of existing imaging modes, to improve accuracy and practicality, and to provide technical support for the construction of miniaturized medical imaging equipment planning.

[0007] The technical solution of the present invention:

[0008] The touch screen control signal generating module inputs the signal to the driving circuit board to control the laser diode and the high numerical aperture integrated laser diode to generate modulated laser; the modulated laser enables optical single-mode imaging / acoustic single-mode imaging / optical + acoustic dual-mode imaging according to the set program; the modulated laser is irradiated on the surface of the object to be measured, and the generated acoustic signal is recorded in the data acquisition module through the ultrasonic transducer and the signal processing circuit, and a reconstructed image is generated after program fusion.

[0009] Specifically:

[0010] 1. Laser diode dual-modality fusion imaging system based on photoacoustic imaging

[0011] The system includes an object to be measured;

[0012] It is equipped with a signal generation module, a power supply, a diode driving circuit board, a laser diode, a high numerical aperture lens integrated laser diode, an adjustable workbench, a detection area module, an ultrasonic transducer, a signal processing circuit, a data acquisition module and a touch screen;

[0013] Its location and connection relationship are:

[0014] Place the object to be tested in the detection area module;

[0015] The laser diode and the high numerical aperture lens integrated laser diode are respectively fixed on an adjustable workbench;

[0016] The power supply is respectively connected with the touch screen, the data acquisition module and the signal processing circuit;

[0017] The signal generation module and the diode driving circuit board are connected front and back; the diode driving circuit board is connected to the laser diode and the high numerical aperture lens integrated laser diode respectively;

[0018] The laser diode and the high numerical aperture lens integrated laser diode are respectively connected to the detection area module;

[0019] The detection area module, the ultrasonic transducer, the signal processing circuit, the data acquisition module, the touch screen and the signal generation module are connected in sequence.

[0020] 2. Laser diode dual-modality fusion imaging method based on photoacoustic imaging (referred to as method)

[0021] The method comprises the following steps:

[0022] ①Place the object to be tested in the detection area module, and then select the detection mode on the touch screen;

[0023] ② After receiving the control command input from the touch screen, the signal generation module will set the wavelength type, pulse frequency and other working parameters of the laser diode and the high numerical aperture lens integrated laser diode to be output;

[0024] ③ The laser diode and high numerical aperture lens are integrated. The laser diode is fixed on an adjustable workbench. By changing the tilt angle and height of the adjustable workbench, the two beams of light are irradiated onto the surface of the object to be measured with maximum efficiency.

[0025] ④ According to the program set on the touch screen, if it is acoustic single-mode imaging, the laser diode alone will irradiate the modulated light on the surface of the object to be measured 0; if it is optical single-mode imaging, the high numerical aperture lens integrated laser diode alone will irradiate the modulated light on the surface of the object to be measured 0; if it is optical + acoustic dual-mode imaging, the laser diode and the high numerical aperture integrated laser diode will irradiate the modulated light on the surface of the object to be measured at the same time;

[0026] ⑤ After the absorption group inside the object to be tested absorbs light energy, part of the energy will be converted into heat energy, resulting in a local temperature increase. This rapid temperature change will cause instantaneous thermal expansion of the tissue, which in turn generates pressure waves and thus acoustic signals. At this time, the ultrasonic transducer receives the acoustic signal;

[0027] ⑥ The acoustic signal is processed by the signal processing circuit, the noise is reduced and amplified, and the processed acoustic signal is recorded through the input end of the data acquisition module;

[0028] ⑦ After recording the photoacoustic signal, the optical resolution signal will be preliminarily processed using the blind deconvolution + non-mean filtering noise reduction algorithm before the signal obtained by the optical resolution is synthesized with the signal obtained by the acoustic resolution in real time. The acoustic resolution signal will be preliminarily processed using SAFT (synthetic aperture) + weight. Subsequently, the data of both will be adjusted in terms of contrast, spatial pixel position, and signal amplitude to ensure a perfect match between the images, and the image to be tested will be displayed on the touch screen.

[0029] The present invention has the following advantages and positive effects:

[0030] ① For the information to be measured, the system outputs modulated laser to irradiate the surface of the object to be measured; after the absorption group inside the object to be measured absorbs the light energy, part of the energy will be converted into heat energy, resulting in a local temperature increase. This rapid temperature change will cause instantaneous thermal expansion of the tissue, which in turn generates pressure waves and thus acoustic signals; the system collects the photoacoustic signal and processes it to obtain the required image to be measured;

[0031] Photoacoustic imaging does not require the use of radioactive substances or ionizing radiation, has the characteristics of high contrast and high resolution, deep penetration imaging and real-time imaging, and provides new ideas and methods for non-invasive imaging of biological tissues.

