192 results about "Particle imaging" patented technology

The invention belongs to the technical field of magnetic particle imaging, relates to a magnetic particle imaging reconstruction method based on a calibration magnetic field generation system matrix, and aims to solve the problems that a traditional magnetic particle imaging reconstruction method is poor in applicability in asymmetric bilateral structure magnetic particle imaging equipment (A-MPI) and cannot perform imaging in any region. The method comprises the following steps: performing grid division on an imaging area, calibrating magnetic field intensity, and obtaining magnetic field gradient distribution of each point; obtaining a theoretical system matrix according to a mathematical calculation mode; randomly moving the positions of the non-magnetic field points for scanning to obtain actually measured magnetic field gradient distribution and a system matrix, and constructing a data set; expanding the data set based on the simulation system; constructing a deep learning model, and inputting the extended data set and the measured data into the training deep learning model; and inputting a theoretical system matrix at any position, and obtaining an accurate system matrix by using the trained model. According to the invention, the system matrix at any position can be obtained under the A-MPI equipment, so that imaging at any position is realized.

Provided in the present invention are an imaging device and method for turbid oil abrasive particles based on polarized image enhancement, which belong to the technical field of image processing. The imaging device of the present invention includes a CMOS fixing device, a Stokes polarized CMOS sensor, an optical lens sleeve and an optical magnifying glass, where the Stokes polarized CMOS sensor includes a CMOS sensor and a Stokes analyzer. By using a polarization characteristic difference between scattered light of lubricating oil media and reflected light of abrasive particles, Stokes vector information is measured in real time under turbid lubricating oil scenes, the scattered light of the media is filtered out, image quality of the abrasive particles is improved, coverage duration for monitoring abrasive particle imaging is effectively prolonged.

The invention provides a magnetic particle imaging resolution improving method and system based on frequency domain information filtering, and relates to the technical field of magnetic particle imaging. Comprising the following steps: inputting original magnetic particle imaging data into a Transform model, and selectively filtering frequency domain information in the magnetic particle imaging data through a fusion frequency domain discrimination feedforward network module in an encoder to obtain the output of the encoder; inputting the output of the encoder into a bottleneck layer, aggregating global and local information through a multi-scale attention mechanism module, and then selectively filtering frequency domain information in the magnetic particle imaging data again to obtain the output of the bottleneck layer; inputting the output of the bottleneck layer into a decoder with the same structure as the bottleneck layer to obtain deep features; inputting the deep features into a convolutional layer to obtain a residual image; and calculating the sum of the original magnetic particle imaging data and the residual image to obtain a reconstructed image. According to the invention, the overall imaging resolution of the MPI image under the low-gradient field acquisition condition is improved.

The invention belongs to the field of magnetic particle imaging, particularly relates to a magnetic particle high-resolution reconstruction method based on fast feature fusion, and aims to solve the problems that an existing magnetic particle reconstruction method is slow in system matrix calibration, low in reconstructed magnetic particle image resolution, limited in signal-to-noise ratio and the like. The method comprises the following steps: collecting a system matrix generated by using a standard particle sample as a low-resolution system matrix; acquiring a voltage signal of the to-be-imaged phantom; inputting the low-resolution system matrix into the trained fast feature fusion Transform model to obtain a high-resolution system matrix; and based on the voltage signal, reconstructing the high-resolution system matrix to obtain a high-resolution MPI image. According to the method, the resolution of the MPI image is improved by carrying out rapid super-division on the system matrix, tedious and time-consuming calibration in system matrix reconstruction is avoided, in addition, resolution and signal-to-noise ratio improvement can be carried out on any system matrix, and a scanning mode related to the system matrix is not needed.

