Background technology
MR imaging apparatus is widely used in clinical medicine inspection and treatment, and MR imaging apparatus of the prior art mainly comprises frame, sick bed, gradient coil, radio-frequency coil and control and image re-construction system.When to torso portion imaging, can adopt body coil, to launch and/or received RF pulse signal.As shown in Figure 1, existing body coil is mainly made up of cylindrical shell 1, multiple coil unit 2 and electric capacity 3, mainly for generation of radio-frequency field.
Carrying out in the process of MRI scan, people knows from experience absorption portion radio-frequency power, measures with specific absorption rate (SpecialAbsorption Rate, SAR).If radio-frequency coil emissive power is larger, after scanning a period of time, the shell temperature of body local can increase under electric field.According to U=I*Z, the voltage that U is electric capacity, I is the electric current that flows through electric capacity, the impedance that Z is electric capacity, wherein I is certain, and impedance Z is larger, and voltage is larger, the RF field intensity producing between human body and electric capacity is just larger, and the electric current that human epidermal induction produces is just larger, and SAR is also just larger; Impedance is less, and voltage is less, and the RF field intensity producing between human body and electric capacity is just less, and the electric current that human epidermal produces is just less, and SAR is also just less.So the impedance Z of electric capacity 3 affects near the RF field intensity it, thereby affects the induction current of human body and the SAR of human body.The numerical value C of electric capacity and the impedance Z relation that is inversely proportional to again, thus when capacitance values large, impedance is little, thus the electric current that human body produces under RF field intensity is less; Capacitance values is little, and impedance is large, and the RF field intensity of its near zone is large, thereby the induction current that human body produces under RF field intensity is just large.The RF field intensity that the SAR of human body is subject to along with epidermis increases and increases, and reduces and reduces.Some patient feels uneasy or feels uncertain the temperature rise of this body surface.Some existing MR imaging apparatus attempts to avoid remarkable temperature to raise by strengthening the approach that electric capacity reduces impedance.But the change of electric capacity can cause the variation of coil parameter, adjust relative complex.
Summary of the invention
The problem to be solved in the present invention is to provide a kind of magnetic resonance body coil, both can effectively solve the higher problem of body local SAR, can prevent that again the heat that electric capacity produces is delivered to body coil inside, makes the body temperature of patient in the time doing magnetic resonance examination can maintain normal level.
For addressing the above problem, magnetic resonance body coil of the present invention, comprise cylindrical shell, multiple coil unit and electric capacity, described multiple coil unit is fixed on described cylindrical shell, described multiple electric capacity is arranged on described coil unit, also comprise the hollow body for a kind of heat eliminating medium of delivery, described hollow body is between described coil unit and cylindrical shell, and along the circumferential extension of described cylindrical shell.
Further, be arranged on described coil unit and form an annular with multiple electric capacity of one end, described hollow body is positioned at the below of described annular.
Further, the multiple electric capacity that are arranged on the axial same position of described cylindrical shell form an annular, and the below of described annular is provided with described hollow body.
Further, the surface of contact of described hollow body and described cylindrical shell is circular arc, and the surface of contact of described hollow body and described coil unit is circular arc.
Further, the length that described hollow body circumferentially extends along described cylindrical shell is less than or equal to the circumferential girth of described cylindrical shell.
Further, one end of described hollow body has the input port for importing described heat eliminating medium, and the other end has the delivery outlet for deriving described heat eliminating medium.
Further, the sub-hollow body that described hollow body is extended by multiple circumferencial directions along described cylindrical shell connects and composes successively, one end of each described sub-hollow body has the input port for importing described heat eliminating medium, and the other end has the delivery outlet for deriving described heat eliminating medium.
Further, described heat eliminating medium is the one in gaseous state or the liquid cooling medium under room temperature.
Further, described hollow body and described cylindrical shell are made integral piece.
Further, between described hollow body and described cylindrical shell, adopt nonmetal screw to be connected or bonding method connect in one.
