CN109497964B - Human blood vessel detection system based on laser photoacoustic spectroscopy - Google Patents
Human blood vessel detection system based on laser photoacoustic spectroscopy Download PDFInfo
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/0059—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence
- A61B5/0075—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence by spectroscopy, i.e. measuring spectra, e.g. Raman spectroscopy, infrared absorption spectroscopy
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/0093—Detecting, measuring or recording by applying one single type of energy and measuring its conversion into another type of energy
- A61B5/0095—Detecting, measuring or recording by applying one single type of energy and measuring its conversion into another type of energy by applying light and detecting acoustic waves, i.e. photoacoustic measurements
Abstract
The invention discloses a human body blood vessel detection system based on laser photoacoustic spectroscopy, which mainly comprises a main controller, a scanning head, a three-dimensional electric platform and auxiliary components. The invention has the advantages that the volume and the cost of the system are reduced by multiplexing the laser optoacoustic and the laser Raman light source and part of the light path; by taking photoacoustic echoes of blood flow in a blood vessel as a spatial analysis reference and adopting time domain resolution photoacoustic echo signal analysis, photoacoustic echo signals corresponding to layered substances of the blood flow, the internal tissue of the blood vessel and the vascular wall passing through a main shaft path at the same moment can be analyzed, and the simultaneous detection of the external appearance and the internal tissue shape distribution of the blood vessel by photoacoustic can be realized; the photoacoustic and laser Raman are combined, and the molecular components of layered substances of the vascular wall can be detected.
Description
Technical Field
The invention relates to a human body blood vessel detection system, in particular to a detection system based on the combination of laser optoacoustic and laser Raman, which is suitable for detecting the internal and external three-dimensional structures and molecular components of human body arteriovenous vessels and belongs to the field of photoelectric detection.
Background
Angiography is an auxiliary examination technology for monitoring the health condition of blood vessels, is widely used for diagnosis and treatment of various clinical diseases, is helpful for doctors to find the state of an illness in time, controls the progress of the illness and effectively improves the survival rate of patients. Angiography is an interventional procedure that requires the injection of a contrast agent into the blood vessels of the subject, because X-rays cannot penetrate the contrast agent, angiography accurately reflects the location and extent of vascular lesions. However, angiography has many disadvantages in practical clinical applications. For example, it can only show the lumen status, it cannot show the wall of the vessel where the lesion is located and the atheroma, it cannot provide details of the atheroma morphology and nature, and it can potentially underestimate the extent of coronary stenosis for the physician. In order to detect the conditions inside blood vessels, new technologies such as intravascular ultrasound are invented. The intravascular ultrasound is to guide a miniature ultrasonic probe into a blood vessel through a catheter for detection, and then display fine anatomical information such as geometric forms, structures and the like in the blood vessel through an electronic imaging system. The probe of the intravascular ultrasound is directly placed in a blood vessel for detection, so the technology not only can accurately measure the sizes of the blood vessel, the atheromatous plaque and the fibrous plaque, but also can provide general tissue information of the atheromatous plaque and the fibrous plaque, and is obviously superior to radiography when displaying the deformation state of the intravascular complex disease caused by cardiovascular diseases or interventional therapy and the like.
Although the intravascular ultrasound technique can detect the internal morphology of a blood vessel, as well as angiography, the intravascular ultrasound technique belongs to interventional detection, and a probe is inserted into the blood vessel under local anesthesia, so that a plurality of blood vessel detection blind areas exist and adverse side effects on a person to be detected can be caused. Therefore, the non-invasive blood vessel health monitoring technology has huge requirements and market prospects.
Photoacoustic Imaging (PAI) is a new non-invasive and non-ionizing biomedical Imaging method developed in recent years, which can avoid the problems of invasive detection methods such as intravascular ultrasound. The principle is that when pulse laser is irradiated into biological tissue, the light absorption domain of the tissue will generate ultrasonic signals, and the ultrasonic signals generated by light excitation are photoacoustic signals. The photoacoustic signal generated by the biological tissue carries the light absorption characteristic information of the tissue, and the light absorption distribution image in the tissue can be reconstructed by detecting the photoacoustic signal. The photoacoustic imaging technology can realize the detection of the blood vessel distribution, namely the detection of the external appearance, but the detection of the external appearance and the internal tissue shape distribution of the blood vessel is a difficult problem to overcome. In addition, the molecular composition of an atheroma or other growth on the inner wall of a blood vessel needs to be detected in order to treat the disease accurately. Laser-induced Raman (Laser-induced Raman) can detect molecular components. If the two technologies are combined, more abundant information can be expected in the blood vessel detection.
