CN107495967B - Method, device and system for predicting and controlling radio frequency energy deposition and storage medium - Google Patents
Method, device and system for predicting and controlling radio frequency energy deposition and storage medium Download PDFInfo
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Abstract
The invention provides a radio frequency energy deposition prediction and control method, a device, a system and a storage medium for magnetic resonance scanning, wherein the method comprises the following steps: determining the frequency of each radio frequency excitation pulse contained in a multi-slice scanning sequence to be implemented; retrieving and extracting pre-stored imaging body absorption power factors respectively corresponding to each of the determined frequencies of the radio frequency excitation pulses; acquiring pre-stored forward power values respectively associated with each of the determined frequencies of the radio-frequency excitation pulses, and calculating a total imaging volume absorption power value based on the imaging volume absorption power factor and the forward power values; and acquiring a prestored imaging body mass value, and calculating a specific absorption rate predicted value aiming at the radio frequency pulse scanning sequence to be implemented on the basis of the calculated total imaging body absorption power value and the imaging body mass value. The radio frequency energy deposition prediction and control method, the device and the storage medium disclosed by the invention can obviously improve the accuracy of the specific absorption rate prediction value.
Description
Technical Field
The invention relates to the field of medical images, in particular to a radio frequency energy deposition prediction and control method, a device and a storage medium for magnetic resonance scanning.
Background
Currently, with the increasing development of medical imaging technology, it becomes more and more important to perform a magnetic resonance-based scan on an imaging volume (e.g., a human body) to acquire a magnetic resonance image.
Typically, when performing a magnetic resonance scan, the deposited amount of radio frequency energy absorbed by the imaging volume over a predetermined time (e.g., 6 minutes) needs to be monitored to ensure compliance with radio frequency safety standards (such as YY0319/IEC60601-2-33 standards). Here, the value of the deposition amount of the radio frequency energy absorbed by the imaging body for a predetermined time is represented by SAR (specific absorption Rate), and the value thereof causes a safety risk if a threshold value prescribed by a relevant standard is exceeded. The value of the SAR is typically defined by: SAR is the imaging volume absorbed power/imaging volume mass.
Therefore, before the actual magnetic resonance scan is performed on the imaging body, the SAR value prediction needs to be performed on the scan sequence to be implemented, and if the predicted value of the SAR exceeds the threshold value specified by the relevant standard, the scan sequence to be implemented is not executed, otherwise, the scan sequence to be implemented is executed.
In a conventional solution, a pre-scan operation is performed before performing an actual magnetic resonance scan to complete a center frequency calibration, so as to ensure that the frequency of the rf pulse excitation is consistent with the lamor precession frequency of an imaging subject (e.g., a human body) (when the imaging subject enters a main magnetic field, the imaging subject generates a net magnetization vector aligned along the direction of the main magnetic field, the imaging subject contains spin nuclei precession at a certain frequency, which is called the lamor precession frequency), and then an rf link calibration operation is performed at the center frequency to obtain rf characteristic parameters, which include forward power, reflected power, and the like, then an absorption power factor is calculated based on the obtained rf characteristic parameters, and a body absorption power is calculated according to the absorption power factor and the forward power, and thus a predicted SAR value is calculated according to the formula.
However, the above conventional technical solutions have the following problems: since the predicted value of the SAR is calculated according to the radio frequency characteristic parameter at the central frequency, a large prediction error is caused under the condition of multi-slice scanning, thereby affecting the accuracy of the SAR predicted value.
Disclosure of Invention
In order to solve the problems in the prior art, the present invention provides a method, an apparatus and a storage medium for predicting and controlling rf energy deposition for magnetic resonance scanning.
