CN115808648A - Device and method for measuring ringing noise of magnetic resonance system - Google Patents
Device and method for measuring ringing noise of magnetic resonance system Download PDFInfo
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Abstract
The invention discloses a device and a method for measuring ringing noise of a magnetic resonance system, wherein the method comprises the following steps: controlling a radio frequency power amplifier to apply radio frequency pulses through a nuclear magnetic resonance spectrometer, acquiring a first signal through a radio frequency coil by a preset signal acquisition method, and acquiring a second signal through a ringing noise detection probe; calculating a correlation coefficient between the radio frequency coil and the ringing noise detection probe according to the first signal and the second signal; and eliminating the ringing noise in the signals collected by the radio frequency coil by using the ringing signal detected by the ringing noise detection probe according to the correlation coefficient. The method can eliminate ringing noise in single acquisition, can meet the application occasions with high real-time requirements, can calculate the result through a single time for a motion sensitive sequence, such as an SE-dispersion sequence, is insensitive to motion, and can improve the accuracy and stability of apparent diffusion coefficient measurement.
Description
Technical Field
The invention belongs to the technical field of magnetic resonance, and particularly relates to a device and a method for measuring ringing noise of a magnetic resonance system.
Background
When a radio frequency pulse is emitted during the detection of Nuclear Magnetic Resonance (NMR), an oscillation current flowing through an antenna can cause the instrument to vibrate, and a motor effect, namely ringing, is caused. Although ringing noise is attenuated quickly, it is still present during echo detection, and the amplitude of ringing is typically high, which has a significant effect on the measurement result, so that it is necessary to eliminate ringing noise to ensure that the measurement result is accurate.
In the prior art, noise is mainly eliminated by a cross-phase pulse pair sequence (PAPS) or a phase cycle method, and an acquired echo signal Y of the CPMG sequence is represented as:
Y＝S+R； (1)
where S represents the NMR signal and R represents ringing noise.
By changing the phases of the excitation and convergence pulses of the CPMG sequence, for example, the first TR uses [0 °,90 ° ] and the second TR uses [180 °,90 ° ], the phases of the ringing noise and the NMR signal are reversed, i.e.:
Y1＝S+R； (2)
Y2＝S-R； (3)
wherein Y1 and Y2 represent signals acquired by the first TR and the second TR, respectively.
From the equations (2) and (3), it is understood that the NMR signal S = (Y1 + Y2)/2 and the ringing noise R = (Y1-Y2)/2 after the ringing noise is removed.
Although the phase cycling method is simple and effective and widely used, the disadvantages of the method are that: at least two TR signals are required to eliminate ringing noise, the real-time performance is not high, and the ringing noise is easily influenced by motion.
In addition, the prior art also reduces ringing noise by a Q-Switch method, which turns on a radio frequency coil with another high-loss coil after the radio frequency pulse is transmitted, so that the energy is quickly attenuated. However, this method can only shorten the ringing time, but cannot completely eliminate the ringing.
Disclosure of Invention
The invention aims to provide a device and a method for measuring ringing noise of a magnetic resonance system, which are used for solving the technical problem that the ringing noise needs to be eliminated or cannot be completely eliminated by acquiring signals of at least two TRs in the prior art.
In order to achieve the purpose, the invention adopts the following technical scheme:
the first aspect provides a measuring device for ringing noise of a magnetic resonance system, which comprises a nuclear magnetic resonance spectrometer, a radio frequency power amplifier, a receiving-transmitting conversion switch, a magnet, a radio frequency coil, a preamplifier and at least one ringing noise detection probe connected with the preamplifier;
the size of the at least one ringing noise detection probe is smaller than a size threshold, and the distance between the at least one ringing noise detection probe and the detected object is larger than a distance threshold, so that the detection probe can detect the magnetic resonance signal of the detected object as less as possible; meanwhile, the at least one ringing noise detection probe keeps a preset distance and a preset spatial distribution with the radio frequency coil, so that the influence of the detection probe on the radio frequency coil is reduced to be below an influence threshold while the detection probe effectively detects a ringing signal in the radio frequency coil.
In one possible design, the ringing noise detection probe employs a radio frequency coil in a spiral or planar spiral configuration.