Further, between described hollow body and described coil unit, adopt nonmetal screw to be connected or bonding method connect in one.
Magnetic resonance body coil provided by the invention, between coil unit and cylindrical shell, be provided with hollow body, the heat that in hollow body, mobile heat eliminating medium produces electric capacity is taken away, and has prevented that the heat that electric capacity produces is delivered to body coil inside, avoids the heat producing that patient is done not feel like oneself; Meanwhile, hollow body is arranged on electric capacity below, and electric capacity, to the direction jack-up away from human body, has been increased to the distance between human body and electric capacity, has reduced SAR value, efficiently solves the higher problem of local SAR value; In addition, magnetic resonance body coil of the present invention also has simple in structure, transformation or the lower advantage of production cost.
Embodiment:
For above-mentioned purpose of the present invention, feature and advantage can be become apparent more, below in conjunction with drawings and Examples, the specific embodiment of the present invention is described in detail.
For solving problems of the prior art, magnetic resonance body coil provided by the invention, comprise cylindrical shell, multiple coil unit and electric capacity, described multiple coil unit is fixed on described cylindrical shell, described multiple electric capacity is arranged on described coil unit, also comprise the hollow body for a kind of heat eliminating medium of delivery, described hollow body is between described cylindrical shell and coil unit, and along the circumferential extension of described cylindrical shell.In the time carrying out MRI scan, the heat that mobile heat eliminating medium can produce electric capacity in hollow body be taken away, and prevents that heat that electric capacity produces is delivered to body coil inside patient is done not feel like oneself, and has improved user's experience.
Fig. 2 is the structural representation of one embodiment of the present invention.For simplicity, in figure, only show the critical piece of magnetic resonance body coil, omitted between the each parts of magnetic resonance body coil, between magnetic resonance body coil and magnetic resonance equipment miscellaneous part be connected wire and for arranging that these connect the set grooves of wires.
This magnetic resonance body coil comprises cylindrical cylindrical shell 100 and is fixed on eight coil units 210,220,230,240 on cylindrical shell 100 etc.These eight coil unit equal and opposite in directions, and cylindrical along the axial formation one of cylindrical shell 100.It should be noted that, " cylindrical " described herein and " annular " below addressed not only comprises strict geometrically " cylindrical ", " annular ", also comprises that those xsects are that ellipse, polygon etc. are similar to circular " cylindrical ", " annular ".
On coil unit and/or between coil unit, be also provided with electric capacity, for removing the coupling between coil unit.As shown in Figure 2, on each coil unit, be provided with two electric capacity, as coil unit 230 two ends are respectively arranged with electric capacity 231,232; Between adjacent two coil units, be provided with two electric capacity, as being provided with electric capacity 233,234 between coil unit 230,240.
Fig. 3 is that the magnetic resonance body coil shown in Fig. 2 is perpendicular to the circumferential sectional view of cylindrical shell.Incorporated by reference to Fig. 2 and Fig. 3, between coil unit and cylindrical shell 100, be provided with hollow body 310,320, hollow body 310,320 is fixed on cylindrical shell 100 and along the circumferential extension of cylindrical shell 100.Hollow body 310,320 is for a kind of heat eliminating medium of delivery, and in the time carrying out magnetic resonance imaging, the heat that in hollow body, mobile heat eliminating medium can produce electric capacity be taken away, and prevents that heat that electric capacity produces is delivered to body coil inside patient is done not feel like oneself.In present embodiment, electric capacity is arranged on the two ends of coil unit, wherein, be arranged on coil unit with multiple electric capacity of one end circumferential formation one annular along cylindrical shell 100.Hollow body 310 and 320 is just separately positioned on above-mentioned two annular belows.The benefit that hollow body is arranged to electric capacity below is, hollow body has certain height, and it to the direction jack-up away from human body, slightly increases distance between electric capacity and human body electric capacity, has reduced SAR value.Simultaneously, the distance strengthening between electric capacity and human body only can reduce the RF field intensity between human body and electric capacity, can't affect the RF field intensity of whole body coil for imaging, so signal to noise ratio (S/N ratio) (SNR) impact on this regional imaging little, MRI imaging effect can't be subject to very large impression.
