Carstens Medizinelektronik

Tips & Tricks

The Information given herein is, to the best of our knowledge, correct. However, this material is intended to be purely descriptive and is not intended to imply a warranty of any kind.

The clinical use of Electromagnetic Articulography (EMA)
Sensor handling
Glue for Sensors
Coating for Sensors

Software tools for system check and maintenance

The clinical use of Electromagnetic Articulography (EMA)

General remarks
Fixation of the measurement sensors
Examination of the lip kinematics
Examination of the tongue kinematics
Hygienical measurements

General remarks:

The receiver sensors have to be positioned, so that they are parallel to the axis of the transmitters on the helmet. The midsagittal plane and the axis of the transmitter and receiver-coils (sensors) form a right angle. Any displacement of the receiver coils out of the midsagittal plane has an adverse effect on accuracy.
Before beginning the examination of an articulator on a patient, it should be examined if and to which extent the concerned structure performs transversal or rotation movements during speech or swallowing. For example, a sidewise movement of the tongue is not uncommon in hypoglossus nerve paralysis. In such cases, the extent of sidewise movement should be determined when using EMA.
Lateral movement of the sensors from > 10mm has clinically relevant influence on measurement errors. Rotation of the articulators by more than 30° also leads to artifacts and absolute and relative measurement errors.


Fixation of the measurement sensors

A drop of Cyano-Vemeer or Histoacryl is applied to the sensorin order to fix them on the skin - and mucous membrane. The sensor is pressed upon the dry surface for a few seconds with anatomical forceps, being careful to align the axis properly.
When fixing the sensors on the oral mucous membrane, the use of a cotton swab or an airstream to dry up the mucous membrane is recommended. If the incisors are used as a reference point, a temporary sealant such as Temp-bond may be used.
Depending on the surface movement, the sensors remain affixed for up to one hour. Adherence to the surface of the tongue and the outer skin is stronger than to the mucous surface of the mouth because of the surface structure.
To fix the sensors to the soft palate for a longer examination, an atraumatic suture under local anesthetic should be taken into consideration. The positioning of the sensors normally depends on the clinical or scientific question to be studied. Depending on the indication, the following sensor-combinations have been found to be useful.


Examination of the lip kinematics

Upper lip sensor: median immediately cranial to the lip red-white borderline

Lower lip sensor: immediately caudal to the lip red-white borderline.

As reference points, further sensors are fixed directly subnasal and over the point of the chin in a area of little movement.


Examination of the tongue kinematics

In case of a question concerning the surface movement of the tongue during articulation and swallowing, 5 sensors are placed medial 10mm apart starting 10mm from the tongue tip in the region of the sulcus medianus.
In combination with other sensor positions, experience has shown that at least one sensor in the region of the tip of the tongue and one further back are needed, since the tip of the tongue and the dorsal region show different movement in speech and swallowing. Combinations with sensors positioned on the lower jaw and at the velum may be considered depending on the question to be studied.
The lower jaw may be studied using a point on the mucous membrane in the region of the median anterior vestibule. Supplementary sensors on the outer skin of the chin may also be used.
Positioning sensors at the incisal point of the lower jaw is generally not possible because of the vertical overbite. For reference points sensors can be fixed to the upper jaw either in the vestibulum or in the region of the mesial incisors.
The use of Cyano-Vemeer or Histoacryl on composite dental filling material or crowns is to be strictly avoided. The soft palate has to be examined from a distal third near the margin. A deduction anterior of the velar knee (velar dimple) does not seize the maximal movement track and so it is to be avoided.
During short examinations, the use of Cyano-Vemeer or Histoacryl after drying up the velum with a cotton swab is sufficient. During longer examinations, a sensor can be covered with little lateral perforate extensions, "buttonholes" of Palador, a self-hardening acrylic material. Under local anaesthesia the sensor will then be fixed to the mucous surface with an atraumatic suture (f.i. silk 4-0). This should be done by a doctor who has the experience. In this case it is an assumption to work sterile.