A second aspect provides a measurement method applied to the measurement apparatus described in any one of the possible designs of the first aspect, including:
controlling a radio frequency power amplifier to apply radio frequency pulses through a nuclear magnetic resonance spectrometer, acquiring a first signal through a radio frequency coil by a preset signal acquisition method, and acquiring a second signal through a ringing noise detection probe;
calculating a correlation coefficient between the radio frequency coil and the ringing noise detection probe according to the first signal and the second signal;
and eliminating the ringing noise in the signals collected by the radio frequency coil by using the ringing signal detected by the ringing noise detection probe according to the correlation coefficient.
In one possible design, controlling the rf power amplifier to apply the rf pulses by the nmr spectrometer includes:
and controlling a radio frequency power amplifier to sequentially apply an excitation pulse and a plurality of refocusing pulses through a nuclear magnetic resonance spectrometer.
In one possible design, acquiring a first signal by using a radio frequency coil and acquiring a second signal by using a ringing noise detection probe by a preset signal acquisition method includes:
opening the acquisition windows after the 1 st refocusing pulse to the Nth refocusing pulse so that the radio frequency coil acquires a first signal Y through the transceiving switch and other channels of the nuclear magnetic resonance spectrometer receive a second signal Y acquired by the ringing noise detection probe i ；
Wherein the first signal Y = S + R + n; (6)
Wherein S represents a magnetic resonance signal, R represents ringing noise, and n represents noise;
wherein the second signal Y i ＝c i R+n i ； (7)
Wherein i represents the ith ringing noise detection probe, c i Representing a correlation coefficient, n, of the ringing noise detection probe with the radio frequency coil i Representing the noise collected by the ith ringing noise detection probe.
In one possible design, acquiring a first signal by using a radio frequency coil and acquiring a second signal by using a ringing noise detection probe by a preset signal acquisition method includes:
the acquisition window is opened after the excitation pulse so that both the radio frequency coil and the ringing noise detection probe receive only the ringing signal and not the echo signal.
In one possible design, acquiring a first signal by using a radio frequency coil and acquiring a second signal by using a ringing noise detection probe by a preset signal acquisition method includes:
after all the magnetic resonance echo signals have been acquired and spaced apart by a time TD, at least one test pulse of the same power and the same duration as the echo pulses is applied again, and the acquisition window is opened after the test pulse, so that both the radio frequency coil and the ringing noise detection probe receive only the ringing signal and not the echo signals.
In one possible design, after acquiring the first signal with the radio frequency coil and acquiring the second signal with the ringing noise detection probe, the method further includes:
the detected object is prescanning by adopting a phase cycle method so as to calculate and obtain the ringing noise in the first signal.
In one possible design, calculating a correlation coefficient between the radio frequency coil and the ringing noise detection probe from the first signal and the second signal includes:
according to ringing noise R in the first signal p And ringing noise P of the second signal i And calculating a correlation coefficient W between the radio frequency coil and the ringing noise detection probe, wherein the calculation formula is as follows:
W＝(P T P) -1 P T R； (8)
wherein, the first and the second end of the pipe are connected with each other,
wherein, t 1 To t M Representing different time instants of sampling.
In one possible design, the removing, according to the correlation coefficient, the ringing noise in the signal collected by the radio frequency coil by using the ringing signal detected by the ringing noise detecting probe includes:
and calculating the ringing noise of the radio frequency coil at the moment t according to the correlation coefficient and the signal acquired by the ringing noise detection probe at the moment t, wherein the calculation formula is as follows:
wherein Y is n (t) represents the signal collected by the nth ringing noise detection probe at time t, w n Denotes the n-thDetecting a correlation coefficient of a probe and the radio frequency coil, wherein R (t) represents the ringing noise of the radio frequency coil at the moment t;
according to the ringing noise of the radio frequency coil at the moment t, calculating the magnetic resonance signal acquired by the radio frequency coil, wherein the calculation formula is as follows:
S(t)＝Y(t)-R(t)； (10)
where Y (t) represents the total signal acquired by the radio frequency coil at time t.
A third aspect provides a computer-readable storage medium having instructions stored thereon, which when executed on a computer perform the measurement method as set forth in any one of the possible designs of the second aspect.
