Voltage-to-frequency electrocardiogram measurement node

Abstract

A system for acquiring electrocardiogram (ECG) pulses from a subject includes: a virtual ground; the system includes a virtual ground, a plurality of ECG electrodes connected to the virtual ground, and a plurality of measurement nodes connectable to a plurality of corresponding ECG electrodes, where the plurality of measurement nodes are connected to the virtual ground, where each of the plurality of measurement nodes includes: a voltage-to-frequency converter (VFC) configured to convert an ECG signal from a corresponding ECG electrode into a frequency signal; an optical converter configured to: convert a frequency signal from the VFC into an optical signal, and output the optical signal via an output fiber optic cable; and a DC power converter configured to receive a modulated optical signal via an input fiber optic cable, to recover DC power from the modulated optical signal, and to provide the DC power to at least the VFC and the optical converter.

Description

Technical Field

[0001] The present disclosure generally relates to systems for acquiring electrocardiogram (ECG) pulses from a subject in an MRI environment. Background Art

[0002] An electrocardiogram system monitors a subject's cardiac function by collecting and measuring ECG pulses through ECG electrodes in contact with the subject. ECG systems may be useful for monitoring subjects in potentially stressful situations during medical diagnosis and treatment. For example, during a magnetic resonance imaging (MRI) procedure, a subject is confined to the relatively small diameter bore of an MRI scanner for a long period of time, which may cause anxiety. Therefore, ECG electrodes may be attached to the subject while in the bore during the MRI procedure to provide ECG pulses in real time, and thereby provide information about the subject's health status.

[0003] However, an MRI scanner is a harsh environment for detecting the small millivolt ECG pulses generated by the heart. Conventional ECG systems use long electrical ECG leads to connect the ECG electrodes individually to an ECG module, which serves as an analog front end for the ECG electrodes, including amplification and analog-to-digital conversion of the ECG pulses. In fact, a typical MRI-compatible multi-electrode ECG measurement setup is achieved by current ECG lead connections between the patient electrodes and a remotely located module that processes the signals of all leads at a single location. During active scanning, the ECG leads are susceptible to MRI noise pickup, resulting in signal degradation. If improperly placed, the ECG leads may also become a source of RF heating, causing thermal damage to sedated patients. In addition, the ECG equipment inside the MRI bore may interfere with MRI image quality. Summary of the invention

[0004] Therefore, there remains a need for a system suitable for collecting ECG pulses from a subject in an MRI environment. Various embodiments and implementations herein relate to a system for collecting ECG pulses from a subject. The system includes a plurality of measurement nodes that can be connected to a plurality of corresponding ECG electrodes, wherein each of the plurality of corresponding ECG electrodes can be attached to the subject, wherein the plurality of measurement nodes are connected to a virtual ground, wherein each of the plurality of measurement nodes includes: a voltage to frequency converter (VFC), an optical converter, and a DC power converter.

[0005] In general, in one aspect, a system for collecting ECG pulses from a subject is provided. The system includes a virtual ground, and a plurality of measurement nodes connectable to a plurality of corresponding ECG electrodes, wherein each of the plurality of corresponding ECG electrodes can be attached to the subject, and wherein the plurality of measurement nodes are connected to the virtual ground. Each of the plurality of measurement nodes includes: a voltage-to-frequency converter (VFC) configured to convert an ECG signal from a corresponding ECG electrode into a frequency signal; an optical converter configured to convert the frequency signal from the VFC into an optical signal, and output the optical signal via an output optical fiber cable; and a DC power converter configured to receive a modulated optical signal via an input optical fiber cable to recover DC power from the modulated optical signal, and provide the DC power to at least the VFC and the optical converter.

[0006] According to an embodiment, the modulated optical signal includes an embedded clock signal, and wherein the system further comprises: for each of the plurality of measurement nodes, a clock recovery circuit is configured to: receive the modulated optical signal with the embedded clock signal via an input optical fiber cable, recover the embedded clock signal from the modulated optical signal, and provide the recovered clock signal to at least the VFC and the optical converter for synchronization.

[0007] According to an embodiment, the system further comprises an ECG module configured to: provide the modulated optical signal to the plurality of measurement nodes via input optical fiber cables, respectively, receive optical signals from the plurality of measurement nodes via output optical fiber cables, respectively, and convert the optical signals into the ECG pulses.

