1. 6-10 Medical surface electrodes
Shuyi Wang

2. 6-10 Medical surface electrodes
Surface electrodes are those that are placed in contact with the skin of the subject．Also in this category are certain needle electrodes of a size that prevents their being inserted inside a single cell .
In any event, one must treat surface electrodes as a very high impedance（高阻抗） voltage source（电压源）— a fact that seriously influences the design of biopotentials amplifier input circuit.
VIASYS ECG MasterScreen Ergo Unit, 12-channel

3. Typical medical surface electrodes
in short-term ECG recording

4. Suction-cup electrodes
in short-term ECG recording

5. QDS ElectroCap
                                                                                                                                                                                                         The QDS ElectroCap consists of a headband with 10 openings for electrodes and a chin strap, and 3 cross straps with 3 openngs each. The headband can be rotated around the head in order to apply an electrode at any desired site. Electrodes can be applied at all 10/20 sites. The headband stretches to fit a range of head sizes. There are three sizes of ElectroCap. The Large fits heads cm in circumference. The Medium fits heads cm. The Small fits heads cm. The ElectroCap is used with conventional cup electrodes and earclips (not included). QDS recommends and we sell solid silver molded electrodes.
Strap带式 Electrode
The QDS ElectroCap consists of a headband with 10 openings for electrodes and a chin strap, and 3 cross straps with 3 openings each. The headband can be rotated around the head in order to apply an electrode at any desired site. Electrodes can be applied at all 10/20 sites. The headband stretches to fit a range of head sizes. There are three sizes of ElectroCap. The Large fits heads cm in circumference. The Medium fits heads cm. The Small fits heads cm.

6. A typical column electrode
For longer-term recording or monitoring—such as continuous monitoring of a hospitalized patient in a coronary or intensive care unit（CCU&ICU）, the paste-on column electrode is used instead.
Silver Chloride 氯化银 foam 泡沫塑料

7. Column electrode
The electrode consists of a silver-silver chloride（氯化物） metal contact button at the top of a hollow column that is filled with a conductive（传导的） gel or paste. This assembly is held in place by all adhesive coated foam rubber(海绵乳胶) disk.
The use of a gel-filled or paste-filled column that holds the actual metallic electrode off the surface reduces movement artifact.

8. Column electrode
A convenient form of column electrode often used in monitoring situations is the three-electrode pad. These adhesive pads have a surface area of 20 to 30 sq in. and contain three ECG electrodes (two differential signal pick-up electrodes and a reference electrode)in a single package.

9. Problems with surface electrodes
One of the problems with column electrodes is that the adhesive will not stick for long on sweaty or clammy（湿） skin surfaces.
The user also must avoid placing the electrode over bony prominences（骨骼凸起）.Usually, the fleshy portions（肉质部分） of the chest and abdormen are selected as electrode sites.

10. Movement artifact（人为影响）
One of the most significant problems is movement artifact which is generated by patient movements and consists of a small electrical component from the bioelectric signals in the patient’s skeletal muscles and a large component from the change in interface between electrode and skin.

11. Movement artifact
For short-term recordings, movement artifact is of little practical importance because most patients can lie still long enough for the recording to be made.
But in the intensive and coronary care units it is necessary to do long-term monitoring and recording of ECG signals, so the problem becomes more acute.

12. Electrode slippage（滑动）
The most common mechanism that creates artifact signals is electrode slippage.
If the electrode position slips, then the thickness of the layer of jelly or paste changes abruptly, and this change is reflected as changes in both the electrode impedance （电极阻抗）and the electrode offset potential.
The outward effect produces an artifact in the recorded signal that could possibly obscure（使不明显） the real signal or be interpreted as a bioelectric event in its own right.

13. Attempts to solve the movement artifact(1)
Sometimes adhesive tape is used to hold the electrode in place, and while this approach will work for a while, the electrodes inevitably（不可避免地） become loose. In an hour or two the problem returns.

14. Attempts to solve the movement artifact(2)
Another popular solution involves the use of a rough (prickly多刺的) surface electrode that digs in be low the scaly（有鳞的，劣等的） outer layer of skin. But these electrodes are often uncomfortable for the patient, and they fail to solve the problem completely.

15. Attempts to solve the movement artifact(3)
The column electrode does fairly well in overcoming the motion artifact, but even so it is often necessary for the medical staff conducting the test to clean and gently abrade（摩擦） the skin at the site where the electrode is attached.

16. Needle electrodes
Insulated 绝缘的
Handle 手柄
This type of ECG electrode is inserted into the tissue immediately beneath the skin by puncturing（刺破） the skin at a large oblique angle（斜角）.
The needle electrode is only used for exceptionally（异常的） poor skin, especially on anesthetized patients, and in veterinary situations.

