Method for determining blood flow velocity and Doppler blood flow detection device

Abstract

An embodiment of the present application provides a method for determining blood flow velocity and a Doppler blood flow detection device, wherein the method comprises: obtaining an emission angle, which is the angle between the direction in which a signal is emitted by a transmitting element in the Doppler blood flow detection device and the direction in which blood flow moves in a blood vessel to be detected; obtaining the distance between a transmitting element and a receiving element in the Doppler blood flow detection device and the distance between the transmitting element and the blood vessel to be detected; determining a receiving angle according to the emission angle, the distance between the transmitting element and the receiving element, and the distance between the transmitting element and the blood vessel to be detected, wherein the receiving angle is the angle between the direction in which a signal is received by a receiving element in the Doppler blood flow detection device and the direction in which blood flow moves; determining a blood flow velocity measurement value according to the emission angle and the receiving angle; in this way, a more accurate blood flow velocity measurement value can be obtained.

Description

Technical Field

[0001] The invention relates to the field of medical detection, and in particular to a method for determining blood flow velocity and a Doppler blood flow detection device. Background Art

[0002] With the development of science and technology, medical testing methods can be used to obtain relevant parameters of the human body to help doctors diagnose various diseases. Among them, blood flow velocity is an important physiological parameter, and many diseases can be reflected in the blood flow velocity.

[0003] The basic principle of using Doppler technology to detect blood flow velocity is that the ultrasonic probe emits ultrasonic waves of a certain intensity. When the ultrasonic waves encounter moving blood, the wavelength of the ultrasonic waves is greater than the diameter of the red blood cells in the blood, and the ultrasonic waves will be scattered when encountering the red blood cells. At the same time, because the red blood cells are moving, the scattered echo signals undergo Doppler frequency shift. The greater the speed, the greater the frequency shift. By analyzing the frequency shift in the echo signal and combining it with the mathematical formula of Doppler technology, the movement speed of the red blood cells can be calculated.

[0004] At present, the use of Doppler blood flow detection devices to detect blood flow velocity of patients has been widely used in clinical practice. However, in actual use, there are often certain errors in the measurement results, especially when the medical staff's operation is not standard, or when the patient moves during long-term monitoring, the error of the measurement result will be greater, which leads to a reduction in the reference value of the blood flow velocity measurement results. In severe cases, it may cause medical staff to misjudge the patient's condition. Summary of the invention

[0005] In view of this, the embodiments of the present application provide a method for determining blood flow velocity and a Doppler blood flow detection device to solve at least one problem existing in the background technology.

[0006] In a first aspect, an embodiment of the present application provides a method for determining blood flow velocity, which is applied to a Doppler blood flow detection device, and the method includes:

[0007] Acquire the emission angle, which is the angle between the direction of the emission signal of the transmitting chip in the Doppler blood flow detection device and the direction of blood flow movement in the blood vessel to be detected;

[0008] Acquire the distance between the transmitting chip and the receiving chip in the Doppler blood flow detection device and the distance between the transmitting chip and the blood vessel to be detected;

[0009] The receiving angle is determined according to the transmitting angle, the distance between the transmitting chip and the receiving chip, and the distance between the transmitting chip and the blood vessel to be detected. The receiving angle is the angle between the direction in which the receiving chip receives the signal in the Doppler blood flow detection device and the direction of blood flow movement;

[0010] The blood flow velocity measurement is determined based on the transmission angle and the reception angle.

[0011] Optionally, the distance between the transmitting chip and the blood vessel to be detected includes a first distance, and the first distance is the distance from the transmitting chip to the blood vessel to be detected along the direction in which the transmitting chip transmits the signal;

[0012] The receiving angle is determined according to the transmitting angle, the distance between the transmitting chip and the receiving chip, and the distance between the transmitting chip and the blood vessel to be detected, including using the following formula to determine the receiving angle:

[0013] |β-α|=arctan(D / L); wherein β is the receiving angle, α is the transmitting angle, |β-α| is the absolute value of the difference between the receiving angle and the transmitting angle, D is the distance between the transmitting wafer and the receiving wafer, and L is the first distance.

[0014] Optionally, obtaining the distance between the transmitting chip and the blood vessel to be detected includes: obtaining the time required for the transmitting chip to transmit the signal and the receiving chip to receive the signal; determining the distance the signal propagates within the required time according to the required time and the propagation speed of the signal; and determining the first distance according to the propagation distance.

[0015] Optionally, obtaining the distance between the transmitting chip and the blood vessel to be detected includes:

[0016] Acquire a second distance input by a user based on an input device, where the second distance is the distance from the transmitting wafer to the blood vessel to be detected in a direction perpendicular to the skin surface;

[0017] The first distance is determined according to the second distance, wherein the first distance is determined using the following formula:

[0018] L=H / sinα; where H is the second distance.

[0019] Optionally, determining the blood flow velocity measurement value based on the emission angle and the receiving angle includes determining the blood flow velocity measurement value using the following formula:

[0020] V=Δf*c / (f*(cosα+cosβ)); wherein V represents the blood flow velocity measurement value, Δf represents the frequency difference obtained by measuring the blood flow velocity using a Doppler blood flow detection device, c represents the propagation speed of the signal emitted by the transmitting chip, f is the frequency of the signal emitted by the transmitting chip, α is the emission angle, and β is the receiving angle.

[0021] Optionally, the receiving chip in the Doppler blood flow detection device includes a first receiving chip and a second receiving chip, the first receiving chip and the second receiving chip receive a signal transmitted by the same transmitting chip, and the distance between the transmitting chip and the first receiving chip is the same as the distance between the transmitting chip and the second receiving chip;

[0022] Determining the receiving angle according to the transmitting angle, the distance between the transmitting chip and the receiving chip, and the distance between the transmitting chip and the blood vessel to be detected, including: determining a first receiving angle and a second receiving angle; wherein the first receiving angle is the angle between the direction in which the first receiving chip receives the signal and the direction in which the blood flow moves, and the second receiving angle is the angle between the direction in which the second receiving chip receives the signal and the direction in which the blood flow moves;

[0023] Determining a blood flow velocity measurement value according to an emission angle and a receiving angle includes: determining a first blood flow velocity measurement value according to an emission angle and a first receiving angle; determining a second blood flow velocity measurement value according to the emission angle and a second receiving angle; and determining a blood flow velocity measurement value according to the first blood flow velocity measurement value and the second blood flow velocity measurement value.

[0024] Optionally, the method further includes:

[0025] Determine the roll angle of the probe of the Doppler blood flow detection device in the detection state, the roll angle being the angle between the projection direction of the sound field emitted by the transmitting crystal element in the probe on the horizontal plane and the blood flow movement direction in the blood vessel to be detected;

[0026] The blood flow velocity measurement value is corrected according to the roll angle to obtain a blood flow velocity correction value.

