CN116520225A - Method, system, device and medium for generating magnetic resonance image - Google Patents
Method, system, device and medium for generating magnetic resonance image Download PDFInfo
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Abstract
The invention discloses a method, a system, equipment and a medium for generating a magnetic resonance image, wherein the method comprises the following steps: acquiring a plurality of groups of first magnetic resonance images of a plurality of target persons, and acquiring position information of a target part in each group of first magnetic resonance images based on the plurality of groups of first magnetic resonance images; according to the plurality of position information, carrying out radio frequency emission field local shimming on a plurality of target parts to obtain the amplitude and the phase of the emission channel after local shimming respectively, thereby obtaining the amplitude and the phase of the emission channel after local shimming of a plurality of groups of radio frequency emission fields; acquiring a target amplitude and a target phase of a group of emission channels based on the amplitudes and phases of the emission channels after the local shimming of a plurality of groups of radio frequency emission fields; and taking the target amplitude and the target phase of a group of transmitting channels as the initial amplitude and the initial phase of the transmitting channels in the next scanning, and scanning a target person to generate a target magnetic resonance image, so that the local spatial distribution of the radio frequency transmitting field in the magnetic resonance image generation process is uniform.
Description
Technical Field
The present invention relates to the field of magnetic resonance imaging technology, and in particular, to a method, a system, an apparatus, and a medium for generating a magnetic resonance image.
Background
MRI (magnetic resonance imaging) is a medical imaging technique for medical diagnosis. MR (magnetic resonance) scanners use strong magnetic fields, magnetic field gradients, and radio waves to generate images of an object to be scanned (e.g., a tissue or organ in a human body). Cardiac magnetic resonance images are commonly used to evaluate cardiac functional parameters and diagnose cardiovascular disease, and are the gold standard for quantitative cardiac analysis. Compared with low-field magnetic resonance imaging, the ultra-high-field magnetic resonance imaging has higher signal-to-noise ratio and tissue contrast, and is more suitable for observing the fine structure and metabolic physiological change of heart tissue. However, the field intensity is increased to shorten the radio frequency wavelength, which is easy to form standing waves in the imaging field of human heart to cause B1 + The local spatial distribution of (radio frequency emission field) is uneven, so that the image is in a 'black hole', and the image quality and clinical diagnosis are affected.
Currently, B1 for ultra-high field magnetic resonance imaging + Spatially inhomogeneous, global B1 is mostly required in pre-clinical scan calibration + Shimming, which has long calibration time and is difficult to ensure B1 of scanned part in global shimming + And (5) uniformity. In addition to global shimming, local shimming is also a common way to shim a specific ROI (region of interest) region to improve B1 of that ROI region + Non-uniformity. Either global shimming or local shimming requires a calibration procedure. The process is affected by the respiration, heartbeat, electrocardiographic state and other factors of the patient, and the stability is insufficient.
Disclosure of Invention
The invention aims to overcome the defect of uneven local spatial distribution of a radio frequency emission field in the generation process of a magnetic resonance image in the prior art, and provides a generation method, a system, equipment and a medium of the magnetic resonance image.
The invention solves the technical problems by the following technical scheme:
the invention provides a generation method of a magnetic resonance image, which comprises the following steps:
acquiring a plurality of groups of first magnetic resonance images of a plurality of target persons, and acquiring position information of a target part in each group of first magnetic resonance images based on the plurality of groups of first magnetic resonance images;
according to the position information, carrying out radio frequency emission field local shimming on the target parts to obtain the amplitude and the phase of the emission channel after local shimming, so as to obtain the amplitude and the phase of the emission channel after local shimming of a plurality of groups of radio frequency emission fields;
acquiring a target amplitude and a target phase of a group of emission channels based on the amplitudes and phases of the emission channels after the local shimming of a plurality of groups of radio frequency emission fields;
and taking the target amplitude and the target phase of the group of transmitting channels as the initial amplitude and the initial phase of the transmitting channels in the next scanning, and scanning a target person to generate a target magnetic resonance image.
Preferably, the step of acquiring the position information of the target site in each set of the first magnetic resonance images based on the sets of the first magnetic resonance images includes:
and respectively acquiring the position information of the target part in each group of first magnetic resonance images by using an image recognition model based on the plurality of groups of first magnetic resonance images.
Preferably, the step of performing radio frequency emission field local shimming on the plurality of target parts to obtain the amplitude and the phase of the emission channel after local shimming respectively includes:
acquiring a plurality of groups of second magnetic resonance images of a plurality of target persons;
acquiring the transmission sensitivity of a plurality of groups of transmission channels based on a plurality of groups of the second magnetic resonance images;
calculating target weights corresponding to the emission sensitivities of the plurality of groups of emission channels by using a punishment function;
and based on the target weight, acquiring the amplitude and the phase of the transmission channel after the local shimming of a plurality of groups of radio frequency transmission fields.