A fourth aspect provides a computer device comprising a memory, a processor and a transceiver communicatively connected in sequence, wherein the memory is used for storing a computer program, the transceiver is used for sending and receiving messages, and the processor is used for reading the computer program and executing the measurement method as set forth in any one of the possible designs of the first aspect.
A fifth aspect provides a computer program product comprising instructions which, when run on a computer, cause the computer to perform a measurement method as set out in any one of the possible designs of the first aspect.
Compared with the prior art, the invention has the beneficial effects that:
1. the invention relates to a measuring device of ringing noise of a magnetic resonance system, which is characterized in that at least one ringing noise detection probe is connected to a preamplifier; the size of at least one ringing noise detection probe is smaller than a size threshold value, and the distance between the ringing noise detection probe and the detected object is larger than a distance threshold value, so that the detection probe can detect the magnetic resonance signals of the detected object as less as possible; meanwhile, at least one ringing noise detection probe keeps a preset distance and a preset spatial distribution with the radio frequency coil, so that the influence of the detection probe on the radio frequency coil is reduced to be below an influence threshold while the detection probe effectively detects a ringing signal in the radio frequency coil. Namely, the ringing noise detection probe in the invention is used for detecting the ringing noise as far as possible so as to meet the requirement of a subsequent measurement method.
2. The method for measuring the ringing noise of the magnetic resonance system comprises the steps of acquiring a first signal by using a radio frequency coil through a preset signal acquisition method, and acquiring a second signal by using a ringing noise detection probe; calculating a correlation coefficient between the radio frequency coil and the ringing noise detection probe; and eliminating the ringing noise in the signals collected by the radio frequency coil by using the ringing signal detected by the ringing noise detection probe according to the correlation coefficient. Firstly, the correlation coefficient of the ringing noise in the ringing noise monitoring probe and the radio frequency receiving/transmitting coil is estimated by collecting reference data, then the ringing noise is estimated by utilizing the signal collected by the ringing noise monitoring probe in real time, and the ringing noise is eliminated from the echo signal, so that the magnetic resonance signal without the ringing noise is obtained. Therefore, the elimination of ringing noise can be completed in single acquisition, the application occasions with high real-time requirements can be met, such as real-time detection in petroleum wells, and for motion sensitive sequences, such as SE-dispersion sequences, the result can be calculated through single calculation, the motion is insensitive, and the accuracy and the stability of apparent diffusion coefficient measurement can be improved.
Drawings
Fig. 1 is a block diagram of a ringing noise measurement device of a magnetic resonance system in an embodiment of the present application;
fig. 2 is a flowchart of a method for measuring ringing noise of a magnetic resonance system according to an embodiment of the present application;
FIG. 3 is a first sequence chart in the embodiment of the present application;
FIG. 4 is a timing diagram of a second sequence in the embodiment of the present application;
FIG. 5 is a timing diagram of a third sequence in the embodiment of the present application;
FIG. 6 is a graph comparing the results of the measurement method in the examples of the present application with those of the conventional method.
Detailed Description
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the present invention will be briefly described below with reference to the accompanying drawings and the embodiments or the description in the prior art, it is obvious that the following description of the structure of the drawings is only some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts. It should be noted that the description of the embodiments is provided to help understanding of the present invention, but the present invention is not limited thereto.
Examples
As shown in fig. 1, a first aspect of the embodiments of the present application provides a measuring apparatus for ringing noise of a magnetic resonance system, including a nuclear magnetic resonance spectrometer, a radio frequency power amplifier, a transmit-receive switch, a magnet, a radio frequency coil, a preamplifier, and at least one ringing noise detecting probe connected to the preamplifier;
the size of the at least one ringing noise detection probe is smaller than a size threshold, and the distance from the detected object is larger than a distance threshold, so that the detection probe can detect the magnetic resonance signal of the detected object as less as possible; meanwhile, the at least one ringing noise detection probe keeps a preset distance and a preset spatial distribution with the radio frequency coil, so that the detection probe effectively detects the ringing signal in the radio frequency coil and simultaneously the influence on the radio frequency coil is reduced to be below an influence threshold.
