CN106066306A - A kind of photoacoustic microscope system - Google Patents

Abstract

This application discloses a photoacoustic microscope system. The laser light source is used to emit pulsed laser light and form linearly polarized light after passing through a polarizer. The light irradiates the tissue, the photoacoustic signal receiving device located at the other end of the tissue receives the photoacoustic signal, converts the acoustic signal into an electrical signal, the data acquisition and processing device collects the electrical signal and saves the data, and obtains the 3D image of the tissue through 3D reconstruction and Cross-sectional image. In the specific implementation manner of the present application, since the spatial light modulator is introduced into the optical path, the optical focal depth can be significantly increased, thereby realizing large focal depth and high-resolution photoacoustic imaging. This application does not need to use an axicon to generate a Bessel beam, which solves the problem of the loss of luminous flux of the axicon, and does not need two short intervals of laser irradiation to eliminate the influence of the Bessel beam side lobe, and simplifies the design and components of the experimental device Cost, but also to avoid high-energy thermal relaxation effect irradiation on biological tissue damage.

Description

A Photoacoustic Microscope System

technical field

The present application relates to the field of photoacoustic imaging, in particular to a photoacoustic microscope system.

Background technique

Photoacoustic imaging based on light absorption characteristics organically combines two methods of light excitation and acoustic detection. Pigment substances in biological tissues absorb pulsed laser light and convert them into thermal energy. Due to the instantaneous thermoelastic effect, broadband ultrasonic waves (ie, photoacoustic signals) are released outward, and the light absorption characteristics of tissues can be measured by detecting photoacoustic signals. The rapid development of optical resolution photoacoustic microscopy in recent years has improved the lateral resolution to the micron level, and can image the blood microcirculation system in vivo with high precision, including main vessels at all levels, capillaries, and even individual red blood cells. By analyzing the depth position of the pigment substance through the transit time of the photoacoustic signal, the optical resolution photoacoustic microscope only needs to scan the sample in a two-dimensional plane to obtain a three-dimensional microstructure image of the tissue. However, traditional optical resolution photoacoustic microscopy uses a Gaussian beam, which is limited by the Rayleigh length, and the optical depth of focus is small. Ordinary optical-resolution photoacoustic microscopy uses an objective lens with a numerical aperture of 0.1 to focus the excitation beam, which can achieve a lateral resolution of about 6 microns, but the depth of focus that maintains this resolution is only about 100 microns. When the imaging area exceeds this depth range, the lateral resolution of the system will degrade rapidly.

Existing optical resolution photoacoustic microscopes use objective lenses to focus the excitation beam, and the resulting Gaussian beam has a short depth of focus, resulting in imaging resolution that is only consistent over a small depth region (typically less than 100 microns) . Although the Bessel beam produced by the axicon prism has a large depth of focus, the beam side lobes seriously affect the resolution and image quality. The thermal relaxation effect generated by continuous photoexcitation at short time intervals can weaken the influence of Bessel beam side lobes to a certain extent. However, the ineffective side lobes of the beam in this method will lose a lot of light energy, and multiple laser irradiations greatly prolong the imaging time, and at the same time cause photodamage to the tissue. In addition, the generation of excitation light at short intervals usually requires two lasers, increasing the complexity and cost of the imaging system.

Contents of the invention

The technical problem to be solved in this application is to provide a photoacoustic microscope system for the deficiencies of the prior art.

The technical problem to be solved in this application is solved through the following technical solutions:

A photoacoustic microscope system, including a laser light source, a polarizer, a shaping optical path, a photoacoustic signal receiving device, and a data acquisition and processing device, and also includes a spatial light modulator, the laser light source is used to emit pulsed laser light and pass through the After the polarizer forms linearly polarized light, after being collimated and expanded by the shaping optical path, it is incident on the surface of the spatial light modulator, and the modulated pulsed light irradiates the tissue, and the photoacoustic signal receiving device located at the other end of the tissue receives the light Acoustic signal, converting the acoustic signal into an electrical signal, the data collection and processing device collects the electrical signal and saves the data, and obtains a three-dimensional image and a cross-sectional image of the tissue through three-dimensional reconstruction.

The data acquisition and processing device includes a controller and a data acquisition card, and the controller controls the data acquisition card to use the electrical pulse signal output by the laser light source as a synchronization signal to collect data on the electrical signal.

The controller is integrated on a PC or a graphics workstation, and the data acquisition card is integrated on a PC or a graphics workstation.

The controller is an independent device, and the data acquisition card is integrated on a PC or a graphics workstation.

A three-dimensional displacement device is also included, and the three-dimensional displacement device enables the light beam to scan the tissue in a two-dimensional plane, so as to obtain the two-dimensional data required by the three-dimensional image stack.

