Patent Description:
However, the MRI scanner is a harsh environment for detecting small, millivolt, ECG pulses produced by the heart. Conventional ECG systems are implemented with long electrical ECG leads individually connecting the ECG electrodes to an ECG module, which serves as the analog front end for the ECG electrodes, including amplification and analog-to-digital conversion of the ECG pulses. The ECG leads are susceptible to MRI noise pickup during active scans resulting in ECG signal degradation. The ECG leads may also be a source of radio frequency (RF) heating, induced by RF coils of the MRI scanner, which may cause thermal injuries to the subject if the ECG leads are not placed correctly. <CIT> relates to an electrocardiographic measurement apparatus and an MRI imaging system for electrocardiographic MRI that detects an electrocardiographic signal in an MRI apparatus and performs imaging in synchronization with the motion of a subject's heart.

The present invention is defined by independent claims <NUM> and <NUM>. The dependent claims define further embodiments of the invention.

According to a representative embodiment, a system is provided for acquiring electrocardiogram (ECG) pulses from a subject. The system includes a common node configured to create a virtual ground, and multiple measurement nodes connectable to corresponding ECG electrodes, respectively, attachable to the subject. The measurement nodes are connected to the virtual ground at the common node via short conductive paths, respectively. Each measurement node of the multiple measurement nodes includes an analog-to-digital converter (ADC) configured to convert an ECG signal from the corresponding ECG electrode to a digital signal; an optical converter configured to convert the digital signal from the ADC to an optical signal, and to output the optical signal via an output fiber-optic cable; a direct current (DC) power converter configured to receive a modulated optical signal with an embedded clock signal via an input fiber-optic cable, to recover DC power from the modulated optical signal, and to supply the DC power to at least the ADC and the optical converter; and a clock recovery circuit configured to receive the modulated optical signal with the embedded clock signal via the input fiber-optic cable, to recover the embedded clock signal from the modulated optical signal, and to supply the recovered clock signal to at least the ADC and the optical converter for synchronization. The common node may or may not be configured as a measurement node.

According to another representative embodiment, a system is provided for acquiring ECG pulses from a subject. The system includes a common node configured to create a virtual ground, and multiple measurement nodes in contact with corresponding ECG electrodes, respectively, that are attachable to the subject. The measurement nodes are connected to the virtual ground at the common node via short conductive paths, respectively. Each measurement node of the multiple measurement nodes includes an analog front end configured to receive and process an ECG signal from the corresponding ECG electrode; a DC power converter configured to receive a modulated optical signal with an embedded clock signal via an input fiber-optic cable, to recover DC power from the modulated optical signal, and to supply the DC power to the analog front end; and a clock recovery circuit configured to receive the modulated optical signal with the embedded clock signal via the input fiber-optic cable, to recover the embedded clock signal from the modulated optical signal, and to supply the recovered clock signal to the analog front end.

According to another representative embodiment, a measurement node is provided that is connectable to an ECG electrode attachable to a body of a subject for measuring ECG pulses from the subject. The measurement node includes an ADC configured to convert an ECG signal from the ECG electrode to a digital signal; an optical converter configured to convert the digital signal from the ADC to an optical signal, and to output the optical signal to an ECG monitor via an output fiber-optic cable; a DC power converter configured to receive a modulated optical signal from the ECG monitor with an embedded clock signal via an input fiber-optic cable, to recover DC power from the modulated optical signal, and to supply the DC power to at least the ADC and the optical converter; and a clock recovery circuit configured to receive the modulated optical signal with the embedded clock signal via the input fiber-optic cable, to recover the embedded clock signal from the modulated optical signal, and to supply the recovered clock signal to at least the ADC and the optical converter for synchronization. The ADC, the optical converter, the DC power converter, and the clock recovery circuit are connected to a virtual ground created by a common node attachable to the body of the subject via a short conductive path between the measurement node and the common node.

The example embodiments are best understood from the following detailed description when read with the accompanying drawing figures. It is emphasized that the various features are not necessarily drawn to scale. In fact, the dimensions may be arbitrarily increased or decreased for clarity of discussion. Wherever applicable and practical, like reference numerals refer to like elements.

