CN113759298B

CN113759298B - Scanning protocol parameter determination method and magnetic resonance system

Info

Publication number: CN113759298B
Application number: CN202010504086.7A
Authority: CN
Inventors: 刘双双; 贾二维; 周晓东
Original assignee: Shanghai United Imaging Healthcare Co Ltd
Current assignee: Shanghai United Imaging Healthcare Co Ltd
Priority date: 2020-06-04
Filing date: 2020-06-04
Publication date: 2023-07-07
Anticipated expiration: 2040-06-04
Also published as: CN113759298A

Abstract

The embodiment of the invention discloses a scanning protocol parameter determining method and a magnetic resonance system, wherein the method comprises the following steps: setting scanning protocol parameters, wherein the scanning protocol parameters are used for exciting one or more slices of a target object, and the scanning protocol parameters comprise a layer selection gradient, a phase encoding gradient and a frequency encoding gradient; updating the scanning protocol parameters when the scanning protocol parameters are detected so that a target object has PNS overrun slices to be scanned in the magnetic resonance data acquisition process, wherein the updating method of the scanning protocol parameters comprises the steps of determining the application direction of one or more of a slice selection gradient, a phase encoding gradient and a frequency encoding gradient based on a golden ratio algorithm; and performing magnetic resonance imaging on the target object according to the updated scanning protocol parameters. The method solves the problems of time and labor waste in the modification of scanning protocol parameters in the magnetic resonance scanning method in the prior art.

Description

Scanning protocol parameter determination method and magnetic resonance system

Technical Field

The embodiment of the invention relates to the field of medical equipment control, in particular to a scanning protocol parameter determining method and a magnetic resonance system.

Background

In general, magnetic resonance is safe for the subject, but due to the increasing magnetic field strength and the emerging new technologies, the biological effects and safety issues of MRI remain to be ignored, especially with respect to system hardware (e.g., high magnetic fields 5T, 7T, etc.).

The high gradient strength and switching rate can cause the magnetic flux density in the scanning cavity to change greatly in a short time, the generated induced electric field can excite peripheral nerves to generate peripheral nerve stimulation (Peripheral Nervous Stimulate, PNS for short), and if the induced electric field reaches a certain degree, people feel uncomfortable or obvious pain, and even life is possibly threatened, so that the magnetic field gradient is monitored. The relationship of PNS threshold to cumulative duration is described in IEC60601-2-332002 and 2010 standards by detecting the induced electric field (also dB/dt) in the subject caused by a varying gradient magnetic field. Before the magnetic resonance clinical scanning, an operator can modify scanning protocol parameters according to actual conditions, and if the parameters are improperly modified, the magnetic field gradient climbing rate in a scanning cavity is out of limit, so that the condition that the primary mode of PNS safety inspection is out of limit and scanning cannot be performed occurs. Currently, after this situation occurs, an operator is usually required to reset the scanning protocol parameters of the PNS overrun slice to be scanned according to experience, and then start PNS security check again until PNS overrun does not occur in all slices to be scanned.

In summary, for high magnetic fields, the magnetic resonance scanning method in the prior art has the problem that the modification of scanning protocol parameters is time-consuming and labor-consuming.

Disclosure of Invention

The embodiment of the invention provides a scanning protocol parameter determining method and a magnetic resonance system, which solve the problems of time and labor waste in the modification of scanning protocol parameters in the magnetic resonance scanning method in the prior art.

In a first aspect, an embodiment of the present invention provides a method for determining a scan protocol parameter, including:

setting scanning protocol parameters, wherein the scanning protocol parameters are used for exciting one or more slices of a target object, and the scanning protocol parameters comprise a layer selection gradient, a phase encoding gradient and a frequency encoding gradient;

updating the scanning protocol parameters when the scanning protocol parameters are detected so that a target object has PNS overrun slices to be scanned in the magnetic resonance data acquisition process, wherein the updating method of the scanning protocol parameters comprises the steps of determining the application direction of one or more of a slice selection gradient, a phase encoding gradient and a frequency encoding gradient based on a golden ratio algorithm;

and performing magnetic resonance imaging on the target object according to the updated scanning protocol parameters.