[0008] According to an embodiment, the plurality of measurement nodes include a left arm (LA) measurement node, a right arm (RA) measurement node, a left leg (LL) measurement node, and a right leg (RL) measurement node.

[0009] According to an embodiment, the DC power converter of each measurement node of the plurality of measurement nodes comprises a photovoltaic cell.

[0010] According to an embodiment, each measurement node of the plurality of measurement nodes further comprises a programmable gain amplifier (PGA) connected to an input of the VFC and configured to amplify the ECG signal.

[0011] According to an embodiment, the system further comprises a monitor configured to display the ECG pulses output by the ECG module.

[0012] According to an embodiment, the subject is placed in a magnetic resonance imaging (MRI) bore while ECG pulses are acquired.

[0013] According to an embodiment, the modulated optical signal comprises a pulse width modulated (PWM) optical signal.

[0014] According to an embodiment, the modulated optical signal comprises a frequency modulated or amplitude modulated optical signal.

[0015] According to an embodiment, the VFC of each measurement node is configured to convert the ECG signal into a different frequency signal relative to each other measurement node.

[0016] According to another aspect, a system for acquiring ECG pulses from a subject is provided. The system includes: (i) a virtual ground; (ii) a plurality of measurement nodes that are connectable to a plurality of corresponding ECG electrodes, wherein each of the plurality of corresponding ECG electrodes is attachable to the subject and includes a left arm (LA) measurement node, a right arm (RA) measurement node, a left leg (LL) measurement node, and a right leg (RL) measurement node, wherein the plurality of measurement nodes are connected to the virtual ground, wherein each of the plurality of measurement nodes includes: a programmable gain amplifier (PGA) configured to amplify the ECG signal; a voltage-to-frequency converter (VFC) configured to convert the ECG signal into a frequency signal; and an optical (iii) an ECG module, which is configured to: provide the modulated optical signal to the plurality of measurement nodes via the input optical fiber cables, receive the optical signals from the plurality of measurement nodes via the output optical fiber cables, and convert the optical signals into the ECG pulses. And (iv) a monitor, which is configured to display the ECG pulses output by the ECG module.

[0017] It should be understood that all combinations of the above-described concepts and the additional concepts discussed in more detail below (assuming such concepts are not mutually inconsistent) are contemplated as being part of the inventive subject matter disclosed herein. In particular, all combinations of the subject matter of the claims are contemplated as being part of the inventive subject matter disclosed herein. It should also be understood that terms explicitly employed herein, which may also appear in any disclosure incorporated by reference, should be given the meaning that best matches the specific concepts disclosed herein.

[0018] These and other aspects of the embodiments will be apparent from and elucidated with reference to the embodiment(s) described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In the accompanying drawings, the same reference numerals generally refer to the same parts in different views. The accompanying drawings illustrate features and modes of implementing various embodiments and should not be interpreted as limiting other possible embodiments that fall within the scope of the appended claims. Likewise, the drawings are not necessarily to scale, but the emphasis is on illustrating the principles of the various embodiments.

[0020] Figure 1 is a schematic diagram of a collection of measurement nodes for monitoring ECG signals from a subject according to an embodiment.

[0021] Figure 2 is a schematic diagram of an ECG system implemented within a magnetic resonance imaging (MRI) system for monitoring ECG pulses from a subject according to an embodiment.

[0022] Figure 3 is a schematic diagram of a representative measurement node for monitoring an ECG signal from a subject, according to an embodiment. DETAILED DESCRIPTION

[0023] The present disclosure describes various embodiments of an electrocardiogram (ECG) system configured to collect ECG pulses from a subject. More generally, the applicant has recognized and appreciated that it would be beneficial to provide an ECG system configured to operate in an MRI environment. The ECG system includes a plurality of measurement nodes connectable to a plurality of corresponding ECG electrodes, wherein each of the plurality of corresponding ECG electrodes can be attached to an object, wherein the plurality of measurement nodes are connected to a virtual ground, wherein each of the plurality of measurement nodes includes: a voltage to frequency converter (VFC), an optical converter, and a DC power converter. According to an embodiment, the system described or contemplated herein can be implemented as an element of a commercial product for an MRI environment in some non-limiting embodiments.