[0032] ② Utilize optical + acoustic dual-modality imaging combination technology: Combining optical resolution imaging that can obtain high resolution but low penetration depth with acoustic resolution imaging technology that has high penetration depth but low resolution, to make up for the shortcomings of a single imaging mode.

[0033] ③ The laser generated by the optical resolution system and the laser generated by the acoustic resolution system act on the surface of the object to be measured at the same time. After being processed by the system, the signals can be perfectly separated, and real-time imaging can be achieved on the screen during the scanning process. There is no need to scan the two modes separately and then merge them, which further reduces the working time.

[0034] ④ Self-designed adjustable workbench: The angle and height of the workbench can be adjusted according to the focusing needs, so that the laser can be focused on the surface of the object to be measured with maximum efficiency and reduce unnecessary energy loss.

[0035] In summary, the present invention realizes high-resolution and high-depth photoacoustic image reconstruction, which can make up for the defects caused by the single-mode imaging mode while retaining the information of the single-mode imaging mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is the structural block diagram of this system;

[0037] Figure 2 is an exploded view of the structure of a high numerical aperture lens integrated laser diode 5;

[0038] Figure 3 is a top view of the adjustable workbench 6;

[0039] Figure 4 It is a three-dimensional view of the adjustable workbench 6.

[0040] In the figure:

[0041] 0—object to be measured;

[0042] 1—Signal generating module;

[0043] 2—Power supply;

[0044] 3—Diode driver circuit board;

[0045] 4—Laser diode;

[0046] 5—High numerical aperture lens integrated laser diode,

[0047] 5.1—Laser diode integrated cap,

[0048] 5.2—Laser diode,

[0049] 5.3—High numerical aperture lens,

[0050] 5.4—Focus adjustment knob;

[0051] 6—Adjustable workbench,

[0052] 6.1—Wooden enclosure,

[0053] 6.2—Wooden plywood,

[0054] 6.3—Tightness adjustment knob,

[0055] 6.4—Laser diode fixing area,

[0056] 6.5—Sliding support,

[0057] 7—Detection area module;

[0058] 8—ultrasonic transducer;

[0059] 9—Signal processing circuit;

[0060] 10—Data acquisition module;

[0061] 11—Touch screen. DETAILED DESCRIPTION

[0062] The following is a detailed description with reference to the accompanying drawings and embodiments.

[0063] 1. System

[0064] 1. Overall

[0065] like Figure 1 , the system includes an object to be measured 0;

[0066] A signal generating module 1, a power supply 2, a diode driving circuit board 3, a laser diode 4, a high numerical aperture lens integrated laser diode 5, an adjustable workbench 6, a detection area module 7, an ultrasonic transducer 8, a signal processing circuit 9, a data acquisition module 10 and a touch screen 11 are provided;

[0067] Its location and connection relationship are:

[0068] Place the object to be tested 0 in the detection area module 7;

[0069] The laser diode 4 and the high numerical aperture lens integrated laser diode 5 are respectively fixed on an adjustable workbench 6;

[0070] The power supply 2 is connected to the touch screen 11, the data acquisition module 10 and the signal processing circuit 9 respectively;

[0071] The signal generating module 1 and the diode driving circuit board 3 are connected front and back; the diode driving circuit board 3 is connected to the laser diode 4 and the high numerical aperture lens integrated laser diode 5 respectively;

[0072] The laser diode 4 and the high numerical aperture lens integrated laser diode 5 are respectively connected to the detection area module 7;

[0073] The detection area module 7, the ultrasonic transducer 8, the signal processing circuit 9, the data acquisition module 10, the touch screen 11 and the signal generating module 1 are connected in sequence.

