CN107656225B

CN107656225B - Magnetic resonance frequency calibration method, magnetic resonance imaging method and system

Info

Publication number: CN107656225B
Application number: CN201711049369.1A
Authority: CN
Inventors: 刘柳; 廖康佳
Original assignee: Shanghai United Imaging Healthcare Co Ltd
Current assignee: Shanghai United Imaging Healthcare Co Ltd
Priority date: 2017-10-31
Filing date: 2017-10-31
Publication date: 2020-08-25
Anticipated expiration: 2037-10-31
Also published as: CN107656225A

Abstract

The embodiment of the invention discloses a magnetic resonance frequency calibration method, a magnetic resonance imaging method and a magnetic resonance imaging system. The magnetic resonance frequency calibration method comprises the following steps: exciting a region to be scanned by utilizing a pre-scanning radio frequency pulse, collecting a plurality of echo signals from the region to be scanned, and determining frequency spectrum lines or frequency spectrum information of the echo signals; identifying peak-to-valley information in the frequency spectral lines or spectral information; and determining the water peak frequency in the frequency spectrum line or the frequency spectrum information according to the peak-valley information based on a preset calibration mode, and determining the water peak frequency as the central frequency of the magnetic resonance system. The embodiment of the invention solves the problem of large identification error rate caused by nonstandard frequency spectrum lines or frequency spectrum information of complicated parts of a human body, realizes the application of different calibration modes according to different scanning parts, intelligently identifies the water peak frequency in the frequency spectrum lines or the frequency spectrum information, and improves the flexibility and the calibration precision of the frequency calibration of a magnetic resonance system.

Description

Magnetic resonance frequency calibration method, magnetic resonance imaging method and system

Technical Field

The embodiments of the present invention relate to magnetic resonance technology, and in particular, to a magnetic resonance frequency calibration method, a magnetic resonance imaging apparatus, and a magnetic resonance imaging system.

Background

In a magnetic resonance system, the larmor frequency of the precession of the proton spins is ω ═ γ B₀Where gamma is the gyromagnetic ratio of the proton, B₀Is the static magnetic field strength at which the protons are located. However, in an actual imaging process, the static magnetic field of the magnetic resonance system is not absolutely uniform, and further, the static magnetic field is not uniform due to the different magnetic susceptibility of human tissues due to the entrance of a patient, thereby causing different precession frequencies of protons in the patient. Therefore, the center frequency of the magnetic resonance system needs to be calibrated to a proper value when performing the magnetic resonance scan, so as to ensure the grease pressing effect and obtain a high-quality magnetic resonance image. Due to the chemical shift of other tissues such as fat and muscle, the precession frequency of other tissues such as fat and muscle is different under the same field intensity, and theoretically, the fat frequency is about 3.45ppm lower than that of other tissues such as muscle. Generally, the frequency spectrum line collected by a human body is generally in a lorentz line shape with two peaks, the higher frequency peak is a water (muscle, etc.) peak, and the lower frequency peak is a fat peak. However, due to the non-uniformity of the magnetic field of the magnet itself (e.g., near the edge of the magnet) and the complexity of the human tissue, the actual frequency spectrum is no longer two ideal lorentz-type peaks, and there is severe broadening, distortion, or even splitting, that makes it difficult to identify water peaks in the frequency spectrum.

The existing frequency calibration techniques are generally numerical fitting of frequency spectra. According to a theoretical model, the spectral line should satisfy a bimodal Lorentzian line type, the acquired frequency spectral line or frequency spectrum information is fitted through a function of the sum of the two Lorentzian line types, and the frequency of the water peak, namely the frequency of the system, can be obtained from parameters of a fitting result.

The method is suitable for the condition that the B0 field is relatively uniform when no obvious cavity or convex part exists in the part of the central area of the magnet, and the frequency spectral line is relatively close to a function model of the sum of two Lorentzian line types under the ideal condition. However, when scanning more complex regions of human tissue (e.g., neck, cervical and thoracic), the B0 field is less uniform due to the influence of the anatomy. At this time, because the frequency spectral line has severe broadening, deformation and even splitting, and is far away from the bimodal lorentzian function model under an ideal condition, the existing fitting method has errors or instability, inaccurate system frequency is obtained, and clinical application (such as the fat pressing effect of a fat pressing image) is affected.

Disclosure of Invention

The embodiment of the invention provides a magnetic resonance frequency calibration method, a magnetic resonance imaging device, an imaging method, a system and a storage medium, so as to improve the robustness of the central frequency of a magnetic resonance system.

In a first aspect, an embodiment of the present invention provides a magnetic resonance frequency calibration method, where the method includes:

exciting a region to be scanned by utilizing a pre-scanning radio frequency pulse, collecting a plurality of echo signals from the region to be scanned, and determining frequency spectral lines or frequency spectrum information of the echo signals;

identifying peak-to-valley information in the frequency spectral lines or spectral information, wherein the peak-to-valley information includes at least one of a number of peaks and valleys, a peak amplitude, a valley depth, a peak frequency, and a peak-to-peak spacing;

and determining the water peak frequency in the frequency spectrum line or the frequency spectrum information according to the peak-valley information based on a preset calibration mode, and determining the water peak frequency as the central frequency of the magnetic resonance system.

Further, determining the water peak frequency in the frequency spectrum line or the frequency spectrum information according to the peak-valley information based on a preset calibration mode, including:

and determining a corresponding water peak screening rule according to the preset calibration mode and the number of peaks in the peak-valley information, determining peaks meeting conditions in the frequency spectrum line or the frequency spectrum information as water peaks according to the water peak screening rule, and determining the frequency of the peaks meeting the conditions as water peak frequency.

Further, the preset calibration mode is a normal mode, wherein a corresponding water peak screening rule is determined according to the preset calibration mode and the number of peaks in the peak-valley information, and a peak satisfying a condition in the frequency spectrum line or the frequency spectrum information is determined as a water peak according to the water peak screening rule, including:

if the number of peaks in the frequency spectrum line or the frequency spectrum information is 1, determining a single peak in the frequency spectrum line or the frequency spectrum information as a water peak;

and if the number of peaks in the frequency spectrum line or the frequency spectrum information is more than or equal to 2, determining at least one water-fat peak pair in the frequency spectrum line or the frequency spectrum information, screening a first optimal water-fat peak pair according to the at least one water-fat peak pair, and determining a water peak according to the first optimal water-fat peak pair.

Further, determining at least one water-fat peak pair in the frequency spectrum line or the frequency spectrum information comprises:

if the ratio of the valley depth of the valley to the adjacent peak amplitude meets a first preset condition, determining the peak smaller than the valley frequency of the valley as a candidate fat peak, and determining the peak larger than the valley frequency of the valley as a candidate water peak;

and selecting candidate fat peaks and candidate water peaks meeting the interval condition for a first standard interval to form the water-fat peak pair, wherein the first standard interval is the standard interval of the fat peaks and the water peaks.

Further, after determining at least one water-fat peak pair in the frequency spectrum line or the frequency spectrum information, the method further includes:

screening the at least one water-fat peak pair for a first water-fat peak pair according to a first constraint;

and when the number of the first water-fat peak pairs is more than zero, screening second water-fat peak pairs in the first water-fat peak pairs according to a second limiting condition.

Further, screening a first optimal water and fat peak pair according to the at least one water and fat peak pair, and determining a water peak according to the first optimal water and fat peak pair, includes:

if the number of the first water-fat peak pairs is zero, determining that the first optimal water-fat peak pairs do not exist, and determining the peak with the maximum peak amplitude in the frequency spectrum line or the frequency spectrum information as a water peak;

if the number of the second water and fat peak pairs is zero, acquiring a first peak-to-peak distance in a first water and fat peak pair, determining a first water and fat peak pair corresponding to the first peak-to-peak distance with the minimum difference with a first standard distance between the water and fat peak and the water peak as a first optimal water and fat peak pair, and determining candidate water peaks in the first optimal water and fat peak pair as water peaks;

and if the number of the second water-fat peak pairs is larger than zero, screening the first optimal water-fat peak pair according to a left-leaning principle and an amplitude principle, and determining candidate water peaks in the first optimal water-fat peak pair as water peaks.

Further, screening the first optimal water-fat peak pair according to a left-leaning principle and an amplitude principle comprises:

determining the water-fat peak pair with the lowest frequency of the candidate water peak in the second water-fat peak pair as the first optimal water-fat peak pair;

obtaining the absolute value of the amplitude difference value of the maximum peak amplitude in the second water and fat peak pair and the peak amplitude of the candidate water peak in the first optimal water and fat peak pair;

if the absolute value of the amplitude difference is smaller than or equal to a first threshold, reserving the first optimal water-fat peak;

and if the absolute value of the amplitude difference is larger than the first threshold, updating the water-fat peak pair corresponding to the maximum peak amplitude into a first optimal water-fat peak.

