CN109567758B - Cross-scale photoacoustic imaging system - Google Patents
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Abstract
The invention provides a cross-scale photoacoustic imaging system, which comprises a laser light source, a light path system, a switching device, a sample and an ultrasonic transducer, wherein the laser light source is arranged on the sample; the switching device is used for irradiating the pulse laser in the optical path system to the sample and reflecting a photoacoustic signal generated by the sample to the ultrasonic transducer, and at least one ultrasonic transducer is fixed on the switching device; the switching device is arranged in the optical path system, the optical path system comprises a double-clad optical fiber, and the pulse laser is transmitted by the double-clad optical fiber and then irradiates the sample through the switching device and excites the acoustic signal. According to the trans-scale photoacoustic imaging system, the transmission of photoacoustic imaging exciting light with two different scales of optical resolution and acoustic resolution is realized by adopting the double-clad optical fiber, so that the cost of the trans-scale photoacoustic imaging system is greatly reduced; meanwhile, the switching device is used for reflecting the photoacoustic signals generated by the sample to the ultrasonic transducer, so that the detection range of the system is greatly widened.
Description
Technical Field
The invention relates to the field of biomedical image imaging, in particular to a cross-scale photoacoustic imaging system.
Background
Photoacoustic imaging (PAI) is a new biomedical imaging method that has been developed in recent years, both non-invasive and non-ionizing. The photoacoustic imaging is a novel hybrid imaging technology, has rich optical contrast and depth imaging capability, overcomes the defects of the limitation of pure optical imaging depth and poor contrast of pure ultrasonic imaging, and has wide biomedical clinical application. The principle of photoacoustic imaging is: biological tissue is excited by pulsed laser light, which produces photoacoustic signals (also ultrasonic waves) due to the momentary thermal expansion, which can be detected by an ultrasonic transducer to obtain information on the degree of absorption of light by the tissue. The frequency of the excited photoacoustic signal is different when the detected objects are different, so that if a system only has a detector in a certain frequency band, signals in a certain frequency band of the detected object can be missed.
Conventional photoacoustic microscopy systems are distinguished from imaging resolution and are mainly classified into optical resolution photoacoustic microscopy systems and acoustic resolution photoacoustic microscopy systems. Optical resolution photoacoustic microscopy systems are characterized in that the diameter of the excitation light spot in the system is smaller than the focal spot of the ultrasound transducer, so the imaging resolution of the system depends on the size of the excitation light spot. Acoustic resolution the light spot of a photoacoustic microscopy system is much larger than the detection area of an ultrasound transducer, and thus its imaging resolution depends on the focal spot size of the ultrasound transducer. The traditional optical resolution photoacoustic microscopy system has high resolution which can reach hundreds of nanometers to microns, but has shallow imaging depth of about 1-2 mm; conventional acoustic resolution photoacoustic microscopy systems have imaging depths on the order of centimeters, but have less resolution than the former, up to several hundred microns. Based on the advantages and disadvantages of the two, many groups of subjects are dedicated to combining two imaging modes into one system to realize cross-scale imaging.
The Wangli macro topic group of Washington university in 2013 firstly provides a trans-scale photoacoustic microscopic imaging system, and the system mainly utilizes an optical fiber bundle to realize trans-scale microscopic imaging. However, the optical fiber bundle in the system is composed of ten thousand single-mode fiber cores, so that the cost of the whole system is high, if one single-mode fiber in the optical fiber bundle is damaged, the whole optical fiber bundle needs to be replaced, so that the use cost of the system is extremely high, and the system can only use a single transducer, namely, only can collect photoacoustic signals of a single frequency band, so that the usable range of the system is limited.
In 2014, the germany Estrada group also proposed a trans-scale photoacoustic microscopy imaging system. The system mainly utilizes the distance between the mobile single-mode fiber and the self-focusing lens to realize the cross-scale microscopic imaging. The ultrasonic transducer in the system needs to be perforated, so that the detection efficiency of the ultrasonic transducer is greatly reduced. In the same year, the luo qing ming topic group of the science and technology university in china also proposed a cross-scale photoacoustic microscopy imaging system. The system mainly utilizes the optical fiber bundle to realize cross-scale microscopic imaging. The system has the following problems that firstly, the system uses a transmission type signal acquisition mode, the range of an imaged object is limited, and the object with the thickness more than several centimeters cannot be imaged; secondly, the system still adopts the optical fiber bundle so that the manufacturing cost and the use cost of the whole system are high.