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

The radio frequency transmitting coil is used for transmitting radio frequency pulses to a scanning part of a target object so as to excite nuclear spins of the scanning part;

gradient coils for applying slice selection gradient fields, phase encoding gradient fields, and frequency encoding gradient fields to the scan site to generate echo signals;

a radio frequency receiving coil for receiving the echo signals to form magnetic resonance scan data;

a controller for receiving set scan protocol parameters for exciting one or more slices of a target object, the scan protocol parameters including a slice selection gradient, a phase encoding gradient, and a frequency encoding gradient; updating the scanning protocol parameters when the scanning protocol parameters show that the target object has PNS overrun slices to be scanned in the magnetic resonance data acquisition process, wherein the updating method of the scanning protocol parameters comprises the steps of determining the application direction of one or more of a slice selection gradient, a phase encoding gradient and a frequency encoding gradient based on a golden ratio algorithm; the updated scan protocol parameters are used to acquire magnetic resonance data of the target object.

According to the technical scheme of the scanning protocol parameter determining method provided by the embodiment of the invention, if the set scanning protocol parameter enables a target object to have PNS overrun slice to be scanned in the magnetic resonance data acquisition process, the scanning protocol parameter is updated, and the scanning protocol parameter updating method comprises the step of determining the application directions of a slice selection gradient, a phase encoding gradient and a frequency encoding gradient based on a golden ratio algorithm. Because the golden ratio algorithm can give a dense and uniformly distributed normal vector distribution diagram, the normal vector of the gradient field of the slice to be scanned, which is determined according to the golden ratio algorithm, can not only solve the problem of PNS overrun, but also make the included angle between the updated normal vector of the gradient field of the slice to be scanned and the original normal vector smaller, and the smaller included angle of the normal vector corresponds to shorter gradient field forming time, and the automatic updating of the scanning protocol parameters is helpful for reducing the time spent by an operator for modifying the scanning protocol parameters, so that the magnetic resonance imaging time can be reduced from multiple aspects.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a flowchart of a scan protocol parameter determination method according to an embodiment of the present invention;

FIG. 2A is a schematic diagram of a normal vector distribution diagram provided by a first embodiment of the present invention;

FIG. 2B is a schematic view of a projection of a normal vector of an object according to an embodiment of the invention;

FIG. 3A is a schematic diagram of the number of target normal vectors corresponding to the spherical distance between the target normal vector and the original magnetic field normal vector according to the first embodiment of the present invention;

FIG. 3B is a diagram illustrating a relationship between a minimum spherical distance and a corresponding number of target normal vectors according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of a recommendation parameter prompt message according to an embodiment of the present invention;

figure 5 is a control block diagram of a magnetic resonance system provided in accordance with a third embodiment of the present invention;

fig. 6 is a schematic structural diagram of a magnetic resonance system according to a third embodiment of the present invention.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described by means of implementation examples with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

Example 1

Fig. 1 is a flowchart of a magnetic resonance scanning method according to an embodiment of the present invention. The technical scheme of the embodiment is suitable for the condition of quickly and automatically completing the modification of the scanning protocol parameters. The method may be performed by a controller provided by an embodiment of the present invention. The method specifically comprises the following steps:

s101, setting scanning protocol parameters, wherein the scanning protocol parameters are used for exciting one or more slices of a target object, and the scanning protocol parameters comprise a slice selection gradient, a phase encoding gradient and a frequency encoding gradient.

Before performing magnetic resonance scanning on a target object, corresponding scanning protocol parameters need to be set at a parameter setting interface. The scan protocol parameters include slice selection gradients (parameters), phase encoding gradients (parameters), and frequency encoding gradients (parameters), and are used to excite one or more slices of the target subject. By way of example, the parameters of the slice selection gradient, the phase encoding gradient and the frequency encoding gradient can be the direction of application of the gradient field, the field strength of the gradient field, the moment of application of the gradient, the duration of the gradient, etc. The target object may be a tissue, organ or local area of interest in a human or animal body and comprises one or more slices to be scanned.

In some embodiments, the scan protocol parameters further include, but are not limited to, time-dependent parameters such as repetition time, echo time, effective echo time, echo chain length, echo gap, inversion time, excitation times, acquisition time, or spatial resolution-dependent parameters such as layer thickness, layer spacing, matrix, and field of view, or deflection angle is equal to energy-dependent parameters.

S101, updating the scanning protocol parameters when the scanning protocol parameters are detected so that the target object has PNS overrun slices to be scanned in the magnetic resonance data acquisition process, wherein the updating method of the scanning protocol parameters comprises the step of determining the application direction of one or more of a slice selection gradient, a phase encoding gradient and a frequency encoding gradient based on a golden ratio algorithm.