Further, after the screening the first optimal water-fat peak pair according to the left-leaning rule and the peak amplitude maximization rule, the method further includes:

determining whether a standard water-fat peak pair exists in the first water-fat peak pair according to standard screening conditions;

and if so, replacing the first optimal water-fat peak pair with the standard water-fat peak pair, and determining candidate water peaks in the standard water-fat peak pair as water peaks.

Further, the method is characterized by further comprising, after determining the water peak:

determining the peak with the maximum peak amplitude in the preset frequency range of the water peak;

and if the peak with the maximum peak amplitude is different from the water peak, replacing the water peak with the maximum peak amplitude.

Further, the preset calibration mode is a special mode, wherein a corresponding water peak screening rule is determined according to the preset calibration mode and the number of peaks in the peak-valley information, and a peak satisfying a condition in the frequency spectrum line or the frequency spectrum information is determined as a water peak according to the water peak screening rule, including:

if the number of peaks in the frequency spectrum line or the frequency spectrum information is 1, determining a convex hull in the frequency spectrum line or the frequency spectrum information as a peak, and increasing the number of corresponding peaks;

if the number of peaks in the frequency spectrum line or the frequency spectrum information is more than or equal to 2, determining at least one water and fat peak pair in the frequency spectrum line or the frequency spectrum information, determining a second optimal water and fat peak pair according to a left-leaning principle, and determining a peak with the highest frequency in the second optimal water and fat peak pair as a water peak, wherein the left-leaning principle is that the water and fat peak pair with the lowest frequency is determined as the second optimal water and fat peak pair.

Further, the preset calibration mode is a silica gel mode, wherein a corresponding water peak screening rule is determined according to the preset calibration mode and the number of peaks in the peak-valley information, and a peak satisfying a condition in the frequency spectrum line or the frequency spectrum information is determined as a water peak according to the water peak screening rule, including:

if the number of peaks in the frequency spectrum line or the frequency spectrum information is 2, determining the peak types of any two peaks according to the actual distance between the two peaks and a second standard distance, and determining a water peak according to the peak types, wherein the second standard distance comprises the peak-peak standard distance between any two peaks in a silica gel peak, a fat peak and a water peak;

and if the number of peaks in the frequency spectrum line or the frequency spectrum information is more than or equal to 3, determining an optimal three-peak combination according to the second standard interval and a preset evaluation function, and determining a water peak according to the optimal three-peak combination.

Further, determining the peak type of the two peaks according to the distance between the two peaks and the peak-to-peak standard distance includes:

and obtaining the difference value between the actual distance and each standard distance, and determining the peak types of two peaks in the frequency spectrum line or the frequency spectrum information according to the standard distance corresponding to the minimum difference value.

Further, determining an optimal three-peak combination according to the standard interval and a preset evaluation function, and determining a water peak according to the optimal three-peak combination, includes:

combining any three peaks in the frequency spectral lines or the frequency spectral information to form at least one tri-peak combination;

traversing the three-peak combination to obtain an evaluation function value of the three-peak combination, wherein the evaluation function value is the sum of absolute values of differences between any peak-to-peak distance in the three-peak combination and a corresponding peak-to-peak standard distance;

and determining the three-peak combination corresponding to the minimum evaluation function value as the optimal three-peak combination, and determining the peak with the highest frequency in the optimal three-peak combination as a water peak.

In a second aspect, an embodiment of the present invention further provides a magnetic resonance imaging method, including:

exciting a region to be scanned by utilizing a pre-scanning radio frequency pulse, and collecting a plurality of echo signals from the region to be scanned;

determining frequency spectral lines or spectral information of the plurality of echo signals;

determining the water peak frequency in the frequency spectrum line or the frequency spectrum information according to the peak-valley information based on a preset calibration mode, and determining the water peak frequency as the central frequency of the magnetic resonance system;

exciting the region to be scanned by using the central frequency to acquire a magnetic resonance imaging signal;

and reconstructing the magnetic resonance imaging signal to generate a magnetic resonance image.

In a third aspect, an embodiment of the present invention further provides a magnetic resonance system, including: a magnetic resonance apparatus and a computer apparatus, wherein the computer apparatus comprises a memory, one or more processors and a computer program stored on the memory and executable on the processors, the processor when executing the program being operable to perform the method of magnetic resonance frequency calibration provided by any of the embodiments of the invention.

According to the method, the peak-valley information in the frequency spectrum line or the frequency spectrum information is identified, the characteristic information such as the number of peaks and valleys, the peak amplitude, the valley depth, the peak frequency, the peak-peak distance and the like in the peak-valley information is screened according to the preset calibration mode, the water peak frequency is used for determining the central frequency of the magnetic resonance system, the problem of large identification error rate caused by the fact that the frequency spectrum line or the frequency spectrum information of a complicated part of a human body is not standard is solved through a numerical fitting mode, different calibration modes are applied according to different scanning parts, the water peak frequency in the frequency spectrum line or the frequency spectrum information is intelligently identified, and the flexibility and the calibration precision of frequency calibration of the magnetic resonance system are improved.

Drawings

FIG. 1A is a schematic diagram of a magnetic resonance imaging apparatus;

fig. 1B is a flowchart of a magnetic resonance frequency calibration method according to an embodiment of the present invention;

fig. 2 is a flowchart of a magnetic resonance frequency calibration method according to a second embodiment of the present invention;

fig. 3A is a flowchart of a magnetic resonance frequency calibration method according to a third embodiment of the present invention;

FIG. 3B is a schematic diagram of frequency spectra obtained by scanning the thoracic vertebrae according to a third embodiment of the present invention;

FIG. 3C is a schematic diagram of frequency spectra obtained by scanning the cervical spine according to a third embodiment of the present invention;

fig. 3D is a diagram showing a magnetic resonance imaging result obtained by scanning the thoracic vertebrae according to the third embodiment of the present invention;

fig. 3E is a diagram showing a magnetic resonance imaging result obtained by scanning cervical vertebrae according to the third embodiment of the present invention;

fig. 4 is a flowchart of a magnetic resonance frequency calibration method according to a fourth embodiment of the present invention;

fig. 5 is a flowchart of a magnetic resonance imaging method according to a fifth embodiment of the present invention;

fig. 6 is a schematic structural diagram of a magnetic resonance frequency calibration apparatus according to a sixth embodiment of the present invention;

fig. 7 is a schematic structural diagram of a magnetic resonance system according to a seventh embodiment of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.

A magnetic resonance imaging system typically comprises a magnet having an aperture, a transmit coil for transmitting radio frequency signals and a receive coil for receiving magnetic resonance signals, gradient coils for spatially localizing the magnetic resonance signals, a pulse generator for generating a scan sequence, and a control system. The magnetic resonance imaging system is operated by an operator (clinician) controlling a console connected to the control system, which may include a keyboard or other input device, a control panel and a display to input commands and display the generated images.

Fig. 1A is a schematic structural view of a magnetic resonance imaging apparatus in which a clinician first places a subject 3 on a bed 1 and places a local coil for receiving magnetic resonance signals on the body surface of the subject 3 at the time of performing a magnetic resonance examination; then the clinician controls the scanning bed 1 to move towards the aperture formed by the magnet 2 by operating the console connected with the control system 5, after the magnetic resonance imaging system monitors that the clinician sends out the instruction of the movement of the scanning bed 1, the control system 5 monitors the movement range of the scanning bed 1 immediately, when the scanning bed 1 enters the edge of the scanning imaging area 4, the control system 5 controls the pulse sequence generator to generate a corresponding sequence for scanning, the sequence can control the excitation to generate the radio frequency pulse, and the radio frequency pulse can excite the body area of the examinee 3 to generate the precession nuclear spin. In the moving process of the scanning bed 1, the gradient magnetic field generated by the gradient coil can carry out phase encoding, frequency encoding or slice selection encoding on the precession nuclear spin, the receiving coil placed on the surface of the body of the detected object can move in the inner space of the magnet space along with the scanning bed 1, and the receiving coils at different positions are in an open state or a closed state under the action of the control system so as to receive corresponding magnetic resonance signals.

Example one

Fig. 1B is a flowchart of a magnetic resonance frequency calibration method according to an embodiment of the present invention, which is applicable to a case where a center frequency of a magnetic resonance system is calibrated before a magnetic resonance scan is performed on a patient, and the method can be performed by a magnetic resonance frequency calibration apparatus according to an embodiment of the present invention, and the apparatus can be implemented in a software and/or hardware manner. Referring to fig. 1B, the method specifically includes:

s110, exciting a region to be scanned by utilizing a pre-scanning radio frequency pulse, collecting a plurality of echo signals from the region to be scanned, and determining frequency spectral lines or frequency spectrum information of the echo signals.