In 2018, a four-mode cross-scale photoacoustic microscopic imaging system was proposed by the yaojunjie topic group of the university of ducke, usa. The system is characterized in that both the light spot and the sound spot can be changed. However, the ultrasonic transducers used in the system are all of a central opening structure, which will greatly reduce the receiving efficiency of the ultrasonic transducers, and the system has two frequencies because two ultrasonic transducers are intelligently accessed.
In order to achieve a good image signal-to-noise ratio, photoacoustic imaging has two key points: 1. photoacoustic co-axial, 2-light focusing and acoustic frequency matching. The optical axis of the exciting light coincides with the axis of the sound field of the ultrasonic transducer, so that after the exciting light irradiates on the surface of a sample, the photoacoustic signal is transmitted along the opposite direction of the axis, and can be well received by the ultrasonic transducer. Photoacoustic co-axial is the best "excitation-reception" approach. In order to achieve photoacoustic coaxiality, some subjects choose to perforate the middle of the ultrasonic transducer and let light exit from the center of the ultrasonic transducer, but this can greatly reduce the performance of the ultrasonic transducer and reduce the image signal-to-noise ratio.
Therefore, the following problems are ubiquitous in the existing trans-scale photoacoustic microscopic imaging system: firstly, a system needs to use an optical fiber bundle consisting of ten thousand single-mode optical fibers, so that the cost of the whole system is high, the replacement of a single optical fiber and the replacement of the whole optical fiber bundle cannot be realized, and the use cost is high; secondly, when the ultrasonic transducer is used in the system, the central hole of the ultrasonic transducer needs to be opened to achieve the photoacoustic coaxiality, so that the detection efficiency of the ultrasonic transducer is greatly reduced; thirdly, a mode of transmitting light to reflect ultrasound is adopted, but only a single ultrasonic transducer or two ultrasonic transducers can be accessed in the system, so that only a photoacoustic signal of a certain frequency band can be received, and the whole-frequency-band photoacoustic signal cannot be covered, that is, cross-scale photoacoustic imaging cannot be realized.
Disclosure of Invention
The invention aims to solve the defects that the cost of a system is high due to the fact that an optical fiber bundle needs to be used in the conventional trans-scale photoacoustic imaging system, and the detection range of the system is limited due to the fact that the system can only be accessed into a single ultrasonic transducer, and provides a trans-scale photoacoustic imaging system.
The technical scheme adopted by the invention for solving the technical problems is as follows: a cross-scale photoacoustic imaging system comprises a laser light source, a light path system, a switching device, a sample and an ultrasonic transducer; the laser light source is used for emitting pulse laser; the optical path system is used for transmitting the pulse laser between the laser light source and the sample, the switching device is used for irradiating the pulse laser in the optical path system onto the sample and reflecting a photoacoustic signal generated by the sample onto the ultrasonic transducer, and at least one ultrasonic transducer is fixed on the switching device; the ultrasonic transducer is used for receiving the photoacoustic signals and/or the self-generating and self-receiving ultrasonic signals reflected by the switching device; the switching device is arranged in the optical path system, the optical path system comprises a double-clad optical fiber, and the pulse laser irradiates the sample and excites the photoacoustic signal through the switching device after being transmitted by the double-clad optical fiber.
Further, the double-clad optical fiber includes a core, an inner cladding, and an outer cladding.
Specifically, the fiber core is used for transmitting excitation light in an optical resolution imaging mode, and the inner cladding is used for transmitting excitation light in an acoustic resolution imaging mode.
Further, the switching device comprises an inner shell, a light source entrance port and a light source exit port are formed in the inner shell along the light path direction, the sample is arranged at the light source exit port, and a signal exit port is further formed in the inner shell and perpendicular to the light path direction.
Specifically, the ultrasonic transducer is fixed at the signal exit for receiving the photoacoustic signal emitted by the sample.
