# US 11,076,809 B2 · Static charge filter for cardiac electrical signals corrupted with static charge and routed to an electrocardiograph (EKG) monitor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,076,809 B2 - Document ID: US11076809B2 - Status: Granted - Kind: B2 - Application number: 15/778,872 - Filed: 2016-12-02 - Published: 2018-12-13 - Granted: 2021-08-03 - Earliest claimed: 2015-12-03 - Assignees: Koninklijke Philips N.V. - Applicants: Koninklijke Philips N.V. - Inventors: Marc Anthony Chappo; David Dennis Salk - Web page: https://patentgrep.com/patent/US11076809B2 ## CPC - A61B 5/7207: {of noise induced by motion artifacts} - A61B 5/308: for electrocardiography [ECG] - A61B 5/352: Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval - A61B 5/7203: {for noise prevention, reduction or removal} - A61B 5/7225: {Details of analogue processing, e.g. isolation amplifier, gain or sensitivity adjustment, filtering, baseline or drift compensation (input circuits for detecting, measuring, or recording bioelectric or biomagnetic signals A61B5/30; specific diagnostic methods using bioelectric or biomagnetic signals A61B5/316)} - A61B 5/7289: {Retrospective gating, i.e. associating measured signals or images with a physiological event after the actual measurement or image acquisition, e.g. by simultaneously recording an additional physiological signal during the measurement or image acquisition} - A61B 5/7292: {Prospective gating, i.e. predicting the occurrence of a physiological event for use as a synchronisation signal} - A61B 6/032: {Transmission computed tomography [CT]} - A61B 6/5288: {involving retrospective matching to a physiological signal} - A61B 6/541: {involving acquisition triggered by a physiological signal} - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) ## Abstract A static charge filter (522) removes static charge in a cardiac electrical signal. The static charge filter includes a first amplifier (608) configured to amplify an input signal, which includes the cardiac electrical signal and static charge from an electrode, which is in a path of an X-ray beam. The static charge filter further includes a limiter (614) configured to limit a maximum voltage of the signal based on a predetermined clamping threshold, producing a voltage clamped signal. The static charge filter further includes a filter (616) configured to filter high frequency components of the voltage clamped signal, producing a filtered signal. The static charge filter further includes a second amplifier (620) configured to scale an amplitude of the filtered signal so that cardiac electrical signal in an output signal has a same voltage level as a voltage level of the cardiac electrical signal in the input signal. ## Claims ### Claim 1 A static charge filter for removing static charge in a cardiac electrical signal, comprising: a first amplifier configured to amplify an input signal by a first gain, producing an amplified signal, which includes the cardiac electrical signal and static charge from one or more electrodes in a path of an X-ray beam; a signal limiter configured to limit a maximum voltage of the amplified signal based on a predetermined clamping threshold, producing a voltage clamped signal; a filter configured to filter high frequency components of the voltage clamped signal, producing a filtered signal; and a second amplifier configured to scale an amplitude of the filtered signal using a second gain so that the cardiac electrical signal in an output signal has approximately a same voltage level as a voltage level of the cardiac electrical signal in the input signal. ### Claim 2 (depends on 1) The static charge filter of claim 1, further comprising: a separate processing channel for each of the one or more electrodes. ### Claim 3 (depends on 2) The static charge filter of claim 2, wherein only one of the separate processing channels is configured to remove static charge, and the other processing channels are pass-through. ### Claim 4 (depends on 2) The static charge filter of claim 2, wherein all of the separate processing channels are configured to remove static charge. ### Claim 5 (depends on 2) The static charge filter of claim 2, further comprising: a feedback loop of the first amplifier configured to automatically adjust the first gain so that the cardiac electrical signal in the amplified signal is at about the predetermined clamping threshold. ### Claim 6 (depends on 1) The static charge filter of claim 1, wherein the signal limiter comprises: an electrical path through the signal limiter; an electrical ground; and a pair of diodes electrically connected between the path and electrical ground in parallel and in reverse polarity, wherein a spike of the static charge in the amplified signal exceeding the predetermined clamping threshold turns one of the diodes on, clamping a maximum voltage of the amplified signal to the predetermined clamping threshold, and reducing the spike. ### Claim 7 (depends on 1) The static charge filter of claim 1, wherein the filter is a clock programmable low pass filter configured to reject the high frequency