CN116106806A - Multi-core imaging parameter determination method, device and system - Google Patents
Multi-core imaging parameter determination method, device and system Download PDFInfo
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- CN116106806A CN116106806A CN202310366296.8A CN202310366296A CN116106806A CN 116106806 A CN116106806 A CN 116106806A CN 202310366296 A CN202310366296 A CN 202310366296A CN 116106806 A CN116106806 A CN 116106806A
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Abstract
The application relates to a multi-core imaging parameter determining method, device and system, wherein the multi-core imaging parameter determining method comprises the following steps: acquiring imaging attributes and sampling parameters of a plurality of nuclides; determining the gradient strength of a target layer selection according to imaging attributes and sampling parameters of a plurality of nuclides; determining a target radio frequency pulse width and a target time bandwidth product of each nuclide according to the target layer-selecting gradient strength; determining target readout gradient strength according to imaging properties and sampling parameters of a plurality of nuclides; and determining the target acquisition time of each nuclide according to the target readout gradient intensity. According to the multi-core imaging determining method, an effective and feasible multi-core imaging determining method is provided, and the problem that an imaging parameter determining method aiming at a multi-nuclear magnetic resonance imaging technology is lacked in the related technology is solved.
Description
Technical Field
The present disclosure relates to the field of magnetic resonance imaging, and in particular, to a method, apparatus, and system for determining multi-core imaging parameters.
Background
Common magnetic resonance imaging techniques are mainly used for 1 The H nuclide is imaged, other nuclides which naturally exist in the body and can also perform magnetic resonance imaging also exist 23 Na、 31 P, etc., in addition, can also be exogenously input 19 F、 129 Xe, etc. Polynucleic imaging can provide information on metabolism, distribution and the like in a body, and is a great development hot spot in recent years.
Multi-core imaging increases timing constraints compared to single-species imaging. Due to removal of 1 H and 19 the nuclide magnetic rotation outside F is lower, and the signal to noise ratio is lower under the same field intensity; different nuclidesDifferent coil transmission efficiency leads to different transmission power to be configured; different nuclear species have different longitudinal magnetization relaxation time constants, etc., which cause the imaging sequence parameters of each nuclear species to be adjusted when imaging multiple nuclear species. Due to the aforementioned timing constraints, the adjustment of imaging parameters is more limited than single species imaging.
The existing imaging parameter determination method mainly aims at single nuclear magnetic resonance imaging, and for the multi-nuclear magnetic resonance imaging technology, a mature imaging parameter determination method is lacking.
Disclosure of Invention
The invention provides a multi-core imaging parameter determining method, device and system, which are used for solving the problem that the related technology lacks an imaging parameter determining method aiming at a multi-nuclear magnetic resonance imaging technology.
In a first aspect, the present invention provides a method for determining multi-core imaging parameters, the method comprising:
Acquiring imaging attributes and sampling parameters of a plurality of nuclides;
determining the gradient strength of a target layer selection according to imaging attributes and sampling parameters of a plurality of nuclides;
determining a target radio frequency pulse width and a target time bandwidth product of each nuclide according to the target layer-selecting gradient strength;
determining target readout gradient strength according to imaging properties and sampling parameters of a plurality of nuclides;
and determining the target acquisition time of each nuclide according to the target readout gradient intensity.
In some of these embodiments, said determining a target slice-select gradient strength from said imaging properties and said sampling parameters comprises:
determining a layer selection gradient value of each nuclide according to imaging attributes and sampling parameters of the nuclide;
and determining the target layer selection gradient strength according to the minimum layer selection gradient value in the layer selection gradient values.
In some of these embodiments, the imaging attributes include: t (T) 1 Relaxation time constant and imaging relation, wherein the imaging relation is the corresponding relation between radio frequency emission voltage and excitation flip angle;
the sampling parameters include: an imaging field of view;
the determining the slice-selecting gradient value of the nuclide according to the imaging parameter and the sampling parameter of the nuclide comprises:
T according to the nuclide 1 A relaxation time constant, determining an excitation flip angle of the species;
a slice-selective gradient value of the nuclear species is determined based on the excitation flip angle, imaging relationship, and imaging field of view of the nuclear species.
In some of these embodiments, said determining said target slice selection gradient strength from a smallest slice selection gradient value of a number of said slice selection gradient values comprises:
determining a gradient transform coefficient, the gradient transform coefficient being greater than 0 and less than or equal to 1;
and determining the product of the minimum selected layer gradient value and the gradient transformation coefficient as the target selected layer gradient strength.
In some of these embodiments, the imaging attributes include: t (T) 2 × Relaxation time constant, T 2 × The relaxation time constant is an apparent relaxation time constant affected by magnetic field inhomogeneities; the sampling parameters include: an imaging field of view;
the method further comprises the steps of:
according to a plurality of said T 2 × Shortest T in relaxation time constant 2 × A relaxation time constant, determining a temporary time-bandwidth product for each of said species;
the determining the product of the target radio frequency pulse width and the target time bandwidth of each nuclide according to the target layer-selecting gradient strength comprises:
determining a temporary radio frequency bandwidth of each nuclide according to the target layer-selecting gradient strength and the imaging field of view of the nuclide;
Determining a temporary radio frequency pulse width of each nuclide according to the product of the temporary radio frequency bandwidth and the temporary time bandwidth of the nuclide;
and respectively aiming at each nuclide, and determining the target time bandwidth and the target radio frequency pulse width of the nuclide according to the temporary time bandwidth and the temporary radio frequency pulse width of the nuclide.
In some of these embodiments, said T is according to a number of said T 2 × Shortest T in relaxation time constant 2 × Determining the temporal bandwidth product of each of the nuclides includes:
when the shortest T 2 × Determining a first preset value as a temporary time-bandwidth product for each of the species when the relaxation time constant is less than or equal to a first threshold;
when the shortest T 2 × And when the relaxation time constant is larger than the first threshold and smaller than or equal to a second threshold, determining a second preset value corresponding to each nuclide as a respective temporary time-bandwidth product.
In some of these embodiments, the determining the target time bandwidth product and the target radio frequency pulse width for the species from the temporary time bandwidth product and the temporary radio frequency pulse width for the species comprises:
determining the maximum temporary radio frequency pulse width in a plurality of temporary radio frequency pulse widths;
When the nuclide meets the updating condition, increasing the temporary time-bandwidth product of the nuclide by a unit value, and updating the temporary radio frequency pulse width of the nuclide; wherein the update condition includes: the quotient of the product of the temporary time bandwidth of the nuclide and the temporary radio frequency bandwidth is smaller than or equal to the maximum temporary radio frequency pulse width after the product of the temporary time bandwidth of the nuclide is increased by a unit value;
and respectively determining the updated temporary time bandwidth and the temporary radio frequency pulse width of the nuclide as the target time bandwidth and the target radio frequency pulse width of the nuclide.