Specifically, the switching device further comprises an outer shell sleeved on the outer side of the inner shell, the inner shell can rotate relative to the outer shell, a rotating shaft of the inner shell is parallel to the direction of the light path, an opening which can be communicated with a signal exit port of the inner shell is formed in the outer shell, and the ultrasonic transducer is fixed at the opening and used for receiving the photoacoustic signal sent by the sample.
Specifically, the switching device further includes an optical transmission-acoustic reflection structure disposed in the inner housing, the optical transmission-acoustic reflection structure transmitting the pulsed laser light transmitted in the optical path system to the sample and reflecting the photoacoustic signal excited by the sample, the optical transmission-acoustic reflection structure being disposed between the light source entrance port and the light source exit port, and the optical transmission-acoustic reflection structure forming an angle with the optical path direction, and the ultrasonic transducer being configured to receive the photoacoustic signal emitted from the sample and reflected by the optical transmission-acoustic reflection structure of the switching device.
Specifically, the trans-scale photoacoustic imaging system further comprises a mechanical scanning platform, and the switching device and the ultrasonic transducer are arranged in the mechanical scanning platform.
Furthermore, the optical path system further comprises a coupling lens arranged between the laser light source and the double-clad optical fiber, and the required light spot is coupled into the double-clad optical fiber by adjusting the coupling lens.
Specifically, the optical path system further comprises an imaging focusing lens arranged between the double-clad optical fiber and the switching device, and the imaging focusing lens is used for focusing light transmitted by the double-clad optical fiber on the sample.
The cross-scale photoacoustic imaging system provided by the invention has the beneficial effects that: the double-clad optical fiber is adopted to solve the transmission of the photoacoustic imaging excitation light with two different scales of optical resolution and acoustic resolution, and the problem that the whole optical path system needs to be replaced after the optical fiber bundle is adopted as the optical path transmission, which is caused by high cost and damage, is solved, so that the cost of the trans-scale photoacoustic imaging system is greatly reduced; meanwhile, the switching device is used for reflecting the photoacoustic signals generated by the sample to the ultrasonic transducer, so that holes do not need to be formed in the ultrasonic transducer, meanwhile, the ultrasonic transducer can be additionally arranged on the switching device to expand the detection frequency band of the cross-scale photoacoustic imaging system, and the detection range of the system is greatly expanded.
Drawings
FIG. 1 is a schematic diagram of a trans-scale photoacoustic imaging system provided by the present invention;
FIG. 2 is an end view of a double-clad optical fiber of a trans-scale photoacoustic imaging system provided by the present invention;
FIG. 3 is a schematic perspective view of an inner housing of a switching device of a trans-scale photoacoustic imaging system according to the present invention;
FIG. 4 is a front view of an inner housing of a switching device of a trans-scale photoacoustic imaging system provided by the present invention;
FIG. 5 is a schematic perspective view of a housing of a switching device of a trans-scale photoacoustic imaging system provided by the present invention;
FIG. 6 is a schematic perspective view of a switching device of a trans-scale photoacoustic imaging system according to the present invention;
fig. 7 is a schematic perspective view of an assembled switching device and an ultrasonic transducer of the trans-scale photoacoustic imaging system provided by the present invention.
