CN116784798A - Photoacoustic imaging system - Google Patents

Abstract

The invention provides a photoacoustic imaging system, which is composed of a light source, a micro-ring resonant cavity detector array and a signal processing unit. The micro-ring resonant cavity detector array includes at least two detector arrays, and each detector array includes At least two microring resonators. During the imaging process, the light source emits a laser signal, each micro-ring resonant cavity generates a corresponding resonance signal according to the laser signal, and the signal processing unit outputs an image signal correspondingly according to each resonance signal. The small size, high on-chip integration, high sensitivity, large bandwidth, and large acceptance angle (~75°) of the microring resonator-based detector array are incomparable to traditional detectors PZT, PMUTs and CMUTs, and can achieve imaging System miniaturization. At the same time, the photoacoustic detector array based on the microring resonator can achieve high-resolution fast imaging, precise positioning of sound sources, and deep wide-field imaging, which can further move closer to clinical applications.

Description

Photoacoustic imaging system

Technical field

The present invention relates to the field of imaging technology, and in particular to photoacoustic imaging systems.

Background technique

Photoacoustic imaging (PAI) is a new imaging method that combines the advantages of traditional optical imaging and ultrasonic imaging. Most photoacoustic imaging systems will integrate detectors, such as piezoelectric ceramic-based ultrasonic transducers ( Piezoelectric transducer (PZT), micromachined piezoelectric ultrasonic transducers (PMUTs) and micromachined capacitive ultrasonic transducers (CMUTs). The above-mentioned detectors all have problems such as small bandwidth, large size, and small receiving angle, which accordingly lead to problems such as low image resolution, excessive volume of the imaging system, slow imaging speed, and low positioning accuracy of the sound source.

Therefore, the existing technology needs to be improved.

Contents of the invention

The main purpose of the present invention is to propose a photoacoustic imaging system to at least solve the technical problems of large imaging system size and slow imaging speed in existing photoacoustic imaging systems in related technologies.

The invention provides a photoacoustic imaging system. The photoacoustic imaging system includes a light source, a micro-ring resonant cavity detector array and a signal processing unit; the micro-ring resonant cavity detector array includes at least two detector arrays, each The path detector array includes at least two micro-ring resonant cavities;

Wherein, the light source is used to emit a laser signal, each of the micro-ring resonant cavities is used to generate a corresponding resonance signal according to the laser signal, and the signal processing unit is used to output an image signal correspondingly according to each of the resonance signals.

Optionally, the light source is a wavelength-tunable continuous wave laser, and the continuous wave laser is used to continuously emit laser signals with a wavelength range of 1530-1565 nm.

Optionally, the photoacoustic imaging system also includes an optical fiber and a coupler;

The optical fiber and the coupler are arranged between the light source and the micro-ring resonant cavity.

Optionally, the signal processing unit includes a photoelectric balance detector, an amplifier, a data acquisition card and a control display; the photoelectric balance detector is electrically connected to the control display via the amplifier and the data acquisition card; The photoelectric balance detector is used to receive the resonance signal, the amplifier is used to amplify the resonance signal to obtain an amplified signal, the data acquisition card is used to collect the amplified signal, and the control display is used to collect the amplified signal according to the Output image signal.

Optionally, the data acquisition card is configured with the same number of acquisition channels as the number of the micro-ring resonant cavities, and each of the acquisition channels is used to acquire the amplified signal corresponding to a corresponding one of the micro-ring resonant cavities.

The photoacoustic imaging system of the present invention is composed of a light source, a micro-ring resonant cavity detector array and a signal processing unit, wherein the micro-ring resonant cavity detector array includes at least two detector arrays, and each detector array includes at least two Microring resonant cavity. During the imaging process, the light source emits a laser signal, each micro-ring resonant cavity generates a corresponding resonance signal according to the laser signal, and the signal processing unit outputs an image signal correspondingly according to each resonance signal. The small size, high on-chip integration, high sensitivity, large bandwidth, and large acceptance angle (~75°) of the microring resonator-based detector array are incomparable to traditional detectors PZT, PMUTs and CMUTs, and can achieve imaging System miniaturization. At the same time, the photoacoustic detector array based on the microring resonator can achieve high-resolution fast imaging, precise positioning of sound sources, and deep wide-field imaging, which can further move closer to clinical applications.