components out of band harmonics produced by clamping the amplified signal. ### Claim 8 (depends on 1) The static charge filter of claim 1, wherein the filter is a switched capacitor low pass filter. ### Claim 9 (depends on 1) The static charge filter of claim 1, wherein the first gain is a first value A and the second gain is at least a second value 1/A. ### Claim 10 An imaging system, comprising: a gantry with an examination region; an X-ray radiation source configured to produce and transmit X-ray radiation that traverses the examination region; an X-ray sensitive detector array configured to detect the X-ray radiation traversing the examination region and generate projection data; one or more processors configured to reconstruct at least a sub-portion of the projection data and generate an image indicative thereof; and a static charge filter for removing static charge in a cardiac electrical signal, comprising: a first amplifier configured to amplify an input signal by a first gain, producing an amplified signal, which includes the cardiac electrical signal and static charge from one or more electrodes in a path of an X-ray beam; a signal limiter configured to limit a maximum voltage of the amplified signal based on a predetermined clamping threshold, producing a voltage clamped signal; a filter configured to filter high frequency components of the voltage clamped signal, producing a filtered signal; and a second amplifier configured to scale an amplitude of the filtered signal using a second gain so that a cardiac electrical signal in an output signal has approximately a same voltage level as a voltage level of the cardiac electrical signal in the input signal. ### Claim 11 (depends on 10) The imaging system of claim 10, further comprising: an electrocardiogram monitor configured to process signals output by the static charge filter and produce an electrocardiogram waveform. ### Claim 12 (depends on 11) The imaging system of claim 11, wherein the one or more processors is configured to identify R peaks in the electrocardiogram waveform, and wherein the identified R peaks control an operation of the system during at least one of a prospectively gated cardiac scan or a retrospectively gated cardiac scan. ### Claim 13 (depends on 10) The imaging system of claim 10, further comprising: a feedback loop of the first amplifier configured to automatically adjust the first gain so that the cardiac electrical signal in the amplified signal is at about the predetermined clamping threshold. ### Claim 14 (depends on 10) The imaging system of claim 10, wherein the signal limiter comprises: an electrical path through the signal limiter; an electrical ground; and a pair of diodes electrically connected between the path and electrical ground in parallel and in reverse polarity, wherein a spike in the cardiac electrical signal exceeding the predetermined clamping threshold turns one of the diodes on, clamping a maximum voltage of the cardiac electrical signal to the predetermined clamping threshold, reducing the spike in the cardiac electrical signal. ### Claim 15 A method for removing static charge in a cardiac electrical signal, comprising: receiving a cardiac electrical signal from one or more electrodes in a path of an X-ray beam during an imaging examination, wherein the cardiac electrical signal includes static charge; removing a static charge voltage spike from the received cardiac electrical signal, producing a static charge filtered cardiac electrical signal by: amplifying the received cardiac electrical signal by a first gain, producing an amplified signal; clamping a maximum voltage of the amplified signal based on a predetermined clamping threshold, producing a voltage clamped signal; filtering high frequency out of band harmonics of the clamped signal, producing a filtered signal; and scaling an amplitude of the filtered signal using a second gain, which produces an output signal having a voltage level at approximately a voltage level of the input cardiac electrical signal; transmitting the static charge filtered cardiac electrical signal to an electrocardiogram monitor, which processes the static charge filtered cardiac electrical signal and produces an electrocardiogram waveform representing an electrical activity of a heart of the subject. ### Claim 16 (depends on 15) The method of claim 15, further comprising: identifying an R peak in the electrocardiogram waveform; triggering a scan during an acquisition window of a quiet phase of the heart based on the identified R peak; and reconstructing projection data from the scan to generate an image of the heart for the acquisition window for the quiet phase. ### Claim 17 (depends on 15) The method of claim 15, further comprising: identifying an R peak in the electrocardiogram waveform; identifying a sub-set projection data corresponding to an acquisition window of a quiet phase of the heart from a set of projection data covering more than the acquisition window; and reconstructing the sub-set of projection data to generate an image of the heart for the acquisition window for the quiet phase.