Ultrasonic high-precision bone ranging method, system and probe for noninvasive registration

Abstract

The invention belongs to the technical field of medical ultrasonic data processing, and discloses an ultrasonic high-precision bone ranging method, system and probe for noninvasive registration. The first receiving array element and the second receiving array element convert the sound pressure of the received multiple groups of sound pressure echo signals into electric signals, then the electric signals are amplified, low-frequency interference and ultrasonic higher harmonics are filtered out to obtain harmonic voltage signals, and echo data D are obtained through an analog-to-digital converter and temporarily stored in a single-chip microcomputer; when the upper computer sends instruction request data, the lower computer uploads echo data to the upper computer, waveform display is carried out on the echo data on the upper computer, and a measurement distance is calculated based on a bone surface echo detection algorithm. The invention has the advantages of noninvasive property, rapidness, accuracy (the error is not greater than 1mm) and the like, and has the advantages of miniaturization, convenience in operation, easiness in integration, good targeting accuracy, low cost and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of medical ultrasonic data processing, and in particular relates to an ultrasonic high-precision bone ranging method, system and probe for non-invasive registration. Background Art

[0002] Medical ultrasound technology has the advantages of being non-invasive, non-ionizing radiation, good targeting, and repeatable treatment in clinical practice. Type A ultrasound has been clinically used to measure the thickness of the eye canthus and the length of the eye axis.

[0003] Ultrasonic ranging is widely used in industry. The principle of ultrasonic bone ranging is similar to that of industrial ultrasonic rangefinders and ultrasonic non-destructive testing. It calculates the distance by identifying the time interval between the ultrasonic transmission wave and the ultrasonic echo of the object to be measured (i.e., the bone surface).

[0004] Medical ultrasound imaging technology has been regarded as a mature and stable technology, and researchers continue to explore ways to improve ultrasound image quality and develop new ultrasound imaging technologies. However, less attention has been paid to combining medical ultrasound technology with new treatment methods.

[0005] Computer-assisted surgical navigation technology uses computer graphics and image processing technology to align the virtual image model of the patient's surgical site with the actual spatial position of the surgical site. It is of great significance to the development of intelligent surgical robots and improving surgical efficiency. Registration is a key step in computer-assisted surgical navigation. The spatial position of the pre-scanned patient CT (Computed Tomography) or MRI (Magnetic Resonance Imaging) image is matched with the actual position coordinates in order to accurately perform the preset surgical procedure. Traditional registration methods usually use a mechanical probe to invasively puncture the tissue and place the apex of the mechanical probe close to the bone surface for coordinate acquisition.

[0006] The disadvantages of this traditional registration method are that it is complex, time-consuming and invasive. When more points need to be registered, both doctors and patients will face long operations. In addition, patients with wounds have a poor prognosis, and it is difficult to repeat sampling, and batch real-time sampling is not possible.

[0007] Some researchers have proposed that ultrasound can be used to replace probe puncture positioning to achieve non-invasive, rapid and real-time sampling. However, there is currently no instrument that uses ultrasound to measure the thickness of tissue between skin and bone. Traditional A-ultrasound and B-ultrasound instruments are large in size and have closed system interfaces, which are not convenient for integration into surgical navigation systems and are not conducive to the alignment operation process. In addition, the large area of ​​the probe leads to a large deviation between the measurement position and the positioning point, and the measurement error increases. The thin tissue thickness in certain parts (such as the ankle) exceeds the lower limit of the measurable range of traditional A-ultrasound instruments.

[0008] Through the above analysis, the problems and defects of the existing technology are as follows: the registration method using a mechanical probe to puncture into the bone surface in computer-assisted surgical navigation is complex, time-consuming and invasive. When more points need to be registered, both doctors and patients need to face a long operation time, and the patient's prognosis is poor. This method is not easy to repeat sampling and cannot perform batch real-time sampling.

[0009] Ultrasound registration can be used for non-invasive, fast and real-time registration. Traditional A-ultrasound and B-ultrasound instruments are large in size and have closed system interfaces, which are not convenient for integration into surgical navigation systems and are not conducive to the registration process. The large probe area leads to large deviations between the measurement position and the positioning point, resulting in large measurement errors. The thin tissue thickness of specific parts (ankle) is beyond the measurable range of traditional A-ultrasound instruments. Summary of the invention

[0010] In order to overcome the problems existing in the related art, the disclosed embodiments of the present invention provide an ultrasonic high-precision bone ranging method, system and probe for non-invasive registration. In view of the problems existing in the application of traditional medical ultrasonic instruments in computer-assisted surgical navigation positioning registration, the present invention develops a special ultrasonic registration method to achieve non-invasive, accurate, fast and real-time measurement registration.

