Optical fiber probe and blood pressure monitoring system

Abstract

The present invention relates to an optical fiber probe and a blood pressure monitoring system. The optical fiber probe comprises: a sleeve having a free end and a connection end and n F-P sensors contained in the sleeve for pressure measurement, n being greater than or equal to 2, the F-P sensor comprising an F-P cavity and two multimode optical fibers, the F-P cavity being formed between the two multimode optical fibers, the cavity lengths of each F-P cavity being different, the multimode optical fibers being connected by thin-diameter optical fibers, the diameter of the multimode optical fibers being greater than the diameter of the thin-diameter optical fibers, the F-P sensors being sequentially cascaded in the sleeve from small to large according to the cavity lengths along the direction from the free end of the sleeve to the connection end. The present invention cascades a plurality of F-P sensors at different axial positions of the probe, so that blood pressure measurements at different positions can be obtained by only one measurement, and the operation is simple and fast.

Description

Technical Field

[0001] The present invention relates to the field of medical device technology, and in particular to a fiber optic probe and a blood pressure monitoring system. Background Art

[0002] Blood enters the heart through two main coronary arteries and passes through a network of blood vessels on the surface of the heart muscle to provide nutrients to the heart. Cholesterol and fat are deposited in the arteries. Lipid deposition and inflammatory reactions lead to stenosis or occlusion of the vascular lumen, causing myocardial ischemia and angina pectoris. After years of technological development, the coronary artery blood flow reserve fraction (FFR) has been recognized by more and more people as an invasive functional evaluation indicator of lesions. FFR is defined as the ratio of the maximum blood flow provided to the myocardium of the innervated area by the epicardial stenotic coronary artery to the maximum blood flow provided to the myocardium by the same coronary artery when it is normal. It is simplified as the ratio of the mean pressure in the stenotic distal coronary artery (Pd) under the state of maximum myocardial hyperemia to the mean pressure in the aorta at the coronary artery orifice (Pa).

[0003] Existing blood pressure monitoring methods mainly use electrical sensors for monitoring, but such products have some problems and inconveniences in use. On the one hand, electrical sensors are susceptible to electromagnetic interference, making it difficult to network when using multi-point measurements; on the other hand, due to their large size, it is difficult to enter the human blood vessels for measurement, which in turn limits the timely processing of signals and their sensitivity.

[0004] Fiber optic pressure sensors are widely used in the medical field due to their small size, high sensitivity, strong anti-electromagnetic interference ability, and in some cases, biocompatibility and convenience of aseptic operation. Common fiber optic sensors can usually only measure the pressure at a certain point, and sometimes multiple measurements are required to achieve pressure measurement, which is very inconvenient to operate. Summary of the invention

[0005] In order to overcome the problems existing in the related art, this specification provides a fiber optic probe and a blood pressure monitoring system.

[0006] According to a first aspect of an embodiment of the present specification, there is provided an optical fiber probe, comprising: a sleeve having a free end and a connecting end, and n FP sensors contained in the sleeve for pressure measurement, wherein n is greater than or equal to 2, the FP sensor comprising an FP cavity and two multimode optical fibers, the FP cavity being formed between the two multimode optical fibers, the cavity length of each FP cavity being different, the multimode optical fibers being connected by thin-diameter optical fibers, the diameter of the multimode optical fibers being greater than the diameter of the thin-diameter optical fibers, and the FP sensors being cascaded in sequence in the sleeve from small to large according to the cavity length along the direction from the free end of the sleeve to the connecting end.

[0007] Furthermore, n is equal to 3, and the cavity lengths of the three FP cavities form a geometric progression with 3 as a common ratio.

[0008] Furthermore, the shortest FP cavity has a cavity length of 60 μm.

[0009] Furthermore, at least one FP sensor is disposed at a central position of the casing, and at least one FP sensor is disposed at an eccentric position of the casing.

[0010] Furthermore, along the axial direction of the sleeve, the spacing between adjacent FP sensors is equal, and the spacing is greater than or equal to 1 cm and less than or equal to 3 cm.

[0011] Furthermore, the FP sensor is further provided with a polydimethylsiloxane cladding on the outer periphery of the thin-diameter optical fiber, and the polydimethylsiloxane cladding fills the FP cavity.

[0012] Furthermore, the diameter of the polydimethylsiloxane cladding is greater than the diameter of the multimode optical fiber, and both axial ends of the polydimethylsiloxane cladding at least partially wrap the outer peripheral surface of the multimode optical fiber.