Disclosure of Invention
Aiming at the problems of simultaneous detection of the external appearance and the internal tissue shape distribution of a blood vessel and the requirements of detection of components of increased biomolecules such as atheromatous plaques and the like proliferated on the inner wall of the blood vessel by the photoacoustic technology, the invention provides a system and a method for combined detection of laser photoacoustic and laser-induced Raman. In laser optoacoustic, a technology based on coaxial time domain resolution optoacoustic imaging is adopted, namely laser emission and ultrasonic receiving are coaxial light paths, optoacoustic echo of blood flow in a blood vessel is taken as a spatial analysis reference, and optoacoustic echo signals corresponding to layered substances of the blood flow, the internal tissue of the blood vessel and the vascular wall which pass through a main shaft path at the same moment can be analyzed at a single scanning point through analysis of time domain resolution optoacoustic echo signals, so that the optoacoustic can simultaneously detect the external appearance and the internal tissue shape distribution of the blood vessel; after the position and the thickness of the augmented organism on the inner wall of the blood vessel are determined by laser optoacoustic, the composition of the augmented organism molecules distributed at different positions along the section is obtained by adopting fine scanning laser Raman detection.
The invention is realized by the following steps:
the invention provides a human blood vessel detection system based on laser photoacoustic spectroscopy, which mainly comprises a main controller, a scanning head, a three-dimensional electric platform and auxiliary components, wherein the scanning head is arranged on the main controller;
the auxiliary components comprise a fiber Raman spectrometer, a cascade amplifier, a detector circuit, a laser controller, a signal acquisition card, a three-way motor controller and a three-way stepping motor;
a Raman receiving assembly, a photoacoustic detection head, a perforated reflector, a laser beam expander, a proportional beam splitter, a photoelectric detector, an ultrasonic probe, a laser cable, a detector cable and an ultrasonic cable are arranged in the scanning head; the Raman receiving assembly consists of a double-color chip, an optical fiber coupling mirror, a Rayleigh filter and an optical fiber; the scanning head is provided with a window, so that a laser cable, a detector cable, an optical fiber and an ultrasonic cable can conveniently penetrate out of the scanning head and are respectively connected with a laser controller, a detector circuit, an optical fiber Raman spectrometer and a cascade amplifier; the photoacoustic probe consists of a plano-convex focusing lens and an ultrasonic lens which are coaxially assembled, the central axes of the plano-convex focusing lens and the ultrasonic lens are both main axes, the plano-convex focusing lens is provided with a central circular hole, the ultrasonic lens is coaxially embedded and assembled into the central circular hole, and the optical focus of the plano-convex focusing lens and the acoustic focus of the ultrasonic lens are coincided at a focusing point; the scanning head is assembled on the three-dimensional electric platform and is driven by the three-way stepping motor to do three-dimensional motion, and the three-way stepping motor is accurately controlled by the three-way motor controller;
the laser controller starts or closes the laser through the laser cable and can set working parameters of the laser; the photoelectric detector can convert the received light into an electric signal, the electric signal is sent to a detector circuit through a detector cable to be amplified, the amplified electric signal is used as a control signal and sent to a trigger port of the signal acquisition card, and the signal acquisition card is triggered to start signal acquisition work; the ultrasonic probe can convert the received ultrasonic into an electric signal, and the electric signal is sent to the cascade amplifier through the ultrasonic cable to be amplified in a multi-stage series connection manner, the amplified signal is sent to the signal acquisition card to be sampled, and is subjected to analog-to-digital conversion and sent to the main control software in the main controller to be analyzed;
intermediate frequency pulse laser emitted by the laser along an emission optical axis is divided into two parts of transmission pulse light and reflection pulse light after passing through the proportion light splitting sheet; the reflected pulse light travels along a monitoring optical axis, is received by a photoelectric detector and converted into an electric signal, is amplified by a detector circuit and is transmitted to a trigger port of a signal acquisition card; the transmitted pulse light continues to advance along the emission optical axis, is expanded by the laser beam expander, is collimated, penetrates through the bicolor sheet, is reflected by the perforated reflector, advances downwards along the main shaft, and is focused on a focusing point by the plano-convex focusing mirror; simultaneously exciting an ultrasonic signal and a Raman signal at a focusing point, enabling the excited ultrasonic signal to travel upwards along a main shaft, passing through a through hole of a reflector with a hole through an ultrasonic lens in a central round hole, focusing the ultrasonic signal onto an ultrasonic probe, converting the ultrasonic into an electric signal by the ultrasonic probe, and amplifying the electric signal in multiple stages by a cascade amplifier to a signal acquisition card; the excited Raman signal travels upwards along the main shaft, passes through the plano-convex focusing mirror, is reflected by the perforated reflecting mirror, travels from right to left along the emission optical axis, is reflected by the dichromatic plate, then is converted to the Raman optical axis to travel, passes through the Rayleigh filter by the optical fiber coupling mirror to be focused on the end surface of the optical fiber, then enters the optical fiber Raman spectrometer through the optical fiber to be subjected to light splitting and photoelectric conversion to obtain a Raman spectrum signal, and then is transmitted to main control software in the main controller to be analyzed; the main controller is used for starting the laser controller, receiving the signal output by the signal acquisition card and the Raman signal output by the fiber Raman spectrometer, and analyzing the signals by internal main control software; the main controller is used for sending a control command and the number of the three-way stepping motor required to move in three directions to the three-way motor controller; the main controller is also used for setting the exposure time of the Raman test for the optical fiber Raman spectrometer;
