Device and method for removing ECG signal drift and outputting gating signal

Abstract

The invention relates to a device and method for removing ECG signal drift and outputting a gating signal, and the method comprises the steps: a high-pass filter which removes a DC component and extremely low noise from an original signal to obtain a first signal; the first amplifier is used for amplifying the first signal; the low-pass filter is used for performing low-frequency component extraction on the amplified first signal; a non-linear processor performing non-linear integration on the low-frequency component; the second amplifier is used for amplifying the low-frequency component subjected to nonlinear integration to obtain a second signal; the summator is used for subtracting the second signal from the first signal to obtain a third signal; the third amplifier is used for amplifying the third signal; the pulse discriminator is used for discriminating an effective pulse signal in the amplified third signal and generating a pulse signal; and the level converter is used for performing level conversion on the pulse signal and outputting a gating signal. The beneficial effects are that extraction of effective pulse signals is substantially improved, interconnection with a rear-end circuit is more reliable and convenient, and PET / CT imaging quality can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the field of radiation detection technology, and in particular to a device and method for removing ECG signal drift and outputting a gating signal. Background Art

[0002] PET (Positron Emission Tomography) is a clinical diagnostic imaging technology in the field of nuclear medicine. Its basic principle is to inject a tracer containing positron-emitting radionuclides into a living body, and then detect the energy, time and position information of 511keV gamma rays emitted in the opposite direction when the positrons are annihilated in vitro. Finally, the location of the lesion is determined by statistically reconstructing the location of the annihilation event. This three-dimensional imaging non-destructive detection technology has the characteristics of high sensitivity, good accuracy and the ability to perform functional imaging.

[0003] However, PET / CT imaging of the chest and abdomen is still significantly affected by respiratory motion (RM) and cardiac contraction, resulting in respiratory motion artifacts in the reconstructed images. Common clinical methods to avoid respiratory motion artifacts include prone scanning, breath-hold scanning, 4D-CT, reconstruction without attenuation correction, hardware-based and data-driven respiratory gating reconstruction, etc.

[0004] The oldest and most straightforward method of reducing cardiopulmonary artifacts is to synchronize data acquisition with the cardiac or respiratory cycle, a process called gating or triggering. Triggering means that data acquisition begins only after the desired physiological event (R wave, peripheral pulse, or specific level of inspiration) is detected. Gating is the continuous acquisition of data (not in response to specific cardiopulmonary "trigger" events) while recording the EKG, pulse, or respiratory level, and the data can then be reordered, grouped, or associated with the phase of the cardiopulmonary cycle.

[0005] Cardiac contractions can be detected by an electrocardiogram or a peripheral pulse sensor. Some kind of EKG-based triggering is mandatory for cardiac imaging (and is often recommended for imaging of the lower chest). Peripheral pulse gating cannot be used for cardiac imaging due to the long and unpredictable delay between cardiac contraction and the arrival of the pulse wave at the finger. Peripheral pulse gating is often used for peripheral MRA and cine CSF scans.

[0006] Respiratory expansion can be monitored by using a chest strap, bellows, or pads. For a "chest respirator", the belt should be placed around the lower chest, and for an "abdominal respirator", it should be placed around the mid-abdomen. Common respiratory monitoring systems include: electrical impedance ECG monitors that measure changes in electrical potential around the chest and abdomen, temperature-sensitive monitoring systems that measure changes in air convection and temperature during breathing, spirometers that measure changes in lung volume, and real-time position monitoring systems that track and measure the movement of infrared reflective markers fixed to the patient's chest.

[0007] In these hardware-based gating technologies, the slow drift of the original signal will have a great impact on the acquisition of the gated signal. If the noise is too large, the accuracy of the gated signal will be reduced. Taking ECG signals as an example, ECG signals contain multiple types of noise, baseline drift, power supply interference, EMG noise and electrode movement noise. Baseline drift is a low-frequency noise with a frequency of about 0.5 to 0.6 Hz, the low-frequency noise of power supply interference is 50 to 50 Hz, the frequency of EMG noise is slightly greater than 100 Hz, and the electrode movement noise requires the subject to reduce activity. Summary of the invention

[0008] Technical issues to be solved

[0009] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a device and method for removing ECG signal drift and outputting a gating signal, which solves the technical problem of how to improve the PET / CT imaging quality.