[0011] The technical solution is as follows: an ultrasonic high-precision bone distance measurement method for non-invasive registration, comprising:

[0012] S1, the transmitting array element of the micro ultrasonic transducer probe transmits ultrasonic waves to the object under test, and the receiving array element arranged symmetrically with the transmitting array element array receives the signal emitted by the transmitting array element and the echo signal emitted by the object under test;

[0013] S2, the receiving array element converts the sound pressure of the received multiple groups of echo signals into a voltage signal V1, amplifies the voltage signal V1 by gain, obtains an amplified voltage signal V2, and filters the amplified voltage signal V2 through a bandpass filter to remove low-frequency interference and ultrasonic high-order harmonics to obtain a harmonic voltage signal V3. The harmonic voltage signal V3 obtains echo data D through an analog-to-digital converter and temporarily stores it in the single-chip microcomputer;

[0014] S3, when the upper computer sends a command requesting data, the lower computer uploads the echo data to the upper computer and displays the waveform on the upper computer. The measured distance is calculated based on the bone surface echo detection algorithm and automatically displayed.

[0015] In step S1, a receiving array element arranged symmetrically with the axis of the transmitting array element array receives a signal sent by the transmitting array element and an echo signal sent by the object to be measured, including: the first transmitting array element transmits a ranging pulse to the object to be measured, the first receiving array element receives a group of echo signals, the first transmitting array element transmits a ranging pulse again, the second receiving array element receives a group of echo signals, after the first transmitting array element completes sampling, the second transmitting array element transmits a ranging pulse, the first receiving array element and the second receiving array element respectively receive a group of echo signals, the micro ultrasonic transducer probe instantaneously collects a group of ultrasonic echo data of a length of U=4096 time domain data at one time, and so on, according to the operation time of the main control chip of the micro ultrasonic transducer probe and the real-time measurement speed requirement, the four groups of data obtained by the four combinations of transmission and reception of each array element are calculated as a large group;

[0016] The waveform X(t) of the ultrasonic ranging pulse emitted by the first transmitting array element and the second transmitting array element is as follows:

[0017]

[0018] Where X(t) is the waveform of the ultrasonic ranging pulse, x(t) is the pulse signal, f is the ultrasonic center operating frequency, k is the number of pulses, and t is the emission time;

[0019] The ultrasonic center operating frequency f = 7.5MHz, the number of pulses k = 6, and the pulse signal x(t) is expressed as:

[0020]

[0021] Where A is the pulse signal amplitude, and b is the serial number of the transmitted pulse wave.

[0022] In step S3, the bone surface echo detection algorithm is based on the human body's arms, calves, knees, and ankles, and uses an A-ultrasound bone surface distance detection bone surface echo detection algorithm, including:

[0023] (1) The collected 4N sets of ultrasonic echo data are pre-processed and uploaded to the host computer, the data with index n in the waveform is recorded as D1(n), and D1(n) is Gaussian filtered to generate Gaussian filtered data D2(n);

[0024] (2) extracting the data envelope from the Gaussian filter data D2(n) using Hilbert transform to obtain the data envelope data D3(n);

[0025] (3) Binarizing the data envelope data D3(n) using a dynamic threshold to obtain binary data D4(n);

[0026] (4) performing pulse width identification on the binary data D4(n) to retain the envelope band with the same width range as the transmitted wave, and filtering out the waveforms outside the envelope band with the same width range as the transmitted wave;

[0027] (5) Extract the first five envelope bands in each group of data according to the intensity, and calculate the calculated distance d of each envelope wave in all groups ij , where i represents different echo data, and j is the index of the five bands in each set of data;

[0028] Taking the index position of the maximum envelope amplitude as the center, select 10 points before and after, and calculate the band mean square root r corresponding to the band ij ;

[0029] (6) Using the common feature values ​​between the data to perform cross-validation to select the ultrasonic bone echo: All the statistical distance values ​​d ij Subtract all the distance values ​​from other groups, and regard the echo bands with distance difference less than 0.5mm as echoes at the same position, recorded as similar distance bands, and subtract all similar distance bands into groups to generate several similar distance groups;

[0030] (7) Credibility feedback: The calculated amplitude credibility and consistency credibility reference indicators are used to evaluate the influence of the bone surface and measurement angle on the bone surface distance measurement.

[0031] In step (1), the expression of Gaussian filter data D2(n) is:

[0032]

[0033] Where, σ, μ are both standard normal distributions, σ=1, μ=0, e is the Euler number, and the length of the Gaussian template is 2s+1, s=2.

[0034] In step (2), the Hilbert transform is used to extract the data envelope of the Gaussian filter data D2(n) to obtain the data envelope data D3(n); the expression is:

[0035]

[0036] Where m is the position index of the result sequence, and n is the position index in D2.

[0037] In step (3), the expression of the binary data D4(n) is:

[0038]

[0039] Where T is the first quartile of D3(n).

[0040] In step (5), the calculated distance d of each envelope wave is ij The expression is:

[0041]

[0042] In the formula, K b is the compensation coefficient, V is the sound velocity in the medium to be measured, P end is the peak position of the echo, P stand is the peak position of the transmitted wave, f c is the sampling frequency;

[0043] Corresponding band root mean square r ij The calculation formula is:

[0044]

[0045] In the formula, U is the width of the echo, g is the position index of the echo signal, and x g is the index position corresponding to g.

