CN103105595A - Liquid nitrogen refrigeration magnetic resonance imaging system - Google Patents
Liquid nitrogen refrigeration magnetic resonance imaging system Download PDFInfo
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- CN103105595A CN103105595A CN2013100314682A CN201310031468A CN103105595A CN 103105595 A CN103105595 A CN 103105595A CN 2013100314682 A CN2013100314682 A CN 2013100314682A CN 201310031468 A CN201310031468 A CN 201310031468A CN 103105595 A CN103105595 A CN 103105595A
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Abstract
The invention discloses a liquid nitrogen refrigeration magnetic resonance imaging system. The system comprises a high-temperature superconductor main magnet capable of generating even magnetic fields in an imaging area, at least one low-temperature gradient coils capable of generating magnetic filed gradients in the imaging area, and at least one low-temperature radio frequency coil capable of receiving and transmitting radio frequency signals in the imaging area. The system comprises at least one of the following materials: non-superconducting materials and superconducting materials, wherein the non-superconducting materials and the superconducting materials have higher electrical conductivity than copper when cooled to the temperature of 77K. The main magnet, the gradient coils and the radio frequency coils of a preset system adopt low-temperature conducting materials, and the low-temperature conducting materials comprise high-temperature conducting materials, the high-temperature conducting materials are used for manufacturing coils of the main magnet, and therefore high current density can be produced in the coils, and power consumption can be saved; the high-temperature conducting main magnet is small and light and capable of operating under the temperature of 77K, and therefore refrigeration efficiency is improved greatly; and the gradients and the radio frequency coils are made of low-temperature conducting materials, resistance of the coils can be reduced, and coil efficiency can be improved.
Description
Technical field
The present invention relates to a kind of magnetic resonance imaging system of liquid nitrogen refrigerating, refer more particularly to a kind of magnetic resonance imaging system that adopts superconductive device.
Background technology
At present, mr imaging technique has been widely used in the world each large-scale medical institutions and has obtained huge and unique benefit in medical practice.MRI has been developed to the structure of a maturation and has dissected the image-forming diagnose instrument, also be developed for functional activation imaging and other biological physics and biochemical characteristics and process, as blood flow, metabolism molecule/metabolism, diffusion, the some of them mr imaging technique is included as the known MRI functional imaging of people, magnetic resonance spectrum imaging (MRSI), Diffusion-Weighted MR Imaging (DWI) and diffusion tensor imaging (DTI).These mr imaging techniques not only have at identification and assessment pathology, the diagnostic value of judgement aspect tested tissue health situation, also be widely used in clinical and research in.
During typical magnetic resonance detected, patient's health (or sample) was placed on the interior stilt of magnetic resonance scanner, places oneself in the midst of imaging region.Scanner provides constant uniform main field by main magnet.Arrange the precession atom in human body such as hydrogen (proton) in magnetic field.Gradient coil in magnet makes the magnetic field in certain limit produce change, therefore provides the resonant frequency coding at imaging region.
Radio-frequency coil generates the ringing signal in patient body based on the specific sequence of pulses selectivity under computer control, signal can be mapped to part corresponding to patient after being caught by radio-frequency coil and processing by computing machine, thereby the image of imaging region is provided.Under general MRI configuration, static main magnetic field is produced by helical type master magnet, and patient table is placed in the cylindrical space scope (i.e. the hole of main magnet) that solenoid coil surrounds into.Main field coil adopts low temperature superconducting material usually, adopts the cooling resistance that reduces of liquid helium, keeps the electric power of main field with heat and the saving of minimizing equipment generation to greatest extent.Most of cryogenic magnet adopts niobium titanium (NbTi) and/or niobium three tin superconducting alloy (Nb
3Sn), in cooled cryostat, temperature is fixed on 4.2K.Those skilled in the art are familiar with, magnetic field gradient coils can provide along the upper linear magnetic field gradient of three cartesian coordinate axes (one of them coordinate axis is the direction of main field) direction on the space, therefore size diverse location in imaging region in magnetic field is different, different magnetic resonance signal features (as signal frequency and phase place) are encoded according to its diverse location in imaging area, thereby space orientation is provided.Under common situation, by the electric current generation gradient fields of saddle coil or solenoid coil, gradient coil is fixed on the less face of cylinder.These cylinders with comprise the concentric than big column of main field coil.Different from main field, the coil that is used for the generation gradient fields adopts the normal temperature copper coil usually.Gradient intensity and vertical linearity have the vital role of essence for the accuracy of synthetic image and the chemical information of resolution and tissue (as in MRSI).
Since the invention magnetic resonance imaging, just people are devoted to improve its image quality and ability, as high spatial resolution, higher spectral resolution (in MRSI), more high-contrast and picking rate are faster provided more.For example, imaging faster (collection) speed can reduce the image fog that temporal evolution causes in image acquisition process due to imaging region (pseudo-shadow), as the patient move, dissection or functionally naturally move (as heartbeat, breathing, blood flow), and biochemical variation the (variation that causes as metabolism in MRSI) naturally.Equally, due in the magnetic resonance spectrum imaging process, the pulse train of image data is the space encoder information spectral information of also encoding both, therefore reduce to greatest extent that to gather enough wave spectrums and spatial information required time also most important for desirable spectral resolution and space orientation is provided, could improve like this Clinical practicability and the effectiveness of magnetic resonance spectrum imaging.A plurality of factors can affect the magnetic resonance imaging mass formation aspect contrast, resolution and picking rate.One of them important parameter that affects image quality and picking rate is signal to noise ratio (snr).Increase signal to noise ratio (S/N ratio) very important for improving the quality of image.Prime amplifier enhancing signal by magnetic resonance imaging system can increase signal to noise ratio (S/N ratio).Signal to noise ratio (S/N ratio) is directly proportional to magnetic field intensity, therefore can increase signal to noise ratio (S/N ratio) by the magnetic field intensity that increases magnet.But in clinical practice, the magnetic field intensity of magnet has the upper limit (U.S. FDA be limited to now 3T(tesla)).Other possible modes that increase signal to noise ratio (S/N ratio)s also have: reduce sampling noiset by reducing possible visual field, reduce to sample and radio-frequency coil between distance, and reduce the radio-frequency coil noise.Although by unremitting effort, magnetic resonance imaging has obtained significant progress, magnetic resonance imaging also has the needs that further improve, as higher contrast, stronger signal to noise ratio (S/N ratio), the room and time resolution of picking rate and Geng Gao faster.
In addition, affect the further key factor of using of mr imaging technique and namely buy and safeguard the expensive expense that the highfield system brings.Therefore, providing a class can spend magnetic resonance imaging system that reasonable price can make and/or safeguard will more be conducive to mr imaging technique and be more widely used.