In the figure: 100-trans-scale photoacoustic imaging system
10-laser light source 20-optical path system 30-switching device
40-sample 50-ultrasonic transducer 60-mechanical scanning platform
21-double-clad fiber 22-coupling lens 23-imaging focusing lens
211-core 212-inner cladding 213-outer cladding
24-Beam processing System 31-housing 311-opening
312-through hole 32-inner shell 33-light transmission-sound reflection structure
321-light source entrance port 322-light source exit port 323-signal exit port
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Referring to fig. 1, a cross-scale photoacoustic imaging system 100 provided by the present invention includes a laser light source 10, an optical path system 20, a switching device 30, a sample 40, and an ultrasonic transducer 50. The laser light source 10 is used for emitting a pulse laser light source, and the light beam processing system 24 arranged in front of the laser light source shapes the light spot of the pulse laser light emitted by the laser light source 10 and then collimates the light spot in the output optical path system 20. The optical path system 20 is used for transmitting the pulse laser between the laser light source 10 and the sample 40, the optical path system 20 includes a double-clad fiber 21, and the double-clad fiber 21 is used for realizing the transmission of the excitation light of two photoacoustic imaging modes, namely "optical resolution" and "acoustic resolution". The switching device 30 is disposed in the optical path system 20 and located between the double-clad fiber 21 and the sample 40, and the pulse laser is transmitted through the double-clad fiber 21 and then transmitted to the sample 40 through the switching device 30. The switching device 30 is used for irradiating the pulsed laser light transmitted in the optical path system 20 onto the sample 40 and reflecting the photoacoustic signal generated by the sample 40 onto the ultrasonic transducer 50, the switching device 30 is used for fixing at least one ultrasonic transducer 50, and the fixed ultrasonic transducer 50 can be ultrasonic transducers 50 with different frequencies and different functions. The ultrasonic transducer 50 is used for receiving the photoacoustic signal reflected by the switching device 30 and/or the self-receiving ultrasonic signal. The ultrasonic transducer 50 can be used for self-generating and self-receiving ultrasonic signals, and the signals of the ultrasonic transducer need to be switched by the switching device 30. The switching device 30 is disposed in the optical path system 20, and is configured to transmit the pulse laser emitted by the laser light source 10, and further change a propagation path of a photoacoustic signal emitted by the sample 40, so that the propagation path of the photoacoustic signal is perpendicular to the optical path direction, and thus a plurality of ultrasound transducers 50 can be disposed on a perpendicular plane of the optical path direction by rotating the switching device 30 to receive the photoacoustic signal emitted by the sample 40, and the switching device 30 can increase the number of the ultrasound transducers 50 by changing an emitting direction of the photoacoustic signal emitted by the sample 40, so that access of the plurality of ultrasound transducers 50 can be achieved without forming a hole on the ultrasound transducer 50, and coaxial propagation of the photoacoustic signal is ensured, so that the trans-scale photoacoustic imaging system 100 can simultaneously access the plurality of ultrasound transducers 50 to receive signals of a plurality of frequency bands, and achieve signal detection of a wide frequency band, can almost cover the common signals from low frequency to high frequency.
Further, as shown in fig. 2, the double-clad optical fiber 21 includes a core 211, an inner cladding 212, and an outer cladding 213. The optical path system 20 in the cross-scale photoacoustic imaging system 100 provided by the invention adopts the double-clad optical fiber 21 as a light source transmission path, can realize free switching transmission of optical resolution and acoustic resolution in the working process of the system, is simple to operate, and can replace a traditional optical fiber bundle structure, so that the cost of the optical path system 20 is lower, and the transmission of two cross-scale photoacoustic imaging is realized. Specifically, the core 211 is used for transmitting the excitation light for the optical resolution imaging mode, and the inner cladding 212 is used for transmitting the excitation light for the acoustic resolution imaging mode.
Further, the photoacoustic microscopy systems are mainly classified into optical fiber resolution photoacoustic microscopy systems and acoustic resolution photoacoustic microscopy systems. The optical path system 20 further includes a coupling lens 22 disposed between the laser source 10 and the double-clad fiber 21, and the coupling lens 22 is adjusted to obtain the desired spot to be coupled into the double-clad fiber 21. By adjusting the position of the coupling lens 22, the size of the light spot can be freely switched. The imaging resolution of the trans-scale photoacoustic imaging system 100 provided by the present invention depends on the size of the excitation spot. When performing optical resolution photoacoustic imaging, light is coupled into the center of the double-clad fiber 21, i.e., into the core 211, through the coupling lens 22, and the light source is transmitted through the core 211 of the double-clad fiber 21. When the acoustic resolution imaging is performed, the distance between the coupling lens 22 and the double-clad optical fiber 21 is adjusted, so that the emergent light spot passing through the coupling lens 22 is irradiated on the inner cladding 212 of the double-clad optical fiber 21, and the light source is transmitted through the double-clad optical fiber 21. Therefore, the pulse laser light source emitted by the laser light source 10 is collimated by the light beam processing system 24 in the optical path system 20, and then enters the coupling lens 22, and the coupling lens 22 adjusts the light spot entering the double-clad optical fiber 21, and then the double-clad optical fiber 21 is used for light source transmission. The double-clad fiber 21 has high coupling efficiency, and the imaging mode of the system can be freely switched through the coupling lens 22, so that the operation is simple and the realization is easy.
