CN105572612B - A method of improving Multi-channel radio-frequency coil performance - Google Patents
A method of improving Multi-channel radio-frequency coil performance Download PDFInfo
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- CN105572612B CN105572612B CN201511027258.1A CN201511027258A CN105572612B CN 105572612 B CN105572612 B CN 105572612B CN 201511027258 A CN201511027258 A CN 201511027258A CN 105572612 B CN105572612 B CN 105572612B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
- G01R33/32—Excitation or detection systems, e.g. using radio frequency signals
- G01R33/36—Electrical details, e.g. matching or coupling of the coil to the receiver
- G01R33/3642—Mutual coupling or decoupling of multiple coils, e.g. decoupling of a receive coil from a transmission coil, or intentional coupling of RF coils, e.g. for RF magnetic field amplification
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
- G01R33/48—NMR imaging systems
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F5/00—Coils
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Abstract
A method of improving Multi-channel radio-frequency coil performance, comprising the following steps: before magnetic resonance imaging, magnetic Meta Materials are added in Multi-channel radio-frequency coil；In the case where no radio-frequency emission power, the noise in each channel in the Multi-channel radio-frequency coil is acquired；Calculate the noise coupling matrix of the Multi-channel radio-frequency coil after the magnetic Meta Materials are added；In image reconstruction process, Multi-channel radio-frequency coil coupling is compensated using the noise coupling matrix.A kind of method improving Multi-channel radio-frequency coil performance provided by the invention, by each channel noise of acquisition Multi-channel radio-frequency coil and its noise coupling matrix is calculated, and deteriorated in image reconstruction using the coupling of noise coupling matrix compensation Multi-channel radio-frequency coil, to realize the purpose for promoting Multi-channel radio-frequency coil performance when magnetic Meta Materials are added in Multi-channel radio-frequency coil, the signal-to-noise ratio and image resolution ratio of image are improved, picture quality is promoted.
Description
Technical field
The present invention relates to magnetic resonance imaging more particularly to a kind of methods for improving Multi-channel radio-frequency coil performance.
Background technique
Meta Materials performance mainly passes through the description of the electromagnetic parameters such as dielectric constant, magnetic conductivity and refractive index.And magnetic Meta Materials
The Meta Materials of magnetic response are generated to electromagnetic field for micro-structure, it has the characteristics that can manual control magnetic conductivity.Magnetic Meta Materials are logical
Magnetic resonance structure (such as split ring resonator) and its distressed structure are crossed to realize the adjusting to equivalent permeability.When electromagnetic wave enters
When penetrating, split ring resonator can form equivalent LC resonance circuit in the structure, to be realized by magnetic resonance to electromagnetic wave
Control and constraint, to electromagnetic field realize reinforcing effect.
Currently, magnetic Meta Materials are used widely in RF application, especially in magnetic resonance imaging (Magnetic
Resonance Imaging, MRI) in application.Those skilled in the art using magnetic Meta Materials devise applied to magnetic resonance at
The micro-structure of picture, this kind of micro-structure are the multilayer cylindrical body that aluminium foil is rolled into, wherein aluminium foil with a thickness of 50 μm, multilayer cylindrical body
Diameter 10mm, length 200mm, the multilayer cylindrical body by every side be 10 in a manner of rearrange into a hexagonal structure.It should
The resonant frequency of micro-structure based on magnetic Meta Materials is that 21.3MHz puts the micro-structure applied to the MRI machine of 0.5T type
It is placed between imaging object and radio-frequency coil, the effect of guidance magnetic flux may be implemented, improve image quality.In addition, this field skill
A kind of split ring resonator of three-dimensional structure, the external high-precision (± 1%) of each split ring resonator has also been devised in art personnel
Capacitor achievees the purpose that required frequency.The split ring resonator is made of micro structure array, diameter 15mm, and resonant frequency is
63.28Mhz, the MRI machine applied to 1.5T type.
Although showing that resonance image quality and resolution ratio can be improved in magnetic Meta Materials in an experiment.However, facing
In bed application, when split ring resonator is inserted into Multi-channel radio-frequency coil, the mutual inductance that will lead between each unit coil becomes
To change, main cause are as follows: unit coil carries out Decoupling design under conditions of not accounting for being added magnetic Meta Materials, so that plus
Enter the decoupling effect decline after magnetic Meta Materials between coil unit, causes the performance of Multi-channel radio-frequency coil to decline, Bu Nengqi
To the effect for promoting picture quality.