It should be noted that, in the embodiment of the present application, connection relationships among the nuclear magnetic resonance spectrometer, the radio frequency power amplifier, the transceiving switch, the magnet, the radio frequency coil, and the preamplifier are all existing connection relationships, and are not described herein again, where a plurality of preamplifiers may be provided, and each preamplifier is correspondingly connected with one ringing noise detection probe. The magnet is used for generating a static gradient magnetic field to polarize a measured object; the magnetic resonance spectrometer is connected with the receiving and transmitting switching module through a radio frequency power amplifier; the receiving and transmitting switching module is used for switching the transmitting state and the receiving state of a radio frequency coil in the magnetic resonance system; the radio frequency coil is connected with the receiving and transmitting switching module; in the transmitting state, the radio frequency coil is used for transmitting radio frequency pulses to a measured object; in a receiving state, the radio frequency coil is used for receiving a nuclear magnetic resonance echo signal generated after a detection target position of a detected object is excited, and receiving ringing noise; the preamplifier is used for amplifying magnetic resonance echo signals and ringing noise; the ringing noise detection probes are used for detecting ringing signals, the number of the ringing noise detection probes can be 1-n, and the more the probes are, the more accurate the detection is.
Specifically, the ringing noise detection probe is small in size and needs to be far away from the object to be detected, so that it cannot detect or detects few magnetic resonance signals. The ringing noise detection probe needs to keep a certain distance and specific spatial distribution with the radio frequency coil, so that the ringing noise detection probe can effectively detect the ringing signal in the radio frequency coil, and small coupling with the radio frequency coil is kept, so that the influence on the radio frequency coil is small, and the requirement of a subsequent measurement method is met.
In one possible design, the ringing noise detection probe adopts a radio frequency coil with a spiral tube structure or a planar spiral tube structure, and the size of the radio frequency coil is smaller; of course, it is understood that the structural arrangement of the radio frequency coil in the embodiment of the present application is not limited to the above example, and other existing coil structures capable of meeting the design requirements of the embodiment of the present application are within the protection scope of the embodiment of the present application, and are not described herein again.
Based on the disclosure, the embodiment of the application connects at least one ringing noise detection probe to the preamplifier; the size of at least one ringing noise detection probe is smaller than a size threshold value, and the distance between the ringing noise detection probe and the detected object is larger than a distance threshold value, so that the detection probe can detect the magnetic resonance signals of the detected object as less as possible; meanwhile, at least one ringing noise detection probe keeps a preset distance and a preset spatial distribution with the radio frequency coil, so that the influence of the detection probe on the radio frequency coil is reduced to be below an influence threshold while the detection probe effectively detects a ringing signal in the radio frequency coil. The ringing noise detection probe is used for detecting the ringing noise as far as possible so as to meet the requirement of a subsequent measurement method.
As shown in fig. 2 to 5, a second aspect of the embodiments of the present application provides a measurement method applied to the measurement apparatus described in any one of the possible designs of the first aspect, including but not limited to the following steps S1 to S3:
s1, controlling a radio frequency power amplifier to apply radio frequency pulses through a nuclear magnetic resonance spectrometer, acquiring a first signal through a radio frequency coil by a preset signal acquisition method, and acquiring a second signal through a ringing noise detection probe;
in step S1, controlling a radio frequency power amplifier to apply a radio frequency pulse by a nuclear magnetic resonance spectrometer, including:
and controlling a radio frequency power amplifier to sequentially apply an excitation pulse and a plurality of refocusing pulses through a nuclear magnetic resonance spectrometer.
It should be noted that the pulse sequence adopted in the embodiment of the present application is preferably a common CPMG sequence, but it should be understood that other existing pulse sequences may also be applied to the embodiment of the present application, and the present application is not limited thereto.
As shown in fig. 3, in a first possible design in step S1, since ringing noise may occur after the excitation pulse and each refocusing pulse, and a magnetic resonance echo signal may occur after each refocusing pulse, a first signal is acquired by using the radio frequency coil and a second signal is acquired by using the ringing noise detection probe by a preset signal acquisition method, which includes:
opening the acquisition windows after the 1 st refocusing pulse to the Nth refocusing pulse so that the radio frequency coil acquires a first signal Y through the transceiving switch and other channels of the nuclear magnetic resonance spectrometer receive a second signal Y acquired by the ringing noise detection probe i ；
Wherein the first signal Y = S + R + n; (6)
Wherein S represents a magnetic resonance signal, R represents ringing noise, and n represents noise;
wherein the second signal Y i ＝c i R+n i ； (7)
Where i denotes the ith ringing noise detection probe, c i Representing a correlation coefficient, n, of the ringing noise detection probe with the radio frequency coil i Representing the noise collected by the ith ringing noise detection probe.
