Abstract:
A method and a device for collecting data for posturography comprising a magnetizable body and an acceleration sensor are located on the platform, which magnetizable body and acceleration sensor are connected to a computer by means of an A/D converter. An electromagnet is located under the platform and is attached so as to be displaceable in two axes parallel to the plane of the platform, wherein the electromagnet is connected to an A/D converter and a power supply by means of a circuit, and a time-variable display, which is connected to the A/D converter, and a digital camera which are connected to the computer. By means of the method and the device it is now possible to standardize posturographic measurements, simultaneously detect the acceleration and the position of the platform, and more variably carry out provocations.

Description:
The invention relates to a method and a device for collecting data for posturography. 
     BACKGROUND OF THE INVENTION 
     Devices for posturography are used for determining the functional ability of balance regulation in the standing position, wherein, for example, the lower extremities are loaded by the action of a force. The devices according to the prior art comprise, for example, a swingable platform, on which healthy persons, serving as test subjects, patients, or animals, can stand. Such a swingable platform is connected at the corners thereof to springs. Optionally, such a device can be equipped with a mechanical provocation unit, which can be installed in one of the two horizontal axes of the platform. Such devices are known from the company Haider-Bioswing GmbH. 
     The devices according to the prior art have disadvantages, however. 
     The device according to the prior art does not permit intra- and inter-individual comparability of measurements within the scope of studies. 
     The movements of the platform are measured by means of an acceleration sensor, wherein the distance covered is calculated from the measured value in order to quantify the measurement. Calculation errors are therefore also induced. Depending on the orientation of the test subject, either only a lateral or a frontal provocation is possible. Combinations with deflections in both horizontal axes cannot be carried out. The provocation unit must be mechanically released so as to start measurement. Although the device according to the prior art can be used for therapeutic purposes, the device is neither intended nor suited for use in diagnostics. 
     SUMMARY OF THE INVENTION 
     Therefore, the object of the invention is to overcome the disadvantages of the prior art. In particular, standardization of the measurement during posturography should be made possible. Furthermore, detection of the platform movement by means of position determination, synchronously with the acceleration measurements, should be made possible. A device with which parameters or measurement data can be determined, for diagnosis of coordination impairments, should be made available. 
     By way of the method and the device according to the invention, it is now possible to standardize the posturographic measurements by standardizing the zero position of the starting position for the measurement, to limit calculation errors, and to permit provocation in the lateral, frontal and diagonal directions as well as in any direction and any intensity with respect to the test subject. Mechanical or manual release of the provocation unit can be eliminated. Use of the device for determining measurement data and/or parameters for diagnostic purposes is made possible. 
     The invention will be described hereafter in the general form thereof. 
     By means of the device and the method according to the invention, the balance functions of a test subject can be analyzed. A test subject within the meaning of the invention can be a healthy person, a patient, or an animal. 
     The device according to the invention comprises a swingable platform on which the test subject can stand. The swingability can be given by means of a suspension on springs. 
     The platform interacts with an electromagnet, which is preferably attached under the platform and can be switched on and off by means of a power supply via a circuit. The electromagnet is displaceable in two axes, which preferably extend perpendicular to one another, parallel to the plane of the platform. As a result, the platform is deflectable. For this purpose, the electromagnet can be mounted on two rails, which are stacked perpendicular to one another and allow a movement of the electromagnet in two axes extending perpendicular to one another. 
     The electromagnet is connected to a power supply. The power supply can be, for example, a power pack or a battery. 
     In one special embodiment, the platform can be located in a frame or a rack in which the platform is suspended with springs. 
     Located under the frame is a plate (a), which is fixedly connected to the frame or the rack so that the position thereof is fixed. 
     Located on this plate (a) are rails, for example, on which a further plate (b) is located. The plate (b) is then movable on the plate (a) in two opposing directions. 
     Located on the plate (b) in this special embodiment is a further plate (c), which is movable on the plate (b) on rails in two opposing directions, which extend perpendicular to the directions in which the plate (b) can move. The electromagnet is located on the plate (c). By way of such an arrangement, which is shown here by way of example, the electromagnet can be brought into a desired position underneath the platform. 
     The platform comprises a magnetizable body, for example, a ferromagnetic metal body, for example, in the form of a metal plate, which reacts to the magnet. The magnetizable body or the metal plate made from ferromagnetic material can be affixed, for example, onto the platform. Preferably, the metal body is fastened under the platform. 