The invention belongs to the technical field of magnetic particle imaging, particularly relates to a magnetic particle imaging system and method based on a flexible receiving coil array, and aims to solve the problems that an existing rigid receiving coil is poor in biological surface adaptability and low in signal-to-noise ratio for micro geometric texture imaging. According to the structure, a receiving coil array adheres to the surface of an object to be measured, the receiving coil array and a compensation coil array are distributed on the two sides of a flexible substrate, the receiving coil array is used for receiving magnetic nanoparticle signals, and the partitioned small compensation coil array is used for conducting feed-through interference and electromagnetic interference compensation on a receiving coil; the reconstruction method comprises the following steps: sequentially carrying out Fourier transform on the collected receiving signals, extracting in-phase third harmonics and superposing to obtain processed signals, interpolating to construct a sinogram for Cartesian coordinate distribution, and reconstructing the three-dimensional particle concentration distribution of a measured object by a filtering back projection method. A flexible receiving coil array strategy is adopted, an adaptive reconstruction method is provided, and the imaging signal-to-noise ratio is improved.

The invention discloses a cloud and mist particle acquisition probe based on interference particle imaging, and the probe comprises a sheet-shaped laser emission unit which is used for emitting sheet-shaped pulse laser beams, expanding the laser beams, adjusting the incident position and the incident angle, and irradiating cloud and mist particles to generate scattered light signals; the scattered light signal acquisition unit is used for collecting scattered light signals and recording the scattered light signals on the camera; the mechanical unit comprises a first measuring arm used for installing the sheet-shaped laser unit and a second measuring arm used for installing the scattered light signal acquisition unit, and the first measuring arm and the second measuring arm are connected through a connecting section and are installed on the base; and the signal processing system is used for processing the scattered light interference signal recorded by the camera to obtain cloud and mist particle parameters. The acquisition probe provided by the invention ensures stable operation of a photoelectric system in a low-temperature complex and severe cloud environment, improves the accuracy of interference particle imaging measurement, and realizes real-time measurement of cloud particle parameters suitable for different industrial scenes.

The invention belongs to the technical field of magnetic nanoparticle imaging, particularly relates to an MPI magnetic particle imaging method and system for early detection of an AD patient, and aims to complete MPI time sequence imaging by using a diffusion model and solve the problem that the feature dimension of an input signal in the diffusion model is not matched with the resolution of an expected generated image. The method comprises the following steps: constructing a generative network model, and performing staged training; mPI time sequence one-dimensional signals are collected, and image reconstruction is carried out based on the generative network model to obtain MPI time sequence images; carrying out registration and dividing a brain region; and constructing a functional connection diagram and a functional connection matrix by using the RV coefficient, and drawing the brain network. According to the method, by constructing the Seq-VAE / Regression / Sig-LDM step-by-step network and performing staged training, free input of a signal sequence of a fixed feature dimension is realized, the image sequence reconstruction effect is improved, a default mode network is drawn based on the reconstructed image sequence, and accurate data is provided for subsequent application.

The invention discloses a multi-metal borate nano-particle as well as a preparation method and application thereof. The preparation method comprises the following steps: in the presence of small molecules with alkyl chains, performing high-temperature thermal decomposition on an organic metal compound or a metal salt compound precursor and organic borate in a solvent, and then centrifuging, modifying, performing ultrafiltration, dialyzing and purifying to obtain the multi-metal borate nanoparticles. The preparation method disclosed by the invention has the characteristics of mildness, high efficiency and strong controllability. The multi-metal borate nanoparticles prepared by the preparation method disclosed by the invention have the advantages of monodisperse size, relatively high magnetic property and good biocompatibility. Therefore, the prepared multi-metal borate nanoparticles not only have multi-modal imaging functions such as magnetic resonance imaging, near-infrared two-region imaging, nuclear medicine imaging and magnetic particle imaging, but also can be used for various treatment means such as magnetocaloric therapy and boron neutron capture therapy; potential advantages are realized in biomedical applications such as magnetic targeting tumor treatment and imaging contrast agents, and high practical values are realized.