To calculate the correlation coefficient, after acquiring a first signal with the radio frequency coil and a second signal with the ringing noise detection probe, the method further comprises:
the detected object is prescanning by adopting a phase cycle method so as to calculate and obtain the ringing noise in the first signal.
Specifically, the ringing noise in the rf coil is calculated by formula (5), and the ringing noise calculated by the rf coil is denoted as R p The signal received by the ith ringing signal monitoring probe is recorded as P i For use in subsequent correlation coefficient calculations.
As shown in fig. 4, in a second possible design in step S1, acquiring a first signal by using a radio frequency coil and acquiring a second signal by using a ringing noise detection probe by a preset signal acquisition method includes:
the acquisition window is opened after the excitation pulse so that both the radio frequency coil and the ringing noise detection probe receive only the ringing signal and not the echo signal.
Similarly, let R denote the ringing noise received by the RF coil p The signal received by the ith ringing signal monitoring probe is recorded as P i For use in subsequent correlation coefficient calculations.
As shown in fig. 5, in a third possible design in step S1, acquiring a first signal by using a radio frequency coil and acquiring a second signal by using a ringing noise detection probe by a preset signal acquisition method includes:
after all the magnetic resonance echo signals have been acquired and spaced apart by a time TD, at least one test pulse of the same power and the same duration as the echo pulses is applied again, and the acquisition window is opened after the test pulse, so that both the radio frequency coil and the ringing noise detection probe receive only the ringing signal and not the echo signals.
Similarly, let R denote the ringing noise received by the RF coil p The signal received by the ith ringing signal monitoring probe is recorded as P i For use in subsequent correlation coefficient calculations. It is noted that the separation time TD cannot be equal to the separation between two refocusing pulses, and TD should not be too long, otherwise a new magnetic resonance signal will be excited due to the relaxation recovery of T1.
S2, calculating a correlation coefficient between the radio frequency coil and the ringing noise detection probe according to the first signal and the second signal;
in step S2, calculating a correlation coefficient between the radio frequency coil and the ringing noise detection probe from the first signal and the second signal includes:
calculating a correlation coefficient W between the radio frequency coil and the ringing noise detection probe according to the ringing noise Rp in the first signal and the ringing noise Pi of the second signal, wherein the calculation formula is as follows:
W＝(P T P) -1 P T R； (8)
wherein the content of the first and second substances,
wherein, t 1 To t M Representing different time instants of sampling; for example, at the time corresponding to the 1 st to M points when the echo signal is collected, the signal received by the radio frequency coil or the calculated ringing noise is recorded as Rp, and the signal received by the ith ringing signal monitoring probe is recorded as Pi.
And S3, eliminating ringing noise in the signals collected by the radio frequency coil by using the ringing signal detected by the ringing noise detection probe according to the correlation coefficient.
In one possible design of step S3, according to the correlation coefficient, eliminating the ringing noise in the signal collected by the radio frequency coil by using the ringing signal detected by the ringing noise detection probe includes:
and calculating the ringing noise of the radio frequency coil at the moment t according to the correlation coefficient and the signal acquired by the ringing noise detection probe at the moment t, wherein the calculation formula is as follows:
wherein, Y n (t) indicates that the nth ringing noise detection probe is in timeSignal acquired at time t, w n Representing the correlation coefficient of the nth ringing noise detection probe and the radio frequency coil, and R (t) representing the ringing noise of the radio frequency coil at the moment t;
according to the ringing noise of the radio frequency coil at the moment t, calculating the magnetic resonance signal acquired by the radio frequency coil, wherein the calculation formula is as follows:
S(t)＝Y(t)-R(t)； (10)
where Y (t) represents the total signal acquired by the radio frequency coil at time t.
