CN211014617U - Magnetic resonance imaging system - Google Patents
Magnetic resonance imaging system Download PDFInfo
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- CN211014617U CN211014617U CN201921785742.4U CN201921785742U CN211014617U CN 211014617 U CN211014617 U CN 211014617U CN 201921785742 U CN201921785742 U CN 201921785742U CN 211014617 U CN211014617 U CN 211014617U
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Abstract
The utility model provides a magnetic resonance imaging system, include: a main magnet assembly circumferentially forming a bore; a bed assembly operable to move into or out of the bore; and the local body transmitting coil is fixedly arranged on the inner wall of the hole cavity, and when the sickbed assembly is moved into the hole cavity, the local body transmitting coil is positioned below the sickbed assembly. The utility model provides a magnetic resonance imaging system can be applicable to the super high field, and it has shortened transmitting coil distance from the examinee through setting up transmitting coil in the latter half of the vestibule that the magnet formed, does benefit to and forms even radio frequency field in less scope; the transmission efficiency of the radio-frequency pulse transmitted by the transmitting coil is improved, and the duration time of the radio-frequency pulse is reduced.
Description
Technical Field
The utility model relates to a medical imaging technical field especially relates to a magnetic resonance imaging system.
Background
Magnetic Resonance Imaging (MRI) uses the Resonance characteristics of the Magnetic nuclei of a living body in a Magnetic fieldImaging technique for sexually performing imaging, which can utilize the main magnetic field (B) in a uniform manner0Field) hydrogen atoms precessing by larmor in a radio frequency field (B)1Field) excitation, using spatial encoding of gradient fields. The magnetic resonance imaging has the characteristics of no ionizing radiation, no damage, high resolution, high contrast, multi-parameter, cross section imaging in any direction and the like, so that the magnetic resonance imaging is widely applied to the field of medical imaging.
Magnetic resonance imaging systems are classified into low fields (below 0.5T), high fields (1.5T to 3.0T), and ultra high fields (greater than 3.0T) according to the magnetic field strength (T in Tesla) of a superconducting magnet. The signal-to-noise ratio of the ultrahigh-field magnetic resonance imaging system is obviously improved, the scanning speed is obviously accelerated, the image contrast is obviously enhanced, and the frequency spectrum effect is prominent, so that the ultrahigh-field magnetic resonance imaging system becomes a high-grade dual platform for clinical and scientific research, and is the fastest growing point of the future magnetic resonance market.
Along with the main magnetic field (B)0Field) field strength is increased, and the pulse power emitted by the radio frequency coil is increased. The energy carried by the rf pulse is released as heat and absorbed locally by the body, which may cause an increase in body temperature and even local thermal damage. This also causes the performance of the current ultra-high field magnetic resonance imaging system on Specific Absorption Rate (SAR) to be extremely insufficient. If a conventional Volume Coil (also called Volume Transmit Coil, VTC) is used in the ultra-high field magnetic resonance imaging system, the system will have a very high SAR, and there is no competitive advantage in terms of cost.
SUMMERY OF THE UTILITY MODEL
In view of the above, there is a need for an improved magnetic resonance imaging system which is suitable for ultra-high field magnetic resonance scanning and has a relatively low SAR and a competitive advantage in cost.
The utility model provides a magnetic resonance imaging system, include:
a main magnet assembly circumferentially forming a bore;
a bed assembly operable to move into or out of the bore;
it is characterized by also comprising:
and the local body transmitting coil is fixedly arranged on the inner wall of the hole cavity, and when the sickbed assembly is moved into the hole cavity, the local body transmitting coil is positioned below the sickbed assembly.
Further, a receiving coil and a control switch are arranged on the inner wall of the cavity, and the control switch is used for activating at least one of the local body transmitting coil and the receiving coil.
Further, the length of the receive coil is greater than the length of the local body transmit coil in the axial direction along the bore.
Further, the local body transmitting coil is provided with at least two scanning beds with different positions in the axial direction relative to the sickbed assembly, and the local body transmitting coil can scan different parts of the patient on different scanning beds.
Further, the local transmitting coil comprises a transmitting antenna, the transmitting antenna comprises a plurality of transmitting units distributed in an array, and the pulse amplitude and/or the pulse phase of each coil transmitting unit can be independently adjusted.
Further, the local body transmit coil comprises a tuning-out unit for tuning the local body transmit coil to a tuned-out state.