[0010] Technical Solution

[0011] In order to achieve the above object, the main technical solutions adopted by the present invention include:

[0012] In a first aspect, the present invention provides a device for removing ECG signal drift and outputting a gating signal, comprising:

[0013] A high-pass filter removes a DC component and very low noise from the original signal to obtain a first signal;

[0014] A first amplifier amplifies the first signal;

[0015] The feedback loop includes: a low-pass filter, a nonlinear processor and a second amplifier; the low-pass filter extracts the low-frequency component of the amplified first signal; the nonlinear processor performs nonlinear integration on the low-frequency component; the second amplifier amplifies the low-frequency component after the nonlinear integration to obtain the second signal;

[0016] A summer, which subtracts the second signal from the first signal to obtain a third signal;

[0017] a third amplifier, for amplifying the third signal;

[0018] a pulse discriminator for discriminating a valid pulse signal in the amplified third signal and generating a pulse signal;

[0019] The level converter converts the pulse signal into a level and outputs a gating signal.

[0020] Optionally, the feedback loop includes an internally triggered gated BLR circuit or a BLR circuit with a DC servo loop.

[0021] Optionally, when the input signal of the feedback loop is less than a preset value, the internally triggered gated BLR circuit feeds back the input signal which is less than the preset value to the main loop.

[0022] Optionally, in the BLR circuit with a DC servo loop, the low-pass filter is an RC low-pass filter, and the nonlinear processor is an integration circuit.

[0023] Optionally, the pulse discriminator includes a CR-LR circuit and a high-speed comparison circuit, and the CR-LR circuit and the high-speed comparison circuit perform an AND operation.

[0024] In a second aspect, the present invention provides a method for removing ECG signal drift and outputting a gating signal, which is used in the device described in any of the above technical solutions, and the method comprises:

[0025] Removing a DC component and extremely low noise from the original signal to obtain a first signal;

[0026] amplifying the first signal;

[0027] Extracting low-frequency components from the amplified first signal;

[0028] Perform nonlinear integration on low-frequency components;

[0029] Amplifying the low-frequency component after nonlinear integration to obtain a second signal;

[0030] Subtract the second signal from the first signal to obtain a third signal;

[0031] amplifying the third signal;

[0032] identifying a valid pulse signal in the amplified third signal and generating a pulse signal;

[0033] Perform level conversion on the pulse signal and output the gate signal.

[0034] In a third aspect, the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein when the program is executed, the method for removing ECG signal drift and outputting a gating signal as described in any one of the first aspects above is implemented.

[0035] In a fourth aspect, the present invention provides a storage device comprising a storage medium and a processor, wherein the storage medium stores a computer program, and when the program is executed by the processor, the method of removing ECG signal drift and outputting a gating signal as described in any one of the first aspects above is implemented.

[0036] Beneficial Effects

[0037] The beneficial effects of the present invention are as follows: the device for removing ECG signal drift and outputting a gating signal of the present invention uses signal processing technology to remove the influence of most low-frequency noise on the original signal of the hardware gating device, such as the ECG signal, and generates a reliable gating signal. The application of this gating signal makes the grouping and sorting of data obtained by PET / CT continuous scanning more reasonable and accurate, significantly improves the extraction of effective pulse signals, and is more reliably and conveniently interconnected with the back-end circuit, thereby effectively improving the imaging quality of PET / CT. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 A baseline drift waveform diagram provided by an embodiment of the present invention;

[0039] Figure 2 A power supply interference waveform diagram provided by an embodiment of the present invention;

[0040] Figure 3 An EMG noise waveform diagram provided by an embodiment of the present invention;

[0041] Figure 4 A schematic diagram of a process for removing ECG signal drift and outputting a gated signal provided in an embodiment of the present invention;

[0042] Figure 5 A schematic diagram of the principle of an internally triggered gated BLR circuit provided by an embodiment of the present invention;

[0043] Figure 6 Schematic diagram of an example of an internally triggered gated BLR circuit provided by an embodiment of the present invention

[0044] Figure 7 A schematic diagram of the BLR circuit principle with a DC servo loop provided in an embodiment of the present invention;

[0045] Figure 8 A schematic diagram of an example of a BLR circuit with a DC servo loop provided in an embodiment of the present invention;

[0046] Fig. 9 A schematic diagram of test results of a gated BLR circuit using internal triggering provided in an embodiment of the present invention;

[0047] Fig.10A schematic diagram of test results of a BLR circuit with a DC servo loop provided in an embodiment of the present invention;

[0048] Fig.11 A schematic diagram of a CR-LR circuit provided by an embodiment of the present invention;

[0049] Fig.12 A schematic diagram of a high-speed comparison circuit provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0050] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below through specific implementation modes in conjunction with the accompanying drawings.

