Sensor applications commonly used in the medical field

Computer technology, digital signal processing technology, and electronic technology have developed rapidly in recent years, and related fields have been promoted, and the development of the medical field has become more prominent. It can be seen that more and more high-tech electronic products appear in the field of medical technology, such as automatic biochemical analyzers, whole body gamma knife treatment systems, and multi-slice spiral CT and MRI. The application of sensors in the medical field is also the same. Very wide, the sensor can play an important role in sensing vital signs information, and is of great significance to promote the development of modern medicine. "One of the key scientific and technological projects of the Eighth Five-Year Plan" is the sensor, so researching sensors is the only way to develop contemporary medicine.

1 Sensor composition and classification

The sensor usually consists of two parts, a conversion element and a sensitive element. The sensitive component is the part that can directly respond or feel the measured, and the conversion component is the part that converts the measured signal into an electrical signal. According to the classification method currently in common use, sensors can be classified into two categories, such as biosensors, physical sensors, and chemical sensors, all of which convert input signals into electrical signals; and torque sensors and speed sensors. , flow sensors, gas sensors and viscosity sensors, etc., these are classified according to the output. All of the above are sensors that are more popular and widely used, and have broad prospects for development in the future.

In the past, doctors collected patient information in a relatively simple way, basically "seeking and asking" and simple checks. In the 1960s, China established medical engineering, and a variety of high-tech medical equipment was developed, which greatly enriched the way doctors collected patient information and improved the overall level of diagnosis and treatment. In the medical field, the sensor plays the role of "eyes and ears". The sensors are of various types and have different uses. According to the purpose of diagnosis and treatment, they can be divided into prevention sensors, inspection sensors, etc. According to different sampling methods, they can be divided into external sensors and internal sensors. According to the purpose of the inspection, it can be divided into a morphological sensor, a physiological function sensor, and a Linchuan chemical sensor. The purpose is different, the use is different, and the classification methods are not the same.

2 Biosensor applications

There are many test methods in medicine. The general method is to test in the laboratory. However, this test method is cumbersome and takes a long time, and it can not meet the needs of modern clinical medicine. The appearance of biosensors has greatly changed this phenomenon. . A biosensor is a kind of chemical sensor. The core part is a sensitive unit based on bioactive units such as cells, microorganisms, tissues, etc. The sensor captures the reaction between the primitive and the target and outputs it by electrical signals. Biosensors are widely used in the medical field because of their advantages of simple operation and less time.

2.1 Principle and structure

The sensor contains bioactive materials such as antibodies, antigens, proteins, DNA or enzymes. After the substances to be tested enter the sensor, the molecules recognize and then react biologically and generate information. The information is converted into sound and light by chemical transducers or physical transducers. Signals such as electricity and electricity, the instrument outputs the signal, and we can get the concentration of the substance to be tested. The main components of the sensor are the susceptor and the transducer, which can then be processed by automated instrumentation and microelectronics to form a variety of instruments or systems.

2.2 Classification and characteristics

According to the type of transducer, it can be divided into acoustic wave sensor, semiconductor sensor, thermal sensor, impedance sensor, etc. According to the classification of molecular recognition components, it can be divided into immunosensor, cell sensor and tissue sensor.

Traditional medical tests are mostly enzymatic methods. This method is cumbersome and costly. The biosensor method is expensive, but it can be used multiple times. Biosensors have strong transferability, that is, only specific The substrate reacts regardless of its turbidity and color. In addition, the analysis speed is faster, and the result can be obtained in one minute; the error can be controlled within 1%, the accuracy can be guaranteed; the operation is easier than the enzyme analysis method. Automated analysis is possible; biosensors are more efficient. All of the above are advantages of biosensors.

2.3 Use in the medical field

There are many types of biosensors, and the following is an analysis of the use of several of these sensors in the medical field.

2.3.1 Microbial sensors

The sensor of the microbial sensor is a membrane containing microorganisms. The working principle is that the microorganisms will consume dissolved oxygen in the solution to be tested, and release heat or light to achieve the purpose of quantitatively detecting the substance to be tested. Compared to enzyme sensors, microbial sensors are stable and less expensive to use, but they are used in less than enzyme sensors. The data shows that microbial sensors can detect about 60 to 70 substances. Microorganisms are affected by the toxic effects of the substance to be tested. This is the main factor affecting the accuracy and longevity of the sensor. This problem has been solved and the market for microbial sensors is just around the corner.

2.3.2 Enzyme sensor

The sensor's sensitive element is an immobilized enzyme, and the use of an enzyme sensor does not require a lot of effort to extract the enzyme. Clinically, biochemical indicators such as urea, glucose, lactic acid, and asparagine can be used to measure enzymes. For example, the current glucose enzyme sensor has been developed to the fourth generation, and its application range is wide, and the international lactate sensor technology is quite mature. Clinically, it is necessary to perform renal function diagnosis in order to test the renal function of the patient, and then perform manual dialysis in a targeted manner. In this case, a urea sensor is used. The enzyme sensor has a long research time and development time, and the number of enzyme sensors on the market has reached more than 200.

2.3.3 Gene sensor

Gene sensors are a kind of sensor that has emerged in recent years, but the technology is advanced. Many experts and scholars at home and abroad have researched on gene sensors, and now it has become one of the research hotspots. The basis of the gene sensor is high hybridization specificity. Generally, there are about 30 nucleotide single-stranded nucleic acid molecules on the gene sensor, and the target nucleic acid molecule is determined by hybridization with the target sequence. Nowadays, the genetic sensors that are researched and used more are DNA sensors, which are mainly used for the detection of Mycobacterium tuberculosis, HIV and hepatitis B virus, so as to achieve the purpose of diagnosing diseases.