In this embodiment, referring to FIG. 1A, the magnet 2 defines an aperture that contains a gradient coil and a radio frequency transmit coil, the gradient coil being disposed within the magnet-defined aperture and the radio frequency transmit coil also being disposed within the magnet-defined aperture. Wherein the gradient coils may comprise an X-axis gradient coil, a Y-axis gradient coil and a Z-axis gradient coil, the gradient coils being connectable to a gradient assembly comprising gradient current Amplifiers (AMP), the gradient assembly may comprise three independent channels Gx, Gy, Gz, each gradient amplifier exciting a corresponding one of the gradient coils of the gradient coil set to generate gradient fields for generating respective spatially encoded signals for spatially localizing the magnetic resonance signals. The control system 5 may generate a pre-scan sequence, which may include various parameters such as gradient amplitude, intensity, sampling time, radio frequency pulse flip angle, etc.; the pre-scan sequence can control the radio frequency transmitting coil to transmit a pre-scan pulse in the scanning imaging region 4, and control the gradient coil to generate one or more gradient pulses; the pre-scanning pulse and the gradient pulse excite the region to be scanned of the examinee 3 to trigger a nuclear spin echo signal; further, the echo signal can be detected or measured by the radio frequency receiving coil, and can be sent to the control system 5 after certain digital-to-analog conversion or amplification processing; the control system 5 processes the echo signal to obtain a frequency spectrum line or frequency spectrum information/frequency spectrum information.

The frequency spectrum line or the frequency spectrum information represents the precession frequency corresponding to different tissues, the horizontal axis of the frequency spectrum line or the frequency spectrum information is frequency, the vertical axis of the frequency spectrum line or the frequency spectrum information is amplitude, and the amplitude represents the proportion of the content of the fat or the water.

Alternatively, the frequency spectral line or spectral information may be implemented as follows: the method comprises the steps of pre-scanning a to-be-scanned part of a patient, acquiring magnetic resonance data, carrying out Fourier transform on the magnetic resonance data, and generating frequency spectral lines or frequency spectral information.

And S120, identifying peak-valley information in the frequency spectrum line or the frequency spectrum information, wherein the peak-valley information comprises at least one of the number of peaks and valleys, the amplitude of peaks, the depth of valleys, the frequency of peaks and the distance between peaks and valleys.

The frequency spectral line or the spectral information has irregular amplitude variation along with the variation of the frequency, so that peaks and valleys are formed. Optionally, if it is recognized (successively) that the amplitude has an ascending trend and a descending trend, and the absolute value of the difference between the amplitude of the ascending vertex and the amplitude of the descending vertex is greater than the peak recognition threshold, it is determined that the ascending trend and the descending trend form a peak.

The peak-valley information refers to the related information of all peaks and valleys of the frequency spectral line or the spectral information, wherein the number of the peaks and the valleys comprises the number of the peaks and the number of the valleys in the frequency spectral line or the spectral information; the peak amplitude refers to amplitude information of each peak, namely the corresponding lipid-water content ratio of each peak; the valley depth refers to depth information of each valley; peak frequency refers to the frequency corresponding to the maximum amplitude point of each peak, such as the position of a fat peak in the frequency domain or the position of a water peak in the frequency domain; peak-to-peak spacing refers to the spacing between any two peaks in a frequency spectrum line or spectral information.

And S130, determining the water peak frequency in the frequency spectrum line or the frequency spectrum information according to the peak valley information based on a preset calibration mode, and determining the water peak frequency as the central frequency of the magnetic resonance system.

Due to the characteristic of the lipid-water content ratio of different parts of a human body, the calibration modes of the magnetic resonance center frequency are different, and different calibration modes are applied when different parts of the human body are calibrated. Illustratively, the static magnetic field B is caused by less fat in the cervical or thoracic vertebrae, and the complexity and irregularity of the structure of the above-mentioned portions₀The unevenness of (a) is significantly enhanced; the fat rate of the parts such as the pelvic cavity or the knee joint of the breast and the patient with partial fat is obviously increased, the central frequency of the magnetic resonance is easily calibrated to the fat peak by using the traditional calibration method, and the accuracy of the magnetic resonance image is further reduced.

The preset calibration mode at least comprises a normal mode, a special mode and a silica gel mode, wherein the special mode can be used for carrying out frequency calibration on specific parts such as cervical vertebra, thoracic vertebra and cervical vertebra, the silica gel mode can be used for carrying out frequency calibration on a mammary gland part implanted with silica gel, and the normal mode can be used for carrying out frequency calibration on other parts except the special parts. Alternatively, the preset calibration mode may be set by a physician or technician of the magnetic resonance procedure in accordance with the region of the patient to be scanned between magnetic resonances of the patient. In the actual scanning process, the special mode or the non-special mode can be determined according to the region to be detected of the detected object. If the region to be detected of the examinee is any one of cervical vertebra, thoracic vertebra or cervical vertebra, the current scanning mode can be determined as the special mode. Further, before the scanning of the examinee, the normal mode or the silica gel mode can be selected according to the information registered by the patient. For example, the silicone mode is selected only when the region to be detected according to the subject is the chest and it is displayed in the registered information of the patient that the mammary gland part is implanted with silicone. When the region to be detected according to the subject is the chest and it is shown in the registered information of the patient that no silica gel is implanted in the breast part, the normal mode is selected. When the area to be detected of the detected object is the abdomen, the legs, the head and other areas without the vertebral body and the chest, the normal mode is selected.

In this embodiment, different preset calibration modes are applied to different human body parts, and feature information such as the number of peaks and valleys, the peak amplitude, the valley depth, the peak frequency, the peak-to-peak distance, and the like in the frequency spectrum line or the frequency spectrum information of each part is analyzed corresponding to different screening rules, so as to screen and determine the water peak frequency in the frequency spectrum line or the frequency spectrum information, thereby avoiding the problem that the frequency spectrum line or the frequency spectrum information of different parts causes a large error of the determined water peak frequency according to a unified screening rule.

Optionally, step S130 includes: and determining a corresponding water peak screening rule according to a preset calibration mode and the number of peaks in the peak-valley information, determining peaks meeting conditions in the frequency spectrum line or the frequency spectrum information as water peaks according to the water peak screening rule, and determining the frequencies of the peaks meeting the conditions as water peak frequencies.

In this embodiment, in the same calibration mode, the number of peaks in the frequency spectrum line or the frequency spectrum information is identified, the number of peaks is different and corresponds to different water peak screening rules, wherein the water peak screening rules include water peak screening conditions, a peak meeting the screening conditions in the water peak screening rules is determined to be a water peak in at least one peak in the frequency spectrum line or the frequency spectrum information, and the frequency of the water peak is further determined to be the center frequency of the magnetic resonance system. The center frequency of the magnetic resonance in this embodiment may also be referred to as the chemical saturation transmit frequency by which water or fat, etc. may be saturated.

According to the technical scheme of the embodiment, the peak-valley information in the frequency spectrum line or the frequency spectrum information is identified, the water peaks in the frequency spectrum line or the frequency spectrum information are screened according to the preset calibration mode and the characteristic information such as the number of peaks and valleys, the peak amplitude, the valley depth, the peak frequency, the peak-peak distance and the like in the peak-valley information, the water peak frequency is used for determining the central frequency of the magnetic resonance system, the problem of large identification error rate caused by the fact that the frequency spectrum line or the frequency spectrum information of a complicated part of a human body is not standard is solved through a numerical fitting mode, different calibration modes are applied according to different scanning parts, the water peak frequency in the frequency spectrum line or the frequency spectrum information is intelligently identified, and the flexibility and the calibration accuracy of the frequency calibration of the magnetic.

Example two

Fig. 2 is a flowchart of a magnetic resonance frequency calibration method according to a second embodiment of the present invention, and based on the first embodiment, a magnetic resonance frequency calibration method when the preset calibration mode is the normal mode is provided. Correspondingly, the method specifically comprises the following steps:

s210, exciting a region to be scanned by utilizing a pre-scanning radio frequency pulse, collecting a plurality of echo signals from the region to be scanned, determining frequency spectral lines or frequency spectral information of the echo signals, and identifying peak-valley information in the frequency spectral lines or the frequency spectral information.

Wherein the peak-to-valley information includes at least one of a number of peaks and valleys, a peak amplitude, a valley depth, a peak frequency, and a peak-to-peak distance.