In one embodiment, the scanning protocols may include segmented scanning protocols corresponding to different scanning time periods, scanning protocol parameters of each segmented scanning protocol may be calculated respectively, so that whether a PNS overrun to-be-scanned slice exists in the target object in the magnetic resonance data acquisition process, and updating of scanning protocol parameters is performed only on the segmented scanning protocols with PNS overrun to-be-scanned slices, thereby improving online operation efficiency of the sequence.

In one embodiment, the scanning protocols may include segmented scanning protocols corresponding to different scanning time periods, scanning protocol parameters of each segmented scanning protocol may be calculated respectively, so that whether PNS overrun to-be-scanned slices exist in the target object in the magnetic resonance data acquisition process or not is ensured, and the scanning protocol parameters of all segmented scanning protocols are updated to obtain a globally optimized scanning protocol, so that quality of final imaging is ensured.

After setting the scan protocol parameters, PNS security checks are preferably performed on the scan protocol parameters before using the scan protocol parameters to perform magnetic resonance scanning on the target object in order to improve the security of the magnetic resonance scanning. If the scanning protocol parameter is detected during the safety inspection so that the target object has PNS overrun slices to be scanned in the magnetic resonance data acquisition process, the scanning protocol parameter is updated.

Wherein the updating method of the scanning protocol parameters comprises determining the application direction of one or more of the slice selection gradient, the phase encoding gradient and the frequency encoding gradient based on the golden ratio algorithm. The method comprises the following steps: and generating a normal vector distribution diagram of the PNS overrun slice to be scanned according to a golden ratio algorithm, wherein the normal vector in the normal vector distribution diagram is distributed around the original normal vector of the slice to be scanned. Fig. 2A and fig. 2B show distribution of a large number of normal vectors within a range of 5 degrees around an original normal vector of a slice to be scanned, the center of a target object is equivalent to the origin of coordinates in fig. 2A or fig. 2B, the slice to be scanned of the target object is in a plane determined by XY, a plurality of points in fig. 2A are a plurality of projection points of a plurality of preset vectors on a spherical surface, fig. 2B is a plurality of preset vectors passing through the center of the target object, and the rotation angle of each preset normal vector is different from the original normal vector of the slice to be scanned; determining a target normal vector in the normal vector distribution map; and determining the application direction of one or more of a slice selection gradient, a phase encoding gradient and a frequency encoding gradient corresponding to the slice to be scanned according to the target normal vector.

The method for generating the vector distribution map based on the golden ratio algorithm comprises the following steps: determining golden angles corresponding to a plurality of preset vectors; calculating the coordinates of the X-axis direction and the Y-axis direction of a plurality of projection points of each preset vector on the spherical surface and the coordinates of the Z-axis of a plurality of projection points of each preset vector on the spherical surface respectively under the golden ratio through the golden angle corresponding to the preset vector; and obtaining the distance (or the minimum spherical distance) between the projection point and the center of the target object in the golden ratio according to the three coordinates. Wherein:

phi(n)＝2×3.14×137.51×n/360

theta(n)＝asin(n/N)

x＝cos(theta(n))×cos(phi(n))

y＝cos(theta(n))×sin(phi(n))

z＝sin(theta(n))

wherein n is an index number, phi is an angle, theta (n) is an included angle between a layer normal vector and an XY plane; the angle between the projection of Phi (n) normal vector on the XY plane and X. In some embodiments, the slice direction to be scanned is the XY plane direction, X is the readout gradient direction, Y is the phase encoding direction, and Z is the slice selection gradient direction.

To facilitate a more intuitive understanding of the distribution in the normal vector distribution map, the distribution angle range of the normal vector is set to 180 degrees, i.e., the normal vector is distributed over a hemisphere, see fig. 3A, and the projections of the plurality of pre-vectors are distributed on the spherical surface. In fig. 3A, the relationship of the minimum spherical distance between normal vectors to the corresponding number is seen in fig. 3B. In the embodiment of the invention, the method for generating the vector distribution diagram based on the golden ratio algorithm and determining the target normal vector based on the distribution diagram is not easy to be influenced by the number of the preset normal vectors, when the number of the preset normal vectors changes from 0 to 1000, the distance difference between the target normal vector and the original layer normal vector is small, and the target normal vector fluctuates within the range of 0.05-0.08, so that the method has good robustness. The target normal vector selected by the method can not generate larger errors due to the number of the preset normal vectors, and the calculation accuracy of the target normal vector is high.