3 fiber optic sensor applications

Propagating light is not the only use of fiber, it can also be used to exchange information. The fiber can combine various parameters with the to-be-measured to obtain the state of the signal under test and convert it into an optical signal output. Compared with traditional sensors, fiber optic sensors have faster response and high sensitivity. They do not generate electromagnetic interference during use. The fiber density is small, the confidentiality is good, and it is easy to save. Therefore, fiber optic sensors are used in many fields.

3.1 Principles and classification

The basic principle is that light enters the modulation zone through the fiber and then interacts with the measured parameters. The measured parameters change the frequency, intensity and phase of the light. The changed light passes through the fiber and outputs the measured physical quantity through the modulator. According to the sensing principle, fiber-optic sensors can be divided into two types, namely, sensing sensors and light-transmitting sensors; according to the measurement objects, they can be divided into flow sensors, position sensors, temperature sensors, image sensors, etc., which are widely used in the medical field. It is a light-transmitting sensor.

3.2 Application of light transmission sensor

Light-transmitting sensors have many advantages, such as insulation, small size, and are free from microwave and radio frequency interference. They are widely used in France, Japan, and the United States.

3.2.1 Measuring pH

The principle of measuring the pH value by using a light sensor is to measure the intensity of the transmitted light and the emitted light with the wavelength distribution, insert two optical fibers into the cellulose capsule, and then insert the needle into the blood vessel or tissue, and the reagent will Body fluid mixing, absorbing light of a specific wavelength, and then measuring the change using an analyzer, after which the pH of the tissue or blood can be obtained.

3.2.2 Measuring temperature

At present, microwave heating therapy is widely used at home and abroad to treat cancer, but the temperature of heating is difficult to control. If the temperature is too low, cancer cells may not kill, and if the temperature is too high, normal cells will be killed together, which has adverse effects on the human body. The temperature is 42.5 ° C to 45 ° C, so measures need to be taken to monitor the heating temperature, we can use the light sensor to achieve this purpose, has been developed is the use of lithium niobate crystal, due to the birefringence characteristics of the crystal and thus the temperature Very sensitive, although the fiber optic sensors currently used to measure temperature are still in the research stage, but the demand is large.

3.2.3 Transferring images

The principle is to combine multiple fibers to form a fiber bundle to achieve image transmission. Applying it to an endoscope can greatly increase the range of endoscope applications. This endoscope has the advantages of large degree of freedom, softness and small diameter. Therefore, the patient does not feel pain during use, and the light endoscope can also be used in normal medical fields such as polypectomy.

4 Temperature sensor application

Temperature indicators are very important in medicine. Doctors can rely on the temperature of various parts to diagnose diseases. For example, when diagnosing shock patients, they need to obtain their body surface temperature, while an elevated human body temperature may result in infectious diseases, such as Proper adjustment of the incubator can create a comfortable environment for newborns. These examples all show that the application of temperature in the medical field is very extensive, so the application of temperature sensors in medicine is equally important.

4.1 Types and applications of temperature sensors

4.1.1 Thermocouple

Back routing two different metal components, if the electric shock temperature is different, then there will be current through the loop, which is the principle of the thermocouple sensor. The advantages of this type of sensor are reliable, accurate, wide range and stable measurement, and are widely used in the medical field. For example, in the treatment of tumors, if the precise temperature control can enhance the effect of radiotherapy, the thermocouple sensor is used to control the temperature around the tumor to 43 °C, which improves the therapeutic effect of the tumor.

4.1.2 Thermal resistance

The main thing is to use a thermistor, which is a temperature-sensitive component that can be fabricated using a thermistor, such as a semiconductor thermal resistor and a metal thermal resistor. The advantages of the thermal resistance sensor are that the price is cheap, the reaction is fast, and the process is relatively mature. The thermistor used in the industrial industry in China is very extensive. Due to the sensitive and small size of the thermistor, it has also been widely used in medicine. For example, a thermistor can be packaged in glass or plastic to measure the temperature of the rectum, the mouth, etc., and a sheet thermistor is used to measure the body surface temperature. Thermal resistance sensors have broad prospects for development.

4.1.3 Thermal radiation

In fact, it is a thermoelectric transducer that uses a black surface element to absorb the amount of radiation, convert it into heat, and convert it into other parameters to become a parameter or a power. Commonly, it is a non-contact temperature sensor, for example, it is widely used during SARS. Infrared thermometer.

4.2 PN junction temperature sensor

Temperature affects the volt-ampere characteristics of the PN junction, so this feature can be used to create temperature sensors such as integrated circuit sensors, diodes, and triode temperature sensors. Among them, integrated circuit sensors are widely used, and peripheral circuits and temperature-transistor transistors are integrated on one chip. Compared to thermal sensors, integrated analog sensors are faster, more sensitive, and smaller, making them easy to carry and use.

4.3 Digital Temperature Sensor

Converting temperature to oscillation frequency is the principle of digital temperature sensors. Digital temperature sensors can be divided into intelligent temperature sensors and logic output sensors. Among them, the intelligent temperature sensor is also called intelligent temperature controller. It was invented in the 1990s. Now there are many kinds of intelligent temperature sensors in the world, which is the combination of computer technology and microelectronic technology. The intelligent temperature sensor is a combination of software and hardware, and its intelligence is also affected by the software level. The intelligent temperature sensor is small in size, anti-interference and has good precision. It can use the intelligent temperature sensor to build a multi-channel temperature measurement and control system for the ward, measure the body temperature in batches, and also have an alarm function. The logic output temperature sensor is the temperature switch. In many cases, we only care about whether the temperature is out of range. If there is such a requirement, we can use the logic output temperature sensor.

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