[0046] In step (7), the calculated amplitude credibility is used, including:

[0047] Sum all the RMS values ​​in the same similar distance group R = ∑sr ij , the R of all similar groups is linearly normalized to obtain the echo amplitude credibility P. The linear normalization formula is:

[0048]

[0049] In the formula, R min ,R max Represent the minimum and maximum values ​​of R in all similar groups, respectively;

[0050] Calculate the consistency reliability, including: The consistency reliability Q is the frequency of a certain similar distance appearing in different echo signals. The larger the value, the more times it appears in different echo signals. The expression is:

[0051]

[0052] In the formula, A c is the number of times the distance value appears in each group of echo signals;

[0053] The range of P and Q is between 0 and 1. When Q>0.5 and P>0.8, it is considered that a valid echo is detected. The average distance of the band group with similar distance d corresponding to the maximum Q and P is selected. As a final measurement, the expression is:

[0054]

[0055] In the formula, S is the number of similar bands in the group;

[0056] If Q<0.5 or P<0.8, it is considered that no valid echo is detected, so P, Q, Set to zero.

[0057] Another object of the present invention is to provide an ultrasonic high-precision bone distance measurement driving control system for non-invasive registration, the system implements the ultrasonic high-precision bone distance measurement method for non-invasive registration, and the system comprises:

[0058] The main control chip is used to generate a 7.5MHz pulse signal, which is driven to emit ultrasound after power amplification through a bus control chip; the ultrasound wave forms an echo ultrasound signal after reflection, and the echo ultrasound signal senses an echo electrical signal through the probe; the signal acquisition circuit performs impedance matching and pre-amplification on the echo electrical signal, and the amplified signal is transmitted to the analog-to-digital conversion chip for data conversion after 7-8Mhz bandpass filtering. The data obtained by the analog-to-digital conversion is first stored in the lower computer main control chip, and then further processed in the lower computer according to different needs to obtain the final measurement result and then transmitted to the upper computer, or the original waveform data is directly transmitted to the upper computer, and C# language is used as the upper computer software based on the .NET Framework framework, and the lower computer device is communicated through the RS-485 serial port. The upper computer software is used to remotely control the transmission and reception of A-ultrasound equipment, real-time display of waveforms, batch access of historical data, and automatically identify and display the bone surface distance in real time using the bone surface echo detection algorithm.

[0059] Another object of the present invention is to provide a miniature ultrasonic transducer probe, which implements the ultrasonic high-precision bone ranging method for non-invasive alignment. The miniature ultrasonic transducer probe is an axially symmetrical structure of a circular array with 4 elements and a base frequency of 7.5 MHz.

[0060] Combining all the above technical solutions, the beneficial effects of the present invention are as follows: the present invention has high accuracy, automatic detection and display, and non-invasiveness. Compared with the traditional mechanical probe insertion registration, it has the advantages of non-invasiveness, rapidity, and accuracy (error is not greater than 1mm). Compared with the existing A / B ultrasound instruments, it has the advantages of miniaturization, convenient operation, easy integration, good targeting accuracy, and low cost.

[0061] The traditional computer-assisted navigation surgery registration method is to collect the marking points for registration by implanting reference markers or mechanical probes, but this method often requires invasive contact with the bone surface, which increases the complexity of the operation and prolongs the operation time. To this end, we explored ultrasound as an alternative technology for non-invasive detection. The present invention solves the technical difficulties of non-invasive registration and fills the technical gap of A-ultrasound high-precision human body ranging (error is not more than 1mm) at home and abroad. In addition, compared with the disadvantages of traditional CT machines that are too large and too expensive, the A-ultrasound ranging equipment produced by the present invention is small in size and low in cost; the present invention is expected to be applied to the clinical registration stage of various surgeries, such as computer-assisted navigation surgery. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] The accompanying drawings herein are incorporated in and constitute a part of the specification, illustrate embodiments consistent with the present disclosure, and together with the description, serve to explain the principles of the present disclosure;

[0063] Figure 1 is a flow chart of an ultrasonic high-precision bone ranging method for non-invasive registration provided by an embodiment of the present invention;

[0064] Figure 2 It is a schematic diagram of an ultrasonic high-precision bone ranging drive control system for non-invasive registration provided by an embodiment of the present invention;

[0065] Figure 3 It is a diagram of the upper computer software interface provided by an embodiment of the present invention;

[0066] Figure 4 is a schematic diagram of a high-precision ultrasonic bone ranging method for non-invasive registration provided by an embodiment of the present invention;

[0067] Figure 5 is a waveform diagram of ultrasonic ranging transmission actually measured according to an embodiment of the present invention;

[0068] Figure 6 It is a flow chart of a bone surface echo detection algorithm dedicated to A-ultrasound bone surface distance detection provided by an embodiment of the present invention;

[0069] Figure 7 It is a curve diagram of measured values ​​at different distances of the underwater aluminum plate experiment provided by an embodiment of the present invention;

[0070] Figure 8 It is a box diagram of the measurement error distribution of the aluminum plate in water at 25° and 48° provided by an embodiment of the present invention;

[0071] Fig. 9 It is a box plot of measurement error distribution of pork aluminum plate at water temperatures of 25° and 48° provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0072] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific implementation disclosed below.