[0051] The purpose of the present invention is to use a signal processing technology to remove the influence of most low-frequency noise on the original signal of the hardware gating device, such as ECG signal, and generate a reliable gating signal. The application of this gating signal will make the grouping and sorting of the data obtained by the continuous scanning of PET / CT more reasonable and accurate, thereby effectively improving the imaging quality of PET / CT.

[0052] In order to better understand the above technical solution, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a clearer and more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0053] ECG signals contain many types of noise, including baseline drift, power supply interference, EMG noise, and electrode movement noise. Baseline drift is a low-frequency noise with a frequency of about 0.5 to 0.6 Hz. Its waveform is as follows: Figure 1 The low-frequency noise of power supply interference is 50~50Hz, and its waveform is as follows Figure 2 The frequency of EMG noise is slightly greater than 100 Hz, and its waveform is as follows Figure 3 shown.

[0054] In order to effectively suppress the above noise, the baseline restoration technology (BLR, Basic Line Restoration) can be used to process it. The complete signal processing process is as follows: Figure 4As shown. The principle is as follows: Generally speaking, pulse signals with higher frequencies and higher amplitudes are used to generate gated signals. If there are no low-frequency noise signals and the threshold signal is set appropriately, each pulse signal will generate a gated signal. Such a gated signal is very real, even if the pulse signal amplitude is slightly lower. If a low-frequency noise signal is superimposed, the amplitude of pulse glitch signals (another type of noise) with an amplitude lower than the effective pulse signal and a frequency higher than the low-frequency noise will be increased after superposition, which will also generate some erroneous gated signals. Therefore, filtering out those low-frequency noise signals will reduce the interference of pulse glitch signals and make the gated signal more real.

[0055] First, refer to Figure 4 This embodiment provides a device for removing ECG signal drift and outputting a gating signal, comprising:

[0056] The high-pass filter is a high-pass filter with a low cut-off frequency, which removes the DC component and very low noise from the original signal to obtain the first signal.

[0057] The first amplifier amplifies the first signal.

[0058] The feedback loop includes: a low-pass filter, a nonlinear processor and a second amplifier. The low-pass filter extracts the low-frequency component of the amplified first signal. The nonlinear processor performs nonlinear integration on the low-frequency component. The second amplifier amplifies the low-frequency component after nonlinear integration to obtain a second signal, and feeds it back to the main signal path.

[0059] The summer subtracts the second signal from the first signal to obtain the third signal, which is equivalent to removing the low-frequency component in the first signal.

[0060] The third amplifier amplifies the third signal.

[0061] The pulse discriminator discriminates the effective pulse signal in the amplified third signal and generates a reliable pulse signal.

[0062] The level converter converts the pulse signal to output the gate signal, matches the level with the back-end circuit, and provides the necessary safety isolation.

[0063] Optionally, the feedback loop includes an internally triggered gated BLR circuit or a BLR circuit with a DC servo loop.

[0064] Optionally, when the input signal of the feedback loop is less than a preset value, the internally triggered gated BLR circuit feeds back the input signal which is less than the preset value to the main loop.

[0065] The principle of the internally triggered gated BLR circuit is as follows Figure 5As shown. If the input signal of the feedback loop is less than a certain set threshold, it will be fed back to the main loop through the feedback loop. This threshold is related to the baseline. In practical applications, the following can be adopted Figure 6 The circuit shown.

[0066] Optionally, in the BLR circuit with a DC servo loop, the low-pass filter is an RC low-pass filter, and the nonlinear processor is an integration circuit.

[0067] The principle of BLR circuit with DC servo loop is as follows Figure 7 In practical applications, the following can be adopted Figure 8 The circuit shown. The LPF circuit is implemented by RC low-pass filtering. The NON-LINEAR BUFFER is implemented by an integrating circuit. Increasing R3 can enhance the recovery ability, but at the same time it will increase the noise. The -3dB cutoff frequency is shown in the following formula:

[0068] The test results of the internally triggered gated BLR circuit and the BLR circuit with a DC servo loop are shown in Figure 2. Figure 7 and Figure 8 As shown in the figure, the low-frequency baseline changes are eliminated. Figure 7 It can also be seen that the gain of the circuit is set to be small. Figure 8 The gain is relatively large, so some small glitches also appear. Therefore, it is also necessary to carefully consider the selection of the appropriate gain according to the input signal size.

[0069] Optionally, the pulse discriminator includes a CR-LR circuit and a high-speed comparison circuit, and the CR-LR circuit and the high-speed comparison circuit perform an AND operation.