And S220, if the number of peaks in the frequency spectrum line or the frequency spectrum information is 1, determining a single peak in the frequency spectrum line or the frequency spectrum information as a water peak.

In this embodiment, if the number of peaks in the frequency spectrum line or the frequency spectrum information is 1, it indicates that there is only one single peak in the frequency spectrum line or the frequency spectrum information, and the single peak is determined as a water peak because a water peak signal is always present when a human body is scanned.

And S230, if the number of peaks in the frequency spectrum line or the frequency spectrum information is more than or equal to 2, determining at least one water-fat peak pair in the frequency spectrum line or the frequency spectrum information, screening a first optimal water-fat peak pair according to the at least one water-fat peak pair, and determining a water peak according to the first optimal water-fat peak pair.

Wherein, the number of peaks in the frequency spectrum line or the frequency spectrum information is more than or equal to 2, at least one water-fat peak pair is formed according to multiple peaks, and the water-fat peak pair consists of a fat peak and a water peak. The first optimal water and fat peak pair refers to a standard water and fat peak pair or a water and fat peak pair most similar to the standard water and fat peak pair in at least one water and fat peak pair, and a candidate water and fat peak in the first optimal water and fat peak pair is determined as a water and fat peak.

Optionally, determining at least one water-fat peak pair in the frequency spectrum line or the frequency spectrum information includes: if the ratio of the valley depth of the valley to the adjacent peak amplitude meets a first preset condition, determining the peak smaller than the valley frequency of the valley as a candidate fat peak, and determining the peak larger than the valley frequency of the valley as a candidate water peak; and selecting candidate fat peaks and candidate water peaks meeting the interval condition to form a water-fat peak pair for the first standard interval, wherein the first standard interval is the first standard interval of the fat peaks and the water peaks.

For example, the first preset condition may be that when the valley depth is greater than or equal to 1/3 of the amplitude of the adjacent peak, the valley corresponding to the valley depth is determined as the boundary between the fat peak and the water peak. Wherein, the chemical bond of hydrogen atom in water molecule is O-H bond, the chemical bond of hydrogen proton in fat molecule is C-H bond, the electron cloud distribution around the hydrogen proton is different in the two structures, the magnetic field intensity of the hydrogen proton in water molecule is slightly higher, the difference of progress frequency of the proton in water molecule and fat molecule is about 3.5PPM (for the magnetic resonance system with the magnetic field intensity of 1.5T, the difference of water-fat frequency is about 220Hz), the frequency of fat peak is less than the frequency of water peak, thereby the peak less than the dividing line frequency is determined as candidate fat peak, and the peak more than the dividing line frequency is determined as candidate water peak.

And selecting corresponding candidate water peaks for each candidate fat peak to form a water-fat peak pair, and optionally forming the water-fat peak pair according to a spacing principle. The first standard pitch of the fat peak and the water peak was found to be 3.45ppm from the physical properties of the fat peak and the water peak, and the candidate water peak having the closest first standard pitch to the candidate fat peak was selected to form a water-fat peak pair. Illustratively, if for a candidate fat peak, there is a first candidate water peak spaced from the candidate fat peak by 3.2ppm, differing from the first standard spacing by 0.25ppm, and a second candidate water peak spaced from the candidate fat peak by 3.5ppm, differing from the first standard spacing by 0.05ppm, then it is determined that the second candidate water peak forms a water-fat peak pair with the candidate fat peak.

Optionally, after the water and fat peak pair is determined according to the distance principle, the water and fat peak pair is corrected according to the maximum amplitude principle, and the water and fat peak pair is updated. Comparing the amplitude of the candidate water peak in the formed water and fat peak pair with that of the adjacent candidate water peak, and replacing the candidate water peak with the adjacent candidate water peak to form a new water and fat peak pair if the amplitude of the adjacent candidate water peak is greater than that of the candidate water peak; and if the amplitude of the adjacent candidate water peak is less than or equal to the candidate water peak, keeping the original water-fat peak pair unchanged.

Optionally, after determining at least one water-fat peak pair in the frequency spectrum line or the frequency spectrum information, the method further includes: and screening the first water-fat peak pair in at least one water-fat peak pair according to a first limiting condition.

In this embodiment, since the water and fat peak pair formed according to the pitch principle and/or the amplitude maximization principle has an error with the standard water and fat peak pair, the first water and fat peak pair may be screened by the first constraint condition, where the first constraint condition may include a first error range and/or a first amplitude threshold, that is, the first error range is satisfied by screening the error that satisfies the pitch between the peaks and the first standard pitch, and/or the water and fat peak pair whose amplitude of the candidate water and fat peak is greater than the first amplitude threshold is the first water and fat peak pair.

And if the first water and fat peak pair is empty, namely the water and fat peak pair meeting the first limiting condition does not exist, determining that the first optimal water and fat peak pair does not exist, and determining the peak with the maximum peak amplitude in the frequency spectrum line or the frequency spectrum information as the water peak.

And if the number of the first water-fat peak pairs is not zero, namely the water-fat peak pairs meeting the first limiting condition exist, screening second water-fat peak pairs in the first water-fat peak pairs according to a second limiting condition. Wherein the second limiting condition may be that a second error range and/or a second amplitude threshold value is included, that is, the error of the peak-to-peak distance from the first standard distance is screened to satisfy the second error range, and/or the first water-fat peak pair whose candidate water peak amplitude is greater than the second amplitude threshold value is screened as the second water-fat peak pair. It should be noted that the second error range is included in the first error range, and/or the second amplitude threshold is larger than the first amplitude threshold, i.e. the second limitation is stricter than the first limitation.

If the number of the second water and fat peak pairs is zero, that is, there is no first water and fat peak pair satisfying the second limiting condition, obtaining a first peak-to-peak distance in the first water and fat peak pair, determining the first water and fat peak pair corresponding to the first peak-to-peak distance with the minimum difference between the first standard distances of the water and fat peaks and the water peak as a first optimal water and fat peak pair, and determining candidate water peaks in the first optimal water and fat peak pair as water peaks.

And if the number of the second water-fat peak pairs is larger than zero, screening the first optimal water-fat peak pair according to a left-leaning principle and an amplitude principle, and determining candidate water peaks in the first optimal water-fat peak pair as water peaks. And determining the water-fat peak pair with the lowest frequency of the candidate water peak in the second water-fat peak pair as the first optimal water-fat peak pair. The amplitude principle refers to obtaining the absolute value of the amplitude difference value of the maximum peak amplitude in the second water and fat peak pair and the peak amplitude of the candidate water peak in the first optimal water and fat peak pair; if the absolute value of the amplitude difference is less than or equal to a first threshold, the first optimal water-fat peak is reserved; and if the absolute value of the amplitude difference is larger than the first threshold, updating the second water-fat peak pair corresponding to the maximum peak amplitude into the first optimal water-fat peak.

Optionally, after the first optimal water-fat peak pair is screened according to the left-leaning principle and the amplitude principle, the method further includes: determining whether a standard water-fat peak pair exists in the first water-fat peak pair according to standard screening conditions; and if so, replacing the first optimal water-fat peak pair by the standard water-fat peak pair, and determining candidate water peaks in the standard water-fat peak pair as water peaks.

In this embodiment, the standard screening condition refers to a condition satisfied by a standard water and fat peak pair, and may exemplarily include a standard amplitude threshold, a standard peak-to-peak distance, a standard water peak frequency, and a standard fat peak frequency. In this embodiment, the standard water and fat peak pair is screened, and the first optimal water and fat peak pair is replaced with the standard water and fat peak pair, so that the accuracy of determining the water peak is improved.

Optionally, after determining the water peak, the method further comprises: determining the peak with the maximum peak amplitude in the preset frequency range of the water peak; and if the peak with the maximum peak amplitude is different from the water peak, replacing the water peak with the maximum peak amplitude.

In this embodiment, the preset frequency range may be, for example, a range of ± 50Hz of the current water peak. The maximum peak is screened in the preset frequency range, the problem that the water peak is determined inaccurately due to the fact that the water peak is not standard and the current water peak is split or burred is solved, the current water peak is replaced by the peak with the maximum peak amplitude, and the water peak determination accuracy is improved.

And S240, determining the frequency of the water peak as the central frequency of the magnetic resonance system.

The central frequency of the magnetic resonance system in this embodiment corresponds to the frequency at which the water signal starts to be saturated, i.e. the frequency corresponding to the water peak.

According to the technical scheme of the embodiment, a single peak in the frequency spectrum line or the frequency spectrum information is determined as a water peak or a first optimal water and fat peak pair closest to a standard water and fat peak pair is screened in at least one water and fat peak pair in the normal mode, and a candidate water peak in the first optimal water and fat peak pair is determined as the water peak, so that the problem of low water peak determination precision when a plurality of peaks exist due to nonstandard frequency spectrum line or frequency spectrum information is solved, the water peak meeting the conditions is intelligently screened according to the peak-valley information, and the precision of the center frequency of the magnetic resonance system is improved.

