CARDIOLOGY SYSTEM WITH ELECTRICALLY ISOLATED MEASURING HEAD

Abstract: The present invention relates an electrocardiography system having an isolated measurement head from which are electrodes attached to a patient so that the accuracy of the electrocardiographic test may be improved without an electric shock. An electrocardiography according to the present invention comprises: a measuring head for receiving electrocardiographic signals sensed by the sensing electrodes and for generating difference voltages signals from the received electrocardiographic signals, wherein the isolated measuring head is driven by a first power supply; a transmission link for transmitting the difference voltage signals; and an induced voltage generator for receiving difference voltages signals via the transmission link and for generating induced voltage signals, wherein the measuring head is electrically isolated from the induced voltage generator and wherein the induced voltage generator is driven by a second power supply.

Description: CARDIOLOGY SYSTEM WITH ELECTRICALLY ISOLATED MEASURING HEAD Technical Field The present invention relates to an improved cardiology system which displays and records electrocardiographic signals; and, more specifically, to an electrocardiography system having an electrically isolated measurement head from which electrodes are to be attached to a patient so that the accuracy of the electrocardiographic test may be improved and radically eliminate an electric shock. Description of the Prior Art Electrocardiography system has become an important diagnostic tool for the medical profession. Moreover, recently it has become important when coupled with the administration of a stress test in conjunction with a treadmill, or the like. Such stress tests are performed not only on patients who have a history of cardiac disease, but also on otherwise healthy patients during a general examination or during an examination related to another physiological problem. Typically, in such electrocardiography systems, a large number of electrode leads are connected to the patient, but only a few (for example, three) of these electrode leads are connected to the display and chart recorder for derivation of data. Moreover, the attending physician or test administrator often finds it necessary, in the course of the test, to connect different leads to the display and chart recorder so as to be able to view a different set of derived data. In the prior art systems, ~ he mode change switches arc located at the front end where Ir.e πea≤ur i r.g el e Lrodes are d i reel! connected and be fore senscα electrccardioσrapny signals arc foeded to the zirsr operational amplifier. Thai is, f recorder is located rencLe place, the measuring moαo change can not c sonsscd at the 1 oca i on o f re or . A conventional electrocardiography system includes four electrodes, for example, a right-hand electrode, a left-hand electrode, a left-foot electrode and a chest electrode. The electrocardiography system measures the seven kinds of induced electromotive forces (I EF ): 1) a first I EF (V 2 ) ; 2) a second I EF (V 2 ) ; 3) a third I EF (V 3 ) ; 4) a Goldberg-right-hand I EF (aV R ) ; 5) a Goldberg-left-hand I EF (a V L ) ; 6) a Goldberg-left-foot I EF (a V F ) ; and 7) a illson-single-pole I EF (V w ) and also records all the induced electromotive forces or selectively records some of them. Where, E R is potential sensed at the right-hand electrode, E L is potential sensed at the left hand electrode, E F is potential sensed at the left-foot electrode, and E c is potential sensed at the chest electrode, these seven kinds of induced electromotive forces are as follows: the first I EF (V = E L - E R the second I EF (V 2 )= E F - E R the third I EF (V 3 )= E F - E L the Goldberg-right-hand I EF (aV R ) = E R - ( E L + E F ) /2 the Goldberg-left-hand I EF (aV L )= E L - ( E L + E F ) /2 the Goldberg-right-foot I EF (aV F )= E F - ( E R + E L ) /2 the Willson single-pole I EF (V = E c - ( E L + E F + E R ) /3 The electrocardiography system connected to an A.C. power supply includes a recorder consuming high power. When leakage current is caused by any reason, patients or operators are dangerous. Accordingly, a special isolation transformer is required to be electrically insulated from other parts . So, such a complete isolation may increase the fabrication cost of the electrocardiography system. In addition, since the electrocardiography system is connected to the A.C. power supply and it is subjected to the influenced of the common mode noise, the firm ground connection thereof should be provided so as to the potential of the equipment should be completely maintained to the ground level . Especially, for the convenience of a patient who should use the electrocardiography system at a company or home everyday, such a complete ground is inevitable and causes the user inconvenience . Further, the accuracy may be deteriorated due to the common mode noise caused by the A.C. power supply. Accordingly, the electrocardiography system could not be used at home without any control on electro-magnetic noise induction by which a great common mode noise can be generated and the measurement results are inaccurate. Disclosure of the Invention It, therefore, is an object of the present invention to provide an improved electrocardiography system which excludes common mode noises caused by an A.C. power supply. It is another object of the present invention to provide an improved electrocardiography system which prevents leakage current to cause danger to a patient and an operator. In