Certainly, magnetic resonance body coil of the present invention is not limited in present embodiment, embodiment as an alternative, and hollow body can be arranged on the below of multiple electric capacity of looping, also can not be arranged on the below of multiple electric capacity of looping; Between cylindrical shell and coil unit, two hollow bodies can be only set, multiple hollow bodies also can be set.As another preferred embodiment be along cylindrical shell axially, be distributed with multiple annulars that formed by electric capacity, a hollow body is all set below each annular.
Fig. 4 is that the magnetic resonance body coil shown in Fig. 2 is parallel to the circumferential sectional view of cylindrical shell.Please refer to Fig. 4, hollow body 320 is between cylindrical shell and coil unit, and hollow body 320 is circular arc with the surface of contact of cylindrical shell 100, with the surface of contact of each coil unit be also circular arc.In the present embodiment, hollow body 310,320 and cylindrical shell 100 are made to integral piece, and hollow body is connected by bonding method with coil unit.Mode as an alternative, between hollow body and cylindrical shell, can also adopt bonding method to be connected between hollow body and coil unit or nonmetal screw connects.
Please continue with reference to figure 4, hollow body 320 is along the circumferential extension of cylindrical shell 100, and hollow body 320 is less than the girth of the circumferencial direction of cylindrical shell 100 along the length of the circumferential extension of cylindrical shell 100.Certainly, in other embodiments, hollow body 320 can also equal the circumferential girth of cylindrical shell 100 along the length of the circumferential extension of cylindrical shell 100.Have the input port 321 for importing heat eliminating medium in one end of hollow body 320, the other end has the delivery outlet 322 of deriving heat eliminating medium.As a kind of substitute mode, a hollow body can also be divided into multistage, every section of hollow body can be defined as a sub-hollow body, be provided for importing the input port of described heat eliminating medium in one end of every sub-hollow body, the other end is provided for deriving the delivery outlet of described heat eliminating medium, so, a hollow body just includes multiple input ports and corresponding delivery outlet, can make the heat producing in cylindrical shell be taken away fast.
About the selection of heat eliminating medium, can be the liquid cooling medium under a kind of room temperature, particularly water, can be also the gaseous cooling medium under a kind of room temperature, particularly air.Can make the patient chamber of magnetic resonance equipment maintain one by the flow of heat eliminating medium in control hollow body and make to place oneself in the midst of the comfortable temperature of human body sensory of wherein testing.
Material about hollow body is selected, and in present embodiment, hollow body adopts the material identical with cylindrical shell, is specially fiberglass.Certainly, in other embodiments, cylindrical shell and hollow body also can select other to have material some strength and that specific inductive capacity is little.
In sum, magnetic resonance body coil of the present invention arranges hollow body between coil unit and cylindrical shell, and the heat that in hollow body, mobile heat eliminating medium produces electric capacity is taken away, prevent that the heat that electric capacity produces is delivered to body coil inside, avoids the heat producing that patient is done not feel like oneself; Meanwhile, hollow body is arranged on electric capacity below, and electric capacity, to the direction jack-up away from human body, has been increased to the distance between human body and electric capacity, has reduced SAR value, efficiently solves the higher problem of local SAR value; In addition, magnetic resonance body coil of the present invention also has simple in structure, transformation or the lower advantage of production cost.
Although the present invention discloses as above with preferred embodiment; so it is not in order to limit the present invention, any those skilled in the art, without departing from the spirit and scope of the present invention; when doing a little amendment and perfect, therefore protection scope of the present invention is worked as with being as the criterion that claims were defined.