[0074] Working process:

[0075] When it is necessary to detect the image of the object to be detected 0, first place the object to be detected 0 in the detection area module 7 and turn on the power 2; then select the detection mode on the touch screen 11 (optical single-mode imaging, acoustic single-mode imaging or optical + acoustic dual-mode imaging and other modes can be selected, dual-mode imaging is used as an example here); when the signal generating module 1 receives the control instruction from the touch screen 11, the output wavelength category is set to 520nm and the laser pulse frequency is 1kHz; then the signal generating module 1 drives the laser diode 4 and the high numerical aperture lens integrated laser diode 5 to output through the diode driving circuit board 3; the pulse modulated light is adjusted in direction and position through the adjustable workbench 6 After that, it is irradiated on the surface of the object to be tested 0; after the absorption group inside the object to be tested 0 absorbs the light energy, part of the energy will be converted into heat energy, resulting in a local temperature increase. This rapid temperature change will cause instantaneous thermal expansion of the tissue, thereby generating pressure waves and thus generating acoustic signals. At this time, the ultrasonic transducer 8 receives the acoustic signal; after being processed by the signal processing circuit 9, the acoustic signal is denoised, amplified and fused for imaging. After being processed, the acoustic signal is recorded through the input end of the data acquisition module 10; after the photoacoustic signal is recorded, the signal obtained by the optical resolution and the signal obtained by the acoustic resolution are synthesized in real time to obtain a high-resolution and high-depth imaging image, which is displayed on the touch screen 11.

[0076] 2. Functional components

[0077] 0) Object to be tested 0

[0078] The object to be tested 0 is an animal tissue slice.

[0079] 1) Signal generation module 1

[0080] The signal generating module 1 is a component for generating light source signals controlled by an FPGA circuit board, and specifically an AlinxAX515 development board is selected.

[0081] Its function is to generate the required signal for the laser diode 4.

[0082] 2) Power supply 2

[0083] They are respectively connected to the touch screen 11, the data acquisition module 10 and the signal processing circuit 9, and the SIGLENTSPD3303C power supply is specifically selected.

[0084] Its function is to provide power.

[0085] 3) Diode driver circuit board 3

[0086] The diode driver circuit board 3 is a purchased part, specifically PivoLAS LDP-V-50-100V3.3.

[0087] Its function is to connect the signal generator 1 to drive the laser diode 4 to work.

[0088] 4) Laser diode 4

[0089] Commonly used components, specifically the PLPT9450LB_E laser diode from OSRAM Metal Can.

[0090] Its function is to provide detection light source.

[0091] 5) High numerical aperture lens integrated laser diode 5

[0092] like Figure 2 The high numerical aperture lens integrated laser diode 5 is a self-designed component, including a laser diode integrated cap 5.1, a laser diode 5.2, a high numerical aperture lens 5.3 and a focus adjustment knob 5.4 connected in sequence;

[0093] The overall appearance is cylindrical, with a cover for fixing the laser diode 5.2 at the top, a high numerical aperture lens 5.3 at the bottom, and a focus adjustment knob 5.4 at the bottom for adjusting the focus.

[0094] Its function is to provide a high numerical aperture lens for optical resolution microscopic imaging and focus the light spot.

[0095] 6) Adjustable workbench 6

[0096] like Figure 3 , 4 , the adjustable workbench 6 comprises a wooden shell 6.1, a wooden splint 6.2, a tension adjustment knob 6.3, a laser diode fixing area 6.4 and a slidable support 6.5;

[0097] Its location and connection relationship are:

[0098] The wooden splint 6.2 is connected to the tension adjustment knob 6.3, the wooden housing 6.1 is connected to the slidable support 6.5, and the laser diode 4 and the high numerical aperture lens integrated laser diode 5 are fixed in the laser diode fixing area 6.4.

[0099] (1) Wooden housing 6.1

[0100] The wooden housing 6.1 is rectangular, and is processed after obtaining appropriate dimensions in the early simulation;

[0101] Its function is to provide external structural support for the entire adjustable workbench 6.

[0102] (2) Wooden plywood 6.2

[0103] The wooden splint 6.2 is rectangular, and a gap is left between the wooden shell 6.1 to leave redundant space for adjusting the direction of the laser diode 4;

[0104] Its function is to fix the laser diode 4 and to adjust the irradiation direction of the laser diode 4 .

[0105] (3) Tension adjustment knob 6.3

[0106] The tension adjustment knob 6.3 is connected to the wooden splint 6.2;

[0107] Its function is: to fix the wooden plywood to move in 6.2 directions.

[0108] (4) Laser diode fixing area 6.4

[0109] Its function is to fix the laser diode 4 and the high numerical aperture lens integrated laser diode 5.

[0110] (5) Sliding support 6.5

[0111] The slidable support 6.5 is connected to the wooden housing 6.1;

[0112] Its function is to control the height of the wooden housing 6.1, thereby ensuring that the laser diode 4 can reach the optimal focusing distance.