[0027] Optionally, the Doppler blood flow detection device includes a triaxial acceleration sensor; determining the roll angle of the probe of the Doppler blood flow detection device in the detection state includes:

[0028] Based on the three-axis acceleration sensor, the acceleration components of gravity acceleration in the three mutually perpendicular coordinate axis directions under the detection state are obtained;

[0029] The roll angle is determined from the acceleration components.

[0030] Optionally, the Doppler blood flow detection device includes a first chip group and a second chip group for being placed at different positions of a blood vessel to be detected; and determining the blood flow velocity measurement value according to the emission angle and the receiving angle includes:

[0031] Determine a blood flow velocity measurement value of the first chip group according to an emission angle and a receiving angle of the blood vessel to be detected through the first chip group;

[0032] Determine a blood flow velocity measurement value of the second chip group according to an emission angle and a receiving angle of the blood vessel to be detected by the second chip group;

[0033] The blood flow velocity measurement value to be output is determined according to the blood flow velocity measurement value of the first wafer group and the blood flow velocity measurement value of the second wafer group.

[0034] In a second aspect, an embodiment of the present application provides a Doppler blood flow detection device for implementing the method for determining blood flow velocity of any one of the above-mentioned first aspects.

[0035] The method for determining blood flow velocity and the Doppler blood flow detection device provided in the embodiment of the present application, wherein the method includes: obtaining the emission angle, which is the angle between the direction of the emission signal of the transmitting element in the Doppler blood flow detection device and the direction of blood flow movement in the blood vessel to be detected; obtaining the distance between the transmitting element and the receiving element in the Doppler blood flow detection device and the distance between the transmitting element and the blood vessel to be detected; determining the receiving angle according to the emission angle, the distance between the transmitting element and the receiving element, and the distance between the transmitting element and the blood vessel to be detected, which is the angle between the direction of the receiving signal received by the receiving element in the Doppler blood flow detection device and the direction of blood flow movement; determining the blood flow velocity measurement value according to the emission angle and the receiving angle; in this way, a more accurate blood flow velocity measurement value can be obtained. In particular, for the case where the blood vessel to be detected is a superficial blood vessel, such as the human carotid artery, the present embodiment can obtain a result that is closer to the actual situation.

[0036] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0038] Figure 1 A schematic flow chart of a method for determining blood flow velocity provided in one embodiment of the present application;

[0039] Figure 2 A structural block diagram of a Doppler blood flow detection device provided in an embodiment of the present application;

[0040] Figure 3 A schematic diagram showing the comparison of receiving angles when a Doppler blood flow detection device is used to detect superficial blood vessels and deep blood vessels;

[0041] Figure 4 A schematic diagram of using a Doppler blood flow detection device to detect a blood vessel to be detected;

[0042] Figure 5 A schematic diagram of using another Doppler blood flow detection device to detect a blood vessel to be detected;

[0043] Figure 6 A schematic diagram of the principle of determining a first distance using ultrasound provided in a specific example of the present application;

[0044] Figure 7 A circuit block diagram for determining a first distance using ultrasound provided in a specific example of the present application;

[0045] Figure 8 A schematic diagram of a process of determining a first distance using ultrasound provided in a specific example of the present application;

[0046] Fig. 9 A schematic diagram of the positions of a wafer group including a first receiving wafer and a second receiving wafer when detecting a blood vessel to be detected is provided as a specific example of the present application;

[0047] Fig.10 is a schematic diagram of the positional relationship between the triaxial acceleration sensor and the blood vessel to be detected when the roll angle is not equal to 90°;

[0048] Fig.11 Schematic diagram of yaw angle, pitch angle and roll angle;

[0049] Fig.12 is a schematic diagram of the position of the blood vessel to be detected when there is a roll angle error and when there is no roll angle error;

[0050] Fig.13 The figure is a schematic diagram of the position of a blood vessel to be detected when a Doppler blood flow detection device is used to detect the blood vessel in a specific application. DETAILED DESCRIPTION

[0051] In order to make the technical solutions and beneficial effects of the present invention more clearly understandable, the following is a detailed description by listing specific embodiments. The drawings are not necessarily drawn to scale, and local features may be enlarged or reduced to more clearly show the details of the local features; unless otherwise defined, the technical and scientific terms used herein have the same meanings as those in the technical field to which this application belongs.

[0052] Unless otherwise defined, the technical terms or scientific terms involved in this application shall have the general meaning understood by people with general skills in the technical field to which this application belongs. The words such as "one", "a", "the", "these" and the like in this application do not indicate quantitative restrictions, and they can be singular or plural. The terms "include", "comprise", "have" and any variants thereof involved in this application are intended to cover non-exclusive inclusions; for example, a process, method and system, product or device comprising a series of steps or modules (units) is not limited to the listed steps or modules (units), but may include unlisted steps or modules (units), or may include other steps or modules (units) inherent to these processes, methods, products or devices. "Multiple" involved in this application refers to two or more. "And / or" describes the association relationship of associated objects, indicating that there can be three relationships, for example, "A and / or B" can represent: A exists alone, A and B exist at the same time, and B exists alone. The terms "first", "second", "third", etc. involved in this application are only used to distinguish similar objects and do not represent a specific ordering of objects.

[0053] In this application, a patient refers to any person who is being or may be tested by a Doppler blood flow detection device, and the patient may also be referred to as a patient. Medical personnel, for example, include people who use a Doppler blood flow detection device to monitor patients, and therefore, are also one of the users of the Doppler blood flow detection device; however, users may include not only medical personnel, but also other people who directly or indirectly use the Doppler blood flow detection device.

[0054] First, please refer to Figure 1 An embodiment of the present application provides a method for determining blood flow velocity, which is applied to a Doppler blood flow detection device. The method includes:

[0055] Step 101, obtaining a transmission angle, where the transmission angle is the angle between the direction of the transmission signal of the transmitting chip in the Doppler blood flow detection device and the direction of blood flow movement in the blood vessel to be detected;

[0056] Step 102, obtaining the distance between the transmitting chip and the receiving chip in the Doppler blood flow detection device and the distance between the transmitting chip and the blood vessel to be detected;

[0057] Step 103, determining a receiving angle according to the transmitting angle, the distance between the transmitting chip and the receiving chip, and the distance between the transmitting chip and the blood vessel to be detected, wherein the receiving angle is the angle between the direction in which the receiving chip in the Doppler blood flow detection device receives the signal and the direction of blood flow movement;

[0058] Step 104: Determine a blood flow velocity measurement value according to the emission angle and the receiving angle.

