CN221013310U - Wearable ultrasonic Doppler blood flow monitoring system - Google Patents

Abstract

The utility model discloses a wearable ultrasonic Doppler blood flow monitoring system which comprises an ultrasonic sensor and a host, wherein the ultrasonic sensor comprises a pcb substrate, a plurality of groups of multi-array-element ultrasonic transducers and a flexible packaging layer, the pcb substrate is communicated with the host, each group of multi-array-element ultrasonic transducers comprises a plurality of ultrasonic transducers which are distributed at intervals and form different angles with the pcb substrate, and each group of multi-array-element ultrasonic transducers at least comprises an ultrasonic transducer Ux with an angle of zero degrees, and ultrasonic transducers Ua and ultrasonic transducers Ub which are positioned at two ends of the ultrasonic transducer Ux and distributed at intervals. The utility model can implement real-time monitoring of human blood flow information in a continuous Doppler mode and a pulse Doppler mode, can overcome the defects of large volume, high professional technical requirements, complex operation and the like of the traditional ultrasonic Doppler equipment, and has the advantages of simple structure, low cost, portability, convenience and the like.

Description

A wearable ultrasonic Doppler blood flow monitoring system

Technical Field

The utility model belongs to the field of medical equipment, and in particular relates to a wearable ultrasonic Doppler blood flow monitoring system.

Background technique

The Doppler index of blood flow has a very wide and important demand and value in clinical practice, and is an important indicator of many diseases and physiological characteristics. Ultrasonic Doppler and technology refers to the method of detecting the blood flow of moving organs and blood vessels using the principle of Doppler effect. It is also the most important means of obtaining blood flow Doppler in clinical practice. It is divided into continuous and pulsed Doppler according to the working state.

For continuous Doppler, it uses two ultrasonic transducers, one of which continuously emits ultrasonic waves and the other continuously receives echoes. This method has high velocity resolution and can detect very high-speed blood flow, which is its main advantage. However, its main disadvantage is the lack of distance resolution.

Pulse Doppler uses the same ultrasonic transducer to transmit and receive ultrasound. Due to the use of depth gating (or distance gating) technology, it can measure blood flow at a fixed point, so it has a high distance resolution and can also make an accurate analysis of the nature of blood flow at a fixed point. Since the maximum display frequency of pulse wave Doppler is limited by the pulse repetition frequency, aliasing is prone to occur when detecting high-speed blood flow.

At present, the ultrasonic Doppler systems used in clinical practice are mostly B-ultrasound trolleys. Although they can meet the needs of outpatient clinics in terms of clinical diagnosis, they have many limitations in real-time monitoring and home testing, and cannot meet some usage requirements that require long-term spans or frequent blood flow monitoring. Therefore, how to miniaturize ultrasonic Doppler detection equipment or even make it wearable to meet the needs of daily monitoring has become a hot topic in current research.

However, there are many existing wearable ultrasonic Doppler patents, and the most similar methods and devices are listed below: Application number: CN201820488946.0, Patent name: A wearable ultrasonic Doppler blood flow detector, the invention is divided into upper and lower limb detection. Application number: CN202111135992.5, Patent name: A wearable ultrasonic Doppler blood flow detector and detection method, the invention is a clothing-type wearable. Application number: KR1020070114541A, portable device for measuring blood flow, watch-style ultrasonic detection Doppler.

In summary, the shortcomings of ultrasonic Doppler blood flow detection equipment are: 1. The equipment is large and expensive; 2. It requires clinical professional medical staff to operate and cannot be used at home; 3. It cannot be worn for long-term monitoring; 4. It cannot perform pulse Doppler and continuous Doppler detection at the same time; 5. There is no blood pressure information.

Summary of the invention

The technical problem to be solved by the utility model is to overcome the deficiencies of the prior art and provide an improved wearable ultrasonic Doppler blood flow monitoring system.

The ultrasonic Doppler blood flow monitoring system of the utility model embeds multiple groups of specifically arranged ultrasonic transducers into a flexible substrate to form a flexible and adherent wearable probe, as well as a special processing system, so that the system equipment can perform both pulse Doppler detection and continuous Doppler detection. It also has the characteristics of miniaturization and wearability, and can monitor human blood flow information including flow velocity, blood flow pulsation index and blood pressure in real time, meeting the needs of multi-scenario applications.