Hygienical measurements

Before usage all of the sensors must be sterilized (f.i. Gas-sterilization with Äthylenoxid). Before the examination starts, the sensors can be covered with a gum solution (plasty-late), which can simply be removed after the examination and keeps the sensor on clean condition. After cautious but careful cleaning of the sensors under conditions recommendet for surgical instruments the sensors may be sterilized again.


Sensor handling

It is possible to mark on the tongue with lipstick. Placing pellets at an exact location is difficult, but one can put a small mark next to the place where the pellet should go, and things are easier.

Phil Gleason,

1. In our investigations, we use cyanoacrylate glue for coils attached to the tongue and upper incisors.
For externally-mounted coils (e.g. lips, jaw, secondary reference coil at bridge of nose) we use Skin-Bond, a rubber glue manufactured by Smith and Nephew (1-800-876-1261). This company also manufactures "Uni-solve," an adhesive remover useful for cleaning the receiver coils at the end of an experimental. Uni-solve is sold in 8-oz cans (the cheapest way to go!) or individual, moistened towelettes.

2. One difficulty we've encountered is a loss of receiver coils due to broken leads at the coil base. This usually occurs as the result of the repeated dipping (in Plastylate) and cleaning these coils require. We have been able to reduce this damage by occasionally dipping the stripped-down coils in cyanoacrylate glue. up as far as the sleeve. This strengthens the base and reduces breakage.

William Katz,

Please see also "Coating for sensors" with plasty late or with shrinkable tube


Glue for sensors


For fixation of the measurement sensors inside the mouse.
delivery form:
Package with 4 ampoules 3g each
Order-No. ACVEN001

Medizin- und Dentalhandelsgesellschaft GmbH
Postfach/P.O. Box 2069

D-61440 Oberursel - Germany

Phone *(49) 6171 570 88
Fax: *(49) 6171 563 22



For fixation of the measurement sensors inside the mouse.
delivery form:
Package with 5 ampoules 0.5g each
Cat. No. 105 005/2

B.Braun Melsungen AG
Woundhealing Division
P.O.B. 110 + 120

34212 Melsungen - Germany


Coating for sensors


Plasty-late is a natural-rubber-based, stabilized, liquid moulding compound which is prevulcanized and therefore ready for use.
Plasty-late has proved a success already for several years in industrial manufacture of gummos moulding
(figures, gleves, bathin-caps etc.).

The sensors can be covered with plasty-late, which can simply be removed after the examination. and keeps the sensors on clean condition.

bastel-system gmbh

D7995 Neukirch/Bodensee - Germany

Shrinkable tubing as cover material

This user tip concerns an alternative to the latex method to cover the AG100 coils and has two advantages as compared to the latter:

  1. The material doesn't need to dry for a certain period of time
  2. It can be removed fairly easy, when applied with care as described below, without a risk of damaging the coils.

The method consists of using shrinkable tubing as cover material. Regarding the shrinkable tubing, one can use the standard material that is used for electronics, with the following specifications:

One can use a paintstripper heater (hair dryers won't do!) to shrink the tubing. One can also buy special devices for this as well, but they are more expensive. One only needs to heat the coil covered by the tubing for a few seconds, but keep the wire of the coil out of the heat.
Also, before applying the tubing to the coil, one has to put a little mineral jelly on the coil (this makes removing the tubing even easier after the experiment, especially if one has put a thin layer of super glue on the coils to protect them, as described by Prof. Katz on this site).
It is important not to leave an opening at the front part of the coil (excessive glue may enter). By using a pair of pliers, one can bring the open ends of the tubing together immediately after the heating and cut off the excessive parts.

P.S. To remove the tubing material one needs a very small pair of scissors (e.g., a knee bended type with a cutting size of .5 cm used for surgery or tissue preparation) to make a small cut along the length side of the coil. This way the cover can be opened and the coil can be squeezed gently out of it.

Succes with your measurements!

Pascal van Lieshout, Toronto

Software tools for system check and maintenance


Points.exe is a program to check the system accuracy, noise and the actual calibration.

Tools ( load: agset1.exe - 496397 Byte)

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