What Are the Different Types of EEG Equipment?

EEG machine is a bioelectric amplifier used to measure EEG signals. There are mainly video EEG, digital EEG and dynamic EEG.

Chinese name: EEG machine
Foreign name: Electroencephalograph

Management category: Class II medical devices
Category Name: EEG diagnostic equipment

EEG machine definition

It is a bioelectric amplifier used to measure brain electrical signals, which can assist clinical diagnosis of brain diseases.

EEG machine development history

In 1875, British surgeon Caton recorded the current directly in the exposed brain of the animal. The electrode was inserted directly into the skull of the monkey's head to detect the current activity in the brain.

In 1903, the German medical scientist Berger was inspired by these achievements and started the experiment of brain current recording with success. He named the method of recording human EEG as electroencephalography, which became the beginning of clinical application of EEG. .

In 1934, Adrian and Mateus improved electroencephalography so that it could diagnose certain types of epilepsy and insanity and tumors, as well as detect intracranial lesions and localize brain lesions.

It has been widely used in clinical diagnosis since the 1940s.

In 1950, Poser and Schubfrey began the application of EEG. This test is mainly used to assist the diagnosis of cerebrovascular disease.

The dynamic electroencephalograph was introduced in 1978. This technology has been widely used internationally and is a mature and effective diagnostic method. Compared with the traditional static EEG, the significant advantage of the dynamic EEG technology is that the dynamic EEG device can be used by the subject in daily living conditions, and complete recording of all EEG activities for 24 hours, and then by a computer The recorded data was replayed to regenerate the EEG activity of the occasional transient transient brain disorder, in order to determine the relationship between the onset and the environment, time, inducement and personal status ^[1] .

EEG machine works

The weak bioelectrical signal is picked up by the electrode, amplified by the amplifier, and then the graph is drawn by the recorder ^[2] .

EEG machine basic structure

The structure diagram is shown in Figure 1:

Figure 1 Schematic diagram of EEG structure

The input box is a metal shielded box. The scalp electrode leads are connected to the input end of the EEG machine through the input box. EEG machines on the market today generally buffer amplifiers in the input box to reduce noise. The lead selector enables selection of different leads and signal channels. Because the EEG signal is weak and the amplitude is extremely low, it is required that the EEG machine has a high amplification gain, so the EEG machine mostly uses multi-pole amplification technology to achieve its higher gain. A high common-mode rejection ratio is also required. There are also strict requirements on the stability of the power supply. Generally, when the power supply voltage fluctuates ± 10%, the output voltage change should be less than 0.01%, especially the power supply voltage fluctuation to the preamplifier stage should be less than 0.5V. The contact resistance between the electrode and the skin is directly related to the quality of the EEG recording. Generally, the contact resistance should be less than 20K. If it is greater than this value, the skin must be cleaned, the electrode should be treated or a better electrode paste should be used to ensure the accuracy of the measurement. Therefore, the EEG machine is provided with an electrode-skin contact impedance measuring device. Because the amplitude of the EEG signal changes greatly, it is required that the gain control can be adjusted in multiple gears ^[3] .

EEG machine common classification

Video electroencephalograph

Video EEG system

Simultaneous recording of video EEG and EEG, synchronized monitoring of EEG for more than 24 hours, can observe the patient's facial expressions and whole body movements, provide a basis for capturing seizures, accurately identify artifacts, facilitate doctor diagnosis, and play back the brain at high speed The radio wave can timely and comprehensively reproduce the normal, abnormal performance and corresponding brain wave changes in the entire process of the patient. 24-hour uninterrupted recording of the patient's EEG signals during awake, various activities and sleep, combined with high-definition video recording and playback of the patient's active images, which is helpful for clinical observation of the patient's movement status or sleep during the onset of illness When the action status. The features are: comprehensive understanding of patient information, more accurate identification of artifacts, and convenient direct observation of patients.

2. Digital EEG

Digital EEG

Full-featured integration of EEG detection magnification, computer analysis, and printing. Real-time brain wave monitoring, power spectrum analysis, dynamic topographic map, compressed spectrum array, potential analysis, parameter extraction, etc. 16-lead EEG signal acquisition, multiple lead combinations. It is a multifunctional instrument integrating EEG, brain topography and EEG monitoring. Features: strong scalability; high-precision, high-reliability USB interface EEG amplifier; multi-purpose dedicated trolley; stable system performance and high hardware configuration; powerful and comprehensive analysis software and functions; more convenient EEG playback function; human nature Case management functions.