In the following detailed description, for the purposes of explanation and not limitation, representative embodiments disclosing specific details are set forth in order to provide a thorough understanding of an embodiment according to the present teachings. Descriptions of known systems, devices, materials, methods of operation and methods of manufacture may be omitted so as to avoid obscuring the description of the representative embodiments. Nonetheless, systems, devices, materials, and methods that are within the purview of one of ordinary skill in the art are within the scope of the present teachings and may be used in accordance with the representative embodiments. It is to be understood that the terminology used herein is for purposes of describing particular embodiments only and is not intended to be limiting. The defined terms are in addition to the technical and scientific meanings of the defined terms as commonly understood and accepted in the technical field of the present teachings.

It will be understood that, although the terms first, second, third, etc. may be used herein to describe various elements or components, these elements or components should not be limited by these terms. These terms are only used to distinguish one element or component from another element or component. Thus, a first element or component discussed below could be termed a second element or component without departing from the teachings of the inventive concept.

The terminology used herein is for purposes of describing particular embodiments only and is not intended to be limiting. As used in the specification and appended claims, the singular forms of terms "a," "an" and "the" are intended to include both singular and plural forms, unless the context clearly dictates otherwise. Additionally, the terms "comprises," "comprising," and/or similar terms specify the presence of stated features, elements, and/or components, but do not preclude the presence or addition of one or more other features, elements, components, and/or groups thereof.

Unless otherwise noted, when an element or component is said to be "connected to," "coupled to," or "adjacent to" another element or component, it will be understood that the element or component can be directly connected or coupled to the other element or component, or intervening elements or components may be present. That is, these and similar terms encompass cases where one or more intermediate elements or components may be employed to connect two elements or components. However, when an element or component is said to be "directly connected" to another element or component, this encompasses only cases where the two elements or components are connected to each other without any intermediate or intervening elements or components.

The present disclosure, through one or more of its various aspects, embodiments and/or specific features or sub-components, is thus intended to bring out one or more of the advantages as specifically noted below. For purposes of explanation and not limitation, example embodiments disclosing specific details are set forth in order to provide a thorough understanding of an embodiment according to the present teachings. However, other embodiments consistent with the present disclosure that depart from specific details disclosed herein remain within the scope of the appended claims. Moreover, descriptions of well-known apparatuses and methods may be omitted so as to not obscure the description of the example embodiments. Such methods and apparatuses are within the scope of the present disclosure.

Generally, the various embodiments described herein provide an ECG system that includes synchronized measurement nodes configured to digitize and transmit ECG pulses acquired from a subject through corresponding ECG electrodes attached to a body of the subject. Each measurement node includes all necessary components at the corresponding ECG electrode to which it is attached for digitizing the ECG pulses. This eliminates the need for a conductive ECG lead to connect the measurement node to an ECG module. Without conductive ECG leads, the measurement nodes reduce signal degradation otherwise caused by noise within the bore of an MRI system, for example, caused by conventional measurement nodes and ECG modules. Each measurement node includes an analog-to-digital converter (ADC) for converting the ECG pulses to digital signals, a pair of fiber-optic cables for communicating DC power, clock and ECG pulse data with the ECG module, and a short conductive path for connecting to a common measurement node that creates a common electrical reference. The measurement nodes may be snapped or clipped onto existing ECG electrodes, or may incorporate dedicated ECG electrodes.

<FIG> is a simplified block diagram showing a set of measurement nodes for monitoring electrocardiogram (ECG) signals from a subject, according to a representative embodiment.