[0059] It can be understood that the method for determining blood flow velocity provided in the embodiment of the present application can obtain a more accurate blood flow velocity measurement value by first determining the receiving angle according to the emission angle, the distance between the transmitting chip and the receiving chip, and the distance between the transmitting chip and the blood vessel to be detected, and then determining the blood flow velocity measurement value using the emission angle and the receiving angle. In particular, for the case where the blood vessel to be detected is a superficial blood vessel, such as the human carotid artery, the use of this embodiment can obtain a result that is closer to the actual situation.

[0060] Next, please refer to Figure 2 . Figure 2 The structure of a Doppler blood flow detection device provided in an embodiment of the present application is shown. As shown in the figure, the Doppler blood flow detection device includes: a probe, a signal processing module, and a device main body module. Specifically, the probe may include at least one crystal element group. Figure 2 In the example, two wafer groups including a first wafer group and a second wafer group are shown; of course, in some embodiments of the present application, only one wafer group may be included. The first wafer group and the second wafer group are respectively connected to the signal processing module, so that the detected signal is transmitted to the signal processing module; after receiving the signal transmitted by each wafer group, the signal processing module processes the above signal. Specifically, the signal processing module includes a filtering circuit 1, a filtering circuit 2, a signal demodulation 1, a signal demodulation 2, ADC1, and ADC2; the first wafer group is connected to the filtering circuit 1 in the signal processing module, and the second wafer group is connected to the filtering circuit 2 in the signal processing module, and the filtering circuit 1 and the filtering circuit 2 respectively filter the signals detected by the first wafer group and the second wafer group; the filtering circuit 1 is connected to the signal demodulation 1, and the filtering circuit 2 is connected to the signal demodulation 2, and the signal demodulation 1 and the signal demodulation 2 respectively demodulate the signals after filtering by the filtering circuit 1 and the filtering circuit 2; the signal demodulation 1 is connected to the ADC1, and the signal demodulation 2 is connected to the ADC2, and the ADC1 and the ADC2 respectively perform analog-to-digital conversion on the signals after demodulation by the signal demodulation 1 and the signal demodulation 2. The signal processed by the signal processing module is transmitted to the processor. Optionally, the probe may also include a posture sensor. The posture sensor is connected to the processor to transmit the detected sensor signal to the processor. In order to store the received detection results, as well as the intermediate quantities and algorithm programs in the operation process, the device also includes a storage module connected to the processor, such as a memory, a storage, etc. Of course, the device may also include a network port.

[0061] The communication interface provides an interface for communication with other smart devices to transmit data and realize feedback. The communication interface can be a commonly used communication hardware interface such as USB / UART / network port / Bluetooth / WIFI / CAN, and this application does not make specific restrictions on it.

[0062] In addition, the device may also include an audio power amplifier and a speaker connected to the audio power amplifier. The speaker may be used to perform an audio output of the result determined by the processor and to perform an audio output of information that needs to be reminded to the user.

[0063] In this specific example, the device may also include an input device; wherein the input device includes but is not limited to at least one of the following: a keyboard, a button, a voice-controlled input device, and a touch screen. It is understandable that other devices capable of realizing signal input are included in the meaning of this application. In addition, the device may also include an output device; wherein the output device includes but is not limited to an LCD display. Of course, other devices capable of realizing signal output are also included in the meaning of this application. In this way, the device can realize information interaction with the user.

[0064] As a specific implementation, in step 104, the blood flow velocity measurement value is determined according to the emission angle and the receiving angle, including using the following formula to determine the blood flow velocity measurement value: V = Δf*c / (f*(cosα+cosβ)); wherein V represents the blood flow velocity measurement value, Δf represents the frequency difference obtained by measuring the blood flow velocity using a Doppler blood flow detection device, c represents the propagation speed of the signal emitted by the transmitting chip, f is the frequency of the signal emitted by the transmitting chip, α is the emission angle, and β is the receiving angle.

[0065] Herein, c may specifically be the speed of sound propagation in human tissue, which is generally 1570 m / s or 1540 m / s depending on the tissue.

[0066] Below, please refer to Figure 3 , 1011 in the figure represents a superficial blood vessel, 1012 represents a deep blood vessel, T is a transmitting crystal element, R is a receiving crystal element, and T and R are located in the same crystal element group. Among them, the depth of the deep blood vessel 1012 from the skin surface is greater than the depth of the superficial blood vessel 1011 from the skin surface. Correspondingly, the distance between the deep blood vessel 1012 and the crystal element group is greater than the distance between the superficial blood vessel 1011 and the crystal element group. As shown in the figure, when measuring the deep blood vessel 1012 with a deeper depth, the difference between the emission angle α and the corresponding second receiving angle β2 is small, and the two can be considered to be approximately equal when calculating the blood flow velocity measurement value. However, when measuring the shallow blood vessel 1011 with a shallower depth, the ultrasound is still in the near sound field, and the difference between the emission angle α and the corresponding first receiving angle β1 is large. Generally, an error of 2° to 10° may occur due to the depth problem. If the actual receiving angle is not considered, it will obviously lead to a large deviation between the measurement result and the actual situation. It should be noted that the figure only schematically illustrates that when the distances between the blood vessel and the wafer group are different, β1 and β2 will differ greatly, and the angles, sizes and proportional relationships in the figure do not strictly represent the actual situation.

[0067] by Figure 4Take the case shown in the figure as an example, where the transmitting chip T is closer to the blood vessel 101 to be detected than the receiving chip R, assuming: α = 60°, D = 5mm, the normal carotid artery is about 20mm deep from the skin, because the chip group cannot be completely attached to the skin surface when designing the sensor, plus the angle when the chip group is installed, H≈25mm; then, along the direction of the transmitting chip T transmitting the signal, the distance from the transmitting chip T to the blood vessel 101 to be detected is L = 25 / sin60° = 25 / 0.866 = 28.867mm. (β-α) = arctan(D / L) = arctan(5 / 28.867) = 9.823°; β = α + (β-α) = 60° + 9.823° = 69.823°; then cosα + cosβ = cos60° + cos69.823° = 0.5 + 0.345 = 0.845.

[0068] If the blood flow velocity measurement value is calculated by the method that the transmission angle and the reception angle are approximately equal, then V'=Δf*c / (f*2cosα).

[0069] In fact, V = Δf*c / (f*(cosα+cosβ)).

[0070] The error percentage is: |V'-V| / V=|V' / V-1|=|(cosα+cosβ) / 2cosα-1|=15.5%.

[0071] Figure 5 Schematic diagram of another Doppler blood flow detection device for detecting a blood vessel to be detected. In the Doppler blood flow detection device, the transmitting chip T is farther away from the blood vessel to be detected 101 than the receiving chip R. It can be understood that in this case, the formula V = Δf*c / (f*(cosα+cosβ)) is used to determine the blood flow velocity measurement value, which can also reduce the error. The specific error rate is not calculated here.