     The device can also comprise a computer, which controls the switching on and off of the electromagnet. This can take place via an analog/digital converter card (A/D converter card) and a circuit. The power supply can be connected to the A/D converter or to the circuit. 
     Within the meaning of the invention, an A/D converter is intended to mean a converter, which has an interface with an A/D converter and a D/A converter. 
     Signals should therefore be capable of being converted from analog to digital and from digital to analog. 
     In addition, the device can comprise lifting means, which make it possible to lift the electromagnet. By way of these lifting means, the electromagnet can be guided toward the magnetizable body or the magnetizable plate. 
     An acceleration sensor, which is connected to the computer via the A/D card, is attached on the platform. 
     The platform is preferably equipped with at least one position marker, which makes it possible to detect the exact position of the platform. Advantageously, multiple position markers, for example, two, three, or four position markers, are attached on the platform. Three, four, or more position markers have the advantage that a plane can be defined, whereby the measurement becomes more precise. 
     The device comprises a digital camera. 
     The digital camera captures the position of the position markers on the platform. On the basis of these positions, the movement of the platform is captured in the image sequences. 
     In addition, the device comprises a time-variable display, which is captured by the digital camera. 
     The time-variable display can be a holder on which lamps are attached, the lamps generating different patterns at different points in time, which can be registered by the digital camera. For example, multiple LED lamps can light up in different patterns and/or colors in predefined temporal sequences. The time-variable display can also be a clock or a temporally varying pattern, which can be displayed by means of display panels. 
     The time-variable display is connected to the computer via the A/D card. 
     Preferably, at least one additional position marker is associated with the time-variable display, the position marker being imaged with the digital camera, which makes it easier for the computer to recognize the position of the variable time display. 
     The digital camera can image the movement of the test subject. 
     The figure schematically illustrates the device according to the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1 : shows a schematic illustration of the device. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a platform  1 , which is equipped with an acceleration sensor  2  and on which a magnetizable body  3 , in the form of a ferromagnetic metal plate, is attached. The acceleration sensor  2  is connected to an A/D converter  4 . The A/D converter is connected to a computer  5 . A position marker  6  is located on the platform  1 . A time-variable display  7 , which likewise has a position marker  8 , is also connected to the A/D converter  4 . The A/D converter  4  is connected to a circuit  9 . The circuit  9  is connected to a power pack  10  and to an electromagnet  11 . The electromagnet  11  is located on a plate  12 , which is displaceable in two axes and is positioned on a further plate  13 . In addition, the device comprises a digital camera  14 , which is connected to the computer  5 . 
     In the method according to the invention, the platform is initially fixed. 
     To this end, the electromagnet is supplied with current via the power supply and the circuit. 
     Preferably, the electromagnet is guided toward the electromagnetic body, which is located on the underside of the platform, by means of the lifting mechanism. As a result, a test subject standing upright on the platform is not exposed to great fluctuations. A defined zero position at the beginning of the measurement is therefore also ensured. Measurement can therefore be standardized. 
     The test subject positions itself on the fixed platform and assumes the desired posture. 
     When the measurement begins, the current is switched off, whereby the electromagnet is demagnetized. 
     If the current is switched off when the platform is in a rest position, provocation does not take place. 
     If a provocation is desired as the starting situation for the measuring process, the position of the electromagnet is changed before the switching-off, so that the platform moves into the desired starting position by means of the interaction between the magnetizable body and the electromagnet. 
     The electromagnet is switched off in the desired final position of the platform. An elongation with respect to the rest position is now present, proceeding from which the platform can swing. The switching on and off of the electromagnet can be controlled via the computer. 
     The test subject steps onto the platform ( 1 ) after the platform ( 1 ) has been fixed by means of the electromagnet ( 11 ). 
     Fixing of the platform by means of the electromagnet can take place in the zero position or in a deflected position. 
     Switching off the electromagnet in the deflected position results in a provocation. If the electromagnet is switched off when the platform is in the zero position, provocation does not take place. 
     Fixing the platform has the result that the starting position for the measurement is defined and the test subject proceeds from a rest position into a situation in which a provocation does not take place or, alternatively, in which a provocation is initiated. As a result, the method can be utilized for diagnostic purposes, because intra- and inter-individual comparability is ensured. For example, groups of persons of different ages or having different clinical profiles can be compared. 
     The measurement begins when the electromagnet is switched off. 
     The acceleration values are picked up by the acceleration sensor and are forwarded to the computer via the A/D card. 