Referring to <FIG>, an illustrative measurement node set <NUM> is attachable to the skin of a subject, e.g., using adhesive strips, for acquiring ECG pulses produced by the subject's heart beat. The measurement node set <NUM> includes a measurement node <NUM> (e.g., left arm (LA) measurement node), a measurement node <NUM> (e.g., left leg (LL) measurement node), a measurement node <NUM> (e.g., right arm (RA) measurement node), and a common node <NUM> (e.g., right leg (RL) measurement node). As discussed below, the measurement nodes <NUM>, <NUM> and <NUM> include the necessary components for receiving and digitizing the ECG pulses, converting the digitized ECG pulses into optical ECG pulses, and communicating the optical pulses over optical fiber, thus eliminating the need for electrical ECG leads. In various configurations, the number of measurement nodes in the measurement node set <NUM> may vary (e.g., up to <NUM> total) to provide unique benefits for any particular situation or to meet application specific design requirements of various implementations, as would be apparent to one skilled in the art.

The common node <NUM> creates a common electrical reference for the measurement node set <NUM>, referred to as virtual ground (V-gnd). In an embodiment, the common node <NUM> may also be a measurement node with the same configuration as the measurement nodes <NUM>, <NUM> and <NUM>. In this case, the common node <NUM> may also be used for receiving and digitizing the ECG pulses, converting the digitized ECG pulses into optical ECG pulses, and communicating the optical pulses over optical fiber. Alternatively, the common node <NUM> may simply create the virtual ground without the functionality of a measurement node.

Since the common node <NUM> creates the virtual ground, the measurement nodes <NUM>, <NUM> and <NUM> are connected to the common node <NUM> through short conductive paths in relation to the subject's body length, so that they have a common ground potential without having to be electrically grounded, e.g., through long ECG leads. A short conductive path may be less than a quarter of the subject's body length, while the long ECG leads exceed the subject's body length. In particular, the measurement node <NUM> is connected to the common node <NUM> via conductive path <NUM>, the measurement node <NUM> is connected to the common node <NUM> via conductive path <NUM>, and the measurement node <NUM> is connected to the common node <NUM> via conductive path <NUM>. Each of the short conductive paths <NUM>, <NUM> and <NUM> is formed of a highly electrically conductive material, such as copper, aluminum, gold or silver, for example, and is no longer than about <NUM>, for example.

In the depicted embodiment, each of measurement nodes <NUM>, <NUM> and <NUM> is connected to a corresponding ECG electrode that attaches to the skin of the subject at specific locations on the subject's body to acquire ECG pulses generated from the subject's heartbeat. In particular, the measurement node <NUM> is connected to ECG electrode <NUM>, the measurement node <NUM> is connected to ECG electrode <NUM>, and the measurement node <NUM> is connected to ECG electrode <NUM>. The common node <NUM> is shown as optionally connected to ECG electrode <NUM> (indicated by dashed lines), which would occur when the common node <NUM> also has the functionality of a measurement node, as discussed above. The measurement nodes <NUM>, <NUM> and <NUM> may be detachably connected to the ECG electrodes <NUM>, <NUM> and <NUM>, in which case conventional ECG electrodes may be used. For example, the measurement nodes <NUM>, <NUM> and <NUM> may snap or clip onto respective upper surfaces (facing away from the subject's body) of the corresponding ECG electrodes <NUM>, <NUM> and <NUM>. Alternatively, the ECG electrodes <NUM>, <NUM> and <NUM> may be physically integrated within the measurement nodes <NUM>, <NUM> and <NUM>, respectively.

The measurement nodes <NUM>, <NUM> and <NUM> are further configured to communicate with an ECG module (not shown), discussed below with reference to <FIG>. Generally, the ECG module provides DC power and clock signals to the measurement nodes <NUM>, <NUM> and <NUM> via input fiber-optic cables, and processes the ECG signals provided by the measurement nodes <NUM>, <NUM> and <NUM> via output fiber-optic cables. In particular, the measurement node <NUM> is connected to input fiber-optic cable <NUM> and output fiber-optic cable <NUM>, the measurement node <NUM> is connected to input fiber-optic cable <NUM> and output fiber-optic cable <NUM>, and the measurement node <NUM> is connected to input fiber-optic cable <NUM> and output fiber-optic cable <NUM>. The common node <NUM> is shown as optionally connected to input fiber-optic cable <NUM> and output fiber-optic cable <NUM> (indicated by dashed lines). As mentioned above, this because the common node <NUM> may be configured as a measurement node to acquire ECG signals.