The invention discloses a Brazilian splitting experiment device and method based on multiple heating modes, and belongs to the technical field of splitting experiments. Comprising a base, a Brazilian splitting clamp, a kettle body, a heating system, a heat transfer fluid injection hole, an axial pressure head, a temperature and pressure monitoring and heat transfer fluid outlet, a magnetic particle imaging system and a high-temperature early warning system, the temperature and pressure monitoring and heat-carrying fluid outlet is used for being connected with an external real-time observation system to conduct temperature and pressure monitoring and serves as an outlet of heat-carrying fluid at the same time. The magnetic particle imaging system is used for observing the distribution state of nano magnetic induction particles in the kettle body; the real-time high-temperature Brazilian splitting experiment can be carried out in multiple heating modes such as convection heating, conduction heating and supercritical fluid heating, the generation and expansion process of cracks in a sample can be monitored in real time, and the device is suitable for testing the strength and crack expansion of rocks under the thermal stress condition possibly encountered in actual engineering.

The invention belongs to the technical field of magnetic particle imaging, particularly relates to a stacked high-uniformity magnetic field free line magnetic particle imaging system and method, and aims to solve the problems that magnetic field free lines in an existing FFL-MPI are not uniform, imaging resolution is not uniform, and circumferential artifacts exist. The system comprises a laminated gradient coil unit composed of N groups of symmetrical coil pairs, each group comprising n layers of coils with increasing diameters, and a saddle-shaped driving scanning coil and a detection coil; through a reverse current mode of two adjacent layers of coils, the magnetic field amplitude is opposite to the current direction, the non-uniformity of the magnetic field is compensated, and a high-uniformity FFL gradient field is generated; the control system accurately collects and processes signals, the signals are fed back to the imaging unit after analog-to-digital conversion, amplification and filtering, and imaging is reconstructed through an imaging algorithm. According to the invention, the problems of non-uniform resolution and circumferential artifacts caused by non-uniform magnetic field are solved, and the imaging quality of FFL-MPI equipment is remarkably improved.

Disclosed is a nanosecond neutron analysis and associated particle imaging system (NNA / API) and gamma ray detector arrangement (arrangement) that uses associative element detection of titanium, iron and oxygen to determine concentrations of ilmenite or other minerals in extra-terrestrial bodies associated with He-3. The arrangement is used with a mobile carrier for mapping out concentrations of likely He-3 regions on the extra-terrestrial body.

The invention belongs to the technical field of magnetic particle imaging, and relates to a magnetic particle imaging method based on mixed-frequency magnetic field excitation, which comprises the following steps: acquiring a dotted magnetic nanoparticle sample and a to-be-imaged object, respectively applying a mixed-frequency excitation magnetic field in an imaging mode to the dotted magnetic nanoparticle sample and the to-be-imaged object, acquiring a mixed frequency magnetic field excitation-based system matrix and a mixed frequency domain magnetization response frequency spectrum signal; and inputting the system matrix and the mixed frequency domain magnetization response frequency spectrum signal into a concentration spatial distribution inversion model to perform concentration spatial distribution inversion of the magnetic nanoparticles, obtaining the concentration spatial distribution of the magnetic nanoparticles in the object to be imaged, and performing magnetic particle concentration distribution imaging. According to the invention, real-time high-resolution magnetic particle imaging can be realized.

The invention discloses a magnetic particle imaging signal processing link and method based on adjustable external compensation, and the link is characterized in that a signal generator is respectively connected with the input ends of a first power amplifier and a second power amplifier through a first output end and a second output end, the output end of the first power amplifier is connected with the input end of a first capacitor, and the output end of the second power amplifier is connected with the input end of a second capacitor; the output end of the first capacitor is connected with the input end of the receiving excitation module, the output end of the second power amplifier is connected with the input end of the second capacitor, the output end of the second capacitor is connected with the input end of the compensation excitation module, and the output ends of the receiving excitation module and the compensation excitation module are connected with the input end of the low-noise amplifier. The output end of the low-noise amplifier is connected with the input end of the acquisition card, the output end of the acquisition card is connected with the input end of the central processing unit, and the output end of the central processing unit is connected with the input end of the signal generator. According to the invention, the sensitivity and the imaging quality of the MPI equipment are obviously improved.