[0070] The pulse discriminator discriminates the processed signal and outputs a pulse width signal with a variable pulse width. The discriminator consists of two types, CR-LR circuit and high-speed comparison circuit, respectively. Fig. 9 and Fig.10 The AND operation of the two circuits can avoid the noise components with lower amplitude from triggering the generation of pulse signals, thus further improving the reliability of identification of useful signals.

[0071] In a second aspect, this embodiment provides a method for removing ECG signal drift and outputting a gating signal, which is used in a device of any of the above embodiments, and the method includes:

[0072] Removing a DC component and extremely low noise from the original signal to obtain a first signal;

[0073] amplifying the first signal;

[0074] Extracting low-frequency components from the amplified first signal;

[0075] Perform nonlinear integration on low-frequency components;

[0076] Amplifying the low-frequency component after nonlinear integration to obtain a second signal;

[0077] Subtract the second signal from the first signal to obtain a third signal;

[0078] amplifying the third signal;

[0079] identifying a valid pulse signal in the amplified third signal and generating a pulse signal;

[0080] Perform level conversion on the pulse signal and output the gate signal.

[0081] According to the method for removing ECG signal drift and outputting a gating signal provided in this embodiment, since it is used in a device for removing ECG signal drift and outputting a gating signal provided in the first aspect of the present invention, the method for removing ECG signal drift and outputting a gating signal has all the technical effects of the device for removing ECG signal drift and outputting a gating signal, and will not be repeated here.

[0082] In a third aspect, an embodiment of the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed, implements any of the above-mentioned methods for removing ECG signal drift and outputting a gating signal.

[0083] In a fourth aspect, an embodiment of the present invention provides a storage device, including a storage medium and a processor, wherein the storage medium stores a computer program, and when the program is executed by the processor, it implements any of the above-mentioned methods for removing ECG signal drift and outputting a gating signal.

[0084] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, devices or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0085] Obviously, those skilled in the art can make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention should also include these modifications and variations.

[0086] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may alter, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A device for removing ECG signal drift and outputting a gating signal, characterized in that: include: A high-pass filter removes a DC component and very low noise from the original signal to obtain a first signal; A first amplifier amplifies the first signal; The feedback loop includes: a low-pass filter, a nonlinear processor and a second amplifier; the low-pass filter extracts the low-frequency component of the amplified first signal; the nonlinear processor performs nonlinear integration on the low-frequency component; the second amplifier amplifies the low-frequency component after the nonlinear integration to obtain the second signal; A summer, which subtracts the second signal from the first signal to obtain a third signal; a third amplifier, for amplifying the third signal; a pulse discriminator for discriminating a valid pulse signal in the amplified third signal and generating a pulse signal; The level converter converts the pulse signal into a level and outputs a gating signal.

2. A device for removing ECG signal drift and outputting a gating signal according to claim 1, characterized in that: The feedback loop includes an internally triggered gated BLR circuit or a BLR circuit with a DC servo loop.

3. A device for removing ECG signal drift and outputting a gating signal according to claim 2, characterized in that: When the input signal of the feedback loop is less than the preset value, the internally triggered gated BLR circuit feeds back the input signal which is less than the preset value to the main loop.

4. The device for removing ECG signal drift and outputting a gating signal according to claim 3, characterized in that: In the BLR circuit with a DC servo loop, the low-pass filter is an RC low-pass filter, and the nonlinear processor is an integration circuit.

5. The device for removing ECG signal drift and outputting a gating signal according to claim 4, characterized in that: The pulse discriminator comprises a CR-LR circuit and a high-speed comparison circuit, and the CR-LR circuit and the high-speed comparison circuit perform an AND operation.

6. A method for removing ECG signal drift and outputting a gating signal, characterized in that: For use in an apparatus as claimed in any one of claims 1 to 5, the method comprising: Removing a DC component and extremely low noise from the original signal to obtain a first signal; amplifying the first signal; Extracting low-frequency components from the amplified first signal; Perform nonlinear integration on low-frequency components; Amplifying the low-frequency component after nonlinear integration to obtain a second signal; Subtract the second signal from the first signal to obtain a third signal; amplifying the third signal; identifying a valid pulse signal in the amplified third signal and generating a pulse signal; Perform level conversion on the pulse signal and output the gate signal.

7. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method of removing ECG signal drift and outputting a gating signal as claimed in claim 6 is implemented.

8. A storage device comprising a storage medium and a processor, wherein the storage medium stores a computer program, characterized in that: When the processor executes the computer program, the method of removing ECG signal drift and outputting a gating signal as described in claim 6 is implemented.

Images