an electrocardiography system according to the present invention, a measuring head part including sensing electrodes, which comes in contact with the human body, is isolated from an A.C. power supply. In accordance with an aspect of the present invention, there is provided an electrocardiography system having sensing electrodes for sensing electrocardiographic signals from a human body and a recorder for recording induced voltage signals generated by the sensing electrodes, the electrocardiography system comprising: a measuring head for receiving electrocardiographic signals sensed by the sensing electrodes and for generating difference voltage signals from the received electrocardiographic signals, wherein the measuring head is driven by a first power supply; a transmission link for transmitting the difference voltage signals; and an induced voltage generating means for receiving difference voltages signals via the transmission link and for generating induced voltage signals, wherein the measuring head is electrically isolated from the induced voltage generating means and wherein the induced voltage generating means is driven by a second power supply. In accordance with another aspect of the present invention, there is provided an electrocardiography system having sensing electrodes for sensing electrocardiographic signals from a human body and a recorder for recording induced voltage signals generated by the sensing electrodes, the electrocardiography system comprising: a measuring head for receiving electrocardiographic signals sensed by the sensing electrodes and for generating difference voltages signals from the received electrocardiographic signals: an induced voltage generating means for receiving difference voltages signals and for generating induced voltage signals; and a long-distance transmission means for transmitting the difference voltage signals via a long-distance transmission link, wherein the measuring head is electrically isolated from the induced voltage generating means and wherein the difference voltages signals are transmitted to the induced voltage generating means via a transmission link. In accordance with a further aspect of the present invention, there is provided an electrocardiography system having sensing electrodes for sensing electrocardiographic signals from a human body and a recorder for recording induced voltage signals generated by the sensing electrodes, the electrocardiography system comprising: a measuring head for receiving electrocardiographic signals sensed by the sensing electrodes and for generating difference voltages signals from the received electrocardiographic signals; a receiving means for receiving the difference voltages signals from the measuring head; a long-distance transmission means for transmitting the difference voltages signals received by the receiving means via a short-hop-distance transmission link; a long-distance receiving means for receiving the difference voltages signals transmitted by the long-distance transmission means; and an induced voltage generating means for receiving the difference voltages signals from the long-distance receiving means and for generating the induced voltage signals, wherein the measuring head is electrically isolated from the induced voltage generating means and wherein the difference voltages signals are transmitted to the induced voltage generating means via a transmission link. Brief Description of the Drawings A further understanding of the nature and advantage of the present invention will become apparent by reference to the remaining portions of the specification and drawings, in which: FIG. 1 is a schematic block diagram illustrating an electrocardiography system according to an embodiment of the present invention; FIG.2 is a schematic block diagram illustrating a measuring head part of the electrocardiography system according to an embodiment of the present invention; FIG. 3 is a schematic block diagram illustrating an induced voltage generator of the electrocardiography system according to an embodiment of the present invention; FIG. 4 is a schematic block diagram illustrating an electrocardiography system according to another embodiment of the present invention; and FIG. 5 is a schematic block diagram illustrating an electrocardiography system according to a further embodiment of the present invention. Detailed Description of the Preferred Embodiments Hereinafter, an electrocardiography system according to the present invention will be described in detail. First, referring to Fig. 1, an electrocardiography system 10 according to the present invention includes a measuring head part 100, an induced voltage generator 200, a recorder 300 and a power supply 400. The measuring head part 100 includes sensing electrodes which are in contact with a human body to sense electrocardiographic signals from the human body and has an additional power supply, such as a dry battery, a rechargeable battery, or the like. Also, electrocardiographic signals sensed in the sensing electrodes of the measuring head part 100 is transmitted to the induced voltage generator 200 via a transmission link 150. The transmission link 150 may be selected from a radio link and an optical communication link such as an optical fiber. That is, various communication links are can be used in the electrocardiography system 10 as far as the measuring head part 100 is electrically isolated form the power supply 400. Referring to Fig. 2, the measuring head part 100 includes a right-hand electrode 110, a left-hand electrode 112, a left-foot electrode 114 