In some of these embodiments, said determining the target readout gradient strength from imaging properties and sampling parameters of a number of said species comprises:
for each nuclide, determining a readout gradient value of the nuclide according to imaging parameters and sampling parameters of the nuclide;
and determining the target readout gradient intensity according to the maximum readout gradient value in the plurality of readout gradient values.
In some of these embodiments, the imaging attributes include: t (T) 2 × Relaxation time constant, T 2 × The relaxation time constant is an apparent relaxation time constant affected by magnetic field inhomogeneities; the sampling parameters include: imaging field of view and sampling resolution;
The determining the target readout gradient strength according to the imaging properties and sampling parameters of the plurality of nuclides further comprises:
according to a plurality of said T 2 × Shortest T in relaxation time constant 2 × A relaxation time constant, determining a maximum acquisition time;
the determining the readout gradient value of the nuclear species according to the imaging parameter and the sampling parameter of the nuclear species comprises:
and determining a readout gradient value of the nuclide according to the maximum acquisition time, the sampling resolution of the nuclide and the imaging field of view.
In some of these embodiments, said T is according to a number of said T 2 × Shortest T in relaxation time constant 2 × The relaxation time constant, determining the maximum acquisition time comprises:
when the shortest T 2 × When the relaxation time constant is less than or equal to a third threshold value, the shortest T is set 2 × A relaxation time constant is determined as the maximum acquisition time;
when the shortest T 2 × And when the relaxation time constant is larger than the third threshold value, determining a third preset value as the maximum acquisition time.
In some of these embodiments, said determining said target readout gradient strength from a largest readout gradient value of a number of said readout gradient values comprises:
determining the maximum readout gradient value as the target readout gradient intensity when the maximum readout gradient value is less than or equal to a fourth threshold value;
When the maximum readout gradient value is greater than the fourth threshold, determining the fourth threshold as the target readout gradient intensity.
In some of these embodiments, determining the target acquisition time for each of the nuclear species from the target readout gradient intensities comprises:
and determining the target acquisition time of each nuclide according to the target readout gradient intensity, the imaging field of view and the acquisition resolution of the nuclide.
In some of these embodiments, the method further comprises:
and determining target repetition time and target echo time according to the sampling parameters of each nuclide, the target radio frequency pulse width and the target acquisition time.
In some of these embodiments, the method further comprises:
iteratively calculating imaging parameters of the nuclide until an iteration cut-off condition is met;
wherein the imaging parameters include: the target slice-selecting gradient strength, a target radio frequency pulse width and target time-bandwidth product of each nuclide, the target readout gradient strength and the target acquisition time of each nuclide.
In some of these embodiments, the iteration cutoff condition includes:
the rate of change of one or more of the imaging parameters after one iteration is less than a fifth threshold;
Alternatively, the number of iterations exceeds a sixth threshold;
alternatively, T of any of the nuclides 2 × The relaxation time constant is smaller than the seventh threshold.
In a second aspect, the present invention provides a multi-core imaging parameter determination apparatus, the apparatus comprising:
the information acquisition module is used for acquiring imaging attributes and sampling parameters of a plurality of nuclides;
the first determining module is used for determining the gradient strength of the target layer selection according to imaging attributes and sampling parameters of a plurality of nuclides;
the second determining module is used for determining the product of the target radio frequency pulse width and the target time bandwidth of each nuclide according to the target layer-selecting gradient strength;
the third determining module is used for determining the target readout gradient strength according to imaging attributes and sampling parameters of a plurality of nuclides;
and a fourth determining module, configured to determine a target acquisition time of each nuclide according to the target readout gradient intensity.
In a third aspect, the present invention provides an electronic device, including a memory, a processor, and a computer program stored on the memory and executable on the processor, where the processor implements the method for determining multi-core imaging parameters according to the first aspect.
In a fourth aspect, the present invention provides a storage medium having stored thereon a computer program which, when executed by a processor, implements the multi-core imaging parameter determination method of the first aspect described above.
In a fifth aspect, the present invention provides a magnetic resonance imaging system, which determines a multi-core imaging parameter by the multi-core imaging parameter determination method described in the first aspect.
Compared with the related art, the multi-core imaging parameter determining method, device and system provided by the invention can determine the multi-core imaging parameters of the multi-core synchronous imaging technology. Firstly, determining the target layer selection gradient strength shared by a plurality of nuclides according to imaging attributes and sampling parameters of the plurality of nuclides, and then determining the respective target radio frequency pulse width and target time bandwidth product of each nuclide based on the target layer selection gradient strength. And determining the target readout gradient intensity common to the plurality of nuclides according to the imaging attributes and the sampling parameters of the plurality of nuclides, and determining the respective target acquisition time of each nuclide based on the target readout gradient intensity. Therefore, the invention provides an effective and feasible multi-core imaging parameter determination method, which solves the problem that the imaging parameter determination method aiming at the multi-nuclear magnetic resonance imaging technology is lacked in the related technology. Specifically, the multi-core imaging parameter determination method overcomes the difficulty that parameter adjustment is inconvenient due to mutual restriction of each nuclide imaging parameter in the multi-core imaging process. The multi-core imaging parameters determined by the multi-core imaging parameter determination method can simultaneously meet the constraint requirements of each nuclide.
The details of one or more embodiments of the application are set forth in the accompanying drawings and the description below to provide a more thorough understanding of the other features, objects, and advantages of the application.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and together with the description serve to explain the application and do not constitute an undue limitation to the application. In the drawings:
FIG. 1 is a block diagram of the hardware architecture of a terminal that performs the multi-core imaging parameter determination method of the present invention;
FIG. 2 is a flow chart of a method of determining multi-core imaging parameters in an embodiment of the invention;
FIG. 3 is a schematic diagram of a multi-core simultaneous imaging sequence involved in a particular embodiment of the invention;
FIG. 4 is a flow chart of a method of determining multi-core imaging parameters in a specific embodiment of the invention;
fig. 5 is a block diagram of the structure of the multi-core imaging parameter determination apparatus in the embodiment of the present invention.
Detailed Description
For a clearer understanding of the objects, technical solutions and advantages of the present application, the present application is described and illustrated below with reference to the accompanying drawings and examples.
Unless defined otherwise, technical or scientific terms used herein shall have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terms "a," "an," "the," "these," and the like in this application are not intended to be limiting in number, but rather are singular or plural. The terms "comprising," "including," "having," and any variations thereof, as used in the present application, are intended to cover a non-exclusive inclusion; for example, a process, method, and system, article, or apparatus that comprises a list of steps or modules (units) is not limited to the list of steps or modules (units), but may include other steps or modules (units) not listed or inherent to such process, method, article, or apparatus. The terms "connected," "coupled," and the like in this application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. Reference to "a plurality" in this application means two or more. "and/or" describes an association relationship of an association object, meaning that there may be three relationships, e.g., "a and/or B" may mean: a exists alone, A and B exist together, and B exists alone. Typically, the character "/" indicates that the associated object is an "or" relationship. The terms "first," "second," "third," and the like, as referred to in this application, merely distinguish similar objects and do not represent a particular ordering of objects.
