Patent Publication Number: US-2012025829-A1

Title: Acoustically damped gradient coil

Description:
BACKGROUND 
     1. Technical Field 
     The invention includes embodiments that relate to a gradient coil such as that used in a magnetic resonance imaging device. The invention includes embodiments that relate to a method of making the gradient coil for use in a magnetic resonance imaging device. 
     2. Discussion of Related Art 
     Magnetic resonance imaging (MRI) is a known technique for acquiring images of the inside of the body of an examination subject. In a MRI device, rapidly switched gradient fields that are generated by a gradient coil assembly are superimposed on a static basic magnetic field that is generated by a basic field magnet system. The MRI device also has a radio-frequency system that beams radio-frequency signals into the examination subject for triggering magnetic resonance signals and picks up the resulting magnetic resonance signals from which magnetic resonance images are produced. 
     For generating gradient fields, suitable currents must be set in gradient coils of the gradient coil system. The amplitudes of the required currents amount to up to several hundred amperes. The current rise and decay rates can be up to several hundred kilo amperes per second. Given a basic magnetic field of the order of magnitude of 1 Tesla, Lorentz forces that lead to oscillations of the gradient coil system act on these time-variable currents in the gradient coils. These oscillations are transmitted to the surface of the MRI device via various propagation paths. In case of a Z-gradient coil, the Lorenz forces are predominantly radial in direction with some axial component due to the curvature of the static basic magnetic field. At the surface, the mechanical oscillations are converted into acoustic oscillations that ultimately lead to unwanted noise that may exceed the ambient background noise. The excessive noise generated during an MRI procedure may be unsettling to patients and irritating to physicians and technicians. 
     A number of passive and active noise-reduction techniques have been proposed for magnetic resonance apparatuses. For example, known passive noise reduction measures include the application of foamed materials for lining components toward the gradient coil system and/or the use of flexible layers like rubber, at and/or in the gradient coil system. 
     It may be desirable to have an improved MRI device with reduced noise that differs from those devices that are currently available. It may be desirable to have a method of noise reduction for an MRI device that differs from those methods that are currently available. 
     BRIEF DESCRIPTION 
     In accordance with an embodiment of the invention, a gradient coil assembly is provided. The gradient coil assembly includes a cylindrical element. The cylindrical element has an inner surface and an outer surface. At least one first isolation material is disposed over the outer surface of the cylindrical element. A conducting material is disposed over the isolation material. 
     In accordance with an embodiment of the invention, a gradient coil assembly is provided. The gradient coil assembly includes a cylindrical element. The cylindrical element has an inner surface and an outer surface. A first isolation material is disposed over the outer surface of the cylindrical element. A conducting material is disposed over the first isolation material. A second isolation material is disposed over the conducting material. The conducting material is disposed between the first isolation material and the second isolation material. 
     In accordance with an embodiment of the invention, a gradient coil assembly is provided. The gradient coil assembly includes a cylindrical element. The cylindrical element has an inner surface and an outer surface. A first isolation material is disposed over the outer surface of the cylindrical element. A second isolation material is disposed over the first isolation material. A conducting material is disposed over the second isolation material. A third isolation material is disposed over the conducting material. The conducting material is disposed between the second isolation material and the third isolation material. 
     In accordance with an embodiment of the invention, an apparatus is provided. The apparatus comprises at least one component contributing to generation of mechanical oscillations. The component comprises a cylindrical element, at least one first isolation material, and a conducting material. The cylindrical element has an inner surface and an outer surface. The isolation material is disposed over the outer surface of the cylindrical element. The conducting material is disposed over the isolation material. 
     In accordance with an embodiment of the invention, a magnetic resonance imaging device is provided. The device comprises a magnet and a gradient coil assembly located within the magnet. The gradient coil assembly includes a cylindrical element. The cylindrical element has an inner surface and an outer surface. At least one first isolation material is disposed over the outer surface of the cylindrical element. A conducting material is disposed over the isolation material. 