[0072] It can be understood that although the specific steps for obtaining blood flow velocity measurement values ​​are described in this embodiment, the above specific steps are obviously also applicable to the case where there are multiple chip groups in the Doppler blood flow detection device, that is, each chip group can use the above steps to obtain blood flow velocity measurement values.

[0073] Wherein, obtaining the emission angle may specifically include: obtaining the emission angle α pre-stored in the Doppler blood flow detection device. It can be understood that the specific value of the emission angle α may be a fixed angle value determined when the Doppler blood flow detection device is designed.

[0074] Acquiring the distance D between the transmitting wafer T and the receiving wafer R in the same wafer group in the Doppler blood flow detection device may specifically include: acquiring the distance D between the transmitting wafer T and the receiving wafer R in the same wafer group pre-stored in the Doppler blood flow detection device. The D value may also be a fixed value determined when the Doppler blood flow detection device is designed.

[0075] The distance between the transmitting chip T and the blood vessel 101 to be detected includes a first distance L, which is the distance from the transmitting chip T to the blood vessel 101 to be detected along the direction in which the transmitting chip T transmits the signal; as a specific implementation, the receiving angle β is determined according to the transmitting angle α, the distance D between the transmitting chip T and the receiving chip R, and the distance L between the transmitting chip T and the blood vessel 101 to be detected, including using the following formula to determine the receiving angle β: |β-α|=arctan(D / L); wherein β is the receiving angle, α is the transmitting angle, |β-α| is the absolute value of the difference between the receiving angle and the transmitting angle, D is the distance between the transmitting chip and the receiving chip, and L is the first distance.

[0076] Please refer to Figure 6 Exemplarily, obtaining the distance between the transmitting chip T and the blood vessel 101 to be detected includes: obtaining the time t required for the transmitting chip T to transmit the signal and the receiving chip R to receive the signal; determining the distance the signal propagates within the required time according to the required time t and the propagation speed c of the signal; and determining the first distance L according to the propagation distance.

[0077] In practical applications, the distance between the transmitting wafer T and the blood vessel 101 to be detected can be measured by A-ultrasound, B-ultrasound and other techniques. Figure 6 , the transmitter T is, for example, an ultrasonic transmitter, the receiver R is, for example, an ultrasonic receiver, and the obstacle is, for example, a blood vessel to be detected; the transmitter T transmits a short segment of ultrasonic waves of a fixed frequency to the obstacle, and starts timing when the transmission begins. The ultrasonic wave has a propagation speed c and time in the object, and enters the receiver R after being reflected by the obstacle. The time from transmission to reception can be measured as t, and the propagation speed of the ultrasonic wave in the object is c, then the measured distance can be calculated, and the actual distance can be estimated according to the measured distance. The first distance can be determined by the following formula: L = c*t / 2.

[0078] Specifically, the original acquisition circuit and sensor can be used to acquire Doppler signals using a PW pulse wave Doppler method, and the time difference between transmission and reception can be recorded in each occurrence cycle to calculate the measured distance and angle. This method uses time domain data for analysis and calculation.

[0079] Since the propagation speed of ultrasound in human tissue is c=1570m / s=1570000mm / s, the blood vessel depth of the neck is between 5mm-30mm (i.e. H is between 5mm-30mm), and the range of L is between 7mm-42mm. The range of T is between 7 / 1570000~42 / 1570000s, 7 / 1570~42 / 1570ms, and 4.5μs~27μs. The ultrasonic frequency used can be between 2MHz and 8MHz, specifically, the ultrasonic frequency is 4MHz. Taking the ultrasonic frequency of 4MHz as an example, the duration of each transmission cycle is 1 / 4MHz=0.25μs; then, 5 ultrasonic cycles are transmitted, and the total transmission duration is 1.25μs, which can meet the sampling interval time.

[0080] Figure 7 A circuit block diagram for determining a first distance using ultrasound provided in a specific example of the present application; Figure 8 A schematic diagram of a process for determining a first distance using ultrasound is provided as a specific example of the present application.

[0081] First, please refer to Figure 7 . The circuit in the figure is a part of the signal conditioning part in the overall circuit, which is specially used for distance testing. Among them, the generation control circuit, signal demodulation and signal amplification parts are shared. When performing a distance test, the generation control circuit controls the transmitting chip to send a signal. After the receiving chip receives the signal, the signal demodulation and signal amplification respectively demodulate and amplify the signal; wherein, the received signal will be input into the ADC (not shown in the figure) for collection. When performing a distance test, the signal enters the analog comparator for comparison, and the analog comparator outputs a digital signal, which is directly collected by the I / O pin of the processor.

[0082] Next, please refer to Figure 8 . The process of using ultrasound to determine the first distance includes: after starting the distance test, the transmitting chip transmits an ultrasonic signal, starts timing, and turns off the transmission; the ultrasonic signal is transmitted through the tissue to collide with the blood, and the Doppler effect occurs and then reflects to the receiving chip. The receiving chip performs i / q demodulation on the ultrasonic signal, and the demodulated signal is output as a weak analog signal. The signal amplification circuit amplifies the signal to a set range. The greater the blood flow velocity, the greater the signal. Set a comparison voltage V0. When the signal is greater than V0, the analog comparator outputs 1; when the signal is less than V0, the analog comparator outputs 0.

[0083] The method for determining each ranging cycle is as follows: the ultrasonic signal is emitted from the transmitting chip and the timing is started. If the analog comparator output changes from 0 to 1, it is considered to be the ultrasonic transmission time measured in this cycle. Specifically, the result of the comparator trigger is determined to be yes or no. If the result is yes, the time N is recorded; if the result is no, the waiting time is up until the total acquisition time is up.

[0084] Since the speed of dynamic blood flow increases from small to large and then turns small in a pulsation cycle, from the design circuit, the greater the blood flow speed, the greater the signal, the earlier the analog comparator will be triggered, and the more accurate the measured time will be in this case. Therefore, it is optional to set a time period, such as a measurement time of 2s-5s, preferably 3s, to ensure that the signal under the maximum blood flow state can be measured in one measurement time. In the case of 3s, the pulse of the patient being measured is 20bpm, which can meet clinical requirements.

[0085] like Figure 8 As shown, from the emission of ultrasonic waves to the total acquisition time, the recorded time is sorted from small to large, the abnormal points are removed, the three smallest times are selected and averaged, and the distance test is completed.

[0086] According to the formula L=c*t / 2, the first distance is determined. Then the receiving angle is calculated by the following formula: |β-α|=arctan(D / L).