In order to solve the above technical problems, the utility model adopts the following technical solutions: a wearable ultrasonic Doppler blood flow monitoring system, which includes an ultrasonic sensor and a host, the ultrasonic sensor includes a long and flexible PCB substrate, a plurality of groups of multi-element ultrasonic transducers spaced apart on the PCB substrate, and a flexible packaging layer encapsulated on the surface of the plurality of groups of multi-element ultrasonic transducers and capable of fitting the skin, wherein the PCB substrate is connected to the host, each group of multi-element ultrasonic transducers includes a plurality of ultrasonic transducers spaced apart and forming different angles with the PCB substrate, each group of multi-element ultrasonic transducers includes at least one ultrasonic transducer Ux with an angle of zero degrees, ultrasonic transducers Ua and ultrasonic transducers Ub located at both ends of the ultrasonic transducer Ux and spaced apart, wherein the ultrasonic transducer Ux can transmit and receive ultrasonic waves, and one of the ultrasonic transducers Ua and the ultrasonic transducer Ub transmits ultrasonic waves, and the other receives ultrasonic waves.

Preferably, each group of multi-element ultrasonic transducers includes ultrasonic transducers U1, U2, U3, U4, and U5 distributed in sequence, wherein U3 is an ultrasonic transducer Ux located in the middle and with an angle of zero degrees, the two ultrasonic transducers Ua are U1 and U2, and the two ultrasonic transducers Ub are U4 and U5. In other words, each group of transducers for detection is composed of 5 transducers, and the 5 transducers form a fixed angle with the bottom PCB circuit, θ0, θ1, 0, θ2, θ3.

Furthermore, the angles formed by each group of ultrasonic transducers U1, U2, U3, U4, U5 and the PCB substrate are the same.

According to a specific implementation and preferred aspect of the utility model, the backing layer of each ultrasonic transducer is a conductor, a pad with positive and negative electrodes is formed on the PCB substrate, the conductor is connected to the pad through a conductive adhesive or a conductive wedge block and is connected to the negative electrode of the pad, the positive electrode of the ultrasonic transducer is connected to the positive electrode of the pad through a conductive line, and one end of the PCB substrate forms a connector end, which is connected to the host. This facilitates the circuit conduction installation of the ultrasonic transducer.

The backing layer is a conductive material, such as silver glue, etc. Or the low-frequency transducer has no backing. The working layer material of the transducer is plated with gold, silver, aluminum and other electrodes on both sides.

Preferably, the conductive glue is silver glue.

Each transducer is connected to the flexible PCB circuit board at the bottom, and the host's selection module can control which specific transducers are working.

The negative electrode (conductive backing) of the transducer is directly adhered to the negative pad of the PCB substrate through conductive glue. In order to control the size and structure of the circuit, all the negative pads are turned on to form a common ground circuit, and then the positive electrode of the transducer is connected to the positive pad of the PCB substrate by bonding wire/gold wire welding. At one end of the PCB substrate, all the electrode pads form a connector end and are connected to the host system through the connector end. In particular, in order to improve the performance of flexible bending, the wires in the PCB substrate are bent or serpentine.

The plurality of groups of multi-element ultrasonic transducers are arranged in a linear array or a planar array. That is, the entire flexible probe is composed of a plurality of such transducer groups, and the transducers in the probe can be arranged in a linear array or a planar array.

Preferably, the ultrasonic transducer can be a piezoelectric ultrasonic transducer, a piezoelectric composite ultrasonic probe, a capacitive ultrasonic probe or a thin film ultrasonic probe, and the operating frequency range can be 1MHz~15MHz, and the outer diameter size is between 0.1mm~2mm. In other words, the ultrasonic transducer used can be a piezoelectric ultrasonic transducer such as PZT/PMN-PT, a piezoelectric composite ultrasonic probe such as 1-3 piezoelectric composite, a capacitive ultrasonic probe such as CMUT, a thin film ultrasonic probe such as PVDF/AlN, etc.

In this example, the five transducers in each group of ultrasonic probes that make up the flexible ultrasonic sensor have the same operating center frequency, but the operating center frequencies of transducers in different groups can be different, depending on the requirements for monitoring target depth, resolution, and sensitivity.

According to another specific implementation and preferred aspect of the utility model, the flexible packaging layer is hydrogel, silica gel, rubber or tape. After the transducer is bonded to the PCB circuit board, the adhesive is integrally injected. The adhesive mainly plays the role of protecting the transducer and the PCB circuit, and adhering to the human skin.