The method embodiments provided in the present embodiment may be executed in a terminal, a computer, or similar computing device. For example, running on a terminal, fig. 1 is a block diagram of the hardware architecture of a terminal that performs the multi-core imaging parameter determination method of the present invention. As shown in fig. 1, the terminal may include one or more (only one is shown in fig. 1) processors 102 and a memory 104 for storing data, wherein the processors 102 may include, but are not limited to, a microprocessor MCU, a programmable logic device FPGA, or the like. The terminal may also include a transmission device 106 for communication functions and an input-output device 108. It will be appreciated by those skilled in the art that the structure shown in fig. 1 is merely illustrative and is not intended to limit the structure of the terminal. For example, the terminal may also include more or fewer components than shown in fig. 1, or have a different configuration than shown in fig. 1.
The memory 104 may be used to store a computer program, for example, a software program of application software and a module, such as a computer program corresponding to the multi-core imaging parameter determination method in the present invention, and the processor 102 executes the computer program stored in the memory 104 to perform various functional applications and data processing, that is, to implement the above-described method. Memory 104 may include high-speed random access memory, and may also include non-volatile memory, such as one or more magnetic storage devices, flash memory, or other non-volatile solid-state memory. In some examples, the memory 104 may further include memory remotely located relative to the processor 102, which may be connected to the terminal via a network. Examples of such networks include, but are not limited to, the internet, intranets, local area networks, mobile communication networks, and combinations thereof.
The transmission device 106 is used to receive or transmit data via a network. The network includes a wireless network provided by a communication provider of the terminal. In one example, the transmission device 106 includes a network adapter (Network Interface Controller, simply referred to as NIC) that can connect to other network devices through a base station to communicate with the internet. In one example, the transmission device 106 may be a Radio Frequency (RF) module for communicating with the internet wirelessly.
In the present invention, a method for determining a multi-core imaging parameter is provided, and fig. 2 is a flowchart of a method for determining a multi-core imaging parameter in an embodiment of the present invention. As shown in fig. 2, the process includes the steps of:
step S210, obtaining imaging properties and sampling parameters of a plurality of nuclides.
In this step, imaging properties and sampling parameters of at least two nuclides are acquired first. These nuclides may be 1 H、 23 Na、 31 P、 19 F、 129 Xe, etc. The imaging parameters then include T 1 Relaxation time constant, imaging relationship and T 2 × Relaxation time constants, etc. Wherein the imaging relationship refers to the corresponding relationship between the emission voltage and the flip angle, T 2 × The relaxation time constant is the apparent relaxation time constant affected by the magnetic field inhomogeneity. Sampling parameters include imaging field of view (FOV), sampling resolution, and the like. The step is to obtain each T of the nuclide 1 Relaxation time constant, correspondence between emission voltage and flip angle, T 2 × Relaxation time constant, imaging field of view, and sampling resolution.
Step S220, determining the gradient strength of the target selected layer according to the imaging attribute and the sampling parameters of a plurality of nuclides.
In the step, the imaging attribute and the sampling parameter of each nuclide are synthesized to calculate, and the gradient strength of the target selected layer is obtained. The method is mainly aimed at multi-core synchronous imaging, wherein the excitation of a plurality of nuclides in the multi-core synchronous imaging shares the same layer selection gradient, and the target layer selection gradient strength is the strength value of the layer selection gradient shared by a plurality of nuclides.
In some embodiments, step S220 specifically includes:
step S221, determining a layer gradient value of each nuclide according to imaging properties and sampling parameters of the nuclide; step S222, determining the target layer selection gradient strength according to the minimum layer selection gradient value in the plurality of layer selection gradient values.
In this embodiment, the respective slice gradient value of each nuclide is calculated according to the imaging attribute and the sampling parameter of each nuclide, that is, step S221 needs to be performed once for each nuclide. The selected layer gradient value is the selected layer gradient intensity of each nuclide under the corresponding parameters. Because the layer selection gradient strength of each nuclide is different, the layer selection gradient strength of each nuclide needs to be unified, namely the target layer selection gradient strength is determined. In this embodiment, the gradient strength of the target selected layer is determined according to the minimum selected layer gradient value. The specific solution process of the gradient strength of the target selected layer is described as follows.
In one embodiment, step S221 specifically includes:
step S221a, according to the T of the nuclide 1 A relaxation time constant, determining an excitation flip angle of the nuclear species; step S221b, determining a layer gradient value of the nuclide based on the excitation flip angle, the imaging relation and the imaging field of view of the nuclide.
In this embodiment, for each species, first, according to a predetermined setRepetition Time (TR) and T 1 The relaxation time constant determines the excitation Flip Angle (FA) of the species by using the enroute angle. A slice-selective gradient value for the nuclear species is then determined based on the relationship coefficients in the imaging relationship, the excitation flip angle, and the imaging field of view. The specific calculation formula is as follows:
wherein the subscript i of each symbol represents the ith imaging species, G ss,i Layer gradient value, P, for the ith species i Time-bandwidth product, T, of radio frequency pulses representing the ith species i Representing the highest emission voltage or preset voltage threshold, gamma, of the radio frequency emission channel of the ith species i Shows gyromagnetic ratio, SS, of the ith species i Representing the imaging field of view of the ith species in the selective layer direction, alpha i FA as a relationship coefficient of imaging relationship of the ith species i Indicating the flip angle of the ith species. Wherein alpha is i Can be obtained by combining the information of pulse waveform and the like with the voltage calibration in the prior art.
In the iterative calculation embodiment, the time-bandwidth product used in the calculation process of the layer gradient value is the time-bandwidth product obtained by the last calculation. If the layer gradient value is calculated for the first time, the time-bandwidth product can be a preset value.
Further, the expression of the imaging relationship is:
wherein U is i Indicating that the ith species is excited by radio frequency using a pulse width D i The excitation flip angle is FA i A required transmit voltage for the pulse waveform of (a).
In one embodiment, step S222 specifically includes:
step S222a, determining a gradient transformation coefficient, wherein the gradient transformation coefficient is more than 0 and less than or equal to 1; in step S222b, the product of the minimum selected layer gradient value and the gradient transform coefficient is determined as the target selected layer gradient strength.
In this embodiment, after determining the minimum slice-selection gradient value, the value is multiplied by the gradient transform coefficient to obtain the target slice-selection gradient strength value. The gradient transform coefficient is greater than 0 and less than or equal to 1, so that in this embodiment, the gradient transform coefficient can be divided into two cases, namely, directly taking the minimum selected layer gradient value as the target selected layer gradient strength value, and taking the minimum selected layer gradient value as the target selected layer gradient value after shrinking.
