Abstract:
A local breast coil is designed to be tightly coupled to the natural shape of the pendant breast to provide high SNR for diagnostic MR imaging applications, while still providing access for interventional procedures through openings in the coil. In accordance with one configuration, the coil has a symmetrical design, such that the coil can be rotated about the breast to position an opening in the coil proximate to a desired portion of the breast without incurring registration or other alignment or artifact errors due to inhomogeneous B 1  excitation. Furthermore, the coil is designed to facilitate medial and lateral imaging of the breast. The coil is combined with a patient support system that facilitates rotation of the coil and interchangeability of the coil to match the configuration of the coil to the position of the breast being imaged.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on, incorporates herein by reference, and claims the benefit of provisional application Ser. No. 60/915,842, filed May 3, 2007, and entitled “INTERVENTIONAL DEVICE WITH SOLENOID RF COIL.” 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
     This invention was made with government support under Grant No. NIH 5 P30 CA014520-33. The United States Government has certain rights in this invention. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to a system and method for imaging a breast using a magnetic resonance imaging (MRI) system. More particularly, a local breast coil is provided that enables medial and lateral imaging of the breast and provides ready access to the breast throughout the imaging process. 
     BACKGROUND OF THE INVENTION 
     Breast cancer is a fatal disease caused by the growth of cancerous cells within breast tissue. These cancerous cells form a lump, cyst, lesion, and the like that can grow at an alarming rate and, if left undetected, can even spread beyond the breast. Unfortunately, even with an increasing number of breast cancer cases reported each year, many women are still reluctant to go in for scheduled examinations or to receive treatment for non-cancerous lumps. A major reason for this reluctance is the physical and psychological discomfort that are experienced during examinations and treatments. 
     For example, screening mammography has been one of the primary diagnosis tools for breast cancer detection for over 30 years. However, many women find the compression of the breast required during a mammography procedure to be extremely uncomfortable. 
     Though more costly than x-ray mammography, MRI is more sensitive and can be used to detect lesions at an earlier stage than traditional mammography. Furthermore, MRI of the breast does not require compression of the breast like mammography. 
     In basic principle, when a substance such as human tissue is subjected to a uniform magnetic field (polarizing field B 0 ) applied along an axis, typically designated the z axis of a Cartesian coordinate system, the individual magnetic moments of the spins in the tissue attempt to align with this polarizing field, but precess about it in random order at their characteristic Larmor frequency. If the substance, or tissue, is subjected to a magnetic field (excitation field B 1 ) that is in a perpendicular plane to the axis, typically designated the x-y plane, and that is near the Larmor frequency, the net aligned moment, Mz, may be rotated, or “tipped”, into the that x-y plane to produce a net transverse magnetic moment M t . A nuclear magnetic resonance (NMR) signal is emitted by the excited spins after the excitation signal B 1  is terminated. This NMR signal may be received and processed to form an image or produce a spectrum. 
     When utilizing these signals to produce images, magnetic field gradients (G x , G y , and G z ) are employed. Typically, the region to be imaged is scanned by a sequence of measurement cycles in which these gradients vary according to the particular localization method being used. The resulting set of received NMR signals are digitized and processed to reconstruct the image using one of many well known reconstruction techniques. 
     Radio frequency antennas, or coils, are used to produce the excitation field B 1  and other RF magnetic fields in the subject being examined. Such coils are also used to receive the very weak NMR signals that are produced in the subject. Such coils may be so-called “whole body” coils that are large enough to produce a uniform magnetic field for a human subject or, they can be much smaller “local” coils that are designed for specific clinical applications such as head imaging, knee imaging, wrist imaging, breast imaging, and the like. 
     In the case of breast MRI, a local breast coil is typically employed. Typically, to arrange the breast in the coil, the woman is arranged in the prone position and the breast positioned in a local coil arranged beneath a patient bed on which the woman is laying. Thus, the breast is not compressed. 
     Two types of local coils are typically utilized in breast imaging and each coil design has an associated number of advantages and drawbacks. One coil type is often referred to as an “open” coil. These coils have coil elements that are arranged about an area where the breast is arranged but are disposed at a distance from the actual breast. These open coils provide ready access to the breast when it is arranged in the coil to facilitate stereotactic procedures, allow the placement of fiducial markers, and the like. Unfortunately, the distance between the exterior of the breast and the location of the coil reduces the signal-to-noise ratio (SNR). That is, the further the coil is decoupled from the breast, the lower the SNR 
     To improve SNR, some traditional local breast coils utilize a “saddle” design that is built into a frame that extends below the patient bed. In this regard, the coil is arranged directly about the breast. While this configuration increases SNR, these traditional saddle coils present a number of drawbacks. Specifically, the amount of access to the breast when arranged in the coil is significantly restricted. That is, saddle coils can only be rotated about the principal magnetic field (z) axis without seriously compromising SNR. For biopsy, rotation about z axis is done to improve access and visualization of the target region, but this rotation is highly constrained and limited to only a few degrees of rotation. 
