CN203000923U - Non-contact magnetic induction-type intracranial pressure monitor - Google Patents

Abstract

The utility model relates to a non-contact magnetic induction type intracranial pressure monitor, comprising an excitation source for generating excitation signals and reference signals; and a magnetic induction detection device surrounding the skull to be measured, which is connected to the At the output end of the excitation source, an alternating excitation magnetic field signal is generated according to the excitation signal provided by the excitation source. The excitation magnetic field signal passes through the entire skull under test, and the excitation magnetic field signal and the secondary magnetic field signal are superimposed together to form a phase change relative to the reference signal. The superimposed magnetic field signal; and a phase detector, the phase detector detects the phase difference between the reference signal and the superimposed magnetic field signal, and the phase difference is used to reflect the pressure change produced by the cranial content on the wall of the cranial cavity. The utility model can overcome the defect that when the ICP rises due to early brain lesions, the cerebrospinal fluid and cerebral hemodynamics can regulate, so that the ICP rises little, and the direct ICP monitoring cannot sensitively reflect the changes of early lesions.

Description

Non-contact magnetic induction intracranial pressure monitor

technical field

The utility model belongs to the technical field of biomedical medical equipment, in particular to a non-contact magnetic induction intracranial pressure monitor for neurology and surgery.

Background technique

All kinds of craniocerebral trauma, brain tumor, stroke, cerebral infarction, cerebral ischemia, encephalitis, epilepsy, cerebral hematoma, high altitude cerebral edema and other common diseases in neurology and surgery, most of the cases are violent, critical condition and high mortality rate . Most of these diseases are accompanied by increased intracranial pressure (ICP), which is one of the most common causes of patient deterioration, poor prognosis, secondary brain injury, and death. Accurate, rapid, objective and convenient ICP monitoring is an important means to observe changes in patients' conditions, make early diagnosis, determine treatment plan, guide clinical drug treatment, judge and improve prognosis.

ICP refers to the pressure generated by the contents of the cranium on the wall of the cranial cavity, represented by the pressure of cerebrospinal fluid (CSF). Various existing ICP monitoring methods are based on the correlation between measured physiological parameters and ICP changes, and have various limitations. Invasive ICP monitoring methods, such as intraventricular, intraparenchymal, epidural or subdural, subarachnoid space, lumbar puncture, neuroendoscopy, invasive brain electrical impedance monitoring, etc., are harmful to the human body and patients Painful, easy to cause infection and other problems; CT and MRI imaging methods, there are problems such as relatively expensive inspections, and inability to implement bedside and emergency on-site monitoring. Noninvasive ICP monitoring methods, including ultrasound-based optic nerve sheath diameter, retinal venous or arterial pressure, flash visual evoked potentials, tympanic membrane displacement, bregma manometry, noninvasive EEG impedance, minimally invasive strain electrometry, near-infrared spectroscopy Monitoring, transcranial Doppler, etc., because when the ICP rises due to early brain lesions, the cerebrospinal fluid and cerebral hemodynamics can regulate the ICP, so that the direct ICP monitoring cannot reflect the changes of early lesions sensitively . In addition, the ICP monitoring method has the following problems:

① For patients with severe craniocerebral injury, severe burns, infectious diseases, skin diseases, skin allergies, etc., it is not convenient to use the contact method for monitoring; ② The contact method cannot meet the needs of individualized and aging populations for individualized treatment; ③Contact measurement places many electrodes on the patient’s head, which is inconvenient for clinical use, restricts the patient’s activities, and increases discomfort; ④For special forces, air force pilots, astronauts and other special groups, when monitoring is required in a natural state, contact Traditional methods are not suitable; ⑤ There are different degrees of detection blind spots in various non-invasive ICP monitoring.

In view of the deficiency of existing ICP monitoring methods and the needs of diagnosis and treatment of clinical neurological and surgical diseases, an ICP monitoring method with high sensitivity for early lesions and deep lesions, non-contact magnetic induction, and convenient bedside monitoring is proposed, which can improve the clinical value of neurological and surgical patients. The treatment level is of great significance.

Contents of the invention

The technical problem to be solved by the utility model is to overcome the ICP increase caused by early brain lesions, the regulation of cerebrospinal fluid and cerebral hemodynamics, so that the ICP increase is not large, so that direct ICP monitoring cannot sensitively reflect the changes of early lesions , and propose a non-contact magnetic induction intracranial pressure monitor.