Summary of the invention
The technical problem to be solved in the present invention is to provide a kind of magnetic resonance imaging system of liquid nitrogen refrigerating.
in order to solve the problems of the technologies described above, the invention provides a kind of magnetic resonance imaging system of liquid nitrogen refrigerating, this system comprises: one can produce at imaging region the high-temperature superconductor master magnet of uniform magnetic field, at least one can produce the low temperature gradients coil of magnetic field gradient in imaging region, at least one can receive and dispatch the low temperature radio-frequency coil of the radiofrequency signal in imaging region, this system comprises following at least a kind of material: the electric conductivity a kind of non-superconducting material higher than copper when being cooled to the 77K temperature, superconductor or low-temperature conductive material, described low-temperature conductive material comprises high temperature superconducting materia, described low temperature gradients coil and low temperature radio-frequency coil are placed at least one vacuum chamber, this vacuum chamber comprises the non magnetic nonmetal locular wall that one side is used for separating imaging region and low temperature gradients coil and low temperature radio-frequency coil at least, place described low temperature gradients coil in the first vacuum chamber that described vacuum chamber comprises, place described low temperature radio-frequency coil in the second vacuum chamber between the first vacuum chamber and surveyed area, locular wall is comprised of the non magnetic nonmetal locular wall of first between surveyed area and described low temperature gradients coil and the non magnetic nonmetal locular wall of second between surveyed area and described low temperature radio-frequency coil, described vacuum chamber comprises a high vacuum chamber between the second vacuum chamber and surveyed area, described high vacuum chamber as its first surface locular wall, leaves interval between the 3rd non magnetic nonmetal locular wall and this first surface locular wall by described second non magnetic nonmetal locular wall.
Wherein at least one radio-frequency coil adopts described low-temperature conductive material or superconductor; Wherein said high-temperature superconductor master magnet, low temperature gradients coil and low temperature radio-frequency coil all adopt the low-temperature conductive material, described low-temperature conductive material comprises high temperature superconducting materia, and described high temperature superconducting materia is the superconducting tape that bismuth-strontium-calcium-copper oxide (BSCCO) or yttrium barium copper oxide (YBCO) are made.
Described high-temperature superconductor master magnet, low temperature gradients coil and low temperature radio-frequency coil at least one or all to be placed on a common vacuum that is isolated by non magnetic nonmetal locular wall indoor, described common vacuum chamber comprises a high vacuum chamber between described common vacuum chamber and surveyed area, described high vacuum chamber has the described non magnetic nonmetal locular wall in two sides, leaves the interval between first surface and second locular wall.Wherein said high-temperature superconductor master magnet is cylindric, and described high-temperature superconductor master magnet is provided with a cylindrical cavity as described surveyed area.
Wherein said at least one low temperature radio-frequency coil comprises that a coil array or one both can send also receivable radio-frequency coil, and wherein said at least one low temperature radio-frequency coil comprises that a radio frequency sends coil and a RF receiving coil.Wherein said at least one low temperature gradients coil comprises at least three low temperature gradients field coils, is used for providing respectively three magnetic field gradients on orthogonal directions, and the interior uniform magnetic field direction of one of them direction and surveyed area is consistent.
As a further improvement on the present invention, a kind of magnetic resonance imaging system of liquid nitrogen refrigerating, this system comprises: one can produce at surveyed area the high-temperature superconductor master magnet of uniform magnetic field; At least one can produce the low temperature gradients coil of magnetic field gradient in surveyed area; At least one can receive and dispatch the low temperature radio-frequency coil of the radiofrequency signal in surveyed area, this low temperature radio-frequency coil configuration is used for cooling, and this system comprises following at least a kind of material: electric conductivity a kind of non-superconducting material and the superconductor higher than copper when being cooled to the 77K temperature; Described radio-frequency coil is made by the described non-superconducting material that electric conductivity is higher than copper when being cooled to 77K; Wherein said at least one radio-frequency coil is Two-dimensional electron material structure or carbon nano tube structure.
As a further improvement on the present invention, a kind of magnetic resonance imaging system of liquid nitrogen refrigerating, this system comprises: one can produce at surveyed area the high-temperature superconductor master magnet of uniform magnetic field; At least one can produce the low temperature gradients coil of magnetic field gradient in surveyed area; At least one can receive and dispatch the low temperature radio-frequency coil of the radiofrequency signal in surveyed area, this low temperature radio-frequency coil configuration is used for cooling, this system comprises following at least a kind of material: a kind of non-superconducting material that electric conductivity is higher than copper when being cooled to the 77K temperature, superconductor or low-temperature conductive material, and described low-temperature conductive material comprises high temperature superconducting materia; Described high-temperature superconductor master magnet is placed in the first vacuum chamber, and described low temperature radio-frequency coil and low temperature gradients coil are placed in the second vacuum chamber.
Further improve again as of the present invention, a kind of magnetic resonance imaging system of liquid nitrogen refrigerating, this system comprises: one can produce at surveyed area the high-temperature superconductor master magnet of uniform magnetic field; At least one can produce the low temperature gradients coil of magnetic field gradient in surveyed area; At least one can receive and dispatch the low temperature radio-frequency coil of the radiofrequency signal in surveyed area, this low temperature radio-frequency coil configuration is used for cooling, this system comprises following at least a kind of material: a kind of non-superconducting material that electric conductivity is higher than copper when being cooled to the 77K temperature, superconductor or low-temperature conductive material, and described low-temperature conductive material comprises high temperature superconducting materia; Described high-temperature superconductor master magnet, low temperature radio-frequency coil and low temperature gradients coil are placed on respectively in separately vacuum chamber.
Further improve as of the present invention, a kind of magnetic resonance imaging system of liquid nitrogen refrigerating, this system comprises: one can produce at surveyed area the high-temperature superconductor master magnet of uniform magnetic field; At least one can produce the low temperature gradients coil of magnetic field gradient in surveyed area; At least one can receive and dispatch the low temperature radio-frequency coil of the radiofrequency signal in surveyed area, this low temperature radio-frequency coil configuration is used for cooling, comprise following at least a kind of: a kind of non-superconducting material that electric conductivity is higher than copper when being cooled to the 77K temperature, superconductor or low-temperature conductive material, described low-temperature conductive material comprises high temperature superconducting materia; It is indoor that described low temperature radio-frequency coil and low temperature gradients coil are placed on same common vacuum; Wherein said low temperature radio-frequency coil and low temperature gradients coil are thermally coupled to same common heat sink.
Further improve as of the present invention, a kind of magnetic resonance imaging system of liquid nitrogen refrigerating, this system comprises: one can produce at surveyed area the high-temperature superconductor master magnet of uniform magnetic field; At least one can produce the low temperature gradients coil of magnetic field gradient in surveyed area; At least one can receive and dispatch the low temperature radio-frequency coil of the radiofrequency signal in surveyed area, this low temperature radio-frequency coil configuration is used for cooling, this system comprises following at least a kind of material: a kind of non-superconducting material that electric conductivity is higher than copper when being cooled to the 77K temperature, superconductor or low-temperature conductive material, and described low-temperature conductive material comprises high temperature superconducting materia; Described high-temperature superconductor master magnet is undertaken cooling by the first low-temperature cooling system, described low temperature radio-frequency coil is undertaken cooling by the second low-temperature cooling system, and described low temperature gradients coil is undertaken cooling by the 3rd low-temperature cooling system.
As a further improvement on the present invention, a kind of magnetic resonance imaging system of liquid nitrogen refrigerating, this system comprises: one can produce at surveyed area the high-temperature superconductor master magnet of uniform magnetic field; At least one can produce the low temperature gradients coil of magnetic field gradient in surveyed area; At least one can receive and dispatch the low temperature radio-frequency coil of the radiofrequency signal in surveyed area, this low temperature radio-frequency coil configuration is used for cooling, this system comprises following at least a kind of material: a kind of non-superconducting material that electric conductivity is higher than copper when being cooled to the 77K temperature, superconductor or low-temperature conductive material, and described low-temperature conductive material comprises high temperature superconducting materia; Described high-temperature superconductor master magnet is undertaken cooling by the first low-temperature cooling system, described low temperature radio-frequency coil and low temperature gradients coil are undertaken cooling by the second low-temperature cooling system.
