Surgery – Diagnostic testing – Cardiovascular
Reexamination Certificate
2000-10-03
2004-02-17
Evanisko, George R. (Department: 3762)
Surgery
Diagnostic testing
Cardiovascular
Reexamination Certificate
active
06694178
ABSTRACT:
The invention relates to a method and a device for representing and monitoring function parameters of a physiological system, in particular electrocardiographic data, which are derived from electronic measuring signals.
Since the discovery of the action currents of the heart in 1887, data determined have been recorded using electrocardiography. After the initial use of the string galvanometer in conjunction with a paper strip with a light-sensitive coating for the purpose of detecting the action potentials, recording measuring units have been in use for several decades. In these measuring units, recording means comparable to a plotter execute a linear movement as a function of the amplified measured values, a paper strip being guided along perpendicular to the movement of the recording means and below the latter.
This produces a curve which has a typical, periodically repeating characteristic. With the aid of this curve, an educated and trained cardiologist can detect changes in the impulse formation, dysrhythmias or damage to the heart muscle. A disadvantage of this type of representation is that, particularly in the case of small changes, the information content can be detected only with difficulty, and that special training and wide experience are required to interpret the curves. Furthermore, a not inconsiderable period is required for careful evaluation of an electrocardiogram.
In the further development, the curve was represented on a display screen, and this rendered possible a substantially refined representation, since the electron beam has a lesser inertia than the recording unit, and therefore operates virtually without delay. A brief representation of the curve and the limited resolution on the display screen are disadvantageous here.
The two-dimensional representation led to the development of vector cardiography, in which the action currents of the heart muscle fibers are recorded in such a way that loops are produced in the three planes in space, only trained specialist staff being capable of carrying out interpretation of the space curves.
U.S. Pat. No. 5,215,099 discloses a device and a method for predicting cardiac dysrhythmias, in the case of which a multiplicity of ECG measurements of the QRS region are averaged, and atypical waveforms are rejected. The average values of the ECG measurements are subsequently digitized, the segments are shifted in time relative to one another, analyzed and transformed by means of a Fourier transformation. The transformed data are expressed in a three-dimensional form, it being possible to infer a low risk of infarct when the temporally displaced segments correspond to one another.
Various methods for representing surface potentials are described in the articles “A microcomputer-based cardiac mapping system for tachycardia surgery”; Moura et al., “A system for accurate interactive 3-D display of cardiac electrical activity” Branham et al., “A real-time data acquisition system for the display of three dimensional cardiac activation maps”; Young et al., and “3-D mapping of body surface potentials”; Calderon et al.; although they permit positionally accurate assignment of the measuring points their evaluation requires experience, however.
The object of the present invention is to provide a method and device which quickly and in a fashion which can be used by anyone render it possible to analyze the variation in process states and to predict future states.
This object is achieved according to the invention by means of a method in accordance with claim 1 and a device in accordance with claim 17.
The word information microscope is illustrative both of the method according to the invention and of the device for carrying it out, since available information which is not immediately available to a viewer is brought to human perception. In the case of a light microscope, very small structures of matter are rendered visible by refraction of the light waves in a lens system. The information microscope provides function parameters of a physiological system in such a way that these are made acceptable per se to general perception, and that extremely small variations become clear.
The interpretation of complex information such as is contained, for example, in an ECG is substantially simplified and accelerated by the method according to the invention. Frequent data acquisition is possible because of the very short measuring period and the simple application, with the result that it is possible to observe a variation in a physiological system by measuring at short intervals over a long period.
The short evaluation period and the simple interpretability of the measured values provided also reveal very small variations. Predictions relating to the physiological system under investigation are possible in conjunction with the possibility of qualitatively estimating the measured values represented.
Conversion into a graphical portrait produces an individual mapping of the system under investigation with the aid of which identification is possible, as in the case of a photograph.
The graphical portrait is advantageously constructed in the manner of a three-dimensional topological model, since it is possible to transmit the highest information density with the aid of this representation, which comes closest to the natural perception of the environment. Thus, even complex measured values can be represented in a way which is graphic and easily accessible. Likewise, small deviations which could be identified only with difficulty in a two-dimensional diagram become perceptible through this type of representation because of the larger information quantity. Like a map, in which the topological conditions are visualized by an appropriate arrangement, the three-dimensional model conveys a view of the function parameters with great vividness and a high information density.
The digitization of the data permits regions previously plotted longitudinally to be assigned to space coordinates, thus achieving a three-dimensional effect. Starting from a significant measured variable, specific sections of the measured value characteristic are assigned specific spatial areas. The analog signal is digitized, and the value is used, as a function of its temporal occurrence, as an interpolation point for forming a largely closed surface. In addition, the individual interpolation points are stored with a color code which comprises both chrominance and luminance. This color code storage is performed on the basis of the measured values of in each case one analysis cycle, and permits qualitative orientation with the aid of the color values and brightness values of the image.
The analysis cycle is advantageously fixed by determining the temporal spacing of at least two repeating significant variables, the variables being a function of the physiological conditions and/or of the body part under examination. In the case of cardiological examinations, the interval between two R impulses is suggested as the length of an analysis cycle, since this is easy to determine and has a satisfactory edge steepness as a rule. The analysis cycle is fixed in this case in such a way that the significant action potentials of the heart muscle are detected, and therefore that the entire range from P to T is covered.
In order to increase the accuracy and informativeness of the measurement, and to increase the precision of the representation, it is advantageous to have a measuring period which covers a multiple of an analysis cycle. Since the discrete values of he digitized measurement correspondingly are assigned according to their sequence to specific zones inside the pictorial representation, a measurement over a time interval which contains the entire range of the values to be taken into account is favorable.
It is particularly advantageous that the assignment of color codes is calculated by combining empirically determined reference data. On the basis of data which are stored in an electronic memory and can be called up therefrom, the interpolation points are assigned information with reference t
Gillessen Werner
Kitachine Youri
Soula Anatoli
Christie Parker & Hale LLP
Energy-Lab Technologies GmbH
Evanisko George R.
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