the emission optical axis, the monitoring optical axis, the main axis and the Raman optical axis are coplanar, the emission optical axis is parallel to the main axis, the monitoring optical axis is parallel to the Raman optical axis, and the emission optical axis is perpendicular to the monitoring optical axis; the invention provides a human body blood vessel detection method based on laser photoacoustic spectroscopy, which comprises the following steps:
(1) initial positioning of system
The human body area to be detected comprises different tissues and components such as skin, subcutaneous tissues, blood vessel walls, atheromatous plaques, flowing blood and the like, and a human body blood vessel detection system is close to the initial blood flow position of the blood vessel to be detected in the human body area to be detected; the main controller sends a control instruction to the three-way motor controller, sets the advancing step number of the three-way stepping motor in the z direction (the subcutaneous depth direction is the z direction, the direction along the blood flow is the x direction, and the direction perpendicular to the blood flow is the y direction), and drives the scanning head on the three-dimensional electric platform to move, so that the photoacoustic of the probe is approximately positioned above the skin by about one centimeter; the main controller starts a laser controller, and the laser controller starts a laser according to set working parameters;
(2) single point testing
Part of energy of laser pulse penetrates through the proportional beam splitter and the bicolor plate, is reflected by the perforated reflector, and is focused on a focusing point by the plano-convex focusing mirror to form an excitation solid angle taking the focusing point as a vertex, the excitation solid angle penetrates through different tissues at different depths under the skin, and only those tissues with unit area energy density exceeding the photoacoustic generation threshold can generate ultrasonic echo signals; ultrasonic echo signals positioned in a receiving solid angle taking a focusing point as a vertex are focused to an ultrasonic probe through an ultrasonic lens and converted into electric signals; meanwhile, the other part of energy of the laser pulse is reflected by the proportional beam splitter, is received by the photoelectric detector and converted into an electric signal, is amplified by the detector circuit and is transmitted to a trigger port of the signal acquisition card, the signal acquisition card is instantly started, at the moment, the electric signal output by the ultrasonic probe is amplified in multiple stages by the cascade amplifier and then is transmitted to the signal acquisition card for high-frequency sampling, analog-to-digital conversion and is transmitted to main control software in the main controller for analysis;
(3) time domain resolved photoacoustic localization analysis
Under the condition of good focusing, the laser energy of unit area of the above four different components reaches a photoacoustic threshold value, and a subcutaneous tissue photoacoustic signal, a blood vessel wall photoacoustic signal, an atheromatous plaque photoacoustic signal and a flowing blood photoacoustic signal are sequentially excited; in the time domain resolution photoacoustic signal received by the main control software in the main controller, firstly at t1The time of day receiving intensity is I1A time width of T1Then sequentially at t2The time of day receiving intensity is I2A time width of T2Photoacoustic signal of vessel wall of (t)3The time of day receiving intensity is I3A time width of T3Atheromatous photoacoustic signal of, t4The time of day receiving intensity is I4A time width of T4The flowing blood photoacoustic signal of (a);
the reciprocal of the time width of the photoacoustic signal is approximately 2 times of the ultrasonic frequency, the ultrasonic frequencies of different tissue components excited by laser are different, and the ultrasonic frequencies of the same tissue components excited by laser are the same, so that the tissue components can be judged according to the measurement of the time width; the strength of the photoacoustic signal represents the size of the density of the tissue components, and the stronger the photoacoustic signal is, the higher the density of the tissue at the position is;
defining a transmission time at1＝t2-t1；Δt2＝t3-t2；Δt3＝t4-t3(ii) a Multiplying the transmission speed of sound in the tissue component by the transmission time to obtain the thickness of the tissue component;
(4) photoacoustic single point blood vessel measurement
Recording the x coordinate of the focusing point at the moment by main control software in the main controller; main controlThe device sends a control command to the three-way motor controller, the three-way stepping motor drives the scanning head on the three-dimensional electric platform to move and scan along the z axis and the y axis, and meanwhile, the steps (2) and (3) are repeated; continuously analyzing by main control software in the main controller until the highest value is reached, recording y and z coordinates of a focusing point which is the highest point of the blood concentration at the moment, and thus obtaining a three-dimensional coordinate of the highest point of the blood concentration; by Δ t3Multiplying by sound velocity to obtain the thickness of atheromatous plaque passing by the main shaft at the focusing point according to I3Recording the density of atheromatous plaque by Δ t2Multiplying by the speed of sound to obtain the thickness of the vessel wall through which the principal axis passes at the focus, according to I2Recording the density of the vessel wall;