Compared with prior art, the present invention has following advantages.
(1) current carrying density of described high temperature superconducting materia is far longer than low temperature superconducting material, and the magnet that therefore uses high temperature superconducting materia to make can greatly reduce the consumption of superconduction magnetic therapy wire rod, has greatly reduced weight and the volume of magnet.Under equal magnetic field intensity, the power consumption of high-temperature superconducting magnet will be saved greatly than cryogenic magnet, can save material and power consumption simultaneously.In addition, cryogenic magnet need to operate under the low temperature lower than 10K, and high-temperature superconductor master magnet can operate at the temperature of 77K, and the cold-producing medium that therefore consumes in first cold process is less, the structure of cooled cryostat is relatively simple, thereby can reduce the spending of this respect; This system adopts the low-temperature conductive material, and described low-temperature conductive material comprises that the gradient coil that high temperature superconducting materia is made can improve gradient intensity greatly, thereby greatly improves resolution; Radio-frequency coil utilizes the low-temperature conductive material, comprises high temperature superconducting materia, therefore can reduce the coil noise relevant to resistance, can greatly improve the signal to noise ratio (S/N ratio) of MRI imaging as adopting high temperature superconducting materia to make radio-frequency coil; Because the high-temperature superconductor radio-frequency coil has higher sensitivity, compare with radio-frequency coil with adopting the low-temperature superconducting gradient coil, can also simplify heat isolation and vacuum insulation step; Compare with gradient coil with conventional copper radio-frequency coil, the overall performance of magnetic resonance imaging system can get a promotion, the high-temperature superconductor gradient coil provides high drive current in addition, exchange also can obviously reduce heat radiation fast, the superconduction radio-frequency coil can reduce the coil noise, cause the signal to noise ratio (S/N ratio) of circuit in radio frequency receiver to increase, can accelerate like this picking rate and/or improve image resolution ratio.
(2) described main magnet, gradient coil and radio-frequency coil are the superconductor at the 77K temperature, and every kind is high-temperature superconductor or cryogenic superconductor, described gradient coil is the same superconductor, be high-temperature superconductor or cryogenic superconductor, the configuration of this kind overall height temp. superconductive makes cost, quality raising and performance good.
(3) high-temperature superconductor master magnet can adopt belt material of high temperature superconduct, as yttrium barium copper oxide (YBCO), bismuth-strontium-calcium-copper oxide (BSCCO) and other critical temperatures higher than one or more in the belt material of high temperature superconduct of 77K, the Magnetic Field Design of a correcting coil is inhomogeneous, after main field combined, the unevenness of total magnetic field namely can be offset in the magnetic field of correcting coil.
(4) vacuum chamber is placed low temperature gradients coil and low temperature radio-frequency coil.Space between each double wall is two-layer is evacuated, the outside double wall of vacuum chamber adopts non magnetic nonmetallic materials, the material that the inside double wall of vacuum chamber adopts does not produce shielding effectiveness to the radiofrequency signal that the low temperature radio-frequency coil transmits and receives, can be because gradient signal produces eddy effect to the effect of low temperature gradients coil yet.
(5) second layer inwall is set and is separated out the vacuum space for the heat isolation, be conducive to improve users'comfort aspect temperature.The vacuum space is coupled to a vacuum pump or as a closed chamber.The radial extension of vacuum space minimizes to guarantee that radio-frequency coil is as far as possible near Examination region.Inwall adopts nonmagnetic substance, can interference test gradient magnetic and radiofrequency signal in the zone.
(6) superconducting coil of the gradient coil gradient heat that generates or distribute reduces, and allows high gradient field to change fast, thereby it is faster to gather the speed of image.
Description of drawings
Figure 1A is the xsect signal schematic diagram of the superconducting magnetic resonance imaging system of liquid nitrogen refrigerating of the present invention.
Figure 1B is according to the top cross sectional representation of the main magnet system in Figure 1A of the present invention.
Fig. 2 A is according to the stravismus schematic diagram of the gradient coil of the liquid nitrogen refrigerating magnetic resonance imaging system in Figure 1A of the present invention.
Fig. 2 B is according to the floor map of the gradient coil on right cylinder X-direction in Fig. 2 A of the present invention.
Fig. 3 A-3D is of the present invention for the different cooling system configurations in magnetic resonance imaging system.
Fig. 4 A and 4B are the cross-sectional view of the coil configuration of the present invention's superconducting magnetic resonance imaging system of adopting cylindric line solenoid coil structures.
Embodiment
Embodiment one.
a kind of magnetic resonance imaging system of liquid nitrogen refrigerating, this system comprises: one can produce at imaging region the high-temperature superconductor master magnet of uniform magnetic field, described high-temperature superconductor master magnet is cylindric, described high-temperature superconductor master magnet is provided with a hole as described surveyed area, at least one can produce the low temperature gradients coil of magnetic field gradient in imaging region, at least one can receive and dispatch the low temperature radio-frequency coil of the radiofrequency signal in imaging region, this system comprises following at least a kind of material: the electric conductivity a kind of non-superconducting material higher than copper when being cooled to the 77K temperature, superconductor or low-temperature conductive material, described low-temperature conductive material comprises high temperature superconducting materia, described low temperature gradients coil and low temperature radio-frequency coil are placed at least one vacuum chamber, and this vacuum chamber comprises the non magnetic nonmetal locular wall that one side is used for separating imaging region and low temperature gradients coil and low temperature radio-frequency coil at least.
Wherein said at least one low temperature radio-frequency coil comprises that a coil array or one both can send also receivable radio-frequency coil; Wherein said at least one low temperature radio-frequency coil comprises that a radio frequency sends coil and a RF receiving coil, wherein said at least one low temperature gradients coil comprises at least three low temperature gradients field coils, be used for providing respectively three magnetic field gradients on orthogonal directions, the interior uniform magnetic field direction of one of them direction and surveyed area is consistent.
Wherein at least one low temperature radio-frequency coil adopts described superconductor, wherein said high-temperature superconductor master magnet, low temperature gradients coil and low temperature radio-frequency coil all adopt the low-temperature conductive material, described low-temperature conductive material or low-temperature conductive material of the same race, described low-temperature conductive material comprises high temperature superconducting materia, and described high temperature superconducting materia is the superconducting tape that bismuth-strontium-calcium-copper oxide (BSCCO) or yttrium barium copper oxide (YBCO) are made.
It is indoor that wherein said high-temperature superconductor master magnet, low temperature gradients coil and low temperature radio-frequency coil are placed on a common vacuum that is isolated by non magnetic nonmetal locular wall, described common vacuum chamber comprises a high vacuum chamber between described common vacuum chamber and surveyed area, described high vacuum chamber has the described non magnetic nonmetal locular wall in two sides, leaves the interval between first surface and second locular wall.
Place described low temperature gradients coil in the first vacuum chamber that described vacuum chamber comprises, place described low temperature radio-frequency coil in the second vacuum chamber between the first vacuum chamber and surveyed area, locular wall is comprised of the non magnetic nonmetal locular wall of first between surveyed area and described low temperature gradients coil and the non magnetic nonmetal locular wall of second between surveyed area and described low temperature radio-frequency coil; Described vacuum chamber also comprises a high vacuum chamber between the second vacuum chamber and surveyed area, described high vacuum chamber as its first surface locular wall, leaves interval between the 3rd non magnetic nonmetal locular wall and this first surface locular wall by described second non magnetic nonmetal locular wall.