3. Dynamic EEG

Ambulatory electroencephalograph

The dynamic electroencephalograph is a miniature cassette tape recording device carried by the patient, which can record all the EEG activity of the patient in real time for a long time in the process of the patient in the normal environment and engaged in daily activities. The EEG signal is recorded on a magnetic tape through a differential preamplifier, and the original recorded EEG image is reproduced through playback. It is used for the identification and diagnosis of epilepsy.

How to use the EEG machine

Environmental requirements

1) The EEG device should be placed in a shielded room to prevent external AC interference and ensure the stability of the EEG trace and clear waveforms.

2) The room temperature should be kept warm (not lower than 18 ) to avoid EMG interference caused by cold.

3) Unrelated personnel should not walk in the room, especially near the subject, to avoid magnetic interference caused by it.

2. Preparation

1) Explain to the examinee that the head should be washed with soap and water the day before the examination.

2) Subjects are required to stop taking sedatives, sleeping pills and antiepileptic drugs 3 days before the test.

3) The subject should eat on the day of the inspection, and should not be fasted.

4) For those who are the first time to be inspected, they should do a good job of explaining in advance to eliminate tension and better cooperate with the inspection.

3. Skin treatment and electrode placement

1) If there is dirt or excessive hair on the electrode site, clean the skin or shave the hair beforehand.

2) Apply conductive paste to the skin where the electrode is placed. Do not just apply conductive paste to the electrode. Avoid using cotton swabs or writing brushes to infiltrate normal saline or alcohol to replace conductive paste, which makes the polarization potential unstable and easily cause baseline drift or other artifacts.

3) Accurately place conventional 16-lead EEG electrodes in strict accordance with international uniform standards, and sphenoidal electrodes in special cases are placed according to uniform standards.

4) In order to judge whether there are other interference factors, the eye movement electromyogram and mandibular electromyography electrodes should be placed simultaneously.

4. Tracing EEG

1) Impedance, noise and paper speed should be adjusted before formal recording of EEG. Observe whether the calibration below the tracing chart is accurate, and adjust it if it is not appropriate.

2) Perform standard operation according to the instructions of the electroencephalograph. The routine includes Guide I, Guide II, Guide III and Guide IV. Guides V and VI can be added according to the application.

3) Patients with suspected epilepsy need to do excessive ventilation and flash stimulation to induce abnormal waveforms.

4) If most leads are normal and only one or two leads are straight, you should pay attention to whether the lead is not in good contact and you should reposition the electrode.

5) If the routine EEG cannot determine whether there is an abnormal waveform, 24-hour EEG monitoring should be performed to further clarify the correlation between EEG changes and clinical symptoms.

6) Complete EEG registration items. Establish an index book. After the inspection, register according to name, gender, age, clinical diagnosis, and EEG diagnosis. The EEG records should be in two copies. The original drawings should be archived with the report. To find when reviewing.

EEG machine routine maintenance

The storage and use place of the EEG machine should be relatively dry and clean, the temperature should not be too high or too low, the floor should be protected from vibration, and dust should not be allowed to enter the instrument. Cover it with a cloth cover when not in use. The electroencephalograph must be kept and used by someone. In addition, the following matters should be noted:

1. If the EEG machine is not used for a long time, it must be powered on regularly to drive off moisture and prevent rust. Generally, it is powered on once or twice a month for about one hour each time.

2. The ink used in the EEG machine is special. It is not suitable to use other writing inks to prevent the recording pen from being blocked. If the ink tank is found to be leaking, stop using it immediately and dispose of it in time. Pay special attention not to let the ink penetrate the recorder, so as not to adversely affect the performance of the recorder.

3. Pay attention to protect the stylus pen. In order to obtain a high frequency response, the stylus pen is always made light and light, but at the same time it also causes the pen to be not strong enough and easily damaged. During use, prevent overload signals from being applied to the recorder.

4. When recording, try to keep the baseline at the middle position. If you find that the circuit pen is aside, the guide record switch should be turned off in time, because the recorder coil has the highest current when the pen is aside Over time, the coil can overheat and even be damaged.

5. Be careful not to allow salt water to wet electrode leads, junction boxes, instrument panels, etc. If salt water is immersed in the junction box, it will reduce the insulation and cause AC interference.

6. Always check the chlorination of the electrode and perform a chlorination treatment after a period of use.

EEG machine extended reading

[1] Yang Jing, Li Xiangdong, Cui Yan. Analysis of detection methods of digital electrocardiograph [J]. Medical and Health Equipment, 2016, 37 (02): 106-108.

[2] Zhao Jijun. Factors that interfere with the use of ECG machines and their countermeasures. China Science and Technology Review, 2015, 0 (20); 70-70.