Preferably, the scanning protocol parameter updating method comprises the following steps: and setting the number of the normal vector with the smallest included angle with the original normal vector of the slice to be scanned in the normal vector distribution diagram to be 0, calculating whether the gradient climbing rate of the magnetic field corresponding to each normal vector exceeds a threshold value from the normal vector with the number of 0, if so, determining that the normal vector can cause PNS overrun of the slice to be scanned, and if not, determining that the normal vector can not cause PNS overrun of the slice to be scanned. And taking the first normal vector which does not cause PNS overrun of the slice to be scanned during magnetic resonance data acquisition as the target normal vector of the slice to be scanned. It should be noted that, when the number of normal vectors in the normal vector distribution diagram, that is, the number of spherical points in fig. 2A varies from 0 to 1000, PNS corresponding to the gradient field obtained by optimization is basically maintained between 0.05 and 0.08, that is, the method for updating the scanning protocol parameters based on the golden ratio algorithm is not easily affected by the number of normal vectors, and has good stability and high accuracy of updating results.

In an embodiment, the scanning protocols may include segmented scanning protocols corresponding to different scanning time periods, and the PNS value corresponding to each segmented scanning protocol is calculated by the following formula:

Wherein SR is the gradient climbing rate, gscale is the maximum dB/dt generated in the conforming volume when the gradient climbs at the climbing rate of 1T/m/s, and Limit is the threshold of the normal mode or the primary controlled operation mode.

In one embodiment, the scanning protocol may include a segmented scanning protocol corresponding to different scanning time periods, and the global PNS value calculation formula corresponding to the scanning protocol is:

wherein o represents the equivalent global maximum PNS value after merging gradient units in three directions; w (w) _i Weights representing the gradient units in each direction; o (o) _i The individual PNS values for each gradient element are represented, i representing the number of gradient elements, 1.ltoreq.i.ltoreq.3, which may form, for example, a layer selection gradient field, a phase encoding gradient field and a frequency encoding gradient field.

When judging whether the gradient climbing rate of the magnetic field exceeds the threshold value, it may be judged only whether the gradient climbing rate of the magnetic field on a certain axis exceeds the threshold value of the axis, or whether the gradient climbing rate of the magnetic field on each axis exceeds the threshold value of each axis, the latter being preferable in this embodiment.

In some embodiments, upon updating of scan protocol parameters, the direction of application of the slice selection gradient, phase encoding gradient, and frequency encoding gradient for the slice to be scanned for which PNS overrun exists is determined based only on the golden ratio algorithm, while preserving the slice selection gradient, phase encoding gradient, and frequency encoding gradient for the slice to be scanned for which PNS overrun does not occur. In other words, when the scan protocol parameters need to be updated, only the partial scan protocol parameters corresponding to the slice to be scanned, in which the PNS overrun exists, may be updated.

In some embodiments, when the scanning protocol parameters are updated, the application directions of the layer selection gradient, the phase encoding gradient and the frequency encoding gradient of all the layers to be scanned are redetermined according to the golden ratio algorithm and the original normal vector of the layers to be scanned with PNS overrun. In other words, when it is detected that the scan protocol parameters need to be updated, the scan protocol parameters of all the slices to be scanned are updated based on the golden ratio algorithm, so that the PNS overrun problem does not exist in all the slices to be scanned.

In some embodiments, when the scanning protocol parameter is detected so that the target object has a PNS overrun slice to be scanned in the magnetic resonance data acquisition process, PNS overrun prompt information is output, so that a user can know the scannable range of the current scanning protocol parameter in time.

In some embodiments, the update-prompting message is also output before the update of the scan protocol parameters is completed. As shown in fig. 4, the update-promoting information includes recommended values of the protocol parameters, where the recommended values include: one or more of a gradient rotation angle recommended value, a gradient recommended mode, a bandwidth recommended value, a reading resolution recommended value and a phase resolution recommended value can be selected by a user to accept one or more recommended values for updating the scanning protocol parameters.

