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Chinese medicine has a long history of thousands of years, is a treasure of Chinese culture, has made indelible contributions to the reproduction of the Chinese nation, occupies a very important position in traditional Chinese medicine, and the history of pulse diagnosis is long and long. Pulse diagnosis has always been the focus and difficulty of TCM teaching, from the earliest pattern diagram, schematic diagram to the current waveform diagram, researchers have been looking for the best way and way to objectify pulse diagnosis.
The selection and application of sensor types and schemes is a key part of the research on pulse diagnosis objectivity. In this paper, the working principle and application scheme of various pulse acquisition sensors are discussed.
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Sensor type and working principle
Pulse imager is an important tool for the objectiveization of pulse diagnosis in Traditional Chinese medicine, the sensor is an indispensable part of it, and different sensors determine the different working methods of the pulse imager. The sensors used in today's pulse imagers can be divided into mechanical sensors, pressure sensors, photoelectric sensors, ultrasonic sensors and microphones according to the working principle.
Among them, the pulser using mechanical sensors was first introduced, but due to its shortcomings in automatic control, it was also limited in research. Mechanical and pressure sensors are contact sensors, and photoelectric and ultrasonic sensors and microphones are non-contact sensors. The working principle of non-contact sensors does not conform to the finger-press pulse cutting method of Traditional Chinese medicine, but it also provides an idea for the objective study of pulse diagnosis from the side. In addition, sensors made of nano and graphene technologies and pulse signal detection methods in the space-time domain have also begun to appear in recent years.
One / pressure sensor
In the development process of pulse imager, the pressure sensor was first applied, which is more in line with the diagnosis method of "lifting, pressing and finding" of traditional Chinese medicine, and is currently the most widely used and the research is more in-depth. Pressure sensors are mainly divided into three types: piezoresistive, piezoelectric and piezomagnetic according to the principle.
Piezoresistive sensors
Piezoresistive sensor according to the principle of resistivity changes with the change of force, the use of resistance to reflect the change of pulse force, the principle is simple, widely used, due to different stresses there are different influencing factors, so there is a certain degree of distortion. According to the different pressure conductive media, it is divided into three types: solid-state piezoresistive sensors, hydraulic sensors and air-conducted sensors. Some researchers use air-conducted sensors to convert the pulse wave voltage signal, and at the same time use Bluetooth technology and integrated display to achieve human-computer interaction, making a portable wearable pulse diagnosis device.
Piezoelectric sensors
Piezoelectric sensors use the physical properties of piezoelectric materials to complete the transformation of the pulse's pressure signal to an electrical signal. according to
The differences in piezoelectric materials are divided into four types: piezoelectric crystal sensors, piezoelectric ceramic sensors, piezoelectric polymer sensors and composite piezoelectric material sensors.
Piezoelectric sensors perform well in terms of sensitivity, frequency response, immunity, stability, and soft tissue acoustic impedance matching, but there are shortcomings such as high cost and volatile charge. Some researchers have designed a new type of piezoelectric thin film (PVDF) multi-point pulse wave computer-aided test system, which achieves multi-point, dynamic and synchronous measurement of pulse signal, and can display various pulse maps at multiple levels, while performing spectrum analysis and digital filtering. Okada in Japan
Teng was the first to use piezoelectric ceramic sensors to develop a pulse imager for floating, medium and sinking pulse images, and elaborated 6 corresponding pulse images.
Piezomagnetic sensors
Piezo magnetic sensor with the help of magnetic elastic effect, the force is converted into the permeability of the sensor, and the corresponding electrical signal is output by the change of permeability information, the structure is simple, the signal is strong, is the emerging sensor in the world in recent years. However, the theory and technology of such sensors such as material selection and processing still need further research.
The market has a sensor system that combines fiber Bragg light (FBG) pressure sensor and phase-generated carrier wave (PGC) interferometric wavelength demodulation, using the wavelength modulation principle of FBG to display the pressure signal through modulation and demodulation wavelength change, so as to achieve accurate detection and accurate reduction of pulse pulse conditions.
2/ Photoelectric sensors
Japanese researchers were the first to use photoelectric sensors to collect pulse signals, and developed a pulse mapping system based on the principle of photoelectric sensors. Since infrared rays can be absorbed by blood through the skin and blood vessels, and the blood volume in the blood vessels per unit length changes with the flow of blood, the amount of infrared rays absorbed depends on the amount of blood volume, with the help of photoelectric sensors to determine the change in blood volume, and then convert the received optical signal into an electrical signal, thereby reflecting the pulse information.