[0073] The innovation of the present invention is that the present invention develops a special ultrasonic registration method with a frequency of 7.5MHz and four array elements and builds a test device to achieve non-invasive, accurate, fast and real-time measurement and registration of human bones. The measurement range is 3mm-45mm, and the measurement accuracy is within 1mm and can be stably applied to human body measurement. The present invention greatly reduces the cost of clinical surgical registration and improves the efficiency of pre-operative registration.

[0074] Embodiment 1, as Figure 1 As shown, the ultrasonic high-precision bone ranging method for non-invasive registration provided by the embodiment of the present invention includes:

[0075] S1, the transmitting array element of the micro ultrasonic transducer probe transmits ultrasonic waves to the object under test, and the receiving array element arranged symmetrically with the transmitting array element array receives the signal emitted by the transmitting array element and the echo signal emitted by the object under test;

[0076] S2, the receiving array element converts the sound pressure of the received multiple groups of echo signals into a voltage signal V1, amplifies the voltage signal V1 by gain, obtains an amplified voltage signal V2, and filters the amplified voltage signal V2 through a bandpass filter to remove low-frequency interference and ultrasonic high-order harmonics to obtain a harmonic voltage signal V3. The harmonic voltage signal V3 obtains echo data D through an analog-to-digital converter and temporarily stores it in the single-chip microcomputer;

[0077] S3, when the upper computer sends a command requesting data, the lower computer uploads the echo data to the upper computer and displays the waveform on the upper computer. The measured distance is calculated based on the bone surface echo detection algorithm and automatically displayed.

[0078] Example 2: To meet the measurement range and accuracy requirements of different patients and different parts, the present invention provides a miniature ultrasonic transducer probe. Based on the CT data of the calf, ankle, and arm of different patients, the finite difference time domain (FDTD) method is used to solve the Westervelt ultrasonic nonlinear propagation equation:

[0079]

[0080] In the formula, is the Laplace operator, p is the sound pressure, c is the sound speed, ρ is the density, is the partial differential symbol, t is time, β is the nonlinear coefficient, δ is the diffusion coefficient, δ=2c 3 a / w 2 , a is the absorption coefficient, w is the angular frequency, w=2πf.

[0081] The three-dimensional numerical simulation model of the sound field was established, and the measurement accuracy of different transducer structure designs and frequencies was calculated by numerical simulation. Finally, a circular array axisymmetric structure with 4 array elements and a base frequency of 7.5MHz was selected, and the manufactured probe was a miniature planar transducer with an array element diameter of 2mm and a probe diameter of 8.5mm. In order to meet the measurement requirements and measurement accuracy requirements of different thickness parts (range: 4-40mm), 7.5MHz was determined as the optimal center frequency of the transducer probe based on the simulation results.

[0082] Example 3: To facilitate embedding into a computer-assisted surgical navigation system, the measuring device is miniaturized and the control protocol is opened. An ultrasonic high-precision bone ranging drive control system for non-invasive registration is proposed (e.g. Figure 2 ) and develop supporting host computer software.

[0083] The ultrasonic high-precision bone ranging drive control system for non-invasive registration uses the STM32FH743 chip as the main control to generate a 7.5MHz pulse signal. It drives the transducer to emit ultrasound after power amplification through the bus control STHV748 chip. The power amplifier circuit is powered by an ±80V external power supply. The ultrasound wave is reflected by human tissue to form an echo ultrasound signal, and the echo ultrasound signal is sensed by the probe to produce an echo electrical signal. The signal acquisition circuit uses the AD8336 chip to perform impedance matching and pre-amplification on the echo electrical signal. The amplified signal is transmitted to the AD9226 analog-to-digital conversion chip for data conversion after 7-8Mhz bandpass filtering. The analog-to-digital conversion rate is 28.5MHz. The data obtained by analog-to-digital conversion is first stored in the master control chip of the lower computer. According to different needs, the lower computer can be further processed to obtain the final measurement result and then transmitted to the upper computer, or the original waveform data can be directly transmitted to the upper computer, and the computing power of the upper computer can be used for more detailed analysis. The drive control and receiving circuit realizes the functions of 7.5MHz instantaneous short pulse ultrasonic emission and weak ultrasonic signal reception.