The invention discloses a directional grouting test device and a visual test method for a goaf, and the method comprises the steps: building a bed rock, laying a mineral product to be mined, laying and filling an area to be reinforced, burying a soil pressure gauge and a water pressure gauge, burying a grouting floral tube, arranging a grouting inner tube, communicating a grouting system, and setting a particle imaging velocimeter PIV. In the test process, the seepage and diffusion process in the slurry and the stress state of the rock-soil body are monitored by using a soil pressure meter and a water pressure meter; calculating the total amount of slurry flowing into the model through a slurry barrel outer scale; after grouting is finished, original-state sampling is conducted on the grouting permeation reinforcement area, a mechanical property test and a microcosmic test are conducted, and the grout permeation and reinforcement effect is analyzed; the grouting pressure-seepage distance-mechanical property relation is obtained. The goaf directional grouting permeation simulation device can carry out goaf directional grouting permeation simulation, facilitates mechanical property test of original state sampling, and has the characteristics of visualization, simulation, monitoring and the like.

The invention belongs to the technical field of magnetic particle imaging, particularly relates to a time sequence magnetic nanoparticle imaging device and method for detecting nerve response activity, and aims to solve the problems that the sensitivity of magnetic particle signal detection is not high, a large coil assembly is needed for achieving high magnetic field intensity, the calculation amount is large, and the calculation mode is complex. According to the device, a signal generator outputs a voltage signal, amplifies the voltage signal and then accesses a selection coil and a driving coil; the two selection coils are arranged in a Maxwell configuration and have the same axis; the driving coils are arranged at intervals of 90 degrees from top to bottom, from left to right and from front to back by taking the FFR as the center; the excitation coil, the receiving coil and the selection coil are coaxial; and the high-pass filter filters the signal received by the receiving coil and imports the signal into a computer through a signal acquisition card for time sequence fMPI image sequence reconstruction. According to the invention, the magnetic particle signal detection sensitivity is improved, the volume of the coil assembly is reduced, the calculation complexity and the calculation amount are simplified, and the magnetic particle imaging robustness is improved.

The invention relates to a method for evaluating and debugging a sterile pipeline for food and beverage processing, which comprises the following steps of: introducing standardized sterile gas into a closed pipeline system to establish a micro-positive pressure environment; detecting a pressure change curve of each node of the system in real time by using a micro-differential pressure sensing module; calculating the position and the size of a trace leakage point; recording the motion trail of the particles in the pipeline by using a dynamic particle imaging system PIV; flow dead angles are identified through trajectory analysis, and the potential pollution accumulation area of the retention area marks the pollution accumulation probability of each section of pipeline in a quantitative mode; preparing simulation liquid, and adding biomarker particles to enable the viscosity and the fluidity of the target beverage to be close to those of the target beverage; according to the identified potential pollution accumulation area, local directional pouring is carried out; full-process automatic data acquisition, model judgment and debugging instruction issuing can be realized, manual intervention is greatly reduced, the system stability is improved, and the system is suitable for various food and beverage production scenes.

This invention discloses a particle morphology recognition method based on YOLOv7 and interferometric imaging technology. The method uses an interferometric particle imaging system to obtain interferometric defocused images of a mixed particle field to create a dataset. The annotated interferometric defocused images are divided into training, validation, and test sets. The network is then improved by incorporating a collaborative attention module to enhance detection accuracy. Hyperparameters are adjusted, and training and testing are performed using the annotated dataset. After 200 epochs of training, the optimal weights are obtained, ultimately achieving mixed particle field morphology recognition. This method can achieve high-precision identification of particle morphology in mixed particle fields, providing technical support for acquiring cloud particle field information.