(5) cross-sectional atheromatous component analysis
The main controller sets the exposure time of the Raman test for the optical fiber Raman spectrometer; sending a control instruction to the three-way motor controller by main control software in the main controller according to the thickness of the atheromatous plaque calculated in the step (4), enabling the three-way stepping motor to drive the scanning head on the three-dimensional electric platform to move upwards along the z-axis continuously in a minimum step length, and enabling the total moving distance to be equal to the thickness of the atheromatous plaque; every time the minimum step length is moved, the Raman detection is carried out according to the following method:
part of energy of the laser pulse penetrates through the proportional beam splitter and the bicolor plate, is reflected by the perforated reflector, and is focused on a focusing point by the plano-convex focusing mirror, so that atheromatous plaque at the focusing point is excited to generate a Raman signal, and the Raman signal reflects the molecular composition of the atheromatous plaque at the focusing point; the excited Raman signal travels upwards along the main shaft, passes through the plano-convex focusing mirror, is reflected by the perforated reflecting mirror and the dichroic plate, passes through the Rayleigh filter (the Rayleigh filter filters Raman pump laser) by the optical fiber coupling mirror and is focused on the end face of the optical fiber, then enters the optical fiber Raman spectrometer through the optical fiber for light splitting and photoelectric conversion to obtain a Raman spectrum signal, and then is transmitted to main control software in the main controller to analyze the molecular composition of atheromatous plaques at the focusing point;
and after finishing Raman detection, moving a minimum step length again, and repeating continuously until the total moving distance is equal to the thickness of the atheromatous plaque: after the component analysis of the whole section atheromatous plaque is completed, according to the three-dimensional coordinate of the highest point of the blood concentration recorded in the step (4), the main control software in the main controller sends a control command to the three-way motor controller, so that the three-way stepping motor drives the scanning head on the three-dimensional electric platform to move downwards along the z-axis until the focusing point returns to the highest point of the blood concentration again;
(6) photoacoustic three-dimensional vascular reconstruction
The main controller sends a control instruction to the three-way motor controller, the three-way stepping motor drives the scanning head on the three-dimensional electric platform to step by one step length along the x axis, and the steps (4) and (5) are repeated to obtain the coordinate of the blood center point of the second point, the thickness and the density of the corresponding atheromatous plaque under the coordinate, the thickness and the density of the blood vessel wall and the component distribution of the section atheromatous plaque; then, the scanning head is stepped by one step length along the x axis to obtain the blood center point coordinate of the third point, the thickness and the density of the corresponding atheromatous plaque under the coordinate, the thickness and the density of the blood vessel wall and the distribution of the components of the section atheromatous plaque; similarly, continuously completing the coordinates of the blood center points of the fourth point, the fifth point, … and the Nth point, and the thickness and density of the corresponding atheroma, the thickness and density of the blood vessel wall and the distribution of the components of the sectional atheroma under the coordinates; and summarizing the information of all the measuring points until the blood vessel three-dimensional measurement in the whole human body region to be measured is completed, and then reconstructing the three-dimensional appearance (including coordinates, tissues, thickness, density and component distribution) of the blood vessel in the human body region to be measured.
The invention has the advantages that the volume and the cost of the system are reduced by multiplexing the laser optoacoustic and the laser Raman light source and part of the light path; by taking photoacoustic echoes of blood flow in a blood vessel as a spatial analysis reference and adopting time domain resolution photoacoustic echo signal analysis, photoacoustic echo signals corresponding to layered substances of the blood flow, the internal tissue of the blood vessel and the vascular wall passing through a main shaft path at the same moment can be analyzed, and the simultaneous detection of the external appearance and the internal tissue shape distribution of the blood vessel by photoacoustic can be realized; the photoacoustic and laser Raman are combined, and the molecular components of layered substances of the vascular wall can be detected.
Drawings
Fig. 1 is a schematic diagram of the system and operation of the present invention (including a photoacoustic signal), in which: 1-scanning head; 2-laser; 3-emission optical axis; 4-monitoring the optical axis; 5-photodetector; 6-laser cable; 7-laser beam expander; 8-detector cable; 9-plano-convex focusing lens; 10-photoacoustic probe head; 11-ultrasonic lens; 12-a mirror with a hole; 13-ultrasonic probe; 14-ultrasonic cable; 15-window; 16-main shaft; 17-cascade amplifier; 18-detector circuit; 19-laser controller; 20-signal acquisition card; 21-main controller; 22-three-dimensional motorized platform; 23-three-way motor controller; 24-a receiving solid angle; 25-excitation solid angle; 26-subcutaneous tissue; 27-the vessel wall; 28-atheroma; 29-flowing blood; 30-focus point; 31-proportional beam splitter; 32-subcutaneous tissue photoacoustic signal; 33-vessel wall photoacoustic signal; 34 — atheroma photoacoustic signal; 35-flow blood photoacoustic signal; 36-through hole; 37-three-way stepping motor; 38-central circular hole; 39-area to be measured of human body; 40-skin; 41-fiber Raman spectrometer; 42-two color chips; 43-fiber coupled mirror; 44-Rayleigh filter; 45-Raman optical axis; 46-optical fiber.