Preferably, before the step of calculating the target weights of the emission sensitivities of the plurality of emission channels by using the penalty function, the step of performing radio frequency emission field local shimming on the plurality of target locations to obtain the amplitude and the phase of the emission channels after radio frequency emission field local shimming, respectively, further includes:
and applying a mask to the region outside the target part to obtain the amplitude and the phase of the transmission channel after the radio frequency transmission field is locally shimmed.
Preferably, the step of obtaining the target amplitude and the target phase of the group of transmission channels based on the amplitudes and the phases of the transmission channels after the local shimming of the plurality of groups of radio frequency transmission fields includes:
scanning a plurality of target persons by adopting the amplitude values and the phases of the transmission channels after the local shimming of a plurality of groups of radio frequency transmission fields to generate a plurality of groups of third magnetic resonance images;
judging whether each group of the third magnetic resonance images meets the requirements, if so, taking the amplitude and the phase of the transmitting channel corresponding to the third magnetic resonance images as the candidate amplitude and the candidate phase of the transmitting channel respectively;
and respectively acquiring a candidate amplitude average value and a candidate phase average value corresponding to the candidate amplitude and the candidate phase, and respectively taking the candidate amplitude average value and the candidate phase average value as a target amplitude and a target phase of a group of transmitting channels.
Preferably, the step of determining whether each set of the third magnetic resonance images meets the requirement includes:
acquiring a variation coefficient of a target part in a third magnetic resonance image generated by each group of emission channels based on the amplitude and phase scanning of the radio frequency emission field after local shimming;
and judging whether the variation coefficient is smaller than a preset threshold value, and if so, conforming to the requirement of the third magnetic resonance image.
Preferably, the step of obtaining the candidate amplitude average value and the candidate phase average value corresponding to the candidate amplitude and the candidate phase respectively includes:
selecting a third magnetic resonance image with the variation coefficient smaller than a preset threshold value;
constructing a histogram based on the amplitude and the phase corresponding to the third magnetic resonance image respectively;
and acquiring a candidate amplitude average value and a candidate phase average value corresponding to the candidate amplitude and the candidate phase based on the histogram.
The invention also provides a generation system of the magnetic resonance image, which comprises:
the first acquisition module is used for acquiring a plurality of groups of first magnetic resonance images of a plurality of target persons and acquiring the position information of a target part in each group of first magnetic resonance images based on the plurality of groups of first magnetic resonance images;
the second acquisition module is used for carrying out radio frequency emission field local shimming on the plurality of target parts according to the plurality of position information so as to respectively obtain the amplitude and the phase of the emission channel after the radio frequency emission field local shimming and obtain the amplitude and the phase of the emission channel after the multi-group radio frequency emission field local shimming;
the third acquisition module is used for acquiring the target amplitude and the target phase of one group of transmission channels based on the amplitude and the phase of the transmission channels after the local shimming of the multiple groups of radio frequency transmission fields;
and the scanning module is used for taking the target amplitude and the target phase of the group of emission channels as the initial amplitude and the initial phase of the emission channels in the next scanning, and scanning a target person to generate a target magnetic resonance image.
The invention also provides an electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, the processor implementing the method of generating a magnetic resonance image as described above when executing the computer program.
The invention also provides a computer readable storage medium having stored thereon a computer program which when executed by a processor implements a method of generating a magnetic resonance image as described above.
On the basis of conforming to the common knowledge in the field, the above preferred conditions can be arbitrarily combined to obtain the preferred examples of the invention.
The invention has the positive progress effects that:
according to the invention, a plurality of groups of first magnetic resonance images of a plurality of target persons are acquired, the position information of target parts in each group of first magnetic resonance images is acquired based on the plurality of groups of first magnetic resonance images, the amplitudes and phases of the transmission channels after the plurality of groups of radio frequency transmission field local shimming are acquired based on the radio frequency transmission field local shimming of the plurality of target parts, the target amplitudes and the target phases of one group of transmission channels are acquired based on the amplitudes and phases of the transmission channels after the plurality of groups of radio frequency transmission field local shimming, and the target amplitudes and the target phases of the group of transmission channels are taken as the initial amplitudes and the initial phases of the transmission channels in the next scanning, so that the target persons are scanned to generate the target magnetic resonance images.
Drawings
Fig. 1 is a flowchart of a method for generating a magnetic resonance image according to embodiment 1 of the present invention.
Fig. 2 is a flowchart of step 102 in embodiment 1 of the present invention.
Fig. 3 is a flowchart of step 103 in embodiment 1 of the present invention.
Fig. 4 is a schematic diagram of a histogram in embodiment 1 of the present invention.
Fig. 5 is a block diagram of a magnetic resonance image generation system according to embodiment 2 of the present invention.