The invention discloses a rock permeability testing system in a high-temperature and high-pressure environment and a using method thereof, and belongs to the technical field of geothermal development or coal in-situ gasification mining. The test system is composed of a stress loading system, a test kettle assembly and a magnetic particle imaging system. When in use, the stress loading system and the test kettle assembly provide conditions such as high temperature, high pressure, seepage fluid and the like for a test piece; and detecting the spatial distribution state of the nano magnetic induction particles added in the seepage fluid through a magnetic particle imaging system to observe the pore and crack distribution characteristics in the test piece or detecting the nano magnetic induction particles added in the pollutant solution to observe the pollutant migration condition. The test system is scientific in design, simple in structure and easy to operate and maintain, can monitor pore fracture distribution and pollutant migration conditions in the test piece in real time under high-temperature and high-pressure conditions, provides accurate dynamic observation data, and provides important technical support for reservoir assessment and optimization in a complex environment.

The invention belongs to the field of magnetic particle imaging, particularly relates to a zero-inertia magnetism gathering ring magnetic-field-free line magnetic particle imaging system and method, and aims to solve the problems of low magnetic field gradient, high magnetic field control complexity and limited imaging space. The current of a gradient magnetic field coil group is generated by a magnetic field control and imaging module, is output by a signal acquisition and output module, and is amplified and provided by a gradient power amplifier module. The current of the axial excitation magnetic field coil is generated by the magnetic field control and imaging module, is output by the signal acquisition and output module and is amplified and provided by the excitation power amplifier module, and a signal received by the multi-axis detection coil is filtered and amplified by the signal processing unit and then is input to the imaging module by the magnetic field control and imaging module for algorithm reconstruction. According to the invention, the magnetic field gradient and the control precision are obviously improved, and the imaging space of the axial fault plane is realized.

The invention relates to the technical field of magnetic particle imaging, in particular to a non-magnetic field line three-dimensional magnetic particle imaging method and system based on weak gradient coding, and the method comprises the steps: driving a zero magnetic field line to carry out the spiral scanning of an imaging object; exciting a nonlinear response signal generated by magnetic particles of the imaging object; obtaining a two-dimensional image of magnetic particle concentration distribution in the imaging object; performing spatial position coding on the zero magnetic field line; obtaining target magnetic particle concentration distribution on the zero magnetic field line; and obtaining a three-dimensional image of the magnetic particle concentration distribution in the imaging object. According to the invention, the zero magnetic field line along the axial direction is constructed, and the Halbach permanent magnet array is driven to carry out visual field scanning of two-dimensional imaging. Two-dimensional imaging is carried out by adopting axial projection, then three-dimensional reconstruction is carried out under the guidance of the two-dimensional reconstruction image, and the three-dimensional reconstruction image is reconstructed by encoding the zero magnetic field line, that is, the three-dimensional image reconstruction can be completed only by scanning twice, and the imaging speed is higher compared with the traditional three-dimensional tomography.

The invention belongs to the field of image reconstruction of magnetic particle imaging and multi-modal generative artificial intelligence models, particularly relates to a magnetic particle image reconstruction method and system based on a multi-modal diffusion model, and aims to solve the problem that there is no method capable of combining a generative model and a multi-modal imaging technology to realize accurate quantitative reconstruction of MPI. The method comprises the following steps: carrying out integral modeling and discretization operation on a first excitation signal to obtain discrete signals, fitting and superposing the discrete signals to obtain a first response signal, calculating a loss function, and training a model based on the loss function; processing the second time sequence signal by using the trained particle response model to obtain a second response signal; calculating based on the second response signal and the system matrix, gradually adding noise, and constraining to obtain a noise constrained image; and gradually denoising and recovering the noise constraint image in the last step to obtain a final reconstructed image. According to the invention, rapid and high-quality MPI image reconstruction becomes possible.