In some embodiments, the update hint information further includes summary information, such as a recommended value of a protocol parameter displayed for a display interface in fig. 4, and determines that PNS is limited according to the scanned protocol parameter, and the current security mode is a normal mode. The rotation angle corresponding to the slice to be scanned is a column in the recommended parameters, the scanning protocol parameters are that the user adjusts the current cross section (TRA) to be rotated by 3.5 degrees by the coronal plane (COR), and the system recommends that the user adjusts the current cross section (TRA) to be rotated by 5.6 degrees by the coronal plane (COR). In some embodiments, a column of gradient modes in recommended parameters may also be included, the scan protocol parameters set the gradient mode high for the user, and the system recommends the gradient mode low for the user. In some embodiments, a column of bandwidths in recommended parameters may also be included, the scan protocol parameters set the current bandwidth to 2500 for the user, and the system recommends the current bandwidth to 2450 for the user. In some embodiments, a layer thickness column in the recommended parameters may also be included, the scan protocol parameters set the current layer thickness to 3mm for the user, and the system recommends the current layer thickness to 3.2mm for the user. The read resolution in the recommended parameters is column, the scan protocol parameters set the current read resolution to 256 for the user, and the system recommends the current read resolution to 240 for the user. In some embodiments, a column of phase resolution in recommended parameters may also be included, the scan protocol parameters set the current phase resolution to 100% for the user, and the system recommends the current phase resolution to 98% for the user. Of course, a protocol details option for querying updated scan protocol parameter specific information, such as "open protocol" in fig. 4, is also included.

In some embodiments, the update hint information further includes a scan protocol parameter selection option, see "O" in fig. 4, where the parameter corresponding to the selected "O" (first "O" in fig. 4) is the scan protocol parameter selected by the user, and the parameter corresponding to the "O" that is not selected is the scan protocol parameter abandoned by the user. It will be appreciated that the scan protocol parameters discarded by the user are scan protocol parameters that are disabled.

Also included in fig. 4 are a "ok" option and a "cancel" option. In some embodiments, if the user clicks the "ok" option, it indicates that the user accepts the current scan protocol parameter update information, and if the user clicks the "cancel" option, it indicates that the user does not accept the current scan protocol parameter update information, at which time a PNS overrun hint is preferably output, and the PNS overrun hint is associated with the update hint information, so that the user refers to the update hint information again.

S103, performing magnetic resonance imaging on the target object according to the updated scanning protocol parameters.

After the updated scanning protocol parameters are obtained, performing magnetic resonance scanning on the target object according to the updated scanning protocol parameters to obtain magnetic resonance data, and then performing magnetic resonance image reconstruction on the magnetic resonance data to obtain a magnetic resonance image of the target object.

Example two

On the basis of the scan protocol parameter determining method, the application also provides a magnetic resonance imaging method, which divides the scan protocol into a plurality of visualized sequence sub-modules: sequence regular sub-modules, sequence basic building blocks, which are present in the tool box in the form of visualization modules. The sequence conventional submodules comprise a fat pressing module, a space saturation band module, a reverse recovery module and the like; the sequence basis building blocks include, for example, RF excitation pulses, refocusing pulses, slice selection gradients, phase encoding gradients, frequency encoding gradients, and the like. The basic constituent units can flexibly carry out parameter configuration so as to meet the design requirement of a target sequence. The parameter settings of the slice selection gradient, the phase encoding gradient, and the frequency encoding gradient may be as described in the foregoing steps S101 and S102.

In one embodiment, the operator can drag modules in the tool box into the target sequence, and optionally adjust the sequence composition modules and timing relationships as desired by the design. Further, the timing relationship may implement an automatic optimization function. Illustratively, when the scanning protocol requires a minimum repetition Time (TR) design, the system can optimize the timing of each RF excitation pulse and gradient layer selection gradient, phase encoding gradient, frequency encoding gradient using an automatic algorithm to achieve the minimum TR design objective.

In one embodiment, the scan protocol is associated with a mannequin that includes one or more of patient height, weight, fat content and distribution, physiological motion state, etc., parameters of the mannequin may be adaptively modified for different patients, while thresholds of the scan protocol associated with the mannequin may be synchronously modified, such as Specific Absorption Rate (SAR) values, PNS values, etc. By setting the scanning protocol to be associated with a human body model, the human body model can be conveniently and flexibly adjusted to adapt to different scanning requirements.