Fig. 6 is a schematic block diagram of a second acquisition module in embodiment 2 of the present invention.
Fig. 7 is a schematic block diagram of a third acquisition module in embodiment 2 of the present invention.
Fig. 8 is a schematic structural diagram of an electronic device according to embodiment 3 of the present invention.
Detailed Description
The invention is further illustrated by means of the following examples, which are not intended to limit the scope of the invention.
Example 1
As shown in fig. 1, the present embodiment discloses a method for generating a magnetic resonance image, the method comprising:
step S101, acquiring a plurality of groups of first magnetic resonance images of a plurality of target persons, and acquiring position information of a target part in each group of first magnetic resonance images based on the plurality of groups of first magnetic resonance images;
specifically, multiple sets of first magnetic resonance images may be generated by scanning multiple target persons, such as volunteers, of different gender and size. A set of first magnetic resonance images is generated when each target person is scanned, and a target position corresponding to each target person is determined from the set of magnetic resonance images. Wherein one or more first magnetic resonance images may be included in a set of first magnetic resonance images. The first magnetic resonance image is an image for identifying a target region of a human body, and may be a GRE (gradient echo sequence) image or an FSE (fast spin echo sequence) image. The first magnetic resonance image includes anatomical information of a target person and includes at least a target site.
The target site in the present embodiment may be the heart of the volunteer or other sites in the human body of the volunteer, for example, the liver, stomach, etc. The target part is not limited to a specific part in a human body, and can be specifically determined according to actual requirements.
Step S102, according to a plurality of pieces of position information, carrying out radio frequency emission field local shimming on a plurality of target parts respectively to obtain the amplitude and the phase of a emission channel after local shimming respectively, so as to obtain the amplitude and the phase of a plurality of groups of emission channels after local shimming of radio frequency emission fields;
in the scheme, the local shimming area of the radio frequency emission field is determined according to the position information, so that the local shimming of the radio frequency emission field of the target part is realized.
In the scheme, the amplitude and the phase are parameters of a transmitting channel of the magnetic resonance equipment, and influence the amplitude and the phase of the radio frequency pulse and influence the transmitting sensitivity distribution of the transmitting channel. The amplitude, i.e., amplitude, is typically used to characterize the strength and power of the radio frequency signals, and the phase is typically used to characterize the angular offset between the radio frequency signals, and the phase is typically in units of "degrees" or "radians". The amplitude and phase of the RF signal affect the uniformity of the pulses of the RF signal, which causes an RF transmit field (B1 + ) And thus affects the quality of the scanned image.
In this scenario, the magnetic resonance apparatus comprises a plurality of transmit channels. For each target person, a corresponding set of magnitudes and phases may be obtained after shimming. Wherein the set of amplitudes and phases specifically comprises values of amplitudes and phases of a plurality of transmit channels of the magnetic resonance apparatus. Multiple groups of amplitude values and phases can be obtained after shimming by multiple scanned persons. Step S103, acquiring a target amplitude and a target phase of a group of emission channels based on the amplitudes and phases of the emission channels after local shimming of a plurality of groups of radio frequency emission fields;
in the scheme, each target person corresponds to the amplitude and the phase of a transmission channel after local shimming of a group of radio frequency transmission fields. And obtaining the amplitude and the phase of a group of transmission channels which are most satisfactory as a target amplitude and a target phase through the amplitude and the phase of the transmission channels after the local shimming of a plurality of groups of radio frequency transmission fields.
Step S104, taking the target amplitude and the target phase of the group of emission channels as the initial amplitude and the initial phase of the emission channels in the next scanning, and scanning a target person to generate a target magnetic resonance image.
Specifically, the target person is scanned to generate a target magnetic resonance image by using the obtained target amplitude and target phase of a group of emission channels as parameters of a magnetic resonance image scanning system, namely as the initial amplitude and initial phase of the emission channels in the next scanning.
In the scheme, compared with the traditional method of scanning a target person by adopting the default amplitude and phase of the magnetic resonance equipment, the amplitude and phase of the radio frequency signal in the scanning process have relatively smaller influence on the pulse uniformity of the radio frequency signal by taking the amplitude and phase of the obtained transmitting channel which meets the requirements as the initial amplitude and initial phase of the transmitting channel in the next scanning, thereby leading the pulse uniformity of the radio frequency signal to have a higher pulse uniformity on the radio frequency transmitting field (B1 + ) The influence of the uniformity of the local spatial distribution of the radio frequency emission field in the magnetic resonance image generation process is relatively smaller, and the quality of the scanning image and the accuracy of clinical diagnosis are further improved.
In an implementation manner, the step S101 specifically includes:
and respectively acquiring the position information of the target part in each group of first magnetic resonance images by using an image recognition model based on the plurality of groups of first magnetic resonance images. The image recognition model is a model which is obtained by training a large number of image samples in advance, and the geometric form and the position information of the target part are output after the target part is recognized.