     In accordance with an embodiment of the invention, a gradient coil assembly is provided. The gradient coil assembly comprises a cylindrical element. The cylindrical element has an inner surface and an outer surface. A plurality of grooves are disposed on the outer surface of the cylindrical element; wherein the grooves comprise alternately disposed projections and recesses. A first isolation material comprising silicone, rubber, or compliant epoxy having compliance in a range from about 0.1 millimeters per Newton to about 1 millimeter per Newton is disposed over the outer surface of the cylindrical element such that the first isolation material is aligned with the recesses of the cylindrical element. A second isolation material comprising silicone, rubber, or compliant epoxy having compliance in a range from about 1 millimeter per Newton to about 10 millimeters per Newton is disposed over the outer surface of the cylindrical element. The second isolation material covers the projections on the outer surface of the cylindrical element and the first isolation material aligned with the recesses of the cylindrical element. A conducting material is disposed over the second isolation material. The conducting material is aligned with the recesses of the cylindrical element. A third isolation material comprising silicone, rubber, or compliant epoxy having compliance in a range from about 0.1 millimeters per Newton to about 1 millimeter per Newton is disposed over the conducting material. The conducting material is disposed between the second isolation material and the third isolation material. 
     In accordance with an embodiment of the invention, a method is provided. The method includes a first step of providing a cylindrical element having an inner surface and an outer surface. A first step includes disposing at least one first isolation material over the outer surface of the cylindrical element. A second step includes disposing a conducting material over the isolation material. 
     In accordance with an embodiment of the invention, a method is provided. The method includes a first step of providing a cylindrical element having an inner surface and an outer surface. A plurality of grooves are disposed on the outer surface of the cylindrical element. The grooves comprise alternately disposed projections and recesses. A second step includes disposing a first isolation material over the outer surface of the cylindrical element such that the first isolation material is aligned with the recesses of the cylindrical element. A third step includes disposing a second isolation material is disposed over the outer surface of the cylindrical element. The second isolation material covers the projections on the outer surface of the cylindrical element and the first isolation material aligned with the recesses of the cylindrical element. A fourth step includes disposing a conducting material over the second isolation material. The conducting material is aligned with the recesses of the cylindrical element. A fifth step includes disposing a third isolation material over the conducting material. The conducting material is disposed between the second isolation material and the third isolation material. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic view showing a gradient coil assembly in accordance with one embodiment of the invention. 
         FIG. 2  is a schematic view showing a gradient coil assembly in accordance with one embodiment of the invention. 
         FIG. 3  is a schematic view showing a gradient coil assembly in accordance with one embodiment of the invention. 
         FIG. 4  is a schematic view showing a gradient coil assembly in accordance with one embodiment of the invention. 
         FIG. 5  is a schematic view showing a gradient coil assembly in accordance with one embodiment of the invention. 
         FIG. 6  is a schematic view showing a gradient coil assembly in accordance with one embodiment of the invention. 
         FIG. 7  is a schematic view showing a cylindrical element in accordance with one embodiment of the invention. 
         FIG. 8  is a schematic view showing a gradient coil assembly in accordance with one embodiment of the invention. 
         FIG. 9  is a schematic view showing a gradient coil assembly in accordance with one embodiment of the invention. 
         FIG. 10  is an isometric view showing an MRI device in accordance with one embodiment of the invention. 
         FIG. 11  is a method of forming a gradient coil assembly in accordance with one embodiment of the invention. 
         FIG. 12  is a method of forming a gradient coil assembly in accordance with one embodiment of the invention. 
         FIG. 13  is a schematic view of a cylindrical element in accordance with an embodiment of the invention. 
         FIG. 14  is a schematic view of a cylindrical element in accordance with an embodiment of the invention. 
         FIG. 15  is a schematic view of a cylindrical element in accordance with an embodiment of the invention. 
         FIG. 16  is a schematic view of a cylindrical element in accordance with an embodiment of the invention. 
         FIG. 17  is a schematic view of a cylindrical element in accordance with an embodiment of the invention. 
         FIG. 18  is a schematic view of a cylindrical element in accordance with an embodiment of the invention. 
         FIG. 19  is a schematic view of a cylindrical element in accordance with an embodiment of the invention. 
         FIG. 20  is a schematic view of a cylindrical element in accordance with an embodiment of the invention. 
         FIG. 21  is a graph illustrating the vibration at resonance of a gradient coil assembly in accordance with an embodiment of the invention. 
         FIG. 22  is a graph illustrating the air-borne noise of the gradient coil assembly in accordance with an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     The invention includes embodiments that relate to a gradient coil such as that used in a magnetic resonance imaging device. The invention includes embodiments that relate to a method of making the gradient coil for use in a magnetic resonance imaging device. 
     As discussed above, the vibrations caused during the operation of an MRI device result in the production of airborne noise that may constitute an annoyance to the patient, the operating staff and other persons in the vicinity of the MRI device. The vibrations of the gradient coil and of the magnet, and their transmission to an RF resonator and a patient couch in the interior of the magnet and/or the gradient coil, are expressed in inadequate clinical image quality which can even lead to misdiagnosis, especially in the case of functional imaging, fMRI. Costs are also incurred for providing a vibration-isolation system setup to prevent transmission of the vibrations to the ground, or vice versa. 
