JP2020065824A - Cardiac potential simulation method and apparatus - Google Patents

Abstract

To provide a cardiac potential simulation method that makes it possible to easily perform cardiac potential simulation using a commercially available computer or the like.SOLUTION: In step S101, an electric signal source is disposed on a three-dimensional human body model imitating a human body at a predetermined location of a part of the heart of this model. The electric signal source is an electric dipole, for instance. Next, in step S102, a body surface potential derived from the electric signal source is obtained. The body surface potential is obtained through electromagnetic field simulation. Steps S101 and S102 are repeated by sequentially changing a position of the electric signal source to a set measurement location at each set time (step S104). After having obtained the body surface potential at every measurement location (yes in step S103), the operation is ended.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electrocardiographic potential simulation method and apparatus for simulating a state of a heart to reproduce an electrocardiographic potential.

Measuring heart rate variability is useful for controlling the load intensity of cardiopulmonary function. In recent years, wearable devices have been developed that can measure electrocardiogram by incorporating electrodes into clothes such as shirts, and heart rate variability is monitored and observed in various situations. In the development of wearable devices that measure such cardiac potentials, the location of the electrodes is important. As a method for determining the electrode arrangement for measuring the cardiac potential, for example, there is a technique using a heart simulator. In recent years, with the improvement of computer performance, a heart simulator that reproduces behaviors at the molecular / cellular level to blood pressure / electrocardiogram has been developed. By reproducing (simulating) the electrocardiogram waveform using a heart simulator, it becomes possible to determine the optimum electrode installation location.

Introduction of research Outline of heart simulator, UT-Heart Laboratory, University of Tokyo, [Search on August 13, 2018], (http://www.sml.ku-tokyo.ac.jp/report/report01a. html). Study on high-precision exposure assessment technology-Development of numerical human body model-, living body EMC, [August 15, 2018 search], (http://emc.nict.go.jp/bio/model/model01_1.html ). J. Malmivuo and R. Plonsey, Bioelectromagnetism: principles and applications of bioelectric and biomagnetic fields, Oxford University Press, pp. 188-191, 1995. R. E. Klabunde, Cardiovascular physiology concepts, Second Edition, Philadelphia: Lippincott Williams & Wilkins / Wolters Kluwer, pp. 21-23, 2012.

  However, the above-described heart simulator requires a large-scale computer called a so-called super computer, and there is a problem that it is not easy to reproduce the cardiac potential.

  The present invention has been made to solve the above problems, and an object of the present invention is to make it possible to easily carry out a simulation of an electrocardiographic potential with a commercially available computer or the like.

  The cardiac potential simulation method according to the present invention is set with the first step of changing the position of the electric signal source arranged at the heart portion of the three-dimensional human body model simulating the human body at every set time. The second step of obtaining the body surface potential derived from the electric signal source for each position of the electric signal source changed with time, and a waveform simulating the cardiac potential from the distribution of a plurality of body surface potentials obtained with time And a third step of

  In the above cardiac potential simulation method, the second step is, for example, to obtain a body surface potential in the chest lead.

  In the above-described cardiac potential simulation method, in the first step, the change distance of the position of the electric signal source may be changed between the atrium and the ventricle.

  In the above cardiac potential simulation method, the electric signal source is an electric dipole. Further, in the second step, the body surface potential is obtained by electromagnetic field simulation.

  A cardiac potential simulation device according to the present invention is an implementation of the cardiac potential simulation method described above.

  As described above, according to the present invention, it is possible to obtain an excellent effect that the simulation of the cardiac potential can be easily carried out by a commercially available computer or the like.

FIG. 1 is a flow chart for explaining a cardiac potential simulation method according to the embodiment of the present invention. FIG. 2 is an explanatory diagram illustrating a human body model. FIG. 3 is a waveform diagram showing standard electrocardiographic waveforms in the chest leads V1 to V6 shown in FIG. FIG. 4 is an explanatory diagram for explaining an example of the location of the electric dipole. FIG. 5A is an explanatory diagram showing a series of body surface potential distributions calculated while sequentially changing the position of the electric dipole as shown in FIG. FIG. 5B is an explanatory diagram showing a series of body surface potential distributions calculated while sequentially changing the position of the electric dipole as shown in FIG. FIG. 5C is an explanatory diagram showing a series of body surface potential distributions calculated while sequentially changing the position of the electric dipole as shown in FIG. FIG. 6 is an explanatory diagram for explaining the calculation of the propagation time. FIG. 7 is a characteristic diagram showing an example of a waveform simulating an electrocardiographic potential obtained by the electrocardiographic potential simulating method of the present invention by the location of the electric dipole shown in FIG. FIG. 8: is explanatory drawing for demonstrating the other example of the location where an electric dipole is arrange | positioned. FIG. 9 is a characteristic diagram showing an example of a waveform simulating an electrocardiographic potential obtained by the electrocardiographic potential simulating method of the present invention by the location of the electric dipole shown in FIG. FIG. 10 is an explanatory diagram showing a series of body surface potential distributions calculated while sequentially changing the position of the electric dipole as shown in FIG.