Detailed Description
The specific embodiment of the present invention is shown in fig. 1.
The invention provides a human blood vessel detection system based on laser photoacoustic spectroscopy, which mainly comprises a main controller 21, a scanning head 1, a three-dimensional electric platform 22 and auxiliary components;
the auxiliary components comprise a fiber Raman spectrometer 41, a cascade amplifier 17, a detector circuit 18, a laser controller 19, a signal acquisition card 20, a three-way motor controller 23 and a three-way stepping motor 37;
a Raman receiving component, a photoacoustic probe 10, a perforated reflector 12, a laser 2, a laser beam expander 7, a proportional beam splitter 31, a photoelectric detector 5, an ultrasonic probe 13, a laser cable 6, a detector cable 8 and an ultrasonic cable 14 are arranged in the scanning head 1; the Raman receiving component consists of a double-color chip 42, an optical fiber coupling mirror 43, a Rayleigh filter 44 and an optical fiber 46; a window 15 is formed on the scanning head part 1, so that the laser cable 6, the detector cable 8, the optical fiber 46 and the ultrasonic cable 14 can conveniently penetrate out of the scanning head part 1 and are respectively connected with the laser controller 19, the detector circuit 18, the optical fiber Raman spectrometer 41 and the cascade amplifier 17; the photoacoustic probe 10 consists of a plano-convex focusing mirror 9 and an ultrasonic lens 11 which are coaxially assembled, the central axes of the two are both a main shaft 16, the plano-convex focusing mirror 9 is provided with a central circular hole 38, the ultrasonic lens 11 is coaxially embedded and assembled into the central circular hole 38, and the optical focus of the plano-convex focusing mirror 9 and the acoustic focus of the ultrasonic lens 11 are superposed on a focusing point 30; the scanning head part 1 is assembled on a three-dimensional electric platform 22 and is driven by a three-way stepping motor 37 to do three-dimensional motion, and the three-way stepping motor 37 is accurately controlled by a three-way motor controller 23;
the laser controller 19 starts or shuts off the laser 2 through the laser cable 6, and can set working parameters of the laser 2; the photoelectric detector 5 can convert the received light into an electric signal, the electric signal is sent to the detector circuit 18 through the detector cable 8 to be amplified, the amplified electric signal is used as a control signal and sent to a trigger port of the signal acquisition card 20, and the signal acquisition card 20 is triggered and started to carry out signal acquisition work; the ultrasonic probe 13 can convert the received ultrasonic into an electric signal, and the electric signal is sent to the cascade amplifier 17 through the ultrasonic cable 14 for multistage series amplification, the amplified signal is sent to the signal acquisition card 20 for signal sampling, and the signal is subjected to analog-to-digital conversion and sent to the main control software in the main controller 21 for analysis;
the intermediate frequency pulse laser emitted by the laser 2 along the emission optical axis 3 is divided into two parts of transmission pulse light and reflection pulse light after passing through the proportional beam splitter 31 (in this embodiment, nine beam splitters, i.e. the ratio of transmission light to reflection light is nine to one); the reflected pulse light advances along the monitoring optical axis 4, is received by the photoelectric detector 5 and converted into an electric signal, is amplified by the detector circuit 18 and is transmitted to a trigger port of the signal acquisition card 20; the transmitted pulse light continues to travel along the emission optical axis 3, is expanded and collimated by the laser beam expander 7, penetrates through the bicolor sheet 42, is reflected by the perforated reflector 12, travels downwards along the main shaft 16, and is focused on a focusing point 30 by the plano-convex focusing mirror 9; an ultrasonic signal and a Raman signal are simultaneously excited at a focusing point 30, the excited ultrasonic signal travels upwards along a main shaft 16, passes through a through hole 36 of a reflector 12 with a hole through an ultrasonic lens 11 in a central round hole 38 and is focused on an ultrasonic probe 13, the ultrasonic probe 13 converts the ultrasonic into an electric signal, and the electric signal is subjected to multistage amplification by a cascade amplifier 17 and then is transmitted to a signal acquisition card 20; the excited raman signal travels upwards along the main shaft 16, passes through the plano-convex focusing mirror 9, is reflected by the perforated reflecting mirror 12, travels from right to left along the emission optical axis 3, is reflected by the dichroic plate 42, then is turned to the raman optical axis 45 to travel, passes through the rayleigh filter 44 by the optical fiber coupling mirror 43 to be focused on the end surface of the optical fiber 46, then enters the optical fiber raman spectrometer 41 through the optical fiber 46 to be subjected to light splitting and photoelectric conversion to obtain a raman spectrum signal, and then is transmitted to main control software in the main controller 21 to be analyzed;
the main controller 21 is used for starting the laser controller 19, receiving the signal output by the signal acquisition card 20 and the raman signal output by the fiber raman spectrometer 41, and analyzing by internal main control software; the main controller 21 is configured to send a control command and the number of steps required to move the three-way stepping motor 37 to the three-way motor controller 23; the main controller 21 is further configured to set an exposure time of the raman test for the fiber raman spectrometer 41;