Further, as shown in fig. 1, the optical path system 20 further includes an imaging focusing lens 23 disposed between the double-clad optical fiber 21 and the switching device 30, and the imaging focusing lens 23 is configured to focus light transmitted by the double-clad optical fiber 21 onto the sample 40. The imaging focusing lens 23 focuses the pulse laser transmitted by the double-clad fiber 21 and then directly irradiates the sample 40 through the switching device 30. The sample 40 generates a photoacoustic signal under the excitation of the pulsed laser, the photoacoustic signal is conducted to the switching device 30, and the photoacoustic signal is conducted into the ultrasonic transducer 50 by the reflection of the switching device 30 for the ultrasonic transducer 50 to detect.
Further, the trans-scale photoacoustic imaging system 100 provided by the present invention further comprises a mechanical scanning platform 60, and the switching device 30 and the ultrasound transducer 50 are disposed in the mechanical scanning platform 60. Meanwhile, the double-clad optical fiber 21 and the imaging focusing lens 23 in the optical path system 20 are also disposed in the mechanical scanning platform 60. The function of the cross-scale photoacoustic imaging system 100 of zigzag line-by-line scanning on the sample 40 can be realized by the mechanical scanning platform 60. The switching device 30 and the ultrasonic transducer 50 need to be placed in a water tank, in which a transparent liquid for transmitting photoacoustic signals is contained, and water is generally used as a transmission medium. The sample 40 is arranged at the bottom of the mechanical scanning platform 60, the switching device 30 is arranged in the water tank, and by using the water in the water tank as the photoacoustic couplant, when the sample 40 is excited and irradiated by the pulse laser output by the double-clad fiber 21 to generate a photoacoustic signal, the photoacoustic signal propagates in the water tank, and the photoacoustic signal propagation path changes when encountering the switching device 30, so that the detection direction of the ultrasonic transducer 50 is changed.
Specifically, as shown in fig. 3 to 4, the switching device 30 includes an inner housing 32, a light source entrance port 321 and a light source exit port 322 are disposed on the inner housing 32 along a light path direction, the sample 40 is disposed at the light source exit port 322, and a signal exit port 323 is further disposed on the inner housing 32 perpendicular to the light path direction. The light source output from the double-clad fiber 21 is irradiated from top to bottom through the switching device 30 onto the sample 40 located below the switching device 30. The optical path direction of the switching device 30 is from top to bottom as shown in fig. 1. Therefore, a light source entrance port 321 is provided above the inner case 32, a light source exit port 322 is provided below the inner case 32, and the light source enters from the light source entrance port 321 of the inner case 32 and exits from the light source exit port 322 to irradiate the sample 40. Therefore, when the sample 40 is excited to generate a photoacoustic signal and propagates in the water tank 60, the ultrasonic transducer 50 is fixed at the signal outlet 322 for receiving the photoacoustic signal emitted by the sample 40, and at this time, the receiving port of the ultrasonic transducer 50 only needs to be arranged toward the direction of the sample 40, so that the ultrasonic transducer 50 can receive the photoacoustic signal emitted by the sample 40.