     Therefore, it would be desirable to have a system and method for imaging a breast using an MRI system that permits ready access to any desired portion of the breast when the breast is positioned in the local coil while still providing a high SNR and not requiring an onerous registration or orientation process. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the aforementioned drawbacks by providing a local breast coil that is designed to be tightly coupled to the breast to provide high SNR, while still providing access to the breast through openings in the coil. The coil has a symmetrical design, such that the coil is well suited to transmit/receive rather than receive only configurations and thus can readily be used for bilateral imaging of the breast with minimized cross-talk and improved and reduced noise. In accordance with one configuration, the coil can be rotated about the breast to position an opening in the coil proximate to a desired portion of the breast without incurring registration or other alignment or artifact errors due to inhomogeneous B1 excitation. Furthermore, the coil is designed to facilitate medial and lateral imaging of the breast with good sensitivity in regions proximal to the chest wall. 
     In accordance with one aspect of the invention, an RF coil for use with a magnetic resonance imaging (MRI) system is disclosed that includes a frame and a conductor coupled to the frame and extending about the frame to form a solenoid shape. The frame includes an opening at a first end having a first cross-sectional area configured to receive a body part to be imaged using the MRI system and a frame body extending along a central axis of the frame from the first end toward a second end having a second cross-sectional area smaller than the first cross sectional area. The frame also includes a plurality of openings formed in the frame body to provide access from an exterior of the frame body to the body part arranged in an interior of the frame. The conductor includes a first loop arranged proximate to the first end of the frame and extending in a first plane substantially transverse to the central axis of the frame and a second loop arranged proximate to the second end of the frame and extending in a second plane substantially parallel to the first plane and transverse to the central axis of the frame. The conductor also includes at least one leg connecting the first loop and the second loop. Accordingly, at least a portion of the plurality of openings formed in the frame body is accessible between the first loop and the second loop. 
     In accordance with another aspect of the invention, a patient support system configured to support a patient during an MRI process using an MRI system is disclosed that includes a bed having a surface configured to receive the patient to support the patient during the MRI process and an RF coil as described above. 
     Various other features of the present invention will be made apparent from the following detailed description and the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of an MRI system that employs the present invention; 
         FIG. 2  is a block diagram of an RF system that forms part of the MRI system of  FIG. 1 ; 
         FIG. 3  is a perspective view of a local breast coil in accordance with the present invention and utilized with the systems of  FIGS. 1 and 2 ; 
         FIG. 4  is a schematic diagram of a conductor arrangement of the coil of  FIG. 3 ; 
         FIG. 5  is a side-elevational view of a conductor arrangement of the coil of  FIGS. 3 and 4 ; 
         FIG. 6  is a side-elevational view of a patient table in accordance with the present invention that is designed to interchangeably receive local breast coils such as illustrated in  FIG. 3 ; and 
         FIG. 7  is a perspective view of another conductor arrangement in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring particularly to  FIG. 1 , the present invention is employed with an MRI system. The MRI system includes a workstation  10  having a display  12  and a keyboard  14 . The workstation  10  includes a processor  16  that is a commercially available programmable machine running a commercially available operating system. The workstation  10  provides the operator interface that enables scan prescriptions to be entered into the MRI system. The workstation  10  is coupled to, for example, four servers including a pulse sequence server  18 , a data acquisition server  20 , a data processing server  22 , and a data store server  23 . The workstation  10  and each server  18 ,  20 ,  22  and  23  are connected to communicate with each other. 
     The pulse sequence server  18  functions in response to instructions downloaded from the workstation  10  to operate a gradient system  24  and an RF system  26 . Gradient waveforms necessary to perform the prescribed scan are produced and applied to the gradient system  24  that excites gradient coils in an assembly  28  to produce the magnetic field gradients G x , G y  and G z  used for position encoding MR signals. The gradient coil assembly  28  forms part of a magnet assembly  30  that includes a polarizing magnet  32  and a whole-body RF coil  34  or, in accordance with the present invention, a local RF coil  35 . 
     In operation, RF excitation waveforms are applied to the RF coil  34  by the RF system  26  to perform the prescribed magnetic resonance pulse sequence. Responsive MR signals are detected by, as will be described, a local RF coil  35 . The MR signals are received and provided to the RF system  26  where, as will be described with respect to  FIG. 2 , the signals are amplified, demodulated, filtered, and digitized under direction of commands produced by the pulse sequence server  18 . 
     The RF system  26  includes an RF transmitter for producing a wide variety of RF pulses used in MR pulse sequences. The RF transmitter is responsive to the scan prescription and direction from the pulse sequence server  18  to produce RF pulses of the desired frequency, phase and pulse amplitude waveform. The generated RF pulses may be applied to the whole body RF coil  34  or to one or more local coils or coil arrays  35 . As will be described, it is contemplated that the local coil  35  in accordance with the present invention may be used as both a receive and a transmit coil. 
     The RF system  26  also includes one or more RF receiver channels. Each RF receiver channel includes an RF amplifier that amplifies the MR signal received by the coil to which it is connected and a detector that detects and digitizes the I and Q quadrature components of the received MR signal. The magnitude of the received MR signal may thus be determined at any sampled point by the square root of the sum of the squares of the I and Q components:
 