As shown in Figure 1A, super magnetic resonance imaging system 100 comprises an imaging region 180, removable scanning bed 190, magnet/coil shell 130 and main magnet system, main magnet system comprises that (i) is with the main magnet of superconduction main coil 104, superconduction correcting coil 106 and coil rack 108, (ii) the Cryo Refrigerator cold head 110, (iii) cooled cryostat 112, (iv) thermal shield 114, and (v) main magnet vacuum chamber housing 116 is with (vi) cryogenic system 160.Can from the imaging area shift-in or shift out removable scanning bed 190.Scanning bed 190 parts that are placed in main field need to adopt the non magnetic nonmetallic materials such as plastics.
The second vacuum chamber of magnet/coil shell 130 has been contained interior section, magnet/coil shell 130 end wall portion and the inwall 150 of vacuum chamber housing 116, and the vacuum space 142 that crosses comprises low temperature gradients coil 103 and low temperature radio-frequency coil 105.The vacuum chamber that comprises space 142 is coupled to a fine pumping system in order to set up environment under low pressure (for example high vacuum situation) in manufacture process, i.e. sealing after reaching high vacuum condition.Low temperature radio-frequency coil 105 and low temperature gradients coil 103 all keep good thermo-contact with public heat radiator 110, and heat radiator is thermally coupled to cryogenic system 170.Cryogenic system 170 comprises refrigeration machine 172 and the second level 174, and an end of the second level 174 is thermally coupled to heat radiator 110, and the other end is thermally coupled to refrigeration machine 172.The material that is suitable for making heat radiator has ceramic-like such as aluminium oxide, crystal class such as sapphire and metal, and glass etc.
Figure 1B has at length described the top cross sectional representation of the main magnet system in Figure 1A.As shown in Figure 1B, vacuum chamber housing 116 comprises 132, one of a vacuum spaces vacuum system around main magnet and is connected to vacuum space 132 via one or more ports, vacuum tube and/or lead-in wire etc., in order to this space vacuum pressure is evacuated to 10
5Holder or lower, i.e. condition of high vacuum degree.Vacuum chamber housing 116 adopts aluminium, stainless steel or other metals or nonmetallic materials to make, as glass, pottery, plastics, or by these material mixing manufactures, the thermal insulation that vacuum space 132 is used between main magnet and vacuum chamber housing 116.
Superconduction main coil 104 and superconduction correcting coil 106 both can be used as cryogenic superconductor and also can be used as high-temperature superconductor.Low-temperature superconducting master magnet can adopt low-temperature superconducting electric wire such as niobium titanium (NbTi), niobium three tin (Nb
3Sn), niobium three aluminium (Nb
3Al), magnesium diboride (MgB
2) and other low-temperature superconducting wires.high-temperature superconductor master magnet can adopt belt material of high temperature superconduct, as yttrium barium copper oxide (YBCO), bismuth-strontium-calcium-copper oxide (BSCCO) and other critical temperatures are higher than one or more in the belt material of high temperature superconduct of 77K, the use of one or more sets correcting coils 106 is in order to realize higher uniformity of magnetic field, this type of correcting coil generally is designed for the number of turn of electric current and/or the carrying sub-fraction superconduction main coil of carrying sub-fraction superconduction main coil, the Magnetic Field Design of a correcting coil is inhomogeneous, after main field combines, the unevenness of total magnetic field namely can be offset in the magnetic field of correcting coil.
Superconduction main coil 104 and superconduction correcting coil 106 all are wound around puts coil supports 108 into.Coil supports 108 adopts one or more in the high material of stainless steel, aluminium, FR4 or other physical strengths.Coil supports 108 is connected to heat radiator 110 and keeps good thermo-contact, and heat radiator 110 is coupled to cryogenic system 160 again, so that heat is passed to cryogenic system 160 via heat radiator 110.The material that is suitable for making heat radiator 110 has aluminium oxide, sapphire and metal.
As shown in Figure 1A and 1B, a large amount of uniformly horizontal magnetic fields of superconducting main magnet system's employing solenoid coil in imaging region generates certain limit are such as in the 0.5T-10T scope.In alternate embodiments, according to designing and/or application request, superconducting main magnet system's employing other configurations except solenoid such as low of vertical-type magnet, two bagel vertical magnets and/or employing, are arrived 0.5T as 0.1T as open magnet.In typical case, the direction of downfield can be towards the direction of expectation, such as with direction or the vertical direction of scanning bed quadrature, and the direction of highfield is generally horizontal direction.
Superconduction radio-frequency coil 105 and superconduction gradient coil 103 share cooling system, thereby superconduction radio-frequency coil 105 and superconduction gradient coil 103 Chang Zuowei same kind superconductor more, namely be all high-temperature superconductor or be all cryogenic superconductor, if they can be cooled to the critical temperature of low-temperature superconducting, adopt wherein a kind ofly also to allow as cryogenic superconductor as the high-temperature superconductor another kind.This uses lower high-temperature superconductor radio-frequency coil and the suitable material that uses of gradient coil is the superconducting tape of being made by bismuth strontium Cu oxide (BSCCO) or similar material.In other alternative embodiments, the superconduction radio-frequency coil may be superconducting thin film, adopts yttrium barium copper oxide (YBCO), thallium barium calcium copper oxide (TBCCO), magnesium diboride (MgB
2) or boronation M(MB) etc. the high-temperature superconductor material make, wherein M is beryllium (Be), aluminium (Al), niobium (Nb), molybdenum (Mo), tantalum (Ta), titanium (Ti), hafnium (Hf), vanadium (V) or chromium (Cr).The detailed guidance of making high-temperature superconducting thin film on planar substrates is included in Ma et al, " Superconducting MR Surface Coils for Human Imaging; " Proc. Mag. Res. Medicine, 1,171 (1999), its disclosed content integral body by reference is attached to herein.other teachings about high temperature superconductor coil are included in Ma et al., " Superconducting RF Coils for Clinical MR Imaging at Low Field, " Academic Radiology, vol. 10, no., 9, September 2003, pp. 978-987, with Miller et al., " Performance of a High Temperature Superconducting Probe for In Vivo Microscopy at 2.0 T, " Magnetic Resonance in Medicine, in 41:72-79 (1999), its disclosed content integral body by reference is attached to herein.
The structure of magnetic resonance imaging system and running may be used multiple different high-temperature superconductor and low temperature superconducting material.For example, gradient coil 304 may adopt commercial superconducting tape Bi-223 cheaply.In some cases, the Bi-223 superconducting tape may be with fine silver (Ag) sheath to improve its physical strength.The Bi-223 superconducting tape immerses realizes superconducting characteristic when freezing in liquid nitrogen, this moment, its resistance was close to zero substantially.Both can be configured to the superconduction radio-frequency coil 306 that transceiver also can be configured to independent transmission machine or receiver, also may adopt high temperature superconducting materia, as YBCO, BSCCO etc. or adopt superconductor, nano material such as carbon nano-tube and have Two-dimensional electron (2DEG) material/structure of high conductivity characteristics.Perhaps, high-temperature superconductor radio-frequency coil 306 may be a row film coil, and the basal diameter of each film is, for example, and approximately 1 centimetre to 30 centimetres.The superconducting main magnet coil may adopt high-temperature superconductor or low temperature superconducting material.For example, may use magnesium diboride (MgB
2) make main magnet coil 302.From cooling angle, superconducting coil perhaps can operate in different temperature ranges.For example, superconducting main magnet 302 may be cooled between 20-40K, and superconduction gradient coil 304 may be cooled between 40K-60K, and superconduction radio-frequency coil 306 holding temperatures can be higher, between 40K-60K or higher than 77K.Perhaps, superconducting main magnet 302 is cooled between 20K-40K, and superconduction gradient coil 304 and superconduction radio-frequency coil 306 all are cooled to 77K.The various temperature combination is arranged for the keeping coil running.For example, under some configuration mode, all superconducting coils may all maintain 77K.
