An intracranial pressure sensor

Abstract

This invention relates to a novel intracranial pressure sensor, comprising a pressure-sensitive element, a reflector, an optical fiber assembly, a processing unit, etc. The intracranial pressure sensor of this invention uses ultrasound to determine the position of the reflector, providing ultrasound time-of-flight information. When the reflector position changes, the time-of-flight of the reflected ultrasound signal changes significantly. Two-channel photoresistors are directly combined with optical fibers to form a complete system capable of measuring the optical flux of both channels. Pre-testing of the sensor's photoresistors using precision impedance analysis ensures accurate measurement of the changes in optical flux between the two optical fibers caused by the reflector position change. The monitor monitors the feedback signals of the differential optical signal and the ultrasound time-of-flight, performing airway balance control and issuing alarm signals to achieve accurate and stable measurement of the patient's intracranial pressure, thus fulfilling the monitoring purpose.

Description

Technical Field

[0001] This invention relates to the field of medical multi-parameter monitors, and in particular to an intracranial pressure sensor that simultaneously uses ultrasound signals and fiber optic signals as control balance signals. Background Technology

[0002] Existing intracranial pressure monitors use implanted fiber optic probes as sensors to detect pressure within and outside the dura mater, in the subarachnoid space via lumbar puncture, and at the anterior fontanelle in infants. The fiber optic probe uses optical sensing information and optical fiber as the transmission medium. During monitoring, the intracranial pressure sensed by the probe is converted into a differential optical signal and transmitted to the monitor. The monitor uses an internal pressure balancing system to increase or decrease pressure within the fiber optic probe to maintain pressure balance with the external environment. Intracranial pressure is indirectly obtained by measuring the pressure in the internal airway system. Pressure-balanced intracranial pressure measurement features high sensitivity, good stability, and reliable physiological safety.

[0003] These fiber optic intracranial pressure probe sensors also have many problems: a. Due to the nonlinearity and different response times of photoresistors, conventional pairing and matching are not easy; b. The pressure sensor inside the sensor is made of a reflector with a reed structure, and it is difficult to meet the technical requirements for the roughness of the reflective surface of the reflector. The reflective surface of the light spot is too small, and the two light fluxes are inconsistent, resulting in too large a dispersion of light flux between the two channels; c. The fiber optic cable is prone to breakage, which can easily cause false differential light signals, causing the airway system to fail to reach a balanced state. This can lead to loss of control and imbalance during the inflation and deflation process, resulting in failure of intracranial pressure monitoring. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention provides an intracranial pressure sensor, comprising:

[0005] Pressure sensitive element 10, the pressure sensitive element 10 has a cavity 9 inside, and a column 8 is vertically installed inside the cavity 9;

[0006] The reflector 6 is mounted on the column 8 by a spring 7. The spring 7 enables the reflector 6 to deflect around the mounting point under external pressure, and one end of the spring 7 is also provided with a force sensing strip 18.

[0007] An optical sensing module having an optical fiber group 19 pointing to the reflector 6 for detecting changes in light flux caused by the deflection of the reflector 6;

[0008] An ultrasonic positioning module is used to detect the ultrasonic echo time difference signal caused by the displacement of the reflector 6. It includes an ultrasonic transducer 4 and an ultrasonic transducer 5. The ultrasonic transducer 4 and the ultrasonic transducer 5 are respectively positioned on the upper and lower sides of the reflector 6's motion path, facing the reflector 6's reflective surface. When the reflector 6 is in its initial equilibrium position, the acoustic paths between the ultrasonic transducer 4 and the ultrasonic transducer 5 and the reflector 6's reflective surface are equal.

[0009] The processing unit is used to receive and process the signals from the optical sensing module and the ultrasonic positioning module, and output control signals for airway balance control and / or alarm based on the light flux change signal and the ultrasonic echo time difference signal.