[0024] According to an embodiment, the ECG system described or contemplated herein includes a synchronous measurement node configured to transmit ECG pulses collected from a subject by corresponding ECG electrodes attached to the subject's body. Each measurement node includes all necessary components for formatting ECG pulses on the corresponding ECG electrodes connected thereto. This eliminates the need to connect the measurement node to the ECG module using a conductive ECG wire. Without the need for a conductive ECG wire, the measurement node can reduce signal attenuation (e.g., caused by a traditional measurement node and ECG module) that would otherwise be caused by noise in the bore of the MRI system. The measurement node can be snapped into or clipped onto an existing ECG electrode, or a dedicated ECG electrode can be incorporated.

[0025] refer to Figure 1, in one embodiment, is a schematic diagram of a set of measurement nodes for monitoring ECG signals from a subject. The measurement node set 100 can be attached to the skin of the subject for collecting ECG pulses generated by the heartbeat of the subject. The measurement node set 100 includes a measurement node 110 (e.g., a left arm (LA) measurement node), a measurement node 120 (e.g., a left leg (LL) measurement node), a measurement node 130 (e.g., a right arm (RA) measurement node), and a measurement node 140 (e.g., a right leg (RL) measurement node). Any of these nodes can be a common node, and in this example, node 140 is a common node. As described below, the measurement nodes 110, 120, and 130 include the necessary components for receiving ECG pulses, converting ECG pulses into optical ECG pulses, and transmitting the optical pulses through optical fibers, thereby eliminating the need for electrical ECG wires. In various configurations, the number of measurement nodes in the measurement node set 100 can be varied to provide unique advantages for any particular situation or to meet the specific application design requirements of various implementations, which will be apparent to those skilled in the art.

[0026] The common node 140 creates a common electrical reference for the set of measurement nodes 100, called a virtual ground (V-gnd). In one embodiment, the common node 140 may also be a measurement node having the same configuration as the measurement nodes 110, 120, and 130. In this case, the common node 140 may also be used to receive ECG pulses, convert ECG pulses into optical ECG pulses, and transmit optical pulses through optical fibers. Alternatively, the common node 140 may only create a virtual ground without the functionality of a measurement node.

[0027] Because common node 140 creates a virtual ground, measurement nodes 110, 120, and 130 are connected to common node 140 via conductive paths that are short relative to the subject's body length, so that they have a common ground potential without the need for electrical grounding (e.g., through a long ECG lead). The short conductive path may be less than one-quarter of the subject's body length, while the long ECG lead exceeds the subject's body length. Specifically, measurement node 110 is connected to common node 140 via conductive path 115, measurement node 120 is connected to common node 140 via conductive path 125, and measurement node 130 is connected to common node 140 via conductive path 135. For example, each short conductive electrical path 115, 125, and 135 is formed of a highly conductive material (such as copper, aluminum, gold, or silver) and has a length not exceeding, for example, about 12 centimeters.

[0028] In the depicted embodiment, each of the measurement nodes 110, 120, and 130 is connected to a corresponding ECG electrode, which is attached to the subject's skin at a specific location on the subject's body to collect ECG pulses generated by the subject's heartbeat. Specifically, the measurement node 110 is connected to the ECG electrode 118, the measurement node 120 is connected to the ECG electrode 128, and the measurement node 130 is connected to the ECG electrode 138. The common node 140 is shown as optionally connected to the ECG electrode 148 (represented by the dotted line), which will occur when the common node 140 also has the function of a measurement node, as described above. The measurement nodes 110, 120, and 130 can be detachably connected to the ECG electrodes 118, 128, and 138, in which case conventional ECG electrodes can be used. For example, the measurement nodes 110, 120, and 130 can be snapped into or clipped onto the respective upper surfaces (facing away from the subject's body) of the corresponding ECG electrodes 118, 128, and 138. Alternatively, ECG electrodes 118, 128, and 138 may be physically integrated within measurement nodes 110, 120, and 130, respectively.

[0029] The measurement nodes 110, 120 and 130 are also configured to communicate with an ECG module (not shown), which will be referred to below. Figure 2 For discussion. In general, the ECG module provides DC power to 110, 120 and 130 via an input fiber optic cable and optionally provides a clock signal and processes the ECG signal provided via output fiber optic cables 110, 120 and 130. Specifically, measurement node 110 is connected to input fiber optic cable 111 and output fiber optic cable 112, measurement node 120 is connected to input fiber optic cable 121 and output fiber optic cable 122, and measurement node 130 is connected to input fiber optic cable 131 and output fiber optic cable 132. Common node 140 is shown as optionally connected to input fiber optic cable 141 and output fiber optic cable 142 (represented by dotted lines). As described above, this is because common node 140 can be configured as a measurement node to collect ECG signals.