The technical scheme that solves the above-mentioned technical problem is as follows:

A non-contact magnetic induction intracranial pressure monitor comprising an excitation source for generating an excitation signal and a reference signal; and

A magnetic induction detection device surrounding the measured head, the magnetic induction detection device is connected to the output end of the excitation source, the magnetic induction detection device generates an alternating excitation magnetic field signal according to the excitation signal provided by the excitation source, and the excitation magnetic field signal passes through the whole measuring the head, generating an eddy current in the head under test, and the eddy current generates a secondary magnetic field signal, and the excitation magnetic field signal and the secondary magnetic field signal are superimposed together to form a superimposed magnetic field signal with a phase change relative to the reference signal; and

A phase detector, the input end of the phase detector is respectively connected to the output end of the excitation source and the output end of the magnetic induction detection device, the phase detector detects the phase difference between the reference signal and the superimposed magnetic field signal, the The phase difference is used to reflect the pressure change produced by the cranial contents on the cranial cavity wall.

Adopting the above scheme, the non-contact magnetic induction intracranial pressure monitor of the present invention, through the excitation signal sent by an excitation source, makes the magnetic induction detection device generate an alternating excitation magnetic field signal, and the excitation magnetic field signal passes through the entire skull to be measured. The eddy current is generated in the skull under test, and the eddy current generates another magnetic field signal, which is called the secondary magnetic field signal. The original excitation magnetic field and the secondary magnetic field signal are superimposed together to form a superimposed magnetic field signal. This superimposed magnetic field signal is relative to the reference signal sent by the excitation source. (The phase of the reference signal and the phase of the excitation signal are the same, so it can replace the phase of the excitation signal), and a multi-frequency phase detector is used to detect the phase difference, which is consistent with the overall brain tissue conductance of the measured head. The conductivity of the whole brain tissue is directly proportional to the volume of lesions, cerebrospinal fluid and blood, and the intracranial volume directly affects the ICP (the pressure of the cranial contents on the wall of the cranial cavity). Therefore, the change of ICP can be reflected by detecting the phase difference between the superimposed magnetic field signal and the reference signal.

Although for early brain lesions, such as cerebral edema and cerebral hemorrhage, the cerebrospinal fluid and cerebral blood flow can adjust the intracranial pressure through compensatory effects, so that the increase in intracranial pressure is not large; but because the cranial cavity is rigid, when the contents of the cranial cavity When the volume increases to a critical point, the cerebrospinal fluid and cerebral blood flow can no longer be adjusted. At this time, a slight increase in the intracranial volume can cause a sharp increase in intracranial pressure, aggravate brain displacement and brain herniation, and lead to central failure crisis , which is very dangerous, and it is often too late for treatment at this time. Therefore, the intracranial pressure-volume relationship approximates an exponential curve, and the critical point range is usually 20–25 mmHg in adults and lower in children. It can be seen that when the intracranial pressure does not reach the critical point, detecting the change of the disease state has a high value for the judgment of the state of the disease. The current ICP detection method cannot detect the change of the intracranial lesion before the critical point, but the utility model can compare Sensitively reflect early lesions. Therefore, the non-contact magnetic induction intracranial pressure monitor of the present invention can reflect the change of the whole brain conductance caused by early lesion, regulation of cerebrospinal fluid and cerebral hemodynamics, so as to realize the monitoring of early lesion.

In addition, due to deep brain lesions, the adjustment of cerebrospinal fluid and cerebral blood flow changes according to the approximate cubic relationship of deep lesions, and has an additive effect with the lesion volume. The current ICP detection method is not sensitive to small deep brain lesions. The utility model can reflect the change of the overall brain conductance caused by small deep lesions and improve the sensitivity to deep brain lesions.

Further, the excitation source is a multi-frequency sinusoidal excitation source, the multi-frequency sinusoidal excitation source includes an input device for users to set the frequency and power, and a single-chip microcomputer connected to the output end of the input device, and sends out control instructions according to the signal provided by the input device ; and a field programmable gate array connected to the output terminal of the single-chip microcomputer, which generates a control timing signal after receiving the control command of the single-chip microcomputer; and a crystal oscillator which generates a clock frequency; and a phase-locked loop connected with the crystal oscillator, which multiplies the clock frequency signal output by the crystal oscillator Obtain the reference clock; and respectively connect the field programmable gate array and the phase-locked loop output to the direct digital frequency synthesizer, according to the control timing provided by the field programmable gate array and the reference clock provided by the phase-locked loop, generate user The set frequency and power signal; and the switch frequency selection filter connected to the output of the direct digital frequency synthesizer, which converts the frequency and power signal output by the direct digital frequency synthesizer into a reference signal output; and connected to the switch frequency selection filter The power amplifier and matcher at the output end of the filter amplifies and matches the reference signal output by the switch frequency selection filter as an excitation signal output. This multi-frequency sinusoidal excitation source uses a high-precision direct digital frequency synthesizer (DDS chip) and a powerful field-programmable gate array (FPGA chip) control and synchronization functions, so that the frequency stability of the output signal of this excitation source can be Reached 10 ^-8 , significantly higher than the signals used by other domestic units.