In this scheme, the first magnetic resonance image is specifically obtained by scanning a magnetic resonance device with a corresponding preset sequence, and before the scanning with the preset sequence, the magnetic resonance device needs to be calibrated. B1B 1 + The shimming is used as part of a calibration stage, and a plurality of first magnetic resonance images can be generated by scanning at any stage before shimming, and the first magnetic resonance images are used for identifying and segmenting out a target part.
In the scheme, the image recognition model is adopted to acquire the position information of the target part in each group of first magnetic resonance images, so that the position information of the target part is more accurate, the local shimming area of the radio frequency emission field is more accurate, the accuracy of the amplitude and the phase of the obtained local shimming rear emission channel is ensured, and the uniformity of the spatial distribution of the radio frequency emission field after local shimming in the magnetic resonance image generation process is improved.
As shown in fig. 2, in one implementation, the step 102 specifically includes:
s1021, acquiring a plurality of groups of second magnetic resonance images of a plurality of target persons;
in this solution, each target person corresponds to a set of second magnetic resonance images, where a set of second magnetic resonance images may include a plurality of second magnetic resonance images. The second magnetic resonance image is an image for acquiring the transmit sensitivity of the transmit channel. The second magnetic resonance image comprises B1 + Distribution information of the field map.
Step S1022, acquiring the transmission sensitivity of a plurality of groups of transmission channels based on a plurality of groups of the second magnetic resonance images; wherein the emission sensitivity of the emission channel can be B1 + Field map characterization.
In this scheme, each target person corresponds to a set of second magnetic resonance images, and each set of second magnetic resonance images corresponds to the emission sensitivity of a set of emission channels.
Step S1023, calculating target weights corresponding to the emission sensitivities of the plurality of groups of emission channels by using a penalty function;
specifically, the penalty function is used to calculate the following formula:
wherein J (w) represents a penalty function, the result of which represents a target weight corresponding to the emission sensitivity of the emission channel, S i Characterizing the emission sensitivity of the ith emission channel, T characterizes an optimization target value, w i Characterizing the amplitude and the phase of the ith channel in a complex form; n represents the number of emission channels, R represents the index of each point in the emission sensitivity, R represents the number of points in the emission sensitivity, and λ represents a constant greater than or equal to 0.
Step S1024, based on the target weight, the amplitude and the phase of the transmission channel after the local shimming of the plurality of groups of radio frequency transmission fields are obtained.
In this scheme, the weight of the transmit sensitivity of the transmit channel is a complex number, where the complex number includes an amplitude and a phase, so that the target weight of the sensitivity of each transmit channel corresponds to the amplitude and the phase of each transmit channel.
In the scheme, the penalty function is adopted to calculate the target weights corresponding to the emission sensitivities of the plurality of groups of emission channels, so that the obtained target weights are more accurate, then, based on the target weights, the amplitude values and the phases of the emission channels after the local shimming of the plurality of groups of radio frequency emission fields are obtained, so that the amplitude values and the phases of the emission channels after the local shimming of the plurality of groups of radio frequency emission fields are more accurate, and further, the local spatial distribution uniformity of the radio frequency emission fields in the magnetic resonance image generation process is ensured.
In one embodiment, before the step of calculating the target weights of the emission sensitivities of the plurality of emission channels by using the penalty function, the step of performing radio frequency emission field local shimming on the plurality of target sites to obtain the amplitudes and phases of the emission channels after radio frequency emission field local shimming, respectively, further includes:
and applying a mask to the region outside the target part to obtain the amplitude and the phase of the transmission channel after the radio frequency transmission field is locally shimmed.
In the scheme, the mask is applied to the region outside the target part, so that the radio frequency emission field local shimming treatment can be more accurately carried out on the target part, thereby obtaining B1 + And finally, based on the emission sensitivity of the emission channel, the amplitude and the phase of the emission channel after the local shimming of the radio frequency emission field is acquired are more accurate.
In particular, the step of performing masking of the region outside the target site may be performed after the step of acquiring a plurality of sets of second magnetic resonance images generated by a plurality of target persons and before the step of acquiring the emission sensitivities of the plurality of sets of emission channels. Alternatively, the step of masking the region outside the target region may be performed after the step of acquiring the emission sensitivities of the plurality of sets of emission channels and before the step of calculating the target weights corresponding to the emission sensitivities of the plurality of sets of emission channels using a penalty function. In summary, the step of masking the region outside the target region may be performed just before the step of calculating the target weights for the emission sensitivity multiple emission groups of the multiple emission channels using a penalty function.
In a specific embodiment, for example, when the target site is the heart, a mask is applied to an area outside the heart area, so that the amplitude and the phase of the transmission channel after the local shimming of the plurality of groups of radio frequency transmission fields are more accurate, and further, the local spatial distribution of the radio frequency transmission fields in the magnetic resonance image generation process is ensured to be uniform.