the emission optical axis 3, the monitoring optical axis 4, the main axis 16 and the Raman optical axis 45 are coplanar, the emission optical axis 3 is parallel to the main axis 16, the monitoring optical axis 4 is parallel to the Raman optical axis 45, and the emission optical axis 3 is perpendicular to the monitoring optical axis 4;
the invention provides a human body blood vessel detection method based on laser photoacoustic spectroscopy, which comprises the following steps:
(1) initial positioning of system
The human body area to be detected 39 comprises different tissues and components such as skin 40, subcutaneous tissue 26, blood vessel wall 27, atheromatous plaque 28, flowing blood 29 and the like, and the human body blood vessel detection system is close to the initial blood flow position of the blood vessel to be detected of the human body area to be detected 39; the main controller 21 sends a control instruction to the three-way motor controller 23, sets the number of steps in the z direction of the three-way stepping motor 37 (in this embodiment, the subcutaneous depth direction is the z direction, the direction along the blood flow is the x direction, and the direction perpendicular to the blood flow is the y direction), and drives the scanning head 1 on the three-dimensional electric platform 22 to move, so that the photoacoustic probe 10 is approximately located about one centimeter above the skin 10 (the focal length of the planoconvex focusing mirror 9 in this embodiment is 3 centimeters); the main controller 21 starts the laser controller 19, and the laser controller 19 starts the laser 2 according to the set working parameters (in this embodiment, the laser repetition frequency is 1kHz, the laser pulse width is 10ns, the wavelength is 785nm, and the single pulse energy is 30 microjoules);
(2) single point testing
Part of energy of the laser pulse penetrates through the proportional beam splitter 31 and the bicolor 42, is reflected by the reflector 12 with holes, and is focused on the focusing point 30 by the plano-convex focusing mirror 9 to form an excitation solid angle 25 taking the focusing point 30 as a vertex, the excitation solid angle 25 penetrates through different tissues at different depths under the skin 40, and only those tissues with energy density of unit area exceeding the photoacoustic generation threshold can generate ultrasonic echo signals; ultrasonic echo signals of a receiving solid angle 24 with a focusing point 30 as a vertex are focused to an ultrasonic probe 13 through an ultrasonic lens 11 and converted into electric signals; meanwhile, another part of the energy of the laser pulse is reflected by the proportional beam splitter 31, is received by the photodetector 5 and is converted into an electrical signal, is amplified by the detector circuit 18, and is sent to a trigger port of the signal acquisition card 20, the signal acquisition card 20 is instantly started, at this time, the electrical signal output by the ultrasonic probe 13 is subjected to multistage amplification by the cascade amplifier 17, is sent to the signal acquisition card 20 for high-frequency sampling (the sampling frequency is 40MHz in the embodiment), is subjected to analog-to-digital conversion (the sampling frequency is 12bit analog-to-digital conversion in the embodiment), and is sent to main control software in the main controller 21 for analysis;
(3) time domain resolved photoacoustic localization analysis
Normally, the laser pulse energy in the excitation solid angle 25 passes through the subcutaneous tissue 26, the blood vessel wall 27, the atheroma 28 and the flowing blood 29 in sequence, and when the focusing is good, the laser energy of the unit area of the above four different components reaches the photoacoustic threshold, and the subcutaneous tissue photoacoustic signal 32, the blood vessel wall photoacoustic signal 33, the atheroma photoacoustic signal 34 and the flowing blood photoacoustic signal 35 are excited in sequence; in the time domain resolved photoacoustic signal received by the master software in the master controller 21 (see the photoacoustic signal diagram in fig. 1), first at t1Time of dayReceived strength of I1A time width of T1Then sequentially at t2The time of day receiving intensity is I2A time width of T2Vascular wall photoacoustic signal 33, t3The time of day receiving intensity is I3A time width of T3Of the atheromatous photoacoustic signal 34, t4The time of day receiving intensity is I4A time width of T4The flowing blood photoacoustic signal 35;
the reciprocal of the time width of the photoacoustic signal is approximately 2 times of the ultrasonic frequency, the ultrasonic frequencies of different tissue components excited by laser are different, and the ultrasonic frequencies of the same tissue components excited by laser are the same, so that the tissue components can be judged according to the measurement of the time width; the strength of the photoacoustic signal represents the size of the density of the tissue components, and the stronger the photoacoustic signal is, the higher the density of the tissue at the position is;
defining a transmission time at1＝t2-t1；Δt2＝t3-t2；Δt3＝t4-t3(ii) a Multiplying the transmission speed of sound in the tissue component by the transmission time to obtain the thickness of the tissue component;