[0084] The supporting host computer software was developed using C# language based on the .NET Framework ( Figure 3 ), and communicate with the lower computer equipment through the RS-485 serial port. The software realizes remote control of A-ultrasound equipment transmission and reception, real-time waveform display, and batch access of historical data. The software integrates the bone surface echo detection algorithm disclosed in the present invention and can automatically identify and display the bone surface distance in real time.

[0085] Example 4, as another embodiment of the present invention, Figure 4 As shown, the ultrasonic high-precision bone ranging method for non-invasive registration provided by the embodiment of the present invention includes:

[0086] When starting to measure the distance, the first transmitting array element first transmits a ranging pulse to the object under test, and the first receiving array element and the second receiving array element receive two sets of echo signals. After the first transmitting array element completes sampling, the second transmitting array element transmits a ranging pulse, and the first receiving array element and the second receiving array element receive two sets of echo signals. Four sets of ultrasonic echo data with a length of 4096 can be instantly collected at one time (the number of collections takes into account the computing time of the main control chip and the real-time measurement speed requirements. If more data is needed, 4×N sets of data can be obtained by repeated sampling N times).

[0087] The waveform X(t) of the ultrasonic ranging pulse emitted by the first transmitting array element and the second transmitting array element is as follows:

[0088]

[0089] Where X(t) is the waveform of the ultrasonic ranging pulse, x(t) is the pulse signal, f is the ultrasonic center operating frequency, k is the number of pulses, and t is the emission time;

[0090] The ultrasonic center operating frequency f = 7.5MHz, the number of pulses k = 6, and the pulse signal x(t) is expressed as:

[0091]

[0092] Where A is the pulse signal amplitude, and b is the serial number of the transmitted pulse wave.

[0093] Among them, the measured ultrasonic ranging transmission waveform is as follows Figure 5 shown.

[0094] The first receiving array element and the second receiving array element collect the sound pressure and convert it into a voltage signal V1, and then amplify the weak signal by gain V2. V2 is filtered out by a 7-8Mhz bandpass filter to remove low-frequency interference and ultrasonic high-order harmonics to obtain V3. V3 obtains echo data D through an analog-to-digital converter and temporarily stores it in the microcontroller. When the host computer sends a command requesting data, the lower computer uploads the echo data to the host computer and displays the waveform on the host computer and calculates the measured distance based on the bone surface echo detection algorithm.

[0095] Among them, the bone surface echo detection algorithm includes: The key to this non-invasive ultrasonic bone ranging method is to accurately identify the bone surface echo. Compared with the single propagation medium waveform of industrial ultrasound, human tissues include skin, muscle, fat, etc. Ultrasound will generate echoes when passing through different tissue interfaces. A-ultrasound bone ranging contains more interference and clutter. Using the traditional threshold method for echo judgment will lead to problems such as poor accuracy, poor reliability, and inaccurate detection of echoes.

[0096] The A-ultrasound distance measurement result is the average of the bone surface distance within the range covered by the probe. The ultrasound probe must be miniaturized to achieve accurate measurement of the target, otherwise it will be interfered by the bone around the target. However, the miniature probe has the problem of low rated sound power and weak received signal, which makes the ultrasound echo feature not significant and is greatly affected by interference. Traditional A-ultrasound equipment and ranging algorithms cannot be used for bone surface distance detection.

[0097] In view of the above problems, the present invention develops a bone surface echo detection algorithm dedicated to bone surface distance detection by A-ultrasound based on numerical simulation and experimental data of different parts of the human body such as arms, calves, knees, ankles, etc. Figure 6 ), some of the key parameters are determined based on empirical values ​​of measured results at different locations.

[0098] The collected 4N groups of ultrasonic echo data are pre-processed and uploaded to the host computer. The data with index n in the waveform is recorded as D1(n). Gaussian filtering is performed on D1(n) to generate D2(n):

[0099]

[0100] Where, σ, μ are both standard normal distributions, σ=1, μ=0, e is the Euler number, and the length of the Gaussian template is 2s+1, s=2.

[0101] Use Hilbert transform to extract the data envelope of D2(n) to get D3. The Hilbert transform formula is as follows:

[0102]

[0103] Where m is the position index of the result sequence, and n is the position index in D2.

[0104] Then, D3(n) is binarized using a dynamic threshold:

[0105]

[0106] Where T is the first quartile of D3(n).

[0107] Perform pulse width identification on D4(n) to retain the envelope band with the same width range as the transmitted wave (20-40 sampling points) and filter out other waveforms.

[0108] Extract the first five envelope bands in each group of data according to the intensity, and calculate the calculated distance d of each envelope wave in all groups ij And the corresponding band root mean square r ij , where i represents different groups and j is the index of the 5 bands in each group.

[0109] Single envelope wave distance calculation formula:

[0110]

[0111] In the formula, K b represents the compensation coefficient, V is the sound velocity in the medium to be measured, and P end is the peak position of the echo, P stand is the peak position of the transmitted wave, f c is the sampling frequency.