[0013] Furthermore, it also includes a fiber Bragg grating cascaded with the FP sensor, and the length of the fiber Bragg grating is greater than or equal to 7 mm and less than or equal to 12 mm.

[0014] Furthermore, the FP sensors along the free end to the connection end of the sleeve are respectively the first to the nth FP sensors, and the end of the fiber Bragg grating close to the free end of the sleeve is cascaded to the nth FP sensor.

[0015] According to the second aspect of the embodiments of this specification, a blood pressure monitoring system is provided, comprising: a circulator, a broadband light source, a spectrum acquisition module, a computer device, and the fiber optic probe, wherein the fiber optic probe is connected to the circulator via an optical fiber, and the circulator is also connected to a broadband light source providing a light source and a spectrum acquisition module receiving reflected spectral information via optical fibers, respectively, and the spectrum acquisition module transmits the spectral information to the computer device, and the computer device demodulates the spectral information.

[0016] The technical solutions provided by the embodiments of this specification may have the following beneficial effects:

[0017] A plurality of FP sensors are cascaded at different axial positions inside the probe for measuring blood pressure, so that blood pressure measurements at different positions can be obtained through only one measurement, and the operation is simple and fast.

[0018] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a structural schematic diagram of a blood pressure monitoring system according to an embodiment of the present invention;

[0020] Figure 2 is a schematic diagram of the structure of an optical fiber probe according to an embodiment of the present invention;

[0021] Figure 3 yes Figure 2 Structural diagram of the FP sensor.

[0022] Reference numerals:

[0023] 1. Broadband light source; 2. Optical fiber; 3. Circulator; 4. Optical fiber probe; 41. FP sensor; 411. Thin-diameter optical fiber; 4111. Thin-diameter optical fiber core; 4112. Thin-diameter optical fiber cladding; 412. Multimode optical fiber; 4121. Multimode optical fiber core; 4122. Multimode optical fiber cladding; 413. PDMS cladding; 42. Sleeve; 43. FBG; 44. Single-mode optical fiber; 441. Single-mode optical fiber core; 442. Single-mode optical fiber cladding; 5. Spectrum acquisition module; 6. Computer equipment. DETAILED DESCRIPTION

[0024] Figure 2 This is a schematic diagram of the internal structure of an optical fiber probe according to an embodiment of the present invention, and the figure is not drawn to scale. Figure 2 As shown, the present invention discloses a fiber optic probe 4. Since the optical fiber itself is very small, it is particularly suitable for measuring blood vessel pressure with wounds. A sleeve 42 is provided on the outside of the fiber optic probe 4 to support and protect the internal sensor unit. The material of the sleeve 42 can be selected from biocompatible materials, such as polyimide materials. The sleeve 42 is a slender circular tube as a whole, including a free end and a connecting end connected to the device. Inside the sleeve 42, n pressure sensing units are sequentially arranged from the free end to the connecting end, where n is greater than or equal to 2. The n pressure sensing units are cascaded to form a pressure measurement component of the fiber optic probe 4, which is used to measure blood pressure values ​​at different positions in the blood vessel. The n pressure sensing units are all optical fiber Fabry-Perot (FP) sensors, that is, n FP sensors 41, such as Figure 2 As shown in the dotted box. The n FP sensors 41 are arranged from the free end to the connection end of the sleeve 42, which are the first to the nth FP sensors 41, respectively. The n FP sensors 41 are connected to each other by optical fibers, and the optical fibers can be single-mode optical fibers 44 with low cost and low fusion loss. The sleeve 42 has a channel for blood to pass through, and the blood transmits the pressure to the n FP sensors 41 through the channel.

[0025] A fiber Bragg grating (FBG) is also provided inside the sleeve 42 for temperature compensation. The FBG 43 can be provided at any position in the sleeve 42, that is, it can be located at the front end of the first FP sensor 41, at the rear end of the nth FP sensor, or between any two FP sensors 41. Figure 2 As shown in the embodiment, as a preference, the FGB 43 is cascaded behind the nth FP sensor 41 , that is, one end of the FGB 43 close to the free end of the sleeve 42 is connected to the nth FP sensor 41 .