<FIG> shows an ECG system for monitoring ECG pulses from a subject, implemented within magnetic resonance imaging (MRI) system, according to a representative embodiment. Although depicted with the MRI system for purposes of explanation, it is understood that the ECG system may be implemented on its own or with any other type of medical imaging or medical testing system, without departing from the scope of the present teachings.

Referring to <FIG>, ECG system <NUM> is incorporated with representative MRI system <NUM> in order to monitor ECG pulses of a subject <NUM> during an MRI procedure. The MRI system <NUM> may be any type of MRI system, and the following description of the MRI system <NUM> is intended to be illustrative and not limiting. In the depicted example, the MRI system <NUM> includes a magnet <NUM> with a bore <NUM>. The magnet <NUM> may be a superconducting cylindrical magnet, for example, although use of different types of magnets is possible, such as a split cylindrical magnet and an open magnet. An imaging zone <NUM> is provided in the bore <NUM> where the magnetic field generated by operation of the magnet <NUM> is strong and uniform enough to perform the magnetic resonance imaging.

The subject <NUM> is placed on a support <NUM> and positioned within the bore <NUM> to be imaged during the MRI procedure. The support <NUM> may be attached to an actuator <NUM> (optional) configured to move the support <NUM>, so that the subject <NUM> may be moved through the imaging zone <NUM>. Accordingly, a larger portion of the subject <NUM> or the entire subject <NUM> may be imaged.

The ECG system <NUM> includes the measurement node set <NUM>, discussed above. Accordingly, the ECG electrodes <NUM>, <NUM> and <NUM> respectively corresponding to the measurement nodes <NUM>, <NUM> and <NUM> are attached to the skin of the subject <NUM> in order to perform ECG monitoring during the MRI procedure. Only the measurement node <NUM> is shown in <FIG> for the sake of convenience. As discussed above, the common node <NUM> (not shown) creates a virtual ground, and the measurement node <NUM> is connected to the common node <NUM> by the short conductive path <NUM> in order to provide the common electrical reference to the measurement node <NUM>. The other measurement nodes <NUM> and <NUM> (not shown) are likewise connected to the virtual ground provided by the common node <NUM>, as discussed above. In an embodiment, the common node <NUM> is also a measurement node, and is connected to the corresponding ECG electrode <NUM>.

The MRI system <NUM> includes a set of magnetic field gradient coils <NUM> configured to acquire magnetic resonance data for spatially encoding magnetic spins within the imaging zone <NUM>. A magnetic field gradient coil power supply <NUM> supplies current to the magnetic field gradient coils <NUM>. The current may be controlled as a function of time, and may be ramped or pulsed, for example. Although two magnetic field gradient coils <NUM> are shown, it is understood that additional magnetic field gradient coils may be included, e.g., to enable spatially encoding in three orthogonal spatial directions.

The MRI system <NUM> further includes RF coil <NUM> located within the bore <NUM>. The RF coil <NUM> is configured to manipulate orientations of magnetic spins within the imaging zone <NUM>, and to receive RF transmissions from spins also within the imaging zone <NUM>. The RF coil <NUM> may represent dedicated transmit and receive antennas or may contain multiple transmit and receive coil elements. The RF coil <NUM> is shown connected to an RF transceiver <NUM>, which transmits and receives RF signals to and from the RF coil <NUM> during the MRI procedure. In various configurations, the RF coil <NUM> and the RF transceiver <NUM> may be replaced by separate transmit and receive coils and separate transmitters and receivers, for example.