Further, the magnetic resonance imaging system further comprises a switch electrically connected to the local body transmitting coil, the switch being capable of switching the local body transmitting coil from a radio frequency transmitting coil to a radio frequency receiving coil.
Further, the magnetic resonance imaging system further comprises a body volume transmit coil disposed around the bore; the local body transmit coil can be adapted to the body volume transmit coil when used as a radio frequency receive coil.
Further, the magnetic resonance imaging system further includes a gradient coil assembly disposed around the bore, the gradient coil assembly for generating a gradient magnetic field.
Further, the local body transmit coil further comprises a radio frequency shielding device disposed between the transmit antenna and the gradient coil assembly.
The utility model provides a magnetic resonance imaging system can be applicable to the super high field, and it has shortened transmitting coil distance from the examinee through setting up transmitting coil in the latter half of the vestibule that the magnet formed, does benefit to and forms even radio frequency field in less scope; the transmission efficiency of the radio-frequency pulse transmitted by the transmitting coil is improved, and the duration time of the radio-frequency pulse is reduced.
Drawings
Fig. 1 is a schematic structural diagram of a magnetic resonance imaging system according to a first embodiment of the present invention;
figure 2 is a schematic view of the magnetic resonance imaging system of figure 1 in an operational state at another viewing angle;
FIG. 3 is a schematic diagram of the local body transmit coil of FIG. 1;
FIG. 4 is a schematic diagram of the structure of the receiving coil shown in FIG. 1;
fig. 5 is a schematic structural diagram of a magnetic resonance imaging system according to a second embodiment of the present invention;
figure 6 is a schematic view of the magnetic resonance imaging system of figure 5 at another viewing angle;
fig. 7 is a schematic diagram of an operating state of a local body transmitting coil according to an embodiment of the present invention.
Description of the main elements
| Magnetic |
100、100a |
| |
10 |
| |
11 |
| Radio |
20 |
| |
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| Sickbed component | |
| 30 | |
| Local |
40、40a |
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50 |
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60 |
The following detailed description of the invention will be further described in conjunction with the above-identified drawings.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.
It will be understood that when an element is referred to as being "mounted on" another element, it can be directly mounted on the other element or intervening elements may also be present. When a component is referred to as being "disposed on" another component, it can be directly on the other component or intervening components may also be present. When an element is referred to as being "secured to" another element, it can be directly secured to the other element or intervening elements may also be present.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "or/and" includes any and all combinations of one or more of the associated listed items.
Referring to fig. 1 to 2, fig. 1 is a schematic structural diagram of a magnetic resonance imaging system 100 according to a first embodiment of the present invention, and fig. 2 is a schematic structural diagram of the magnetic resonance imaging system 100 shown in fig. 1 in a working state under another viewing angle.
The utility model provides a Magnetic Resonance Imaging system 100 (MRI), it is through utilizing at even main field (B)0Field) hydrogen atoms precessing by larmor in a radio frequency field (B)1Field) excitation, and spatial encoding of gradient fields is used to achieve imaging.
The magnetic resonance imaging system 100 can obtain medical images containing various physiological information of a living body, thereby providing an auxiliary aid for diagnosis and treatment of the living body. The magnetic resonance imaging has the characteristics of no ionizing radiation, no damage, high resolution, high contrast, multi-parameter, cross section imaging in any direction and the like, so that the magnetic resonance imaging is widely applied to the field of medical imaging.
In this embodiment, the magnetic resonance imaging system 100 is a human magnetic resonance imaging system, and the imaging aperture is preferably 60 to 80 cm. It is to be understood that in other embodiments the magnetic resonance imaging system 100 may also be used as an animal magnetic resonance imaging system, in which case the imaging aperture is preferably 16 to 40 cm.
The magnetic resonance imaging system 100 includes a main magnet assembly 10, a gradient coil assembly (not shown), a radio frequency coil assembly 20, a spectrometer (not shown), and a computer device (not shown). The main magnet assembly 10 is used to generate a uniform static magnetic field; the gradient coil assembly is used for generating a linear gradient field so as to provide spatial encoding for the whole magnetic field; the radio frequency coil assembly 20 is used for transmitting radio frequency pulses and receiving radio frequency pulse signals; the spectrometer acts as a control center for controlling the coordination among the main magnet assembly 10, the gradient coil assembly, and the radio frequency coil assembly 20; the computer device is used to process and synthesize the image information received by the radio frequency coil assembly 20.