  Hereinafter, the cardiac potential simulation method according to the embodiment of the present invention will be described with reference to FIG. First, in step S101, an electric signal source is arranged on a three-dimensional human body model imitating a human body at a predetermined position of the heart of the model. The electric signal source is, for example, an electric dipole. Next, in step S102, the body surface potential derived from the electric signal source is obtained. The body surface potential is obtained by electromagnetic field simulation.

  The above-described steps S101 and S102 are sequentially changed and repeated at the set measurement location every time the position of the electric signal source is set (step S104). When the body surface potentials at all the measurement points are obtained (yes in step S103), the operation ends.

  As described above, according to the electrocardiographic potential simulation method of the present invention, the position of the electric signal source arranged in the heart portion of the three-dimensional human body model imitating the human body is changed every set time (first step). , The body surface potential derived from the electric signal source is obtained for each position of the electric signal source changed at each set time (second step). From the distribution of the plurality of body surface potentials obtained at each time This is to obtain a waveform simulating the cardiac potential (third step).

  Further, the electrocardiographic potential simulation device of the present invention is configured by a computer that implements the above-described electrocardiographic potential simulation method. The computer is a computer device that includes a CPU (Central Processing Unit), a main storage device, an external storage device, and the like. Each function is realized. Further, each function may be distributed to a plurality of computer devices by using a network connection device.

  For example, a human body model as illustrated in FIG. 2 is used. This human body model is a voxel model that is composed of 51 types of tissues such as skin, muscle, and heart, and has a resolution of 2 mm (see Non-Patent Document 2). Physical properties such as conductivity of each tissue used when the body surface potential is obtained by electromagnetic field simulation should be values that actually match, and can be appropriately set by the person who performs the calculation. The conductivity of each living tissue used for the calculation is shown below.

  As well known, V1 to V6 shown in FIG. 2 are positions of the chest lead (electrode) when measuring an electrocardiogram. Typical electrocardiographic waveforms for these chest leads V1-V6 are shown in FIG. From V1 to V6, the main direction of the QRS wave in the electrocardiographic waveform changes from minus to plus. In the calculation example described later, the waveform observed at this position is obtained. The computer used for the calculation of the calculation example described later uses two "Xeon (registered trademark) Gold 5120 (2.2 GHz)" manufactured by Intel Corporation for the CPU, and the main memory is 96 GB.

  Next, the location of the electric signal source (electric dipole) will be described with reference to FIG. It should be noted that FIG. 4A shows a cross-sectional view of the heart, and shows the extracted heart portion of the calculation model in a form corresponding to the cross-sectional views of FIGS. 4B and 4A. Further, in FIG. 4B, the positions where the electric dipoles are sequentially arranged are indicated by "◆". The body surface potential is calculated by electromagnetic field analysis using a minute current generated by placing an electric dipole as an input source. The electromagnetic field analysis may use, for example, the SPFD (scalar-potential fine-difference) method. The amount of electric charge of the electric dipole is set by the person who performs the calculation in consideration of the amount of electric potential to be generated. In this calculation example, the charge amount was set to 0.1 mC. Note that a plurality of electric dipoles may be placed in the heart at the same time, but in this case, the total charge amount is set to 0.1 mC.

  As the configuration of the electrocardiogram, first, the body surface potential when a single electric dipole arranged at a position on the surface of the heart portion of the human body model is used as an input source is calculated by the SPFD method. As described with reference to FIG. 4, a series of body surface potential distributions calculated by sequentially changing the position of the electric dipole are shown in FIGS. 5A, 5B, and 5C.