Description of the drawings

In order to explain the embodiments of the present application or the technical solutions in the prior art more clearly, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are only These are some embodiments recorded in this application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without exerting creative efforts.

Figure 1 is a schematic structural diagram of the photoacoustic imaging system provided in the embodiment of the present application;

Figure 2 is a schematic structural diagram of a signal processing unit in an embodiment of the present application;

Figure 3 is a schematic diagram of the connection between optical fiber, coupler, light source and micro-ring resonant cavity according to the embodiment of the present application.

The functions, features and advantages that can be achieved by the present invention will be further described with reference to the embodiments and the accompanying drawings.

Detailed ways

It should be understood that the specific embodiments described here are only used to explain the present invention and are not intended to limit the present invention.

It should be noted that related terms such as “first”, “second”, etc. may be used to describe various components, but these terms do not limit the component. These terms are only used to distinguish one component from another component. For example, without departing from the scope of the invention, a first component could be termed a second component, and the second component could similarly be termed a first component. The term "and/or" refers to any one or more combinations of the associated and described items. In addition, in order to better explain the present invention, numerous specific details are given in the following detailed description. It will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known structures and components are not described in detail in order to emphasize the subject matter of the invention.

Among related technologies, photoacoustic imaging (PAI) is a new imaging method that combines the advantages of traditional optical imaging and ultrasonic imaging. Its principle is to use short pulse laser to irradiate objects to generate ultrasonic waves, which are received by the detector and processed by the signal. The reconstruction produces an image showing the specificity of optical absorption within the object. Since the entire imaging process has no contact with the imaging object, and the source of image contrast is the specific absorption of excitation light by the absorber inside the object, PAI is a label-free imaging, and multi-wavelength imaging can be performed by changing the wavelength of the excitation light to calibrate the composition of the object. Element.

Specifically: According to different application scenarios, photoacoustic imaging can be divided into photoacoustic tomography, photoacoustic microscopy (PAM) and photoacoustic endoscopy (PAE). The latter two imaging methods are based on the Time of Flight (TOF) method, which uses a single detector to scan point by point or rotate to scan the photoacoustic source for imaging; however, for PACT, due to the use of expanded beam wide light source illumination The absorbers at different positions inside the object simultaneously release photoacoustic signals. Therefore, even under ideal circumstances, three-dimensional imaging of objects requires a single detector to move to three different positions or the use of three fixed detectors to receive photoacoustic signals to locate the photoacoustic source.

In the actual imaging process, the number of detectors and their various parameters determine the performance of the photoacoustic tomography system. For example, the imaging speed depends on the number of detectors used; the positioning accuracy of the sound source by the imaging system is determined by the detection surface size, acceptance angle and number of detectors of a single detector; the imaging resolution and detection depth are determined by the size of the detector , bandwidth, sensitivity and quantity are jointly determined. Therefore, arraying single detectors with excellent performance can improve the performance of photoacoustic imaging systems.