[0113] 7) Detection area module 7

[0114] The detection module consists of a bracket and a stepper motor.

[0115] Its function is to place the object to be tested 0.

[0116] 8) Ultrasonic transducer 8

[0117] The ultrasonic transducer 8 is a purchased part, specifically a Doppler I2-5C6F15 model.

[0118] Its function is to convert photoacoustic signals into electrical signals for detection.

[0119] 9) Signal processing circuit 9

[0120] The circuit consists of an amplifier, a filter and a microcomputer module connected in sequence.

[0121] ①Amplifier

[0122] The amplifier module is a highly integrated small amplifier, which is used to amplify the electrical signal collected by the ultrasonic transducer 8 and is manually set by the user on the touch screen 11 .

[0123] The specific model used is CONNPHY CLC-10K0.5G-5510-S.

[0124] ②Filter

[0125] The filter module is a high-pass filter, which is used to filter the electrical signal collected by the ultrasonic transducer 8 without manual setting by the user.

[0126] Specifically selected is BPF0.5-30MHz BAND PASS FILTER.

[0127] ③Microcomputer module

[0128] The microcomputer module is a self-designed component used for analyzing and processing control system parameters and signals.

[0129] 10) Data acquisition module 10

[0130] The data acquisition module 10 is an externally purchased component and is a high-performance data acquisition card.

[0131] The specific model selected is PCIe8912M from Altay.

[0132] Its function is to collect and save data.

[0133] 11) Touch screen 11

[0134] The touch screen 11 is a self-designed component that imports a microcomputer module, which is used to control the analysis and processing of system parameters and signals. On the one hand, it outputs a modulated signal to the signal generating module 1 according to the user's settings to change the working current of the laser diode, realize the modulation and scanning of the laser wavelength, and adjust the internal model to match the features to be tested. On the other hand, after obtaining the electrical signals after all features are amplified and filtered, the module inputs these signals into the internal processing to obtain the measurement values ​​of the features to be tested, and finally displays them through the touch screen 10.

[0135] Its function is to adjust the output properties and internal model of the signal generation module 1 according to the user settings, and lock the output signal of the ultrasonic transducer 8 after amplification and filtering, and obtain the measurement value of the feature to be detected through processing.

[0136] 2. Laser diode dual-modality fusion imaging method based on photoacoustic imaging (referred to as method)

[0137] The method comprises the following steps:

[0138] ① Place the object to be detected 0 in the detection area module 7, and then select the detection mode on the touch screen 11 (optical single-mode imaging, acoustic single-mode imaging, or optical + acoustic dual-mode imaging, etc. can be selected here);

[0139] ② After receiving the control command input by the touch screen 11, the signal generating module 1 sets the wavelength type, pulse frequency and other working parameters of the laser diode 4 and the high numerical aperture lens integrated laser diode 5 to be output;

[0140] ③ The laser diode 4 and the high numerical aperture lens integrated laser diode 5 are fixed on the adjustable workbench 6. By changing the tilt angle and height of the adjustable workbench 6, the two beams of light are irradiated on the surface of the object to be measured 0 with maximum efficiency.

[0141] ④ According to the program set on the touch screen 11, if it is acoustic single-mode imaging, the laser diode 4 alone irradiates the modulated light on the surface of the object to be measured 0; if it is optical single-mode imaging, the high numerical aperture lens integrated laser diode 5 alone irradiates the modulated light on the surface of the object to be measured 0; if it is optical + acoustic dual-mode imaging, the laser diode 4 + high numerical aperture integrated laser diode 5 simultaneously irradiate the modulated light on the surface of the object to be measured 0;

[0142] ⑤ After the absorption group inside the object to be tested 0 absorbs light energy, part of the energy will be converted into heat energy, resulting in a local temperature increase. This rapid temperature change will cause instantaneous thermal expansion of the tissue, which in turn generates pressure waves and thus acoustic signals. At this time, the ultrasonic transducer 8 receives the acoustic signal;

[0143] ⑥ The acoustic signal is processed by the signal processing circuit 9, the noise is reduced and amplified, and the acoustic signal is recorded through the input end of the data acquisition module 10 after being processed;

[0144] ⑦ After recording the photoacoustic signal, the signal obtained by the optical resolution is synthesized in real time with the signal obtained by the acoustic resolution to obtain a high-resolution and high-depth imaging image, which is displayed on the touch screen.