EXAMPLE III

Fig. 3A is a flowchart of a magnetic resonance frequency calibration method according to a third embodiment of the present invention, and on the basis of the third embodiment, a magnetic resonance frequency calibration method in which a preset calibration mode is a special mode is further provided. Correspondingly, the method specifically comprises the following steps:

s310, exciting a region to be scanned by utilizing a pre-scanning radio frequency pulse, collecting a plurality of echo signals from the region to be scanned, determining frequency spectral lines or frequency spectral information of the echo signals, and identifying peak-valley information in the frequency spectral lines or the frequency spectral information.

And S320, if the number of peaks in the frequency spectral line or the frequency spectral information is 1, determining convex hulls in the frequency spectral line or the frequency spectral information as peaks, and increasing the number of corresponding peaks.

In this embodiment, because the fat content in the cervical vertebra, the thoracic vertebra, the neck and other parts is low, no obvious fat peak exists, and the complexity and irregularity of the anatomical structure of the neck are the phenomenon that the magnetic field is not uniform, a phenomenon that water signals are scattered on a plurality of obvious peaks often exists in the final frequency spectrum space, and the frequency spectrum lines or frequency spectrum information of these parts is easily recognized as the frequency spectrum lines or frequency spectrum information of a single peak in the normal mode, so that the frequency of the water peak is determined to be too high.

During frequency calibration of a special mode, if a single-peak frequency spectrum line or spectrum information is identified, a peak identification threshold value and a valley identification threshold value are reduced, a convex hull meeting the peak identification threshold value in the frequency spectrum line or spectrum information is determined as a peak, the number of corresponding peaks is increased, and identification errors caused by the fact that the amplitude of a fat peak is too small are avoided.

S330, if the number of peaks in the frequency spectrum line or the frequency spectrum information is more than or equal to 2, determining at least one water-fat peak pair in the frequency spectrum line or the frequency spectrum information, determining a second optimal water-fat peak pair according to a left-leaning principle, and determining a peak with the highest frequency in the second optimal water-fat peak pair as a water peak.

Wherein, the left inclination principle is to determine the water-fat peak pair with the lowest frequency as a second optimal water-fat peak pair.

In this embodiment, the boundary between the fat peak and the water peak is determined according to the ratio of the valley depth to the amplitude of the connected peak, and the candidate fat peak and the candidate water peak are further determined. And forming the water-fat peak pair according to the spacing principle, and updating the water-fat peak pair according to the left-leaning principle. Illustratively, if for a candidate fat peak, there is a first candidate water peak with a distance of 3.2ppm from the candidate fat peak and a difference of 0.25ppm from the first standard distance, and a second candidate water peak with a distance of 3.5ppm from the candidate fat peak and a difference of 0.05ppm from the first standard distance, then the second candidate water peak and the candidate fat peak form a water-fat peak pair according to the distance principle, and further, the first candidate water peak replaces the second candidate water peak according to the left-leaning principle, and the water-fat peak pair is updated. In the embodiment, a left-leaning principle is introduced in a special mode, so that the frequency of candidate water peaks in the water and fat peak pair is avoided being too high.

Optionally, after determining the water-fat peak pair according to the pitch principle, a third water-fat peak pair is screened from the at least one water-fat peak pair according to a third constraint. Wherein the third constraint may be the same as or different from the first constraint, and is used to screen a third water-fat peak pair satisfying a third error range and/or a third amplitude threshold. And when the third water-fat peak pair is empty, determining the peak with the maximum peak amplitude in the frequency spectral line or the frequency spectral information as the water peak. And when the third water and fat peak pair is not empty, namely the third water and fat peak pair exists, screening a fourth water and fat peak pair from at least one third water and fat peak according to a fourth limiting condition. And if the fourth water and fat peak pair is empty, acquiring a second peak-to-peak distance in a third water and fat peak pair, determining the third water and fat peak pair corresponding to the second peak-to-peak distance with the minimum difference with the first standard distance between the water and fat peak and the water peak as a second optimal water and fat peak pair, and determining candidate water peaks in the second optimal water and fat peak pair as water peaks. And if the number of the fourth water and fat peak pairs is larger than zero, screening a second optimal water and fat peak pair in the fourth water and fat peak pairs according to a left-leaning principle.

Illustratively, referring to fig. 3B, fig. 3B is a schematic diagram of frequency spectrum lines obtained by scanning the thoracic vertebrae according to the third embodiment of the present invention. The water peak in fig. 3B produces a classification phenomenon, and the fat peak amplitude is lower. Two water and fat peak pairs exist in the thoracic frequency spectral line, and in a special mode, a low-frequency candidate water peak is determined as a water peak according to a left-leaning principle, wherein a peak 301 in fig. 3B is a fat peak determined by the frequency calibration mode of the application; peak 303 is the water peak determined by the frequency calibration method of the present application; peak 302 is the fat peak determined according to conventional frequency calibration; peak 304 is a water peak determined according to conventional frequency calibration means.

Referring to fig. 3C, fig. 3C is a schematic diagram of frequency spectrum lines obtained by scanning cervical vertebrae according to a third embodiment of the present invention, wherein the horizontal axis represents frequency, the vertical axis represents peak intensity, the solid line represents the calibration result of the present application, and the dotted line represents the result of the prior art, wherein the right solid line represents the water peak position, and the left solid line represents the fat peak position.

And S340, determining the frequency of the water peak as the central frequency of the magnetic resonance system.

Furthermore, the central frequency is used to excite the scanning part corresponding to the special mode, so as to acquire the magnetic resonance signal of the scanning part, and the magnetic resonance image of the scanning part can be acquired by performing Fourier transform on the magnetic resonance signal.

Fig. 3D is a diagram showing a magnetic resonance imaging result obtained by scanning the thoracic vertebrae according to the third embodiment of the present invention. Wherein, the left image is a magnetic resonance image obtained by scanning thoracic vertebra fat pressing by using the frequency corresponding to the water peak obtained by adopting the traditional frequency calibration mode as the central frequency as shown in fig. 3B, and the frame area in the image has obvious muscle and vertebral body black pressing phenomenon (the adopted central frequency is too high); the right image is a magnetic resonance image obtained by scanning thoracic vertebra fat pressing by taking the frequency corresponding to the water peak obtained by the frequency calibration mode as the center frequency in fig. 3B, and compared with the prior art, the magnetic resonance image obviously reduces the phenomenon of muscle and vertebral body blackening and improves the signal-to-noise ratio and the image contrast.

Fig. 3E is a diagram showing a magnetic resonance imaging result obtained by scanning cervical vertebrae according to the third embodiment of the present invention. Wherein, the left image is a magnetic resonance image obtained by scanning cervical vertebra pressure fat by using the frequency corresponding to the water peak obtained by adopting the traditional frequency calibration mode as the central frequency as shown in fig. 3C, and the left image obviously has the phenomenon of vertebral body pressure blackening due to the adopted central frequency is too high; the right image is a magnetic resonance image obtained by scanning cervical vertebra fat pressing by using the frequency corresponding to the water peak obtained by the frequency calibration mode of the application as the center frequency in fig. 3C, and the obtained cervical magnetic resonance image is clear in carotid artery, cervical vertebra, muscle and the like and clear in boundary.

According to the technical scheme, the second optimal water-fat peak pair closest to the standard water-fat peak pair is screened by at least one water-fat peak pair in the frequency spectral lines according to a left-leaning principle in a special mode, and the candidate water peak in the second optimal water-fat peak pair is determined as the water peak, so that the problem that when the magnetic resonance frequency of a part with low fat content is calibrated, the peak identification error is large due to too low fat peak amplitude is solved, the low-frequency water peak is screened according to the left-leaning principle, the precision of the central frequency of a magnetic resonance system of the special part of a human body is improved, and the flexibility of frequency calibration of the magnetic resonance system is improved.

Example four

Fig. 4 is a flowchart of a magnetic resonance frequency calibration method according to a fourth embodiment of the present invention, and based on the foregoing embodiment, a magnetic resonance frequency calibration method in which a preset calibration mode is a silica gel mode is further provided. Correspondingly, the method specifically comprises the following steps:

s410, exciting a region to be scanned by utilizing a pre-scanning radio frequency pulse, collecting a plurality of echo signals from the region to be scanned, determining frequency spectral lines or frequency spectral information of the echo signals, and identifying peak-valley information in the frequency spectral lines or the frequency spectral information.