In one aspect of the invention, there is provided a radio frequency energy deposition prediction apparatus for a magnetic resonance scan, the radio frequency energy deposition prediction apparatus comprising:
a radio frequency pulse data acquisition unit configured to acquire a multi-slice scan sequence to be implemented from a data storage based on a trigger instruction from a controller to determine a frequency of each radio frequency excitation pulse included in the multi-slice scan sequence to be implemented;
an absorption power factor determination unit configured to retrieve and extract pre-stored imaging volume absorption power factors from the data storage, each corresponding to each of the determined frequencies of radio frequency excitation pulses;
an absorption power determination unit configured to retrieve from the data memory pre-stored forward power values respectively associated with each of the determined frequencies of radio frequency excitation pulses and to calculate an imaging volume total absorption power value based on the extracted imaging volume absorption power factor and the forward power values;
a prediction unit configured to acquire a pre-stored imaging volume quality value from the data storage, and calculate a specific absorption rate prediction value for the RF pulse scan sequence to be implemented based on the calculated imaging volume total absorption power value and the imaging volume quality value, and then feed back the specific absorption rate prediction value to the controller.
In another aspect of the invention, there is provided a radio frequency energy deposition control system for a magnetic resonance scan, the radio frequency energy deposition control system comprising a radio frequency energy deposition prediction apparatus as described above and a controller configured to trigger the radio frequency energy deposition prediction apparatus to perform a prediction operation before actually performing a multi-slice scan sequence to be performed, and to determine whether to subsequently and actually perform the multi-slice scan sequence to be performed based on a specific absorption rate prediction value fed back by the radio frequency energy deposition prediction apparatus, wherein if the specific absorption rate prediction value is smaller than a predetermined threshold, a scan execution mechanism is driven to perform the multi-slice scan sequence to be performed, and otherwise, the execution of the multi-slice scan sequence to be performed is postponed or terminated.
In another aspect of the invention, there is provided a method of radio frequency energy deposition prediction for a magnetic resonance scan, the method comprising the steps of:
acquiring a multi-slice scanning sequence to be implemented to determine the frequency of each radio frequency excitation pulse contained in the multi-slice scanning sequence to be implemented;
retrieving and extracting from the data store pre-stored imaging volume absorption power factors corresponding respectively to each of the determined frequencies of the radio frequency excitation pulses;
obtaining from the data store pre-stored forward power values associated with each of the determined frequencies of the radio frequency excitation pulses, respectively, and calculating an imaging volume total absorption power value based on the extracted imaging volume absorption power factor and the forward power values;
and acquiring a prestored imaging body mass value from the data memory, and calculating a specific absorption rate predicted value aiming at the radio frequency pulse scanning sequence to be implemented based on the calculated total imaging body absorption power value and the imaging body mass value.
In another aspect of the invention, there is provided a radio frequency energy deposition control method for magnetic resonance scanning, the radio frequency energy deposition control method comprising the steps of:
performing the radio frequency energy deposition prediction method described above to obtain a specific absorption rate prediction value before actually performing a multi-slice scan sequence to be performed;
and determining whether the multi-slice scanning sequence to be implemented is actually executed according to the specific absorption rate predicted value.
In another aspect of the invention, a computer-readable storage medium is provided for storing processor-executable instructions that, when executed, are capable of causing a processor to implement the method for radio frequency energy deposition prediction described above.
In another aspect of the invention, a computer-readable storage medium is provided for storing processor-executable instructions that, when executed, are capable of causing a processor to implement the rf energy deposition control method described above.
In another aspect of the invention, a computer device is provided, the computer device comprising any of the computer-readable storage media described above and a processor capable of executing processor-executable instructions stored in the computer-readable storage medium.
Compared with the prior art, the radio frequency energy deposition prediction and control method, the device and the storage medium for magnetic resonance scanning, which are provided by the invention, allow for the in-band fluctuation characteristic of the radio frequency pulse existing in a multi-slice scanning sequence, so that whether the scanning operation meets the safety standard or not can be monitored based on a more accurate specific absorption rate prediction value.
Drawings
Figure 1 is a schematic diagram of an exemplary magnetic resonance system;
FIG. 2 is a timing diagram of a typical multi-slice scan sequence;
FIG. 3 is a schematic diagram of an RF energy deposition prediction apparatus according to some embodiments of the invention;
FIG. 4 is a schematic structural diagram of an RF energy deposition control system according to some embodiments of the present invention;
FIG. 5 is a flow diagram of a method of RF energy deposition prediction, according to some embodiments of the invention;
FIG. 6 is a flow chart of a method of RF energy deposition control according to some embodiments of the present invention.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. In the following description, specific details are set forth in order to provide a thorough understanding of the present invention. The invention can be implemented in a number of ways different from those described herein and similar generalizations can be made by those skilled in the art without departing from the spirit of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.