That is to say, the flexible packaging layer can not only protect the ultrasonic transducer and the circuit of the flexible PCB board, but also adhere to the object to be detected. In this case, PDMS, polydimethylsiloxane (PDMS), is used. It is a kind of organic silicon. Because of its low cost, simple use, good adhesion with silicon wafers, and good chemical inertness, it has become a polymer material widely used in fields such as microfluidics.

In addition, the host includes a high-voltage pulse excitation module, a gating circuit, a receiving unit, a control unit and a display unit, wherein the gating circuit is connected to the PCB substrate, and the gating circuit has at least two selected paths. The gating circuit mainly realizes the gating of the working transducer, thereby reducing the complexity of the system, and it is not necessary to equip each transducer with a separate excitation and receiving circuit. In order to ensure the detection needs of continuous pulse Doppler, at least two transducers must be able to work simultaneously.

Preferably, the display unit includes a display module, an information processing module and an information transmission module, wherein the information transmission module is connected to the user terminal via wired or/and wireless communication. That is, the information transmission module can be a module with wireless transmission such as wifi, Bluetooth, etc., or a mobile battery module to conveniently transmit the collected and processed data to the user terminal.

The high-voltage pulse amplitude generated by the high-voltage pulse excitation module is 20~600V, and the pulse width is less than 10us. In this way, the generated high-voltage pulse excitation voltage drives the ultrasonic probe to work.

The receiving unit mainly realizes low-noise amplification, filtering, gain and sampling of the echo signal. It is mainly composed of a low-noise amplifier LNA, a bandpass filter, an adjustable gain TGC and an analog-to-digital conversion chip ADC.

The control unit mainly controls the work of each part, including the on-off status of each channel of the selection switch, the timing of the excitation circuit, the gain of the TGC, the processing of the echo signal such as Fourier transform, etc. In order to be portable and miniaturized, it is mainly composed of a single-chip microcomputer.

In addition, in order to enable portable wear and data viewing, wireless transmission such as WiFi, Bluetooth, etc. and mobile battery modules can be added to the host system to conveniently transmit the collected and processed data to the terminal.

The user terminal is connected to the information transmission module by wired or wireless means, and its main functions include post-processing, displaying and alarming data. The user terminal can be a smart phone, tablet computer, mobile computer and smart TV, etc.

Due to the implementation of the above technical solution, the utility model has the following advantages compared with the prior art:

The utility model utilizes wearable multi-element flexible ultrasonic sensors and Doppler technology to implement real-time monitoring of human blood flow information in continuous Doppler mode and pulsed Doppler mode, which can overcome the shortcomings of existing ultrasonic Doppler equipment such as large size, high professional and technical requirements, and complex operation. At the same time, it has many advantages such as simple structure, low cost, portable wearability, convenience, and is expected to be applied in clinical and personal monitoring fields.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic front view of a wearable ultrasonic Doppler blood flow monitoring system of the present invention;

FIG2 is an enlarged schematic diagram of the structure of the host in FIG1 ;

FIG3 is an enlarged schematic diagram of the structure of the ultrasonic sensor in FIG1 ;

Wherein: 1. host; 10. high-voltage pulse excitation module; 11. selection circuit; 12. receiving unit; 13. control unit; 14. display unit; 140. display module; 141. information processing module; 142. information transmission module; 2. ultrasonic sensor; 20. PCB substrate; 20a. connector end; 21. multi-element ultrasonic transducer; 210. ultrasonic transducer; 22. flexible packaging layer; P. skin; X. blood vessel; Y. user terminal.

Detailed ways

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

In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present utility model, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

In the present invention, unless otherwise clearly specified and limited, the terms "install", "connect", "connect", "fix" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

In the utility model, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are for illustrative purposes only and are not intended to be the only implementation method.

As shown in FIG. 1 , the wearable ultrasonic Doppler blood flow monitoring system according to this embodiment includes a host 1 and an ultrasonic sensor 2 .

As shown in FIG. 2 , the host 1 is of a conventional structure, which mainly includes a high-voltage pulse excitation module 10 , a gating circuit 11 , a receiving unit 12 , a control unit 13 and a display unit 14 .

The high-voltage pulse amplitude generated by the high-voltage pulse excitation module 10 is 20-600V, and the pulse width is less than 10us. In this way, the generated high-voltage pulse excitation voltage drives the ultrasonic probe to work.