[0026] The n FP sensors 41 and the FBG 43 are connected to each other through a single-mode optical fiber 44 (including: an internal single-mode optical fiber core 441 and an external single-mode optical fiber cladding 442). The outer diameter of the single-mode optical fiber 44 is equal to the outer diameter of the multi-mode optical fiber 412. The n FP sensors 41 are separated by a certain distance along the axial direction of the sleeve 42, and the distance is preferably 1~3cm. Such an arrangement can not only realize blood pressure measurement at different positions, but also avoid the problem that the overall length of the optical fiber probe 4 is too long, causing difficulty in use. In addition, the axial spacing between two adjacent FP sensors 41 is preferably equal spacing, and the spacing is greater than or equal to 1cm and less than or equal to 3cm. Due to the spacing between the n FP sensors 41, the blood pressure points measured by the n FP sensors 41 are different, so that the blood pressure values ​​of multiple locations can be measured at one time.

[0027] As described above, n FP sensors 41 can be arranged at a certain distance along the axis direction of the cannula 42 to measure the blood pressure values ​​at different positions along the length direction of the blood vessel. In order to measure the blood pressure values ​​at different positions in the cross section of the blood vessel, the FP sensors 41 can also be arranged at different radial positions of the cannula 42, such as: the cross-sectional center position or eccentric position of the cannula 42. Figure 2 As shown, in this embodiment, the number of FP sensors 41 is 3, wherein the first FP sensor 41 close to the free end is arranged at the center position of the sleeve 42, and the second and third FP sensors 41 are arranged eccentrically. In other embodiments, the first FP sensor 41 can also be arranged at an eccentric position, while the second and third FP sensors 41 are arranged at the center position. The radial position setting of the n FP sensors 41 can be designed according to requirements. The FP sensor 41 arranged at the eccentric position can be arranged on the inner surface of the sleeve 42 by bonding or other fixing methods. With such a design, the FP sensor 41 located at the center of the sleeve 42 can measure the blood pressure at the center position of the blood vessel, while the FP sensor 41 at the eccentric position can measure the blood pressure at the blood vessel wall.

[0028] The FP sensor 41 is developed from the optical Fabry-Perot interferometer. Its core sensitive element is the FP cavity, which can be used to detect physical parameters such as pressure, temperature, vibration, acceleration, etc. A FP cavity is usually composed of two optical plates with a certain reflectivity and strictly parallel. The sensor of this structure can be attached to the surface of the object to be measured. When the physical quantity such as external pressure or strain changes, it will cause the sensor FP cavity length to change, and the output optical signal parameters will also change accordingly. By demodulating the FP cavity length information in the returned interference light signal, the monitoring of the changes in physical parameters such as pressure or strain in the monitoring environment can be realized.

[0029] like Figure 2 and Figure 3 As shown, the FP sensor 41 includes: an FP cavity, two sections of multimode optical fiber 412 (including: an internal multimode optical fiber core 4121 and an external multimode optical fiber cladding 4122) and a section of thin-diameter optical fiber 411 (including: an internal thin-diameter optical fiber core 4111 and an external thin-diameter optical fiber cladding 4112), wherein the multimode optical fiber 412 is located at both ends of the sensor, forming an FP cavity in the middle, and the thin-diameter optical fiber 411 is located in the FP cavity, and its diameter is smaller than that of the multimode optical fiber 412, and is used to connect the multimode optical fibers 412 at both ends. In order to better measure the blood pressure value at a certain position in the blood vessel, the cavity length direction of the FP cavity is parallel to the axial direction of the cannula 42. Blood flows through the inside of the cannula 42 and contacts the multimode optical fiber 412 of the FP sensor 41. The FP cavity is squeezed by pressure, resulting in a change in the cavity length.

[0030] In order to enhance the sensitivity of the FP sensor 41, a layer of polydimethylsiloxane (PDMS) porous material may be wrapped around the outer periphery of the thin-diameter optical fiber 411. PDMS is an organic silicon polymer that has good compatibility with human tissue and is widely used in the biomedical field.

[0031] like Figure 2As shown, the pressure measurement is performed using n FP sensors 41, where n is 3. Each FP sensor 41 unit includes: an FP cavity, a thin-diameter optical fiber 411, a multimode optical fiber 412, and a PDMS cladding 413, wherein the multimode optical fiber 412 acts as a coupler. The incident light is input from the single-mode optical fiber 44, and after passing through the multimode optical fiber 412, since the core diameter of the multimode optical fiber 412 is larger than the diameter of the thin-diameter optical fiber 411, one path of light is coupled to the thin-diameter optical fiber 411 for transmission, and the other path of light is coupled to the PDMS cladding 413 for transmission. The two beams of light are then coupled and output to the single-mode optical fiber 44 through the multimode optical fiber 412. Due to the particularity of PDMS, a porous material, it is very sensitive to changes in pressure. When the pressure changes, the rate of change of the refractive index of the PDMS material will be much greater than the rate of change of the refractive index of the air, thereby causing the pressure sensitivity of the FP sensor to be greatly improved, achieving the effect of pressure sensitization.