Step S230, determining the product of the target radio frequency pulse width and the target time bandwidth of each nuclide according to the target layer-selecting gradient strength.
In the step, after the target layer selection gradient strength is determined, the product of the target radio frequency pulse width and the target time bandwidth of the excitation pulse of each nuclide is determined based on the target layer selection gradient strength. Excitation pulses of different species may have different pulse widths and time-bandwidth products. The process of solving the product of the target radio frequency pulse width and the target time bandwidth is described as follows.
In some of these embodiments, the multi-core imaging parameter determination method further comprises:
step S231, according to a plurality of T 2 × Shortest T in relaxation time constant 2 × The relaxation time constants determine the temporal bandwidth product of each species.
The step S230 specifically includes:
step S232, determining the temporary radio frequency bandwidth of the nuclide according to the gradient strength of the target layer selection and the imaging field of the nuclide for each nuclide; step S233, determining the temporary radio frequency pulse width of the nuclide according to the product of the temporary radio frequency bandwidth and the temporary time bandwidth of each nuclide; step S234, for each nuclide, determining a target time bandwidth and a target radio frequency pulse width of the nuclide according to the temporary time bandwidth and the temporary radio frequency pulse width of the nuclide.
In this embodiment, in the process of solving the product of each target rf pulse width and the target time-bandwidth, on the one hand, it is necessary to determine the temporary time-bandwidth product of each nuclide. On the other hand, the temporary radio frequency bandwidth of each species needs to be determined according to the target layer-selection gradient strength.
The determination of the temporal bandwidth product of each species is based on a factor of T 2 × Relaxation time constant. Further specifically, T is a plurality of nuclides 2 × Shortest T in relaxation time constant 2 × The relaxation time constant is compared to a first threshold and a second threshold. Illustratively, the first and second thresholds may be set to 5ms and 10ms, respectively. When the shortest T 2 × When the relaxation time constant is smaller than or equal to a first threshold value, determining a first preset value as a temporary time-bandwidth product of each nuclide, wherein each nuclide has the same temporary time-bandwidth product, namely the first preset value; when the shortest T 2 × When the relaxation time constant is greater than the first threshold and less than or equal to the second threshold, determining a second preset value corresponding to each nuclide as a respective temporary time-bandwidth product, and enabling each nuclide to adopt an asymmetric radio frequency waveform to shorten the pulse width. Illustratively, the first preset value may be set to 4, the second preset value may be set to 4, 5, 6, etc. When the shortest T 2 × When the relaxation time constant is greater than the second threshold, then the time-bandwidth product of each species is not transformed. In the iterative calculation process, the time-bandwidth product of each nuclide obtained by the previous calculation is directly used as the temporary time-bandwidth product of each nuclide in the current calculation process. At this time, each nuclide may have a different temporary time-bandwidth product, and the respective temporary time-bandwidth product is a second preset value corresponding to each other.
The calculation formula of the temporary radio frequency bandwidth of each nuclide is as follows:
wherein BW is i Representing the radio frequency bandwidth of the ith species, G ss Gradient intensity of layer for target selection, gamma i Is the gyromagnetic ratio of the ith nuclide, SS i An imaging field of view of the ith species in the selected layer direction.
And then obtaining respective temporary radio frequency pulse widths by the product of the temporary radio frequency bandwidth and the temporary time bandwidth of each nuclide based on a relational expression among the bandwidths, the pulse widths and the time bandwidth products. The calculation relation is as follows:
wherein W is i The radio frequency pulse width of the ith nuclide, P i Time-bandwidth product, BW, for the ith species i Is the radio frequency bandwidth of the ith species.
After the temporary radio frequency pulse width and the temporary time bandwidth product of each nuclide are determined, the temporary radio frequency pulse width and the temporary time bandwidth product of each nuclide are also required to be adjusted, and finally the target radio frequency pulse width and the target time bandwidth product of each nuclide are obtained.
Thus, in one embodiment, step S234 specifically includes:
step S234a, determining the maximum temporary radio frequency pulse width in a plurality of temporary radio frequency pulse widths; step S234b, when the nuclide meets the update condition, increasing the temporary time-bandwidth product of the nuclide by a unit value, and updating the temporary radio frequency pulse width of the nuclide; wherein the update condition includes: the quotient of the product of the temporary time bandwidth of the nuclide and the temporary radio frequency bandwidth is smaller than or equal to the maximum temporary radio frequency pulse width after the product of the temporary time bandwidth of the nuclide is increased by a unit value; in step S234c, the temporary time bandwidth and the temporary rf pulse width of the updated nuclide are respectively determined as the target time bandwidth and the target rf pulse width of the nuclide.
In this embodiment, the maximum temporary radio frequency pulse width is determined from the temporary radio frequency pulse widths of a plurality of nuclides, then the temporary time-bandwidth product of each nuclide is analyzed and judged in sequence, and when the quotient between the temporary time-bandwidth product of a certain nuclide and the temporary radio frequency bandwidth is smaller than or equal to the maximum temporary radio frequency pulse width after the temporary time-bandwidth product of the certain nuclide is increased by a unit value 1, the temporary time-bandwidth product of the nuclide is increased by a unit value 1, and the temporary radio frequency pulse width is correspondingly increased. Until all nuclides do not meet the update condition. It should be noted that, the quotient of the time bandwidth product and the rf bandwidth is the rf pulse width, so this step essentially increases the temporary time bandwidth product and the temporary rf pulse width of each nuclide as much as possible, but the temporary rf pulse width of each nuclide cannot exceed the maximum temporary rf pulse width.
Step S240, determining the target readout gradient strength according to imaging properties and sampling parameters of a plurality of nuclides.
In the step, the imaging attribute and the sampling parameter of each nuclide are synthesized to calculate, and the target readout gradient strength is obtained. The method is mainly aimed at multi-core synchronous imaging, wherein a plurality of nuclides in multi-core synchronous imaging share the same readout gradient, and the target readout gradient strength is the strength value of the readout gradient shared by a plurality of nuclides.
In some embodiments, step S240 specifically includes:
step S241, determining a readout gradient value of the nuclide according to the imaging parameter and the sampling parameter of the nuclide for each nuclide respectively; step S242, determining the target readout gradient intensity according to the maximum readout gradient value of the plurality of readout gradient values.
In this embodiment, the respective readout gradient value of each nuclide is calculated according to the respective imaging attribute and sampling parameter of each nuclide, that is, step S241 needs to be performed once for each nuclide. The readout gradient value is then the readout gradient intensity of each species under the corresponding parameters. Since the readout gradient intensities of the respective nuclides are different, it is necessary to unify the readout gradient intensities of the respective nuclides, that is, to determine the target readout gradient intensity. The target readout gradient strength is determined from the maximum readout gradient value in this embodiment. The specific solving process of the target readout gradient strength is explained as follows.