As used in this application and the appended claims, the terms "a," "an," "the," and/or "the" are not intended to be inclusive in the singular, but rather are intended to be inclusive in the plural unless the context clearly dictates otherwise. In general, the terms "comprises" and "comprising" merely indicate that steps and elements are included which are explicitly identified, that the steps and elements do not form an exclusive list, and that a method or apparatus may include other steps or elements.
Flow charts are used herein to illustrate operations performed by devices and/or systems according to embodiments of the present application. It should be understood that the preceding or following operations are not necessarily performed in the exact order in which they are performed. Rather, various steps may be processed in reverse order or simultaneously. Meanwhile, other operations may be added to the processes, or a certain step or several steps of operations may be removed from the processes.
Fig. 1 is a schematic diagram of an exemplary magnetic resonance system, and as shown in fig. 1, a magnetic resonance system 100 generally includes a magnetic resonance housing having a main magnet 101 therein, the main magnet 101 may be formed of superconducting coils for generating a main magnetic field, and in some cases, a permanent magnet may be used. The main magnet 101 may be used to generate a main magnetic field strength of 0.2 tesla, 0.5 tesla, 1.0 tesla, 1.5 tesla, 3.0 tesla, or higher. In magnetic resonance imaging, an imaging subject 150 is carried by the patient couch 106, and as the couch plate moves, the imaging subject 150 is moved into the region 105 where the magnetic field distribution of the main magnetic field is relatively uniform. Generally for a magnetic resonance system, as shown in fig. 1, the z direction of the spatial coordinate system (i.e. the coordinate system of the apparatus) is set to be the same as the axial direction of the gantry of the magnetic resonance system, the length direction of the patient is usually kept consistent with the z direction for imaging, the horizontal plane of the magnetic resonance system is set to be xz plane, the x direction is perpendicular to the z direction, and the y direction is perpendicular to both the x and z directions.
As shown in fig. 1, in magnetic resonance imaging, the pulse control unit 111 controls the radio frequency pulse generating unit 116 to generate a radio frequency pulse, and the radio frequency pulse is amplified by the amplifier, passes through the switch control unit 117, and is finally emitted by the body coil 103 or the local coil 104 to perform radio frequency excitation on the imaging object 150. The imaging subject 150 generates corresponding radio frequency signals from resonance upon radio frequency excitation. When receiving the radio frequency signals generated by the imaging subject 150 according to the excitation, the radio frequency signals may be received by the body coil 103 or the local coil 104, there may be a plurality of radio frequency receiving links, and after the radio frequency signals are sent to the radio frequency receiving unit 118, the radio frequency signals are further sent to the image reconstruction unit 121 for image reconstruction, so as to form a magnetic resonance image.
As shown in fig. 1, the magnetic resonance system 100 also includes gradient coils 102 that may be used to spatially encode radio frequency signals in magnetic resonance imaging. The pulse control unit 111 controls the gradient signal generating unit 112 to generate gradient signals, which are generally divided into three mutually orthogonal directions: gradient signals in the x, y and z directions, which are different from each other, are amplified by gradient amplifiers (113, 114, 115) and emitted from the gradient coil 102, thereby generating a gradient magnetic field in the region 105.
As shown in fig. 1, data transmission can be performed between the pulse control unit 111, the image reconstruction unit 121, the processor 122, the display unit 123, the input/output device 124, the storage unit 125, and the communication port 126 through the communication bus 127, so as to control the magnetic resonance imaging process. The processor 122 may be composed of one or more processors. The display unit 123 may be a display provided to a user for displaying an image. The input/output device 124 may be a keyboard, a mouse, a control box, or the like, and supports input/output of the corresponding data stream. The storage unit 125 may be a Read Only Memory (ROM), a Random Access Memory (RAM), a hard disk, etc., and the storage unit 125 may be used to store various data files that need to be processed and/or used for communication, as well as possible program instructions executed by the processor 122. The communication port 105 may be implemented with other components such as: and the external equipment, the image acquisition equipment, the database, the external storage, the image processing workstation and the like are in data communication.