Under the control of the spectrometer, the main magnet assembly 10 generates a uniform and strong basic static magnetic field, the gradient coil assembly makes the spatial information of the whole magnetic field known, and the radio frequency coil assembly transmits a radio frequency pulse signal, so that hydrogen nuclei in the organism are converted from a spin low energy state in the original static magnetic field to a high energy state having both longitudinal and transverse magnetization vector components by absorbing photons (electromagnetic waves). After the radio frequency pulse signal is turned off, the hydrogen atomic nucleus can be slowly restored to a dynamic equilibrium state. The image information including the biological physiological information is obtained by collecting echo signals generated in the hydrogen atomic nuclear spin relaxation process and synthesizing the echo signals by computer equipment.
The main magnet assembly 10 is disposed around and forms a bore 11, and the bore 11 is used for the patient bed assembly 30 to extend into, so that the patient bed assembly 30 can move in or out along the axial direction of the bore 11 in the bore 11. The main magnet assembly 10 includes a main magnet (not shown) and shim pieces (not shown) disposed thereon. The main magnet is used for generating a uniform and strong static magnetic field, and the shim pieces are used for further homogenizing the static magnetic field generated by the main magnet.
In this embodiment, the superconducting magnet is selected as the main magnet in consideration of the fact that the superconducting magnet can generate a stronger and more uniform magnetic field. As for the structure of the superconducting magnet itself, it may adopt a conventional structure. The superconducting magnet includes superconducting main coils (not shown), a superconducting shield coil (not shown), and a dewar (not shown). The superconducting main coil and the superconducting shielding coil can be formed by winding niobium-titanium (NbTi) wires and other low-temperature superconducting wires, and a large amount of refrigerants (such as liquid helium) are stored in a Dewar flask and provide a constant low-temperature superconducting environment (such as 4.2K) for the whole superconducting magnet; the superconducting main coils and the shield coils generate a uniform static magnetic field by the magnetic field effect of a strong current.
It is understood that in other embodiments, the main magnet may also be a permanent magnet, in which case the main magnet mainly uses high remanence materials such as rare earth alloy to generate the static magnetic field.
The gradient coil assembly is used to generate a uniform linear gradient magnetic field in the imaging region to spatially encode data. The gradient coil assembly includes a gradient coil, a gradient waveform generator, and a conditioning circuit.
In particular, the gradient coils are typically formed by three sets of x, y, z gradient coils for generating a direction and a main magnetic field (B)0Field) direction is the same, but the magnetic field strength varies linearly in the three directions x, y, z, respectively. The gradient coil assembly generates a homogeneous gradient magnetic field by the superposition of one gradient coil or a plurality of gradient coils.
The gradient amplifier is used to amplify gradient currents, which can be fed to the gradient coil with amplified currents according to nominal gradient currents, thereby enabling the gradient coil to generate a gradient magnetic field. Since the gradient waveforms generated by the gradient waveform generator tend to deviate from the ideal square waveform, the gradient coil assembly is provided with a conditioning circuit to level the gradient waveforms.
The rf coil assembly 20 includes a plurality of rf coils (not shown), some of which are transmit coils and some of which are receive coils. Each rf coil is provided with an rf power amplifier (not shown) and an analog-to-digital converter (not shown) connected correspondingly. One end of the radio frequency power amplifier is electrically connected with the radio frequency coil, and the other end is electrically connected with the spectrometer. One end of the analog-to-digital converter is electrically connected with the radio frequency coil, and the other end of the analog-to-digital converter is electrically connected with the spectrometer.
The spectrometer is electrically connected to the rf coil assembly 20 and the gradient coil assembly for controlling the rf coil assembly to generate a rf magnetic field and controlling the gradient coil assembly to generate a gradient magnetic field. The spectrometer includes one or more of a pulse sequencer, a gradient waveform generator, a transmitter and a receiver (not shown).
The computer device is used for controlling the operation of the magnetic resonance imaging system and the final magnetic resonance imaging, is in communication connection with the spectrometer and is used for transmitting scanning sequence instructions to the spectrometer so as to control the operation of the magnetic resonance imaging system and generate magnetic resonance images.
Further, a patient bed assembly 30 is disposed in the magnetic resonance imaging system 100, and the patient bed assembly 30 is located in the bore 11 surrounded by the main magnet assembly 10 and is operable to move in and out of the bore 11 along an axial direction of the bore 11. The patient is fixed on the patient bed assembly 30 in a lying posture and the like, and then is scanned by the gradient coil assembly and the radio frequency coil assembly 20, so that the complete examination process can be completed.