Claims

1. A laser diode dual-modality fusion imaging system based on photoacoustic imaging, characterized in that: The object to be measured (0) is included; A signal generating module (1), a power supply (2), a diode driving circuit board (3), a laser diode (4), a high numerical aperture lens integrated laser diode (5), an adjustable workbench (6), a detection area module (7), an ultrasonic transducer (8), a signal processing circuit (9), a data acquisition module (10) and a touch screen (11) are provided; Its location and connection relationship are: Placing the object to be detected (0) in the detection area module (7); The laser diode (4) and the high numerical aperture lens integrated laser diode (5) are respectively fixed on an adjustable workbench (6); The power supply (2) is respectively connected to the touch screen (11), the data acquisition module (10) and the signal processing circuit (9); The signal generation module (1) and the diode driving circuit board (3) are connected front to back; the diode driving circuit board (3) is connected to the laser diode (4) and the high numerical aperture lens integrated laser diode (5) respectively; The laser diode (4) and the high numerical aperture lens integrated laser diode (5) are respectively connected to the detection area module (7); The detection area module (7), the ultrasonic transducer (8), the signal processing circuit (9), the data acquisition module (10), the touch screen (11) and the signal generation module (1) are connected in sequence.

2. The laser diode dual-modality fusion imaging system based on photoacoustic imaging according to claim 1, characterized in that: The high numerical aperture lens integrated laser diode (5) comprises a laser diode integrated cap (5.1), a laser diode (5.2), a high numerical aperture lens (5.3) and a focus adjustment knob (5.4) which are connected in sequence; Provides high numerical aperture lenses to focus light spots for optical resolution microscopy.

3. The laser diode dual-modality fusion imaging system based on photoacoustic imaging according to claim 1, characterized in that: The adjustable workbench (6) comprises a wooden shell (6.1), a wooden splint (6.2), a tension adjustment knob (6.3), a laser diode fixing area (6.4) and a slidable support (6.5); Its location and connection relationship are: The wooden splint (6.2) is connected to the tension adjustment knob (6.3), the wooden housing (6.1) is connected to the slidable support (6.5), and the laser diode (4) and the high numerical aperture lens integrated laser diode (5) are fixed in the laser diode fixing area (6.4).

4. The method of the laser diode dual-modality fusion imaging system based on photoacoustic imaging according to claim 1, 2 or 3, characterized in that: ① Place the object to be tested (0) in the detection area module (7), and then select the detection mode on the touch screen (11); ② After receiving the control command input by the touch screen (11), the signal generating module (1) sets the wavelength type, pulse frequency and other working parameters of the light source to be output by the laser diode (4) and the high numerical aperture lens integrated laser diode (5); ③ The laser diode (4) and the high numerical aperture lens integrated laser diode (5) are fixed on an adjustable workbench (6). By changing the tilt angle and height of the adjustable workbench (6), the two beams of light are irradiated onto the surface of the object to be measured (0) with maximum efficiency. ④ According to the program set on the touch screen (11), if it is acoustic single-mode imaging, the laser diode (4) alone irradiates the modulated light on the surface of the object to be measured (0); if it is optical single-mode imaging, the high numerical aperture lens integrated laser diode (5) alone irradiates the modulated light on the surface of the object to be measured (0); if it is optical + acoustic dual-mode imaging, the laser diode (4) and the high numerical aperture integrated laser diode (5) simultaneously irradiate the modulated light on the surface of the object to be measured (0); ⑤ After the absorption group inside the object to be measured (0) absorbs light energy, part of the energy will be converted into heat energy, resulting in a local temperature increase. This rapid temperature change will cause instantaneous thermal expansion of the tissue, which in turn generates pressure waves and thus generates acoustic signals. At this time, the ultrasonic transducer (8) receives the acoustic signal; ⑥ The acoustic signal is processed by the signal processing circuit (9), the noise is reduced and the signal is amplified. The processed acoustic signal is recorded through the input end of the data acquisition module (10); ⑦ After recording the photoacoustic signal, the optical resolution signal will be preliminarily processed using the blind deconvolution + non-mean filtering noise reduction algorithm before the signal obtained by the optical resolution is synthesized with the signal obtained by the acoustic resolution in real time. The acoustic resolution signal will be preliminarily processed using SAFT (synthetic aperture) + weight. Subsequently, the data of both will be adjusted in terms of contrast, spatial pixel position, and signal amplitude to ensure a perfect match between the images, and the image to be tested will be displayed on the touch screen.

Images