and a chest electrode 116. The measuring head part 100 also includes difference voltage generators 122 to 128 for generating difference voltage signals between a reference voltage and voltage signals from the electrodes 110, 112, 114 and 116 and cancels the common mode noise of electrode signal, an average voltage generator 120 for generating an average voltage signal which is obtained by receiving all the voltage signals from the electrodes 110, 112, 114 and 116, a multiplexer 130 for selecting one from outputs of the difference voltage generators 122 to 128, and a transmitting unit 132 for transmitting the multiplexed signal from the multiplexer 130 to the induced voltage generator 200 in Fig. 1. In addition, the measuring head part 100 includes the above-mentioned additional power supply 134 for providing electric power for the difference voltage generators 122 to 128, the multiplexer 130 and the transmitting unit 132. The right-hand electrode 110, the left hand electrode 112, the left-foot electrode 114 and the chest electrode 116 sense electrocardiographic signals at a right-hand, a left hand, a left-foot and a chest respectively. Each signal sensed by the electrodes 110, 112, 114 and 116 produces a sensed potential. For the convenience of explanation, E R denotes the potential sensed by the right-hand electrode 110, E L the left-hand electrode 112, E F the left-foot electrode 114 and E c the thoracic electrode 116, respectively. The average voltage generator 120 receives all signals from the four electrodes 110, 112, 114 and 116 and generates an average voltage E REF (or reference potential) (i.e., E REF = (E R + E L + E F + E c ) /4) . The difference voltage generators 122 to 128 generate the difference voltages V R , V L , V F and V c between the sensed potential and the average voltage E REF , respectively. Accordingly, the difference voltages V R , V L , V F and V c are given by: V R = E R v L = = E L - REF v F = = E F - REF V c = = E c - ■ ^REF The average voltage generator 120 and the difference voltage generators 122 to 128 may be implemented by typical operational amplifiers, which is well known to those skilled m the art to which the subject matter pertains. The multiplexer 130 multiplexes the difference voltage signals (V R , V L , V F and V c ) generated by the difference voltage generators 122 to 128 and transmits the multiplexed signal to the transmitting unit 132 connected with the transmission link 150. However, since the multiplexer 130 is used for improving the transmission rate, it can be removed if the transmission resources are sufficient to guarantee the high transmission rate . The transmitting unit 132 transmits the difference voltage signals (V R , V L , V F and V c ) , which are multiplexed by the multiplexer 130, to the induced voltage generator 200 via the transmission link 150. In the case where the transmission link 150 is implemented by a wireless communication link, the transmitting unit 132 may be a typical wireless transmitter and, m the case where the transmission link 150 is implemented by an optical communication link, the transmitting unit 132 may be a typical photo converter, such as LED (Light Emitting Diode) or LD (Laser Diode) . Finally, the auxiliary power supply 134 is separately used for providing the difference voltage generators 122 to 128, the multiplexer 130 and the transmitting unit 132 in the measuring head part 100 with power, being different from the power supply 400 for providing the induced voltage generator 200 and the recorder 300 with power. The auxiliary power supply 134 may be implemented by the primary or secondary batteries. Referring to Fig. 3, the induced voltage generator 200 includes a receiver 210 for receiving the signals from the measuring head part 100 via the transmission link 150 and a demultiplexer 212. The demultiplexer 212 demultiplexes the output signal from the receiver 210 to recover the difference voltage signals (V R , V L , V F and V c ) . Further, the induced voltage generator 200 includes inner voltage generators 214, 216, 218, 220, 222, 224 and 226 so that the recorder 300 records induced voltage signals which are divided into seven classes, by combining the difference voltage signals (V R , V L , V F and V c ) from the demultiplexer 212. At this time, in the case where the multiplexer 130 is not used, the demultiplexer 212 is also not used. The inner voltage generators 214 to 226 produce voltages Vj, V 2 , V 3 and aV R , aV L , aV F and V w , respectively. * ι ~ ~ E L — E R — ( E L — E REF ) — ( E R — E REF ) — V L - V R , V 2 — F — E R — ( E F — E REF ) — ( L R — E REF ) — V F — V R , V 3 = E F - E L = (E F - E REF ) - (E L - E REF ) = V F - V L , aV R = E R - (E L + E F ) /2 = (E R - E REF ) - ( (E L - E REF ) + (E F - E REF ) ) /2 = V R - (V L + V F )/2 = R - V LF aV L = E L - (E L + E F )/2 = (E L - E REF ) - ( (E L - E REF ) + (E F - E REF ) ) /2 = V L - (V L + V F ) /2 = V L - V LF aV F = E F - (E R + E L ) /2 = (E E - E REF ) - ( (E R - E REF ) + (E L - E REF ) ) /2 = V F - (V R + V L )/2 = v F - V,, V w = E c - (E L + E F + E R )/3 = (E c - E REF ) - ( (E L - E REF ) + (E F - E REF ) + (E R - E REF ) ) /3 = V c - (V L + V F + V R ) /3 = V c - V LFR In similar to the difference voltage generators 122 to 128, the inner voltage generators 214 to 226 can be implemented by typical operation amplifiers. Further, as shown in Fig. 3, the voltages V LF , V RL and V LFR necessary to generate the seven different voltage signals may be implemented by resistor mi ing network. This is well known to those skilled in the art to which the