(4) photoacoustic single point blood vessel measurement
The main control software in the main controller 21 records the x coordinate of the focusing point 30 at this time; the main controller 21 sends a control command to the three-way motor controller 23, the three-way stepping motor 37 drives the scanning head 1 on the three-dimensional electric platform 22 to move and scan along the z axis and the y axis, and meanwhile, the steps (2) and (3) are repeated; continuously analyzing by main control software in the main controller 21 until the highest value is reached, at the moment, the focus point 30 is the highest point of the blood concentration, and recording y and z coordinates of the focus point 30 so as to obtain a three-dimensional coordinate of the highest point of the blood concentration; by Δ t3Multiplying by the speed of sound to obtain the thickness of atheroma 28 through which the principal axis 16 passes at the focal point 30, according to I3Recording the density of atheromatous plaque 28 by Δ t2Multiplying by the speed of sound yields the thickness of the vessel wall 27 through which the principal axis 16 passes at the focal point 30, according to I2Recording the density of the vessel wall 27;
(5) cross-sectional atheromatous component analysis
The main controller 21 sets the exposure time (2 seconds in this embodiment) of the raman test to the fiber raman spectrometer 41; sending a control instruction to the three-way motor controller 23 by the main control software in the main controller 21 according to the thickness of the atheromatous plaque 28 calculated in the step (4), so that the three-way stepping motor 37 drives the scanning head 1 on the three-dimensional electric platform 22 to continuously move along the z-axis in the minimum step length, and the total moving distance is equal to the thickness of the atheromatous plaque 28; every time the minimum step length is moved, the Raman detection is carried out according to the following method:
part of energy of the laser pulse penetrates through the proportional beam splitter 31 and the bicolor 42, is reflected by the reflecting mirror 12 with holes, and is focused on the focusing point 30 through the plano-convex focusing mirror 9, so that the atheromatous plaque 28 at the focusing point 30 is excited to generate a Raman signal, and the Raman signal reflects the molecular composition of the atheromatous plaque 28 at the focusing point 30; the excited raman signal travels upwards along the main shaft 16, passes through the plano-convex focusing mirror 9, is reflected by the perforated reflecting mirror 12 and the dichroic plate 42, passes through the rayleigh filter 44 (i.e. the rayleigh filter 44 filters the raman pump laser) by the optical fiber coupling mirror 43, is focused on the end surface of the optical fiber 46, enters the optical fiber raman spectrometer 41 through the optical fiber 46 for light splitting and photoelectric conversion to obtain a raman spectrum signal, and then is transmitted to the main control software in the main controller 21 to analyze the molecular composition of the atheromatous plaque 28 at the focusing point 30;
after completion of the raman probe, a minimum step is moved again and again until the total distance moved equals the thickness of the atheromatous plaque 28: after the component analysis of the whole section atheromatous plaque 28 is completed, according to the three-dimensional coordinate of the highest blood concentration point recorded in the step (4), the main control software in the main controller 21 sends a control instruction to the three-way motor controller 23, so that the three-way stepping motor 37 drives the scanning head 1 on the three-dimensional electric platform 22 to move downwards along the z-axis until the focusing point 30 returns to the highest blood concentration point again;
(6) the photoacoustic three-dimensional blood vessel reconstruction main controller 21 sends a control instruction to the three-way motor controller 23, the three-way stepping motor 37 drives the scanning head 1 on the three-dimensional electric platform 22 to step by one step along the x axis, and the steps (4) and (5) are repeated to obtain the blood center point coordinate of the second point, the thickness and the density of the atheromatous plaque 28 corresponding to the coordinate, the thickness and the density of the blood vessel wall 27 and the component distribution of the section atheromatous plaque 28; then, the scanning head 1 is stepped by one step along the x axis to obtain the blood center point coordinate of the third point, the thickness and the density of the corresponding atheromatous plaque 28 under the coordinate, the thickness and the density of the blood vessel wall 27 and the component distribution of the section atheromatous plaque 28; similarly, the coordinates of the blood center points of the fourth point, the fifth point, … and the nth point are continuously obtained, and the thickness and density of the corresponding atheroma 28, the thickness and density of the blood vessel wall 27 and the composition distribution of the sectional atheroma 28 are obtained under the coordinates; and summarizing the information of all the measurement points until the blood vessel three-dimensional measurement in the whole human body region to be measured 39 is completed, so that the reconstruction of the three-dimensional appearance (including coordinates, tissues, thickness, density and component distribution) of the blood vessel in the human body region to be measured 39 can be completed.