As shown in fig. 3, in one implementation, the step S103 includes:
step S1031, scanning a plurality of target persons by adopting the amplitude values and the phases of the transmission channels after the local shimming of a plurality of groups of radio frequency transmission fields to generate a plurality of groups of third magnetic resonance images;
specifically, the amplitude and the phase of the transmission channel after the local shimming of each group of radio frequency transmission fields are adopted to scan the corresponding target personnel to generate a group of third magnetic resonance images, so that the amplitude and the phase of the transmission channel after the local shimming of a plurality of groups of radio frequency transmission fields are adopted to scan a plurality of target personnel to generate a plurality of groups of third magnetic resonance images. Wherein the third magnetic resonance image is an image for judging whether the amplitude and the phase of the transmitting channel meet the requirements, and the third magnetic resonance image can be B1 + Field diagram. The third magnetic resonance image may include structural information of the scanned object, or may include B1 + Distribution information of the field map. The corresponding target person is the target person in step 101.
Step S1032, determining whether each set of the third magnetic resonance images meets the requirement, if yes, executing step S1033, and if not, disregarding the third magnetic resonance images which do not meet the requirement.
Specifically, the variation coefficient of the target part in each group of third magnetic resonance images is obtained, whether the variation coefficient is smaller than a preset threshold value or not is judged, and if the variation coefficient is smaller than the preset threshold value, the third magnetic resonance images meet the requirements.
Wherein the variation coefficient is B1 of the third magnetic resonance image + B1 of field diagram + Standard deviation of values with B1 + The ratio of the average values of the values, when the coefficient of variation is smaller, characterizes the third magnetic resonance image B1 + The better the uniformity of the field map, i.e. the better the uniformity after local shimming of the radio frequency transmit field characterizing the target region.
In the scheme, the comparison of the variation coefficient of the target part in each group of third magnetic resonance images with the preset threshold value is used as a judgment condition to ensure that the screening meets the variation coefficient of the requirement, namely the third magnetic resonance image B1 + The uniformity of the field map ensures the accuracy of the screened candidate amplitude and candidate phase, and further ensures the uniformity of local spatial distribution of the radio frequency transmission field in the generation process of the magnetic resonance image.
Step S1033, using the amplitude and the phase of the transmitting channel corresponding to the third magnetic resonance image as the candidate amplitude and the candidate phase of the transmitting channel respectively;
step S1034, respectively obtaining a candidate amplitude average value and a candidate phase average value corresponding to the candidate amplitude and the candidate phase, and respectively using the candidate amplitude average value and the candidate phase average value as a target amplitude and a target phase of a group of transmitting channels.
In this solution, the candidate amplitude average value and the candidate phase average value are only one of the preferred solutions by using the candidate amplitude average value and the candidate phase average value as the target amplitude and the target phase of a group of transmitting channels, and other modes may be used to obtain the target amplitude and the target phase according to the needs of the actual user, which is not limited herein.
In one implementation manner, the step S1034 specifically includes:
selecting a third magnetic resonance image with the variation coefficient smaller than a preset threshold value;
constructing a histogram based on the amplitude and the phase corresponding to the third magnetic resonance image respectively;
and acquiring a candidate amplitude average value and a candidate phase average value corresponding to the candidate amplitude and the candidate phase based on the histogram.
Specifically, selecting a third magnetic resonance image with a variation coefficient smaller than a preset threshold, namely screening a third magnetic resonance image with a low variation coefficient, and constructing a histogram according to the amplitude and the phase of each channel, wherein the phases are divided into intervals from-180 degrees to 180 degrees by taking alpha as an interval, and alpha represents the preset angle of the interval. Screening out interval data with low density of each channel, carrying out average calculation on the phase of the remaining interval and the corresponding amplitude thereof, and taking the calculated candidate amplitude average value and candidate phase average value as a group of target amplitude and target phase of the transmitting channel. According to the method, the histogram is constructed by adopting the amplitude and the phase corresponding to the third magnetic resonance image with the variation coefficient smaller than the preset threshold value, so that the candidate amplitude average value and the candidate phase average value corresponding to the candidate amplitude and the candidate phase are obtained, the target amplitude and the target phase of a group of optimal transmitting channels are ensured to be obtained, the initial amplitude and the initial phase of the transmitting channels in the next scanning process are used for scanning target personnel to generate the target magnetic resonance image, and the quality of the scanned image and the accuracy of clinical diagnosis are further improved.