In the field of magnetic resonance imaging, multi-slice scan sequences are widely used. FIG. 2 is a timing diagram of a typical multi-slice scan sequence. As shown in fig. 2, taking a multi-slice SE (spin echo) scanning sequence as an example, during a time period TR (repetition time), the tissue at different slice positions of the imaging subject is usually excited and the resulting signals are received sequentially to save the total scanning time. Wherein each slice corresponds to a radio frequency excitation frequency (which may also be directly referred to as the frequency of the radio frequency excitation pulse). For the center slice, the excitation frequency is equal to the center frequency, and for the off-center slice, there is a frequency difference between the corresponding radio frequency excitation frequency and the center frequency, and the magnitude of the frequency difference is related to the off-center distance of the slice and the strength of the slice selection gradient. For example, as shown in FIG. 2, the 90 and 180 RF excitation pulses for slice 1 have a frequency f1, the 90 and 180 RF excitation pulses for slice 2 have a frequency f2(f2 ≠ f1), and so on.
Fig. 3 is a schematic structural diagram of an rf energy deposition prediction apparatus for magnetic resonance scanning according to some embodiments of the present invention, and as shown in fig. 3, the rf energy deposition prediction apparatus 200 includes an rf pulse information obtaining unit 201, an absorption power factor determining unit 202, an absorption power determining unit 203, and a prediction unit 204. The rf pulse data acquiring unit 201 is configured to acquire a multi-slice scan sequence to be performed from the data storage 205 based on a trigger instruction from the controller 301 to determine the frequency of each rf excitation pulse included in the multi-slice scan sequence to be performed. The absorption power factor determination unit 202 is configured to retrieve and extract from the data storage 205 pre-stored imaging volume absorption power factors corresponding to each of the determined frequencies of the radio frequency excitation pulses, respectively. The imaging body absorption power factor here refers to the absorption power factor of the imaging body at the corresponding frequency. The absorption power determination unit 203 is configured to retrieve from the data storage 205 pre-stored forward power values respectively associated with each of the determined frequencies of the radio frequency excitation pulses and to calculate an imaging volume total absorption power value based on the extracted imaging volume absorption power factor and the forward power values. The prediction unit 204 is configured to obtain pre-stored values of the imaging volume quality from the data storage 205, and calculate a predicted value of specific absorption rate for the rf pulse scan sequence to be performed based on the calculated values of the total absorption power of the imaging volume and the values of the imaging volume quality, and then feed the predicted value of specific absorption rate back to the controller. As can be seen from the above, the radio frequency energy deposition prediction apparatus disclosed in the present invention can take into account the in-band fluctuation characteristics of the radio frequency pulses existing in the multi-slice scanning sequence (i.e. the frequency difference exists between the radio frequency excitation frequencies corresponding to different slices), so as to significantly improve the accuracy of the specific absorption rate prediction value.
Illustratively, in some embodiments of the invention, the absorption power determination unit 203 is configured to calculate the imaging volume total absorption power value according to: p ═ Σ k (i) × Pf(i) Where P is the total absorption power value of the imager, k (i) is the ith RF excitationFrequency of pulse corresponding to absorption power factor, P, of imaging bodyf(i) Is the forward power value associated with the frequency of the ith radio frequency excitation pulse, i being a positive integer.
Illustratively, in some embodiments of the invention, the prediction unit 204 is configured to calculate the specific absorption rate prediction value according to: SAR is an image volume total absorption power value/image volume measurement value, wherein SAR is a specific absorption rate prediction value.
Illustratively, in some embodiments of the invention, the imaging volume is a human body.