Example III

An embodiment of the present invention provides a magnetic resonance system, as shown in fig. 5 and 6, the system includes a scanning device 110, the scanning device 110 includes a radio frequency transmitting coil 111, a gradient coil 112, a radio frequency receiving coil 113, and a controller 120, the radio frequency transmitting coil 111 is used for transmitting a radio frequency pulse to a scanning site of a target object so as to excite nuclear spins of the scanning site; gradient coils 112 are used to apply slice selection gradient fields, phase encoding gradient fields, and frequency encoding gradient fields to the scan site to produce echo signals; the radio frequency receiving coil 113 is used for receiving echo signals to form magnetic resonance scanning data; the controller 120 is configured to receive set scan protocol parameters, where the scan protocol parameters are configured to excite one or more slices of the target object, and the scan protocol parameters include a slice selection gradient, a phase encoding gradient, and a frequency encoding gradient; updating the scanning protocol parameters when the scanning protocol parameters show that the target object has PNS overrun slices to be scanned in the magnetic resonance data acquisition process, wherein the updating method of the scanning protocol parameters comprises the steps of determining the application direction of one or more of a slice selection gradient, a phase encoding gradient and a frequency encoding gradient based on a golden ratio algorithm; the updated scan protocol parameters are used to acquire magnetic resonance data of the target object.

Before performing magnetic resonance scanning on a target object, corresponding scanning protocol parameters need to be set at a parameter setting interface. The scan protocol parameters include slice selection gradients, phase encoding gradients, and frequency encoding gradients, and are used to drive gradient coils to apply gradient fields of slice selection directions, phase encoding directions, and frequency encoding directions to a target object.

In some embodiments, the scan protocol parameters also include, but are not limited to, layer thickness, bandwidth, gradient pattern.

Wherein the method of updating the scan protocol parameters comprises determining the direction of application of one or more of the slice selection gradient, the phase encoding gradient and the frequency encoding gradient based on a golden ratio algorithm. The method comprises the following steps: and generating a normal vector distribution diagram of the PNS overrun slice to be scanned according to a golden ratio algorithm, wherein the normal vector in the normal vector distribution diagram is distributed around the original normal vector of the slice to be scanned. FIGS. 2A and 2B show the distribution of a large number of normal vectors within 5 degrees around the original normal vector of the sheet to be scanned; determining a target normal vector in the normal vector distribution map; and determining a rotation angle according to an included angle between the target normal vector and the normal vector of the slice to be scanned, and redetermining the application directions of the layer selection gradient, the phase encoding gradient and the frequency encoding gradient corresponding to the slice to be scanned according to the rotation angle and the normal vector of the slice to be scanned.

phi(n)＝2×3.14×137.51×n/360

theta(n)＝asin(n/N)

x＝cos(theta(n))×cos(phi(n))

y＝cos(theta(n))×sin(phi(n))

z＝sin(theta(n))

To facilitate a more intuitive understanding of the distribution in the normal vector distribution map, the distribution angle range of the normal vector is set to 180 degrees, i.e., the normal vector is distributed on a hemisphere, see fig. 3A. In fig. 3A, the relationship of the minimum spherical distance between normal vectors to the corresponding number is seen in fig. 3B.

In some embodiments, after the update of the scan protocol parameters is completed, an update hint is also output. As shown in fig. 4, the update-promoting information includes cross-section (TRA) rotation angle information and coronal plane (COR) rotation angle information, gradient pattern, bandwidth, resolution, and layer thickness.

Because the golden ratio algorithm can give a dense and uniformly distributed normal vector distribution diagram, the normal vector of the gradient field of the slice to be scanned, which is determined according to the golden ratio algorithm, can not only solve the problem of PNS overrun, but also make the included angle between the updated normal vector of the gradient field of the slice to be scanned and the original normal vector smaller, and the smaller included angle of the normal vector corresponds to shorter gradient field forming time, and the automatic updating of the scanning protocol parameters is helpful for reducing the time spent by an operator for modifying the scanning protocol parameters, so that the magnetic resonance imaging time can be reduced from multiple aspects.

As shown in fig. 6, the magnetic resonance imaging system 100 further includes a processor 130, an input device 140, and an output device 150, and the controller 120 may include one or a combination of several of a central controller (Central Processing Unit, CPU), application-specific integrated circuit (ASIC), special instruction controller (Application Specific Instruction Set Processor, ASIP), graphics processing unit (Graphics Processing Unit, GPU), physical controller (Physics Processing Unit, PPU), digital signal controller (Digital Processing Processor, DSP), field-programmable gate array (Field-Programmable Gate Array, FPGA), ARM controller, and the like.