 M =√{square root over ( I   2   +Q   2 )},
 
and the phase of the received MR signal may also be determined:
 
φ=tan −1    Q/I.  
 
     The pulse sequence server  18  also optionally receives patient data from a physiological acquisition controller  36 . The controller  36  receives signals from a number of different sensors connected to the patient, such as ECG signals from electrodes or respiratory signals from a bellows. Such signals are typically used by the pulse sequence server  18  to synchronize, or “gate”, the performance of the scan with the subject&#39;s respiration or heart beat. 
     The pulse sequence server  18  also connects to a scan room interface circuit  38  that receives signals from various sensors associated with the condition of the patient and the magnet system. It is also through the scan room interface circuit  38  that a patient positioning system  40  receives commands to move the patient to desired positions during the scan. 
     The digitized MR signal samples produced by the RF system  26  are received by the data acquisition server  20 . The data acquisition server  20  operates in response to instructions downloaded from the workstation  10  to receive the real-time MR data and provide buffer storage such that no data is lost by data overrun. In some scans, the data acquisition server  20  does little more than pass the acquired MR data to the data processor server  22 . However, in scans that require information derived from acquired MR data to control the further performance of the scan, the data acquisition server  20  is programmed to produce such information and convey it to the pulse sequence server  18 . For example, during pre-scans MR data is acquired and used to calibrate the pulse sequence performed by the pulse sequence server  18 . Also, navigator signals may be acquired during a scan and used to adjust RF or gradient system operating parameters or to control the view order in which k-space is sampled. And, the data acquisition server  20  may be employed to process MR signals used to detect the arrival of contrast agent in an MRA scan. In all these examples the data acquisition server  20  acquires MR data and processes it in real-time to produce information that is used to control the scan. 
     The data processing server  22  receives MR data from the data acquisition server  20  and processes it in accordance with instructions downloaded from the workstation  10 . Such processing may include, for example: Fourier transformation of raw k-space MR data to produce two or three-dimensional images; the application of filters to a reconstructed image; the performance of a backprojection image reconstruction of acquired MR data; the calculation of functional MR images; the calculation of motion or flow images, etc. 
     Images reconstructed by the data processing server  22  are conveyed back to the workstation  10  where they are stored. Real-time images are stored in a data base memory cache (not shown) from which they may be output to operator display  12  or a display that is located near the magnet assembly  30  for use by attending physicians. Batch mode images or selected real time images are stored in a host database on disc storage  44 . When such images have been reconstructed and transferred to storage, the data processing server  22  notifies the data store server  23  on the workstation  10 . The workstation  10  may be used by an operator to archive the images, produce films, or send the images via a network to other facilities. 
     As shown in  FIG. 1 , the RF system  26  may be connected to the whole body RF coil  34  or local coil  35 , or as shown in  FIG. 2 , a transmitter section of the RF system  26  may connect to one RF coil  152 A and its receiver section may connect to a separate RF receive coil  152 B. Often, the transmitter section is connected to the whole body RF coil  34  and each receiver section is connected to separate local coils  35 ,  152 B. In addition, as will be described, it is contemplated that the transmit RF coil  152 A and the receive RF coil  152 B may be the same local coil  35  described above with respect to  FIG. 1 . 
     Referring particularly to  FIG. 2 , the RF system  26  includes a transmitter that produces a prescribed RF excitation field. The base, or carrier, frequency of this RF excitation field is produced under control of a frequency synthesizer  200  that receives a set of digital signals from the pulse sequence server  18 . These digital signals indicate the frequency and phase of the RF carrier signal produced at an output  201 . The RF carrier is applied to a modulator and up converter  202  where its amplitude is modulated in response to a signal R(t) also received from the pulse sequence server  18 . The signal R(t) defines the envelope of the RF excitation pulse to be produced and is produced by sequentially reading out a series of stored digital values. These stored digital values may, be changed to enable any desired RF pulse envelope to be produced. 