Furthermore, the multi-frequency sinusoidal excitation source is used to generate 200KHz, 1MHz, 10.7MHz, 21.4MHz, 30.85MHz, 40.05MHz, 49.95MHz, a total of 7 standard sinusoidal signals, and the output signal power adjustment range is: 10mW— 2W. The multi-frequency sinusoidal excitation source has the characteristics of multi-frequency output and high power regulation, which are also characteristics that other unit excitation source circuits do not have. Three sinusoidal excitation frequencies of 1MHz, 10.7MHz, and 21.4MHz were selected through experiments to meet the different requirements of clinical neurological and surgical disease monitoring, such as different types of cerebral hemorrhage, cerebral edema, and brain tumors.

Further, the excitation source includes a crystal oscillator generating a clock frequency; and a power divider connected to the output of the crystal oscillator, which divides the clock frequency generated by the crystal oscillator into a first clock frequency and a second clock frequency; and The first amplitude adjuster connected to the output end of the power divider adjusts the first clock frequency output by the power divider to become a reference signal; and the second amplitude adjuster connected to the output end of the power divider adjusts the second clock frequency output by the power divider. clock frequency; and a power amplifier connected to the output end of the second amplitude adjuster to amplify the output signal from the second amplitude adjuster to become an excitation signal.

Further, the magnetic induction detection device is composed of excitation coils and detection coils arranged at intervals, and the excitation coils and detection coils are fixed on the outer surface of the plexiglass sleeve so as to be parallel to each other and coaxial. Changes in the induced magnetic field caused by lesions in any part of the tested head can be detected, with high monitoring sensitivity, and ICP changes caused by 0.8ml hemorrhage in the rabbit's skull can be detected. The advantages of the magnetic induction detector of the present invention are: 1. Non-contact and non-invasive (the current ICP detection method needs to insert the sensor head into the brain). 2. High sensitivity, can detect ICP changes caused by a small amount of bleeding, and the detection results are correlated with ICP.

Further, the phase detector includes a first filter for pre-filtering the reference signal output by the excitation source; and a first programmable gain amplifier connected to the output end of the first filter for pre-filtering the reference signal according to user settings The gain of the digital programmable gain amplifier is adjusted to the input range of the A/D converter; and the second filter is used to pre-filter the superimposed magnetic field signal output by the magnetic induction detection device; and the first filter connected to the output end of the second filter Two programmable gain amplifiers, the pre-filtered superimposed magnetic field signal is adjusted to the input range of the A/D converter through the digital programmable gain amplifier according to the gain set by the user; and the first programmable gain amplifier and the second programmable gain amplifier respectively The A/D converter connected to the amplifier converts the first program-controlled gain amplifier and the second program-controlled gain amplifier into digital signals; synchronous acquisition of signals; and a field programmable gate array connected to the data collector to provide working timing for each part of the circuit and as an interface circuit; and a DSP connected to the field programmable gate array to complete the fast Fourier transform , to calculate the phase difference of the input two-way signal; and the synchronous dynamic random access memory connected to the DSP, when the DSP processes the data, the data is read from the SDRAM, and the fast Fourier transform is performed to obtain the phase difference data; and the display connected to the DSP , the phase difference data obtained by the DSP is sent to the monitor for real-time display, and the phase difference curve is drawn. The phase detector of the utility model adopts an independent DSP and a field programmable gate array (FPGA chip) to complete data collection and algorithm processing, and achieves the characteristics of high precision and miniaturization. The phase detector of the utility model can achieve a phase detection accuracy of 0.02°, completely reaching or exceeding foreign instruments, and has the characteristics of low cost and portability.

Furthermore, the phase detector also includes a clock module connected with the field programmable gate array, the synchronous clock provided by the field programmable gate array through the clock module provides the sampling clock for the data collector, and provides the data transmission clock for the DSP . In this way, a synchronous processing of the reference signal and the superimposed magnetic field signal is guaranteed.