And S420, if the number of peaks in the frequency spectrum line or the frequency spectrum information is 1, determining a single peak in the frequency spectrum line or the frequency spectrum information as a water peak.

And S430, if the number of peaks in the frequency spectrum line or the frequency spectrum information is 2, determining the peak types of two peaks according to the actual distance between any two peaks and the second standard distance, and determining the water peak according to the peak types.

Wherein the second standard interval comprises the peak-to-peak standard interval of any two of the silica gel peak, the fat peak and the water peak.

When the mammary gland part with the silica gel is scanned by magnetic resonance, three types of peaks including a silica gel peak, a fat peak and a water peak may exist in obtained frequency spectral line or frequency spectral information, and the frequencies of the three types of peaks are increased in sequence according to the physical characteristics of the silica gel peak, the fat peak and the water peak.

If the number of peaks in the frequency spectrum line or the spectrum information is 2, the peak types of two peaks in the frequency spectrum line or the spectrum information cannot be determined. Optionally, determining the peak type of the two peaks according to the distance between the two peaks and the standard distance includes: and obtaining the difference value between the actual distance and the standard distance of each peak and the peak, and determining the peak types of two peaks in the frequency spectrum line or the frequency spectrum information according to the standard distance of the peak and the peak corresponding to the minimum difference value. Illustratively, if the difference between the distance between two peaks in the frequency spectrum line or spectrum information and the standard distance between a silica gel peak and a fat peak is 0.7ppm, the difference between the distance between two peaks in the frequency spectrum line or spectrum information and the standard distance between a fat peak and a water peak is 1.8ppm, and the difference between two peaks in the frequency spectrum line or spectrum information and the standard distance between a silica gel peak and a water peak is 3ppm, the two peaks in the frequency spectrum line or spectrum information are determined to be a silica gel peak and a fat peak in sequence.

If a water peak exists in the two peaks in the frequency spectrum line or the frequency spectrum information, determining the peak as a final water peak; and if the two peaks in the frequency spectrum line or the frequency spectrum information are the silica gel peak and the fat peak, determining the position corresponding to the sum of the fat peak frequency and the standard interval as the position of the water peak according to the standard interval of the fat peak and the water peak, and further determining that the water peak exists at the position of the water peak.

And S440, if the number of peaks in the frequency spectrum line or the frequency spectrum information is more than or equal to 3, determining an optimal three-peak combination according to the second standard interval and a preset evaluation function, and determining a water peak according to the optimal three-peak combination.

In this embodiment, the number of peaks in the frequency spectrum line or the frequency spectrum information is greater than or equal to 3, and at least one three-peak combination exists in the frequency spectrum line or the frequency spectrum information. Illustratively, if the number of peaks in the frequency spectrum line or spectrum information is equal to 3, there is one three-peak combination, and if the number of peaks is equal to 4, there are 3 three-peak combinations.

Optionally, combining any three peaks in the frequency spectrum line or the frequency spectrum information to form at least one three-peak combination; traversing the three-peak combination to obtain an evaluation function value of the three-peak combination, wherein the evaluation function value is the sum of absolute values of differences between any peak-to-peak distance in the three-peak combination and a corresponding peak-to-peak standard distance; and determining the three-peak combination corresponding to the minimum evaluation function value as the optimal three-peak combination, and determining the peak with the highest frequency in the optimal three-peak combination as the water peak.

In this embodiment, the minimum evaluation function value is zero, and if the minimum evaluation function value is zero, the three-peak combination is the standard three-peak combination, and the peak with the highest frequency in the standard three-peak combination is determined as the water peak.

And S450, determining the frequency of the water peak as the central frequency of the magnetic resonance system.

According to the technical scheme of the embodiment, the peak types in the frequency spectrum line or the frequency spectrum information are identified in the form of the double-peak combination and the triple-peak combination under the silica gel mode, and the water peak in the frequency spectrum line or the frequency spectrum information is further identified, so that the condition that the silica gel peak is mistakenly identified as the fat peak or the water peak is avoided, the problem that the frequency calibration fails due to the existence of silica gel in the mammary gland part is solved, and the accurate frequency calibration of the mammary gland part with the silica gel is realized.

EXAMPLE five

Fig. 5 is a flowchart of a magnetic resonance imaging method according to a fifth embodiment of the present invention, which can be performed by a magnetic resonance system according to a fifth embodiment of the present invention, and the magnetic resonance system can be implemented in software and/or hardware. The method specifically comprises the following steps:

and S510, exciting a region to be scanned by utilizing a pre-scanning radio frequency pulse, and collecting a plurality of echo signals from the region to be scanned.

The center frequency is determined according to the magnetic resonance frequency calibration method provided by any one of the first embodiment to the fourth embodiment of the invention.

S520, determining frequency spectrum lines or spectrum information of a plurality of echo signals.

S530, identifying peak-valley information in the frequency spectrum line or the frequency spectrum information, wherein the peak-valley information comprises at least one of the number of peaks and valleys, the peak amplitude, the valley depth, the peak frequency and the peak-peak distance.

And S540, determining the water peak frequency in the frequency spectrum line or the frequency spectrum information according to the peak valley information based on a preset calibration mode, and determining the water peak frequency as the central frequency of the magnetic resonance system.

And S550, exciting the region to be scanned by using the central frequency, and acquiring a magnetic resonance imaging signal.

And S560, reconstructing the magnetic resonance imaging signal to generate a magnetic resonance image.

The technical scheme of the embodiment of the invention determines the calibration mode of frequency calibration through different areas to be scanned, identifies the peak-valley information in the frequency spectrum line or the frequency spectrum information under different calibration modes, the characteristic information of peak-valley quantity, peak amplitude, valley depth, peak frequency, peak-peak distance and the like in the peak-valley information is screened for the water peak in the frequency spectrum line or the frequency spectrum information, the water peak frequency is used for determining the central frequency of the magnetic resonance system, the problem of large recognition error rate caused by the nonstandard frequency spectrum line or frequency spectrum information of complicated parts of a human body is solved by a numerical fitting mode, different calibration modes are applied according to different scanning parts, and the water peak frequency in the frequency spectrum line or the frequency spectrum information is intelligently identified, so that the flexibility and the calibration precision of the frequency calibration of the magnetic resonance system are improved, and the precision of the magnetic resonance image is further improved.

EXAMPLE six

Fig. 6 is a schematic structural diagram of a magnetic resonance frequency calibration apparatus according to a sixth embodiment of the present invention, where the apparatus specifically includes:

the frequency spectrum acquisition module 610 is configured to excite a region to be scanned by using a pre-scanning radio frequency pulse, acquire a plurality of echo signals from the region to be scanned, and determine frequency spectral lines or frequency spectrum information of the echo signals;

a frequency identification module 620, configured to identify peak-valley information in the frequency spectrum line or the frequency spectrum information, where the peak-valley information includes at least one of a number of peaks and valleys, a peak amplitude, a valley depth, a peak frequency, and a peak-peak distance;

and the frequency calibration module 630 is configured to determine a water peak frequency in the frequency spectrum line or the frequency spectrum information according to the peak-valley information based on a preset calibration mode, and determine the water peak frequency as the center frequency of the magnetic resonance system.

Optionally, the frequency calibration module 630 is specifically configured to:

and determining a corresponding water peak screening rule according to a preset calibration mode and the number of peaks in the peak-valley information, determining peaks meeting conditions in the frequency spectrum line or the frequency spectrum information as water peaks according to the water peak screening rule, and determining the frequencies of the peaks meeting the conditions as water peak frequencies.

Optionally, the preset calibration mode is a normal mode, wherein the frequency calibration module 630 includes:

the first water peak determining module is used for determining a single peak in the frequency spectral line or the frequency spectrum information as a water peak if the number of peaks in the frequency spectral line or the frequency spectrum information is 1;

and the second water peak determining unit is used for determining at least one water-fat peak pair in the frequency spectral line or the frequency spectrum information if the number of peaks in the frequency spectral line or the frequency spectrum information is more than or equal to 2, screening a first optimal water-fat peak pair according to the at least one water-fat peak pair, and determining a water peak according to the first optimal water-fat peak pair.

Optionally, the second water peak determining unit includes:

the peak classification unit is used for determining a peak with a valley frequency smaller than the valley as a candidate fat peak and determining a peak with a valley frequency larger than the valley as a candidate water peak if the ratio of the valley depth of the valley to the adjacent peak amplitude meets a first preset condition;

and the water and fat peak pair determining unit is used for selecting candidate fat peaks and candidate water peaks meeting the distance condition to form a water and fat peak pair for a first standard distance, wherein the first standard distance is the standard distance between the fat peaks and the water peaks.