Summary of the invention
The present invention is to solve the technical problems existing in the prior art, provides and a kind of improves Multi-channel radio-frequency coil performance
Method reduces the coupling between multi-channel coil, and solve to be declined using the Multi-channel radio-frequency coil performance of magnetic Meta Materials is asked
Topic, to improve resonance image quality and resolution ratio.
A method of improving Multi-channel radio-frequency coil performance, comprising the following steps:
(1) before magnetic resonance imaging, magnetic Meta Materials are added in Multi-channel radio-frequency coil；
(2) in the case where no radio-frequency emission power, the multi-channel radio frequency line is acquired on magnetic resonance imaging system
The noise image m in each channel in circlei(), wherein 1≤i≤L, L indicates the port number of multi-channel coil here.
(3) the noise coupling matrix Ψ of the Multi-channel radio-frequency coil after the magnetic Meta Materials are added is calculated；
(4) in image reconstruction process, the Multi-channel radio-frequency coil is coupled using the noise coupling matrix and is carried out
Compensation.
Further, the sampled point of noise image described in step (2) is greater than 10,000.
Further, the calculation formula of noise coupling matrix described in step (3) are as follows:Its
In, mi() indicates the noise image of i-th of channel acquisition,Indicate mj(r) conjugate transposition, 1≤i, j≤L, here L
Indicate the port number of multi-channel coil.
Further, the formula of image reconstruction described in step (4) are as follows:The I is indicated after rebuilding
Image.
Further, S is the acquisition image in each channel in the formula that described image is rebuild, and C is multi-channel radio frequency line
The sensitivity distribution of circle.
Further, when C is equal to S, the simplified formula of image reconstruction isThe I indicates to rebuild
Image afterwards.
Further, the magnetic Meta Materials are split ring resonator.
Beneficial effects of the present invention:
In conclusion a kind of method for improving Multi-channel radio-frequency coil performance provided by the invention, by acquiring multichannel
Simultaneously its noise coupling matrix is calculated in each channel noise of radio-frequency coil, and is mended in image reconstruction using noise coupling matrix
The coupling for repaying Multi-channel radio-frequency coil deteriorates, and promotes multichannel to realize when magnetic Meta Materials are added in Multi-channel radio-frequency coil
The purpose of radio-frequency coil performance improves the signal-to-noise ratio and image resolution ratio of image, promotes picture quality.
Detailed description of the invention
Fig. 1 is the flow chart for the method that the embodiment of the present invention improves Multi-channel radio-frequency coil performance.
Fig. 2 is Multi-channel radio-frequency coil experimental apparatus for capability structural schematic diagram of the embodiment of the present invention.
Fig. 3 is Multi-channel radio-frequency coil noise coupling matrix calculation result figure of the embodiment of the present invention.
Fig. 4 (a) is the signal-to-noise ratio figure before Multi-channel radio-frequency coil of the embodiment of the present invention does not compensate；It (b) is implementation of the present invention
Signal-to-noise ratio figure after example Multi-channel radio-frequency coil compensation.
Specific embodiment
In order to preferably illustrate technical characterstic and structure of the invention, below in conjunction with the preferred embodiment of the present invention and its attached
Figure is described in detail.
Refering to fig. 1, a method of improving Multi-channel radio-frequency coil performance, comprising the following steps:
(S1) before magnetic resonance imaging, magnetic Meta Materials are added in Multi-channel radio-frequency coil；Multi-channel coil is
One coil has multiple channels, receives signal respectively.For example: 8 channel radio frequency coils, it includes 8 channels, this 8 logical
Road can be respectively intended to receive signal.
(S2) it in the case where no radio-frequency emission power, is acquired in Multi-channel radio-frequency coil on magnetic resonance imaging system
The noise image in each channel.
(S3) the noise coupling matrix of the Multi-channel radio-frequency coil after magnetic Meta Materials are added is calculated；
(S4) in image reconstruction process, Multi-channel radio-frequency coil coupling is compensated using noise coupling matrix.