Furthermore, the phase detector also includes an external flash memory connected to the DSP, and the 12-hour phase difference data is stored in the internal RAM of the DSP or the external flash memory. The DSP can store the collected real-time data in the external flash memory through the DMA bus. When the DSP processes the data, it reads the data from the external flash memory and performs fast Fourier transform to obtain the phase difference data.

Description of drawings

Fig. 1 is the circuit block diagram of the non-contact magnetic induction intracranial pressure monitor of the present utility model;

Fig. 2 is the circuit block diagram of the preferred embodiment of excitation source among Fig. 1;

Fig. 3 is the circuit block diagram of another embodiment of excitation source among Fig. 1;

Fig. 4 is the circuit block diagram of another embodiment of excitation source among Fig. 1;

Fig. 5 is a schematic structural view of a preferred embodiment of a magnetic induction detection device;

Fig. 6 is the circuit block diagram of the preferred embodiment of phase detector excitation among Fig. 1;

Fig. 7 is the corresponding relationship between the intracranial pressure and the magnetic induction phase displacement relationship curve obtained in animal experiments;

10 is an excitation source, 100 is a multi-frequency sinusoidal excitation source, 101 is an input device, 102 is a single-chip microcomputer, 103 is a field programmable gate array, 104 is a crystal oscillator, 105 is a phase-locked loop, 106 is a direct digital frequency synthesizer, 107 108 is a power amplifier and matching device, 109 is a display; 110 is a crystal oscillator, 111 is a power divider, 112 is a first amplitude regulator, 113 is a second amplitude regulator, and 114 is a power amplifier;

20 is a magnetic induction detection device, 200 is an excitation coil, and 201 is a detection coil;

300 is a first filter, 301 is a first programmable gain amplifier, 302 is a second filter, 303 is a second programmable gain amplifier, 304 is an A/D converter, 305 is a data collector, and 306 is a field programmable gate Array, 307 is a DSP, 308 is a synchronous dynamic random access memory, 309 is a display, 310 is a clock module, and 311 is an external flash memory.

Detailed ways

Referring to Fig. 1, the non-contact magnetic induction intracranial pressure monitor of the present invention is composed of an excitation source 10, a magnetic induction detection device 20 surrounding the tested skull and a phase detector 30, and each part is described in detail below:

1 and 2, an excitation source 10 is used to generate an excitation signal and a reference signal. The excitation source of the present utility model is preferably a multi-frequency sinusoidal excitation source 100, which is used to generate 200KHz, 1MHz, 10.7MHz, 21.4MHz, 30.85MHz, 40.05MHz, and a total of 7 standard sinusoidal signals of 49.95MHz , the output signal power adjustment range is: 10mW—2W, and the frequency stability of the signal reaches 10 ^-8 . The multi-frequency sinusoidal excitation source 100 includes an input device 101 for users to set the frequency and power. The input device 101 is a keyboard or a touch screen, and the input device in this embodiment is a keyboard. And the single-chip microcomputer 102 connected to the output end of the input device, the single-chip microcomputer 102 sends out control instructions according to the signal provided by the input device, and the single-chip microcomputer 102 controls the work of the whole multi-frequency sinusoidal excitation source with material. And a field programmable gate array (FPGA chip in FIG. 2 ) 103 connected to the output end of the single-chip microcomputer. The field programmable gate array 103 generates a control sequence signal after receiving a control command from the single-chip microcomputer. And a crystal oscillator 104 for generating a clock frequency. And a phase-locked loop (PLL chip in FIG. 2 ) 105 connected to the crystal oscillator, the phase-locked loop 105 multiplies the clock frequency signal output by the crystal oscillator to obtain a reference clock; the phase-locked loop 105 multiplies the 100MHz clock frequency output by the crystal oscillator , get the 800MHz clock frequency signal as the reference clock of the direct digital frequency synthesizer (DDS chip in Figure 2). And respectively connected to the direct digital frequency synthesizer 106 with the field programmable gate array 103 column and the output end of the phase locked loop 105, according to the control sequence provided by the field programmable gate array, and according to the reference clock provided by the phase locked loop, generate user Set the frequency and power signal. And the switch frequency selective filter 107 that is connected to the output port of the direct digital frequency synthesizer converts the frequency and power signal output by the direct digital frequency synthesizer into a reference signal output; The matching unit 108 amplifies and matches the reference signal output by the switch frequency selection filter and outputs it as an excitation signal. The multi-frequency sinusoidal excitation source also includes a display (LCD in FIG. 2 ) 109 connected to the output terminal of the single-chip microcomputer for displaying the frequency and power parameters currently set.