Specific: Relevant literature also introduces a linear transducer detection array composed of 128 detectors (center frequency 7MHz, bandwidth 5MHz), which is used for photoacoustic tomography imaging of isolated mice, achieving better than 130um The lateral resolution and the axial resolution of 330um, the imaging depth is about 7.5mm, and the imaging time is about 1.5 hours. Generally speaking, when the normal direction of the ultrasonic wave surface is perpendicular to the detection surface of the detector, the detection efficiency is the highest. Obviously, the above linear array detector does not meet this requirement. Brecht et al. described an arc-shaped detection array composed of 64 transducers with a center frequency of 3.1MHz, a focal length of 65mm, and was used to image internal organs and blood vessels in mice. The imaging time was 8 minutes and the spatial resolution was 500um. Xia et al. proposed a ring-shaped transducer array with a center frequency of 5MHz and a diameter of 50mm composed of 512 detectors for imaging living mice. It only takes 1.6s to image an area with a diameter of 20mm and a thickness of 1mm. The resolution can reach 100um. Lin et al. disclosed a hemispheric detector array composed of 4 arc-shaped transducers, with 256 detectors per channel. The complete scanning and imaging only takes 5 seconds, and the resolution of mouse brain imaging is 390um, and the imaging depth is is 10mm.

Most photoacoustic imaging systems have detectors integrated into them, such as piezoelectric ceramic-based ultrasound transducers (PZT), micromachined piezoelectric ultrasound transducers (PMUTs) and micromachined capacitive ultrasound. Detectors (Capacitive micromachined ultrasonic transducers, CMUTs). The above-mentioned detectors all have problems such as small bandwidth, large size, and small receiving angle, which accordingly lead to problems such as low image resolution, excessive volume of the imaging system, slow imaging speed, and low positioning accuracy of the sound source.

Therefore, in order to solve the technical problems of excessive volume and slow imaging speed of imaging systems in related technologies, please refer to Figure 1. An embodiment of the present invention provides a photoacoustic imaging system 1. The photoacoustic imaging system includes a light source 10, a micro Ring resonator detector array 20 and signal processing unit 30.

The light source 10 refers to a device that can generate a laser signal, such as a continuous wave laser with tunable wavelength. The continuous wave laser can continuously emit laser signals in the wavelength range of 1530-1565 nm.

The micro-ring resonant cavity detector array 20 includes at least two detector arrays, and each detector array includes at least two micro-ring resonant cavities (in Figure 1, the two micro-ring resonant cavities on the left form a detector array, and the two micro-ring resonant cavities on the right form a detector array. The ring resonator forms another detector array). That is, the number of detector arrays is n, the number of corresponding micro-ring resonators is m, and n and m are both integers greater than or equal to 2. Among them, the microring resonant cavity detector array is manufactured based on semiconductor processing technology.

Through the photoacoustic imaging system of this embodiment, the light source, the microring resonant cavity detector array and the signal processing unit form the photoacoustic imaging system, and the microring resonant cavity detector array includes at least two detector arrays, each detector array Including at least two micro-ring resonant cavities. During the imaging process, the light source emits a laser signal, each micro-ring resonant cavity generates a corresponding resonance signal according to the laser signal, and the signal processing unit outputs an image signal correspondingly according to each resonance signal. The small size, high on-chip integration, high sensitivity, large bandwidth, and large acceptance angle (~75°) of the microring resonator-based detector array are incomparable to traditional detectors PZT, PMUTs and CMUTs, and can achieve imaging System miniaturization. At the same time, the photoacoustic detector array based on the microring resonator can achieve high-resolution fast imaging, precise positioning of sound sources, and deep wide-field imaging, which can further move closer to clinical applications.

Please refer to Figure 2. The signal processing unit 30 includes a photoelectric balance detector 301, an amplifier 302, a data acquisition card 303 and a control display 304; the photoelectric balance detector is electrically connected to the control display through the amplifier and data acquisition card, that is, the photoelectric balance detector The output terminal is electrically connected to the input terminal of the amplifier, the output terminal of the amplifier is electrically connected to the input terminal of the data acquisition card, and the output terminal of the data acquisition card is electrically connected to the input terminal of the control display. Specifically, when the microring resonant cavity generates a resonant signal, the photoelectric balance detector converts the resonant signal into an electrical signal. The amplifier amplifies the electrical signal to obtain an amplified signal. The data acquisition card collects the amplified signal and controls the display to output an image signal based on the amplified signal. .