[0030] refer to Figure 2 , in one embodiment, is an ECG pulse for monitoring a subject implemented in a magnetic resonance imaging (MRI) system. Although described with an MRI system for explanation purposes, it should be understood that the ECG system can be implemented alone or in conjunction with any other type of medical imaging or medical testing system without departing from the scope of the present teachings.

[0031] refer to Figure 2, the ECG system 200 is combined with a representative MRI system 210 to monitor the ECG pulses of the subject 201 during the MRI procedure. The MRI system 210 can be any type of MRI system, and the following description of the MRI system 210 is intended to be illustrative and not limiting. In the example shown, the MRI system 210 includes a magnet 212 having a bore 213. The magnet 212 can be, for example, a superconducting cylindrical magnet, but different types of magnets, such as split cylindrical magnets and open magnets, can also be used. An imaging area 214 is provided in the bore 213, wherein the magnetic field generated by the operation of the magnet 212 is sufficiently strong and uniform to perform magnetic resonance imaging.

[0032] The object 201 is placed on a support 203 and positioned within a bore 213 to be imaged during an MRI procedure. The support 203 may be attached to an actuator 204 (optional) configured to move the support 203 so that the object 201 may be moved through an imaging region 214. Thus, a larger portion of the object 201 or the entire object 201 may be imaged.

[0033] ECG system 200 includes measurement node set 100 discussed above. Thus, ECG electrodes 118, 128, and 138 corresponding to measurement nodes 110, 120, and 130, respectively, are attached to the skin of subject 201 to perform ECG monitoring during an MRI procedure. For convenience, Figure 2 Only the measurement node 130 is shown in FIG. As described above, the common node 140 (not shown) creates a virtual ground, and the measurement node 130 is connected to the common node 140 through a short conductive path 135 to provide a common electrical reference for the measurement node 130. Other measurement nodes 110 and 120 (not shown) are similarly connected to the virtual ground provided by the common node 140, as described above. In one embodiment, the common node 140 is also a measurement node and is connected to a corresponding ECG electrode 148.

[0034] The MRI system 210 includes a set of magnetic field gradient coils 216 configured to acquire magnetic resonance data to spatially encode magnetic spins within the imaging region 214. A magnetic field gradient coil power supply 218 supplies current to the magnetic field gradient coils 216. The current may be controlled as a function of time, such as a ramped current or a pulsed current. Although two magnetic field gradient coils 216 are shown, it should be understood that additional magnetic field gradient coils may be included, for example, to enable spatial encoding in three orthogonal spatial directions.

[0035] The MRI system 210 also includes an RF coil 217 positioned within the bore 213. The RF coil 217 is configured to manipulate the direction of magnetic spins within the imaging region 214 and receive RF transmissions from the spins within the imaging region 214. The RF coil 217 may represent a dedicated transmit and receive antenna, or may include multiple transmit and receive coil elements. The RF coil 217 is shown connected to an RF transceiver 219, which transmits RF signals to and receives RF signals from the RF coil 217 during the MRI procedure. In various configurations, the RF coil 217 and the RF transceiver 219 may be replaced by, for example, separate transmit and receive coils and separate transmitters and receivers.

[0036] The actuator 204, the magnetic field gradient coil power supply 218, and the radio frequency transceiver 219 are connected to the hardware interface 221 and the controller 222 respectively. The controller 222 includes a processor 224, a memory 226, and a user interface 228. The memory 226 represents one or more non-transient memories and / or data memories, as further discussed below. The memory 226 can store pulse sequence instructions, which are executed by the processor 224 to perform the MRI process. The memory 226 can also include a data storage device for storing magnetic resonance data collected during the MRI process and / or reconstructed magnetic resonance images. The hardware interface 221 enables the controller 222 to interact, control, and / or exchange data with at least the actuator 204, the magnetic field gradient coil power supply 218, and the RF transceiver 219. For example, the hardware interface 221 may include one or more of the following: a universal serial bus (USB), an IEEE 1394 port, a parallel port, an IEEE 1284 port, a serial port, an RS-232 port, an IEEE-488 port, a Bluetooth connection, a wireless LAN connection, a TCP / IP connection, an Ethernet connection, a control voltage interface, a MIDI interface, an analog input interface, and a digital input interface.