Optionally, the apparatus further comprises:

the first water and fat peak pair screening module is used for screening a first water and fat peak pair in at least one water and fat peak pair according to a first limiting condition after determining at least one water and fat peak pair in frequency spectral line or frequency spectral information;

and the second water and fat peak pair screening module is used for screening the second water and fat peak pair in the first water and fat peak pair according to a second limiting condition when the number of the first water and fat peak pair is more than zero.

Optionally, the second water peak determining unit includes:

the first water peak determining unit is used for determining that the first optimal water-fat peak pair does not exist if the number of the first water-fat peak pairs is zero, and determining the peak with the maximum peak amplitude in the frequency spectrum line or the frequency spectrum information as the water peak;

a second water peak determining unit, configured to, if the number of the second water and fat peak pairs is zero, obtain a first peak-to-peak distance in the first water and fat peak pair, determine, as a first optimal water and fat peak pair, a first water and fat peak pair corresponding to the first peak-to-peak distance having the smallest difference between the standard distances of the water and fat peaks and the water peak, and determine, as a water peak, a candidate water peak in the first optimal water and fat peak pair;

and the third water peak determining unit is used for screening the first optimal water and fat peak pair according to a left-leaning principle and an amplitude principle and determining candidate water peaks in the first optimal water and fat peak pair as water peaks if the number of the second water and fat peak pairs is larger than zero.

Optionally, the third water peak determining unit is specifically configured to:

determining the water-fat peak pair with the lowest frequency of the candidate water peaks in the second water-fat peak pair as a first optimal water-fat peak pair; obtaining the absolute value of the amplitude difference value of the maximum peak amplitude in the second water and fat peak pair and the peak amplitude of the candidate water peak in the first optimal water and fat peak pair; if the absolute value of the amplitude difference is smaller than or equal to a first threshold, a first optimal water-fat peak is reserved; and if the absolute value of the amplitude difference is larger than the first threshold, updating the water-fat peak pair corresponding to the maximum peak amplitude into a first optimal water-fat peak.

Optionally, the second water peak determining unit further includes:

the standard water and fat peak pair screening unit is used for determining whether a standard water and fat peak pair exists in the first water and fat peak pair or not according to standard screening conditions after screening the first optimal water and fat peak pair according to a left-leaning principle and a peak amplitude maximum principle;

and the water peak updating unit is used for replacing the first optimal water and fat peak pair with the standard water and fat peak pair and determining the candidate water peak in the standard water and fat peak pair as the water peak if the standard water and fat peak pair exists.

Optionally, the preset calibration mode is a special mode, wherein the frequency calibration module 630 includes:

a peak number updating unit, configured to determine a convex hull in the frequency spectrum line or the frequency spectrum information as a peak and increase the number of corresponding peaks if the number of peaks in the frequency spectrum line or the frequency spectrum information is 1;

and the fourth water peak determining unit is used for determining at least one water and fat peak pair in the frequency spectral line or the frequency spectral information if the number of peaks in the frequency spectral line or the frequency spectral information is more than or equal to 2, determining a second optimal water and fat peak pair according to a left-leaning principle, and determining a peak with the highest frequency in the second optimal water and fat peak pair as the water peak, wherein the left-leaning principle is that the water and fat peak pair with the lowest frequency is determined as the second optimal water and fat peak pair.

Optionally, the preset calibration mode is a silica gel mode, wherein the frequency calibration module 630 includes:

a fifth water peak determining unit, configured to determine a single peak in the frequency spectrum line or the frequency spectrum information as a water peak if the number of peaks in the frequency spectrum line or the frequency spectrum information is 1;

a sixth water peak determining unit, configured to determine, if the number of peaks in the frequency spectrum or the frequency spectrum information is 2, a peak type of two peaks according to an actual distance between any two peaks and a second standard distance, and determine a water peak according to the peak type, where the second standard distance includes a peak-to-peak standard distance between any two peaks among a silica gel peak, a fat peak, and a water peak;

and the seventh water peak determining unit is used for determining the optimal three-peak combination according to the second standard interval and the preset evaluation function and determining the water peak according to the optimal three-peak combination if the number of peaks in the frequency spectral line or the frequency spectrum information is more than or equal to 3.

Optionally, the sixth water peak determining unit is specifically configured to:

and obtaining the difference value between the actual distance and the standard distance of each peak and the peak, and determining the peak types of two peaks in the frequency spectrum line or the frequency spectrum information according to the standard distance of the peak and the peak corresponding to the minimum difference value.

Optionally, the seventh water peak determining unit includes:

the three-peak combination determining subunit is used for combining any three peaks in the frequency spectrum line or the frequency spectrum information to form at least one three-peak combination;

the evaluation function value determining subunit is used for traversing the three-peak combination to obtain an evaluation function value of the three-peak combination, wherein the evaluation function value is the sum of absolute values of differences between any peak-to-peak distance in the three-peak combination and the corresponding peak-to-peak standard distance;

and the water peak determining subunit is used for determining the three-peak combination corresponding to the minimum evaluation function value as the optimal three-peak combination and determining the peak with the highest frequency in the optimal three-peak combination as the water peak.

Optionally, the apparatus further comprises:

the amplitude detection module is used for determining the peak with the maximum peak amplitude in the preset frequency range of the water peak after the water peak is determined;

and the water peak updating module is used for replacing the water peak with the maximum peak amplitude if the peak with the maximum peak amplitude is different from the water peak.

The magnetic resonance frequency calibration device provided by the embodiment of the invention can execute the magnetic resonance frequency calibration method provided by any embodiment of the invention, and has corresponding functional modules and beneficial effects for executing the magnetic resonance frequency calibration method.

EXAMPLE seven

Fig. 7 is a schematic structural diagram of a magnetic resonance system according to a seventh embodiment of the present invention, and fig. 7 is a block diagram of an exemplary medical imaging system suitable for implementing the embodiment of the present invention, and the medical imaging system shown in fig. 7 is only an example and should not bring any limitation to the function and the scope of the embodiment of the present invention.

The magnetic resonance system comprises a magnetic resonance apparatus 500 and a computer 600.

Computer 600 may be used to implement particular methods and apparatus disclosed in some embodiments of the invention. The specific apparatus in this embodiment is illustrated by a functional block diagram of a hardware platform that includes a display module. In some embodiments, the computer 600 may implement implementations of some embodiments of the invention by its hardware devices, software programs, firmware, and combinations thereof. In some embodiments, the computer 600 may be a general purpose computer, or a specific purpose computer.

As shown in FIG. 7, computer 600 may include an internal communication bus 601, a processor 602, a Read Only Memory (ROM)603, a Random Access Memory (RAM)604, a communication port 605, input/output components 606, a hard disk 607, and a user interface 608. The internal communication bus 601 may enable data communication among the components of the computer 600. Processor 602 may make the determination and issue a prompt. In some embodiments, the processor 602 may be comprised of one or more processors. The communication port 605 may enable the computer 600 to communicate with other components (not shown), such as: and the external equipment, the image acquisition equipment, the database, the external storage, the image processing workstation and the like are in data communication. In some embodiments, computer 600 may send and receive information and data from a network through communication port 605. Input/output component 606 supports the flow of input/output data between computer 600 and other components. The user interface 608 may enable interaction and information exchange between the computer 600 and a user. The computer 600 may also include various forms of program storage units and data storage units such as a hard disk 607, a Read Only Memory (ROM)603, a Random Access Memory (RAM)604, various data files capable of being stored for processing and/or communication by the computer, and possibly program instructions for execution by the processor 602.

The processor when executing a program is operable to perform a method of magnetic resonance frequency calibration, the method comprising:

Although the present invention has been described with reference to the preferred embodiments, it is not intended to limit the present invention, and those skilled in the art can make variations and modifications of the present invention without departing from the spirit and scope of the present invention by using the methods and technical contents disclosed above.

Also, this application uses specific language to describe embodiments of the application. Reference throughout this specification to "one embodiment," "an embodiment," and/or "some embodiments" means that a particular feature, structure, or characteristic described in connection with at least one embodiment of the present application is included in at least one embodiment of the present application. Therefore, it is emphasized and should be appreciated that two or more references to "an embodiment" or "one embodiment" or "an alternative embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, some features, structures, or characteristics of one or more embodiments of the present application may be combined as appropriate.

Moreover, those skilled in the art will appreciate that aspects of the present application may be illustrated and described in terms of several patentable species or situations, including any new and useful combination of processes, machines, manufacture, or materials, or any new and useful improvement thereon. Accordingly, various aspects of the present application may be embodied entirely in hardware, entirely in software (including firmware, resident software, micro-code, etc.) or in a combination of hardware and software. The above hardware or software may be referred to as "data block," module, "" submodule, "" engine, "" unit, "" subunit, "" component, "or" system. Furthermore, aspects of the present application may be represented as a computer product, including computer readable program code, embodied in one or more computer readable media.