     The magnitude of the RF excitation pulse produced at output  205  is attenuated by an exciter attenuator circuit  206  that receives a digital command from the pulse sequence server  18 . The attenuated RF excitation pulses are applied to the power amplifier  151  that drives the transmit RF coil  152 A. 
     Referring still to  FIG. 2 , the signal produced by the subject is picked up by the receive RF coil  152 B, which, again, may be the same physical coil as the transmit RF coil  152 A. The received MR signals are applied through a preamplifier  153  to the input of a receiver attenuator  207 . The receiver attenuator  207  further amplifies the signal by an amount determined by a digital attenuation signal received from the pulse sequence server  18 . The received signal is at or around the Larmor frequency, and this high frequency signal is down converted in a two step process by a down converter  208  that first mixes the MR signal with the carrier signal on line  201  and then mixes the resulting difference signal with a reference signal on line  204 . The down converted MR signal is applied to the input of an analog-to-digital (A/D) converter  209  that samples and digitizes the analog signal and applies it to a digital detector and signal processor  210  that produces 16-bit in-phase (I) values and 16-bit quadrature (Q) values corresponding to the received signal. The resulting stream of digitized I and Q values of the received signal are output to the data acquisition server  20 . The reference signal as well as the sampling signal applied to the A/D converter  209  are produced by a reference frequency generator  203 . 
     Referring now to  FIGS. 3, 4, and 5 , a local breast coil  300  having a solenoid shape in accordance with the present invention includes a first turn or loop  302 , a second turn or loop  304 , and third turn or loop  306 . It is contemplated that the RF coil  300  may include any other number of loops. That is, the RF coil  300  could have any number of windings and the specific number of windings can be optimized depending on the imaging and intervention requirements. 
     The first loop  302 , second loop  304 , and third loop  306  are mounted to a cup-shaped frame  308 . It is noted that the first loop  302  is mounted proximate a first end  307  of the frame  308 . Accordingly, the RF coil  300  is designed to provide substantial sensitivity extending into the chest wall due to its close proximity to the chest wall when a patient is arranged in the prone position illustrated in  FIG. 1   
     As used herein, the term “mount” can include join, unite, connect, associate, insert, hang, hold, affix, attach, fasten, bind, paste, secure, bolt, nail, glue, screw, rivet, solder, weld, and other like terms. The loops of the RF coil  300  may be made of copper or any other conducting material known to those of skill in the art. In accordance with one configuration, the loops of the RF coil  300  can be in the form of conducting strips or ribbons, such as thin strips of a conducting material. Alternatively, the loops can be in the form of conducting wires or any other conducting segments. 
     As used herein, a ‘cup-shaped’ frame can refer to any frame with a concave inner surface adapted to receive a body part such as a breast. The inner surface of the cup-shaped frame can be circular, elliptical, cylindrical, or any other cup-like shape adapted to receive the body part. Alternatively, the cup-shaped frame can refer to a plurality of frames arranged to form a concave inner surface for receiving a breast. The cup-shaped frame can also come in different sizes to accommodate patients of different sizes. 
     As illustrated, The RF coil  300  is mounted to cup-shaped frame  308  such that the each loop  302 ,  304 ,  306  lie in respective planes that are substantially parallel to each other and a plane formed by a base  310  the RF coil  300  arranged at a second end  311  opposite the first end  307  of the frame  308 . Furthermore, as will be described, the respective planes of each loop  302 ,  304 ,  306  extend transverse or perpendicular to a central axis  328  extending through the frame  308 . 