The invention discloses a multi-particle three-dimensional shape reconstruction method based on projection consistency. According to the method, a three-angle laser interference particle imaging system is used for collecting out-of-focus images of three visual angles, a center M * N pixel range is cut to obtain an out-of-focus speckle image, phase recovery algorithm reconstruction is carried out, a two-dimensional particle shape is obtained, a gray threshold value above 70 is set to be a target contour area, binarization segmentation is carried out, and a target contour image is obtained. And smoothing the target contour area. And carrying out three-dimensional space projection on contours of the four candidate results in Matlab, generating a three-dimensional structure in an intersection region, re-projecting the three-dimensional structure to each view angle, calculating an error S between a re-projected image and an original input projection, and selecting a final reconstruction result with the minimum S. According to the method, through systematic iterative optimization and an error evaluation mechanism, trivial fuzzy interference in a phase recovery process is effectively eliminated, and high-precision reconstruction of a multi-particle three-dimensional shape is realized.

The invention provides a magnetic particle imaging image processing method and device, which can be applied to the technical field of image processing. The method comprises the following steps: performing noise enhancement processing on a magnetic particle imaging noise image by using a Gaussian noise network to obtain a target noise image; n cascaded down-sampling attention layers are utilized to perform multi-level feature extraction on the target noise image to obtain N image features, and the down-sampling attention layers are constructed based on L cascaded down-sampling attention excitation sub-layers; performing feature fusion on the Nth image feature by using a grayscale adaptive learning network layer to obtain an image grayscale enhancement feature, the grayscale adaptive learning network layer being obtained based on adaptive grayscale enhancement learning parameter adjustment; and processing the N image features and the image gray level enhancement features by using N cascaded up-sampling attention layers to obtain a magnetic particle imaging de-noised image, the up-sampling attention layers being constructed based on L cascaded up-sampling attention excitation sub-layers.

The invention belongs to the field of biomedical imaging, particularly relates to a multicolor magnetic particle imaging method and system based on magnetic field free line projection decoding, and aims to solve the problems of low imaging efficiency and quality caused by the absence of a relaxation-based multicolor imaging method by using a magnetic field free line in the prior art. The method comprises the following steps: respectively placing N kinds of magnetic nanoparticles in an imaging view center for scanning, and obtaining a time-frequency spectrum center spectral line by adopting time-frequency analysis; scanning an imaging object, acquiring a voltage response signal and performing time-frequency analysis to obtain a time-frequency spectrum; a linear equation set is constructed and solved, and all unknown quantities are obtained; discretely rotating the free line of the magnetic field by P angles, and obtaining the content distribution of N magnetic nanoparticles at each angle; and constructing a sinogram of the N magnetic nanoparticles, performing back projection reconstruction to obtain multicolor images, and superposing the multicolor images to obtain a reconstructed image. According to the invention, relaxation-based multicolor imaging is realized by using the free line of the magnetic field, and the imaging efficiency and quality are improved.

The invention provides an acid response magnetic particle imaging probe and a preparation method and application thereof.The preparation method comprises the steps that S1, a magnetic core, an iron precursor and long-chain alcohol diol are dispersed in a mixed solution of oleic acid, oleylamine, cyclohexane and octadecene, a reaction is conducted for 30-90 minutes under the inert atmosphere condition of 200-300 DEG C, a first non-polar solvent is used for washing, precipitation and centrifugation, and a first non-polar solvent is obtained; the oil-phase double-magnetic core-shell nanoparticles are obtained; s2, preparing water-phase aminated double-magnetic core-shell nanoparticles from the oil-phase double-magnetic core-shell nanoparticles and polymers with amino groups by adopting a film dispersion method or a nano coprecipitation method; s3, the aqueous-phase aminated double-magnetic core-shell nanoparticles and a compound with multiple aldehyde groups are subjected to an aldehyde-amine condensation reaction, a stable imine bond mediated nanometer assembly structure is formed, and the acid response magnetic particle imaging probe is obtained. The probe provided by the invention can respond to the change of the acid microenvironment, has high sensitivity, low background noise and a relatively strong imaging effect, and is suitable for dynamically monitoring diseases related to the acid microenvironment in real time.