Example eight

An eighth embodiment of the present invention provides a computer-readable storage medium, on which a computer program is stored, where the computer program, when executed by a processor, implements a magnetic resonance frequency calibration method according to any of the embodiments of the present invention, where the method includes:

A computer readable signal medium may comprise a propagated data signal with computer program code embodied therein, for example, on a baseband or as part of a carrier wave. The propagated signal may take any of a variety of forms, including electromagnetic, optical, and the like, or any suitable combination. A computer readable signal medium may be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device. Program code on a computer readable signal medium may be propagated over any suitable medium, including radio, electrical cable, fiber optic cable, radio frequency signals, or the like, or any combination of the preceding.

Computer program code required for the operation of various portions of the present application may be written in any one or more programming languages, including an object oriented programming language such as Java, Scala, Smalltalk, Eiffel, JADE, Emerald, C + +, C #, VB.NET, Python, and the like, a conventional programming language such as C, Visual Basic, Fortran 2003, Perl, COBOL 2002, PHP, ABAP, a dynamic programming language such as Python, Ruby, and Groovy, or other programming languages, and the like. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any network format, such as a Local Area Network (LAN) or a Wide Area Network (WAN), or the connection may be made to an external computer (for example, through the Internet), or in a cloud computing environment, or as a service, such as a software as a service (SaaS).

Additionally, the order in which elements and sequences of the processes described herein are processed, the use of alphanumeric characters, or the use of other designations, is not intended to limit the order of the processes and methods described herein, unless explicitly claimed. While various presently contemplated embodiments of the invention have been discussed in the foregoing disclosure by way of example, it is to be understood that such detail is solely for that purpose and that the appended claims are not limited to the disclosed embodiments, but, on the contrary, are intended to cover all modifications and equivalent arrangements that are within the spirit and scope of the embodiments herein. For example, although the system components described above may be implemented by hardware devices, they may also be implemented by software-only solutions, such as installing the described system on an existing server or mobile device.

Similarly, it should be noted that in the preceding description of embodiments of the application, various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure aiding in the understanding of one or more of the embodiments. This method of disclosure, however, is not intended to require more features than are expressly recited in the claims. Indeed, the embodiments may be characterized as having less than all of the features of a single embodiment disclosed above.

Numerals describing the number of components, attributes, etc. are used in some embodiments, it being understood that such numerals used in the description of the embodiments are modified in some instances by the use of the modifier "about", "approximately" or "substantially". Unless otherwise indicated, "about", "approximately" or "substantially" indicates that the number allows a variation of ± 20%. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximations that may vary depending upon the desired properties of the individual embodiments. In some embodiments, the numerical parameter should take into account the specified significant digits and employ a general digit preserving approach. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the range are approximations, in the specific examples, such numerical values are set forth as precisely as possible within the scope of the application.

The entire contents of each patent, patent application publication, and other material cited in this application, such as articles, books, specifications, publications, documents, and the like, are hereby incorporated by reference into this application. Except where the application is filed in a manner inconsistent or contrary to the present disclosure, and except where the claim is filed in its broadest scope (whether present or later appended to the application) as well. It is noted that the descriptions, definitions and/or use of terms in this application shall control if they are inconsistent or contrary to the statements and/or uses of the present application in the material attached to this application.

Finally, it should be understood that the embodiments described herein are merely illustrative of the principles of the embodiments of the present application. Other variations are also possible within the scope of the present application. Thus, by way of example, and not limitation, alternative configurations of the embodiments of the present application can be viewed as being consistent with the teachings of the present application. Accordingly, the embodiments of the present application are not limited to only those embodiments explicitly described and depicted herein.

Claims

1. A method of magnetic resonance frequency calibration, comprising:

identifying peak-to-valley information in the frequency spectral lines or spectral information, wherein the peak-to-valley information includes at least one of a number of peaks and valleys, a peak amplitude, a valley depth, a peak frequency, a peak-to-peak spacing;

determining a corresponding water peak screening rule according to a preset calibration mode and the number of peaks in peak-valley information, determining peaks meeting conditions in the frequency spectrum line or the frequency spectrum information as water peaks according to the water peak screening rule, determining the frequency of the peaks meeting the conditions as water peak frequency, and determining the water peak frequency as the central frequency of the magnetic resonance system, wherein the preset calibration mode is one of a normal mode, a special mode and a silica gel mode, the special mode is used for carrying out frequency calibration on cervical vertebra, thoracic vertebra and cervical vertebra parts, the silica gel mode is used for carrying out frequency calibration on the mammary gland part implanted with the silica gel, and the normal mode is used for carrying out frequency calibration on the mammary gland part not implanted with the silica gel and human body parts except the vertebral body and the chest;

when the preset calibration mode is a silica gel mode, determining a corresponding water peak screening rule according to the preset calibration mode and the number of peaks in the peak-valley information, and determining peaks meeting conditions in the frequency spectrum line or the frequency spectrum information as water peaks according to the water peak screening rule, including:

if the number of peaks in the frequency spectrum line or the frequency spectrum information is more than or equal to 3, combining any three peaks in the frequency spectrum line or the frequency spectrum information to form at least one three-peak combination;

and determining the three-peak combination corresponding to the minimum evaluation function value as the optimal three-peak combination, and determining the peak with the highest frequency in the optimal three-peak combination as the water peak.

2. The method according to claim 1, wherein the preset calibration mode is a normal mode, wherein determining a corresponding water peak screening rule according to the preset calibration mode and the number of peaks in the peak-valley information, and determining a peak satisfying a condition in the frequency spectrum line or the frequency spectrum information as a water peak according to the water peak screening rule comprises:

and if the number of peaks in the frequency spectrum line or the frequency spectrum information is more than or equal to 2, determining at least one water-fat peak pair in the frequency spectrum line or the frequency spectrum information, screening a first optimal water-fat peak pair in the at least one water-fat peak pair, and determining a water peak according to the first optimal water-fat peak pair.

3. The method of claim 2, further comprising, after determining at least one water-fat peak pair in the frequency spectral line or spectral information:

4. The method of any one of claims 1-3, further comprising, after determining the water peak:

5. The method according to claim 1, wherein the preset calibration mode is a special mode, wherein determining a corresponding water peak screening rule according to the preset calibration mode and the number of peaks in the peak-valley information, and determining a peak satisfying a condition in the frequency spectrum line or the frequency spectrum information as a water peak according to the water peak screening rule comprises:

and if the number of peaks in the frequency spectrum line or the frequency spectrum information is more than or equal to 2, determining at least one water-fat peak pair in the frequency spectrum line or the frequency spectrum information, determining a second optimal water-fat peak pair according to a left-leaning principle, and determining a peak with the highest frequency in the second optimal water-fat peak pair as a water peak.

6. The method according to claim 1, wherein the preset calibration mode is a silica gel mode, wherein determining a corresponding water peak screening rule according to the preset calibration mode and the number of peaks in the peak-valley information, and determining a peak satisfying a condition in the frequency spectrum line or the frequency spectrum information as a water peak according to the water peak screening rule comprises:

and if the number of peaks in the frequency spectrum line or the frequency spectrum information is 2, determining the peak types of any two peaks according to the actual distance between the two peaks and a second standard distance, and determining a water peak according to the peak types, wherein the second standard distance comprises the peak-peak standard distance of any two peaks in a silica gel peak, a fat peak and a water peak.

7. A magnetic resonance imaging method, comprising:

determining a corresponding water peak screening rule according to a preset calibration mode and the number of peaks in peak-valley information, determining peaks meeting conditions in the frequency spectrum line or the frequency spectrum information as water peaks according to the water peak screening rule, determining the frequency of the peaks meeting the conditions as water peak frequency, and determining the water peak frequency as the central frequency of the magnetic resonance system, wherein the preset calibration mode is one of a normal mode, a special mode and a silica gel mode, the special mode is used for performing frequency calibration on cervical vertebra, thoracic vertebra and cervical vertebra parts, the silica gel mode is used for performing frequency calibration on the mammary gland part implanted with the silica gel, and the normal mode is used for performing frequency calibration on the mammary gland part not implanted with the silica gel and human body parts except the vertebral body and the chest;

reconstructing the magnetic resonance imaging signal to generate a magnetic resonance image;

8. A magnetic resonance system comprising a magnetic resonance apparatus and a computer apparatus, wherein the computer apparatus comprises a memory, one or more processors and a computer program stored on the memory and executable on the processors, characterized in that the processor when executing the program is operable to perform the method of any of claims 1-6.