The actuator <NUM>, the magnetic field gradient coil power supply <NUM>, and the RF transceiver <NUM> are connected to a hardware interface <NUM> and a controller <NUM>. The controller <NUM> includes a processor <NUM>, memory <NUM>, and a user interface <NUM>. The memory <NUM> represents one or more non-transitory memories and/or data storage, discussed further below. The memory <NUM> may store pulse sequence instructions, which are executed by the processor <NUM> for performing the MRI procedure. The memory <NUM> may also include data storage for storing magnetic resonance data and/or reconstructed magnetic resonance images acquired during the MRI procedure. The hardware interface <NUM> enables the controller <NUM> to interact with, control and/or exchange data with at least the actuator <NUM>, the magnetic field gradient coil power supply <NUM>, and the RF transceiver <NUM>. The hardware interface <NUM> may include one or more of a universal serial bus (USB), IEEE <NUM> port, parallel port, IEEE <NUM> port, serial port, RS-<NUM> port, IEEE-<NUM> port, Bluetooth connection, wireless local area network connection, TCP/IP connection, Ethernet connection, control voltage interface, MIDI interface, analog input interface, and digital input interface, for example.

The processor <NUM> is representative of one or more processing devices and may be implemented by a general-purpose computer, a central processing unit, a computer processor, a microprocessor, a microcontroller, field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), a state machine, programmable logic device, or combinations thereof, using any combination of hardware, software, firmware, hard-wired logic circuits, or combinations thereof. A processor may also refer to a collection of processors within a single computer system or distributed among multiple computer systems, such as in a cloud-based or other multi-site application.

The memory <NUM> may be implemented by any number, type and combination of random-access memory (RAM) and read-only memory (ROM), for example, and may store various types of information, such as software algorithms, artificial intelligence (AI) machine learning models, and computer programs, all of which are executable by the processor <NUM>. The various types of ROM and RAM may include any number, type and combination of non-transitory computer readable storage media, such as a disk drive, flash memory, an electrically programmable read-only memory (EPROM), an electrically erasable and programmable read-only memory.

(EEPROM), registers, a hard disk, a removable disk, tape, compact disk read only memory (CD-ROM), digital versatile disk (DVD), floppy disk, Blu-ray disk, a universal serial bus (USB) drive, or any other form of storage medium known in the art. As used herein, the term non-transitory is to be interpreted not as an eternal characteristic of a state, but as a characteristic of a state that will last for a period. The term non-transitory specifically disavows fleeting characteristics such as characteristics of a carrier wave or signal or other forms that exist only transitorily in any place at any time.

The user interface <NUM> enables a user or operator to interact with the controller <NUM>, receiving input from the operator to be received by the processor <NUM> and providing output to the user from the processor <NUM>. That is, the user interface <NUM> may provide information or data to the operator and/or receive information or data from the operator. The display of data or information on a display or a graphical user interface is an example of providing information to the operator. The receiving of data through a keyboard, mouse, trackball, touchpad, pointing stick, graphics tablet, joystick, gamepad, webcam, headset, pedals, wired glove, remote control, and accelerometer are all examples of components of the user interface <NUM> which enable the receiving of information or data from the operator.

In addition to the measurement node set <NUM>, the ECG system <NUM> further includes an ECG module <NUM> and an output <NUM>. In the depicted embodiment, the ECG module <NUM> includes an optical modulator <NUM>, an optical demodulator <NUM>, and a processor <NUM>. The optical modulator <NUM> is configured to receive a clock signal from a clock <NUM> and a light signal from a light source <NUM>, to modulate the light signal and the clock signal using any compatible modulation technique, and to output a modulated optical signal with an embedded clock signal to the measurement nodes <NUM>, <NUM> and <NUM> via the respective input fiber-optic cables <NUM>, <NUM> and <NUM>, respectively. The light source <NUM> may be a laser or a light emitting diode (LED), for example. In an embodiment, the optical modulator <NUM> may provide a pulse width modulated (PWM) optical signal with an embedded clock signal, which may be embedded via light pulses, for example. Alternatively, the optical modulator <NUM> may provide a frequency modulated or amplitude modulated optical signal with the embedded clock signal. The frequencies and/or widths of the light pulses in the PWM optical signal and the embedded clock signal, for example, may be adjusted to suit the MRI scanning environment. For example, certain frequencies must be avoided as to not interfere with the MR scanned image. A tunable configuration of the ECG module <NUM> allows all frequencies to be selected or avoided.