Figure 4 is a schematic block diagram of a radio frequency energy deposition control system for magnetic resonance scanning according to some embodiments of the present invention. As shown in fig. 4, the rf energy deposition control system 300 includes a controller 301 and an rf energy deposition prediction apparatus 200. Wherein the rf energy deposition prediction apparatus 200 is the rf energy deposition prediction apparatus described above in connection with fig. 3. The controller 301 is configured to trigger the rf energy deposition prediction apparatus 200 to perform a prediction operation before actually performing a multi-slice scan sequence to be implemented, and determine whether to subsequently and actually perform the multi-slice scan sequence to be implemented based on a specific absorption rate prediction value fed back by the rf energy deposition prediction apparatus 200, wherein if the specific absorption rate prediction value is smaller than a predetermined threshold, the scan execution mechanism is driven to perform the multi-slice scan sequence to be implemented, otherwise, the execution of the multi-slice scan sequence to be implemented is postponed or terminated, or relevant parameters of the multi-slice scan sequence are automatically adjusted. As can be seen from the above, the rf energy deposition control system disclosed in the present invention significantly enhances the safety of the magnetic resonance scanning by allowing for in-band fluctuation characteristics of the rf pulses (i.e., frequency differences between the rf excitation frequencies corresponding to different slices) present in the multi-slice scan sequence and thus enabling monitoring of compliance with safety standards based on more accurate specific absorption rate prediction values. For example, according to the ICE-related standards, the average SAR of the whole body in the normal mode for 6 minutes cannot exceed 2W/kg, the average SAR of the whole body in the primary controlled operation mode for 6 minutes cannot exceed 4W/kg, and particularly, the average SAR of the head in 6 minutes cannot exceed 3.2W/kg when performing a magnetic resonance scan. If the values specified by the standards are exceeded, excessive rf deposition may be presented to the patient, resulting in a safety risk.
Illustratively, in some embodiments of the invention, the controller 301 is further configured to perform an initialization operation to build an imager model of a particular one of the imagers prior to first performing a multi-slice scan sequence for that imager, and to obtain an imager quality value based on the imager model and to store the imager quality value in the data storage 205.
Illustratively, in some embodiments of the invention, the controller 301 is further configured to perform a pre-scan operation by sending radio frequency calibration pulses before each performance of a multi-slice scan sequence to obtain radio frequency characteristic data corresponding to respective operating frequencies within a predetermined radio frequency bandwidth and to store the radio frequency characteristic data in the data memory 205. Alternatively, the radio frequency characteristic data may be determined by means of pre-testing or theoretical calculations and pre-stored in the data storage. The radio frequency characteristic data includes, but is not limited to, forward power, reflected power, voltage, standing wave ratio, and the like. Wherein the operating frequency refers to an excitation frequency applied to each of the plurality of slices.
Illustratively, in some embodiments of the invention, the controller 301 is further configured to, after obtaining the radio frequency characteristic data, calculate an imager absorption power factor corresponding to each of the respective operating frequencies within the predetermined radio frequency bandwidth based on the radio frequency characteristic data.
Illustratively, in some embodiments of the invention, the controller 301 is further configured to calculate, for each operating frequency, an imaging volume absorption power factor corresponding to that operating frequency according to:
k＝1–(Pr+Pcpl+Pother)/Pf，0<k<1
where k is the imaging volume absorbed power factor corresponding to the operating frequency,Pris the reflected power, P, associated with the operating frequencycplIs the power loss of the coil, PfIs the forward power, P, associated with the operating frequencyotherOther loss power (which may be omitted in the absence of dummy load).
FIG. 5 is a flow diagram of a method of RF energy deposition prediction, according to some embodiments of the invention. As shown in fig. 5, the method for predicting rf energy deposition for mr scanning according to some embodiments of the present invention comprises the following steps: (S401) acquiring a multi-slice scanning sequence to be implemented to determine the frequency of each radio frequency excitation pulse contained in the multi-slice scanning sequence to be implemented; (S402) retrieving and extracting from the data storage pre-stored image volume absorption power factors corresponding respectively to each of the determined frequencies of the radio frequency excitation pulses; (S403) retrieving from the data storage pre-stored forward power values respectively associated with each of the determined frequencies of radio frequency excitation pulses and calculating an imager total absorption power value based on the extracted imager absorption power factor and the forward power values; (S404) obtaining pre-stored values of the imaging modality mass from the data storage, and calculating a predicted value of specific absorption rate for the to-be-performed rf pulse scan sequence based on the calculated values of the total imaging modality absorption power and the values of the imaging modality mass. As can be seen from the above, the method for predicting the specific absorption rate disclosed in some embodiments of the present invention can significantly improve the accuracy of the specific absorption rate prediction value by taking into account the in-band fluctuation characteristics of the rf pulses (i.e., the frequency difference between the rf excitation frequencies corresponding to different slices) in the multi-slice scan sequence.