It is understood that other functional auxiliary components such as a water cooling system may be further disposed in the magnetic resonance imaging system 100 to improve the detection performance of the magnetic resonance imaging system 100. These functional auxiliary components are not the focus of the present invention, and are not described herein.
When the magnetic field strength (taking Tesla as a unit, referred to as T for short) of a main magnet is increased to more than 3.0T, that is, when the magnetic resonance imaging system is an ultrahigh-field magnetic resonance imaging system, along with the increase of the field strength of a magnetic resonance main magnetic field, the power of radio-frequency pulses is increased, and energy complicated by radio-frequency excitation pulses is released in the form of heat and is locally absorbed by a human body, so that the body temperature is increased. Therefore, high field magnetic resonance systems are prone to local thermal damage, especially during spinal scans.
The utility model provides a magnetic resonance imaging system 100 is in order to promote the excitation efficiency of radio frequency pulse under the super high field operating mode, regard the body volume coil that conventional backbone scanning adopted as the transmission excitation, adjust to local body transmitting coil as the transmission excitation, thereby reduced the distance between transmitting coil and the human body, need not to adopt more powerful radio frequency pulse when high field intensity formation of image, thereby reduce the deposit of radio frequency power in the human body, improve radio frequency pulse's excitation efficiency, avoid the local thermal damage in the high field magnetic resonance formation of image; the intensity of a local radio frequency field formed by the transmitting coil in a human body area is improved, the local imaging visual field propyne is more accurately excited to obtain higher uniformity of the radio frequency field, and signal pollution/convolution artifacts caused by peripheral tissue signals are reduced to the greatest extent; the emission energy of the radio frequency pulse can be reduced, the radio frequency radiation dose of a patient is reduced, and the inspection safety is improved; the short echo acquisition time is adopted, the scanning speed and the imaging effect of imaging are improved, and the scanning comfort of a patient is improved.
Specifically, the magnetic resonance imaging system 100 further comprises a local body transmit coil 40, the local body transmit coil 40 is fixedly disposed on an inner wall of the bore 11, specifically within a lower half of the bore 11, and the local body transmit coil 40 is located below the couch assembly 30 when the couch assembly 30 is moved into the bore 11 by the local body transmit coil 40. The local body transmit coil 40 transmits radio frequency pulses and excites hydrogen atoms in the patient, thereby generating a magnetic resonance phenomenon.
The use of a smaller Volume local body Transmit Coil 40 as the Transmit Coil and the placement of the local body Transmit Coil 40 on the inner wall of the bore 11 and below the couch assembly 30 allows the local body Transmit Coil 40 to be closer to the body than a conventional Volume Transmit Coil (VTC). At this time, the smaller the rated transmitting power required by the local transmitting coil 40 is, the smaller the amount of magnetic field deposited on the human body is, the lower the SAR parameters are, and the higher the SAR performance of the system is.
In this embodiment, the magnetic resonance imaging system is a horizontal magnetic resonance imaging system. It will be appreciated that in other embodiments the magnetic resonance imaging system may also employ other types of magnetic resonance imaging systems than the prone type.
Optionally, the relative distance of the local body transmit coil 40 and/or the patient bed assembly 30 within the bore 11 is adjustable. For example, the height of the bed assembly 30 in the vertical direction inside the bore 11 can be adjusted, and the bed assembly 30 can actually adjust the position of the patient according to the size of the patient, so that the patient can reach the optimal scanning area. As another example, a plurality of detents are provided on the inner wall of the bore 11, and the local body transmit coil 40 is mounted in a different detent to allow for vertical adjustment. The distance between the local body emitting coil 40 and the sickbed is adjusted according to the requirements aiming at the examinees with different body types and different age groups, so that the optimal scanning effect is obtained, and the safety of the equipment is improved.
In one embodiment, scout images of the subject in the sagittal or coronal positions may be first acquired; determining a plurality of imaging field of view regions of a subject body region from the anatomical region of interest reflected on the scout image; the scanning part in each imaging visual field area has difference in vertical direction, such as the thickness of the abdomen is higher than that of the lower limb; the chest region of the patient is higher than the neck region; according to the position of the scanning part in the vertical direction in each imaging visual field area, the position of the local body transmitting coil 40 relative to the sickbed is adjusted, so that the imaging effect in each imaging visual field area is optimal.
Further, the magnetic resonance imaging system 100 further includes a receiving coil 50 and a control switch (not shown), wherein the receiving coil 50 is disposed on the patient bed assembly 30 and is used for receiving the nuclear spin signal of the hydrogen atom, so as to implement the detection of the magnetic resonance phenomenon; the control switch is used to activate the local transmit coil 40 and/or receive coil 50.