Some scholars and others have adopted waveguide-type optical sensor designs to detect pulse images more accurately than conventional methods using electrical signals, making it easier to form multiple channels and smaller devices. Some scholars also use photoelectric sensors to convert the changes in fingertip blood volume into electrical signals, so that the pulse waves are displayed and stored synchronously, and the accuracy of the pulse wave simulation model is proved.
Three / ultrasonic Doppler technology
Because the arterial pulse has pressure signal and acoustic signal information, there are also many information such as vascular volume and blood flow rate, and only the pressure sensor cannot fully reflect the elements that make up the pulse. Ultrasonic Doppler technology can detect many of these information in addition to pressure beats.
Takahiko Nakamura et al. provide an ultrasonic pulse detection device that can position the ultrasonic transmission piezoelectric element and the ultrasonic receiving piezoelectric element with high precision to resist fluctuations in mass and improve the sensitivity of pulse detection.
Wanton /microphone
The pulse of the inch mouth pulse can produce infrasound waves, and the microphone is based on the principle of acoustics to obtain the infrasound signal caused by the pulse vibration, thereby reflecting the pulse information, with good stability and reliability. The pulse detection system designed by scholars is based on the electret microphone, and uses two sensors to collect the pulse image at the same time, which finds that the acoustic signal of the microphone has a strong correlation with the first derivative of the standard pulse signal, which shows the feasibility of embodying the pulse information with the help of the microphone.
Woo /Soft contact sensor
This sensor uses a biomimicry method that simulates the pressure of a doctor's finger, and is commonly used as a sensor composed of latex film, air cavity, or sensing film and silicone oil. Japanese researchers such as Hitoshi Ishiyama used rubber gloves and semiconductor strain gages to detect and record pulse waves, thus measuring six pulse waves of young adults aged 20 to 40. Researchers have used soft, plastic conductive polymers to make sensors, develop non-rigid pulse imagers, and analyze pulse wave velocities to verify the feasibility of the system.
Sensor application scenarios
Pulser sensor application solutions include single probe, three probe and composite probe, but in clinical and scientific research, single probe sensors are more mature and widely used, and other types of sensors are less used. Since a single probe sensor can only reflect the pulse information of a single part (the customs department), it cannot be simultaneous
Reflects the three pulses of the inch-off ruler, so in recent years, multiple probes and composite probes should be
Scenarios keep coming up.
The application scheme of the sensor is concerned with the use of the pulse imager, and conformity with medical principles is its guiding ideology. Traditional pulse diagnosis pays attention to "three parts and nine waits", in order to find changes in visceral qi and blood, yin and yang, virtual reality, three parts are "inch, close, ruler", nine waits is each "floating, medium, sinking", so the single probe sensor application scheme increases the complexity of pulse diagnosis operation, but also increases the measurement offset caused by part changes, but the single probe program because of its complex problems of simplified design, easy to standardize the strategic positioning is still the first choice for the current TCM pulse diagnosis objectification research.
From the design point of view, the composite and multi-probe application scheme is more in line with the actual operation process of TCM pulse diagnosis, reflecting the multi-dimensional information of pulse image and simulating the real pulse diagnosis method, but the establishment of its pulse classification diagnosis algorithm still needs the support of a large amount of data, and even needs to be recognized by more industries.
Issues and outlook
Although the objectification of traditional Chinese medicine pulse diagnosis has been carried out for decades, and there are many types of pulse image instruments, it is still only used in scientific research, it is difficult to promote and popularize in clinical practice, and there are still non-uniform standards, high homogenization and operation
Problems such as high requirements and low reproducibility of test results. At present, the development and application maturity of single probes based on single-point pressure sensors is the highest, and standard advantages have been formed in the industry, groups and the world, but it is still necessary to provide deeper application solutions and accumulate more effective correlation data to provide support for scientific and accurate reflection and evaluation of human physiological and pathological conditions.
In the future, with the continuous progress and upgrading of sensing technology, and even the intervention of liquid metal sensors, the breakthrough of multi-source information fusion technology, and the iteration of big data and algorithms, TCM pulse research will surely make greater breakthroughs. Through the comprehensive and objective analysis of the pulse signal, in order to find its reaction in the state of certain lesions in human organs, and at the same time make this diagnostic method a more systematic, methodical, standardized and scientific advanced scientific system, and push the pulse diagnosis of Chinese medicine to a new stage from the surface.
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Source: Comprehensive "Application of Sensor Types and Schemes in TCM Pulse Detection", Zhihu
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