[0032] In order to make the PDMS material better wrap the thin-diameter optical fiber 411, the thin-diameter optical fiber 411 with multimode optical fibers 412 fused at both ends can be placed in a capillary with an inner diameter of 400μm, and then PDMS liquid is dripped at one end of the capillary. At this time, under the capillary action, the PDMS liquid will quickly fill the capillary, and then the PDMS liquid will wrap the thin-diameter optical fiber 411. Then, it is placed on a heating table for curing at a temperature of 100°C for 1 hour, and finally a PDMS cladding 413 is formed.

[0033] Through the above method, the PDMS material can be wrapped into the external space of the thin-diameter optical fiber 411 to fill the entire FP cavity. The diameter of the wrapped PDMS cladding 413 is higher than the diameter of the multi-mode optical fiber 412 on both sides, and the PDMS cladding 413 at both ends along the axial direction at least partially wraps the outer peripheral surface of the multi-mode optical fiber 412, so that the integrity of the FP sensor 41 is stronger and the PDMS cladding 413 is not easy to fall off.

[0034] For the FP sensor 41, the pressure change will cause the FP cavity length to change, and the cavity length change will cause the peak of the interference spectrum to change. Therefore, by solving the detection peak, the pressure value can be obtained. Figure 1 , Figure 2As shown, the signal collected by the spectrum acquisition module 5 includes the signals of n FP sensors 41. Therefore, before spectrum demodulation, the signals of the n FP sensors 41 must first be separated. Specifically, the original spectrum signal collected by the spectrum acquisition module 5 is first subjected to a fast Fourier transform to obtain the spectrum information of the original spectrum. Since the cavity lengths of the n FP sensors 41 are all different, different frequency components can be formed in the spectrum diagram, and then the signals of the n FP sensors 41 are distinguished by using an FIR filter. In this process, the greater the difference in the cavity length of the FP sensor 41, the better the signal separation effect. However, due to the limitation of the use length of the probe itself, the setting of the cavity length is not always the larger the better. In the actual design process, the cavity length can be designed according to the number of FP sensors 41 and the length of the probe 4.

[0035] Preferably, the short cavity is placed at the front end of the free end of the sleeve 42 as much as possible, that is, n FP sensors are cascaded in order from small to large according to the cavity length along the direction from the free end of the sleeve to the connection end. Because the long cavity is placed at the front end, it is easy to weaken the spectral intensity, which is not conducive to spectral analysis. In one embodiment, the number of FP sensors 41 is set to 3, and the first FP sensor, the second FP sensor and the third FP sensor are respectively located along the free end of the sleeve 42 to the connection end. In order to better distinguish the signals of the three FP sensors 41, the cavity lengths of the three FP sensors 41 can be set to a geometric progression with 3 as a common ratio. Specifically, the cavity length of the first FP sensor: the cavity length of the second FP sensor: the cavity length of the third FP sensor is equal to 1:3:9. At this time, the signal separation effect is good, and the length of the optical fiber probe 4 is moderate. In addition, in this embodiment, the shortest cavity length of the three FP sensors 41 is set to 60μm, at which time the spectral signal fringe contrast is optimal, the envelope period is most obvious, and the signal is easiest to separate.

[0036] For the FP sensor 41, changes in temperature and pressure will cause spectral drift. Since PDMS is a material with a high thermo-optical coefficient, if this material is set on the FP sensor 41, the sensor's sensitivity to temperature will increase, resulting in greater temperature crosstalk. In order to reduce the impact of temperature changes on the accuracy of the pressure probe, an FBG 43 is also provided on the optical fiber probe 4. The FBG 43 is very sensitive to temperature and strain. The central reflection wavelength of the FBG 43 will drift with changes in the surrounding temperature, and this drift is proportional to the temperature change. By cascading the FBG 43 to the optical fiber probe 4 with the FP sensor 41, the temperature sensitivity of the FBG 43 can be used to monitor and compensate for changes caused by temperature, thereby improving the accuracy of pressure measurement. The length of the FBG 43 can be customized according to actual application needs, and the length range is preferably 7 to 12 mm, including the end value.