[0112] Taking the index position of the maximum envelope amplitude as the center, select 10 points before and after, and calculate the root mean square value r corresponding to the band ij :

[0113]

[0114] In the formula, U is the width of the echo, g is the position index of the echo signal, and x g is the index position corresponding to g.

[0115] The common characteristic values ​​between the data are cross-validated to screen out the ultrasonic bone echo: all the statistical distance values ​​d ij , and subtract them from all the distance values ​​of other groups respectively. The echo bands with distance difference less than 0.5mm are regarded as echoes at the same position, which are recorded as similar distance bands here. All similar distance bands are grouped by subtracting them in turn to generate several similar distance groups.

[0116] Credibility feedback: Ultrasonic measurement of bone surface distance needs to consider the impact of complex bone surface structure on the measurement, as well as the impact of the measurement angle. In order to improve the reliability of the bone surface distance detection results, feedback is given on the test results, and amplitude credibility and consistency credibility are given as reference indicators for the operator's measurement technique and data credibility.

[0117] Amplitude confidence: sum all RMS values ​​in the same similar distance group R = ∑sr ij , then all similar groups R are linearly normalized to obtain the amplitude credibility P. The amplitude credibility indicates the strength of the echo signal characteristics of the distance value. Linear normalization formula:

[0118]

[0119] In the formula, R min ,R max Represent the minimum and maximum values ​​of R in all similar groups, respectively;

[0120] Consistency reliability: The consistency reliability Q is the frequency of a similar distance appearing in different echo signals. The larger the value, the more times it appears in different echo signals.

[0121]

[0122] In the formula, A c is the number of times the distance value appears in each group of echo signals;

[0123] The range of P and Q is between 0 and 1. When Q>0.5 and P>0.8, it is considered that a valid echo is detected. The average distance of the band group with similar distance d corresponding to the maximum Q and P is selected. As a final measurement, the expression is:

[0124]

[0125] In the formula, S is the number of similar bands in the group;

[0126] If Q<0.5 or P<0.8, it is considered that no valid echo is detected, so P, Q, Set to zero.

[0127] Based on human experimental data, this algorithm can determine the echo point within the range of 40 sampling points through mutual verification of multiple groups of echo signals, with a measurement accuracy of up to 1mm. It has better anti-interference ability and reliability than traditional methods.

[0128] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0129] Since the information interaction, execution process, etc. between the above-mentioned devices / units are based on the same concept as the method embodiment of the present invention, their specific functions and technical effects can be found in the method embodiment part and will not be repeated here.

[0130] Those skilled in the art can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In practical applications, the above-mentioned function allocation can be completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated in one processing unit, or each unit can exist physically separately, or two or more units can be integrated in one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of the present invention. The specific working process of the units and modules in the above-mentioned system can refer to the corresponding process in the aforementioned method embodiment.

[0131] An embodiment of the present invention further provides a computer device, which includes: at least one processor, a memory, and a computer program stored in the memory and executable on the at least one processor, wherein the processor implements the steps in any of the above-mentioned method embodiments when executing the computer program.

[0132] An embodiment of the present invention further provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps in the above-mentioned method embodiments can be implemented.

[0133] An embodiment of the present invention further provides an information data processing terminal, which, when executed on an electronic device, provides a user input interface to implement the steps in the above method embodiments. The information data processing terminal is not limited to mobile phones, computers, and switches.

[0134] An embodiment of the present invention further provides a server, which is used to provide a user input interface to implement the steps in the above method embodiments when executed on an electronic device.

[0135] An embodiment of the present invention provides a computer program product. When the computer program product runs on an electronic device, the electronic device can implement the steps in the above-mentioned method embodiments when executing the computer program product.

[0136] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present application implements all or part of the processes in the above-mentioned embodiment method, which can be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of the above-mentioned various method embodiments when executed by the processor. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may at least include: any entity or device that can carry the computer program code to the camera / terminal device, a recording medium, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium. For example, a USB flash drive, a mobile hard disk, a disk or an optical disk.

[0137] The examples of the present invention were used to carry out underwater aluminum plate experiments, pork aluminum plate experiments and pork femur experiments. The experimental results show that the measurement accuracy of the scheme can reach 1mm, and it works stably and has high consistency in various experimental scenarios, which verifies the accuracy and reliability of the method.

[0138] Aluminum plate experiment in water: install the ultrasonic probe and the reflective aluminum plate at both ends of the distance precision control device, and then place it in a 25° constant temperature water tank (medium sound velocity: 1508m / s). Use the distance control device to control the distance to gradually increase from 4mm to 40mm, and record the measured values ​​at different distances, such as Figure 7 Curve of measured values ​​at different distances in the underwater aluminum plate experiment.

[0139] The pork aluminum plate experiment is to replace the intermediate medium with pork, and the other conditions are the same as the aluminum plate experiment in water. The distance control method to be measured is: first use the distance control device to set the distance and then fill the pork tightly between the transducer and the aluminum plate. The measurement results at distances of 9.4, 19.4, 24.4, 26.4, and 35.4 mm are shown in the following table, and the absolute error is less than 1 mm.