Specifically, the implementation method in step (S2): in practical clinical, it is without the case where radio-frequency emission power
Before magnetic resonance imaging perhaps after magnetic resonance imaging or to close the emission power of Multi-channel radio-frequency coil after, to adopt
Collect the noise in each channel in Multi-channel radio-frequency coil, in order to improve the accuracy of result, the sampled point of the noise is greater than 10,000
It is a.
Implementation method in step (S3): it according to the collection result in step (S2), calculates after magnetic Meta Materials are added
Multi-channel radio-frequency coil noise coupling matrix, the calculation formula of the noise coupling matrix are as follows:
Wherein, mi() indicates the noise image of i-th of channel acquisition,Indicate mj(r) conjugate transposition, 0 < i, j
≤ L, L indicates the port number of multi-channel coil here.
Implementation method in step (S4): after magnetic resonance imaging, Multi-channel radio-frequency coil receives data, passes through
Data rebuild image, and in image reconstruction, noise coupling matrix is brought into image reconstruction, compensate multi-channel radio frequency line
Circle reduces Multi-channel radio-frequency coil performance caused by deteriorating because of coupling and declines, the formula of the image reconstruction are as follows:
In formula, S is the acquisition image in each channel, and C is the sensitivity distribution of Multi-channel radio-frequency coil.
When C is equal to S, the simplified formula of image reconstruction are as follows:
It should be noted that this embodiment avoids tradition to scheme when MRI machine is imaged after magnetic Meta Materials are added
Noise coupling matrix is by the way of unit matrix when as rebuilding, and uses the calculated result of noise coupling matrix in step (S3),
The coupling condition of Multi-channel radio-frequency coil unit is obtained, thus in image reconstruction by image reconstruction formula to multi-channel radio frequency
Coil unit coupling deterioration problem is compensated by, to improve Multi-channel radio-frequency coil performance, promotes picture quality.
In order to verify the validity of the invention patent, reality as shown in Figure 2 is devised on 1.5T magnetic resonance imaging system
Experiment device.As shown in Fig. 2, the experimental provision includes the metamaterial board 2 being set on hospital bed 1, and it is held on the Meta Materials
Water mould 3 on plate 2；Volume coil 4 cover on the water mould 3 and a spine coil 5 by conducting wire (not shown) with
The magnetic resonance imaging system (not shown) connection.
The above-mentioned specific assembling mode of experimental provision are as follows: first metamaterial board 2 is placed on hospital bed 1, then by a height of 150 millimeters
Diameter is that 115 millimeters of cylindrical water mould 3 is placed upside down in above metamaterial board 2, and the body coil 4 of four-way is placed on cylinder later
The upper surface of water mould 3.The body coil 3 of four-way and the spine coil 5 in eight channels are directly connected to magnetic resonance imaging system by plug
On system.Finally, acquiring the signal of the body coil 4 of four-way and the spine coil 5 in eight channels on magnetic resonance imaging system and making an uproar
Sound.
In addition, the magnetic metamaterial board 2 that experimental provision is placed is split ring resonator.It should be noted that split ring resonator
It is set in perpendicular variation magnetic field, generates induction field, split ring resonator at this time is equivalent to inductance, and be open resonance
The both ends of ring are provided with capacitor, and charge can gather at both ends, and split ring resonator is made to form resonance circuit, and are produced from split ring resonator both ends
Raw electric dipole moment offsets each other, so that ground improves magnetic conductivity.
The present embodiment is scanned on the MRI machine of 1.5T type in clinical trial, on the MRI machine of 1.5T type
It is scanned, obtained noise coupling matrix is as shown in Figure 3.The image and the only super material of addition magnetic vibration obtained using this technology method
The image being imaged after material is compared, as shown in Figure 4.In conjunction with table 1 as can be seen that signal-to-noise ratio has promotion in water mould after compensation.Cause
This, the noise for obtaining image using this technology method is relatively high, improves image resolution ratio, promotes picture quality.