In one embodiment, a slot may be provided on the patient bed assembly 30, a positioning circuit is provided in the slot, and the positioning circuit is connected to the control switch, when the receiving coil 50 is inserted into the slot, the positioning circuit is triggered to be activated, and the patient bed automatically controls to move the receiving coil 50 into the rf field area formed by the local body transmitting coil 40. In the embodiment of the application, the fixing and the positioning of the receiving coil are completed at one time, and the clinical positioning workflow is simplified.
In one embodiment, the surface of the arcuate structure formed by the local body transmit coil 40 is further provided with an inductor coupled to the local body transmit coil 40 for frequency selective filtering of the radio frequency pulses transmitted by the local body transmit coil 40. The inductor can realize the following functions: radio frequency notching to remove common mode radio frequency signals transmitted by the substantially planar local body transmit coil 40; selectively decoupling the substantially planar local body transmit coil 40 during a radio frequency transmit phase; or to impedance match the electronics connecting the local body transmit coil 40 to the radio frequency cable.
In one embodiment, the local body transmit coil 40 comprises a plurality of radio frequency coils forming a radio frequency array and a housing encasing the radio frequency array, the housing having an arcuate surface of about 5 ° -10 °, each radio frequency coil being connected to a radio frequency power amplifier, each transmit coil being independently controlled, and each transmit coil being drivable by a corresponding radio frequency power amplifier to control the phase and amplitude of the radio frequency pulses.
Optionally, the local body transmit coil 40 may further include a radio frequency shield, which may be disposed between the main magnet assembly 10 and the radio frequency array or between the gradient coil assembly and the radio frequency array, for shielding the plurality of radio frequency transmit coils from interaction with the magnet cryostat (not shown) of the main magnet assembly 10 and the gradient coil unit (not shown) of the gradient coil assembly.
Alternatively, the housing comprises an upper housing and a lower housing, and the two housings form a sealed structure, and the radio frequency shielding device can be arranged on the inner surface or the outer surface of the sealed structure, and the radio frequency array is accommodated in the sealed structure. Considering that the local body transmitting coil 40 is a high power component, it itself generates much heat, which causes the device temperature to rise, and too high a temperature may cause the device to be damaged. In the embodiment of the application, the two ends of the shell are respectively provided with the inlet and the outlet which are communicated with the sealing structure, the heat of the radio frequency array can be taken away by inputting cooling media such as water, air and the like to the inlet, and the cooling media after heat exchange flows out from the outlet. In the embodiment of the application, the cooling structure is arranged on the shell, so that the heat dissipation problem of the radio frequency array is well solved, and the stability of the system is improved.
In practical applications, the local body transmitting coil 40 transmits a radio frequency signal first, after the hydrogen nuclei in the patient are converted into a high energy state by absorbing the radio frequency energy (electromagnetic wave) transmitted by the local body transmitting coil 40, the local body transmitting coil 40 is turned off, the receiving coil 50 is turned on and detects an echo signal generated during the spin relaxation of the hydrogen nuclei, thereby completing the imaging process.
Referring to fig. 3 to 4 together, fig. 3 is a schematic structural diagram of the local body transmitting coil 40 shown in fig. 1, and fig. 4 is a schematic structural diagram of the receiving coil 50 shown in fig. 1.
The local body transmit coil 40 comprises a transmit antenna comprising a plurality of transmit elements arranged in an array, and the pulse amplitude and/or pulse phase of each coil transmit element can be independently adjusted.
With this arrangement, the local body transmitting coil 40 has relatively better transmitting performance, and the performance of signal transmission between the local body transmitting coil 40 and the receiving coil 50 is more excellent.
In this embodiment, the transmit antenna of the local body transmit coil 40 is formed by a linear array of four independent loop coil (L oopCoil) transmit elements, each serving as a transmit channel, it being understood that the transmit antenna of the local body transmit coil 40 may take other arrangements than those described above, so long as the local body transmit coil 40 is able to successfully transmit the radio frequency signal.
The receiver coil 50 includes a plurality of coil receiving units arranged in rows and columns and forming the receiver coil 50.
In the present embodiment, the receiving coil 50 is formed by an array of twenty-four loop coil receiving units, which is arranged in six rows and four columns. Of course, the receiving coil 50 may also adopt other arrangements such as eight rows and three columns to form twenty-four transmitting unit arrays.