     Embodiments of the invention described herein address the noted shortcomings of the state of the art. The gradient coil assembly described herein fills the needs described above by providing an improved vibroacoustic isolation of vibrating conductors. These gradient coils could potentially offer MRI devices with reduced noise levels and hence provide MRI devices that provide better images. Conductors inside the gradient coil experience large Lorenz forces due to the interaction of the AC current with the static field of the magnet. Embodiments disclosed herein provide a gradient coil assembly wherein a conducting material is mechanically isolated from a cylindrical element on which the conducting material is wound. The isolation is done by using layers of isolation materials so that less vibration will be transmitted to the structure when the conductors deflect under the influence of the Lorenz forces. The advantage of this approach is that it reduces structure-borne noise at the source rather than dealing with noise itself. The gradient coil assembly disclosed herein is formed by disposing at least one layer of an isolation material on the surface of a cylindrical element that forms the gradient coil assembly. A conducting material is disposed over the first isolation material. In certain embodiments a second isolation material is disposed over the conducting material such that the conducting material is disposed between the first isolation material and the second isolation material. A third isolation material may be disposed over second isolation material. In certain embodiments, the second isolation material may be disposed over the first isolation material, the conducting material is disposed over the second isolation material, and the third isolation material may be disposed over the conducting material in manner such that the conducting material is disposed between the second isolation material and the third isolation material. Depositing the layers of isolation materials and depositing the conducting material over or in between the isolation materials allows the conducting material to vibrate over the isolation material without further transmission of vibration from the gradient coil assembly to other parts of the apparatus of the device. 
     One or more specific embodiments of the present invention will be described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
     When introducing elements of various embodiments of the present invention, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Moreover, the use of “top,” “bottom,” “above,” “below,” and variations of these terms is made for convenience, but does not require any particular orientation of the components unless otherwise stated. As used herein, the terms “disposed over” or “deposited over” or “disposed between” refers to both secured or disposed directly in contact with and indirectly by having intervening layers there between. 
     As used herein, the phrase “isolation material” refers to a highly compliant elastomeric material used to allow vibrating elements to move freely relative to their surroundings and not transmit their vibrational energy. As known to one skilled in the art, up to a certain limit there is a linear relationship between the force (F) applied to a material and the extent to which the material deforms (D). Hook&#39;s law provides an equation 
         D/F=C    I
 
     wherein C is a constant, and is defined as the compliance of the material in millimeters per Newton. For example, if a cord needs 1256 Newton (F) to be extended by 20 millimeters (D), C is equal to about 0.016 millimeters per Newton (20/1256), or 16 micrometers per Newton. To be effective in this application the isolation material should have a mechanical compliance value of at least 10 times that of the surrounding material. The isolation material may additionally possess damping properties to further remove energy from the vibrating elements themselves. A compliant isolation material that includes a damping loss factor of at least 0.02 would be additionally effective in this application. 
     Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it may be about related. Accordingly, a value modified by a term such as “about” is not limited to the precise value specified. In some instances, the approximating language may correspond to the precision of an instrument for measuring the value. 
     In one embodiment, a gradient coil assembly  100  is provided. Referring to  FIG. 1  a schematic top view  110  and a cross sectional view  112  of the gradient coil assembly  100  is provided. The gradient coil assembly  100  includes a cylindrical element  114 . The cylindrical element  114  has an inner surface  116  and an outer surface  118 . At least one first isolation material  120  is disposed over the outer surface  118  of the cylindrical element  114 . A conducting material  122  is disposed over the isolation material  120  thus isolating the conducting material  122  from being in direct contact with the outer surface  118  of the cylindrical element  114 . In one embodiment, a protective covering (not shown in figure) may be disposed over the second isolation material. In one embodiment, an insulating covering (not shown in figure) may be disposed over the protective covering. In one embodiment, the cylindrical element  110  may comprise any material known to one skilled in the art as useful for a cylindrical element in a gradient coil assembly. In one embodiment, the cylindrical element  110  comprises epoxy or fiberglass. 