[0037] like Figure 1 As shown, the present invention discloses a blood pressure monitoring system for measuring blood pressure values ​​at different positions in a blood vessel. The system includes an optical fiber probe 4, a connecting end of the optical fiber probe 4 is connected to an optical fiber 2, the other end of the optical fiber 2 is connected to a circulator 3, and the circulator 3 is also connected to a broadband light source 1 and a spectrum acquisition module 5 through two other optical fibers 2, wherein the spectrum acquisition module 5 is connected to a computer device 6. In the system, the optical fiber 2 is an ordinary optical fiber, which is used for spectral signal transmission. The specific working process of the monitoring system is that the light emitted by the broadband light source 1 is transmitted to the optical fiber probe 4 after passing through the circulator 3, and the reflected interference spectrum is collected by the spectrum acquisition module 5 through the optical fiber 2 and the circulator 3, and the continuous spectrum signal is converted into a discrete digital electrical signal, and then demodulated on the demodulation software of the computer device 6 to obtain the cavity length information of the sensor, and then the pressure information is obtained. The demodulation software uses the global optimal MMSE fast signal demodulation method. First, the spectrum is demodulated using the fast Fourier transform method to calculate the rough value of the cavity length of the FP sensor 41. Then, a series of virtual cavity length values ​​and their corresponding interference spectra are constructed with a preset step size within the specified virtual cavity length simulation range, and the mean square error between them and the actual spectrum is calculated to obtain the virtual cavity length value corresponding to the minimum mean square error, and the optimal cavity length value that meets the requirements is obtained. Finally, the cavity length value is associated with the pressure value.

Claims

1. An optical fiber probe, comprising: A sleeve having a free end and a connection end, and n FP sensors for pressure measurement contained in the sleeve, n being greater than or equal to 2, characterized in that the FP sensor comprises an FP cavity and two multimode optical fibers, the FP cavity is formed between the two multimode optical fibers, the cavity lengths of each FP cavity are different, the multimode optical fibers are connected by thin-diameter optical fibers, the diameter of the multimode optical fibers is greater than the diameter of the thin-diameter optical fibers, and the FP sensors are cascaded in the sleeve in order from small to large according to the cavity lengths along the direction from the free end of the sleeve to the connection end; The FP sensor is further provided with a polydimethylsiloxane cladding on the outer periphery of the thin-diameter optical fiber, and the polydimethylsiloxane cladding fills the FP cavity.

2. The optical fiber probe according to claim 1, characterized in that n is equal to 3, and the cavity lengths of the three FP cavities form a geometric progression with 3 as a common ratio.

3. The optical fiber probe according to claim 2, characterized in that: The shortest FP cavity has a cavity length of 60 μm.

4. The optical fiber probe according to claim 1, characterized in that At least one FP sensor is disposed at the center of the casing, and at least one FP sensor is disposed at an eccentric position of the casing.

5. The optical fiber probe according to claim 1, characterized in that: Along the axial direction of the sleeve, the spacing between adjacent FP sensors is equal, and the spacing is greater than or equal to 1 cm and less than or equal to 3 cm.

6. The optical fiber probe according to claim 1, characterized in that: The diameter of the polydimethylsiloxane cladding is greater than the diameter of the multimode optical fiber, and both axial ends of the polydimethylsiloxane cladding at least partially wrap the outer peripheral surface of the multimode optical fiber.

7. The optical fiber probe according to claim 6, characterized in that: It also includes a fiber Bragg grating cascaded with the FP sensor, wherein the length of the fiber Bragg grating is greater than or equal to 7 mm and less than or equal to 12 mm.

8. The optical fiber probe according to claim 7, characterized in that: The FP sensors along the free end to the connection end of the casing are respectively the first to the nth FP sensors, and one end of the fiber Bragg grating close to the free end of the casing is cascaded to the nth FP sensor.

9. A blood pressure monitoring system, characterized in that: include: A circulator, a broadband light source, a spectrum acquisition module, a computer device, and the optical fiber probe according to any one of claims 1 to 8, wherein the optical fiber probe is connected to the circulator via an optical fiber, and the circulator is also connected to a broadband light source providing a light source and a spectrum acquisition module receiving reflected spectrum information via optical fibers, respectively, and the spectrum acquisition module transmits the spectrum information to the computer device, and the computer device demodulates the spectrum information.

Images