Main magnet, gradient coil and radio-frequency coil are superconductor, and every kind can be high-temperature superconductor or cryogenic superconductor.Suppose that all gradient coils are same superconductor (as high-temperature superconductor), have eight kinds may make up.According to preferential embodiments more of the present invention, main magnet, gradient coil and radio-frequency coil are high-temperature superconductor.This kind overall height temp. superconductive configuration can bring many advantages at aspects such as the cost of magnetic resonance imaging system, quality and performances, for example, low-temperature superconducting master magnet is usually very heavy, and based on the more small-sized light and handy and power saving comparatively speaking of the high-temperature superconductor master magnet of numerous embodiments of the present invention.In addition, cryogenic magnet need to be in the lower running of low temperature (as lower than 10K or 10-20K), and high-temperature superconductor master magnet can be in the lower running of relatively high temperature (as 77K), therefore less at the first cold-producing medium that consumes when cold, the structure of cooled cryostat is relatively simple, thereby can reduce the spending of this respect.Adopt the superconduction gradient coil to compare with gradient coil with conventional copper radio-frequency coil with the superconduction radio-frequency coil, the overall performance of magnetic resonance imaging system can get a promotion, wherein partly cause comprises that the high-temperature superconductor radio-frequency coil has higher sensitivity (the coil noise is low, and therefore signal to noise ratio (S/N ratio) is high), and the high-temperature superconductor gradient coil provides high drive current, exchange also can obviously reduce heat radiation and increase resolution fast.
Radio-frequency coil 105 is independent respectively is radio-frequency sending coil and RF receiving coil, or may namely have the function that transmits and receives by a radio-frequency coil, it is the radio-frequency receiving-transmitting coil, in addition, adopt in the embodiment of independent radio-frequency sending coil and RF receiving coil at some, only having wherein a kind ofly, is superconducting coil as receiving coil, and other a kind of coils are conventional copper coil.In some embodiments, superconduction radio-frequency coil 105 may be coil array, as the high temperature superconductive wire coil array.
As shown in Fig. 2 A, form or otherwise provide three independently to be used for creating the gradient coil that magnetic field changes along three orthogonal directionss, be placed on three corresponding coaxial cylindrical supporting construction surfaces, that is, the x-gradient supports 258, the y-gradient support 262 and the z-gradient support 264.In a conventional manner, x-and y-represent two orthogonal directionss perpendicular to main field, and z-represents the direction of main field.Therefore, x-gradient support 258, the support 262 of y-gradient and z-gradient support 264 and place respectively corresponding gradient coils for the magnetic field gradient that provides on these three directions.Gradient supports 258,262 and 264 by G10 or other nonferromagnetics, non-conductive, for example, nonmetal, insulating material manufacturing, in this embodiment, the z-gradient coil is solenoid coil, and x-and y-gradient coil are saddle coil and cover separately about along the circumferential direction half of its cylindrical support.Y-gradient support 262 is connected to the support 258 of x-gradient and z-gradient support 264, z-gradient support 264 is connected to heat radiator 110 and the thermo-contact good with its maintenance.In other alternative embodiments, can increase a heating radiator and be connected to heat radiator 110 or support 258 replacement z-gradient support and connection to heat radiator 110 with the x-gradient.If increase a heating radiator outside heat radiator 110, this heating radiator and x-gradient support 258 and join and may by refrigeration machine 172, namely also be used for the same refrigeration machine of cold sink 110 or independent cryocooled.Replace the z-gradients to support 264 being connected to heat radiator 110 when providing gradient coil cooling when support 258 with the x gradient, heat radiator 110 may support pyrolysis coupling on 264 from the z-gradient, but still with radio-frequency coil 105 thermal couplings so that cooling to radio-frequency coil 105 to be provided.
As shown in Fig. 2 B, comprise that the x-gradient supports the x-gradient coil 268 of placing on 258.The x-gradient supports that 258 surface normally caves in, and for example cutter falls into or carving falls into, and gradient coil 268 electric wires are placed and are fixed in groove, also can not move when electric current electric wire when being arranged in the gradient coil electric wire in magnetic field like this.The design structure of the x-gradient coil 268 of placing in the y-gradient coil of placing in y-gradient support 262 and x-gradient support 258 is basic identical, but it is smaller that the diameter that the y-gradient supports supports than x-gradient, so the y-gradient coil is slightly variant with the x-gradient coil dimensionally.The center 260 of x-gradient coil 268 is towards the x direction of principal axis.
As shown in Fig. 2 A and 2B, the y-gradient coil becomes 90 ° with the x-gradient coil.The z-gradient that is placed on helical round z-gradient coil supports on 264 surfaces and/or in the surface, but because being wound in the z-gradient along the cylinder axis spiral fashion, supports on 264 the z-gradient coil, one half-coil is consistent with the direction of main magnet coil, and this part gradient coil can strengthen the magnetic field in scope; And the opposite direction of second half coil and main magnet coil, this coil sections reduces the magnetic field in scope.
Although described embodiment coil all is configured to provide the magnetic field of horizontal direction, other magnetic resonance imaging systems may be taked other structural designs in order to generate (FOV) different magnetic field intensity in the visual field, as the vertical magnetic field of 0.5T, 1.0T.This type of magnetic resonance imaging system includes but not limited to: with the asymmetric head scanning magnetic resonance imaging system of 6 or 8 radio frequency coil arrays; Check the orthopaedics magnetic resonance imaging system (0.2-0.5T) of hand and shank; Or the vertical magnetic field open type magnetic resonance imaging (MRI) system of scanning chest (radio-frequency coil may be arranged on scanning bed interior).The design concept of vertical magnetic field open type magnetic resonance imaging (MRI) system also can be expanded for checking animal.Although in embodiment described herein, all for the hydrogen atom of surveying tissue moisture, this system also is applicable to survey other atomic nucleus that magnetic resonance signal is arranged to magnetic resonance imaging system.
As shown in Fig. 3 B, main magnet coil 220 is controlled cooling to realize high-temperature superconductor or low-temperature superconducting characteristic by low-temperature cooling system 222.And gradient coil 226 and radio-frequency coil 228 are controlled cooling to realize high-temperature superconductor or low-temperature superconducting characteristic by public low-temperature cooling system 230.In this kind embodiment, all coils carries out cooling at its cooling chamber separately.
As shown in Fig. 3 D, main magnet and gradient coil 244 are controlled cooling realizing high-temperature superconductor or low-temperature superconducting characteristic by low-temperature cooling system independently 246, and each 244 coils all carry out cooling at same cooling chamber.And that radio-frequency coil 248 is controlled by low-temperature cooling system independently 250 is cooling realizing high-temperature superconductor or low-temperature superconducting characteristic, and radio-frequency coil 248 carries out cooling in another cooling chamber that is different from main magnet and gradient coil place.
Embodiment two.