[0037] Processor 224 represents 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, a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), a state machine, a programmable logic device, or a combination thereof, using any combination of hardware, software, firmware, hardwired logic circuitry, or a combination thereof. A processor may also refer to a collection of processors within a single computer system, or a collection of processors distributed among multiple computer systems, such as in a cloud-based or other multi-site application.

[0038] For example, the memory 226 may be implemented by any number, type, and combination of random access memory (RAM) and read-only memory (ROM), and may store various types of information, such as software algorithms, artificial intelligence (AI) machine learning models, and computer programs, all of which may be run by the processor 224. The various types of ROM and RAM may include any number, type, and combination of non-transitory computer-readable storage media, such as disk drives, flash memory, electrically programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), registers, hard disks, removable disks, tapes, compact disk read-only memory (CD-ROM), digital versatile disks (DVD), floppy disks, Blu-ray disks, universal serial bus (USB) drives, or any other form of storage media known in the art. As used herein, the term non-transitory should be interpreted as a state characteristic that is not permanent, but rather a state characteristic that will persist for a period of time. The term non-transitory specifically negates fleeting characteristics, such as characteristics of a particular propagating carrier or signal or other forms that exist only transiently anywhere at any time.

[0039] The user interface 228 enables a user or operator to interact with the controller 222, receives input from the operator to be received by the processor 224, and provides output from the processor 224 to the user. That is, the user interface 228 can 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 graphical user interface is an example of providing information to the operator. Receiving data through a keyboard, mouse, trackball, touchpad, pointing stick, graphic input tablet, joystick, game pad, webcam, helmet, pedal, wired gloves, remote control, and accelerometer are all examples of components of the user interface 228 that implements receiving information or data from the operator.

[0040] In addition to the measurement node set 100, the ECG system 200 also includes an ECG module 230 and an output unit 240. In the described embodiment, the ECG module 230 includes an optical modulator 231, an optical demodulator 232, and a processor 233. The optical modulator 231 is configured to receive a clock signal from a clock 237 and an optical signal from a light source 238, modulate the optical signal and the clock signal using any compatible modulation technique, and output the modulated optical signal of the embedded clock signal to the measurement nodes 110, 120, and 130 via the corresponding input optical fiber cables 111, 121, and 131, respectively. The light source 238 can be, for example, a laser or a light emitting diode (LED). In an embodiment, the optical modulator 231 can provide a pulse width modulated (PWM) optical signal with an embedded clock signal, for example, the embedded clock signal can be embedded via an optical pulse. Alternatively, the optical modulator 231 can provide a frequency modulated or amplitude modulated optical signal using the embedded clock signal. For example, the frequency and / or width of the light pulses in the PWM optical signal and the embedded clock signal can be adjusted to adapt to the MRI scanning environment. For example, specific frequencies must be avoided so as not to interfere with the MR scan image. The tunable configuration of the ECG module 230 allows all frequencies to be selected or avoided.

[0041] The optical demodulator 232 is configured to receive optical ECG signals from the measurement nodes 110, 120 and 130 via respective output fiber optic cables 112, 122 and 132, respectively, and convert the ECG signals into corresponding electrical signals. The processor 233 is configured to execute instructions stored in a non-transient memory (not shown) for processing the electrical signals to provide corresponding ECG waves to the output 240. The instructions may also enable the processor 233 to define the characteristics of the ECG signal, such as QRS complex wave, average heart beat, heart rate variability, RR interval, PR interval and pulse rate. The memory may be one or more non-transient memories and / or data memories, as described above with reference to the memory 226.

[0042] Processor 233 represents one or more processing devices and may be implemented by a general purpose computer, central processing unit, computer processor, microprocessor, microcontroller, FPGA, ASIC, state machine, programmable logic device, or a combination thereof, using any combination of hardware, software, firmware, hardwired logic circuits, or a combination thereof. A processor may also refer to a collection of processors within a single computer system, or a collection of processors distributed among multiple computer systems, such as in a cloud-based or other multi-site application.

[0043] Output 240 may include any type of visual representation of the ECG trace. For example, output 240 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. Alternatively or additionally, output 240 may include a printer, such as a thermal printer or an inkjet printer, for printing the ECG wave. The ECG wave may be displayed and / or printed together with text and / or graphical information that classifies and / or interprets the ECG wave.