     In one embodiment, a gradient coil assembly  200  is provided. Referring to  FIG. 2  a schematic top view  210  and a cross sectional view  212  of the gradient coil assembly  200  is provided. The gradient coil assembly  200  includes a cylindrical element  214 . The cylindrical element  214  has an inner surface  216  and an outer surface  218 . At least one first isolation material  220  is disposed over a conducting material  222 . The isolation material  220  is disposed in a manner such that the isolation material  220  forms a sleeve or encapsulation over the conducting material  222 . The conducting material  222  encapsulated in the isolation material  220  is then wound round the cylindrical element  214 . The isolation material  220  thus isolates the conducting material  222  from being in direct contact with the outer surface  218  of the cylindrical element  214 . In one embodiment, a protective covering (not shown in figure) may be disposed over the second isolation material. In one embodiment, an insulating covering (not shown in figure) may be disposed over the protective covering. 
     In one embodiment, a gradient coil assembly  300  is provided. Referring to  FIG. 3  a schematic cross sectional view  310  of the gradient coil assembly  300  is provided. The gradient coil assembly  300  includes a cylindrical element  312 . The cylindrical element  312  has an inner surface  314  and an outer surface  316 . A first isolation material  318  is disposed over the outer surface  316  of the cylindrical element  312 . A conducting material  320  is disposed over the first isolation material  318 . A second isolation material  322  is disposed over the conducting material  320  such that the conducting material  320  is disposed between the first isolation material  318  and the second isolation material  322 . The first isolation material  318  and the second isolation material  322  together assist in isolating the conducting material  320  from being in direct contact with the outer surface  316  of the cylindrical element  312 . In one embodiment, a protective covering (not shown in figure) may be disposed over the second isolation material. In one embodiment, an electrically insulating covering (not shown in figure) may be disposed over the protective covering. 
     In one embodiment, a gradient coil assembly  400  is provided. Referring to  FIG. 4  a schematic cross sectional view  410  of the gradient coil assembly  400  is provided. The gradient coil assembly  400  includes a cylindrical element  412 . The cylindrical element  412  has an inner surface  414  and an outer surface  416 . A first isolation material  418  is disposed over the outer surface  416  of the cylindrical element  412 . A second isolation material  422  is disposed over a conducting material  420  in a manner such that the second isolation material  422  forms a sleeve or encapsulation over the conducting material  420 . The conducting material  420  encapsulated in the first isolation material  418 , is then wound round the first isolation material  418 . The first isolation material  418  and the second isolation material  422  thus isolate the conducting material  420  from being in direct contact with the outer surface  416  of the cylindrical element  412 . In one embodiment, a protective covering (not shown in figure) may be disposed over the second isolation material. In one embodiment, an insulating covering (not shown in figure) may be disposed over the protective covering. 
     In one embodiment, a gradient coil assembly  500  is provided. Referring to  FIG. 5  a schematic cross sectional view  510  of the gradient coil assembly  500  is provided. The gradient coil assembly  500  includes a cylindrical element  512 . The cylindrical element  512  has an inner surface  514  and an outer surface  516 . A first isolation material  518  is disposed over the outer surface  516  of the cylindrical element  512 . A second isolation material  520  is disposed over the first isolation material  518 . A conducting material  522  is disposed over the second isolation material  520 . A third isolation material  524  is disposed over the conducting material  522  such that the conducting material  522  is disposed between the second isolation material  520  and the third isolation material  524 . The first isolation material  518 , the second isolation material  520 , and the third isolation material  524  together assist in isolating the conducting material  522  from being in direct contact with the outer surface  516  of the cylindrical element  512 . In one embodiment, a protective covering (not shown in figure) may be disposed over the second isolation material. In one embodiment, an insulating covering (not shown in figure) may be disposed over the protective covering. 
     In one embodiment, a gradient coil assembly  600  is provided. Referring to  FIG. 3  a schematic cross sectional view  610  of the gradient coil assembly  600  is provided. The gradient coil assembly  600  includes a cylindrical element  612 . The cylindrical element  612  has an inner surface  614  and an outer surface  616 . A first isolation material  618  is disposed over the outer surface  616  of the cylindrical element  612 . A conducting material  620  is disposed over the first isolation material  618 . A second isolation material  622  is disposed over the conducting material  620  such that the second isolation material  622  forms a sleeve over the conducting material  620 , as described in  FIG. 2  above. A third isolation material  624  is then disposed over the second isolation material  622  and the conducting material  620 . The first isolation material  618 , the second isolation material  622 , and the third isolation material  624  together assist in isolating the conducting material  620  from being in direct contact with the outer surface  616  of the cylindrical element  612 . In one embodiment, a protective covering (not shown in figure) may be disposed over the second isolation material. In one embodiment, an insulating covering (not shown in figure) may be disposed over the protective covering. 