     The digital camera captures the test subject, the platform with the position markers, as well as the time-variable display with the position markers associated therewith. 
     The image information of the digital camera is forwarded to the computer. 
     The measured acceleration data and the image information are stored. 
     Given that the acceleration and the position of the platform are measured independently of one another, calculation is not carried out. Possible calculation errors are therefore eliminated. 
     In a subsequent step, the computer associates simultaneous measurement data of the acceleration sensor and the digital camera with one another. 
     The computer preferably has pattern recognition software, which automatically recognizes the position markers or the platform in the images. The position markers, which can be recognized by the pattern recognition software, can be located on the platform, on the time-variable display, and/or on the test subject. In an alternative embodiment, the pattern recognition software can recognize the platform, the time-variable display, and/or the test subject without position markers. 
     The position of the platform is thereby detected. 
     The position of the time-variable display is recognized by the computer. By identifying the time-variable display, the computer can gather the time information, which is coded, for example, by means of lamps, LEDs, or another type of display, such as a clock, by means of suitable software. When lamps, such as LEDs, are used as the time-variable display, a multiplicity of lamps can be disposed next to one another, the lamps lighting up in a temporally varying pattern and making time assignment possible. 
     Preferably, the recognition of the time-variable display is simplified by means of the position markers associated therewith. To this end, the position markers are recognized by the computer. The position of the time display relative to the position marker is known and programmed. Therefore, the time information can be more easily identified. 
     As a result, the position data for the platform with the associated time information are available on the image data. 
     The data of the time-variable display, together with the data of the acceleration sensor, are forwarded via the A/D card to the computer and are stored. The time and acceleration data are therefore associated with one another. 
     The image information for a point in time and the acceleration data for the same point in time are therefore available. 
     In a further step, the image and the acceleration information for the same points in time are associated with one another. 
     Additionally, other signals can be measured, such as, for example, biological signals, for example, electromyogram and/or electrocardiogram and/or electroencephalogram. 
     In addition, non-biological signals, such as, for example, an audio signal, a signal from a clock generator, and/or a trigger signal can be measured by at least one other device. 
     For the case in which the sampling frequencies of the acceleration sensor and the digital camera are the same, the values must be associated 1:1. 
     For the case in which the sampling frequencies of the acceleration sensor and the digital camera differ, either the higher frequency would have to be subjected to a downsampling, or the lower frequency would have to be interpolated. Usually, a downsampling from higher to lower frequencies is carried out. 
     The movements of the test subject can likewise be imaged using the digital camera and forwarded to the computer. In this case, it is possible to attach markers at certain positions on the test subject, for example, at certain joint positions, the movement of which can be likewise imaged by the digital camera and forwarded to the computer. In addition, the test subject can assume a predefined posture with open or closed eyes. 
     The data obtained in this manner can be evaluated. 
     EXAMPLE 
     The invention is presented in the following by way of example but not in a limiting manner. 
     The system according to the prior art was enhanced with an electromagnet, an A/D converter, a Kinect camera, a webcam, and four position markers, whereby a standardized, computer-controlled measurement start is possible, and the acceleration of the platform can be detected by an acceleration sensor and the position thereof can be captured by a digital camera. The test subject and/or patient should perform exercises on the platform, which are typical for posturography (e.g., standing on both legs with open eyes and closed eyes or with the head tilted toward the back, standing on one leg, standing on both legs on a foam base with open eyes and closed eyes). In the developments, no irreversible structural changes were made to the main design of the platform, and therefore all parts are modular and can be removed again. The only change was to create holes (three on each corner, 12 holes in all) for additional screws in order to fix the electromagnet on the frame of the platform. 
     The electromagnet is mounted on a plate, which carries two rail systems, and can be deflected on two axes. This plate is located under the platform and is fastened thereto. The electromagnet is connected to the A/D converter, and therefore the activation/deactivation thereof can be controlled by means of a computer. Since the platform itself is not magnetic, a ferromagnetic plate (11.5 cm×10 cm×1 cm) was mounted (affixed) under the platform. The magnetization takes place by way of the power supply via a circuit. The synchronization of video images with the acceleration time series is carried out by means of a row of LEDs, which are sequentially activated/deactivated. The LEDs are located, together with their own position markers, on a separate holder, which is not fastened on the platform. These LEDs are automatically recognized in the video images. Since the LEDs additionally forward time stamps via the A/D converter card to the recording computer, synchronization of time series and video sequences is possible.