[0010] In one embodiment of the present invention, the processing unit includes a two-channel ultrasonic transceiver unit 11, a two-channel ultrasonic transceiver unit 2 12, a light-emitting diode unit 13, a receiving photoresistor unit 14, and a receiving photoresistor unit 2 15 integrated on a PCB.

[0011] In one embodiment of the present invention, the optical fiber group 19 is composed of receiving optical fiber 1, transmitting optical fiber 2, and receiving optical fiber 3, and receiving optical fiber 1, transmitting optical fiber 2, and receiving optical fiber 3 are wrapped in the same optical fiber cable.

[0012] In one embodiment of the present invention, the two-channel ultrasonic transceiver unit 11 and the two-channel ultrasonic transceiver unit 12 are respectively connected to ultrasonic transducers 4 and 5, and the receiving photoresistor unit 14 and the receiving photoresistor unit 15 are respectively connected to receiving optical fiber 1 and receiving optical fiber 3.

[0013] Compared with the prior art, the above-mentioned technical solution of the present invention has the following advantages: The intracranial pressure sensor of the present invention uses ultrasound to determine the position of the reflector and provides ultrasound time difference information. When the position of the reflector changes, the time difference of the reflected ultrasound signal changes significantly. The two-channel photoresistors are directly combined with optical fibers to form a complete system that can test the optical flux information of the two channels. The photoresistors of the sensor are tested in advance using precision impedance analysis to accurately test the change in optical flux of the two optical fibers caused by the change in the position of the reflector. The monitor monitors the feedback signals of the differential optical signal and the ultrasound time difference, performs airway balance control and issues alarm signals, so as to achieve accurate and stable testing of the patient's intracranial pressure and realize the monitoring purpose. Attached Figure Description

[0014] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0015] Figure 1This is a schematic diagram of the internal structure of the intracranial pressure sensor of the present invention;

[0016] Figure 2 This is a schematic diagram illustrating the working principle of the intracranial pressure sensor described in this invention.

[0017] As shown in the figure: 1. Receiving fiber optic cable 1, 2. Transmitting fiber optic cable, 3. Receiving fiber optic cable 2, 4. Ultrasonic transducer 1, 5. Ultrasonic transducer 2, 6. Reflector, 7. Reed, 8. Column, 9. Cavity, 10. Pressure sensitive element, 11. Two-channel ultrasonic transceiver unit 1, 12. Two-channel ultrasonic transceiver unit 2, 13. Light-emitting diode unit, 14. Receiving photoresistor unit 1, 15. Receiving photoresistor unit 2, 16. Air passage, 17. Eight-pin socket, 18. Force sensing strip, 19. Fiber optic cable group. Detailed Implementation

[0018] like Figure 1 As shown, this embodiment provides an intracranial pressure sensor, including:

[0019] Pressure sensitive element 10, the pressure sensitive element 10 has a cavity 9 inside, and a column 8 is vertically installed inside the cavity 9;

[0020] The reflector 6 is mounted on the column 8 by a spring 7. The spring 7 enables the reflector 6 to deflect around the mounting point under external pressure, and one end of the spring 7 is also provided with a force sensing strip 18.

[0021] An optical sensing module has an optical fiber group 19 pointing towards the reflector 6; an ultrasonic positioning module includes an ultrasonic transducer 4 mounted above the optical fiber group 19 and an ultrasonic transducer 5 mounted below the optical fiber group 19, and the other end of the optical fiber group 19 is connected to a matching processing unit.

[0022] The processing unit includes a two-channel ultrasonic transceiver unit 11, a two-channel ultrasonic transceiver unit 2 12, a light-emitting diode unit 13, a receiving photoresistor unit 14, and a receiving photoresistor unit 2 15, all integrated on a single PCB.

[0023] In addition, the pressure-sensitive element 10 is equipped with an eight-pin socket 17 at its end. The optical fiber group 19 consists of receiving optical fiber 1, transmitting optical fiber 2, and receiving optical fiber 3, which are all wrapped in the same optical fiber cable.