     In one embodiment, a cylindrical element  700  comprises a plurality of grooves  710  disposed on the outer surface of the cylindrical element  700 . Referring to  FIG. 7 , a schematic view of a cross section of a cylindrical element  700  is provided. A plurality of grooves  710 , are disposed on the outer surface  712  of the cylindrical element  700 . The grooves comprise alternately disposed projections  714  and recesses  716 . 
     In one embodiment, a gradient coil assembly  800  is provided. Referring to  FIG. 8  a schematic view of a cross section of the gradient coil assembly  800  is provided. The gradient coil assembly  800  includes a cylindrical element  810 . The cylindrical element  810  has an inner surface  812  and an outer surface  814 . A first isolation material  816  is disposed over the outer surface  814  of the cylindrical element  810 . A second isolation material  818  is disposed over the first isolation material  816 . A conducting material  820  is disposed over the second isolation material  818 . A third isolation material  822  is disposed over the conducting material  820 . The conducting material  820  is disposed between the second isolation material  818  and the third isolation material  822 . 
     In one embodiment, the conducting material comprises at least one metal selected from group VIIIB, group IB, or group IIIA of the periodic table. In one embodiment, the conducting material comprises copper, gold, silver, or aluminum. In one embodiment, the conducting material comprises copper. 
     In various embodiments, the first isolation material  120 ,  220 ,  318 ,  418 ,  518 ,  618 ,  816 , the second isolation material  322 ,  422 ,  522 ,  622 ,  818  and the third isolation material  524 ,  624 ,  822  employed in the gradient coil assemblies  100 ,  200 ,  300 ,  400 ,  500 ,  600 ,  800  discussed above include highly compliant materials that can assist in mechanical isolation of vibration. In one embodiment, the first isolation material comprises a material having compliance greater than about 0.1 millimeters. In another embodiment, the first isolation material comprises a material having compliance greater than about 0.2 millimeters. In yet another embodiment, the first isolation material comprises a material having compliance greater than about 0.3 millimeters. In one embodiment, the first isolation material comprises a material, having compliance in a range from about 0.1 millimeters per Newton to 1.0 millimeter per Newton. In another embodiment, the first isolation material comprises a material having compliance in a range from about 0.2 millimeters per Newton to 0.9 millimeters per Newton. In yet another embodiment, the first isolation material comprises a material having compliance in a range from about 0.3 millimeters per Newton to 0.8 millimeters per Newton. In some embodiments, the first isolation material comprises a material, having compliance in a range bounded by any combination of upper and lower limits as described above. 
     In one embodiment, the first isolation material comprises silicone, rubber, or epoxy. In one embodiment, the first isolation material comprises silicone, having compliance of greater than about 0.1 millimeters. In one embodiment, the first isolation material comprises silicone, having compliance in a range from about 0.1 millimeters per Newton to 1.0 millimeter per Newton. In one embodiment, the first isolation material may be shaped in the form of a cord or a sheet. 
     In one embodiment, the second isolation material  322 ,  422 ,  522 ,  622 ,  818  comprises a material having compliance, of greater than about 1 millimeter. In another embodiment, the second isolation material comprises a material having compliance, of greater than about 2 millimeter. In yet another embodiment, the second isolation material comprises a material having compliance, of greater than about 3 millimeter. In one embodiment, the second isolation material comprises a material having compliance, in a range from about 1 millimeter per Newton to 10 millimeters per Newton. In another embodiment, the second isolation material comprises a material compliance in a range from about 2 millimeters per Newton to 9 millimeters per Newton. In yet another embodiment, the second isolation material comprises a material compliance in a range from about 3 millimeters per Newton to 8 millimeters per Newton. In some embodiments, the first isolation material comprises a material, having compliance in a range bounded by any combination of upper and lower limits as described above. 
     In one embodiment, the second isolation material comprises rubber. In one embodiment, the second isolation material comprises rubber, having compliance in a range from about 1 millimeter per Newton to 10 millimeters per Newton. In one embodiment, the second isolation material may be shaped in the form of a sheet. 