In a practical application scenario, when the continuous wave laser continuously emits laser signals in the wavelength range of 1530-1565nm, each microring resonant cavity in the microring resonant cavity detector array generates a corresponding resonance signal according to the laser signal, and the signal processing unit The photoelectric balance detector in the detector receives the resonant signal and converts it into an electrical signal. The amplifier performs low-noise amplification of the electrical signal (increasing the signal strength) to obtain an amplified signal. The data acquisition card collects the data of the amplified signal changing with time, and controls the display based on The pre-installed image reconstruction program reconstructs the data collected by the data acquisition card and displays the reconstruction results (output image signals).

Please refer to Figure 3. The photoacoustic imaging system also includes an optical fiber and a coupler. The optical fiber and coupler are arranged between the light source and the microring resonant cavity. Among them, there are two sections of optical fiber (labeled subsequently as fiber 1 and fiber 2) and two couplers (labeled as couplers 1 and 2). The light is input from port 1 through fiber 1 and coupler 1 for transmission (coupling The device is designed to improve the coupling efficiency with the optical fiber), and then couples to the microring resonant cavity through the evanescent field in coupling area 1. The light returns to coupling area 1 after traveling in the microring cavity for one week, and is transmitted from port 1 to The light in this area generates constructive interference, and the light intensity in the cavity increases; at the same time, the light in the resonant cavity is output to port 2 through the evanescent field in coupling area 2, and the light intensity in the cavity decreases; as the light is coupled Areas 1 and 2 continuously input and output, the light intensity in the resonant cavity is dynamically balanced, and the output light intensity of port 2 is stable. Specifically, during imaging, light (ultra)sound waves act as mechanical waves on the microring cavity, squeezing and deforming the waveguide, thereby changing the effective refractive index (neff) of the waveguide for 1550nm light, resulting in The resonance of the light of this wavelength weakens in the micro-ring cavity, the light intensity in the micro-ring cavity is no longer stable, and the output light intensity of port 2 fluctuates; and the coupler 2 and optical fiber 2 transmit the optical signal output from port 2 to the photoelectric balance detector After being amplified by the amplifier, the data is recorded to the acquisition card, and finally processed and displayed by the control monitor.

In an optional implementation of this embodiment, the data acquisition card is configured with the same number of acquisition channels as the number of micro-ring resonant cavities, and each acquisition channel is used to collect the amplified signal corresponding to a corresponding one of the micro-ring resonant cavities. . That is, the n lines of the micro-ring cavity detection array respectively correspond to the n channels of the acquisition card, and the n*m detectors in the array jointly receive light (ultra)acoustic waves (the spatial distribution of each micro-ring cavity in the same channel is designed so that The optical signal output interval of adjacent micro-ring cavities is larger than the sampling interval of the photoelectric balance detector to avoid image distortion caused by signal aliasing). Different detectors are used according to the different arrangement modes of the detectors (linear, arc, ring, spherical...) Image reconstruction algorithm.

The following is a further explanation of the technical effects achieved by this embodiment: the present invention uses semiconductor processing technology to manufacture a micro-ring resonant cavity based on SOI materials for photoacoustic imaging; it uses a continuous wave laser with a wavelength of 1550 nm as the detection light source to realize the full light of the micro-ring cavity. Detect light (ultrasound) sound; adjust the number and arraying method of micro-ring resonant cavities according to the different states of the imaging objects (arraying micro-ring cavities is used for light (ultrasound) sound imaging). That is to say, compared with the existing high-performance ultrasonic detectors, the micro-ring cavity used in the present invention is smaller in size, has a larger bandwidth, and has higher sensitivity per unit detection area, and can be integrated on a chip for mass production. The arraying method of the microring cavity can be changed according to the shape and size of the imaging sample to achieve higher ultrasonic detection efficiency and achieve accurate imaging of the sample. The structure size of the micro-ring cavity that makes up the detection array can be adjusted according to the application scenario to meet different detection requirements.