A kind of magnetic resonance imaging system of liquid nitrogen refrigerating, this system comprises: one can produce at surveyed area the high-temperature superconductor master magnet of uniform magnetic field; At least one can produce the low temperature gradients coil of magnetic field gradient in surveyed area; At least one can receive and dispatch the low temperature radio-frequency coil of the radiofrequency signal in surveyed area, this low temperature radio-frequency coil configuration is used for cooling, this system comprises following at least a kind of material: a kind of non-superconducting material that electric conductivity is higher than copper when being cooled to the 77K temperature, superconductor or low-temperature conductive material, and described low-temperature conductive material comprises high temperature superconducting materia; Described low temperature radio-frequency coil during by the described 77K of being cooled to the electric conductivity non-superconducting material higher than copper be made, wherein said at least one radio-frequency coil is Two-dimensional electron material structure or carbon nano tube structure.
One or more radio-frequency coils, to be a plurality of radio-frequency coils be the non-superconducting coil if transmitting coil separates with receiving coil.The material that this type of coil adopts is one or more electric conductivity materials higher than the copper under equal temperature when being cooled to fixed temperature.This type of non-superconducting coil adopts semi-conductive Two-dimensional electron (2DEG) material structure, as gallium arsenide (GaAs) and/or indium phosphide (InP) base, carbon nano-tube and other metals.Distinguish low temperature and refrigeration, about 73.3 ° C(100 °F) or followingly can regard low temperature as, other structures or system are identical with embodiment one.
Embodiment three.
A kind of magnetic resonance imaging system of liquid nitrogen refrigerating, this system comprises: one can produce at surveyed area the high-temperature superconductor master magnet of uniform magnetic field; At least one can produce the low temperature gradients coil of magnetic field gradient in surveyed area; At least one can receive and dispatch the low temperature radio-frequency coil of the radiofrequency signal in surveyed area, this low temperature radio-frequency coil configuration is used for cooling, this system comprises following at least a kind of material: a kind of non-superconducting material that electric conductivity is higher than copper when being cooled to the 77K temperature, superconductor or low-temperature conductive material, and described low-temperature conductive material comprises high temperature superconducting materia; Described high-temperature superconductor master magnet is placed in the first vacuum chamber, and described low temperature radio-frequency coil and low temperature gradients coil are placed in the second vacuum chamber.
As shown in Fig. 4 A, the first cross-sectional view of the coil configuration 300 of the magnetic resonance imaging system 100 in similar Figure 1A, coil configuration 300 comprises the first vacuum chamber 316, the second vacuum chamber 314, one or more main magnet coils 302, one or more gradient coils 304, one or more radio-frequency coils 306, and locular wall 308,310 and 312.In further illustrating hereinafter, coil configuration 300 each locular walls 308,310 and 312 form the sealing double-wall structure, in some embodiments based on or the U.S. Patent application the 12/212nd submitted on September 17th, 1, No. 122 and the 12/212nd, sealing double-wall structure in No. 147 (with the vacuum heat-insulation shell), its disclosed content integral body by reference is attached to herein.
The the first interior placement superconducting magnet of vacuum chamber 316 and coil 302 thereof.Vacuum chamber 316 by double wall 308 and 310 seal isolation out.The space of each double wall 308 and 310 between two-layer is evacuated, and fills the thermal isolation material, and suitably sealing to guarantee high vacuum.The confined space relevant to the first vacuum chamber 316 may be found time by suitable vacuum pump.The outside double wall 308 of the first vacuum chamber 316 can adopt conventional vacuum chamber material structure, but is not limited to aluminium or stainless steel.And the inside double wall 310 of the first vacuum chamber 316 adopts non magnetic nonmetallic materials, but only limits to as glass fibre, non-conductive pottery, G10, FR4 or plastics.
After forming enough vacuum in the first vacuum chamber 316, reduce the temperature of main magnet coil 302 with a low-temperature cooling system.The temperature that needs to reduce is determined by coil method.Compare with the cooling copper coil of routine, coil 302 utilizes low temperature superconducting material or high temperature superconducting materia, therefore can reduce resistance.The superconducting coil of main magnet coil 302 is used to generate required magnetic field of the goal by specific currents, and as 1 tesla, the heat that therefore generates or distribute can reduce.The power that produces and keep required magnetic field for main magnet also can reduce.In addition, magnetic resonance imaging may be further used for higher magnetic field intensity, as greater than 7 teslas.In the case, use the superconducting main magnet coil can produce in coil higher current density, thereby strengthen the magnetic field ability.Low-temperature cooling system for example, can move between 20 to 40 Kelvins.According to some embodiments, a superconducting main magnet coil may be for cylindrical, and long 0.5 to 3 meter, 1 to 3 meter of external diameter, 0.1 to 2.5 meter of internal diameter.
The second vacuum chamber 314 is placed low temperature gradients coil 304 and low temperature radio-frequency coil 306.Vacuum chamber 314 by double wall 310 and 312 seal isolation out, the space of each double wall 310 and 312 between two-layer is evacuated, and fills the thermal isolation material, and suitably sealing to guarantee high vacuum.The confined space relevant to the second vacuum chamber 314 may be found time by suitable vacuum pump.The outside double wall 310 of the second vacuum chamber 314 adopts non magnetic nonmetallic materials, but only limits to glass fibre, non-conductive pottery, G10, FR4 or plastics.And the radiofrequency signal that the material that the inside double wall 312 of the second vacuum chamber 314 adopts transmits and receives radio-frequency coil 306 does not produce shielding effectiveness, can be because gradient signal produces eddy effect to the effect of gradient coil 304 yet.
After forming enough vacuum in the second vacuum chamber 314, reduce a kind of or whole temperature in gradient coil 304 and radio-frequency coil 306 with another low-temperature cooling system.The temperature that needs to reduce is determined by coil method.Compare with the cooling copper coil of routine or other similar non-superconducting materials, coil 304 and/or 306 utilizes low temperature superconducting material or high temperature superconducting materia, therefore can reduce the resistance of coil.The superconducting coil generation of gradient coil 304 or the gradient heat that distributes reduce, and allow high gradient field to change fast, thereby the speed of collection image is faster, are used for the also corresponding minimizing of cooling requirement of gradient magnetic generation and distribute heat.Be used for the low-temperature cooling system of cooling gradient coil 304, for example, can move between 40 to 60 Kelvins.According to some embodiments, a superconduction gradient coil may be cylindric spirality and saddle type, long 0.2 to 2 meter, and 0.1 to 2.5 meter of external diameter, 0.02 to 2.3 meter of internal diameter.A high-temperature superconductor radio-frequency coil is cylindric spirality and saddle type, long 0.01 to 0.5 meter, and 0.02 to 1 meter of external diameter, 0.01 to 0,8 meter of internal diameter.Superconduction radio-frequency coil 306 can reduce the coil noise, causes the signal to noise ratio (S/N ratio) of circuit in radio frequency receiver to increase, and can accelerate like this picking rate and/or improve image resolution ratio.Be used for the low-temperature cooling system of cooling gradient coil 304 and radio-frequency coil, for example, can move between 40 to 60 Kelvins.Fig. 4 B has described coil configuration 300 the second cross-sectional view along the longitudinal direction.
Embodiment four.