[0140] Table 1: Experimental measurement results of pork aluminum plates with different thicknesses

[0141] Actual distance (mm) 9.40 19.40 24.40 26.40 36.40 Test distance (mm) 9.88 19.43 23.90 25.98 35.89 Error(mm) -0.48 -0.03 0.50 0.42 0.51

[0142] The water temperature was controlled at 25° and 48° for aluminum plates in water and 25° for pork aluminum plates, and the measurements were repeated 20 times at distances of 4, 6, 8, 10, 20, and 40 mm. The results are shown in Figure 8 Box plot of measurement error distribution of aluminum plate in water at 25° and 48°. Fig. 9 Box plot of measurement error distribution of pork aluminum plate at water temperatures of 25° and 48°;

[0143] Pork femur experiment: Fresh pork was used as the transmission medium and the pig femur as the reflector. At room temperature of 25°, ultrasonic coupling agent was applied to the pork surface and the ultrasonic transducer probe was placed on the pork surface for measurement. The actual measurement values ​​of pork of different thicknesses are shown in Table 2. The absolute error of the measurement is less than 1mm. This experiment verifies the usability of real tissue and bone.

[0144] Table 2: Test results of pork and pig femur with different thicknesses

[0145] Actual thickness(mm) 11.00 18.00 26.00 33.00 37.00 Test thickness(mm) 11.03 17.17 26.16 32.88 36.61 Error(mm) -0.03 0.83 -0.16 0.12 0.39

[0146] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principles of the present invention should be covered within the protection scope of the present invention.

Claims

1. An ultrasonic high-precision bone distance measurement method for non-invasive registration, characterized in that: The method includes: S1, the transmitting array element of the micro ultrasonic transducer probe transmits ultrasonic waves to the object under test, and the receiving array element arranged symmetrically with the transmitting array element array receives the signal emitted by the transmitting array element and the echo signal emitted by the object under test; S2, the receiving array element converts the sound pressure of the received multiple groups of echo signals into a voltage signal V1, amplifies the voltage signal V1 by gain, obtains an amplified voltage signal V2, and filters the amplified voltage signal V2 through a bandpass filter to remove low-frequency interference and ultrasonic high-order harmonics to obtain a harmonic voltage signal V3. The harmonic voltage signal V3 obtains echo data D through an analog-to-digital converter and temporarily stores it in the single-chip microcomputer; S3, when the upper computer sends a command requesting data, the lower computer uploads the echo data to the upper computer and displays the waveform on the upper computer. The measured distance is calculated based on the bone surface echo detection algorithm and automatically displayed.

2. The ultrasonic high-precision bone distance measurement method for non-invasive registration according to claim 1, characterized in that: In step S1, a receiving array element arranged symmetrically with the axis of the transmitting array element array receives a signal sent by the transmitting array element and an echo signal sent by the object to be measured, including: the first transmitting array element transmits a ranging pulse to the object to be measured, the first receiving array element receives a group of echo signals, the first transmitting array element transmits a ranging pulse again, the second receiving array element receives a group of echo signals, after the first transmitting array element completes sampling, the second transmitting array element transmits a ranging pulse, the first receiving array element and the second receiving array element respectively receive a group of echo signals, the micro ultrasonic transducer probe instantaneously collects a group of ultrasonic echo data of a length of U=4096 time domain data at one time, and so on, according to the operation time of the main control chip of the micro ultrasonic transducer probe and the real-time measurement speed requirement, the four groups of data obtained by the four combinations of transmission and reception of each array element are calculated as a large group; The waveform X(t) of the ultrasonic ranging pulse emitted by the first transmitting array element and the second transmitting array element is as follows: Where X(t) is the waveform of the ultrasonic ranging pulse, x(t) is the pulse signal, f is the ultrasonic center operating frequency, k is the number of pulses, and t is the emission time; The ultrasonic center operating frequency f = 7.5MHz, the number of pulses k = 6, and the pulse signal x(t) is expressed as: Where A is the pulse signal amplitude, and b is the serial number of the transmitted pulse wave.