Taking the amplitude-phase screening of a certain transmitting channel as an example, as shown in fig. 4 as a histogram, the abscissa uniformly segments the amplitude value (0-1.0), and every 0.1 is a zone, and the ordinate represents the frequency of each zone, namely, the number of target personnel falling into the amplitude value of the corresponding zone is represented. As can be seen from the graph, the frequency of the amplitude of the interval (0.1-0.3) and the amplitude of the interval (0.9-1.0) is small, which is an interval with low data density, that is, the number of target persons characterizing the amplitude falling into the interval (0.1-0.3) and the interval (0.9-1.0) is small. Most of the data is concentrated in the (0.5-0.8) interval, which is a high density interval, i.e. the number of target persons characterizing the amplitude falling in the (0.5-0.8) interval is high. During calculation, the data of the interval with low density, namely the interval (0.1-0.3) and the interval (0.9-1.0), is removed, and the amplitude of the rest interval, namely the interval (0.5-0.8), is subjected to average calculation, so that a group of optimal target amplitude and target phase of the emission channel are obtained, and serve as the initial amplitude and initial phase of the emission channel in the next scanning, and further the quality of a scanned image and the accuracy of clinical diagnosis are improved.
Example 2
As shown in fig. 5, the present embodiment discloses a generation system of a magnetic resonance image, which is used for correspondingly implementing the generation method of the magnetic resonance image of embodiment 1, and the generation system includes:
the first acquisition module 1 acquires a plurality of groups of first magnetic resonance images of a plurality of target persons, and acquires position information of a target part in each group of first magnetic resonance images based on the plurality of first magnetic resonance images;
the second obtaining module 2 is configured to perform local shimming of the radio frequency transmission field on the multiple target locations according to the multiple pieces of location information, so as to obtain the amplitude and the phase of the transmission channel after local shimming of the radio frequency transmission field, and obtain the amplitude and the phase of the transmission channel after local shimming of multiple groups of radio frequency transmission fields;
a third obtaining module 3, configured to obtain a target amplitude and a target phase of a group of transmission channels based on the amplitudes and phases of the transmission channels after the local shimming of the multiple groups of radio frequency transmission fields;
and the scanning module 4 is used for taking the target amplitude and the target phase of the group of emission channels as the initial amplitude and the initial phase of the emission channels in the next scanning, and scanning a target person to generate a target magnetic resonance image.
In one embodiment, the second obtaining module 2 is further configured to:
and respectively acquiring the position information of the target part in each group of first magnetic resonance images by using an image recognition model based on the plurality of groups of first magnetic resonance images.
As shown in fig. 6, in one embodiment, the second obtaining module 2 specifically includes:
a first acquisition unit 21 for acquiring a plurality of sets of second magnetic resonance images of a plurality of target persons;
a second acquisition unit 22 for acquiring a plurality of sets of transmissions based on a plurality of sets of the second magnetic resonance imagesThe emission sensitivity of the channel; wherein the emission sensitivity of the emission channel can be B1 + Field map characterization.
A calculating unit 23, configured to calculate target weights corresponding to the emission sensitivities of the multiple groups of emission channels by using a penalty function;
specifically, the penalty function is used to calculate the following formula:
wherein J (w) represents a penalty function, the result of which represents a target weight corresponding to the emission sensitivity of the emission channel, S i Characterizing the emission sensitivity of the ith emission channel, T characterizes an optimization target value, w i Characterizing the amplitude and the phase of the ith channel in a complex form; n represents the number of emission channels, R represents the index of each point in the emission sensitivity, R represents the number of points in the emission sensitivity, and λ represents a constant greater than or equal to 0.
And a third obtaining unit 24, configured to obtain the amplitude and the phase of the transmission channel after the local shimming of the multiple sets of radio frequency transmission fields based on the target weight.
In one embodiment, the second acquisition module 2 further comprises:
and a mask applying unit 25, configured to apply a mask to an area outside the target portion, so as to obtain the amplitude and the phase of the transmission channel after the radio frequency transmission field is locally shimmed.
As shown in fig. 7, in one embodiment, the third obtaining module 3 includes:
the scanning unit 31 is configured to scan a plurality of target persons by using the amplitudes and phases of the transmission channels after the local shimming of the plurality of groups of radio frequency transmission fields to generate a plurality of groups of third magnetic resonance images;
a judging unit 32, configured to judge whether each set of the third magnetic resonance images meets a requirement, if yes, call the first determining unit 33, and if not, disregard the third magnetic resonance images that do not meet the requirement;
a first determining unit 33, configured to take the amplitude and the phase of the transmission channel corresponding to the third magnetic resonance image as a candidate amplitude and a candidate phase of the transmission channel respectively;
the second determining unit 34 obtains the candidate amplitude average value and the candidate phase average value corresponding to the candidate amplitude and the candidate phase, respectively, and uses the candidate amplitude average value and the candidate phase average value as the target amplitude and the target phase of a group of transmission channels, respectively.
In one implementation, the determining unit 32 is specifically configured to:
acquiring a variation coefficient of a target part in a third magnetic resonance image generated by each group of emission channels based on the amplitude and phase scanning of the radio frequency emission field after local shimming;
and judging whether the variation coefficient is smaller than a preset threshold value, and if so, conforming to the requirement of the third magnetic resonance image.