Based on the disclosure, in the embodiment of the application, by a preset signal acquisition method, the radio frequency coil is used for acquiring a first signal, and the ringing noise detection probe is used for acquiring a second signal; calculating a correlation coefficient between the radio frequency coil and the ringing noise detection probe; and eliminating the ringing noise in the signals collected by the radio frequency coil by using the ringing signal detected by the ringing noise detection probe according to the correlation coefficient. Therefore, the elimination of ringing noise can be completed in single acquisition, the application occasions with high real-time requirements can be met, such as real-time detection in petroleum wells, and for motion sensitive sequences, such as SE-dispersion sequences, the result can be calculated through single calculation, the motion is insensitive, and the accuracy and the stability of apparent diffusion coefficient measurement can be improved.
As shown in fig. 6, a graph comparing the results of the ringing noise signal detected by the measurement method in the embodiment of the present application and the ringing noise signal calculated by the conventional phase cycling method (PAPS) is shown. In the embodiment of the application, a CPMG sequence is adopted, the radio frequency pulse width is 120us, the CPMG pulse interval is 700us, 7 ringing noise monitoring probes are adopted, and the radio frequency coil is a small spiral-tube type radio frequency coil. As can be seen from the figure, the measurement method of the embodiment of the present application has a better measurement effect than the conventional phase cycling method.
A third aspect provides a computer-readable storage medium having stored thereon instructions for performing, when running on a computer, a measurement method as set forth in the second aspect or any one of the possible designs of the second aspect.
The computer-readable storage medium refers to a carrier for storing data, and may include, but is not limited to, floppy disks, optical disks, hard disks, flash memories, flash disks and/or Memory sticks (Memory sticks), etc., and the computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices.
For the working process, the working details and the technical effects of the foregoing computer-readable storage medium provided in the third aspect of this embodiment, reference may be made to the method described in any one of the second aspect and the second aspect, which is not described herein again.
A fourth aspect provides a computer device comprising a memory, a processor and a transceiver, wherein the memory is used for storing a computer program, the transceiver is used for sending and receiving messages, and the processor is used for reading the computer program and executing the measurement method according to any one of the second aspect and the second aspect.
For example, the Memory may include, but is not limited to, a Random-Access Memory (RAM), a Read-Only Memory (ROM), a Flash Memory (Flash Memory), a First-in First-out (FIFO), and/or a First-in Last-out (FILO), and the like; the processor may not be limited to the use of a microprocessor model number STM32F105 family; the transceiver may be, but is not limited to, a WiFi (wireless fidelity) wireless transceiver, a bluetooth wireless transceiver, a GPRS (General Packet Radio Service) wireless transceiver, and/or a ZigBee (ZigBee protocol, low power local area network protocol based on ieee802.15.4 standard) wireless transceiver, etc. In addition, the computer device may also include, but is not limited to, a power module, a display screen, and other necessary components.
The working process, working details and technical effects of the foregoing computer device provided in the fourth aspect of this embodiment may refer to the method described in any one of the second aspect or the second aspect, which is not described herein again.
A fifth aspect provides a computer program product comprising instructions which, when run on a computer, cause the computer to perform the measurement method of the second aspect or any one of the possible designs of the second aspect.
For the working process, the working details and the technical effects of the computer program product containing the instructions provided in the fifth aspect of the present embodiment, reference may be made to the method described in any one of the second aspect or the second aspect, which is not described herein again.
Finally, it should be noted that: the above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A measuring device for ringing noise of a magnetic resonance system is characterized by comprising a nuclear magnetic resonance spectrometer, a radio frequency power amplifier, a receiving-transmitting change-over switch, a magnet, a radio frequency coil, a preamplifier and at least one ringing noise detection probe connected with the preamplifier;
the size of the at least one ringing noise detection probe is smaller than a size threshold, and the distance from the detected object is larger than a distance threshold, so that the detection probe can detect the magnetic resonance signal of the detected object as less as possible; meanwhile, the at least one ringing noise detection probe keeps a preset distance and a preset spatial distribution with the radio frequency coil, so that the detection probe effectively detects the ringing signal in the radio frequency coil and simultaneously the influence on the radio frequency coil is reduced to be below an influence threshold.
2. A measurement arrangement for measuring ringing noise in a magnetic resonance system as claimed in claim 1, characterized in that the ringing noise detection probe employs a radio frequency coil of a spiral or planar spiral configuration.