  Here, the propagation time of the electric excitement is obtained by using the propagation speed of the electric excitement and the moving distance between the electric dipoles. The propagation speed of electrical excitement was set as shown in the following table (see Non-Patent Document 3 and Non-Patent Document 4).

  By integrating the potentials corresponding to the target chest leads (V1 to V6) on the calculated body surface potential distribution on the time axis in correspondence with the propagation time obtained by the post-processing as shown in FIG. , Configure the electrocardiogram.

  Explaining the calculation of the propagation time, the positions of two electric dipoles that are continuous in time (time series) are set to x1 and x2, respectively, and the body surface potential at the target induction position as each input source is expressed as φ1 and φ2. Letting t1 be the time when the body surface potential is φ1, and Δt be the value (time) obtained by dividing the distance | x2-x1 | between the moved electric dipoles by the propagation time, the time t2 when the body surface potential becomes φ2 is , T2 = t1 + Δt. Thus, by plotting the body surface potentials obtained for each electric dipole in time series, a waveform simulating the cardiac potential can be obtained.

  The position of the electric dipole indicated by “◆” in FIG. 4B is moved along the arrow, and the body surface potentials in the chest leads V1 to V6 obtained by the electromagnetic field simulation are calculated on the time axis as described above. The waveform obtained by aligning with is shown in FIG. First, a shape close to the approximate shape of the P wave in the electrocardiogram waveform can be simulated. Further, in V4 to V6, the shape close to the abrupt potential change, which is the characteristic of the QRS wave, can be simulated as shown in FIG.

  Next, another calculation result example will be described. Here, as shown in FIG. 8, the position "◆" of the electric dipole is moved. Further, here, the moving distance between the electric dipoles is changed between the atrium and the ventricle. The movement distance between electric dipoles is 3.2 mm on average in the atrium and 24 mm on average in the ventricle.

  The position of the electric dipole indicated by “◆” in FIG. 8 is moved along the arrow as described above, and the body surface potentials in the chest leads V1 to V6 obtained by the electromagnetic field simulation are set on the time axis as described above. FIG. 9 shows the waveform obtained by aligning with. It can be seen that the main direction of the QRS wave shown in FIG. 3 can simulate the transition from the S wave to the R wave in all the leads V1 to V6. As described with reference to FIG. 8, FIG. 10 shows a series of body surface potential distributions calculated by sequentially changing the position of the electric dipole.

  In the above-described calculation example, the body surface potential in the chest lead is obtained, but the invention is not limited to this, and the body surface potential is obtained at any place on the three-dimensional human body model. Good. For example, the body surface potential in limb guidance may be obtained.

  As described above, according to the present invention, the position of the electric signal source arranged in the heart part of the three-dimensional human body model imitating the human body is changed every set time, and the electric signal source is changed. The body surface potential derived from the electric signal source was obtained for each position, and the waveform simulating the cardiac potential was obtained from the distribution of the plurality of body surface potentials obtained for each time. As a result, according to the present invention, the simulation of the electrocardiographic potential can be easily performed by a commercially available computer or the like. Further, according to the present invention, the distribution of the body surface potential can be calculated over the whole body, and the cardiac potential simulation over the whole body becomes possible.

  The present invention is not limited to the embodiments described above, and many modifications and combinations can be implemented by a person having ordinary knowledge in the field within the technical idea of the present invention. That is clear.

Claims (6)

A first step of changing the position of an electric signal source arranged at the heart part of a three-dimensional human body model simulating a human body at preset times;
A second step of obtaining a body surface potential derived from the electric signal source for each position of the electric signal source which is changed every set time;
And a third step of obtaining a waveform simulating an electrocardiographic potential from a distribution of a plurality of body surface potentials obtained for each time. The cardiac potential simulation method according to claim 1,
The second step is a method of simulating an electrocardiographic potential characterized in that a body surface potential in chest lead is obtained. The cardiac potential simulation method according to claim 1 or 2,
The said 1st step is a cardiac potential simulation method characterized by changing the change distance of the position of the said electric signal source between an atrium and a ventricle. The cardiac potential simulation method according to any one of claims 1 to 3,
The cardiac potential simulating method, wherein the electric signal source is an electric dipole. The cardiac potential simulation method according to claim 4,
In the second step, a cardiac potential simulation method is characterized in that the body surface potential is obtained by electromagnetic field simulation.   An electrocardiographic device which implements the electrocardiographic simulation method according to claim 1.