In one embodiment, the first determining unit 33 is specifically configured to include:
selecting a third magnetic resonance image with the variation coefficient smaller than a preset threshold value;
constructing a histogram based on the amplitude and the phase corresponding to the third magnetic resonance image respectively;
and acquiring a candidate amplitude average value and a candidate phase average value corresponding to the candidate amplitude and the candidate phase based on the histogram.
Example 3
Fig. 8 is a schematic structural diagram of an electronic device according to an embodiment of the present invention. The electronic device comprises a memory, a processor and a computer program stored on the memory and used for running on the processor, wherein the processor realizes the generation method of the magnetic resonance image provided in the embodiment 1 when executing the program. The electronic device 40 shown in fig. 8 is merely an example and should not be construed as limiting the functionality and scope of use of embodiments of the present invention.
As shown in fig. 8, the electronic device 40 may be embodied in the form of a general purpose computing device, which may be a server device, for example. Components of electronic device 40 may include, but are not limited to: the at least one processor 41, the at least one memory 42, a bus 43 connecting the different system components, including the memory 42 and the processor 41.
The bus 43 includes a data bus, an address bus, and a control bus.
Memory 42 may include volatile memory such as Random Access Memory (RAM) 421 and/or cache memory 422, and may further include Read Only Memory (ROM) 423.
Memory 42 may also include a program/utility 425 having a set (at least one) of program modules 424, such program modules 424 including, but not limited to: an operating system, one or more application programs, other program modules, and program data, each or some combination of which may include an implementation of a network environment.
The processor 41 executes various functional applications and data processing such as the generation method of a magnetic resonance image provided in embodiment 1 of the present invention by executing a computer program stored in the memory 42.
The electronic device 40 may also communicate with one or more external devices 44 (e.g., keyboard, pointing device, etc.). Such communication may be through an input/output (I/O) interface 45. Also, model-generating device 40 may also communicate with one or more networks, such as a Local Area Network (LAN), a Wide Area Network (WAN), and/or a public network, such as the internet, via network adapter 46. As shown, the network adapter 46 communicates with the other modules of the model-generating device 40 via the bus 43. It should be appreciated that although not shown in the figures, other hardware and/or software modules may be used in connection with the model-generating device 40, including, but not limited to: microcode, device drivers, redundant processors, external disk drive arrays, RAID (disk array) systems, tape drives, data backup storage systems, and the like.
It should be noted that although several units/modules or sub-units/modules of an electronic device are mentioned in the above detailed description, such a division is merely exemplary and not mandatory. Indeed, the features and functionality of two or more units/modules described above may be embodied in one unit/module in accordance with embodiments of the present invention. Conversely, the features and functions of one unit/module described above may be further divided into ones that are embodied by a plurality of units/modules.
Example 4
The present embodiment provides a computer-readable storage medium having stored thereon a computer program which, when executed by a processor, implements the method of generating a magnetic resonance image provided by embodiment 1.
More specifically, among others, readable storage media may be employed including, but not limited to: portable disk, hard disk, random access memory, read only memory, erasable programmable read only memory, optical storage device, magnetic storage device, or any suitable combination of the foregoing.
In a possible embodiment, the invention may also be implemented in the form of a program product comprising program code for causing a terminal device to carry out the method of generating a magnetic resonance image provided by embodiment 1, when said program product is run on the terminal device.
Wherein the program code for carrying out the invention may be written in any combination of one or more programming languages, which program code may execute entirely on the user device, partly on the user device, as a stand-alone software package, partly on the user device and partly on the remote device or entirely on the remote device.
While specific embodiments of the invention have been described above, it will be appreciated by those skilled in the art that this is by way of example only, and the scope of the invention is defined by the appended claims. Various changes and modifications to these embodiments may be made by those skilled in the art without departing from the principles and spirit of the invention, but such changes and modifications fall within the scope of the invention.
Claims (10)
1. A method of generating a magnetic resonance image, the method comprising:
acquiring a plurality of groups of first magnetic resonance images of a plurality of target persons, and acquiring position information of a target part in each group of first magnetic resonance images based on the plurality of groups of first magnetic resonance images;
according to the position information, carrying out radio frequency emission field local shimming on the target parts to obtain the amplitude and the phase of the emission channel after local shimming, so as to obtain the amplitude and the phase of the emission channel after local shimming of a plurality of groups of radio frequency emission fields;
acquiring a target amplitude and a target phase of a group of emission channels based on the amplitudes and phases of the emission channels after the local shimming of a plurality of groups of radio frequency emission fields;
and taking the target amplitude and the target phase of the group of transmitting channels as the initial amplitude and the initial phase of the transmitting channels in the next scanning, and scanning a target person to generate a target magnetic resonance image.