Exemplarily, in some embodiments of the present invention, the step (S403) further comprises: the total power absorbed by the imaging volume is calculated according to the following formula: p ═ Σ k (i) × Pf(i) Where P is the total absorption power value of the imaging volume, k (i) is the absorption power factor of the imaging volume corresponding to the frequency of the ith RF excitation pulse, Pf(i) Is the forward power value associated with the frequency of the ith radio frequency excitation pulse, i being a positive integer.
Exemplarily, in some embodiments of the present invention, the step (S404) further comprises: calculating the predicted value of specific absorption rate according to the following formula: SAR is an image volume total absorption power value/image volume measurement value, wherein SAR is a specific absorption rate prediction value.
Illustratively, in some embodiments of the invention, the imaging volume is a human body.
FIG. 6 is a flow chart of a method of RF energy deposition control according to some embodiments of the present invention. As shown in fig. 6, the rf energy deposition control method according to some embodiments of the present invention includes the following steps: (S501) performing the rf energy deposition prediction method described above in connection with fig. 5 to obtain a predicted value of the specific absorption rate before actually performing the multi-slice scan sequence to be performed; (S502) determining whether the multi-slice scan sequence to be performed is actually performed according to the specific absorption rate prediction value.
Exemplarily, in some embodiments of the present invention, the step (S502) further comprises: and driving a scanning execution mechanism to execute the multi-slice scanning sequence to be implemented under the condition that the predicted specific absorption rate value is less than a preset threshold value, and otherwise, postponing or terminating the execution of the multi-slice scanning sequence to be implemented. As can be seen from the above, the rf energy deposition control method disclosed in the present invention significantly enhances the safety of the magnetic resonance scanning by considering the in-band fluctuation characteristics of the rf pulses (i.e., the frequency difference between the rf excitation frequencies corresponding to different slices) present in the multi-slice scan sequence and thus being able to monitor whether the safety standard is met based on a more accurate specific absorption rate prediction value. For example, according to the ICE-related standards, the average SAR of the whole body in the normal mode for 6 minutes cannot exceed 2W/kg, the average SAR of the whole body in the primary controlled operation mode for 6 minutes cannot exceed 4W/kg, and particularly, the average SAR of the head in 6 minutes cannot exceed 3.2W/kg when performing a magnetic resonance scan. If the values specified by the standards are exceeded, excessive rf deposition may be presented to the patient, resulting in a safety risk.
Illustratively, in some embodiments of the invention, the rf energy deposition control method further comprises: an initialization operation is performed to build an imager model for a particular one of the imagers prior to first performing a multi-slice scan sequence for that imager, and an imager volume value is obtained from the imager model and stored in the data store 205.
Illustratively, in some embodiments of the invention, the rf energy deposition control method further comprises: a pre-scan operation is performed by sending rf calibration pulses before each performance of a multi-slice scan sequence to obtain rf characteristic data corresponding to each operating frequency over a predetermined rf bandwidth and to store the rf characteristic data in the data memory 205. Alternatively, the radio frequency characteristic data may be determined by means of pre-testing or theoretical calculations and pre-stored in the data storage 205. The radio frequency characteristic data includes, but is not limited to, forward power, reflected power, voltage, standing wave ratio, and the like.
Illustratively, in some embodiments of the invention, the rf energy deposition control method further comprises: calculating an imager absorbed power factor corresponding to each of the respective operating frequencies within the predetermined radio frequency bandwidth based on the radio frequency characteristic data after obtaining the radio frequency characteristic data.
Illustratively, in some embodiments of the invention, the rf energy deposition control method further comprises: for each operating frequency, calculating an imaging volume absorption power factor corresponding to the operating frequency according to:
k＝1–(Pr+Pcpl+Pother)/Pf，0<k<1
where k is the power factor absorbed by the imaging volume corresponding to the operating frequency, PrIs the reflected power, P, associated with the operating frequencycplIs the power loss of the coil, PfIs the forward power, P, associated with the operating frequencyotherOther loss power (which may be omitted in the absence of dummy load).