The working process of the above-mentioned multi-frequency sinusoidal excitation source circuit is: when the single-chip microcomputer 102 receives the command from the input device 101, on the one hand, it controls the field programmable gate array 103 to provide various control sequences for the direct digital frequency synthesizer 106. On the one hand, the currently set frequency and power parameters are output to the display 109 for display. The direct digital frequency synthesizer 106 generates the frequency and power output set by the user under the action of the 800MHz reference clock provided by the phase-locked loop 105 and the timing sequence controlled by the field programmable gate array 103 . The signal output by the direct digital frequency synthesizer 106 is filtered by a switch frequency selective filter to generate a reference signal. The reference signal is output as an excitation signal through a three-stage power amplifier circuit and a power matching circuit. This excitation source can finally output standard sinusoidal signals with 7 frequencies of 200KHz, 1MHz, 10.7MHz, 21.4MHz, 30.85MHz, 40.05MHz and 49.95MHz. The frequency stability of the signal reaches 10 ^-8 . The output excitation signal power adjustment range is: 10mW-2W. The amplitude of the reference signal at each frequency is fixed, and the phase difference between the reference signal and the excitation signal is fixed.

With reference to Fig. 1 and Fig. 3, the excitation source of the present utility model can also be the excitation source that crystal oscillator forms, and concrete structure is: described excitation source comprises the crystal oscillator 110 that produces clock frequency; And is connected to crystal oscillator output The power divider 111 at the terminal divides the clock frequency generated by the crystal oscillator into the first clock frequency and the second clock frequency; Road clock frequency becomes reference signal; And the second amplitude adjuster 113 that is connected to power splitter output end, adjusts the second road clock frequency of power splitter output; And the power amplifier 114 that is connected with the second amplitude adjuster output end, will come from The output signal of the second amplitude adjuster is amplified to become an excitation signal.

With reference to Fig. 1 and Fig. 4, the excitation source of the present utility model is not limited to above-mentioned embodiment, can also adopt the structure as shown in Fig. 4, the clock frequency signal that the crystal oscillator generates divides two-way output, one way adopts direct digital frequency synthesizer port as The basis of signal generation, the output signal is filtered by a filter, and then the reference signal is input after impedance transformation by the buffer amplifier. The other channel uses the direct digital frequency synthesizer port as the basis for signal generation, and the output signal is filtered by a filter, then impedance transformed by a buffer amplifier, and then amplified by a power amplifier to obtain an excitation signal.

Referring to FIG. 1 and FIG. 5 , the magnetic induction detection device 20 in the present invention is used to surround the head to be tested. The magnetic induction detection device 20 is connected to the output end of the excitation source 10, and the magnetic induction detection device generates an alternating excitation magnetic field signal according to the excitation signal provided by the excitation source, and the excitation magnetic field signal passes through the entire skull under test and generates The eddy current generates a secondary magnetic field signal, and the excitation magnetic field signal and the secondary magnetic field signal are superimposed to form a superimposed magnetic field signal with a phase change relative to the reference signal. The magnetic induction detection device is composed of excitation coils 200 and detection coils 201 arranged at intervals. The excitation coils 200 and detection coils 201 are fixed on the organic glass sleeve parallel to each other and coaxially (the organic glass sleeve is not shown in the figure) of the outer surface. Both the excitation coil and the detection coil are made of copper enameled wire. The diameter of the excitation coil and the detection coil is 10-30cm. The diameter of the two coils is preferably 25cm. The distance between the excitation coil and the detection coil is 6-9cm. The excitation coil The distance from the detection coil is preferably 8.5 cm, and there is an adjustable space of 5 cm up and down. The magnetic induction detection device 20 of the present utility model has higher monitoring sensitivity, and the rabbit is used as an experiment to detect the ICP change caused by 0.8ml bleeding in the rabbit's skull.