[0044] In the illustrated embodiment, the measurement nodes 110, 120, and 130 are physically connected to the ECG module 230 via input fiber optic cables 111, 121, and 131 and output fiber optic cables 112, 122, and 132. However, in alternative embodiments, the measurement nodes 110, 120, and 130 may be connected to a transceiver and antenna (not shown) via the input fiber optic cables 111, 121, and 131 and the output fiber optic cables 112, 122, and 132, wherein the transceiver is configured to wirelessly communicate with the ECG module 230. In this case, the ECG module 230 would similarly include a transceiver and antenna (not shown) for transmitting DC power and clock signals and receiving ECG signals.

[0045] As described above, the measurement nodes 110, 120, and 130 have the same configuration. In various embodiments, the common node 140 may also have the same configuration as the measurement nodes 110, 120, and 130 (except for the conductive paths). Figure 3 is a simplified block diagram showing an illustrative measurement node for monitoring an ECG signal from a subject according to a representative embodiment. Specifically, for purposes of illustration, Figure 3 The measuring node 130 is shown as a representative representing all measuring nodes.

[0046] refer to Figure 3 , the measurement node 130 includes a DC power converter 310 and a clock recovery circuit 315, which are connected to the input fiber optic cable 131. The DC power converter 310 is configured to receive a modulated optical signal from the optical modulator 231 of the ECG module 230 via the input fiber optic cable 131, and convert the modulated optical signal into a corresponding electrical signal. By converting the modulated optical signal into an electrical signal, the DC power converter 310 recovers the DC power embedded in the modulated optical signal. For example, when the modulated optical signal is a PWM optical signal, the amplitude of the DC power is represented by the frequency and / or width of the optical pulse. The DC power converter 310 can be a photovoltaic unit, for example, which directly converts the optical signal into an electrical signal using the photovoltaic effect.

[0047] According to an embodiment, the clock recovery circuit 315 recovers the embedded clock signal from the modulated optical signal. The clock recovery circuit 315 can be, for example, an edge detector, a phase detector, or a frequency detector. As is well known in the art, the detector of the clock recovery circuit depends on the optical encoding method of the clock. The recovery of the DC power and the embedded clock signal can be performed in any order, or simultaneously. The DC power converter 310 outputs DC power (Vcc), and the clock recovery circuit 315 outputs the recovered clock signal (Clk) to other components of the measurement node 130 discussed below.

[0048] The measurement node 130 is shown connected to an ECG electrode 138, which is attached to the skin of the subject 201 to receive small analog ECG pulses that may be in the μV to mV range. The measurement node 130 provides an analog front end for the ECG electrode 138, including an optional programmable gain amplifier (PGA) 320 (indicated by a dashed line) and a voltage to frequency converter (VFC) 330, as well as an optical converter 340. As shown, the PGA 320, the VFC 330, and the optical converter 340 all receive DC power (Vcc) from the DC power converter 310. In addition, optionally, each of the PGA 320, the VFC 330, and the optical converter 340 receives a recovered clock signal (Clk) from the clock recovery circuit 315. Therefore, the PGA 320, the VFC 330, and the optical converter 340 can be powered using DC power (Vcc) without a power supply, and can optionally be synchronized with each other using the recovered clock signal (Clk).

[0049] PGA 320 receives analog ECG pulses from ECG electrodes 138, which are electrical signals. VFC 330 converts ECG pulses to the frequency domain, and the digital signal (FREQ-OUT) is used to modulate the frequency set of each ECG measurement node. This minimizes signal attenuation from noise sources and avoids interference with MRI when implemented in an MRI environment. In addition, the use of VFC can eliminate the need for synchronized distributed clocks within the ECG system. VFC also encodes analog ECG pulses with extremely low power, thereby reducing the power requirements of the ECG system.

[0050] According to an embodiment, the VFC 330 of each of the measurement nodes 110, 120, and 130 and the common node 140 can frequency encode ECG pulses received from corresponding ECG electrodes at different frequencies. Therefore, the ECG system can be configured to be configured to identify different frequencies of frequency-encoded ECG pulses, and thereby determine which node is transmitting or determine the information transmitted based on the identified frequency. In addition, the VFC 330 can be designed or selected to encode ECG pulses at a frequency that does not interfere with MRI or other environments in which the ECG system is implemented.