3. The ultrasonic high-precision bone distance measurement method for non-invasive registration according to claim 1, characterized in that: In step S3, the bone surface echo detection algorithm is based on the human body's arms, calves, knees, and ankles, and uses an A-ultrasound bone surface distance detection bone surface echo detection algorithm, including: (1) The collected 4N sets of ultrasonic echo data are pre-processed and uploaded to the host computer, the data with index n in the waveform is recorded as D1(n), and D1(n) is Gaussian filtered to generate Gaussian filtered data D2(n); (2) extracting the data envelope from the Gaussian filter data D2(n) using Hilbert transform to obtain the data envelope data D3(n); (3) Binarizing the data envelope data D3(n) using a dynamic threshold to obtain binary data D4(n); (4) performing pulse width identification on the binary data D4(n) to retain the envelope band with the same width range as the transmitted wave, and filtering out the waveforms outside the envelope band with the same width range as the transmitted wave; (5) Extract the first five envelope bands in each group of data according to the intensity, and calculate the calculated distance d of each envelope wave in all groups ij , where i represents different echo data, and j is the index of the five bands in each set of data; Taking the index position of the maximum envelope amplitude as the center, select 10 points before and after, and calculate the band mean square root r corresponding to the band ij ; (6) Using the common feature values ​​between the data to perform cross-validation to select the ultrasonic bone echo: All the statistical distance values ​​d ij Subtract all the distance values ​​from those of other groups, and regard the echo bands with distance differences less than 0.5 mm as echoes at the same position, recorded as similar distance bands. Subtract all similar distance bands in turn to group them into several similar distance groups. (7) Credibility feedback: The calculated amplitude credibility and consistency credibility reference indicators are used to evaluate the influence of the bone surface and measurement angle on the bone surface distance measurement.

4. The ultrasonic high-precision bone distance measurement method for non-invasive registration according to claim 3, characterized in that: In step (1), the expression of Gaussian filter data D2(n) is: Where, σ, μ are both standard normal distributions, σ=1, μ=0, e is the Euler number, and the length of the Gaussian template is 2s+1, s=2.

5. The ultrasonic high-precision bone distance measurement method for non-invasive registration according to claim 3, characterized in that: In step (2), the Hilbert transform is used to extract the data envelope of the Gaussian filter data D2(n) to obtain the data envelope data D3(n); the expression is: Where m is the position index of the result sequence, and n is the position index in D2.

6. The ultrasonic high-precision bone distance measurement method for non-invasive registration according to claim 3, characterized in that: In step (3), the expression of the binary data D4(n) is: Where T is the first quartile of D3(n).

7. The ultrasonic high-precision bone distance measurement method for non-invasive registration according to claim 3, characterized in that: In step (5), the calculated distance d of each envelope wave is ij The expression is: In the formula, K b is the compensation coefficient, V is the sound velocity in the medium to be measured, P end is the peak position of the echo, P stand is the peak position of the transmitted wave, f c is the sampling frequency; Corresponding band root mean square r ij The calculation formula is: In the formula, U is the width of the echo, g is the position index of the echo signal, and x g is the index position corresponding to g.

8. The ultrasonic high-precision bone distance measurement method for non-invasive registration Q according to claim 3, characterized in that: In step (7), the calculated amplitude credibility is used, including: Sum all the RMS values ​​in the same similar distance group R = ∑sr ij , the R of all similar groups is linearly normalized to obtain the echo amplitude credibility P. The linear normalization formula is: In the formula, R min ,R max Represent the minimum and maximum values ​​of R in all similar groups, respectively; Calculate the consistency reliability, including: The consistency reliability Q is the frequency of a similar distance appearing in different echo signals. The larger the value, the more times it appears in different echo signals. The expression is: In the formula, A c is the number of times the distance value appears in each group of echo signals; The range of P and Q is between 0 and 1. When Q>0.5 and P>0.8, it is considered that a valid echo is detected. The average distance of the band group with similar distance d corresponding to the maximum Q and P is selected. As a final measurement, the expression is: In the formula, S is the number of similar bands in the group; If Q<0.5 or P<0.8, it is considered that no valid echo is detected, and P, Q, Set to zero.

9. An ultrasonic high-precision bone ranging drive control system for non-invasive registration, characterized in that: The system implements the ultrasonic high-precision bone ranging method for non-invasive registration as claimed in any one of claims 1 to 8, and the system comprises: The main control chip is used to generate a 7.5MHz pulse signal, which is driven to emit ultrasound after power amplification through a bus control chip; the ultrasound wave forms an echo ultrasound signal after reflection, and the echo ultrasound signal senses an echo electrical signal through the probe; the signal acquisition circuit performs impedance matching and pre-amplification on the echo electrical signal, and the amplified signal is transmitted to the analog-to-digital conversion chip for data conversion after 7-8Mhz bandpass filtering. The data obtained by the analog-to-digital conversion is first stored in the lower computer main control chip, and then further processed in the lower computer according to different needs to obtain the final measurement result and then transmitted to the upper computer, or the original waveform data is directly transmitted to the upper computer, and C# language is used as the upper computer software based on the .NET Framework framework, and the lower computer device is communicated through the RS-485 serial port. The upper computer software is used to remotely control the transmission and reception of A-ultrasound equipment, real-time display of waveforms, batch access of historical data, and automatically identify and display the bone surface distance in real time using the bone surface echo detection algorithm.

10. A miniature ultrasonic transducer probe, characterized in that: The miniature ultrasonic transducer probe implements the ultrasonic high-precision bone ranging method for non-invasive registration as described in any one of claims 1 to 8. The miniature ultrasonic transducer probe is an axisymmetric structure of a circular array with 4 elements and a base frequency of 7.5 MHz.

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