With reference to Fig. 1 and Fig. 6, phase detector 30 is multi-frequency phase detector, and the input end of phase detector 30 is connected with the output end of described excitation source 10 and the output end of described magnetic induction detection device 20 respectively, and phase detector The phase difference between the reference signal and the superimposed magnetic field signal is detected, and the phase difference is used to reflect the pressure change produced by the cranial content on the wall of the cranial cavity. The phase detector of the present invention preferably includes a first filter 300 for pre-filtering the reference signal output by the excitation source, and the first filter 300 is composed of a low-pass filter and a band-pass filter. And the first programmable gain amplifier 301 connected to the output end of the first filter, the pre-filtered reference signal is adjusted to the input range of the A/D converter through the digital programmable gain amplifier according to the gain set by the user. And the second filter 302 is used to pre-filter the superimposed magnetic field signal output by the magnetic induction detection device, and the second filter 302 is also composed of a low-pass filter and a band-pass filter. And the second programmable gain amplifier 303 connected to the output end of the second filter, the pre-filtered superimposed magnetic field signal is adjusted to the input range of the A/D converter through the digital programmable gain amplifier according to the gain set by the user. And the A/D converter 304 connected to the first programmable gain amplifier 301 and the second programmable gain amplifier 303 respectively, converts the signals from the first programmable gain amplifier and the second programmable gain amplifier into digital signals. And a data collector 305 connected with the A/D converter, which synchronously collects the two signals output by the A/D converter; and a field programmable gate array 306 connected with the data collector, which provides working timing for each part of the circuit And as an interface circuit; and a DSP307 connected to a field programmable gate array (FPGA chip in Figure 6) to complete the fast Fourier transform and calculate the phase difference between the two input signals. And the synchronous dynamic random access memory 308 connected with the DSP. When the DSP processes data, it reads the data from the synchronous dynamic random access memory (SDRAM chip in FIG. 6 ) 308, performs fast Fourier transform, and obtains the phase difference data. And the display 309 connected to the DSP, the phase difference data obtained by the DSP is sent to the display (LCD in FIG. 6 ) for real-time display, and the phase difference curve is drawn. The phase detector also includes a clock module 310 connected to the FPGA 306. The FPGA provides a synchronous clock through the clock module to provide a sampling clock for the data collector and a data transmission clock for the DSP. The phase detector also includes an external flash memory (Flash chip in FIG. 6 ) 311 connected to the DSP, and the 12-hour phase difference data is stored in the RAM inside the DSP or in the external flash memory. In addition, DSP can also output to personal computer through RS232 interface. The keyboard 312 is used to control the entire phase detector.

The reference signals and the superimposed magnetic field signals of the two input channels with the same frequency are pre-filtered through their respective filters. The pre-filtered signal is conditioned to be within the input range of the A/D converter via a digitally programmable gain amplifier according to a user-set gain. The two-way signals are collected synchronously by the data collector and sent to the field programmable gate array. The field programmable gate array sends the sampling digital signal to the DSP through the SPORT interface logic of the DSP, and the DSP performs fast Fourier transform to obtain the phase difference data. The DSP then sends the phase difference data to the monitor for real-time display, and draws a phase difference curve.

In addition, the phase detector 30 is not limited to the embodiment shown in FIG. 6 , and can also adopt a down-frequency lock-in amplifier method, an integrated phase detector chip, and software phase detector based on virtual instruments. The following are the introductions of these methods:

The down-frequency lock-in amplifier is a commonly used method. The signal of the detection coil is amplified by the differential amplifier, mixed with the signal close to the excitation frequency, and the high-frequency frequency is reduced to a certain low-frequency frequency through the frequency mixing. Buffer and amplify the input to the lock-in amplifier; the reference signal obtained from the excitation coil end is also input to the reference terminal of the lock-in amplifier after frequency reduction, low-pass filtering and buffer amplification; the detection signal and reference signal after frequency reduction pass through the lock-in amplifier, The real part and imaginary part of the detection signal are output, or converted and stored in the computer through the A/D converter, and the information representing the amplitude and phase can be calculated. When the lock-in amplifier works at a higher frequency, the phase drift tends to be large, and its internal frequent locking and synchronization processes limit the measurement speed of the system, and the internally synthesized reference signal of the lock-in amplifier is not completely synchronized with the external reference signal. In addition, the phase-locking method has a complex structure, a huge system, and inflexible measurement, which is not conducive to miniaturization. At present, lock-in amplifiers imported from abroad are mainly used for phase identification in China. Representative products include SR830 and SR844 lock-in amplifiers developed by Stanford Research Laboratory in the United States.

The current integrated phase detection chips include AD8302 and SYPD-1, etc. The phase difference resolution of AD8302 is only 0.5°, and the resolution of SYPD-1 is about 0.05°. When the amplitude of the input signal changes, the output signal drifts very large, so the phase difference chip The biggest problem is that the output signal is unstable.