[0087] As another optional embodiment, obtaining the distance between the transmitting chip T and the blood vessel to be detected 101 includes: obtaining a second distance H input by the user based on an input device, the second distance H being the distance from the transmitting chip T to the blood vessel to be detected 101 in a direction perpendicular to the skin surface; determining a first distance L based on the second distance H, wherein the first distance L is determined by the following formula: L=H / sinα; wherein H is the second distance.

[0088] The second distance H is input into the Doppler blood flow detection device by medical personnel, for example.

[0089] Next, please refer to Fig. 9Optionally, the receiving element in the Doppler blood flow detection device includes a first receiving element R1 and a second receiving element R2, the first receiving element R1 and the second receiving element R2 receive a signal transmitted by the same transmitting element T, and the distance D1 between the transmitting element T and the first receiving element R1 is the same as the distance D2 between the transmitting element T and the second receiving element R2; determining the receiving angle according to the transmitting angle, the distance between the transmitting element and the receiving element, and the distance between the transmitting element and the blood vessel to be detected, including: determining a first receiving angle β1 and a second receiving angle β2; wherein the first The receiving angle β1 is the angle between the direction in which the first receiving element R1 receives the signal and the direction in which the blood flows. The second receiving angle β2 is the angle between the direction in which the second receiving element R2 receives the signal and the direction in which the blood flows. The blood flow velocity measurement value is determined according to the emission angle and the receiving angle, including: determining a first blood flow velocity measurement value V10 according to the emission angle α and the first receiving angle β1; determining a second blood flow velocity measurement value V20 according to the emission angle α and the second receiving angle β2; and determining a blood flow velocity measurement value V according to the first blood flow velocity measurement value V10 and the second blood flow velocity measurement value V20.

[0090] Among them, the distance D1 between the transmitting wafer T and the first receiving wafer R1 is the same as the distance D2 between the transmitting wafer T and the second receiving wafer R2, so α-β2≈β1-α, and the angle difference is assumed to be ε. When the transmitting wafer T transmits a signal, the first receiving wafer R1 and the second receiving wafer R2 can receive the signal at the same time. Then, the velocity components corresponding to the first receiving wafer R1 and the second receiving wafer R2 are equal, Δf1=Δf2=Δf*cosε.

[0091] Assuming α=60°, passing ε=9.823°, therefore β1=α+ε=69.823°, β2=α-ε=50.177°.

[0092] Let △f*c / 2f=A;

[0093] If the difference between the transmitting angle and the receiving angle is not considered, the actual blood flow velocity V11 that should be detected is △f*c / (2f*cosα)=A / cosα=A / 0.5=2A;

[0094] In this method, the blood flow velocity measurement value V is determined according to the first blood flow velocity measurement value V10 and the second blood flow velocity measurement value V20. Specifically, for example, the average value of the first blood flow velocity measurement value V10 and the second blood flow velocity measurement value V20 is determined as the blood flow velocity measurement value V. Then,

[0095] V10=△f*c / (f*(cosα+cosβ1))=2A / (cos60°+cos69.823°)=2.332A;

[0096] V20=△f*c / (f*(cosα+cosβ2))=2A / (cos60°+cos50.177°)=1.748A;

[0097] Then V = (V1 + V2) / 2 = 2.04A.

[0098] In this way, the error can be reduced by using this method. And the smaller β is, the smaller the error is.

[0099] As an optional implementation, the method may also include: determining the roll angle of the probe of the Doppler blood flow detection device in the detection state, the roll angle being the angle between the projection direction of the sound field emitted by the transmitting element in the probe on the horizontal plane and the direction of blood flow movement in the blood vessel to be detected; correcting the blood flow velocity measurement value according to the roll angle to obtain a blood flow velocity correction value.

[0100] In this way, the error caused by the deviation of the direction of the sound field emitted by the transmitting chip during the measurement of the probe can be corrected, further improving the accuracy of the measurement results. Ultimately, a more reliable blood flow velocity measurement value can be output, providing a more reliable basis for medical staff to judge the patient's condition.

[0101] Please continue to refer to Figure 2 The Doppler blood flow detection device also includes a posture sensor arranged in the probe; determining the roll angle of the probe in the detection state includes: using the posture sensor to determine the roll angle of the probe in the detection state.

[0102] The attitude sensor is a high-performance three-dimensional motion attitude measuring instrument. The attitude sensor may include at least one of the following: a three-axis acceleration sensor, a gyroscope, a three-axis electronic compass, and other motion sensors.

[0103] As an optional implementation, the posture sensor includes a three-axis acceleration sensor; determining the roll angle of the probe in a detection state includes: obtaining the acceleration components of gravity acceleration in three mutually perpendicular coordinate axis directions in the detection state based on the three-axis acceleration sensor; and determining the roll angle based on the acceleration components.

[0104] In a specific application, when starting to measure the blood flow velocity, the user places the probe at the measurement position according to a predetermined usage method, wherein the predetermined usage method is, for example, to ensure that the projection direction of the sound field emitted by the transmitting element in the probe on the horizontal plane is perpendicular to the direction of blood flow movement in the blood vessel to be detected, and no discrete angle is generated, thereby reducing the measurement error. During the measurement process, the patient can be considered to be stationary. At this time, the initial output value of the three-axis acceleration sensor can be recorded as a reference for the roll angle calculated later.

[0105] It can be understood that, taking the blood vessel to be detected as being located in a horizontal plane, if the chip of the three-axis acceleration sensor is placed horizontally, and a rectangular coordinate system including three coordinate axes XYZ is established in the direction of the three-axis acceleration sensor, then the components of the gravitational acceleration g in the X-axis and Y-axis directions are both 0, and the component in the Z-axis direction is g.

[0106] However, in actual measurement, especially in long-term monitoring, it is very likely that the projection direction of the sound field emitted by the transmitting element in the probe on the horizontal plane is not perpendicular to the direction of blood flow in the blood vessel to be tested due to patient movement, thus causing measurement errors.

[0107] Fig.10 The figure shows the positional relationship between the triaxial acceleration sensor and the blood vessel to be detected when the roll angle is not equal to 90°. Since the triaxial acceleration sensor is located inside the probe, Fig.10 That is, the positional relationship between the three-axis acceleration sensor and the blood vessel to be detected, that is, the projection direction of the sound field emitted by the transmitting element in the probe on the horizontal plane is not perpendicular to the direction of blood flow in the blood vessel to be detected. As shown in the figure, the component of gravity acceleration g in the X-axis direction is Ax, the angle between Ax and the blood vessel to be detected 101 is a1, and the angle with gravity acceleration g is a; the component of gravity acceleration g in the Y-axis direction is Ay, the angle between Ay and the blood vessel to be detected 101 is b1, and the angle with gravity acceleration g is b; the component of gravity acceleration g in the Z-axis direction is Az, the angle between Az and the blood vessel to be detected 101 is γ1, and the angle with gravity acceleration g is γ. Among them, the relationship between each angle is: a = 90°-a1, b = 90°-b1, γ = 90°-γ1.