Further, in order to improve the acceptance rate of the photoacoustic signal emitted by the sample 40 received by the ultrasonic transducer 50, a photoacoustic coaxial effect is achieved. As shown in fig. 1, the switching device 30 further peels off the light transmission-sound reflection structure 33 disposed in the inner housing and used for transmitting the pulsed laser light transmitted in the optical path system 20 to the sample 40 and reflecting the photoacoustic signal excited by the sample 40, the light transmission-sound reflection structure 33 is disposed between the light source incident port 321 and the light source exit port 322, and the light transmission-sound reflection structure 33 forms an angle with the optical path direction, while the ultrasonic transducer 50 fixed at the signal exit port 323 of the inner housing 32 only needs to be disposed along the direction of the photoacoustic signal reflected by the light transmission-sound reflection structure 33 to realize photoacoustic co-axis, and the ultrasonic transducer 50 is used for receiving the photoacoustic signal emitted from the sample 40 and reflected by the light transmission-sound reflection structure 33 of the switching device 30. In this embodiment, the light transmitting-sound reflecting structure 33 is a light-transmitting glass sheet, and the glass sheet can be arranged to well transmit the pulsed laser light output from the double-clad fiber 21 to the sample 40 and reflect the photoacoustic signal emitted from the sample 40 to the ultrasonic transducer 50. The light transmitting-sound reflecting structure 33 forms an angle with the light path direction, so that the photoacoustic signal emitted from the sample 40 is reflected by the light transmitting-sound reflecting structure 33 and emitted in the direction deviating from the light path direction, i.e. the reflected photoacoustic signal will be emitted toward the side of the shell of the inner shell 32. Preferably, the light transmitting-sound reflecting structure 33 forms an angle of 45 ° with the direction of the light path, so that the photoacoustic signal of the sample 40 reflected by the light transmitting-sound reflecting structure 33 is in line with the direction of the horizontally arranged ultrasonic transducer 50, thereby achieving photoacoustic coaxiality. The light transmitting-sound reflecting structure 33 located in the switching means 30 does not change the irradiation path of the light source, but only changes the propagation path of the photoacoustic signal in water. The photoacoustic signal travels against the optical path direction and meets the obstruction change path of the light transmission-sound reflection structure 33, so that the photoacoustic signal is transmitted out from the side of the switching device 30 with a rotation of 90 °, and at this time, the photoacoustic signal whose propagation path is changed by the light transmission-sound reflection structure 33 is transmitted out from the signal exit port 323 located on the side of the inner case 32. Therefore, as shown in fig. 1, the ultrasonic transducer 50 in the trans-scale photoacoustic imaging system 100 is fixed at the signal exit port 323 for receiving the photoacoustic signals reflected by the light transmitting-acoustic reflecting structure 33 and/or the self-receiving ultrasonic signals. Only one ultrasonic transducer 50 is provided in the imaging system 100 for detecting photoacoustic signals emitted from the sample 40, and when trans-scale photoacoustic imaging is required, the ultrasonic transducer 50 can be replaced.
Further, as shown in fig. 5, in the trans-scale photoacoustic imaging system 100 provided by the present invention, the switching device 30 further includes an outer shell 31 sleeved outside the inner shell 32. As shown in fig. 6, the inner shell 32 is sleeved in the outer shell 31. The inner housing 32 is rotatable relative to the outer housing 31, and the rotation axis of the inner housing 32 is parallel to the optical path direction. The inner shell 32 and the outer shell 31 may be configured as cylindrical structures sleeved with each other, or may be configured as a 32-bit cylindrical structure of the inner shell as shown in fig. 6, and the outer shell 31 is a rectangular structure. As shown in fig. 5, the outer shell 31 is provided with an opening 311 capable of communicating with the signal exit port 323 of the inner shell 32, and the ultrasonic transducer 50 is fixed at the opening 311 for directly receiving the photoacoustic signal emitted from the sample 40. The light transmitting-sound reflecting structure 33 is disposed in the inner case 32, and the ultrasonic transducer 50 is used for receiving the photoacoustic signal reflected by the light transmitting-sound reflecting structure 33. The switching device 30 further includes an outer shell 31, and the outer shell 31 and the inner shell 32 can rotate relatively, so that in the photoacoustic signal propagation direction of the inner shell 32, a plurality of ultrasonic transducers 50 can be added at the same time for detecting photoacoustic signals, thereby widening the detection range of the system. During the operation of the system 100, the detection of the desired frequency can be achieved by rotating the relative positions of the inner housing 32 and the outer housing 31 such that the signal exit port 323 on the inner housing 32 communicates with the opening of the ultrasonic transducer 50 corresponding to the detection frequency. In the trans-scale photoacoustic imaging system 100 provided by the present invention, the outer shell 31 of the switching device 30 can be simultaneously connected to the plurality of ultrasound transducers 50, the detection frequency can be adjusted by the relative rotation of the inner shell 32 and the outer shell 31, and the switching device 30 does not need to form holes on the ultrasound transducers 50, thereby avoiding the problem of the detection efficiency reduction of the ultrasound transducers 50 caused by the holes.