Software phase identification is also called digital phase identification, which is a new development trend of current phase identification. After the detection signal is amplified by a low-noise narrow-band amplifier, frequency-selected by a crystal filter, and a high-gain narrow-band amplifier, it is converted into a digital signal by AD, and then the digital signal is demodulated by various processors to obtain the real part of the detection signal and The imaginary part, to obtain phase and magnitude information. The software phase identification method has higher precision and greater flexibility, but the cost of software phase identification using computers and virtual instruments increases, which is also not conducive to miniaturization.

The preferred phase detector of the utility model (the embodiment shown in Figure 6) takes into account the advantages and disadvantages of the above-mentioned phase detection method, and adopts independent DSP and FPGA chips to complete data acquisition and algorithm processing, achieving the characteristics of high precision and miniaturization . The phase detector can achieve a phase detection accuracy of 0.02°, completely reaching or exceeding foreign instruments, and has the characteristics of low cost and portability.

The utility model measures the changes of Magnetic Induction Phase Shift (MIPS) in the case of cerebral hemorrhage in 6 rabbits, and conducts a comparative study with intraventricular ICP monitoring. It mainly includes: multi-frequency sinusoidal excitation source, magnetic induction detection device, multi-frequency phase detector, rabbit station, physiological signal acquisition instrument and injection pump, etc.; the main parameters collected include MIPS, electrocardiographic signal (ECG), intraventricular ICP and arterial Pressure (APP), etc. Through the internal capsule hemorrhage model in rabbits, the corresponding relationship between intraventricular ICP monitoring and non-contact magnetic induction phase difference measurement was obtained, as shown in Figure 7. The main advantages of the non-contact magnetic induction ICP monitoring method of the utility model are: realize the non-contact and non-invasive monitoring of ICP; the sensitivity of early pathological changes is higher than that of traditional intraventricular ICP monitoring; solve severe brain trauma, skin diseases, skin allergies, and infectious diseases Patient's inability to stick contact electrodes.

Finally, compare the non-contact magnetic induction intracranial pressure monitor of the present invention with the patent of the Fourth Military Medical University (Patent No.: ZL200510042937.6), in terms of monitoring parameters, excitation detection methods, excitation methods, monitoring objects, scope of application, etc. Different aspects, specifically as follows: ① The patent of the Fourth Military Medical University obtains the distribution of the conductivity of the measured skull through local monitoring, and the utility model monitors the conductivity of the whole brain tissue of the measured skull; ② The patent of the Fourth Military Medical University adopts a multi-excitation detection coil structure , the utility model adopts a single excitation detection coil structure, and the diameter of the excitation detection coil is larger than the measured head diameter; ③ The Fourth Military Medical University patent adopts a single-frequency excitation method, and the utility model adopts a multi-frequency excitation method; ④ The Fourth Military Medical University patent monitoring The change of electrical conductivity distribution caused by cerebral edema, the utility model monitors the change of the overall cerebrospinal fluid and cerebral blood flow; ⑤ The patent of the Fourth Military Medical University is limited to the monitoring of cerebral edema, and the utility model is suitable for ICP monitoring of various common neurological and surgical diseases.

Claims (10)