[0108] The components of the gravitational acceleration g in each axis direction are: Ax=gcosa, Ay=gcosb, Az=gcosγ; or: Ax=gsina1, Ay=gsinb1, Az=gsinγ1.

[0109] Further:

[0110] g*g=Ax*Ax+gcosa1*gcosa1;

[0111] gcosa1 = squr(g*g-Ax*Ax);

[0112] Similarly,

[0113] gcosb1 = squr(g*g-Ay*Ay);

[0114] gcosγ1=squr(g*g-Az*Az).

[0115] In solid geometry, g is equivalent to the diagonal of the cube, and Ax, Ay, and Az are equivalent to the three sides, so according to the Pythagorean theorem: Ax*Ax+Ay*Ay+Az*Az=g*g.

[0116] Taking the X-axis as an example, sina1 = Ax / g, cosa1 = squr(g*g-Ax*Ax) / g;

[0117] tana1=Ax / squr(g*g-Ax*Ax)=Ax / squr(Ay*Ay+Az*Az).

[0118] Similarly,

[0119] tanb1=Ay / squr(Ax*Ax+Az*Az);

[0120] tanγ1=Az / squr(Ax*Ax+Ay*Ay).

[0121] Thus, the relationship between the measured value of the triaxial acceleration sensor and a1, b1 and γ1 is obtained. Here, the values ​​of a1, b1 and γ1 are equal to the corresponding radian values.

[0122] Next, the radian values ​​between each axis and the horizontal line (reference blood vessel 101 to be detected in the figure) are calculated, wherein a11, b11, and γ11 represent the radian values ​​between the X-axis direction, the Y-axis direction, the Z-axis direction and the horizontal line, respectively; then:

[0123] a11=arctan(Ax / squr(Ay*Ay+Az*Az));

[0124] b11=arctan(Ay / squr(Ax*Ax+Az*Az));

[0125] γ11=arctan(Az / squr(Ax*Ax+Ay*Ay)).

[0126] Next, use the following formula to calculate: radian = angle value * πR / 180; that is, angle value = radian * 180 / πR, where R is 1. Finally, the angle values ​​of each axis are:

[0127] φ=a11*180 / π=[arctan(Ax / squr(Ay*Ay+Az*Az))]*180 / π;

[0128] ψ=b11*180 / π=[arctan(Ay / squr(Ax*Ax+Az*Az))]*180 / π;

[0129] θ=γ11*180 / π=[arctan(Az / squr(Ax*Ax+Ay*Ay))]*180 / π;

[0130] Among them, ψ is the angle value corresponding to the radian value b11, θ is the angle value corresponding to the radian value γ11, φ is the angle value corresponding to the radian value a11; φ is the roll angle.

[0131] It can be understood that the directions of the three mutually perpendicular coordinate axes are established according to the directions of the three-axis acceleration sensor in the measuring state. The three-axis acceleration sensor and the transmitting chip are located together in the probe. Therefore, the direction of the three-axis acceleration sensor can represent the direction of the transmitting chip. Therefore, the angle between the projection direction of the sound field emitted by the transmitting chip on the horizontal plane and the direction of blood flow movement can be determined based on the acceleration component.

[0132] As another optional implementation, the attitude sensor includes a gyroscope; determining the roll angle of the probe in the detection state includes: obtaining the roll angle in the detection state based on the gyroscope.

[0133] Fig.11 is a schematic diagram of yaw angle, pitch angle and roll angle; wherein (a) shows yaw angle ψ, (b) shows pitch angle θ, and (c) shows roll angle φ. The spatial trajectory of the moving object is decomposed into independent motions along the Z, Y, and X axes, and the component of the motion vector in each axis is represented by the cosine of the angle between the vector and each axis. The moving object is, for example, a posture sensor. There are nine direction cosine parameters, which can be expressed by a 3rd-order direction cosine matrix To express. The component format is as follows:

[0134]

[0135] The three-fold Euler rotation of a moving object can be represented by three direction cosine matrices:

[0136]

[0137]

[0138]

[0139] Cosine Matrix Product Used to express the transformation from the geographic coordinate system to the moving object coordinate system:

[0140]

[0141]

[0142]

[0143] After obtaining the attitude update matrix of the moving object coordinate system relative to the geographic coordinate system After that, the angular rate data obtained by the attitude sensor can be converted into attitude angle data.

[0144]

[0145] It represents the gravity component sensed by the accelerometer in each axis direction, and

[001] represents the component of the gravity field measured in each axis of the accelerometer in the geographic coordinate system.

[0146] The inclination angle (roll angle φ and pitch angle θ) can be obtained by using inverse trigonometric functions:

[0147]

[0148]

[0149] In actual use, according to the characteristics of the human body, it can be considered that the relative angle between the Z-axis direction and the direction of the blood vessel to be detected is unchanged, that is, γ and γ1 remain unchanged, that is, the pitch angle remains unchanged, and only the roll angle φ needs to be used for angle correction.

[0150] It is understandable that when the position of the human body changes, the position of the posture sensor and the blood vessel to be detected changes synchronously. In the Doppler effect, what works is the angle parallel to the plane where the blood flow direction in the blood to be detected is located.

[0151] The blood flow velocity measurement value is corrected according to the roll angle to obtain a correction value, including obtaining the correction value using the following formula: V1=V / sinφ; wherein V1 represents the correction value, V represents the blood flow velocity measurement value, and φ represents the roll angle.

[0152] Please refer to Fig.12 When the probe is placed at the measurement position according to the predetermined usage method, the roll angle φ is equal to 90°, and the measurement result has no roll angle error. When there is a roll angle error, that is, after the probe rotates, according to the principle of velocity component, the blood flow velocity measurement value obtained at this time is the velocity component of the blood flow velocity measurement value that should be obtained when there is no roll angle error in the direction after rotation. Therefore, the corrected blood flow velocity can be obtained by the formula V1=V / sinφ, that is, or theoretically equal to the corrected value of the blood flow velocity measurement value that should be obtained when there is no roll angle error.

[0153] It can be understood that when the roll angle φ is equal to 90°, according to the above formula V1=V / sinφ, it can be calculated that V1=V, which further illustrates that there is no roll angle error in the measurement result at this time.

[0154] As an optional embodiment, the Doppler blood flow detection device includes a first chip group and a second chip group for being placed at different positions of the blood vessel to be detected; determining the blood flow velocity measurement value according to the emission angle and the receiving angle includes: determining the blood flow velocity measurement value of the first chip group according to the emission angle and the receiving angle of the blood vessel to be detected via the first chip group; determining the blood flow velocity measurement value of the second chip group according to the emission angle and the receiving angle of the blood vessel to be detected via the second chip group; determining the blood flow velocity measurement value to be output according to the blood flow velocity measurement value of the first chip group and the blood flow velocity measurement value of the second chip group.