A kind of magnetic resonance imaging system of liquid nitrogen refrigerating, this system comprises: one can produce at surveyed area the high-temperature superconductor master magnet of uniform magnetic field; At least one can produce the low temperature gradients coil of magnetic field gradient in surveyed area; At least one can receive and dispatch the low temperature radio-frequency coil of the radiofrequency signal in surveyed area, this low temperature radio-frequency coil configuration is used for cooling, this system comprises following at least a kind of material: a kind of non-superconducting material that electric conductivity is higher than copper when being cooled to the 77K temperature, superconductor or low-temperature conductive material, and described low-temperature conductive material comprises high temperature superconducting materia; Described high-temperature superconductor master magnet, low temperature radio-frequency coil and low temperature gradients coil are placed on respectively in separately vacuum chamber, and other structures or system are identical with embodiment one.
Embodiment five.
A kind of magnetic resonance imaging system of liquid nitrogen refrigerating, this system comprises: one can produce at surveyed area the high-temperature superconductor master magnet of uniform magnetic field; At least one can produce the low temperature gradients coil of magnetic field gradient in surveyed area; At least one can receive and dispatch the low temperature radio-frequency coil of the radiofrequency signal in surveyed area, this low temperature radio-frequency coil configuration is used for cooling, this system comprises following at least a kind of material: a kind of non-superconducting material that electric conductivity is higher than copper when being cooled to the 77K temperature, superconductor or low-temperature conductive material, and described low-temperature conductive material comprises high temperature superconducting materia; It is indoor that described low temperature radio-frequency coil and low temperature gradients coil are placed on same common vacuum, and wherein said low temperature radio-frequency coil and low temperature gradients coil are thermally coupled to same common heat sink.
In this embodiment, refrigerant system receiver 112 is unwanted, and refrigerant carries out via heat radiator 110 system cools in the situation that do not use on every side.The temperature of the refrigeration machine first order and the second level for example, can be respectively 40K and 20K, 77K and 40K or other combinations by the decisions such as cryogenic system type, thermal source or load of the parameter in when design such as superconducting magnet material therefor, employing.Therefore, the temperature of thermoshield 114 is between the low temperature of the 77K of vacuum wall and magnet coil, is used for avoiding superconducting main magnet to be subject to heat from vacuum wall.In some embodiments, thermoshield may more than one deck or may do not adopted thermoshield 114 modes.
Embodiment six.
A kind of magnetic resonance imaging system of liquid nitrogen refrigerating, this system comprises: one can produce at surveyed area the high-temperature superconductor master magnet of uniform magnetic field; At least one can produce the low temperature gradients coil of magnetic field gradient in surveyed area; At least one can receive and dispatch the low temperature radio-frequency coil of the radiofrequency signal in surveyed area, this low temperature radio-frequency coil configuration is used for cooling, this system comprises following at least a kind of material: a kind of non-superconducting material that electric conductivity is higher than copper when being cooled to the 77K temperature, superconductor or low-temperature conductive material, and described low-temperature conductive material comprises high temperature superconducting materia; Described low-temperature superconducting master magnet is undertaken cooling by the first low-temperature cooling system, described low temperature radio-frequency coil is undertaken cooling by the second low-temperature cooling system, and described low temperature gradients coil is undertaken cooling by the 3rd low-temperature cooling system.
As shown in Figure 3A, each superconducting coil 202 is all undertaken cooling by separately low-temperature cooling system 204 in cooling chamber separately.Main magnet coil 206 is controlled cooling to realize high-temperature superconductor or low-temperature superconducting characteristic by low-temperature cooling system 208.In like manner, gradient coil 210 is controlled cooling to realize high-temperature superconductor or low-temperature superconducting characteristic by low-temperature cooling system 212, and radio-frequency coil 214 is controlled cooling to realize high-temperature superconductor or low-temperature superconducting characteristic by low-temperature cooling system 216.
Embodiment seven.
A kind of magnetic resonance imaging system of liquid nitrogen refrigerating, this system comprises: one can produce at surveyed area the high-temperature superconductor master magnet of uniform magnetic field; At least one can produce the low temperature gradients coil of magnetic field gradient in surveyed area; At least one can receive and dispatch the low temperature radio-frequency coil of the radiofrequency signal in surveyed area, this low temperature radio-frequency coil configuration is used for cooling, this system comprises following at least a kind of material: a kind of non-superconducting material that electric conductivity is higher than copper when being cooled to the 77K temperature, superconductor or low-temperature conductive material, and described low-temperature conductive material comprises high temperature superconducting materia; Described high-temperature superconductor master magnet is undertaken cooling by the first low-temperature cooling system, described low temperature radio-frequency coil and low temperature gradients coil are undertaken cooling by the second low-temperature cooling system.
As shown in Figure 3 C, gradient coil and radio-frequency coil 238 all carry out cooling at same cooling chamber, main magnet coil 234 is controlled cooling to realize that high-temperature superconductor or low-temperature superconducting characteristic and each coil 234 carry out cooling at separately cooling chamber by low-temperature cooling system 236.And gradient coil and radio-frequency coil 238 are controlled cooling to realize high-temperature superconductor or low-temperature superconducting characteristic by public low-temperature cooling system 240.
But these embodiments are only used for the explanation principle of the invention, are not for the present invention only has embodiment, and above-described embodiment should not be considered as limiting the scope of the invention, and each term used herein and wording are used for explanation but not are used for restriction.The term that uses in the characteristic of describing herein or its partial content and wording do not get rid of other etc. justice describe.In addition, may not provide in practice process of the present invention herein describe or from the disclosure amplification and/or some embodiments wherein one or more of the advantage that realizes, the present invention is not limited to embodiment disclosed herein.
Claims (20)
1. the magnetic resonance imaging system of a liquid nitrogen refrigerating, it is characterized in that: this system comprises: one can produce at imaging region the high-temperature superconductor master magnet of uniform magnetic field, at least one can produce the low temperature gradients coil of magnetic field gradient in imaging region, at least one can receive and dispatch the low temperature radio-frequency coil of the radiofrequency signal in imaging region, this system comprises following at least a kind of material: the electric conductivity a kind of non-superconducting material higher than copper when being cooled to the 77K temperature, superconductor or low-temperature conductive material, described low-temperature conductive material comprises high temperature superconducting materia, described low temperature gradients coil and low temperature radio-frequency coil are placed at least one vacuum chamber, this vacuum chamber comprises the non magnetic nonmetal locular wall that one side is used for separating imaging region and low temperature gradients coil and low temperature radio-frequency coil at least.
2. the magnetic resonance imaging system of liquid nitrogen refrigerating according to claim 1 is characterized in that: wherein at least one radio-frequency coil adopts described low-temperature conductive material or superconductor.
3. the magnetic resonance imaging system of liquid nitrogen refrigerating according to claim 1, it is characterized in that: wherein said high-temperature superconductor master magnet, low temperature gradients coil and low-temperature superconducting radio-frequency coil all adopt low-temperature conductive material, i.e. high temperature superconducting materia.
4. the magnetic resonance imaging system of liquid nitrogen refrigerating according to claim 1, it is characterized in that: described high temperature superconducting materia is the superconducting tape that bismuth-strontium-calcium-copper oxide (BSCCO) or yttrium barium copper oxide (YBCO) are made.
5. the magnetic resonance imaging system of liquid nitrogen refrigerating according to claim 1 is characterized in that: wherein said high-temperature superconductor master magnet, low temperature gradients coil and low temperature radio-frequency coil at least one or all to be placed on a common vacuum that is isolated by non magnetic nonmetal locular wall indoor.