The twenty-four loop coil receiving units are provided, so that the receiving coil 50 has better receiving capability and higher cost performance, and the performance of signal transmission between the local body transmitting coil 40 and the receiving coil 50 is also better.
It will be appreciated that the receive coil 50 may also employ other numbers of loop coil receive units than those described above; the local transmit coil 40 and receive coil 50 may also employ other types of coils besides ring coils, such as transverse electromagnetic radio frequency coils (TEMs).
In one embodiment of the present invention, the length of the receiving coil 50 is greater than the length of the local body transmitting coil 40 in the axial direction along the bore. So configured, the receive coil 50 can extend beyond the length of the patient's spine, and the receive coil 50 can receive the radio frequency signals emitted by the local body transmit coil 40 without loss and over a full range.
It should be noted that the lengths of the local body transmitting coil 40 and the receiving coil 50 refer to the lengths of the local body transmitting coil 40 and the receiving coil 50 in the extending direction of the patient bed assembly 30, i.e. the axial lengths thereof.
In one embodiment of the present invention, the local body transmitting coil 40 has at least two scanning beds with different positions in the axial direction relative to the patient bed assembly 30, and the local body transmitting coil 40 can scan different parts of the patient on different scanning beds.
At this time, the length of the local body emitting coil 40 is designed to be smaller than the length of the spine of the patient, and the local body emitting coil 40 needs to pass through two scanning beds to completely scan the spine of the patient, so that the scanning function of the large-scale coil is realized by the relatively miniaturized local body emitting coil 40 in a multi-station measurement mode, and meanwhile, the cost of the local body emitting coil 40 and the number of control accessories such as control switches needing to be arranged are reduced, and the load on the whole system is further reduced.
In specific application, a patient and a sickbed assembly 30 extend into the cavity 11 together, different scanning beds are formed between the sickbed assembly 30 and the local body transmitting coil 40 by adjusting the position of the sickbed assembly 30, and the local body transmitting coil 40 is miniaturized by multi-station measurement.
In the present embodiment, the local body transmission coil 40 has two scanning beds. It is understood that in other embodiments, the local body transmit coil 40 may also have three and more than three scanning beds. The larger number of scanning beds are arranged, so that the volume required by the local body transmitting coil 40 can be further reduced, and the cost is further reduced.
In one embodiment of the present invention, the local body transmitting coil 40 further has a detuning unit (not shown) for tuning the local body transmitting coil 40 to a detuned state when other coils are used as transmitting coils in the magnetic resonance imaging system 100, so as to couple with other coils.
In one embodiment of the present invention, the local body transmitting coil 40 has four mutually independent transmitting channels (not shown), and the amplitude and phase between the four transmitting channels can be adjusted relatively independently. The local transmitting coil 40 has relatively better transmitting performance, relatively lower cost, and more outstanding cost performance advantage.
In one embodiment of the present invention, the magnetic resonance imaging system 100 further comprises an abdominal coil (not shown) corresponding to the abdominal position of the patient and used with the local body transmitting coil 40, and the receiving coil 50 disposed on the patient bed is used to receive the magnetic resonance signal emitted from the abdomen in combination with the abdominal coil.
Referring to fig. 5 and fig. 6 together, fig. 5 is a schematic structural diagram of a magnetic resonance imaging system 100a according to a second embodiment of the present invention, and fig. 6 is a schematic structural diagram of the magnetic resonance imaging system 100a shown in fig. 5 under another view angle.
Considering that the pulse transmits and receives the resonance signals of the nuclei of the biological tissue at different times, and the frequency of the radio frequency pulse is the same as that of the resonance signals generated by the biological tissue, one coil can be used for both transmission and reception. The second embodiment of the present invention is different from the first embodiment of the present invention in that the local body transmitting coil 40a in the second embodiment of the present invention is used as both a transmitting coil and a receiving coil, i.e., as a transmitting-receiving integrated coil.
In particular, the magnetic resonance imaging system 100a further includes a switch (not shown) electrically connected to the local body transmit coil 40a for switching the local body transmit coil 40 from the radio frequency transmit coil to the radio frequency receive coil.