[0155] In this way, at least two chip groups placed at different positions of the blood vessel to be tested are used to perform measurements respectively. Even if the angle between the probe and the blood vessel to be tested in the actual measurement is inconsistent with the Doppler angle set in the device, the measurement result can be comprehensively determined based on the blood flow velocity measurement values ​​of each chip group, thereby reducing the error caused by the above situation.

[0156] The first wafer group and the second wafer group are used to be placed at different positions of the blood vessel to be detected. For example, one of the first wafer group and the second wafer group is placed at the first position of the blood vessel to be detected, and the other is placed at the second position of the blood vessel to be detected. The first position and the second position are respectively the front and rear positions of the blood vessel to be detected along the direction of blood flow movement, that is, the direction of blood flow movement is the direction from the first position to the second position. It should be understood that the blood vessel to be detected is wrapped by the skin, and the first wafer group and the second wafer group are obviously not in direct contact with the blood vessel to be detected. The first wafer group and the second wafer group described in this article are placed at different positions of the blood vessel to be detected, which means that the first wafer group and the second wafer group are placed at different positions corresponding to the blood vessel to be detected across the skin.

[0157] Please refer to Fig.13In a specific example, for ease of understanding, it can be considered that the first wafer group and the second wafer group are placed at the left and right positions respectively, that is, the first wafer group and the second wafer group can be referred to as the left wafer group and the right wafer group respectively. The dotted box in the figure shows the situation where the angle between the probe and the blood vessel to be detected is consistent with the Doppler angle set in the Doppler blood flow detection device, that is, the actual Doppler angle is equal to the set Doppler angle, and both are equal to the emission angle α. At this time, the left wafer group and the right wafer group are respectively shown as left 0 and right 0 in the figure. However, in actual measurement, it is often difficult to ensure that the actual Doppler angle is completely consistent with the set Doppler angle, that is, measurement errors will occur. The solid box in the figure shows the situation where the actual Doppler angle is inconsistent with the Doppler angle set in the Doppler blood flow detection device. At this time, the actual Doppler angle is α', and the left wafer group and the right wafer group are respectively shown as left 1 and right 1 in the figure. It can be understood that since the blood flow velocity measurement value V of the first wafer group or the blood flow velocity measurement value V of the second wafer group obtained is the vertical component of the actual blood flow velocity V0 in the direction of the corresponding wafer group transmitting or receiving the signal, V = V0 / cosα. Then, if the deviation angle r between α and α' is 1°, the measurement error △V = V0 / cosα-V0 / cos(α') = V0 / cosα-V0 / cos(α±1). It can be seen that the larger the set Doppler angle, the greater the error generated.

[0158] In order to reduce the error, the probe of the Doppler blood flow detection device used in the embodiment of the present application includes the above-mentioned first chip group and second chip group, and two-way Doppler channel acquisition is realized by the first chip group and the second chip group. Since the first chip group and the second chip group are placed at different positions on the blood vessel to be detected, the two-way Doppler channel acquisition has two Doppler angles, and the blood flow velocity measurement value of the first chip group and the blood flow velocity measurement value of the second chip group are obtained based on two different Doppler angles. On this basis, the blood flow velocity measurement value of the first chip group and the blood flow velocity measurement value of the second chip group can also be corrected according to the roll angle to obtain the first correction value and the second correction value; and then the blood flow velocity measurement value to be output is determined according to the first correction value and the second correction value. In this way, by combining the corrected first correction value and the second correction value, a more accurate blood flow velocity measurement value can be obtained.

[0159] The first wafer group includes at least one transmitting wafer and at least one receiving wafer, and the second wafer group also includes at least one transmitting wafer and at least one receiving wafer. The first wafer group and the second wafer group transmit and sample synchronously. The blood flow velocity measurement value of the first wafer group and the blood flow velocity measurement value of the second wafer group have the same measurement time. The transmitting wafer in the left wafer group transmits signals from left to right, for example, and the transmitting wafer in the right wafer group transmits signals from right to left, for example.

[0160] In a specific application, the frequencies of the signals emitted by the transmitting chips in the first chip group and the second chip group are different, so that the Doppler blood flow detection device is a dual-frequency and dual-channel abnormal probe detection device. Optionally, the frequencies of the signals emitted by the first chip group and the second chip group are in the range of 1 MHz - 16 MHz to meet the requirements of dual-frequency and dual-channel detection. Further, the frequencies of the signals emitted by the first chip group and the second chip group are in the range of 2 MHz - 8 MHz, and the accuracy of the detection results is better. The frequency of the signal emitted by the transmitting chip in the first chip group and one of the frequencies of the signals emitted by the transmitting chips in the second chip group are F1, and the other is F2. To improve the accuracy of the detection results, F1 and F2 satisfy the following conditions: F1 < F2; the remainder of F2 divided by F1 is greater than 0.5 MHz, F2 % F1 > 0.5 MHz; and F2 < 3F1. Taking the remainder means taking out the extra part that cannot be divided evenly; specifically, if F2 = nF1 + x, where n is a positive integer and x < F1, then the remainder of F2 divided by F1 is equal to x.

[0161] As a preferred example, F1 = 2.1 MHz - 2.7 MHz, F2 = 3.8 MHz - 4.3 MHz.

[0162] In a specific example, notch filters are used in the signal filtering of the first chip group and the second chip group. The bandwidth range of one of them is F1 - 0.5 MHz to F1 + 0.5 MHz; the bandwidth range of the other is F2 - 0.5 MHz to F2 + 0.5 MHz. In this way, different filtering bandwidths are set for different channels. When transmitting simultaneously in dual channels, the receiving chips on both sides can receive the signals of both transmitting chips, that is, there will be interference with each other. In this specific example, filtering corresponding to the corresponding channel and frequency band is selected, and the signals of the other frequency band can be suppressed to achieve a better signal-to-noise ratio.

[0163] Remove the ultrasonic interference in the two channels through filtering and demodulation techniques.

[0164] As an optional implementation manner, determining the blood flow velocity measurement value to be output according to the blood flow velocity measurement values of the first chip group and the second chip group may include: determining the average value of the blood flow velocity measurement values of the first chip group and the second chip group as the blood flow velocity measurement value to be output.

[0165] It can be understood that in the implementation manner of performing the above corrections on the blood flow velocity measurement values of the first chip group and the second chip group according to the roll angle respectively, determining the blood flow velocity measurement value to be output according to the first correction value and the second correction value includes: determining the average value of the first correction value and the second correction value as the blood flow velocity measurement value to be output.