By the arrangement of the switching means 30, the number of the ultrasonic transducers 50 can be increased at the same time. The addition of ultrasound transducers 50 may select ultrasound transducers 50 of the same frequency but different modes. Namely, the ultrasonic transducers 50 arranged outside the switching device 50 are the focused ultrasonic transducer 50 and the unfocused ultrasonic transducer 50 of the same frequency. Since the lateral resolution in the photoacoustic imaging of the acoustic resolution is determined by the detection focus area of the ultrasonic transducer 50, photoacoustic images of different scales can be simultaneously obtained even if the ultrasonic transducers 50 of different modes are set at the same frequency on the switching device 30. Alternatively, the same mode may be selected for the additional ultrasonic transducers 50, but at different probing frequencies. Since the detection frequency of the ultrasonic transducer 50 will image the longitudinal resolution of the image, the higher the detection frequency, the higher the longitudinal resolution, therefore, although the focusing manner is consistent, the photoacoustic images of different scales can be obtained at the same time. Or, the additional ultrasonic transducer 50 can select ultrasonic transducers with different modes and different detection frequencies to meet the requirements of photoacoustic images with different scales.
Specifically, as shown in fig. 7, a schematic perspective view of the cross-scale photoacoustic imaging system 100 provided by the present invention is shown after the switching device 30 and the ultrasonic transducer 50 are assembled. As shown in fig. 7, the trans-scale photoacoustic imaging system 100 includes four ultrasound transducers 50, and the corresponding outer housing 31 of the switching device 30 is rectangular, so that a through hole 312 is formed vertically therethrough, and four side faces are formed horizontally, and correspondingly, each side face is provided with four openings 311, and the inner housing 32 is cylindrical, and the inner housing 32 is sleeved at the through hole 312 of the outer housing 31, and the inner housing 32 can rotate relatively in the through hole 312 of the outer housing 31. The relative rotation between the inner shell 32 and the outer shell 31 can be manually adjusted or can be electrically controlled. And the opening 311 on the outer shell 31 can communicate with the signal exit port 323 of the inner shell 32 through the relative rotation of the inner shell 32 and the outer shell 31, and the four ultrasonic transducers 50 are respectively fixed at the four openings 311. By rotating the inner housing 32 and the outer housing 31, different ultrasonic transducers 50 can be freely switched to detect photoacoustic signals emitted by the sample 40, and the ultrasonic transducers 50 acquire the photoacoustic signals and perform ultrasonic imaging at the same time. In the present embodiment, the four ultrasonic transducers 50 respectively adopt different probing frequencies, the probing frequencies of the four ultrasonic transducers 50 are respectively 5MHz, 10MHz, 30MHz, and 75MHz, and the bandwidth of the ultrasonic transducer 50 is 100%, so their probing frequency ranges are respectively 2.5MHz-7.5MHz, 5MHz-15MHz, 15MHz-45MHz, and 38.5MHz-113.5 MHz. Therefore, in the trans-scale photoacoustic imaging system 100 provided by the invention, the switching device 30 is used, and the four ultrasonic transducers 50 are additionally arranged, so that the covered detection range is 2.5MHz-113.5MHz, and the signals almost covering the common low-frequency to high-frequency range are realized.
According to the trans-scale photoacoustic imaging system 100 provided by the invention, on one hand, the transmission of photoacoustic imaging with two different scales of optical resolution and acoustic resolution is solved by adopting the double-clad optical fiber 21, and the problem that the whole optical path system needs to be replaced after the whole optical path system is damaged due to high cost caused by adopting an optical fiber bundle as an optical path transmission is solved, so that the cost of the trans-scale photoacoustic imaging system is greatly reduced; on the other hand, the switching device 30 is used for reflecting the photoacoustic signal generated by the sample 40 to the ultrasonic transducer 50, so that no hole needs to be formed in the ultrasonic transducer 50, and the ultrasonic transducer 50 can be additionally arranged on the switching device 30 to expand the detection frequency band of the cross-scale photoacoustic imaging system 100, thereby greatly widening the detection range of the system.