6. the magnetic resonance imaging system of liquid nitrogen refrigerating according to claim 5, it is characterized in that: described common vacuum chamber comprises a high vacuum chamber between described common vacuum chamber and surveyed area, described high vacuum chamber has the described non magnetic nonmetal locular wall in two sides, leaves the interval between first surface and second locular wall.
7. the magnetic resonance imaging system of liquid nitrogen refrigerating according to claim 1, it is characterized in that: place described low temperature gradients coil in the first vacuum chamber that described vacuum chamber comprises, place described low temperature radio-frequency coil in the second vacuum chamber between the first vacuum chamber and surveyed area, locular wall is comprised of the non magnetic nonmetal locular wall of first between surveyed area and described low temperature gradients coil and the non magnetic nonmetal locular wall of second between surveyed area and described low temperature radio-frequency coil.
8. the magnetic resonance imaging system of liquid nitrogen refrigerating according to claim 7, it is characterized in that: described vacuum chamber comprises a high vacuum chamber between the second vacuum chamber and surveyed area, described high vacuum chamber as its first surface locular wall, leaves interval between the 3rd non magnetic nonmetal locular wall and this first surface locular wall by described second non magnetic nonmetal locular wall.
9. the magnetic resonance imaging system of liquid nitrogen refrigerating according to claim 1, it is characterized in that: wherein said high-temperature superconductor master magnet is cylindric, described high-temperature superconductor master magnet is provided with a cylindrical cavity as described surveyed area.
10. the magnetic resonance imaging system of liquid nitrogen refrigerating according to claim 1 is characterized in that: wherein said at least one low temperature radio-frequency coil comprises that a coil array or one both can send also receivable radio-frequency coil.
11. the magnetic resonance imaging system of liquid nitrogen refrigerating according to claim 1 is characterized in that: wherein said at least one low temperature radio-frequency coil comprises that a radio frequency sends coil and a RF receiving coil.
12. the magnetic resonance imaging system of liquid nitrogen refrigerating according to claim 1, it is characterized in that: wherein said at least one low temperature gradients coil comprises at least three low temperature gradients field coils, be used for providing respectively three magnetic field gradients on orthogonal directions, the interior uniform magnetic field direction of one of them direction and surveyed area is consistent.
13. the magnetic resonance imaging system of a liquid nitrogen refrigerating is characterized in that: this system comprises: one can produce at surveyed area the high-temperature superconductor master magnet of uniform magnetic field; At least one can produce the low temperature gradients coil of magnetic field gradient in surveyed area; At least one can receive and dispatch the low temperature radio-frequency coil of the radiofrequency signal in surveyed area, this low temperature radio-frequency coil configuration is used for cooling, this system comprises following at least a kind of material: a kind of non-superconducting material that electric conductivity is higher than copper when being cooled to the 77K temperature, superconductor or low-temperature conductive material, described low-temperature conductive material comprises high temperature superconducting materia, described at least one low temperature radio-frequency coil during by the described 77K of being cooled to the electric conductivity non-superconducting material higher than copper be made.
14. the magnetic resonance imaging system of liquid nitrogen refrigerating according to claim 13 is characterized in that: wherein said at least one low temperature radio-frequency coil is Two-dimensional electron material structure or carbon nano tube structure.
15. the magnetic resonance imaging system of a liquid nitrogen refrigerating is characterized in that: this system comprises: one can produce at surveyed area the high-temperature superconductor master magnet of uniform magnetic field; At least one can produce the low temperature gradients coil of magnetic field gradient in surveyed area; At least one can receive and dispatch the low temperature radio-frequency coil of the radiofrequency signal in surveyed area, this low temperature radio-frequency coil configuration is used for cooling, this system comprises following at least a kind of material: a kind of non-superconducting material that electric conductivity is higher than copper when being cooled to the 77K temperature, superconductor or low-temperature conductive material, described low-temperature conductive material comprises high temperature superconducting materia, described high temperature master magnet is placed in the first vacuum chamber, and described low temperature radio-frequency coil and low temperature gradients coil are placed in the second vacuum chamber.
16. the magnetic resonance imaging system of the liquid nitrogen refrigerating of a liquid nitrogen refrigerating is characterized in that: this system comprises: one can produce at surveyed area the high-temperature superconductor master magnet of uniform magnetic field; At least one can produce the low temperature gradients coil of magnetic field gradient in surveyed area; At least one can receive and dispatch the low temperature radio-frequency coil of the radiofrequency signal in surveyed area, this low temperature radio-frequency coil configuration is used for cooling, this system comprises following at least a kind of material: a kind of non-superconducting material that electric conductivity is higher than copper when being cooled to the 77K temperature, superconductor or low-temperature conductive material, described low-temperature conductive material comprises high temperature superconducting materia, and described high-temperature superconductor master magnet, low temperature radio-frequency coil and low temperature gradients coil are placed on respectively in separately vacuum chamber.
17. the magnetic resonance imaging system of a liquid nitrogen refrigerating is characterized in that: this system comprises: one can produce at surveyed area the high-temperature superconductor master magnet of uniform magnetic field; At least one can produce the low temperature gradients coil of magnetic field gradient in surveyed area; At least one can receive and dispatch the low temperature radio-frequency coil of the radiofrequency signal in surveyed area, this radio-frequency coil configuration is used for cooling, this system comprises following at least a kind of material: a kind of non-superconducting material that electric conductivity is higher than copper when being cooled to the 77K temperature, superconductor or low-temperature conductive material, described low-temperature conductive material comprises high temperature superconducting materia, and it is indoor that described low temperature radio-frequency coil and low temperature gradients coil are placed on same common vacuum.
18. the magnetic resonance imaging system of liquid nitrogen refrigerating according to claim 17 is characterized in that: wherein said low temperature radio-frequency coil and low temperature gradients coil are thermally coupled to same common heat sink.
19. the magnetic resonance imaging system of a liquid nitrogen refrigerating is characterized in that: this system comprises: one can produce at surveyed area the high-temperature superconductor master magnet of uniform magnetic field, at least one can produce the low temperature gradients coil of magnetic field gradient in surveyed area, at least one can receive and dispatch the low temperature radio-frequency coil of the radiofrequency signal in surveyed area, this low temperature radio-frequency coil configuration is used for cooling, this system comprises following at least a kind of material: the electric conductivity a kind of non-superconducting material higher than copper when being cooled to the 77K temperature, a kind of superconductor or low-temperature conductive material, described low-temperature conductive material comprises high temperature superconducting materia, described high-temperature superconductor master magnet is undertaken cooling by the first low-temperature cooling system, described low temperature radio-frequency coil is undertaken cooling by the second low-temperature cooling system, described low temperature gradients coil is undertaken cooling by the 3rd low-temperature cooling system.
20. the magnetic resonance imaging system of a liquid nitrogen refrigerating is characterized in that: this system comprises: one can produce at surveyed area the high-temperature superconductor master magnet of uniform magnetic field; At least one can produce the low temperature gradients coil of magnetic field gradient in surveyed area; At least one can receive and dispatch the low temperature radio-frequency coil of the radiofrequency signal in surveyed area, this low temperature radio-frequency coil configuration is used for cooling, this system comprises following at least a kind of material: a kind of non-superconducting material that electric conductivity is higher than copper when being cooled to the 77K temperature, superconductor or low-temperature conductive material, described low-temperature conductive material comprises high temperature superconducting materia, described high-temperature superconductor master magnet is undertaken cooling by the first low-temperature cooling system, described low temperature radio-frequency coil and low temperature gradients coil are undertaken cooling by the second low-temperature cooling system.
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