[0166] On this basis, the embodiment of the present application also provides a Doppler blood flow detection device, which is used to implement the method for determining the blood flow velocity in any one of the above embodiments.

[0167] It should be understood that the detailed technical features of the Doppler blood flow detection device can refer to the relevant description in the above-mentioned embodiment of the method for determining the blood flow velocity, and will not be repeated here.

[0168] It should be understood that, although the various steps in the flowcharts of the present application are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence according to the order indicated by the arrows. Unless there is a clear description in this article, the execution of these steps is not strictly limited in order, and these steps can be executed in other orders. Moreover, at least a portion of the steps in the figure may include multiple steps or multiple stages, and these steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily carried out in sequence, but can be executed in turn or alternately with other steps or at least a portion of the steps or stages in other steps.

[0169] It should be understood that the above embodiments are exemplary and are not intended to include all possible implementations included in the claims. Various modifications and changes may be made on the basis of the above embodiments without departing from the scope of the present disclosure. Similarly, the various technical features of the above embodiments may be arbitrarily combined to form other embodiments of the present invention that may not be explicitly described. Therefore, the above embodiments only express several implementations of the present invention and do not limit the scope of protection of the patent of the present invention.

Claims

1. A method for determining blood flow velocity, applied to a Doppler blood flow detection device, characterized in that: The method comprises: Acquire the emission angle, where the emission angle is the angle between the direction of the emission signal of the transmitting chip in the Doppler blood flow detection device and the direction of blood flow movement in the blood vessel to be detected; Acquire the distance between the transmitting chip and the receiving chip in the Doppler blood flow detection device and the distance between the transmitting chip and the blood vessel to be detected; Determine a receiving angle according to the transmitting angle, the distance between the transmitting chip and the receiving chip, and the distance between the transmitting chip and the blood vessel to be detected, wherein the receiving angle is the angle between the direction in which the receiving chip in the Doppler blood flow detection device receives the signal and the direction of blood flow movement; determining a blood flow velocity measurement value based on the emission angle and the reception angle; The distance between the transmitting chip and the blood vessel to be detected includes a first distance, which is the distance from the transmitting chip to the blood vessel to be detected along the direction in which the transmitting chip transmits the signal; Determining the receiving angle according to the transmitting angle, the distance between the transmitting element and the receiving element, and the distance between the transmitting element and the blood vessel to be detected includes using the following formula to determine the receiving angle: |β-α|=arctan(D / L); wherein β is the receiving angle, α is the transmitting angle, |β-α| is the absolute value of the difference between the receiving angle and the transmitting angle, D is the distance between the transmitting wafer and the receiving wafer, and L is the first distance.

2. The method for determining blood flow velocity according to claim 1, characterized in that: The method of obtaining the distance between the transmitting chip and the blood vessel to be detected includes: obtaining the time required for the transmitting chip to transmit the signal and the receiving chip to receive the signal; determining the distance the signal propagates within the required time according to the required time and the propagation speed of the signal; and determining the first distance according to the propagation distance.

3. The method for determining blood flow velocity according to claim 1, characterized in that: The obtaining of the distance between the transmitting wafer and the blood vessel to be detected includes: Acquire a second distance input by a user based on an input device, where the second distance is the distance from the transmitting wafer to the blood vessel to be detected in a direction perpendicular to the skin surface; The first distance is determined according to the second distance, wherein the first distance is determined using the following formula: L=H / sinα; where H is the second distance.

4. The method for determining blood flow velocity according to claim 1, characterized in that: Determining the blood flow velocity measurement value according to the emission angle and the receiving angle includes using the following formula to determine the blood flow velocity measurement value: V=Δf*c / (f*(cosα+cosβ)); wherein V represents the blood flow velocity measurement value, Δf represents the frequency difference obtained by measuring the blood flow velocity using the Doppler blood flow detection device, c represents the propagation speed of the signal emitted by the transmitting chip, f is the frequency of the signal emitted by the transmitting chip, α is the emission angle, and β is the receiving angle.

5. The method for determining blood flow velocity according to claim 1, characterized in that: The receiving chip in the Doppler blood flow detection device includes a first receiving chip and a second receiving chip, the first receiving chip and the second receiving chip receive the signal transmitted by the same transmitting chip, and the distance between the transmitting chip and the first receiving chip is the same as the distance between the transmitting chip and the second receiving chip; Determining the receiving angle according to the transmitting angle, the distance between the transmitting chip and the receiving chip, and the distance between the transmitting chip and the blood vessel to be detected includes: determining a first receiving angle and a second receiving angle; wherein the first receiving angle is the angle between the direction in which the first receiving chip receives the signal and the direction in which the blood flows, and the second receiving angle is the angle between the direction in which the second receiving chip receives the signal and the direction in which the blood flows; The method of determining the blood flow velocity measurement value based on the emission angle and the receiving angle includes: determining a first blood flow velocity measurement value based on the emission angle and the first receiving angle; determining a second blood flow velocity measurement value based on the emission angle and the second receiving angle; and determining the blood flow velocity measurement value based on the first blood flow velocity measurement value and the second blood flow velocity measurement value.

6. The method for determining blood flow velocity according to claim 1, characterized in that: The method further comprises: Determine the roll angle of the probe of the Doppler blood flow detection device in the detection state, wherein the roll angle is the angle between the projection direction of the sound field emitted by the transmitting element in the probe on the horizontal plane and the blood flow movement direction in the blood vessel to be detected; The blood flow velocity measurement value is corrected according to the roll angle to obtain a blood flow velocity correction value.

7. The method for determining blood flow velocity according to claim 6, characterized in that: The Doppler blood flow detection device includes a three-axis acceleration sensor; the method for determining the roll angle of the probe of the Doppler blood flow detection device in the detection state includes: Obtaining acceleration components of gravity acceleration in three mutually perpendicular coordinate axis directions under a detection state based on the three-axis acceleration sensor; The roll angle is determined based on the acceleration component.

8. The method for determining blood flow velocity according to claim 1, characterized in that: The Doppler blood flow detection device comprises a first chip group and a second chip group for being placed at different positions of a blood vessel to be detected; and determining the blood flow velocity measurement value according to the emission angle and the receiving angle comprises: Determine a blood flow velocity measurement value of the first wafer group according to the emission angle and the receiving angle of the blood vessel to be detected through the first wafer group; Determine a blood flow velocity measurement value of the second wafer group according to the emission angle and the receiving angle of the blood vessel to be detected through the second wafer group; The blood flow velocity measurement value to be output is determined according to the blood flow velocity measurement value of the first wafer group and the blood flow velocity measurement value of the second wafer group.

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