Claims (1)
1. A human blood vessel detection system based on laser photoacoustic spectroscopy comprises a main controller (21), a scanning head (1), a three-dimensional electric platform (22) and auxiliary components, wherein the auxiliary components comprise an optical fiber Raman spectrometer (41), a cascade amplifier (17), a detector circuit (18), a laser controller (19), a signal acquisition card (20), a three-way motor controller (23) and a three-way stepping motor (37); the method is characterized in that:
a Raman receiving component, a photoacoustic detection head (10), a reflector (12) with holes, a laser (2), a laser beam expander (7), a proportion beam splitter (31), a photoelectric detector (5), an ultrasonic probe (13), a laser cable (6), a detector cable (8) and an ultrasonic cable (14) are arranged in the scanning head (1); the Raman receiving assembly consists of a two-color chip (42), an optical fiber coupling mirror (43), a Rayleigh filter (44) and an optical fiber (46); a window (15) is formed in the scanning head (1), so that a laser cable (6), a detector cable (8), an optical fiber (46) and an ultrasonic cable (14) can conveniently penetrate out of the scanning head (1), and are respectively connected with a laser controller (19), a detector circuit (18), an optical fiber Raman spectrometer (41) and a cascade amplifier (17); the photoacoustic probe (10) consists of a plano-convex focusing mirror (9) and an ultrasonic lens (11) which are coaxially assembled, the central axes of the plano-convex focusing mirror and the ultrasonic lens are both a main shaft (16), the plano-convex focusing mirror (9) is provided with a central round hole (38), the ultrasonic lens (11) is coaxially embedded and assembled in the central round hole (38), and the optical focus of the plano-convex focusing mirror (9) and the acoustic focus of the ultrasonic lens (11) are superposed on a focusing point (30); the scanning head (1) is assembled on a three-dimensional electric platform (22) and is driven by a three-way stepping motor (37) to do three-dimensional motion, and the three-way stepping motor (37) is accurately controlled by a three-way motor controller (23);
the laser controller (19) starts or shuts off the laser (2) through the laser cable (6) and can set working parameters of the laser (2); the photoelectric detector (5) can convert the received light into an electric signal, the electric signal is sent to the detector circuit (18) through the detector cable (8) to be amplified, the amplified electric signal is used as a control signal and sent to a trigger port of the signal acquisition card (20), and the signal acquisition card (20) is triggered and started to carry out signal acquisition work; the ultrasonic probe (13) can convert the received ultrasonic into an electric signal, the electric signal is sent to the cascade amplifier (17) through the ultrasonic cable (14) for multistage series amplification, the amplified signal is sent to the signal acquisition card (20) for signal sampling, and the signal is subjected to analog-to-digital conversion and sent to the main control software in the main controller (21) for analysis;
intermediate-frequency pulse laser emitted by the laser (2) along the emission optical axis (3) is divided into two parts of transmission pulse light and reflection pulse light after passing through the proportion light splitting sheet (31); the reflected pulse light advances along a monitoring optical axis (4), is received by a photoelectric detector (5) and is converted into an electric signal, is amplified by a detector circuit (18), and is sent to a trigger port of a signal acquisition card (20); the transmitted pulse light continues to travel along the emission optical axis (3), is expanded by the laser beam expander (7), is collimated, penetrates through the bicolor patch (42), is reflected by the reflector (12) with holes, travels downwards along the main shaft (16), and is focused on a focusing point (30) by the plano-convex focusing mirror (9); an ultrasonic signal and a Raman signal are simultaneously excited at a focusing point (30), the excited ultrasonic signal travels upwards along a main shaft (16), passes through a through hole (36) of a reflector (12) with a hole through an ultrasonic lens (11) in a central circular hole (38) and is focused on an ultrasonic probe (13), the ultrasonic probe (13) converts the ultrasonic into an electric signal, and the electric signal is amplified in a cascade amplifier (17) in a multi-stage series mode and then is transmitted to a signal acquisition card (20); the excited Raman signal travels upwards along a main shaft (16), passes through a plano-convex focusing mirror (9), is reflected by a perforated reflecting mirror (12), travels from right to left along an emission optical axis (3), is reflected by a dichromatic patch (42), then is transferred to a Raman optical axis (45) to travel, passes through a fiber coupling mirror (43), is focused on the end surface of an optical fiber (46) through a Rayleigh filter (44), then enters a fiber Raman spectrometer (41) through the optical fiber (46) for light splitting and photoelectric conversion to obtain a Raman spectrum signal, and then is transmitted to main control software in a main controller (21) for analysis;
the main controller (21) is used for starting the laser controller (19), receiving the signal output by the signal acquisition card (20) and the Raman signal output by the fiber Raman spectrometer (41), and analyzing by internal main control software; the main controller (21) is used for sending a control command and the number of the three-way stepping motor (37) required three-way traveling steps to the three-way motor controller (23); the main controller (21) is also used for setting the exposure time of the Raman test for the fiber Raman spectrometer (41);
the emission optical axis (3), the monitoring optical axis (4), the main shaft (16) and the Raman optical axis (45) are coplanar, the emission optical axis (3) is parallel to the main shaft (16), the monitoring optical axis (4) is parallel to the Raman optical axis (45), and the emission optical axis (3) is perpendicular to the monitoring optical axis (4).
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