The spatial light modulator includes a phase-type spatial light modulator.

The photoacoustic signal receiving device includes an ultrasonic probe.

A signal amplifier for amplifying the electrical signal is also included.

The device forming the shaping optical path includes a first collimating beam expanding device, a mirror, a second collimating beam expanding device and a focusing lens, and the linearly polarized light is collimated and expanded by the first collimating beam expanding device , irradiate on the reflector, reflect to the spatial light modulator through the reflector, and then collimate and expand the beam through the second collimating beam expander, and irradiate the tissue through the focusing lens .

The device forming the shaping optical path also includes a third collimating beam expanding device, the light irradiated on the mirror is collimated and expanded by the third collimating beam expanding device and then enters the spatial light modulation device surface.

Owing to adopting above technical scheme, the beneficial effect that makes this application possess is:

In the specific implementation of the present application, since the spatial light modulator is introduced into the optical path to modulate the wavefront of the focused beam, it is equivalent to adding an optical mask on the main plane of the focusing lens, and the system achieves a higher The light transmission rate makes full use of light energy, effectively improves the signal-to-noise ratio, and can significantly increase the optical focal depth, thereby realizing large focal depth and high-resolution photoacoustic imaging. This application does not need to use an axicon to generate Bessel beams, thereby solving the problem of the loss of luminous flux of the axicon. At the same time, this application does not need continuous light excitation at short intervals, which simplifies the design of the experimental device and the cost of components, and also avoids high-energy heat dissipation. Relaxation effect radiation damage to biological tissue.

Description of drawings

Figure 1(a) is an unmodulated binary optical image;

Figure 1(b) is a binary optical image modulated by a spatial light modulator;

Figure 2(a) is a cross-sectional view of the beam focus without modulation;

Figure 2(b) is a cross-sectional view of the focal point of the beam modulated by the spatial light modulator;

FIG. 3 is a schematic structural diagram of the system of the present application in an embodiment;

Fig. 4 is a schematic structural diagram of the system of the present application in another embodiment.

detailed description

The present invention will be further described in detail below through specific embodiments in conjunction with the accompanying drawings.

In this application, a liquid crystal spatial light modulator is used to modulate the wavefront of the incident beam, thereby significantly improving the optical resolution of the imaging focal depth of the photoacoustic microscope. The liquid crystal spatial light modulator is the core component to realize the wavefront shaping of the beam. The binary image shown in Fig. The beam wavefront at the modulator surface changes accordingly. In the optical path of the system, the photoacoustic excitation beam is incident on the surface of the spatial light modulator, and the specific light mode loaded on the spatial light modulator (as shown in Figure 1(b) will affect the wavefront distribution of the beam, after being focused by the microscope objective lens , forming the light spatial distribution shown in Figure 2(b). Figure 2(a) is the y-z cross-sectional view of the beam focus after loading Figure 1(a), and the Rayleigh length is very short; Figure 2(b) is loading Figure 1(b) The y-z cross-sectional view of the rear beam focus, the stretching of the Rayleigh length can be significantly observed, and the longitudinal length is greatly increased without losing the lateral dimension of the beam. Obviously, compared with the unmodulated optical focus (As shown in Figure 1(a) and Figure 2(a)), this scheme improves the focal depth of the incident excitation beam, making the lateral resolution of photoacoustic imaging consistent in a larger depth range, which is conducive to improving the imaging quality .

As shown in Figure 3 and Figure 4, the photoacoustic microscope system of the present application, one embodiment, includes a laser light source 100, a polarizer 200, a shaping optical path 300, a photoacoustic signal receiving device 400, a data acquisition and processing device 500 and Spatial light modulator 600. The laser light source 100 is used to emit pulsed laser light and form linearly polarized light after passing through the polarizing plate 200. After being collimated and expanded by the shaping optical path 300, it is incident on the surface of the spatial light modulator 600. The modulated pulsed light irradiates the tissue, located on the other side of the tissue The photoacoustic signal receiving device 400 at one end receives the photoacoustic signal and converts the acoustic signal into an electrical signal. The data acquisition and processing device 500 collects the electrical signal and saves the data, and obtains a three-dimensional image and a cross-sectional image of the tissue through three-dimensional reconstruction. In one embodiment, the spatial light modulator of the present application includes a phase-type spatial light modulator. The photoacoustic signal receiving device 400 may include an ultrasound probe.

The data acquisition and processing device includes a controller and a data acquisition card. The controller controls the data acquisition card to use the electrical pulse signal output by the laser light source as a synchronous signal to collect data on the electrical signal. In one embodiment, the controller can be integrated on a PC or a graphics workstation, and the data acquisition card can be integrated on a PC or a graphics workstation. In another embodiment, the controller is an independent device, and the data acquisition card can be integrated on a PC or a graphics workstation.