[0051] The optical converter 340 receives the frequency modulated data stream from the VFC 330 and converts it into an optical ECG signal. For example, the optical converter 340 can be a laser or LED light source. The optical converter 340 outputs the optical ECG signal to the optical demodulator 232 of the ECG module 230 via the output fiber optic cable 132.

[0052] Each of the DC power converter 310, clock recovery circuit 315, PGA 320, VFC 330, and optical converter 340 is connected to a virtual ground (V-gnd) created by common node 140 via conductive path 135. Thus, the DC power and clock recovery circuit 315, PGA 320, VFC 330, and optical converter 340 are grounded to a common potential along with components of other measurement nodes (e.g., measurement nodes 110, 120) without having to be electrically grounded elsewhere in the ECG system 200. The recovered DC power and virtual grounding of measurement node 130 eliminates the need for electrical wires connecting measurement node 130 to an external power source and ground.

[0053] All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and / or ordinary meanings of the defined terms.

[0054] As used herein in the specification and claims, the terms "a" and "an" should be understood to mean "at least one" unless expressly stated otherwise.

[0055] The phrase "and / or" as used in the specification and claims herein should be understood to mean "one or both" of the elements so combined, i.e., the elements are present in combination in some cases, and separately in other cases. Multiple elements listed with "and / or" should be interpreted in the same manner, i.e., "one or more" elements so connected. Optionally, other elements may be present in addition to the elements specifically identified by the "and / or" clause, whether related or unrelated to those elements specifically identified.

[0056] As used herein in the specification and claims, "or" should be understood to have the same meaning as "and / or" defined above. For example, when separating items in a list, "or" or "and / or" should be interpreted as inclusive, that is, including at least one of several elements or a list of elements, but also including more than one, and optionally, additional unlisted items. Only when the opposite term is clearly indicated, such as "only one" or "exactly one", or when "consisting of..." is used in the claims, it will refer to an exact element in a list of several elements or elements. In general, the term "or" used in this article should be interpreted as indicating exclusive alternatives only when it is preceded by an exclusive term (i.e., "one or the other but not both"), such as "either", "one of", "only one of" or "exactly one of".

[0057] As used herein in the specification and claims, the phrase "at least one", in reference to a list of one or more elements, should be understood to mean at least one element selected from one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed in the list of elements, and not excluding any combination of elements in the list of elements. This definition also allows for the optional presence of elements other than the elements specifically identified in the list of elements to which the phrase "at least one" refers, whether related or unrelated to the specifically identified elements.

[0058] It should also be understood that, in any method claimed herein that includes more than one step or action, the order of the method steps or actions is not necessarily limited to the order in which the method steps or actions are described unless explicitly stated otherwise.

[0059] In the claims and the above description, all transitional phrases such as "include", "comprising", "carrying", "having", "containing", "involving", "holding" shall be understood as open-ended, i.e., meaning including but not limited to the above. Only the transitional phrases "consisting of" and "consisting essentially of" shall be closed or semi-closed transitional phrases, respectively.

[0060] Although several innovative embodiments have been described and illustrated herein, a person skilled in the art will readily envision a variety of other ways and / or structures for performing the functions and / or obtaining the results and / or one or more of the advantages described herein, and each of such variations and / or modifications is shown as being within the scope of the innovative embodiments described herein. More generally, a person skilled in the art will readily recognize that all parameters, dimensions, materials, and configurations described herein are intended to be exemplary, and that the actual parameters, dimensions, materials, and / or configurations will depend on the specific application or application to which the innovative teachings are used. A person skilled in the art will recognize or be able to determine many equivalents of the specific inventive embodiments described herein using no more than routine experimentation. Therefore, it should be understood that the foregoing embodiments are presented only by way of example, and within the scope of the appended claims and their equivalents, the inventive embodiments may be practiced in a manner different from that specifically described and claimed. The innovative embodiments of the present disclosure relate to each individual feature, system, article, material, complete set of equipment, and / or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits and / or methods, if such features, systems, articles, materials, kits and / or methods are not mutually inconsistent, are included within the innovative scope of the present disclosure.