1. A non-contact magnetic induction intracranial pressure monitor, characterized in that, includes an excitation source for generating an excitation signal and a reference signal; and A magnetic induction detection device surrounding the measured head, the magnetic induction detection device is connected to the output end of the excitation source, the magnetic induction detection device generates an alternating excitation magnetic field signal according to the excitation signal provided by the excitation source, and the excitation magnetic field signal passes through the whole measuring the head, generating an eddy current in the head under test, and the eddy current generates a secondary magnetic field signal, and the excitation magnetic field signal and the secondary magnetic field signal are superimposed together to form a superimposed magnetic field signal with a phase change relative to the reference signal; and A phase detector, the input end of the phase detector is respectively connected to the output end of the excitation source and the output end of the magnetic induction detection device, the phase detector detects the phase difference between the reference signal and the superimposed magnetic field signal, the The phase difference is used to reflect the pressure change produced by the cranial contents on the cranial cavity wall. 2. The non-contact magnetic induction type intracranial pressure monitor according to claim 1, wherein the excitation source is a multi-frequency sinusoidal excitation source, and the multi-frequency sinusoidal excitation source includes an input device for user setting frequency and power, as well as A single-chip microcomputer connected to the output terminal of the input device sends a control command according to a signal provided by the input device; and A field programmable gate array connected to the output terminal of the single-chip microcomputer generates a control timing signal after receiving a control command from the single-chip microcomputer; and a crystal oscillator that generates the clock frequency; and A phase-locked loop connected to the crystal oscillator, which multiplies the clock frequency signal output by the crystal oscillator to obtain a reference clock; and It is respectively connected to the field programmable gate array and the output terminal of the phase-locked loop to the direct digital frequency synthesizer, and according to the control sequence provided by the field programmable gate array and the reference clock provided by the phase-locked loop, the frequency and power signal; and A switch frequency selective filter connected to the output of the direct digital frequency synthesizer converts the frequency and power signal output by the direct digital frequency synthesizer into a reference signal output; and The power amplifier and matching device connected to the output end of the switch frequency selection filter amplifies and matches the reference signal output by the switch frequency selection filter as an excitation signal output. 3. The non-contact magnetic induction type intracranial pressure monitor according to claim 2, wherein said multi-frequency sinusoidal excitation source also includes a display connected to the output terminal of the single-chip microcomputer for displaying the frequency and power parameters. 4. The non-contact magnetic induction intracranial pressure monitor according to claim 2, wherein the multi-frequency sinusoidal excitation source is used to generate 200KHz, 1MHz, 10.7MHz, 21.4MHz, 30.85MHz, 40.05MHz, 49.95MHz The standard sinusoidal signal with 7 frequencies in MHz, the output signal power adjustment range is: 10mW-2W. 5. The non-contact magnetic induction intracranial pressure monitor according to claim 1, wherein the excitation source comprises a crystal oscillator generating a clock frequency; and a power divider connected to the output terminal of the crystal oscillator, and divides the clock frequency generated by the crystal oscillator into a first clock frequency and a second clock frequency; and A first amplitude adjuster connected to the output end of the power divider, adjusting the frequency of the first clock output by the power divider to become a reference signal; and A second amplitude adjuster connected to the output end of the power divider to adjust the frequency of the second clock output by the power divider; and The power amplifier connected to the output end of the second amplitude adjuster amplifies the output signal from the second amplitude adjuster to become an excitation signal. 6. The non-contact magnetic induction intracranial pressure monitor according to claim 1, wherein the magnetic induction detection device is composed of excitation coils and detection coils arranged at intervals, and the excitation coils and detection coils are parallel to each other and at the same time. The shaft is fixed on the outer surface of the plexiglass sleeve. 7. The non-contact magnetic induction type intracranial pressure monitor according to claim 5, wherein the excitation coil and the detection coil are all made of copper enameled wire, and the diameters of the excitation coil and the detection coil are 10-30cm, The distance between the excitation coil and the detection coil is 6-9cm. 8. The non-contact magnetic induction intracranial pressure monitor according to claim 1, wherein the phase detector includes a first filter for pre-filtering the reference signal output by the excitation source; and The first programmable gain amplifier connected to the output end of the first filter, the pre-filtered reference signal is adjusted to the input range of the A/D converter through the digital programmable gain amplifier according to the gain set by the user; and The second filter is used to pre-filter the superimposed magnetic field signal output by the magnetic induction detection device; and A second programmable gain amplifier connected to the output end of the second filter, the pre-filtered superimposed magnetic field signal is adjusted to the input range of the A/D converter through the digital programmable gain amplifier according to the gain set by the user; and A/D converters connected to the first programmable gain amplifier and the second programmable gain amplifier respectively, convert the signals from the first programmable gain amplifier and the second programmable gain amplifier into digital signals; and A data collector connected to the A/D converter, which simultaneously collects the two signals output by the A/D converter; and A field programmable gate array connected to the data collector provides working timing for each part of the circuit and serves as an interface circuit; and The DSP connected with the field programmable gate array is used to complete the fast Fourier transform and calculate the phase difference of the two input signals; and Synchronous DRAM connected with DSP, when DSP processes data, data is read out from SDRAM, and fast Fourier transform is carried out to obtain phase difference data; and The display connected to the DSP, the phase difference data obtained by the DSP is sent to the display for real-time display, and the phase difference curve is drawn. 9. The non-contact magnetic induction type intracranial pressure monitor according to claim 8, wherein the phase detector also includes a clock module connected with a field programmable gate array, and the field programmable gate array passes through the clock module The synchronous clock provided provides the sampling clock for the data collector and the data transmission clock for the DSP. 10. The non-contact magnetic induction type intracranial pressure monitor according to claim 8, characterized in that, the phase detector also includes an external flash memory connected with the DSP, and the phase difference data of 12 hours is stored in the internal RAM of the DSP or in external flash memory.

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