The photoacoustic microscope system of the present application may also include a three-dimensional displacement device 700, which enables the light beam to perform two-dimensional plane scanning on the tissue, so as to obtain the two-dimensional data required by the three-dimensional image stack.

In one embodiment, the photoacoustic microscope system of the present application may further include a signal amplifier 800 for amplifying the electrical signal converted by the photoacoustic signal receiving device 400 .

The components forming the shaping optical path 300 include a first collimator and beam expander 310 , a mirror 320 , a second collimator and beam expander 330 and a focusing lens 340 . After the linearly polarized light is collimated and expanded by the first collimating beam expander 310, it is irradiated on the mirror 320, reflected by the mirror 320 to the spatial light modulator, and then collimated by the second collimating beam expander 330. After direct expansion, the beam is irradiated onto the tissue through the focusing lens 340 . The collimating beam expander generally includes a focusing lens and a collimating lens, the focusing lens is used to focus the light beam, and the collimating lens is used to collimate the emitted light beam expansion.

In one embodiment, the device forming the shaping optical path 300 may also include a third collimating beam expanding device (not shown in the figure), and the light irradiated on the mirror 320 is collimated by the third collimating beam expanding device The expanded beam is then incident on the surface of the spatial light modulator 600 . In another embodiment, the device forming the shaping optical path 300 may also include a pinhole filter 350, after the linearly polarized light is collimated and expanded by the first collimating beam expander 310, it can be filtered out by the pinhole filter 350. The stray light at the edge of the light beam is then irradiated onto the reflector 320 .

The above content is a further detailed description of the present invention in conjunction with specific embodiments, and it cannot be assumed that the specific implementation of the present invention is limited to these descriptions. Those of ordinary skill in the technical field to which the present invention belongs can also make some simple deduction or replacement without departing from the concept of the present invention.

Claims (10)

1. A photoacoustic microscope system, comprising a laser light source, a polarizer, a shaping optical path, a photoacoustic signal receiving device, and a data acquisition and processing device, is characterized in that it also includes a spatial light modulator, and the laser light source is used to emit The pulsed laser light passes through the polarizer to form linearly polarized light. After being collimated and expanded by the shaping optical path, it is incident on the surface of the spatial light modulator. The modulated pulsed light irradiates the tissue, and the light at the other end of the tissue The acoustic signal receiving device receives the photoacoustic signal and converts the acoustic signal into an electrical signal. The data collection and processing device collects the electrical signal and saves the data, and obtains a three-dimensional image and a cross-sectional image of the tissue through three-dimensional reconstruction. 2. The photoacoustic microscope system according to claim 1, wherein the data acquisition and processing device comprises a controller and a data acquisition card, and the controller controls the output of the data acquisition card with the laser light source The electrical pulse signal is used as a synchronous signal to collect data from the electrical signal. 3. The photoacoustic microscope system according to claim 2, wherein the controller is integrated on a PC or a graphics workstation, and the data acquisition card is integrated on a PC or a graphics workstation. 4. The photoacoustic microscope system according to claim 2, wherein the controller is an independent device, and the data acquisition card is integrated on a PC or a graphics workstation. 5. The photoacoustic microscope system according to claim 1, further comprising a three-dimensional displacement device, the three-dimensional displacement device enables the light beam to scan the tissue in a two-dimensional plane to obtain the two-dimensional data required by the three-dimensional image stack . 6. The photoacoustic microscope system according to claim 1, wherein the spatial light modulator comprises a phase-type spatial light modulator. 7. The photoacoustic microscope system according to claim 1, wherein the photoacoustic signal receiving device comprises an ultrasonic probe. 8. The photoacoustic microscope system according to claim 7, further comprising a signal amplifier for amplifying the electrical signal. 9. The photoacoustic microscope system according to any one of claims 1 to 8, wherein the device forming the reshaping optical path comprises a first collimator beam expander, a mirror, a second collimator beam expander and a focusing lens, after the linearly polarized light is collimated and expanded by the first collimator and beam expander, it is irradiated onto the reflector, reflected by the reflector to the spatial light modulator, and then passed through the After the beam is collimated and expanded by the second collimating beam expanding device, the beam is irradiated onto the tissue through the focusing lens. 10. The photoacoustic microscope system as claimed in claim 9, wherein the device forming the optical path shaping further comprises a third collimator and beam expander, and the light irradiated on the mirror passes through the third collimator. The beam is collimated and expanded by the direct beam expander before it is incident on the surface of the spatial light modulator.