The optical demodulator <NUM> is configured to receive optical ECG signals from the measurement nodes <NUM>, <NUM> and <NUM> via the respective output fiber-optic cables <NUM>, <NUM> and <NUM>, respectively, and to convert the ECG signals into corresponding electrical signals. The processor <NUM> is configured to execute instructions stored in a non-transitory memory (not shown) for processing the electrical signals to provide a corresponding ECG wave to the output <NUM>. The instructions may further cause the processor <NUM> to define characteristics of the ECG signals, such as the QRS complex, average beat, heart rate variability, RR interval, PR interval, and pulse rate, for example. The memory may be one or more non-transitory memories and/or data storage, as described above with reference to the memory <NUM>.

The processor <NUM> is representative of one or more processing devices, and may be implemented by a general-purpose computer, a central processing unit, a computer processor, a microprocessor, a microcontroller, FPGAs, ASICs, a state machine, programmable logic device, or combinations thereof, using any combination of hardware, software, firmware, hard-wired logic circuits, or combinations thereof. A processor may also refer to a collection of processors within a single computer system or distributed among multiple computer systems, such as in a cloud-based or other multi-site application.

The output <NUM> may include any type of visual manifestation of the ECG traces. For example, the output <NUM> may include a display for displaying the ECG wave, such as a computer monitor, a television, a liquid crystal display (LCD), an organic light emitting diode (OLED) display, a flat panel display, a solid-state display, or a cathode ray tube (CRT) display, a touch screen or an electronic whiteboard, for example. Alternatively, or in addition, the output <NUM> may include a printer, such as a thermal printer or an inkjet printer, for example, for printing the ECG wave. ECG wave may be displayed and/or printed together with textual and/or graphical information that classifies and/or interprets the ECG wave.

In the depicted embodiment, the measurement nodes <NUM>, <NUM> and <NUM> are physically connected to the ECG module <NUM> via the input fiber-optic cables <NUM>, <NUM> and <NUM> and the output fiber-optic cables <NUM>, <NUM> and <NUM>, respectively. However, in an alternative embodiment, the measurement nodes <NUM>, <NUM> and <NUM> may be connected to a transceiver and antenna (not shown) via the input fiber-optic cables <NUM>, <NUM> and <NUM> and the output fiber-optic cables <NUM>, <NUM> and <NUM>, respectively, where the transceiver is configured to communicate wirelessly with the ECG module <NUM>. In this case, the ECG module <NUM> would likewise include a transceiver and antenna (not shown) for sending the DC power and clock signals and receiving the ECG signals.

As discussed above, the measurement nodes <NUM>, <NUM> and <NUM> have the same configuration. In various implementations, the common node <NUM> may also have the same configuration as the measurement nodes <NUM>, <NUM> and <NUM> (except for the conductive paths). <FIG> is a simplified block diagram showing an illustrative measurement node for monitoring ECG signals from a subject, according to a representative embodiment. In particular, <FIG> shows the measurement node <NUM> as being representative of all the measurement nodes, for purposes of illustration.

Referring to <FIG>, the measurement node <NUM> includes a DC power converter <NUM> and a clock recovery circuit <NUM>, which are connected to the input fiber-optic cable <NUM>. The DC power converter <NUM> is configured to receive the modulated optical signal from the optical modulator <NUM> of the ECG module <NUM> via the input fiber-optic cable <NUM>, and to convert the modulated optical signal to a corresponding electrical signal. By converting the modulated optical signal to the electrical signal, the DC power converter <NUM> recovers DC power embedded within the modulated optical signal. For example, when the modulated optical signal is a PWM optical signal, the magnitude of the DC power is indicated by the frequency and/or widths of the light pulses. The DC power converter <NUM> may be a photovoltaic cell, for example, which converts optical signals directly into electrical signals using photovoltaic effect. The clock recovery circuit <NUM> recovers the embedded clock signal from the modulated optical signal. The clock recovery circuit <NUM> may be an edge detector, phase detector or a frequency detector, for example. The detectors of the clock recovery circuit depend on how the clock is optically encoded, as is known in the art. Recovery of the DC power and the embedded clock signal may be performed in any order or simultaneously. The DC power converter <NUM> outputs the DC power (Vcc) and the clock recovery circuit <NUM> outputs the recovered clock signal (Clk) to other components of the measurement node <NUM>, discussed below.