In a practical application scenario, through the photoacoustic imaging contrast, the difference in the absorption of light of a certain wavelength by the absorber inside the sample can be obtained. The photoacoustic signal is a series of sound pressures between ~10pa-~KPa and frequencies between ~KHz-~GHz. Ultrasound, which carries information about the absorber. The microring resonant cavity has a detection sensitivity of mPa/√Hz and a bandwidth of ~100MHz, so the microring cavity can be used as an ultrasonic detector in photoacoustic imaging. Moreover, the microring cavity has a small size, a large detection angle, and is easy to be arrayed, making it easy to achieve higher resolution when used in photoacoustic tomography and to position the absorber with high accuracy.

In the several embodiments provided in this application, it should be understood that the disclosed device can be implemented in other ways. For example, the device embodiments described above are only illustrative. For example, the division of modules is only a logical function division. In actual implementation, there may be other division methods. For example, multiple modules or components may be combined or integrated. to another system, or some features can be ignored, or not implemented. On the other hand, the coupling or direct coupling or communication connection between each other shown or discussed may be through some interfaces, indirect coupling or communication connection of devices or modules, and may be in electrical, mechanical or other forms.

Modules described as separate components may or may not be physically separated, and components shown as modules may or may not be physical modules, that is, they may be located in one place, or they may be distributed to multiple network modules. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

In addition, each functional module in each embodiment of the present application can be integrated into one processing module, or each module can exist physically alone, or two or more modules can be integrated into one module. The above integrated modules can be implemented in the form of hardware or software function modules.

Integrated modules can be stored in a computer-readable storage medium if they are implemented in the form of software function modules and sold or used as independent products. Based on this understanding, the technical solution of the present application is essentially or contributes to the existing technology, or all or part of the technical solution can be embodied in the form of a software product. The computer software product is stored in a readable storage. The medium includes several instructions to cause a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods of various embodiments of the present application. The aforementioned readable storage media include: U disk, mobile hard disk, ROM, RAM, magnetic disk or optical disk and other media that can store program code.

In the above embodiments, each embodiment is described with its own emphasis. For parts that are not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

The above are only preferred embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the description and drawings of the present invention may be directly or indirectly used in other related technical fields. , are all similarly included in the scope of patent protection of the present invention.

Claims (6)

1. The photoacoustic imaging system is characterized by comprising a light source, a micro-ring resonant cavity detector array and a signal processing unit;

the micro-ring resonant cavity detector array comprises at least two paths of detector arrays, and each path of detector array comprises at least two micro-ring resonant cavities;

the light source is used for emitting laser signals, each micro-ring resonant cavity is used for generating corresponding resonant signals according to the laser signals, and the signal processing unit is used for correspondingly outputting image signals according to each resonant signal.

2. The photoacoustic imaging system of claim 1 wherein the light source is a wavelength tunable continuous wave laser for continuously emitting laser signals in the wavelength range 1530-1565 nm.

3. A photoacoustic imaging system according to claim 1, further comprising an optical fiber and a coupler;

the optical fiber and the coupler are arranged between the light source and the micro-ring resonant cavity.

4. The photoacoustic imaging system of claim 1 wherein the signal processing unit comprises a photo balance detector, an amplifier, a data acquisition card and a control display;

the photoelectric balance detector is electrically connected with the control display through the amplifier and the data acquisition card;

the photoelectric balance detector is used for converting the resonance signal into an electric signal, the amplifier is used for amplifying the electric signal to obtain an amplified signal, the data acquisition card is used for acquiring the amplified signal, and the control display is used for outputting an image signal according to the amplified signal.

5. The photoacoustic imaging system of claim 4 wherein the data acquisition card is configured with the same number of acquisition channels as the number of micro-ring resonators, each acquisition channel being for acquiring an amplified signal corresponding to a corresponding one of the micro-ring resonators.

6. The photoacoustic imaging system of claim 4 wherein the optical signal output spacing adjacent the micro-ring resonators is greater than the sampling spacing of the photo-balance detectors.