1 area-of-interest signal-to-noise ratio average value of table compares.
| Area-of-interest | Average signal-to-noise ratio is not compensated | Average signal-to-noise ratio after compensation | Signal-to-noise ratio is promoted |
| 1 | 0.52 | 0.72 | 38.4% |
| 2 | 0.38 | 0.57 | 50% |
| 3 | 0.73 | 0.84 | 15% |
Remarks: the area-of-interest refers to that medical staff wishes the patient part of detection.
In conclusion a kind of method for improving Multi-channel radio-frequency coil performance provided by the invention, by acquiring multichannel
Simultaneously its noise coupling matrix is calculated in each channel noise of radio-frequency coil, and is mended in image reconstruction using noise coupling matrix
The coupling for repaying Multi-channel radio-frequency coil deteriorates, and promotes multichannel to realize when magnetic Meta Materials are added in Multi-channel radio-frequency coil
The purpose of radio-frequency coil performance improves the signal-to-noise ratio and image resolution ratio of image, promotes picture quality.
The above embodiment of the present invention be only to clearly illustrate example of the present invention, and not be to the present invention
Embodiment restriction.For those of ordinary skill in the art, it can also make on the basis of the above description
Other various forms of variations or variation.There is no necessity and possibility to exhaust all the enbodiments.It is all of the invention
Made any modifications, equivalent replacements, and improvements etc., should be included in the protection of the claims in the present invention within spirit and principle
Within the scope of.
Claims (6)
1. a kind of method for improving Multi-channel radio-frequency coil performance, which comprises the following steps:
(1) before magnetic resonance imaging, magnetic Meta Materials are added in Multi-channel radio-frequency coil；
(2) it in the case where no radio-frequency emission power, is acquired on magnetic resonance imaging system in the Multi-channel radio-frequency coil
The noise image in each channel；
(3) the noise coupling matrix of the Multi-channel radio-frequency coil after the magnetic Meta Materials are added is calculated；
(4) in image reconstruction process, the Multi-channel radio-frequency coil coupling matrix is carried out using the noise coupling matrix
Compensation.
2. the method according to claim 1 for improving Multi-channel radio-frequency coil performance, which is characterized in that institute in step (2)
The sampled point for stating noise image is greater than 10,000.
3. the method according to claim 1 for improving Multi-channel radio-frequency coil performance, which is characterized in that institute in step (3)
State the calculation formula of noise coupling matrix Ψ are as follows:Wherein, mi() indicates i-th of channel acquisition
Noise image,Indicate the conjugate transposition of mj (r), 0 < i, j≤L, L indicates the port number of multi-channel coil here.
4. the method according to claim 1 for improving Multi-channel radio-frequency coil performance, which is characterized in that institute in step (4)
State the formula of image reconstruction are as follows:Wherein I indicates final reconstruction image at the r of position, Ψ-1Indicate noise coupling
Inverse matrix is closed, S is the acquisition image in each channel, and C is the sensitivity distribution of Multi-channel radio-frequency coil, utilizes this reconstruction formula
The coupling of Multi-channel radio-frequency coil interchannel can be compensated.
5. the method according to claim 4 for improving Multi-channel radio-frequency coil performance, which is characterized in that when C is equal to S,
The simplified formula of image reconstruction is
6. according to claim 1 to the method for any raising Multi-channel radio-frequency coil performance in 5, which is characterized in that institute
Stating magnetic Meta Materials is split ring resonator.
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| CN106125029A (en) * | 2016-06-21 | 2016-11-16 | 中国科学院深圳先进技术研究院 | Multi-channel magnetic resonance radio-frequency coil performance estimating method and device thereof |
| TWI667487B (en) * | 2016-09-29 | 2019-08-01 | 美商超精細研究股份有限公司 | Radio frequency coil tuning methods and apparatus |
| CN107356892B (en) * | 2017-07-05 | 2019-12-03 | 上海联影医疗科技有限公司 | A kind of magnetic resonance radio frequency coil adjusting method, magnetic resonance scanning system and medium |
| CN110638453B (en) * | 2019-09-19 | 2021-02-05 | 清华大学 | Tunable cylindrical super-structure surface device for nuclear magnetic resonance imaging and preparation method thereof |
| CN113017598B (en) * | 2021-03-11 | 2023-11-21 | 中国科学院深圳先进技术研究院 | Radio frequency energy deposition prediction and monitoring method, device, equipment and medium |
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