In practice, the local body transmitting coil 40a first gives the tissue a radio frequency pulse excitation with a frequency consistent with the precession frequency of the hydrogen protons, the hydrogen protons in the tissue at a low energy level will absorb the energy of the radio frequency pulse and transition to a high energy level state, for example, the energy of the radio frequency pulse can deflect the macroscopic longitudinal magnetization vector of the tissue by 90 degrees, can deflect to the X, Y plane and generate a maximum rotational macroscopic transverse magnetization vector, and the receiving coil can acquire the rotational macroscopic transverse magnetization vector and generate an electrical signal (actually, the original magnetic resonance signal). In one embodiment, the higher the tissue proton density, the larger the macroscopic transverse magnetization vector generated after the radio frequency pulse excitation, the stronger the electrical signal generated by the cutting receiving coil, and the higher the MR signal; conversely, the lower the tissue proton density, the smaller the rotational macroscopic transverse magnetization vector generated after the radio frequency pulse excitation, and the weaker the electrical signal generated by the cutting receiving coil, the lower the MR signal. .
With the above arrangement, the transmitting and receiving functions of the local transmitting coil 40a are integrated, so that the magnetic resonance imaging system 100a does not need to additionally provide a receiving coil during spine scanning, and the cost is further reduced.
Referring to fig. 7, fig. 7 is a schematic diagram illustrating an operating state of the local body transmitting coil 40a according to an embodiment of the present invention. In one embodiment, the local body transmitting coil 40a is further connected to an electrocardiographic identification device 60. the electrocardiographic identification device 60 includes a sensor array comprising sensors which are attachable to the anterior left region of the patient's chest and are connected to the local body transmitting coil 40 a. Optionally, the electrocardiograph 60 may automatically calculate the maximum point potential difference between the leads, determine the sensor corresponding to the available lead signal, and send the available lead signal to the processor to obtain the cardiac motion signal. Of course, the acquisition of the cardiac motion signal may also be based on a deep learning approach: the processor receives signals sent by the sensor array and determines heart motion signals detected by the effectively monitored sensors by using the trained neural network. The system controls the local body transmit coil 40a to transmit radio frequency pulses based on the heart motion signal, e.g., controls the local body transmit coil 40a to transmit radio frequency pulses only when the system detects that the heart motion signal is within a set threshold, and controls the local body transmit coil 40a to turn off when the system detects that the heart motion signal is outside the set threshold.
Further, the magnetic resonance imaging system 100a also includes a body volume transmit coil 21a, the body volume transmit coil 21a being disposed around the bore 11; the local body transmit coil 40a, when functioning as a radio frequency receive coil, can be adapted to the body volume transmit coil 21 a.
At this time, the body volume transmitting coil 21a serves as a transmitting coil, and the local body transmitting coil 40a serves as a receiving coil, thereby completing the transmitting and receiving process of the radio frequency signal.
Since the local body transmitting coil 40a provided in the second embodiment of the present invention is not used in combination with the abdomen coil, the number of receiving units of the local body transmitting coil 40a can be relatively reduced.
The following briefly describes the imaging procedure of the magnetic resonance imaging system:
s100, the computer equipment stores and sends a scanning sequence (scan sequence) instruction to be executed to the spectrometer.
S200, a pulse sequence generator in the spectrometer controls a gradient waveform generator and a transmitter according to a scanning sequence instruction, and the gradient waveform generator outputs a gradient pulse signal with a preset time sequence and a preset waveform.
S300, the gradient pulse signals pass through gradient current amplifiers in the Gx, Gy and Gz directions and then pass through three independent channels Gx, Gy and Gz in the gradient coil assembly, and each gradient current amplifier excites a corresponding gradient coil in the gradient coil assembly to generate a gradient magnetic field for generating corresponding spatial coding signals so as to spatially locate the magnetic resonance signals.
S400, the pulse sequence generator in the spectrometer executes a scanning sequence and outputs data including timing, strength, shape and the like of radio-frequency transmitted radio-frequency pulses and timing of radio-frequency reception and the length of a data acquisition window to the transmitter.
S500, the transmitter sends a radio frequency pulse to the radio frequency transmit coil to generate a B1 field (i.e., a radio frequency magnetic field).
S600, signals emitted by the excited atomic nuclei in the patient body under the action of the B1 field are sensed by a radio frequency receiving module comprising a receiving coil and are transmitted to a radio frequency power amplifier for amplification through a transmitting/receiving switch.
And S700, the amplified magnetic resonance signal is subjected to one or more of demodulation, filtering and AD conversion by an analog-to-digital converter, and then is transmitted to a storage module of the computer equipment. After the storage module acquires a set of raw k-space data, the scan is finished.