subject matter pertains so that further description is omitted. Also, in similar to the conventional electrocardiography systems, the induced voltage signals generated by the inner voltage generators 214 to 226 may be selectively recorded in the recorder 300. According to another embodiment of the present invention, the measuring head part 100 and the recorder 300 can be positioned at a long distance with wireless communication systems. Referring to Fig. 4, the measuring head part 100 and the induced voltage generator 200 are disposed at a short distance and the recorder 300 is disposed at a long distance. The difference voltage signals multiplexed by the measuring head part 100 are transmitted to the induced voltage generator 200 via the transmission link 150. The seven different voltage signals generated by the induced voltage generator 200 are transmitted by a long-distance transmitting unit 410 and a long-distance transmission link 450. The long-distance transmitting unit 410 can be implemented by a multiplexer and a modem. At this time, the long-distance transmission link 450 may be a public telephone network. Further, when the induced voltage generator 200 is mounted on a personal computer, it is possible to transmit the induced voltage signals to other districts in the same building using a LAN (Local Area Network) . In this case, the long-distance transmitting unit 410 may be a LAN card and the long-distance transmission link 450 may be a LAN (Local Area Network) . The induced voltage generator 200 and the long-distance transmitting unit 410 are driven by a separate power supply and the separate power supply is electrically connected to the measuring head part 100. Next, the seven different voltage signals transmitted by the long-distance transmitting unit 410 are received by a long-distance receiving unit 420 having a modem and a demultiplexer, and the long-distance receiving unit 420 divides the received signal into the seven different voltage signals and recovers them. The recovered voltage signals are recorded in the long-distance recorder 300. Of course, the long-distance receiving unit 420 and the recorder 300 may be mounted on a computer system and, in this case, the long-distance receiving unit 420 may be a LAN card. Further, the induced voltage generator 200 and the transmitting unit 410 are driven by a separate power supply 412 and the long-distance receiving unit 420 and the recorder 300 are also driven by a separate power supply 422. It should be noted that the power supplies 412 and 422 are electrically isolated from the measuring head part 100. In this embodiment, if the transmission link 150 and the long-distance transmission link 450 has enough resources to manage the electrocardiography system, the multiplexer and demultiplexer can be eliminated. As shown in Fig. 5, in a further embodiment of the present invention, an induced voltage generator 200' and the recorder 300 may be positioned at a long distance. At this time, the difference voltage signals multiplexed by the measuring head part 100 are transmitted to a receiving unit 210' via the transmission link 150. The receiving unit 210' may be the same as that included in the induced voltage generator 200 of Fig. 3. The multiplexed difference signals received by the receiving unit 210' are transmitted to a long-distance receiving unit 420' via a long-distance transmitting unit 410' and the long-distance transmission link 450. In this embodiment, the long-distance transmitting unit 410' may have no further use of the multiplexer . In similar to the embodiment in Fig. 4, the receiving unit 210' and the long-distance transmitting unit 410' are driven by a separate power supply 412' and the long-distance receiving unit 420' , the induced voltage generator 200' and the recorder 300 also driven by a separate power supply 422' . It should be noted that the power supplies 412' and 422' are electrically isolated from the measuring head part 100. Subsequently, the multiplexed difference signals transmitted by the long-distance transmitting unit 410' are received by the long-distance receiving unit 420' such as a modem. The induced voltage generator 200' divides the received signal into the seven different voltage signals base on an output from the long-distance receiving unit 420' and recovers them. The induced voltage generator 200' don 1 1 have to include a receiving unit as shown in Fig. 3. Finally, the recorder 300 records the seven different induced-voltage signals. Likewise, the long-distance transmission link 450 may be a LAN and the long-distance transmitting unit 410' and the long-distance receiving unit 420' may be LAN cards. If the transmission link 150 and the long-distance transmission link 450 have enough resources to manage the electrocardiography system, the multiplexer and the demultiplexer can also be eliminated. As apparent from the above description, the electrocardiography system according to the present invention drastically reduces the common mode noise and prevents leakage current causing an electric shock, by using the isolated measuring head part from A.C. power. The simple difference voltage generator can eliminate the common mode noise to a certain level requested by modern cardiology measurements . Also, since the recorder can be positioned at a long distance from the electrocardiography system, it is possible to promote the efficiency of the system management. Although the preferred embodiments of the invention have been disclosed for illustrative purpose, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in accompanying claim.