In one embodiment, step S240 specifically further includes:
step S243, according to several T 2 × Shortest T in the relaxation time constant 2 × The relaxation time constant determines the maximum acquisition time.
The step S241 specifically includes:
in step S241a, the readout gradient value of the nuclide is determined according to the maximum acquisition time, the sampling resolution of the nuclide, and the imaging field of view.
This practice isIn an embodiment, T from several species is also required before determining the readout gradient value for each species 2 × Shortest T in the relaxation time constant 2 × The relaxation time constant determines the maximum acquisition time, which refers to the maximum of the acquisition times of several species. After the maximum acquisition time is determined, the readout gradient value of each nuclide is determined according to the maximum acquisition time, the respective sampling resolution of each nuclide and the imaging field of view. The specific calculation formula of the readout gradient value is as follows:
wherein R is i Indicating the resolution of the ith species in the readout direction, gamma i Gyromagnetic ratio, RO, of the ith species i For the imaging field of view of the ith species in the readout direction, S is the maximum acquisition time, G RO,i The readout gradient value for the ith species.
Further, the step S243 specifically includes:
Step S243a, when the shortest T 2 × When the relaxation time constant is less than or equal to the third threshold value, the shortest T is 2 × The relaxation time constant is determined as the maximum acquisition time; step S243b, when the shortest T 2 × And when the relaxation time constant is larger than a third threshold value, determining a third preset value as the maximum acquisition time.
In this embodiment, a specific step of determining the maximum acquisition time is provided, in which the shortest T is first determined 2 × The relaxation time constant is related to the magnitude of the third threshold. The third threshold may be set to 5ms or 10ms, for example. When the shortest T 2 × When the relaxation time constant is less than or equal to the third threshold value, the shortest T is directly adopted 2 × Relaxation time constant as maximum acquisition time, when T is shortest 2 × And when the relaxation time constant is larger than the third threshold value, the third threshold value is used as the maximum acquisition time. The maximum acquisition time is understood to be the maximum of the acquisition times of all nuclides.
Further, step S242 specifically includes:
step S242a, determining the maximum readout gradient value as the target readout gradient intensity when the maximum readout gradient value is less than or equal to the fourth threshold value; in step S242b, when the maximum readout gradient value is greater than the fourth threshold value, the fourth threshold value is determined as the target readout gradient intensity.
In this embodiment, a specific step of determining the target readout gradient strength is provided, where the relationship between the maximum readout gradient value and the fourth threshold value needs to be determined first. The fourth threshold may be set to 70mT/m, for example. And when the maximum readout gradient value is smaller than or equal to the fourth threshold value, the maximum readout gradient value is directly taken as the target readout gradient intensity, and when the maximum readout gradient value is larger than the fourth threshold value, the fourth threshold value is taken as the target readout gradient value.
Step S250, determining the target acquisition time of each nuclide according to the target readout gradient intensity.
In the step, after the target readout gradient intensity is determined, the target acquisition time of each nuclide is determined by combining the target readout gradient intensity with the respective sampling resolution and imaging field of each nuclide. Different nuclides have different acquisition times. The specific calculation formula of the target acquisition time is as follows:
wherein R is i Indicating the resolution of the ith species in the readout direction, gamma i Gyromagnetic ratio of ith nuclide, G RO For target readout gradient intensity, RO i For the imaging field of view of the ith species in the readout direction, S i Target acquisition time for the ith species.
Through the steps, the multi-core imaging parameters of the multi-core synchronous imaging technology can be determined. Firstly, determining the target layer selection gradient strength shared by a plurality of nuclides according to imaging attributes and sampling parameters of the plurality of nuclides, and then determining the respective target radio frequency pulse width and target time bandwidth product of each nuclide based on the target layer selection gradient strength. And determining the target readout gradient intensity common to the plurality of nuclides according to the imaging attributes and the sampling parameters of the plurality of nuclides, and determining the respective target acquisition time of each nuclide based on the target readout gradient intensity.
Therefore, the invention provides an effective and feasible multi-core imaging determination method, which solves the problem that the related art lacks an imaging parameter determination method aiming at the multi-nuclear magnetic resonance imaging technology.
In some of these embodiments, the multi-core imaging parameter determination method further comprises:
step S260, determining target repetition time and target echo time according to the sampling parameters of each nuclide, the target radio frequency pulse width and the target acquisition time.
In this embodiment, after determining the target slice-selection gradient strength, the target rf pulse width and target time-bandwidth product of each species, the target readout gradient strength, and the target acquisition time of each species, the target echo time and the target repetition time are also determined.
In some of these embodiments, the multi-core imaging parameter determination method further comprises:
step S270, iteratively calculating imaging parameters of nuclides until the iteration cut-off condition is met; wherein the imaging parameters include: the target layer-selecting gradient strength, the product of the target radio frequency pulse width and the target time bandwidth of each nuclide, the target reading gradient strength and the target acquisition time of each nuclide.
In this embodiment, the imaging parameters such as the target slice-selecting gradient strength, the product of the target rf pulse width and the target time-bandwidth of each nuclide, the target readout gradient strength, and the target acquisition time of each nuclide are also iteratively calculated, that is, the partial result of the last calculation is used as the partial input of the next calculation, so as to continuously update the imaging parameters.
The calculation formula of the layer selection gradient value shows that the layer selection gradient value is related to the time bandwidth product, and then the target time bandwidth product of each nuclide obtained by the previous generation calculation is used as the input of the next generation calculation and is used for updating and calculating the layer selection gradient value of each nuclide, and further updating the target layer selection gradient strength; and after the gradient strength of the target layer selection is changed, continuously updating and calculating the product of the target radio frequency pulse width and the target time bandwidth of each nuclide. From the above description, the gradient strength of the target selected layer is related to the product of the target RF pulse width and the target time-bandwidth of each nuclide. Therefore, the product of the gradient strength of the target layer selection and the target radio frequency pulse width and the target time bandwidth of each nuclide can be continuously adjusted and updated through iterative calculation.
Similarly, the target readout gradient intensity and the target acquisition time of each species are also interrelated. Specifically, the target readout gradient intensity is determined according to the maximum acquisition time of the target acquisition times of the nuclides, and the target acquisition time of the nuclides is determined according to the target readout gradient intensity. Therefore, the target readout gradient intensity and the target acquisition time of each nuclide can be continuously adjusted and updated through iterative calculation.
Further, the iteration cutoff condition includes:
1. the rate of change of the one or more imaging parameters after one iteration is less than a fifth threshold;
2. the number of iterations exceeds a sixth threshold;
3. t of any nuclide 2 × The relaxation time constant is smaller than the seventh threshold.