[0024] Furthermore, the two-channel ultrasonic transceiver unit 11 and the two-channel ultrasonic transceiver unit 12 are respectively connected to ultrasonic transducer 4 and ultrasonic transducer 5, and the receiving photoresistor unit 14 and the receiving photoresistor unit 15 are respectively connected to receiving optical fiber 1 and receiving optical fiber 3.

[0025] like Figure 2 As shown, the working principle of this device is as follows: Ultrasonic transducer 4 emits an ultrasonic signal to the reflective plate. Due to the smooth and flat reflective plate, the reflected signal is transmitted to ultrasonic transducer 4. Ultrasonic transducer 5 emits an ultrasonic signal to the reflective plate, and the reflected ultrasonic signal is transmitted to ultrasonic transducer 5. When the original reflector is in its initial position, ultrasonic transducers 4 and 5 receive the first ultrasonic echo signal simultaneously. When the sensor receives external pressure, it is transmitted to the reed-loaded reflector. There is a time difference between the ultrasonic echo received by ultrasonic transducers 4 and 5. After receiving the ultrasonic signal, the monitor adjusts the airway inflation or deflation according to the time difference, so that the ultrasonic echoes arrive simultaneously. The equilibrium pressure at this time is the intracranial pressure received by the sensor. Since the ultrasonic waves propagate in the air at this time, they will not be transmitted to the outside of the sensor and will not produce any temperature rise effect. The special miniature ultrasonic transducer design ensures that the reflected ultrasonic echo signal is clean and free of noise, which is also the key to ensuring successful positioning.

[0026] like Figure 1 As shown, the sensor employs multiple ultrasonic transducers and fiber optic sensors to detect pressure within and outside the dura mater, in the subarachnoid space during lumbar puncture, and at the anterior fontanelle of the infant. The fiber optic sensor transmits optical sensing information about the position of the internal pressure sensor, while the ultrasonic transducers simultaneously transmit ultrasonic positioning signals of the pressure sensor. These multiple signals are simultaneously transmitted to the monitor, which adjusts its internal pressure balancing system based on these signals. This involves venting or inflating the airway to adjust the sensor's position and maintain pressure balance with the external environment. Intracranial pressure is indirectly obtained by measuring the pressure within the internal airway system. The simultaneous use of multiple differential optical signals and ultrasonic positioning signals significantly improves system reliability and stability, achieving precise monitoring.

[0027] like Figure 1 As shown, two miniature ultrasonic transducers are characterized by an operating frequency greater than MHz, a size greater than 1 mm, and the ability to transmit and receive independently or by another party. The working distance between the sensor and the ultrasonic transducer is greater than 5 mm (depending on the operating frequency). The monitor receives the electrical signal based on the first ultrasonic echo, using pulse transmission to avoid standing waves and ensure accurate positioning.

[0028] And such as Figure 1 As shown, the intracranial pressure sensor's end is housed within a photoresistor array. The photoresistors employ a three-parameter pairing method: dark resistance, maximum operating resistance at equilibrium, and minimum operating resistance at equilibrium. Pairing is performed beforehand, and successfully paired photoresistors are installed on the same sensor. This ensures consistent optical throughput between the two fiber optic channels.

[0029] When the sensor receives external pressure, the reed-loaded reflector inside the sensor rotates due to the pressure. The fiber optic assembly receives varying amounts of light flux, which are transmitted through the fiber to the photoresistor. The photoresistor changes position, and this change is transmitted to the control unit via an operational amplifier. The control unit uses these signals to control the airway inflation and deflation, adjusting the reflector position. This process is repeated until the reflector returns to its original position, maintaining balance. At this point, the internal airway pressure is the pressure experienced by the sensor, i.e., intracranial pressure. Due to the nonlinearity of the photoresistor, the reflected light flux from the sensor may be inconsistent, potentially leading to a certain degree of imbalance.