The gating circuit 11 mainly realizes the gating of the working ultrasonic transducer, thereby reducing the complexity of the system. It is not necessary to equip each ultrasonic transducer with a separate excitation and receiving circuit. In order to ensure the detection needs of continuous pulse Doppler, the gating circuit 11 selects at least two transducers to work simultaneously.

The receiving unit 12 mainly realizes low-noise amplification, filtering, gain and sampling of the echo signal, and is mainly composed of a low-noise amplifier LNA, a bandpass filter, an adjustable gain TGC and an analog-to-digital conversion chip ADC.

The control unit 13 mainly controls the operation of each part, including the on/off state of each channel of the selection switch, the timing of the excitation circuit, the gain of the TGC, the processing of the echo signal such as Fourier transform, etc. For portability and miniaturization, it is mainly composed of a single-chip microcomputer.

The display unit 14 includes a display module 140 , an information processing module 141 and an information transmission module 142 , wherein the information transmission module 142 is connected to the user terminal Y via wired or/and wireless communication.

That is to say, the information transmission module can be added with wireless transmission such as WiFi, Bluetooth, etc., and a mobile battery module to conveniently transmit the collected and processed data to the user terminal.

The user terminal Y is connected to the information transmission module by wired and wireless means, and its main functions include post-processing, displaying and alarming data. The user terminal can be a smart phone, tablet computer, mobile computer and smart TV.

As shown in Figure 3, the ultrasonic sensor 2 includes a long and flexible PCB substrate 20, a plurality of groups of multi-element ultrasonic transducers 21 spaced apart on the PCB substrate 20, and a flexible packaging layer 22 encapsulated on the surface of the plurality of groups of multi-element ultrasonic transducers 21 and capable of adhering to the skin.

The PCB substrate 20 is connected to the gating circuit 11 , and each group of multi-element ultrasonic transducers 21 includes a plurality of ultrasonic transducers 210 which are distributed at intervals and have different angles with the PCB substrate 20 .

Each group of multi-element ultrasonic transducers 21 includes at least one ultrasonic transducer Ux with an angle of zero degrees, ultrasonic transducers Ua and Ub located at both ends of the ultrasonic transducer Ux and spaced apart, wherein the ultrasonic transducer Ux can transmit and receive ultrasonic waves, and one of the ultrasonic transducer Ua and the ultrasonic transducer Ub transmits ultrasonic waves, and the other receives ultrasonic waves.

Specifically, each group of multi-element ultrasonic transducers includes ultrasonic transducers U1, U2, U3, U4, and U5 distributed in sequence, where U3 is an ultrasonic transducer Ux located in the middle and with an angle of zero degrees, the two ultrasonic transducers Ua are U1 and U2, and the two ultrasonic transducers Ub are U4 and U5. In other words, each group of detected transducers consists of 5 transducers, and the 5 transducers form a fixed angle with the bottom PCB circuit, θ0, θ1, 0, θ2, θ3.

The angle formed by each group of ultrasonic transducers U1, U2, U3, U4, U5 and the PCB substrate is the same.

The backing layer of each ultrasonic transducer 210 is a conductor, and a pad with positive and negative electrodes is formed on the PCB substrate 20. The conductor is connected to the pad through a conductive adhesive or a conductive wedge block and communicates with the negative electrode of the pad. The positive electrode of the ultrasonic transducer 210 is communicated with the positive electrode of the pad through a conductive line, and one end of the PCB substrate 20 forms a connector end 20a, which is connected to the gating circuit 11. This facilitates the circuit conduction installation of the ultrasonic transducer.

The backing layer is a conductive material, such as silver glue, etc. Or the low-frequency transducer has no backing. The working layer material of the transducer is plated with gold, silver, aluminum and other electrodes on both sides.

The conductive glue is silver glue.

Each ultrasonic transducer 210 is connected to the flexible PCB circuit board at the bottom, and the host's selection module can control which specific transducers are working.

The negative electrode (conductive backing) of the ultrasonic transducer is directly bonded to the negative electrode pad of the PCB substrate through conductive glue. In order to control the size and structure of the circuit, all the negative electrode pads are turned on to form a common ground circuit, and then the positive electrode of the transducer is connected to the positive electrode pad of the PCB substrate by bonding wire/gold wire welding. At one end of the PCB substrate, all the electrode pads form a connector end and are connected to the host system through the connector end. In particular, in order to improve the performance of flexible bending, the wires in the PCB substrate are bent or serpentine.