17. Needle electrodes www.jarisupply.com/disposable-monopolar.html
Electromyography(肌电) is a test that measures muscle response to nervous stimulation. A needle electrode is inserted through the skin into the muscle. Each muscle fiber that contracts will produce an action potential. The presence, size, and shape of the wave form of the action potential produced on the oscilloscope（示波器）, provides information about the ability of the muscle to respond to nervous stimulation.
Update Date: 9/26/2006

18. Indwelling（留置） electrodes
Indwelling electrodes are intended to be inserted into the body.
In one application, the electrode is threaded through the patient’s veins (usually in the right aria) to the right side of the heart to measure the intracardiac（心脏内的） ECG waveform.
Sheath 鞘，外壳

19. In deep brain stimulation, electrodes are inserted into certain parts of the brain and are stimulated with the help of a pacemaker-like device.

20. Ambu Neuroline twisted pair subdermal（真皮下） needles feature low noise and impedance（阻抗） levels, delivering a clear and reliable signal every time.
Disposable(可任意处理的) non-coated stainless steel （不锈钢）subdermal（真皮下） needle electrodes with pre-attached color-coded lead wire.
Corkscrew （螺旋形）design keeps electrode in place during surgery.

21. EEG electrodes
The brain produces bioelectric signals that can be picked up through surface electrodes attached to the scalp（头皮）.
The typical EEG electrode may be a needle，but in most cases it is a 1-cm diameter concave（凹陷） disc made either of gold or silver．The disc electrode is held in place by a thick paste that is highly conductive, or by a headband in certain monitoring applications．

22. DISPOSABLE EEG DISC ELECTRODES
EEG disc electrodes feature a 2mm hole in the top for electrolyte（电解液） injection.

23. "Pin-type" Active electrode
The BioSemi “Pin-type” Active electrode has been designed especially for mounting in BioSemi headcap‘s. The electrode has a sintered（熔结的） Ag-AgCl electrode tip, providing very low noise, low offset voltages and very stable DC performance.
Standard sets have 32 electrodes on a common connector with 140 Centimeter cable length. (Other cable lengths are available on request.) The electrode is completely resistant to long term water and alcohol submergence（浸没） enabling easy cleaning and disinfecting（消毒）. The electrodes are numbered with water-proof stickers for easy channel recognition.

24. 128 channel Active-headcap
  The BioSemi headcap is a novel concept for high density EEG measurements. The plain cap only exists of the electrode holders. No electrodes or wires are attached to the cap. This allows for very fast placement of the electrodes according to the procedure described below. Preparation times as low as 30 minutes for a 128 channel EEG headcap are realistic. Because of the Active electrode principle, high electrode impedances（电极阻抗） do not influence the signal quality. Therefore, any skin preparation can be completely omitted. The location of the electrodes can be easily determined by the user, more info can be found in the "Make Cap Question"

25. 128 channel Active-headcap
Step3, Click Active electrodes into holders. (electrodes & holders are color labeled)
Step2, Apply electrode gel in holes. No further scrubbing of the skin necessary !
Step1，Place headcap over the head.

26. electroencephalogram
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The first recording of the electric field of the human brain was made by the German psychiatrist Hans Berger in 1924 in Jena. He gave this recording the name electroencephalogram (EEG). (Berger, 1929).(From 1929 to 1938 he published 20 scientific papers on the EEG under the same title "Über das Elektroenkephalogram des Menschen".)

27. Frequency spectrum （频谱）of normal EEG
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Frequency spectrum （频谱）of normal EEG
spontaneous activity,
evoked potentials, and
bioelectric events produced by single neurons.

28. EEG LEAD SYSTEMS
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The internationally standardized system is usually employed to record the spontaneous EEG. In this system 21 electrodes are located on the surface of the scalp, as shown in Figure 13.2A and B. The positions are determined as follows: Reference points are nasion（鼻根点）, which is the delve at the top of the nose, level with the eyes; and inion（枕骨突出）, which is the bony lump at the base of the skull on the midline at the back of the head. From these points, the skull perimeters（周长） are measured in the transverse（横断面） and median planes. Electrode locations are determined by dividing these perimeters into 10% and 20% intervals. Three other electrodes are placed on each side equidistant from the neighboring points, as shown in Figure 13.2B (Jasper, 1958; Cooper, Osselton, and Shaw, 1969).

29. EEG LEAD SYSTEMS
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30. EEG LEAD SYSTEMS
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Location and nomenclature(名称) of the intermediate 10% electrodes, as standardized by the American Electroencephalographic Society. (Redrawn from Sharbrough, 1991.).

31.
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