The measurement node <NUM> is shown connected to the ECG electrode <NUM>, which is attached to the skin of the subject <NUM>, to receive small analog ECG pulses, which may be in the µV to mV ranges. The measurement node <NUM> provides an analog front end for the ECG electrode <NUM>, including an optional programmable gain amplifier (PGA) <NUM> (indicated by dashed lines) and an analog-to-digital converter (ADC) <NUM>, as well as an optical converter <NUM>. As shown, each of the PGA <NUM>, the ADC <NUM>, and the optical converter <NUM> receive the DC power (Vcc) from the DC power converter <NUM> and the recovered clock signal (Clk) from the clock recovery circuit <NUM>. Accordingly, the PGA <NUM>, the ADC <NUM>, and the optical converter <NUM> are powered without an electrical power source using the DC power (Vcc) and are synchronized with one another using the recovered clock signal (Clk).

The PGA <NUM> receives the analog ECG pulses from the ECG electrode <NUM>, which are electrical signals. The ADC <NUM> converts the ECG pulses into digital ECG signals at a predetermined sampling frequency (e.g., <NUM>). The optical converter <NUM> receives the digital ECG signals and converts them to optical ECG signals. The optical converter <NUM> may be a laser or an LED light source, for example. The optical converter <NUM> outputs the optical ECG signals to the optical demodulator <NUM> of the ECG module <NUM> via the output fiber-optic cable <NUM>.

In addition, the grounds of each of the DC power converter <NUM>, the clock recovery circuit <NUM>, the PGA <NUM>, the ADC <NUM>, and the optical converter <NUM> are connected to the virtual ground (V-gnd) created by the common node <NUM> via the conductive path <NUM>. Accordingly, the DC power and clock recovery circuit <NUM>, the PGA <NUM>, the ADC <NUM>, and the optical converter <NUM> are grounded to a common potential, along with the components of the other measurement nodes (e.g., measurement nodes <NUM>, <NUM>), without having to be electrically grounded elsewhere in the ECG system <NUM>. The recovered DC power and the virtual grounding of the measurement node <NUM> eliminate the need for electrical leads connecting the measurement node <NUM> to an external power source and ground.

The illustrations are not intended to serve as a complete description of all of the elements and features of the disclosure described herein.

Claim 1:
A system (<NUM>) for acquiring electrocardiogram (ECG) pulses from a subject, the system comprising:
a common node (<NUM>) configured to create a virtual ground (V-gnd); and
a plurality of measurement nodes (<NUM>, <NUM>, <NUM>) connectable to a plurality of corresponding ECG electrodes (<NUM>, <NUM>, <NUM>), respectively, attachable to the subject;
wherein the plurality of measurement nodes are connected to the virtual ground at the common node via short conductive paths (<NUM>, <NUM>, <NUM>), respectively;
wherein each measurement node of the plurality of measurement nodes comprises:
an analog-to-digital converter (ADC, <NUM>) configured to convert an ECG signal from the corresponding ECG electrode to a digital signal;
an optical converter (<NUM>) configured to convert the digital signal from the ADC to an optical signal, and to output the optical signal via an output fiber-optic cable (<NUM>, <NUM>, <NUM>);
a DC power converter (<NUM>) configured to receive a modulated optical signal with an embedded clock signal via an input fiber-optic cable (<NUM>, <NUM>, <NUM>), to recover DC power from the modulated optical signal, and to supply the DC power to at least the ADC and the optical converter; and
a clock recovery circuit (<NUM>) configured to receive the modulated optical signal with the embedded clock signal via the input fiber-optic cable, to recover the embedded clock signal from the modulated optical signal, and to supply the recovered clock signal to at least the ADC and the optical converter for synchronization.