The multiple groups of multi-element ultrasonic transducers 21 are arranged in a linear array or a planar array. That is, the entire flexible probe is composed of several groups of such transducer groups, and the transducers in the probe can be arranged in a linear array or a planar array.

The ultrasonic transducer 210 may be a piezoelectric ultrasonic transducer, a piezoelectric composite ultrasonic probe, a capacitive ultrasonic probe or a thin film ultrasonic probe, and the operating frequency range may be 1 MHz to 15 MHz, and the outer diameter may be between 0.1 mm and 2 mm. In other words, the ultrasonic transducer used may be a piezoelectric ultrasonic transducer such as PZT/PMN-PT, a piezoelectric composite ultrasonic probe such as 1-3 piezoelectric composite, a capacitive ultrasonic probe such as CMUT, a thin film ultrasonic probe such as PVDF/AlN, etc.

In this example, the five transducers in each group of ultrasonic probes (ultrasonic transducers) that make up the flexible ultrasonic sensor 2 have the same operating center frequency, but the operating center frequencies of transducers in different groups may be different, depending on the requirements for monitoring target depth, resolution, and sensitivity.

The flexible packaging layer 22 is a hydrogel, a silicone, a rubber or an adhesive tape. After the transducer is bonded to the PCB, the whole is filled with an adhesive body. The adhesive body mainly protects the transducer and the PCB circuit, and adheres to the human skin.

That is to say, the flexible packaging layer can not only protect the ultrasonic transducer and the circuit of the flexible PCB board, but also adhere to the object to be detected. In this case, PDMS, polydimethylsiloxane (PDMS), is used. It is a kind of organic silicon. Because of its low cost, simple use, good adhesion with silicon wafers, and good chemical inertness, it has become a polymer material widely used in fields such as microfluidics.

The working process of the blood flow monitoring system of this embodiment is as follows (taking a group of multi-element ultrasonic transducers as an example):

When working, first, the multi-element flexible ultrasonic sensor is tightly attached to the surface of human skin, the flexible probe is connected to the host, the host is started, and the probe connection and communication with the terminal are confirmed to be normal according to the host status; secondly, the host quickly excites each transducer group in turn through the internal selection switch to receive the echo signal; finally, the ultrasonic transducer U3 works in the pulse Doppler mode, and after excitation, it receives the echo signal by itself. After data reception, it is Fourier transformed to obtain its center frequency, and combined with the ultrasonic transducers U1, U2, U4, and U5 working in the continuous Doppler mode, each of which has an angle of θ ₀ , θ ₁ , θ ₂ , and θ ₃ , where transducers U1 and U2 transmit ultrasonic waves, and transducers U4 and U5 receive ultrasonic waves, thereby obtaining the blood flow velocity.

In addition, according to this method, by monitoring the flow velocities Vd and Vs of the blood vessels during diastole and systole, the pulsation index PI can also be obtained: PI=(Vs-Vd)/((Vs-Vd)/3+Vd).

It is worth noting that in theory, only two angle values are needed for detection, but in order to obtain a more sensitive detection angle, the project still sets 4 different transducer angles for each group. The functions of transducers U1, U2 and transducers U4, U5 can also be reversed, with transducers U4 and U5 transmitting ultrasonic waves and transducers U1 and U2 receiving ultrasonic waves.

Furthermore, since the blood flow velocity v and the outer diameter d (diameter) of the blood vessel (obtained by the upper and lower blood vessel wall envelope signals of the echo signal) can be obtained, assuming that the blood density ρ is a known quantity, the blood pressure can be expressed as:

P=ρV ² /2+C , where C is a constant that can be obtained through calibration using blood pressure measured by a third party.

In summary, this embodiment has the following advantages:

1. By using wearable multi-element flexible ultrasonic sensors and Doppler technology, it is possible to implement real-time monitoring of Doppler information, pulsation index and blood pressure of human blood flow in continuous Doppler mode and pulsed Doppler mode. It is also possible to set warning values on the terminal, issue alarms, and remotely remind medical staff and family members in emergency situations, thus overcoming the shortcomings of existing ultrasonic Doppler equipment, such as large size, high professional and technical requirements, and complex operation;

2. It has many advantages, such as simple structure, low cost, portable and wearable, convenient and easy to use, and is expected to be used in clinical and personal monitoring fields;

3. The gating circuit does not need to equip each ultrasonic transducer with a separate excitation and receiving circuit, thereby reducing the complexity of the system;

4. The flexible packaging layer mainly protects the transducer and PCB circuit, and adheres to the human skin.

The above detailed description of the utility model is intended to enable people familiar with the technology in this field to understand the content of the utility model and implement it. It is not intended to limit the protection scope of the utility model. All equivalent changes or modifications made according to the spirit of the utility model should be included in the protection scope of the utility model.