Specifically, the iteration cut-off condition includes the three above-mentioned items, and when one of the iteration conditions is satisfied, the iteration can be terminated. Of these, for example, the fifth threshold may be set to 20%, the sixth threshold may be set to 3 times, and the seventh threshold may be set to 5ms.
In some of these optional embodiments, the multi-core imaging parameter determination method further comprises:
before acquiring imaging properties and sampling parameters of a plurality of nuclides, performing frequency calibration operation on each nuclide, and performing magnetic field shimming operation on a certain nuclide.
The technical scheme of the invention is described below through a complete specific embodiment.
FIG. 3 is a schematic diagram of a multi-core simultaneous imaging sequence involved in a specific embodiment of the present invention. Referring to fig. 3, in this example sequence, N different species (only two are shown) are included, which collectively use the same combination of gradients, ensuring that the equivalent center of the radio frequency waveform and the acquisition center are each aligned with the intended center of the gradient. In the figure, the time-bandwidth products of the excitation pulses of nuclide 1 and nuclide N are not equal, and each numerical label is a label for conveniently describing the action of each time period. The imaging parameters mainly determined in this embodiment are: target layer selection gradient intensity, target readout gradient intensity, target radio frequency pulse width and target time bandwidth product of each nuclide excitation pulse, and target sampling time. After the parameters are determined, the time consumption of each module can be calculated by combining the gradient climbing rate and other information of the system, and finally the shortest target repetition time and the shortest target echo time allowed by the guaranteed gradient are selected.
FIG. 4 is a flow chart of a method of determining multi-core imaging parameters in a specific embodiment of the invention. Referring to fig. 4, in one particular embodiment, a multi-core imaging parameter determination method includes:
in step S410, main magnetic resonance imaging properties and sampling parameters of a plurality of nuclides in a target sample are acquired for determining imaging parameters.
Specifically, the imaging properties include: t (T) 1 Relaxation time constant, correspondence between emission voltage and flip angle (imaging relationship), T 2 × A relaxation time constant; the sampling parameters include: the imaging field of view of each imaging species used, the sampling resolution of each imaging species used.
Step S420, determining the gradient strength of the target selected layer.
Specifically, the gradient value of each layer selection of nuclides is calculated respectively, the minimum value in the gradient value of each layer selection is taken, and the value or the value multiplied by a coefficient between 0 and 1 is taken as the gradient strength of the target layer selection. The calculation formula of the layer gradient value is as follows:
wherein the subscript i of each symbol represents the ith imaging species, G ss,i Layer gradient value, P, for the ith species i Representation ofTime-bandwidth product, T, of the RF pulse of the ith species i Representing the highest emission voltage or preset voltage threshold, gamma, of the radio frequency emission channel of the ith species i Shows gyromagnetic ratio, SS, of the ith species i Representing the imaging field of view of the ith species in the selective layer direction, alpha i FA as a relationship coefficient of imaging relationship of the ith species i Indicating the flip angle of the ith species. Wherein alpha is i Can be obtained by combining the information of pulse waveform and the like with the voltage calibration in the prior art.
Further, the expression of the imaging relationship is:
wherein U is i Indicating that the ith species is excited by radio frequency using a pulse width D i The excitation flip angle is FA i A required transmit voltage for the pulse waveform of (a).
An example of the calculation of the gradient strength of the target selected layer based on two sets of nuclides is given below as shown in table 1:
table 1 exemplary table of calculation of gradient strength for target selected layers
Step S430, determining the target RF pulse width of each species.
Specifically, the radio frequency bandwidth of each nuclide is calculated respectively, when the shortest T 2 × When the time bandwidth of the radio frequency waveform of each nuclide is smaller than or equal to a first threshold value, the time bandwidth product of the radio frequency waveform of each nuclide is set to be a first preset value; when T is shortest 2 × And when the time bandwidth of the radio frequency waveform of each nuclide is smaller than or equal to the second threshold value and larger than the first threshold value, integrating the time bandwidth of the radio frequency waveform of each nuclide to be a second preset value. The preset value is a dimensionless number and has no units. The calculation formula of the radio frequency bandwidth is as follows:
wherein the method comprises the steps of，BW i Representing the radio frequency bandwidth of the ith species, G ss Selecting gradient intensity gamma for the target layer obtained in the previous step i Is the gyromagnetic ratio of the ith nuclide, SS i An imaging field of view of the ith species in the selected layer direction.
An example of the calculation of the radio frequency bandwidth for two sets of species is shown below in table 2:
table 2 example table of calculation of radio frequency bandwidth
The formula for calculating the pulse width from the time-bandwidth product and the radio frequency bandwidth is:
wherein W is i The radio frequency pulse width of the ith nuclide, P i Time-bandwidth product, BW, for the ith species i Is the radio frequency bandwidth of the ith species.
Examples of the calculation of the radio frequency pulse widths for two sets of species are given below, as shown in tables 3 and 4:
table 3 example of calculation of rf pulse width table 1
Table 4 calculation example of rf pulse width table two
Wherein, when the time bandwidth product is odd, an asymmetric radio frequency waveform is adopted.
After the radio frequency pulse width of each nuclide is determined, traversing all imaging nuclides, and if the quotient of the next adjacent integer of the current time bandwidth product of a certain nuclide and the radio frequency bandwidth is smaller than or equal to the maximum pulse width of each nuclide, increasing the time bandwidth product by 1 and rechecking the condition until all the conditions are not met. After the time-bandwidth product is adjusted, the radio frequency pulse width of each nuclide is determined according to a calculation formula, and the target radio frequency pulse width of each nuclide is obtained.
Examples of adjustments of pulse widths for two sets of species are given below, as shown in table 5:
table 5 example table of adjustments to rf pulse width
Wherein, the liquid crystal display device comprises a liquid crystal display device, 1 the radio frequency bandwidth of H is 24.2kHz, 19 the radio frequency bandwidth of F is 22.8kHz.
Step S440, determining the target readout gradient strength and the target sampling time of each species.
Specifically, when the shortest T in each species 2 × When the maximum total sampling time is less than or equal to a third threshold value, tentatively setting the maximum total sampling time as T 2 × The method comprises the steps of carrying out a first treatment on the surface of the When T is shortest 2 × And when the maximum total sampling time is larger than or equal to a third threshold value, the maximum total sampling time is tentatively set to be a third preset value. Respectively calculating the readout gradient value of each nuclide, taking the maximum value in each nuclide, and taking the value as the target readout gradient intensity; if the value is greater than the fourth threshold, the fourth threshold is used as the target readout gradient strength. After the read gradient strength is determined, the total sampling time of each nuclide is determined according to a formula.
The calculation formula of the readout gradient value is as follows:
wherein R is i Indicating the resolution of the ith species in the readout direction, gamma i Gyromagnetic ratio, RO, of the ith species i For the imaging field of view of the ith species in the readout direction, S is the maximum sampling time, G RO,i The readout gradient value for the ith species.