Claims

1. A system for acquiring electrocardiogram (ECG) pulses from a subject, the system comprising: Virtual ground; as well as a plurality of measurement nodes connectable to a plurality of corresponding ECG electrodes, wherein each of the plurality of corresponding ECG electrodes is attachable to the subject, wherein the plurality of measurement nodes are connected to the virtual ground, and wherein each of the plurality of measurement nodes comprises: a voltage-to-frequency converter (VFC) configured to convert the ECG signal from the corresponding ECG electrode into a frequency signal; an optical converter configured to: convert the frequency signal from the VFC into an optical signal and output the optical signal via an output optical fiber cable; and A DC power converter is configured to receive a modulated optical signal via an input fiber optic cable, recover DC power from the modulated optical signal, and provide the DC power to at least the VFC and the optical converter.

2. The system according to claim 1, wherein: The modulated optical signal includes an embedded clock signal, and wherein the system further includes: a clock recovery circuit for each of the plurality of measurement nodes, the clock recovery circuit being configured to: receive the modulated optical signal with the embedded clock signal via the input optical fiber cable, recover the embedded clock signal from the modulated optical signal, and provide the recovered clock signal to at least the VFC and the optical converter for synchronization.

3. The system according to claim 1, further comprising: The ECG module is configured to provide the modulated optical signals to the plurality of measurement nodes via the input optical fiber cables, respectively, receive the optical signals from the plurality of measurement nodes via the output optical fiber cables, respectively, and convert the optical signals into the ECG pulses.

4. The system according to claim 1, wherein: The plurality of measurement nodes include a left arm (LA) measurement node, a right arm (RA) measurement node, a left leg (LL) measurement node, and a right leg (RL) measurement node.

5. The system according to claim 1, wherein: The DC power converter of each measurement node of the plurality of measurement nodes includes a photovoltaic cell.

6. The system according to claim 1, wherein: Each of the plurality of measurement nodes further comprises: A programmable gain amplifier (PGA) is connected to an input of the VFC and is configured to amplify the ECG signal.

7. The system of claim 1, further comprising: A monitor is configured to display the ECG pulses output by the ECG module.

8. The system according to claim 1, wherein: The subject is positioned within a magnetic resonance imaging (MRI) bore while the ECG pulses are acquired.

9. The system according to claim 1, wherein: The modulated optical signal comprises a pulse width modulated (PWM) optical signal.

10. The system according to claim 1, wherein: The modulated optical signal includes a frequency modulated or amplitude modulated optical signal.

11. The system according to claim 1, wherein: The VFC of each measurement node is configured to convert the ECG signal into a different frequency signal relative to each other measurement node.

12. A system for acquiring electrocardiogram (ECG) pulses from a subject, the system comprising: Virtual ground; a plurality of measurement nodes connectable to a plurality of corresponding ECG electrodes, wherein each of the plurality of corresponding ECG electrodes is attachable to the subject and includes a left arm (LA) measurement node, a right arm (RA) measurement node, and a left leg (LL) measurement node, and a right leg (RL) measurement node, wherein the plurality of measurement nodes are connected to the virtual ground, and wherein each of the plurality of measurement nodes includes: a programmable gain amplifier (PGA) configured to amplify the ECG signal; a voltage-to-frequency converter (VFC) configured to convert the ECG signal into a frequency signal; an optical converter configured to: convert the frequency signal from the VFC into an optical signal and output the optical signal via an output optical fiber cable; and a DC power converter configured to receive a modulated optical signal via an input fiber optic cable, recover DC power from the modulated optical signal, and provide the DC power to at least the VFC and the optical converter; an ECG module configured to: provide the modulated optical signals to the plurality of measurement nodes via the input optical fiber cables, respectively, receive the optical signals from the plurality of measurement nodes via the output optical fiber cables, respectively, and convert the optical signals into the ECG pulses; and A monitor is configured to display the ECG pulses output by the ECG module.

13. The system according to claim 12, wherein: The modulated optical signal includes an embedded clock signal, and wherein the system further includes: a clock recovery circuit for each of the plurality of measurement nodes, the clock recovery circuit being configured to: receive the modulated optical signal with the embedded clock signal via the input optical fiber cable, recover the embedded clock signal from the modulated optical signal, and provide the recovered clock signal to at least the VFC and the optical converter for synchronization.

14. The system according to claim 12, wherein: The subject is positioned within a magnetic resonance imaging (MRI) bore while the ECG pulses are acquired.

15. The system of claim 12, wherein: The VFC of each measurement node is configured to convert the ECG signal into a different frequency signal relative to each other measurement node.

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