     In one embodiment, the third isolation material  524 ,  624 ,  822  comprises a material having compliance greater than about 0.1 millimeters. In another embodiment, the third isolation material comprises a material having compliance greater than about 0.2 millimeters. In yet another embodiment, the third isolation material comprises a material having compliance greater than about 0.3 millimeters. In one embodiment, the third isolation material comprises a material having compliance in a range from about 0.1 millimeters per Newton to 1.0 millimeter per Newton. In another embodiment, the third isolation material comprises a material having compliance in a range from about 0.2 millimeters per Newton to 0.9 millimeters per Newton. In yet another embodiment, the third isolation material comprises a material having compliance in a range from about 0.3 millimeters per Newton to 0.8 millimeters per Newton. In some embodiments, the third isolation material comprises a material, having compliance in a range bounded by any combination of upper and lower limits as described above. 
     In one embodiment, the third isolation material comprises silicone, rubber or epoxy. In one embodiment, the third isolation material comprises silicone, having compliance in a range from about 0.1 millimeters per Newton to 1 millimeter per Newton. In one embodiment, the third isolation material may be shaped in the form of a cord or a sheet. 
     In one embodiment, a gradient coil assembly  900  may be covered with a protecting covering  924 . In one embodiment, an insulating covering  926  may be disposed over the protective covering  924 . The protective covering  924  functions to hold in place the layers of isolation materials  916 ,  918 , and  922  and the conducting material  920  that are disposed over the cylindrical element  910 . Referring to  FIG. 9 , a schematic view of a cross section of the gradient coil assembly  900  is provided. The gradient coil assembly  900  includes a cylindrical element  910 . The cylindrical element  910  has an inner surface  912  and an outer surface  914 . A first isolation material  916  is disposed over the outer surface  914  of the cylindrical element  910 . A second isolation material  918  is disposed over the first isolation material  916 . A conducting material  920  is disposed over the second isolation material  918 . A third isolation material  922  is disposed over the conducting material  920 . The conducting material  920  is disposed between the second isolation material  918  and the third isolation material  922 . A protective covering  924  is disposed over the surface of the gradient coil assembly  900  such that the protective covering covers the cylindrical element and the isolation materials and conducting materials disposed over the cylindrical element. An insulating covering  926  is then disposed over the protective covering. In one embodiment, the protective covering  924  comprises a polymer material. In one embodiment, the insulating covering  926  comprises an epoxy layer. In one embodiment, one embodiment, the insulating covering  926  comprises fiberglass. In one embodiment, the protective covering  922  is provided to prevent the insulating covering  926  from coming in contact with the isolation materials  916 ,  918 ,  922  or the conducting material  920  during the initial curing process when the insulating covering, for example, an epoxy or a fiberglass covering is in a viscous liquid state. In various embodiments, the material used to form the insulating covering  926  may have a much lower compliance than the isolation materials  916 ,  918  and  922  and may hence lead to reducing the effectiveness of the isolation materials if the insulating covering were to come into contact with the conducting material. 
     One embodiment is an MRI device  1000  comprising a gradient coil assembly. The gradient coil assembly may include any of the gradient coils  100 - 600 ,  800 , and  900 . Referring to  FIG. 10 , an isometric view of a MRI device is provided. The MRI device  1000  includes a magnet assembly  1010  that surrounds a gradient coil assembly  1012 , and a radio frequency (RF) coil assembly  1014 . The RF coil assembly may be separate stand along tube disposed within the MRI device  1000 . A patient positioning area  1016  is defined through the MRI device  1000  through the longitudinal axis  1018 . The gradient coil assembly  1012  comprises a cylindrical element  1020  having an inner surface  1022  and an outer surface  1024 . At least one first isolation material  120 , and a conducting material  122  are disposed on the outer surface  1024  of the cylindrical element  1020 . During operation of the MRI device  1000  the magnet assembly  1010  provides a static magnetic field while the gradient coil assembly  1012  generates a magnetic filed gradient for use in producing magnetic resonance images. The RF coil assembly  1014  transmits a radio frequency pulse and detects a plurality of MR signals induced from a subject being imaged. In particular, the isolation material  120  assists in reducing the vibroacoustic energy, and therefore acoustic noise, produced by vibrations of the gradient coil assembly  1012  during an imaging procedure. The reduced amount of acoustic noise produced by the MRI device  1000  provides a more patient friendly system and method of MRI. 
     In accordance with an embodiment of the invention, a magnetic resonance imaging device  1000  is provided. The device  1000  comprises a magnet  1010  and a gradient coil assembly  1012  located within the magnet. The gradient coil assembly  1012  includes a cylindrical element  114 . The cylindrical element  114  has an inner surface  116  and an outer surface  118 . A first isolation material  120  is disposed over the outer surface  118  of the cylindrical element  114 . A conducting material  122  is disposed over the isolation material  120 . The conducting material  122  is isolated from the outer surface  118  of the cylindrical element  114  by the isolation material  120 . 