A computer-readable storage medium to store processor-executable instructions is also disclosed. The processor-executable instructions stored in the computer-readable storage medium, when executed, are capable of causing a processor to implement the radio frequency energy deposition prediction method described above with respect to fig. 5.
Another computer-readable storage medium to store processor-executable instructions is also disclosed. The processor-executable instructions stored in the computer-readable storage medium, when executed, are capable of causing a processor to implement the rf energy deposition control method described above with respect to fig. 6.
Additionally, a computer device for magnetic resonance scanning is also disclosed, the computer device comprising any of the computer-readable storage media described above and a processor capable of executing processor-executable instructions stored in the computer-readable storage medium.
Although the present invention has been described with reference to the preferred embodiments, it is not intended to limit the present invention, and those skilled in the art can make variations and modifications of the present invention without departing from the spirit and scope of the present invention by using the methods and technical contents disclosed above.
Also, this application uses specific language to describe embodiments of the application. Reference throughout this specification to "one embodiment," "an embodiment," and/or "some embodiments" means that a particular feature, structure, or characteristic described in connection with at least one embodiment of the present application is included in at least one embodiment of the present application. Therefore, it is emphasized and should be appreciated that two or more references to "an embodiment" or "one embodiment" or "an alternative embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, some features, structures, or characteristics of one or more embodiments of the present application may be combined as appropriate.
Moreover, those skilled in the art will appreciate that aspects of the present application may be illustrated and described in terms of several patentable species or situations, including any new and useful combination of processes, machines, manufacture, or materials, or any new and useful improvement thereon. Accordingly, various aspects of the present application may be embodied entirely in hardware, entirely in software (including firmware, resident software, micro-code, etc.) or in a combination of hardware and software. Furthermore, aspects of the present application may be represented as a computer product, including computer readable program code, embodied in one or more computer readable media.
Computer program code required for the operation of various portions of the present application may be written in any one or more programming languages, including an object oriented programming language such as Java, Scala, Smalltalk, Eiffel, JADE, Emerald, C + +, C #, VB.NET, Python, and the like, a conventional programming language such as C, Visual Basic, Fortran 2003, Perl, COBOL 2002, PHP, ABAP, a dynamic programming language such as Python, Ruby, and Groovy, or other programming languages, and the like. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any network format, such as a Local Area Network (LAN) or a Wide Area Network (WAN), or the connection may be made to an external computer (for example, through the Internet), or in a cloud computing environment, or as a service, such as a software as a service (SaaS).
Additionally, the order in which elements and sequences of the processes described herein are processed, the use of alphanumeric characters, or the use of other designations, is not intended to limit the order of the processes and methods described herein, unless explicitly claimed. While various presently contemplated embodiments of the invention have been discussed in the foregoing disclosure by way of example, it is to be understood that such detail is solely for that purpose and that the appended claims are not limited to the disclosed embodiments, but, on the contrary, are intended to cover all modifications and equivalent arrangements that are within the spirit and scope of the embodiments herein. For example, although the system components described above may be implemented by hardware devices, they may also be implemented by software-only solutions, such as installing the described system on an existing server or mobile device.
Similarly, it should be noted that in the preceding description of embodiments of the application, various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure aiding in the understanding of one or more of the embodiments. This method of disclosure, however, is not intended to require more features than are expressly recited in the claims. Indeed, the embodiments may be characterized as having less than all of the features of a single embodiment disclosed above.
Numerals describing the number of components, attributes, etc. are used in some embodiments, it being understood that such numerals used in the description of the embodiments are modified in some instances by the use of the modifier "about", "approximately" or "substantially". Unless otherwise indicated, "about", "approximately" or "substantially" indicates that the number allows a variation of ± 20%. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximations that may vary depending upon the desired properties of the individual embodiments. In some embodiments, the numerical parameter should take into account the specified significant digits and employ a general digit preserving approach. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the range are approximations, in the specific examples, such numerical values are set forth as precisely as possible within the scope of the application.