[0030] When external pressure is applied and transmitted to the pressure-sensitive element 10, it surges through the column 8, lifting or lowering the reflector 6. The ultrasonic transducers 1 and 2 receive ultrasonic signals and changes in optical flux. The ultrasonic signals are transmitted to the subsequent receivers, and the position change of the reflector is determined based on the change in reception time. The optical fibers 1 and 2 transmit the signals to the photoresistor units 14 and 25, respectively. The position change is also determined based on the change in photoresistor resistance. The system controller, based on these changes, performs inflation and deflation to achieve a zero-adjustment state for both ultrasonic and optical flux signals. These two signals simultaneously control the balance within the airway, greatly enhancing system reliability and achieving precise monitoring of intracranial pressure. The system is equipped with an eight-pin socket 17 at its end.

[0031] The embodiments of the present invention also provide calculations and examples:

[0032] The miniature ultrasonic transducer, with a working frequency of 5MHz and a wavelength of 0.068mm, is used in conjunction with a circular transducer with an outer diameter of 1mm, an opening angle of 4.8°, a working distance of 5mm, and a reflector distance variation of 0.005mm. This corresponds to a first ultrasonic echo time difference of 0.029μs, which can fully achieve the purpose of precise positioning.

[0033] A three-parameter photoresistor was selected to test the differences in its channel system under atmospheric pressure. The results are as follows:

[0034]

[0035] Using the three-parameter method to pair photoresistors can ensure that the two light fluxes are consistent. Under pressure conditions, it can provide an accurate differential signal. The monitor uses this signal to control the airway for inflation and deflation, thereby achieving internal airway balance and monitoring intracranial pressure.

[0036] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. An intracranial pressure sensor, characterized in that... include: The pressure-sensitive element (10) has a cavity (9) inside, and a column (8) is vertically installed inside the cavity (9). A reflector (6) is mounted on the column (8) by a spring (7). The spring (7) enables the reflector (6) to deflect around the mounting point under external pressure. A force sensing strip (18) is also provided at one end of the spring (7). An optical sensing module having an optical fiber group (19) pointing to the reflector (6) for detecting the change in light flux caused by the deflection of the reflector (6); An ultrasonic positioning module is used to detect the ultrasonic echo time difference signal caused by the displacement of the reflector (6). It includes an ultrasonic transducer one (4) and an ultrasonic transducer two (5). The ultrasonic transducer one (4) and the ultrasonic transducer two (5) are respectively positioned on the upper and lower sides of the reflector (6) on its motion path, facing the reflector surface. When the reflector (6) is in the initial equilibrium position, the sound path between the ultrasonic transducer one (4) and the ultrasonic transducer two (5) and the reflector surface of the reflector (6) is equal. The processing unit is used to receive and process the signals from the optical sensing module and the ultrasonic positioning module, and output control signals for airway balance control and / or alarm based on the light flux change signal and the ultrasonic echo time difference signal.

2. The intracranial pressure sensor according to claim 1, characterized in that: The processing unit includes a two-channel ultrasonic transceiver unit 1 (11), a two-channel ultrasonic transceiver unit 2 (12), a light-emitting diode unit (13), a receiving photoresistor unit 1 (14), and a receiving photoresistor unit 2 (15) integrated on a PCB.

3. The intracranial pressure sensor according to claim 1, characterized in that: The optical fiber group (19) consists of receiving optical fiber one (1), transmitting optical fiber (2), and receiving optical fiber two (3), and receiving optical fiber one (1), transmitting optical fiber (2), and receiving optical fiber two (3) are wrapped in the same optical fiber cable.

4. The intracranial pressure sensor according to claim 2, characterized in that: The two-channel ultrasonic transceiver unit 1 (11) and the two-channel ultrasonic transceiver unit 2 (12) are respectively connected to the ultrasonic transducer 1 (4) and the ultrasonic transducer 2 (5), and the receiving photoresistor unit 1 (14) and the receiving photoresistor unit 2 (15) are respectively connected to the receiving optical fiber 1 (1) and the receiving optical fiber 2 (3).

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