Several calibration methods for particle imaging systems are proposed that allow the determination of lateral focus shifts as a function of focusing changes or refocusing. Distortions in particle-optical images generated with appropriately calibrated systems can thus be reduced, and metrological investigations in these images, and especially in 3D tomography, can be performed with greater accuracy. With appropriately calibrated particle imaging systems, 3D samples, such as deep channels in semiconductor samples, can be measured more precisely. Distortion effects arising from sample geometries in electrostatic immersion fields can also be calibrated and thus corrected.

The invention provides a dynamic self-adaptive range compensator imaging system, which belongs to the technical field of particle imaging equipment, and comprises a particle track detection module used for screening particles directly penetrating through a detector, reconstructing the track and direction of particle motion, and obtaining the energy and position information when particles are incident; the self-adaptive range compensation module is used for realizing dynamic self-adaptive compensation of the particle residual range by adjusting the effective thickness of the compensator so as to receive the particle signal and obtain the residual range corresponding to the residual energy when the particle penetrates out of the imaged object; wherein the effective thickness of the compensator refers to the thickness of the compensator in the particle incidence range along the particle incidence direction; and the image processing module is used for calculating and outputting an image according to the residual range of the imaged object under the conditions of different positions and angles. Through the dynamic compensator, (quasi) continuous range compensation is realized, the precision is improved, and a better detection effect is realized while the cost is reduced.

A tunnel leakage water seepage tracing device disclosed by the present invention comprises a model box, a seepage tracing device, a water level control system and a leakage water collection system, the front side of the model box is provided with a round hole, the round hole is used for placing a tunnel model, the seepage tracing device is arranged at the upper part of the model box, and the seepage tracing device comprises an infusion bag containing pigment. A dripping speed control valve is arranged on the lower portion of the infusion bag, the water level control system is connected to the upper portion and the side face of the model box, and the leakage water collecting system is used for collecting leakage water seeping from the placed tunnel model and recording the flow of the leakage water. The device not only can trace streamlines around a crack, but also can convert position information and time information of tracer particles into velocity vector information of flow of a flow field through planar particle imaging velocity measurement, and further analyzes flow characteristics of the flow field; the influence of different leakage point positions on water leakage can be summarized; the seepage path is tracked through the critical crack width, and the range of the crack is determined.

The invention relates to the technical field of medical imaging, in particular to a narrowband-based multi-harmonic magnetic particle imaging method, which comprises the following steps of: determining a magnetic particle imaging area, and acquiring a first area and a second area according to the magnetic particle imaging area; placing a magnetic nanoparticle sample in the first area, externally applying a magnetic field, and extracting harmonic signals to construct a system matrix; placing a measured object in the second area and externally applying a magnetic field, and extracting harmonic signals to construct a harmonic signal matrix of the measured object; and according to the system matrix and the harmonic signal matrix of the measured object, constructing an equation to be solved and carrying out inversion solution to obtain an image of magnetic nanoparticle concentration distribution. Compared with a broadband imaging technology, the narrow-band imaging technology is adopted, the requirement for the bandwidth of a magnetic particle imaging system is lowered, and the problem of insufficient bandwidth under high-frequency excitation is solved.

The invention discloses a method for measuring the molar concentration of nano-particles. The method comprises the following steps: diluting a nano-particle suspension with a high-molecular polymer solution or dispersing nano-particle powder into the high-molecular polymer solution; transferring the suspension liquid to a spacing net on the side of a sample pool in an electrophoresis tank; nano-particles migrate from the sample pool to the buffer pool under the driving of the electric field and are uniformly distributed on the spacing net in a single-particle manner; performing single-particle imaging on the spacing net by using an optical microscope; and counting the number of the nanoparticles in the image so as to measure the molar concentration of the nanoparticles in the sample. The method can be used under the condition that the properties of the nanoparticles are unknown or no standard substance exists, the detection object has no additional condition, and the accuracy is high.