Finally, it should be understood that the embodiments described herein are merely illustrative of the principles of the embodiments of the present application. Other variations are also possible within the scope of the present application. Thus, by way of example, and not limitation, alternative configurations of the embodiments of the present application can be viewed as being consistent with the teachings of the present application. Accordingly, the embodiments of the present application are not limited to only those embodiments explicitly described and depicted herein.
Claims (10)
1. A method of radio frequency energy deposition prediction for a magnetic resonance scan, the method comprising the steps of:
acquiring a multi-slice scanning sequence to be implemented to determine the frequency of each radio frequency excitation pulse contained in the multi-slice scanning sequence to be implemented;
retrieving and extracting from the data store pre-stored imaging volume absorption power factors corresponding respectively to each of the determined frequencies of the radio frequency excitation pulses;
obtaining from the data store pre-stored forward power values associated with each of the determined frequencies of the radio frequency excitation pulses, respectively, and calculating an imaging volume total absorption power value based on the extracted imaging volume absorption power factor and the forward power values;
and acquiring a prestored imaging body quality value from the data memory, and calculating a specific absorption rate predicted value aiming at the multi-slice scanning sequence to be implemented on the basis of the calculated total imaging body absorption power value and the imaging body quality value.
2. The method of claim 1, further comprising: the total power absorbed by the imaging volume is calculated according to the following formula: p ═ Σ k (i) × Pf(i) Where P is the total absorption power value of the imaging volume, k (i) is the absorption power factor of the imaging volume corresponding to the frequency of the ith RF excitation pulse, Pf(i) Is the forward power value associated with the frequency of the ith radio frequency excitation pulse, i being a positive integer.
3. The method of claim 2, further comprising: calculating the predicted value of specific absorption rate according to the following formula: and SAR is a specific absorption rate predicted value, P is a total absorption power value of the imaging body, and M is a quality value of the imaging body.
4. A radio frequency energy deposition control method for magnetic resonance scanning, the radio frequency energy deposition control method comprising the steps of:
performing the radio frequency energy deposition prediction method of any one of claims 1-3 to obtain a specific absorption rate prediction value prior to actually performing a multi-slice scan sequence to be performed;
and determining whether the multi-slice scanning sequence to be implemented is actually executed according to the specific absorption rate predicted value.
5. The radio frequency energy deposition control method for a magnetic resonance scan according to claim 4, the method further comprising: and driving a scanning execution mechanism to execute the multi-slice scanning sequence to be implemented under the condition that the predicted specific absorption rate value is less than a preset threshold value, and otherwise, postponing or terminating the execution of the multi-slice scanning sequence to be implemented.
6. The radio frequency energy deposition control method for a magnetic resonance scan according to claim 5, further comprising: an initialization operation is performed to build an imager model of a particular one of the imagers prior to a first execution of a multi-slice scan sequence for that imager, and an imager volume value is obtained from the imager model and stored in a data store.
7. The radio frequency energy deposition control method for a magnetic resonance scan according to claim 6, further comprising: a pre-scan operation is performed by transmitting rf calibration pulses prior to each performance of a multi-slice scan sequence to obtain rf characteristic data corresponding to respective operating frequencies over a predetermined rf bandwidth and to store the rf characteristic data in the data store.
8. The radio frequency energy deposition control method for a magnetic resonance scan according to claim 7, further comprising: calculating an imaging body absorption power factor corresponding to each of the respective operating frequencies within the predetermined radio frequency bandwidth range based on the radio frequency characteristic data after obtaining the radio frequency characteristic data;
wherein for each operating frequency, an imaging volume absorption power factor corresponding to the operating frequency is calculated according to:
k＝1–(Pr+Pcpl+Pother)/Pf，0<k<1
where k is the power factor absorbed by the imaging volume corresponding to the operating frequency, PrIs the reflected power, P, associated with the operating frequencycplIs the power loss of the coil, PfIs the forward power, P, associated with the operating frequencyotherOther power losses.
9. A computer readable storage medium for storing processor executable instructions, the processor executable instructions stored in the computer readable storage medium capable, when executed, of causing a processor to implement the radio frequency energy deposition control method of any one of claims 4 to 8.
10. A computer device comprising the computer-readable storage medium of claim 9 and a processor capable of executing processor-executable instructions stored in the computer-readable storage medium.
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