     In accordance with an embodiment of the invention, an apparatus is provided. In one embodiment, the apparatus comprises a MRI device  1000 . The apparatus comprises at least one component contributing to generation of mechanical oscillations. The component includes a cylindrical element  114 . The cylindrical element  114  has an inner surface  116  and an outer surface  118 . A first isolation material  120  is disposed over the outer surface  118  of the cylindrical element  114 . A conducting material  122  is disposed over the isolation material  120 . The conducting material  122  is isolated from the outer surface  118  of the cylindrical element  114  by the isolation material  120 . The component includes a gradient coil assembly that may include any of the gradient coils  100 - 600 ,  800 , and  900 . 
     In accordance with an embodiment of the invention, a method  1100  of forming a gradient coil assembly in accordance with one embodiment of the invention is provided. Referring to  FIG. 11 , the method includes a first step  1110  of providing a cylindrical element having an inner surface  116  and an outer surface  118 . A second step  1112  includes disposing a first isolation material  120  over the outer surface  118  of the cylindrical element  114 . A third step  1114  includes disposing a conducting material  122  over the first isolation material  120 . A fourth step  1116  includes disposing a layer of a protective covering  924  on the surface of the cylindrical element  114 . A fifth step includes disposing a layer of a insulating covering  926  over the protective coating  924 . 
     In accordance with an embodiment of the invention, a method  1200  of forming a gradient coil assembly in accordance with one embodiment of the invention is provided. Referring to  FIG. 12 , the method includes a first step  1210  of providing a cylindrical element  910  having an inner surface  912  and an outer surface  914 . A plurality of grooves  710  are disposed on the outer surface  914  of the cylindrical element  910 . The grooves  710  comprise alternately disposed projections  714  and recesses  716 . A second step  1212  includes disposing a first isolation material  916  over the outer surface  114  of the cylindrical element  910  such that the first isolation material  916  is aligned with the recesses  716  of the cylindrical element  910 . A third step  1214  includes disposing a second isolation material  918  over the outer surface  914  of the cylindrical element  910  and the first isolation material  916  such that the second isolation material  918  covers the projections  714  on the outer surface  914  of the cylindrical element  910  and the first isolation material  916 . A fourth step  1216  includes disposing a conducting material  920  over the second isolation material  918 . The conducting material  920  is aligned with the recesses  716  of the cylindrical element  910 . A fifth step  1218  includes disposing a third isolation material  922  over the conducting material  920 . The conducting material  920  is disposed between the second isolation material  918  and the third isolation material  922 . A sixth step  1218  includes disposing a layer of a protective covering  924  on the surface of the cylindrical element  912 . A seventh step includes disposing a layer of a insulating covering  926  over the protective coating  924 . As used herein, the terms “first step”, “second step” etc., are meant merely to distinguish the steps and do not imply a mandated ordering of steps. Nor do these terms imply that intermediate steps could not be inserted between the enumerated steps. 
     Referring to  FIG. 13 , a cylindrical element  1300  is provided. The cylindrical element  1310  has an inner surface (not shown in figure) and an outer surface  1312 . A plurality of grooves  1314  are disposed on the outer surface of the cylindrical element. The grooves include a plurality of alternately disposed projections  1316  and recesses  1318 . A first isolation material  1320 , for example, a silicone cord having a thickness of 2 millimeters and a breadth of 4 millimeters, is disposed over the cylindrical element  1310 . The first isolation material  1320  is disposed such that the material is aligned to the recesses  1318  on the outer surface of the cylindrical element  1300 . Referring to  FIG. 14 , a second isolation material  1410  is disposed over the cylindrical element  1300 . The second isolation material  1410  is disposed such that it covers the entire outer surface  1312  of the cylindrical element including the projections  1316  and the first isolation material  1320  disposed in the recesses  1318 . Referring to  FIG. 15 , a conducting material  1510  is disposed over the second isolation material  1410 . The conducting material  1510  is disposed over the cylindrical element such that the conducting material  1510  is aligned to the recesses  1318 . The conducting material  1510  is wound over the second isolation material  1410  and is aligned to the first isolation material  1320  disposed in the recesses  1318 . Referring to  FIG. 16 , a third isolation material  1610  is disposed over the conducting material  1510 , such that the third isolation material is aligned to the conducting material  1510 , the first isolation material  1320  and the recesses  1318 . Referring to  FIG. 17 , a finished surface  1700  of the cylindrical element  1300  with the first, second, and third isolation materials encapsulating the conducting material disposed over the cylindrical element is provided. The finished surface  1700  illustrates alternating bands of the third isolation material  1610  and a portion of the second isolation material  1410  that covers the projections on the outer surface of the cylindrical element. The first isolation material  1320 , a portion of the second isolation material covering the recesses and the conducting material are masked below the third isolation material  1610 . Referring to  FIG. 18 , gradient coil assembly  1800  is provided. A protective covering  1810  is disposed over the finished surface  1700  of the cylindrical element  1300 . Referring to  FIG. 19 , gradient coil assembly  1900  is provided. An insulating covering  1910  is disposed over the protective covering  1810  of the cylindrical element  1300 . 