Claims: What is claimed is: 1. An electrocardiography system having sensing electrodes for sensing electrocardiographic signals from a human body and a recorder for recording induced voltage signals generated by the sensing electrodes, the electrocardiography system comprising: a measuring head for receiving electrocardiographic signals sensed by the sensing electrodes and for generating difference voltage signals from the received electrocardiographic signals, wherein the measuring head is driven by a first power supply; a transmission link for transmitting the difference voltage signals; and an induced voltage generating means for receiving difference voltage signals via the transmission link and for generating induced voltage signals, wherein the measuring head is electrically isolated from the induced voltage generating means and wherein the induced voltage generating means is driven by a second power supply. 2. The electrocardiography system as recited in claim 1, wherein the measuring head comprises: an average voltage generating means for receiving the electrocardiographic signals sensed by the sensing electrodes and for generating an average voltage signal which would be used as the cancellation voltage of common mode noise, from the received electrocardiographic signals; a plurality of difference voltage generating means for receiving the electrocardiographic signals from each sensing electrode and the average voltage signal from the average voltage generating means and for generating difference voltage signals between the electrocardiographic signals and the average voltage signal; and a transmitting means for sending the difference voltage signals to the induced voltage generating means. 3. The electrocardiography system as recited in claim 2, wherein the induced voltage generating means comprises: a receiving means for receiving the difference voltage signals from the measuring head; and a voltage generating means for generating the induced voltage signals to be recorded in a recorder by combining the difference voltage signals. 4. An electrocardiography system having sensing electrodes for sensing electrocardiographic signals from a human body and a recorder for recording induced voltage signals generated by the sensing electrodes, the electrocardiography system comprising: a measuring head for receiving electrocardiographic signals sensed by the sensing electrodes and for generating difference voltages signals from the received electrocardiographic signals: an induced voltage generating means for receiving difference voltage signals and for generating induced voltage s ignals ; and a long-distance transmission means for transmitting the difference voltage signals or the induced voltage signals via a long-distance transmission link if the recorder are located at a remote location, wherein the measuring head is electrically isolated from the induced voltage generating means and wherein the difference voltages signals are transmitted to the induced voltage generating means via a transmission link. 5. The electrocardiography system as recited in claim 4, wherein the measuring head comprises: an average voltage generating means for receiving the electrocardiographic signals sensed by the sensing electrodes and for generating an average voltage signal from the received electrocardiographic signals; a plurality of difference voltage generating means for receiving the electrocardiographic signals from each sensing electrode and the average voltage signal from the average voltage generating means and for generating difference voltage signals between the electrocardiographic signals and the average voltage signal; and a transmitting means for sending the difference voltage signals to the induced voltage generating means. 6. The electrocardiography system as recited in claim 5, wherein the induced voltage generating means comprises: a receiving means for receiving the difference voltage signals from the measuring head; and a voltage generating means for generating the induced voltage signals to be recorded in a recorder by combining the difference voltage signals. 7. An electrocardiography system having sensing electrodes for sensing electrocardiographic signals from a human body and a recorder for recording induced voltage signals generated by the sensing electrodes, the electrocardiography system comprising: a measuring head for receiving electrocardiographic signals sensed by the sensing electrodes and for generating difference voltages signals from the received electrocardiographic signals; a receiving means for receiving the difference voltages signals from the measuring head; a long-distance transmission means for transmitting the difference voltages signals received by the receiving means via a long-distance transmission link; a long-distance receiving means for receiving the difference voltages signals transmitted by the long-distance transmission means; and an induced voltage generating means for receiving the difference voltages signals from the long-distance receiving means and for generating the induced voltage signals, wherein the measuring head is electrically isolated from the induced voltage generating means and wherein the difference voltages signals are transmitted to the induced voltage generating means via a transmission link. 8. The electrocardiography system as recited in claim 7, wherein the measuring head comprises: an average voltage generating means for receiving the electrocardiographic signals sensed by the sensing electrodes and for generating an average voltage signal from the received electrocardiographic signals; a difference voltage generating means for receiving the electrocardiographic signals from each sensing electrode and the average voltage signal from the average voltage generating means and for generating difference voltage signals between the electrocardiographic signals and the average voltage signal; and a transmitting means for sending the difference voltage signals to the induced voltage generating means. 9. The electrocardiography system as recited in claim 8, wherein the induced voltage generating means comprises a voltage generating means for generating the induced voltage signals to be recorded in a recorder by combining the difference voltage signals .

Inventors: AHN BYUNG-SUNG, AHN, BYUNG-SUNG
Applicants: AHN BYUNG SUNG, AHN, BYUNG-SUNG
Application year: 1999
Main classification: A61B5
IPC codes: A61B5