3. A measuring method applied to the measuring apparatus according to claim 1 or 2, comprising:
controlling a radio frequency power amplifier to apply radio frequency pulses through a nuclear magnetic resonance spectrometer, acquiring a first signal through a radio frequency coil by a preset signal acquisition method, and acquiring a second signal through a ringing noise detection probe;
calculating a correlation coefficient between the radio frequency coil and the ringing noise detection probe according to the first signal and the second signal;
and eliminating the ringing noise in the signals collected by the radio frequency coil by using the ringing signal detected by the ringing noise detection probe according to the correlation coefficient.
4. The measurement method according to claim 3, wherein the applying of the radio frequency pulse by controlling a radio frequency power amplifier of the nuclear magnetic resonance spectrometer comprises:
and controlling a radio frequency power amplifier to sequentially apply an excitation pulse and a plurality of refocusing pulses through a nuclear magnetic resonance spectrometer.
5. The measurement method according to claim 4, wherein the acquiring a first signal by a radio frequency coil and a second signal by a ringing noise detection probe by a preset signal acquisition method comprises:
opening the acquisition windows after the 1 st refocusing pulse to the Nth refocusing pulse so that the radio frequency coil acquires a first signal Y through the transceiving switch and other channels of the nuclear magnetic resonance spectrometer receive a second signal Y acquired by the ringing noise detection probe i ；
Wherein the first signal Y = S + R + n; (6)
Wherein S represents a magnetic resonance signal, represents ringing noise, and n represents noise;
wherein the second signal Y i ＝c i R+n i ；(7)
Where i denotes the ith ringing noise detection probe, c i Representing a correlation coefficient, n, of the ringing noise detection probe with the radio frequency coil i Representing the noise collected by the ith ringing noise detection probe.
6. The measurement method according to claim 4, wherein the acquiring a first signal by a radio frequency coil and a second signal by a ringing noise detection probe by a preset signal acquisition method comprises:
the acquisition window is opened after the excitation pulse so that both the radio frequency coil and the ringing noise detection probe receive only the ringing signal and not the echo signal.
7. The measurement method according to claim 4, wherein the acquiring a first signal by a radio frequency coil and a second signal by a ringing noise detection probe by a preset signal acquisition method comprises:
after all the magnetic resonance echo signals have been acquired and spaced apart by a time TD, at least one test pulse of the same power and the same duration as the echo pulses is applied again, and the acquisition window is opened after the test pulse, so that both the radio frequency coil and the ringing noise detection probe receive only the ringing signal and not the echo signals.
8. The measurement method of claim 5, wherein after acquiring the first signal with the radio frequency coil and the second signal with the ringing noise detection probe, the method further comprises:
the detected object is prescanning by adopting a phase cycle method so as to calculate and obtain the ringing noise in the first signal.
9. The measurement method of claim 3, wherein calculating a correlation coefficient between the radio frequency coil and the ringing noise detection probe from the first signal and the second signal comprises:
according to ringing noise R in the first signal p And ringing noise P of the second signal i And calculating a correlation coefficient W between the radio frequency coil and the ringing noise detection probe, wherein the calculation formula is as follows:
W＝(P T P) -1 P T R； (8)
wherein the content of the first and second substances,
wherein, t 1 To t M Representing different time instants of sampling.
10. The method of claim 9, wherein the removing ringing noise from the signal collected by the radio frequency coil using the ringing signal detected by the ringing noise detection probe according to the correlation coefficient comprises:
and calculating the ringing noise of the radio frequency coil at the moment t according to the correlation coefficient and the signal acquired by the ringing noise detection probe at the moment t, wherein the calculation formula is as follows:
wherein, Y n (t) represents the signal collected by the nth ringing noise detection probe at time t, w n Representing the correlation coefficient of the nth ringing noise detection probe and the radio frequency coil, and R (t) representing the ringing noise of the radio frequency coil at the moment t;
according to the ringing noise of the radio frequency coil at the moment t, calculating the magnetic resonance signal acquired by the radio frequency coil, wherein the calculation formula is as follows:
S(t)＝Y(t)-R(t)；(10)
where Y (t) represents the total signal acquired by the radio frequency coil at time t.
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