Two examples of calculations of readout gradient values for two sets of species are given below, as shown in tables 6 and 7:
Table 6 calculation example of readout gradient values table 1
Table 7 calculation example of readout gradient values table two
The formula for calculating the total sampling time from the readout gradient strength is:
wherein R is i Indicating the resolution of the ith species in the readout direction, gamma i Gyromagnetic ratio of ith nuclide, G RO For target readout gradient intensity, RO i For the imaging field of view of the ith species in the readout direction, S i Is the target sampling time for the ith species.
Step S450, determining target repetition Time (TR) and target echo Time (TE) according to the target radio frequency pulse width of each nuclide, gyromagnetic ratio and imaging field of view of each nuclide, target sampling time of each nuclide and gradient system performance.
Specifically, the main calculation formula is as follows:
referring to FIG. 3, time D 1 And D 2 Layer selection gradient and disturbance phase gradient calculation based on layer selection gradient axes respectively, and time D 3 And D 4 D, calculating phase encoding gradient and disturbance gradient based on phase encoding gradient axes respectively 5 And D 6 The readout gradient and the disturbance gradient are calculated based on the readout gradient axis, respectively. SR represents the gradient climbing rate of each gradient axis, G + And G - Respectively representing the positive polarity intensity and the negative polarity intensity of each gradient, D - And D + The plateau times for each gradient at negative and positive polarity are shown, respectively. T (T) RF Each radio frequency pulseThe time interval from the equivalent center to the end of the last RF pulse, S max For the longest sampling time in each species.
And iteratively calculating the gradient intensity of the target selected layer and the gradient intensity of the target read-out, and the product of the target radio frequency pulse width and the target time bandwidth and the target sampling time of each nuclide excitation pulse.
Specifically, the iteration cutoff conditions include:
1. the rate of change of the one or more imaging parameters after one iteration is less than a fifth threshold;
2. the number of iterations exceeds a sixth threshold;
3. t of any nuclide 2 × The relaxation time constant is smaller than the seventh threshold.
Specifically, the iteration cut-off condition includes the three above-mentioned items, and when one of the iteration conditions is satisfied, the iteration can be terminated. Of these, for example, the fifth threshold may be set to 20%, the sixth threshold may be set to 3 times, and the seventh threshold may be set to 5ms.
The embodiment also provides a multi-core imaging parameter determining device, which is used for implementing the above embodiment and the preferred implementation manner, and is not described in detail. The terms "module," "unit," "sub-unit," and the like as used below may refer to a combination of software and/or hardware that performs a predetermined function. While the means described in the following embodiments are preferably implemented in software, implementations in hardware, or a combination of software and hardware, are also possible and contemplated.
Fig. 5 is a block diagram of a multi-core imaging parameter determination apparatus according to an embodiment of the present invention, as shown in fig. 5, the apparatus includes:
the information acquisition module 510 is configured to acquire imaging attributes and sampling parameters of a plurality of nuclides;
a first determining module 520, configured to determine a target slice-selection gradient strength according to imaging properties and sampling parameters of a plurality of nuclides;
a second determining module 530, configured to determine a product of the target rf pulse width and the target time-bandwidth for each species according to the target slice-selection gradient strength;
a third determining module 540, configured to determine a target readout gradient strength according to imaging properties and sampling parameters of a plurality of nuclides;
a fourth determination module 550 is configured to determine a target acquisition time for each species based on the target readout gradient strength.
Through the module, the multi-core imaging parameters of the multi-core synchronous imaging technology can be determined. Firstly, determining the target layer selection gradient strength shared by a plurality of nuclides according to imaging attributes and sampling parameters of the plurality of nuclides, and then determining the respective target radio frequency pulse width and target time bandwidth product of each nuclide based on the target layer selection gradient strength. And determining the target readout gradient intensity common to the plurality of nuclides according to the imaging attributes and the sampling parameters of the plurality of nuclides, and determining the respective target acquisition time of each nuclide based on the target readout gradient intensity.
The above-described respective modules may be functional modules or program modules, and may be implemented by software or hardware. For modules implemented in hardware, the various modules described above may be located in the same processor; or the above modules may be located in different processors in any combination.
There is also provided in this embodiment an electronic device comprising a memory having stored therein a computer program and a processor arranged to run the computer program to perform the steps of any of the method embodiments described above.
It should be noted that, specific examples in this embodiment may refer to examples described in the foregoing embodiments and alternative implementations, and are not described in detail in this embodiment.
In addition, in combination with the multi-core imaging parameter determining method provided in the above embodiment, a storage medium may be further provided in this embodiment to implement. The storage medium has a computer program stored thereon; the computer program, when executed by a processor, implements any of the multi-core imaging parameter determination methods of the above embodiments.
It should be noted that, user information (including but not limited to user equipment information, user personal information, etc.) and data (including but not limited to data for analysis, stored data, presented data, etc.) referred to in the present application are information and data authorized by the user or sufficiently authorized by each party.
It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to be limiting. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present application, are within the scope of the present application in light of the embodiments provided herein.
It is evident that the drawings are only examples or embodiments of the present application, from which the present application can also be adapted to other similar situations by a person skilled in the art without the inventive effort. In addition, it should be appreciated that while the development effort might be complex and lengthy, it would nevertheless be a routine undertaking of design, fabrication, or manufacture for those of ordinary skill having the benefit of this disclosure, and thus should not be construed as an admission of insufficient detail.
The term "embodiment" in this application means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive. It will be clear or implicitly understood by those of ordinary skill in the art that the embodiments described in this application can be combined with other embodiments without conflict.
The above examples only represent a few embodiments of the present application, which are described in more detail and are not to be construed as limiting the scope of the patent. It should be noted that it would be apparent to those skilled in the art that various modifications and improvements could be made without departing from the spirit of the present application, which would be within the scope of the present application. Accordingly, the scope of protection of the present application shall be subject to the appended claims.
Claims (16)
1. A method for determining multi-core imaging parameters, the method comprising:
acquiring imaging attributes and sampling parameters of a plurality of nuclides;
determining the gradient strength of a target layer selection according to imaging attributes and sampling parameters of a plurality of nuclides;
determining a target radio frequency pulse width and a target time bandwidth product of each nuclide according to the target layer-selecting gradient strength;
determining target readout gradient strength according to imaging properties and sampling parameters of a plurality of nuclides;
and determining the target acquisition time of each nuclide according to the target readout gradient intensity.
2. The method of claim 1, wherein determining a target slice-select gradient strength based on the imaging properties and the sampling parameters comprises:
Determining a layer selection gradient value of each nuclide according to imaging attributes and sampling parameters of the nuclide;
and determining the target layer selection gradient strength according to the minimum layer selection gradient value in the layer selection gradient values.