An output device 150, such as a display, may display the magnetic resonance image of the region of interest. Further, the output device 150 may also display the height, weight, age, imaging location, and operating status of the scanning device 110 of the subject. The type of the output device 150 may be one or a combination of several of a Cathode Ray Tube (CRT) output device, a liquid crystal output device (LCD), an organic light emitting output device (OLED), a plasma output device, etc. In an embodiment, the display is configured to display a recommended value of a protocol parameter in response to scanning the protocol parameter so that a target object has a PNS overrun slice to be scanned in a magnetic resonance data acquisition process, the recommended value including: one or more of gradient rotation angle recommendation, gradient recommendation mode, bandwidth recommendation, readout resolution recommendation, phase resolution recommendation.

The magnetic resonance imaging system 100 may be connected to a local area network (Local Area Network, LAN), wide area network (Wide Area Network, WAN), public network, private network, proprietary network, public switched telephone network (Public Switched Telephone Network, PSTN), the internet, wireless network, virtual network, or any combination thereof.

The scanning device 110 comprises an MR signal acquisition module, an MR control module and an MR data storage module. The MR signal acquisition module comprises a magnet unit and a radio frequency unit. The magnet unit mainly includes a main magnet generating a B0 main magnetic field and a gradient assembly generating a gradient. The main magnet contained in the magnet unit may be a permanent magnet or a superconducting magnet, the gradient assembly mainly comprises gradient current Amplifiers (AMPs), gradient coils, and the gradient assembly may further comprise three independent channels Gx, gy, gz, each gradient amplifier exciting a corresponding one of the gradient coils in the gradient coil set to generate gradient fields for generating corresponding spatially encoded signals for spatially localization of the magnetic resonance signals. The radio frequency unit mainly comprises a radio frequency transmitting coil and a radio frequency receiving coil, wherein the radio frequency transmitting coil is used for transmitting radio frequency pulse signals to a person to be detected or a human body, the radio frequency receiving coil is used for receiving magnetic resonance signals acquired from the human body, and the radio frequency coils forming the radio frequency unit can be divided into a body coil and a local coil according to different functions. In one embodiment, the type of body coil or local coil may be a birdcage coil, a solenoid coil, a saddle coil, a helmholtz coil, an array coil, a loop coil, or the like. In one particular embodiment, the local coils are provided as array coils, and the array coils may be provided in a 4-channel mode, an 8-channel mode, or a 16-channel mode. The magnet unit and the radio frequency unit may constitute an open low field magnetic resonance device or a closed superconducting magnetic resonance device.

The MR control module may monitor an MR signal acquisition module, an MR data processing module, comprising a magnet unit and a radio frequency unit. Specifically, the MR control module may receive the information or pulse parameters sent by the MR signal acquisition module; in addition, the MR control module can also control the processing procedure of the MR data processing module. In one embodiment, the MR control module is further connected to a pulse sequence generator, a gradient waveform generator, a transmitter, a receiver, etc., and controls the magnetic field module to execute a corresponding scanning sequence after receiving instructions from the console.

Illustratively, the specific process of generating MR data by the scanning device 110 in the embodiments of the present invention includes: the main magnet generates a B0 main magnetic field, and atomic nuclei in the subject generate precession frequency under the action of the main magnetic field, wherein the precession frequency is in direct proportion to the intensity of the main magnetic field; the MR control module stores and transmits an instruction of a scan sequence to be executed, the pulse sequence generator controls the gradient waveform generator and the transmitter according to the scan sequence instruction, the gradient waveform generator outputs gradient pulse signals with preset time sequences and waveforms, the signals pass through Gx, gy and Gz gradient current amplifiers, and then pass through three independent channels Gx, gy and Gz in the gradient assembly, and each gradient amplifier excites a corresponding gradient coil in the gradient coil group to generate a gradient field for generating corresponding spatial coding signals so as to spatially locate magnetic resonance signals; the pulse sequence generator also executes a scanning sequence, outputs data including timing, intensity, shape and the like of radio frequency pulses transmitted by radio frequency, timing of radio frequency reception and length of a data acquisition window to the transmitter, simultaneously the transmitter transmits corresponding radio frequency pulses to a body transmitting coil in the radio frequency unit to generate a B1 field, signals emitted by excited atomic nuclei in a patient body under the action of the B1 field are perceived by a receiving coil in the radio frequency unit, and then transmitted to an MR data processing module through a transmitting/receiving switch, and is subjected to digital processing such as amplification, demodulation, filtering, AD conversion and the like, and then transmitted to an MR data storage module. The scan is completed when the MR data storage module acquires a set of raw k-space data. The raw k-space data is rearranged into separate k-space data sets corresponding to each image to be reconstructed, each k-space data set is input to an array controller, and the image reconstruction is performed to combine the magnetic resonance signals to form a set of image data.