The present invention is not limited to the above preferred embodiments, and any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A cross-scale photoacoustic imaging system is characterized by comprising a laser light source, an optical path system, a switching device, a sample and an ultrasonic transducer; wherein the content of the first and second substances,
the laser light source is used for emitting pulse laser;
the optical path system is used for transmitting the pulse laser between the laser light source and the sample;
the switching device is used for irradiating the pulsed laser in the optical path system onto the sample and reflecting a photoacoustic signal generated by the sample onto the ultrasonic transducer, and at least one ultrasonic transducer is fixed on the switching device;
the switching device comprises an inner shell and an outer shell sleeved outside the inner shell, wherein the inner shell can rotate relative to the outer shell so as to realize the adjustment of detection frequency through the ultrasonic transducers with different connection frequencies and/or modes;
the ultrasonic transducer is used for receiving the photoacoustic signals and/or the self-generating and self-receiving ultrasonic signals reflected by the switching device;
the switching device is arranged in the optical path system, the optical path system comprises a double-clad optical fiber, and the pulse laser irradiates the sample and excites the photoacoustic signal through the switching device after being transmitted by the double-clad optical fiber.
2. The trans-scale photoacoustic imaging system of claim 1 wherein the double-clad fiber comprises a core, an inner cladding and an outer cladding.
3. The system of claim 2, wherein the core is configured for optical resolution imaging mode excitation light transmission and the inner cladding is configured for acoustic resolution imaging mode excitation light transmission.
4. The trans-scale photoacoustic imaging system as set forth in claim 1, wherein the inner housing has a light source entrance port and a light source exit port along a light path, the sample is disposed at the light source exit port, and the inner housing has a signal exit port perpendicular to the light path.
5. A trans-scale photoacoustic imaging system as set forth in claim 4, wherein said ultrasound transducer is fixed at said signal exit port for receiving said photoacoustic signal from said sample.
6. The system according to claim 4, wherein the rotation axis of the inner housing is parallel to the optical path, the outer housing has an opening that can communicate with the signal exit port of the inner housing, and the ultrasonic transducer is fixed at the opening for receiving the photoacoustic signal from the sample.
7. A trans-scale photoacoustic imaging system as set forth in claim 5 or 6, wherein said switching device further comprises an optical transmission-acoustic reflection structure disposed in said internal housing for transmitting the pulsed laser light transmitted in said optical path system to said sample and reflecting the photoacoustic signal excited by said sample, said optical transmission-acoustic reflection structure being disposed between said light source entrance port and said light source exit port, and said optical transmission-acoustic reflection structure forming an angle with said optical path direction, said ultrasonic transducer being used for receiving the photoacoustic signal emitted from said sample reflected by said optical transmission-acoustic reflection structure of said switching device.
8. The trans-scale photoacoustic imaging system of claim 4 wherein the trans-scale photoacoustic imaging system further comprises a mechanical scanning platform, and wherein the switching means and the ultrasound transducer are disposed within the mechanical scanning platform.
9. The system of claim 2, wherein the optical path system further comprises a coupling lens disposed between the laser source and the double-clad fiber, and the coupling lens is adjusted to obtain a desired spot coupling into the double-clad fiber.
10. The system of claim 9, wherein the optical path system further comprises an imaging focusing lens disposed between the double-clad fiber and the switching device, the imaging focusing lens configured to focus light transmitted by the double-clad fiber onto the sample.
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| CN110595607B (en) * | 2019-09-25 | 2020-11-24 | 南京大学 | Photoacoustic point source-based water-immersed transducer sound field characterization equipment and use method thereof |
| CN112414948B (en) * | 2020-11-20 | 2022-12-06 | 南方科技大学 | Photoacoustic imaging system and method |
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| US8454512B2 (en) * | 2007-10-25 | 2013-06-04 | Washington University | Confocal photoacoustic microscopy with optical lateral resolution |
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