3. The multi-core imaging parameter determination method of claim 2, wherein the imaging attribute comprises: t (T) 1 Relaxation time constant and imaging relation, wherein the imaging relation is the corresponding relation between radio frequency emission voltage and excitation flip angle;
the sampling parameters include: an imaging field of view;
the determining the slice-selecting gradient value of the nuclide according to the imaging parameter and the sampling parameter of the nuclide comprises:
t according to the nuclide 1 Determining the excitation flip angle of the nuclear species；
A slice-selective gradient value of the nuclear species is determined based on the excitation flip angle, imaging relationship, and imaging field of view of the nuclear species.
4. The method of determining a multi-core imaging parameter of claim 2, wherein determining the target slice-selection gradient strength from a minimum slice-selection gradient value of the plurality of slice-selection gradient values comprises:
determining a gradient transform coefficient, the gradient transform coefficient being greater than 0 and less than or equal to 1;
And determining the product of the minimum selected layer gradient value and the gradient transformation coefficient as the target selected layer gradient strength.
5. The multi-core imaging parameter determination method of claim 1, wherein the imaging attribute comprises: t (T) 2 × A relaxation time constant; the sampling parameters include: an imaging field of view;
the method further comprises the steps of:
according to a plurality of said T 2 × Shortest T in relaxation time constant 2 × A relaxation time constant, determining a temporary time-bandwidth product for each of said species;
the determining the product of the target radio frequency pulse width and the target time bandwidth of each nuclide according to the target layer-selecting gradient strength comprises:
determining a temporary radio frequency bandwidth of each nuclide according to the target layer-selecting gradient strength and the imaging field of view of the nuclide;
determining a temporary radio frequency pulse width of each nuclide according to the product of the temporary radio frequency bandwidth and the temporary time bandwidth of the nuclide;
and respectively aiming at each nuclide, and determining the target time bandwidth and the target radio frequency pulse width of the nuclide according to the temporary time bandwidth and the temporary radio frequency pulse width of the nuclide.
6. According to claim The method for determining multi-core imaging parameters according to 5, wherein said determining step comprises determining the plurality of said T' s 2 × Shortest T in relaxation time constant 2 × Determining the temporal bandwidth product of each of the nuclides includes:
when the shortest T 2 × Determining a first preset value as a temporary time-bandwidth product for each of the species when the relaxation time constant is less than or equal to a first threshold;
when the shortest T 2 × And when the relaxation time constant is larger than the first threshold and smaller than or equal to a second threshold, determining a second preset value corresponding to each nuclide as a respective temporary time-bandwidth product.
7. The method of claim 5, wherein determining the target time bandwidth and the target radio frequency pulse width for the nuclear species based on the temporary time bandwidth and the temporary radio frequency pulse width for the nuclear species comprises:
determining the maximum temporary radio frequency pulse width in a plurality of temporary radio frequency pulse widths;
when the nuclide meets the updating condition, increasing the temporary time-bandwidth product of the nuclide by a unit value, and updating the temporary radio frequency pulse width of the nuclide; wherein the update condition includes: the quotient of the product of the temporary time bandwidth of the nuclide and the temporary radio frequency bandwidth is smaller than or equal to the maximum temporary radio frequency pulse width after the product of the temporary time bandwidth of the nuclide is increased by a unit value;
And respectively determining the updated temporary time bandwidth and the temporary radio frequency pulse width of the nuclide as the target time bandwidth and the target radio frequency pulse width of the nuclide.
8. The method of claim 1, wherein determining the target readout gradient strength based on imaging properties and sampling parameters of a number of the nuclear species comprises:
for each nuclide, determining a readout gradient value of the nuclide according to imaging parameters and sampling parameters of the nuclide;
and determining the target readout gradient intensity according to the maximum readout gradient value in the plurality of readout gradient values.
9. The multi-core imaging parameter determination method of claim 8, wherein the imaging attribute comprises: t (T) 2 × A relaxation time constant; the sampling parameters include: imaging field of view and sampling resolution;
the determining the target readout gradient strength according to the imaging properties and sampling parameters of the plurality of nuclides further comprises:
according to a plurality of said T 2 × Shortest T in the relaxation time constant 2 × A relaxation time constant, determining a maximum acquisition time;
the determining the readout gradient value of the nuclear species according to the imaging parameter and the sampling parameter of the nuclear species comprises:
And determining a readout gradient value of the nuclide according to the maximum acquisition time, the sampling resolution of the nuclide and the imaging field of view.
10. The method of determining multi-core imaging parameters according to claim 9, wherein the T is based on a plurality of the T' s 2 × Shortest T in relaxation time constant 2 × The relaxation time constant, determining the maximum acquisition time comprises:
when the shortest T 2 × When the relaxation time constant is less than or equal to a third threshold value, the shortest T is set 2 × A relaxation time constant is determined as the maximum acquisition time;
when the shortest T 2 × And when the relaxation time constant is larger than the third threshold value, determining a third preset value as the maximum acquisition time.
11. The method of multi-core imaging parameter determination of claim 8, wherein determining the target readout gradient intensity from a maximum readout gradient value of a number of the readout gradient values comprises:
determining the maximum readout gradient value as the target readout gradient intensity when the maximum readout gradient value is less than or equal to a fourth threshold value;
when the maximum readout gradient value is greater than the fourth threshold, determining the fourth threshold as the target readout gradient intensity.
12. The method of claim 1, wherein determining a target acquisition time for each of the nuclear species from the target readout gradient intensities comprises:
and determining the target acquisition time of each nuclide according to the target readout gradient intensity, the imaging field of view and the acquisition resolution of the nuclide.
13. The method of multi-core imaging parameter determination according to claim 1, further comprising:
and determining target repetition time and target echo time according to the sampling parameters of each nuclide, the target radio frequency pulse width and the target acquisition time.
14. A multi-core imaging parameter determination apparatus, the apparatus comprising:
the information acquisition module is used for acquiring imaging attributes and sampling parameters of a plurality of nuclides;
the first determining module is used for determining the gradient strength of the target layer selection according to imaging attributes and sampling parameters of a plurality of nuclides;
the second determining module is used for determining the product of the target radio frequency pulse width and the target time bandwidth of each nuclide according to the target layer-selecting gradient strength;
the third determining module is used for determining the target readout gradient strength according to imaging attributes and sampling parameters of a plurality of nuclides;
And a fourth determining module, configured to determine a target acquisition time of each nuclide according to the target readout gradient intensity.
15. A magnetic resonance imaging system, characterized in that the system determines multi-nuclei imaging parameters by the multi-nuclei imaging parameter determination method of any one of claims 1-13.
16. A computer readable storage medium having stored thereon a computer program, characterized in that the computer program when executed by a processor implements the steps of the multi-core imaging parameter determination method of any of claims 1 to 13.
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