Note that the above is only a preferred embodiment of the present invention and the technical principle applied. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, while the invention has been described in connection with the above embodiments, the invention is not limited to the embodiments, but may be embodied in many other equivalent forms without departing from the spirit or scope of the invention, which is set forth in the following claims.

Claims

1. A method for determining scan protocol parameters, comprising:

Performing magnetic resonance imaging on the target object according to the updated scanning protocol parameters;

determining an application direction of one or more of a slice selection gradient, a phase encoding gradient, and a frequency encoding gradient based on the golden ratio algorithm comprises:

generating a normal vector distribution diagram of a PNS overrun slice to be scanned based on a golden ratio algorithm, wherein the normal vector in the normal vector distribution diagram is distributed around the original normal vector of the slice to be scanned;

determining a target normal vector in the normal vector distribution map;

determining an application direction of one or more of a slice selection gradient, a phase encoding gradient, and a frequency encoding gradient from the target normal vector;

the generating the normal vector distribution map of the PNS overrun slice to be scanned based on the golden ratio algorithm comprises the following steps: determining golden angles corresponding to a plurality of preset vectors; calculating the coordinates of the X-axis direction and the Y-axis direction of a plurality of projection points of each preset vector on the spherical surface and the coordinates of the Z-axis of a plurality of projection points of each preset vector on the spherical surface under the golden ratio respectively through the golden angle corresponding to the preset vector; and obtaining the distance between the projection point and the center of the target object in the golden ratio according to the three coordinates.

2. The method of claim 1, wherein said determining a target normal vector in said normal vector distribution map comprises:

and taking the normal vector which has the smallest included angle with the original normal vector of the slice to be scanned and does not cause the PNS overrun of the slice to be scanned in the normal vector distribution diagram as a target normal vector.

3. The method of claim 1, further comprising, prior to said updating said scan protocol parameters:

displaying recommended values of the protocol parameters, wherein the recommended values comprise: one or more of gradient rotation angle recommendation, gradient recommendation mode, bandwidth recommendation, readout resolution recommendation, phase resolution recommendation.

4. A method according to any of claims 1-3, wherein said updating said scanning protocol parameters comprises:

determining the application directions of a layer selection gradient, a phase encoding gradient and a frequency encoding gradient of a slice to be scanned, which have PNS overrun, according to a golden ratio algorithm; or alternatively

And re-determining the layer selection gradient, the phase encoding gradient and the application direction of the frequency encoding gradient of all the layers to be scanned according to the golden ratio algorithm and the original normal vector of the layers to be scanned with PNS overrun.

5. A magnetic resonance system, comprising:

a controller for receiving set scan protocol parameters for exciting one or more slices of a target object, the scan protocol parameters including a slice selection gradient, a phase encoding gradient, and a frequency encoding gradient; updating the scanning protocol parameters when the scanning protocol parameters show that the target object has PNS overrun slices to be scanned in the magnetic resonance data acquisition process, wherein the updating method of the scanning protocol parameters comprises the steps of determining the application direction of one or more of a slice selection gradient, a phase encoding gradient and a frequency encoding gradient based on a golden ratio algorithm; the updated scanning protocol parameters are used for acquiring magnetic resonance data of the target object;

generating a normal vector distribution diagram of a PNS overrun slice to be scanned based on a golden ratio algorithm, wherein the normal vector in the normal vector distribution diagram is distributed around the normal vector of the original slice of the slice to be scanned;

determining a target normal vector in the normal vector distribution map;

determining an application direction of one or more of a slice selection gradient, a phase encoding gradient, and a frequency encoding gradient according to the target normal vector;

6. The system of claim 5, wherein said determining a target normal vector in said normal vector distribution map comprises:

and taking the normal vector which has the smallest included angle with the original normal vector of the slice to be scanned and does not cause overrun of PNS of the slice to be scanned in the normal vector distribution diagram as a target normal vector.

7. The system of any of claims 5-6, wherein the updating the scan protocol parameters comprises:

8. The system of claim 5, further comprising a display coupled to the controller, the display responsive to the scan protocol parameter causing a target object to have PNS overrun slices to be scanned during magnetic resonance data acquisition, the recommendation value to display the protocol parameter comprising: one or more of gradient rotation angle recommendation, gradient recommendation mode, bandwidth recommendation, readout resolution recommendation, phase resolution recommendation.