Claims (10)

1. A wearable ultrasonic Doppler blood flow monitoring system, comprising an ultrasonic sensor and a host, characterized in that: the ultrasonic sensor comprises a long and flexible PCB substrate, a plurality of groups of multi-element ultrasonic transducers spaced apart on the PCB substrate, and a flexible packaging layer encapsulated on the surface of the plurality of groups of the multi-element ultrasonic transducers and capable of fitting the skin, wherein the PCB substrate is connected to the host, each group of the multi-element ultrasonic transducers comprises a plurality of ultrasonic transducers spaced apart and forming different angles with the PCB substrate, each group of the multi-element ultrasonic transducers comprises at least one ultrasonic transducer Ux with an angle of zero degree, ultrasonic transducers Ua and ultrasonic transducers Ub located at both ends of the ultrasonic transducer Ux and spaced apart, wherein the ultrasonic transducer Ux can transmit and receive ultrasonic waves, and one of the ultrasonic transducers Ua and Ub transmits ultrasonic waves and the other receives ultrasonic waves. 2. The wearable ultrasonic Doppler blood flow monitoring system according to claim 1 is characterized in that: each group of the multi-element ultrasonic transducers includes ultrasonic transducers U1, U2, U3, U4, and U5 distributed in sequence, wherein U3 is an ultrasonic transducer Ux located in the middle and with an angle of zero degrees, the two ultrasonic transducers Ua are U1 and U2 respectively, and the two ultrasonic transducers Ub are U4 and U5 respectively. 3. The wearable ultrasonic Doppler blood flow monitoring system according to claim 2, characterized in that the angles formed by each group of ultrasonic transducers U1, U2, U3, U4, U5 and the PCB substrate are the same. 4. The wearable ultrasonic Doppler blood flow monitoring system according to claim 3 is characterized in that: the backing layer of each ultrasonic transducer is a conductor, a pad with positive and negative electrodes is formed on the PCB substrate, the conductor is connected to the pad through a conductive glue or a conductive wedge block and is connected to the negative electrode of the pad, the positive electrode of the ultrasonic transducer is connected to the positive electrode of the pad through a conductive line, and one end of the PCB substrate forms a connector end, and the connector end is connected to the host. 5. The wearable ultrasonic Doppler blood flow monitoring system according to claim 4, characterized in that the backing layer is a conductive material or an electrode plated with gold, silver or aluminum. 6. The wearable ultrasonic Doppler blood flow monitoring system according to claim 1, characterized in that: the multiple groups of multi-element ultrasonic transducers are arranged in a linear array or a planar array. 7. The wearable ultrasonic Doppler blood flow monitoring system according to claim 1 is characterized in that: the ultrasonic transducer can be a piezoelectric ultrasonic transducer, a piezoelectric composite ultrasonic probe, a capacitive ultrasonic probe or a thin film ultrasonic probe, and the operating frequency range of the ultrasonic transducer can be 1MHz to 15MHz, wherein the ultrasonic transducers of each group of the multi-element ultrasonic transducers have the same operating center frequency; the outer diameter of the ultrasonic transducer is between 0.1mm and 2mm. 8. The wearable ultrasonic Doppler blood flow monitoring system according to claim 1, wherein the flexible packaging layer is hydrogel, silica gel, rubber or tape. 9. The wearable ultrasonic Doppler blood flow monitoring system according to claim 1 is characterized in that: the host includes a high-voltage pulse excitation module, a gating circuit, a receiving unit, a control unit and a display unit, wherein the gating circuit is connected to the PCB substrate, and the number of paths selected by the gating circuit is at least two. 10. The wearable ultrasonic Doppler blood flow monitoring system according to claim 9 is characterized in that: the display unit includes a display module, an information processing module and an information transmission module, wherein the information transmission module is connected to the user terminal via wired or/and wireless communication; the high-voltage pulse amplitude generated by the high-voltage pulse excitation module is 20 to 600 V, and the pulse width is less than 10 us.