2. The method of generating magnetic resonance images as set forth in claim 1, wherein the step of acquiring the positional information of the target site in each of the plurality of sets of the first magnetic resonance images based on the plurality of sets of the first magnetic resonance images includes:
and respectively acquiring the position information of the target part in each group of first magnetic resonance images by using an image recognition model based on the plurality of groups of first magnetic resonance images.
3. The method of generating a magnetic resonance image as set forth in claim 1, wherein the step of locally shimming the radio frequency transmit field for each of the plurality of target sites to obtain the amplitudes and phases of the locally shimmed transmit channels, respectively, includes:
acquiring a plurality of groups of second magnetic resonance images of a plurality of target persons;
acquiring the transmission sensitivity of a plurality of groups of transmission channels based on a plurality of groups of the second magnetic resonance images;
calculating target weights corresponding to the emission sensitivities of the plurality of groups of emission channels by using a punishment function;
and based on the target weight, acquiring the amplitude and the phase of the transmission channel after the local shimming of a plurality of groups of radio frequency transmission fields.
4. The method of generating a magnetic resonance image as set forth in claim 3, wherein, before the step of calculating the target weights corresponding to the emission sensitivities of the plurality of sets of emission channels using the penalty function, the step of performing radio frequency emission field local shimming on the plurality of target sites to obtain the amplitudes and phases of the emission channels after radio frequency emission field local shimming, respectively, further includes:
and applying a mask to the region outside the target part to obtain the amplitude and the phase of the transmission channel after the radio frequency transmission field is locally shimmed.
5. The method of generating a magnetic resonance image as set forth in claim 1, wherein the step of obtaining the target amplitude and the target phase of a set of transmit channels based on the amplitudes and phases of the transmit channels after the local shimming of the plurality of sets of radio frequency transmit fields comprises:
scanning a plurality of target persons by adopting the amplitude values and the phases of the transmission channels after the local shimming of a plurality of groups of radio frequency transmission fields to generate a plurality of groups of third magnetic resonance images;
judging whether each group of the third magnetic resonance images meets the requirements, if so, taking the amplitude and the phase of the transmitting channel corresponding to the third magnetic resonance images as the candidate amplitude and the candidate phase of the transmitting channel respectively;
and respectively acquiring a candidate amplitude average value and a candidate phase average value corresponding to the candidate amplitude and the candidate phase, and respectively taking the candidate amplitude average value and the candidate phase average value as a target amplitude and a target phase of a group of transmitting channels.
6. The method of generating magnetic resonance images as set forth in claim 5, wherein the step of determining whether each set of the third magnetic resonance images meets the requirement comprises:
acquiring a variation coefficient of a target part in a third magnetic resonance image generated by each group of emission channels based on the amplitude and phase scanning of the radio frequency emission field after local shimming;
and judging whether the variation coefficient is smaller than a preset threshold value, and if so, conforming to the requirement of the third magnetic resonance image.
7. The method of generating a magnetic resonance image as set forth in claim 6, wherein the step of acquiring the candidate amplitude average value and the candidate phase average value corresponding to the candidate amplitude and the candidate phase, respectively, includes:
selecting a third magnetic resonance image with the variation coefficient smaller than a preset threshold value;
constructing a histogram based on the amplitude and the phase corresponding to the third magnetic resonance image respectively;
and acquiring a candidate amplitude average value and a candidate phase average value corresponding to the candidate amplitude and the candidate phase based on the histogram.
8. A generation system for a magnetic resonance image, the generation system comprising:
the first acquisition module is used for acquiring a plurality of groups of first magnetic resonance images of a plurality of target persons and acquiring the position information of a target part in each group of first magnetic resonance images based on the plurality of groups of first magnetic resonance images;
the second acquisition module is used for carrying out radio frequency emission field local shimming on the plurality of target parts according to the plurality of position information so as to respectively obtain the amplitude and the phase of the emission channel after the radio frequency emission field local shimming and obtain the amplitude and the phase of the emission channel after the multi-group radio frequency emission field local shimming;
the third acquisition module is used for acquiring the target amplitude and the target phase of one group of transmission channels based on the amplitude and the phase of the transmission channels after the local shimming of the multiple groups of radio frequency transmission fields;
and the scanning module is used for taking the target amplitude and the target phase of the group of emission channels as the initial amplitude and the initial phase of the emission channels in the next scanning, and scanning a target person to generate a target magnetic resonance image.
9. An electronic device comprising a memory, a processor and a computer program stored on the memory for execution on the processor, characterized in that the processor implements the method of generating a magnetic resonance image according to any one of claims 1 to 7 when executing the computer program.
10. A computer-readable storage medium, on which a computer program is stored, characterized in that the computer program, when being executed by a processor, implements a method of generating a magnetic resonance image according to any one of claims 1 to 7.
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