     The gradient coil assembly  1900  was tested in a  3  Tesla field by placing inside a GE Signa 750 MR Magnet. As discussed above, in case of the Z-gradient coil, the Lorenz forces are predominantly radial in direction with some axial component due to the curvature of the static basic magnetic field. The bulk of the isolation material i.e., the first and the second isolation material was applied in the radial direction while the second isolation material provided isolation in the axial direction based on the intensity and the direction of the Lorenz forces. 
     The vibration and noise were measured as illustrated in  FIG. 20 .  FIG. 20  provides a schematic of a gradient coil assembly  2000 . The assembly comprises a cylindrical element  2010 . The cylindrical element has an inner surface  2012  and an outer surface  2014 . The accelerometers  2016 ,  2018 ,  2020  and  2022  are placed on the inner surface  2012 . An axis  2024  is shown at the center of the cylindrical element which represents the patient location in an operating MRI device. A microphone was placed at the axis. The results were compared to a similar coil that was built in the conventional way. A conventionally built coil consists of a similar grooved cylinder with the conductors embedded directly in the grooves without the presence of the isolation materials, and held in place with a layer of low compliance epoxy/fiberglass. In the case of the conventionally build coil, the conductors are in intimate and solid contact with the cylinder. The vibration at resonance and structure-borne noise at the applied frequencies between 0 hertz and 3200 hertz were recorded. 
     Referring to  FIG. 21 , a graph  2100  illustrating the vibration at resonance of the gradient coil assembly  1810  in comparison to a conventional coil is provided. The graph  2100  includes amplitude in acceleration g&#39;s per ampere on the Y-axis  2110  and frequency in hertz on the X-axis  2112 . Curve  2114  represents the vibration at resonance for the gradient coil assembly  1810  and curve  2116  represents the vibration at resonance for the conventional gradient coil assembly. The vibration at resonance was reduced 10 times for curve  2114  when compared to curve  2116  at the applied frequency. 
     Referring to  FIG. 22 , a graph  2200  illustrating the air-borne noise of the gradient coil assembly  1810  in comparison to a conventional coil is provided. The graph  1400  includes sound in Pascal per ampere on the Y-axis  2210  and frequency in hertz on the X-axis  2212 . Curve  2214  represents the sound at resonance for the gradient coil assembly  1810  and curve  2216  represents the sound at resonance for the conventional gradient coil assembly. The air-borne noise was reduced by  20  decibels for curve  2214 , when compared to curve  2216  at the frequencies between 2100 and 2700 Hertz. The sound in the remaining frequencies was found to be produced by other functions of the MRI and was not found related to the vibration of the gradient coils. 
     In accordance with an embodiment of the invention, a gradient coil assembly  1900  is provided. The gradient coil assembly comprises a cylindrical element. The cylindrical element has an inner surface and an outer surface. A plurality of grooves are disposed on the outer surface of the cylindrical element; wherein the grooves comprise alternately disposed projections and recesses. A first isolation material comprising a silicone cord having compliance in a range from about 0.1 millimeters per Newton to 1.0 millimeter per Newton is disposed over the outer surface of the cylindrical element such that the first isolation material is aligned with the recesses of the cylindrical element. A second isolation material comprising a rubber sheet having compliance in a range from about 1 millimeter per Newton to 10 millimeters per Newton is disposed over the projections on the outer surface of the cylindrical element and the first isolation material. A conducting material is disposed over the second isolation material. The conducting material is aligned with the recesses of the cylindrical element. A third isolation material comprising a silicone cord having compliance in a range from about 0.1 millimeters per Newton to 1.0 millimeter per Newton is disposed over the conducting material. The conducting material is disposed between the second isolation material and the third isolation material. 
     While the invention has been described in detail in connection with a number of embodiments, the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.