The utility model provides a magnetic resonance imaging system can be suitable for the super high field, it reduces the axial length demand of backbone coil through the mode that regards backbone coil as transmitting coil to scan many times; the SAR numerical value is reduced, the excitation efficiency of the system radio frequency pulse is improved, and the problem of local overheating caused by overhigh frequency of the adopted radio frequency pulse in the high field in the prior art is solved.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
It will be appreciated by those skilled in the art that the above embodiments are only for illustrating the present invention and are not to be taken as limiting the present invention, and that suitable modifications and variations of the above embodiments are within the scope of the invention as claimed.
Claims (10)
1. A magnetic resonance imaging system comprising:
a main magnet assembly circumferentially forming a bore;
a bed assembly operable to move into or out of the bore;
it is characterized by also comprising:
and the local body transmitting coil is fixedly arranged on the inner wall of the hole cavity, and when the sickbed assembly is moved into the hole cavity, the local body transmitting coil is positioned below the sickbed assembly.
2. The magnetic resonance imaging system of claim 1, wherein the inner wall of the bore is further provided with a receive coil and a control switch for activating at least one of the local body transmit coil and the receive coil.
3. The magnetic resonance imaging system of claim 2, wherein the length of the receive coil is greater than the length of the local body transmit coil in the axial direction along the bore.
4. The magnetic resonance imaging system of claim 1, wherein the local body transmit coil has at least two scanning beds that differ in position axially relative to the couch assembly, the local body transmit coil being capable of scanning different portions of the patient at different scanning beds.
5. The magnetic resonance imaging system of claim 1, wherein the local volume transmit coil comprises a transmit antenna comprising a plurality of transmit elements distributed in an array, and wherein the pulse amplitude and/or pulse phase of each coil transmit element can be independently adjusted.
6. The magnetic resonance imaging system of claim 1, wherein the local body transmit coil includes a detuning unit for tuning the local body transmit coil to a detuned state.
7. The magnetic resonance imaging system of claim 1, further comprising a switch electrically connected to the local body transmit coil, the switch capable of switching the local body transmit coil from a radio frequency transmit coil to a radio frequency receive coil.
8. The magnetic resonance imaging system of claim 7, further comprising a body volume transmit coil disposed around the bore; the local body transmit coil can be adapted to the body volume transmit coil when used as a radio frequency receive coil.
9. The magnetic resonance imaging system of claim 5, further comprising a gradient coil assembly disposed around the bore, the gradient coil assembly for generating gradient magnetic fields.
10. The magnetic resonance imaging system of claim 9, wherein the local body transmit coil further includes a radio frequency shield disposed between the transmit antenna and the gradient coil assembly.
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| CN201921785742.4U CN211014617U (en) | 2019-10-23 | 2019-10-23 | Magnetic resonance imaging system |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112307657A (en) * | 2020-09-22 | 2021-02-02 | 山东大学 | Superconducting magnetic resonance magnet for neonatal imaging and design method |
| CN113109748A (en) * | 2021-05-08 | 2021-07-13 | 苏州众志医疗科技有限公司 | Radio frequency device for magnetic resonance imaging and magnetic resonance imaging system |
| CN114252826A (en) * | 2020-09-21 | 2022-03-29 | 西门子(深圳)磁共振有限公司 | Bed assembly of magnetic resonance imaging device and magnetic resonance imaging device |
| WO2023141324A1 (en) * | 2022-01-21 | 2023-07-27 | The Trustees Of Columbia University In The City Of New York | Magnetic resonance apparatus, computer-accessible medium, system and method for use thereof |
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2019
- 2019-10-23 CN CN201921785742.4U patent/CN211014617U/en active Active
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114252826A (en) * | 2020-09-21 | 2022-03-29 | 西门子(深圳)磁共振有限公司 | Bed assembly of magnetic resonance imaging device and magnetic resonance imaging device |
| CN112307657A (en) * | 2020-09-22 | 2021-02-02 | 山东大学 | Superconducting magnetic resonance magnet for neonatal imaging and design method |
| CN112307657B (en) * | 2020-09-22 | 2023-03-17 | 山东大学 | Superconducting magnetic resonance magnet for neonatal imaging and design method |
| CN113109748A (en) * | 2021-05-08 | 2021-07-13 | 苏州众志医疗科技有限公司 | Radio frequency device for magnetic resonance imaging and magnetic resonance imaging system |
| WO2023141324A1 (en) * | 2022-01-21 | 2023-07-27 | The Trustees Of Columbia University In The City Of New York | Magnetic resonance apparatus, computer-accessible medium, system and method for use thereof |
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