     While it is contemplated that the conductors  302 ,  304 ,  306  may be mounted in other orientations relative to cup-shaped frame  308 , it is noted that the orientations illustrated in  FIGS. 3-5  are desirable due to the high degree of regularity and homogeneity in the magnetic field produced by the coil  300 . Nonetheless, as will be described with respect to  FIG. 7 , a conductor may be arranged in a saddle configuration. Furthermore, it is contemplated that a loop may include a conducting strip with two faces and two sides. The conducting strip can be mounted horizontally such that a face of the conducting strip lies in a plane that is substantially parallel to the base  310 . Alternatively, the conducting strip can be mounted vertically such that a side of the conducting strip lies in the plane that is substantially parallel to the base  310 . In yet another embodiment, the loop may be implemented with a copper wire or cylindrical copper tube. In one configuration, the cup-shaped frame  308  can include one or more ledges adapted to receive the loops of the RF coil  300 . 
     Referring back to  FIGS. 3, 4, and 5 , the loops  302 ,  304 ,  306  of the RF coil  300  are mounted as spaced concentric shapes that substantially conform to an outer surface of cup-shaped frame  308 . The outer surface of the cup-shaped frame  308  can have a circular or ovular shape such that the loops  302 ,  304 ,  306  of the RF coil  300  form concentric circles that are designed to be coupled tightly to the breast. Alternatively, the outer surface of the cup-shaped frame  308  can take other shapes including various tapers that are linear or non-linear and the loops  302 ,  304 ,  306  of the solenoid RF coil can be shaped accordingly. In an alternative configuration, the shape of the loops  302 ,  304 ,  306  may be different from that of the outer surface of the cup-shaped frame  308 . For example, the outer surface of the cup-shaped frame  308  may be square, and the loops  302 ,  304 ,  306  of the RF coil  300  may be circular. Further still, the loops  302 ,  304 ,  306  of the RF coil  300  may be mounted to the cup-shaped frame  308  in other configurations. For example, the loops may be mounted such that one or more of the loops  302 ,  304 ,  306  lie in planes that are not substantially parallel to the base  310 . Also, the loops may be mounted to an inner surface of the cup-shaped frame  308 . 
     In one configuration, spacing between the loops of the RF coil  300  can be equidistant such that a distance between the first loop  302  and second loop  304  are the same as a distance between the second loop  304  and third loop  306 . Alternatively, the spacing between loops  302 ,  304 ,  306  may be unequal. In an exemplary configuration, consecutive loops of the solenoid RF coil  300  can be connected by respective conducting coil legs  312 ,  314  such that the RF coil  300  is continuous along its length. Thus, the loops  302 ,  304 ,  306  are connected electrically in series to form a solenoid. 
     In particular a single continuous conductor, for example, a copper conductor forms the loops  302 ,  304 ,  306  and legs  312 ,  324  and extends along the surface of the cup-shaped frame  308 . The specific shape, size, and dimensions of the cup-shaped frame  308  may vary such that a number of RF coils  300  may be selected from to adjust the size parameters to optimally accommodate a range of breast sizes. To this end, although three loops  302 ,  304 ,  306  are illustrated, it is contemplated that more loops of the conductor may be desirable depending on the size of the breast to be imaged and the application being performed. 
     The solenoidal geometry of this conductive strip provides homogenous B1 excitation and reception fields, while the tapering of the solenoid near the nipple of the breast allows more efficient coupling to the breast tissue for improved signal to noise (SNR). This tapering of the coil diameter or cross-section is best illustrated in  FIGS. 4 and 5 , which show that the cross-sectional area inside each subsequent loop extending further from the first end  307  of the frame  308  toward a second end  311  of the frame  308  decreases. The following table provides evidence of the SNR performance of the above-described coil using a conventional T1-weighted gradient recalled echo acquisition commonly used for diagnostic breast MRI in comparison to other, local receive coils of conventional design. 
     
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Region 
                 Solenoid Coil 
                 7 Channel Coil 
                 4 Channel Coil 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Upper 
                 9.6 
                 8.9 
                 11.9 
               
               
                   
                 Middle 
                 21.9 
                 10.0 
                 13.0 
               
               
                   
                 Lower 
                 54.1 
                 10.4 
                 16.0 
               
               
                   
                   
               
             
          
         
       
     
     Moreover, the orientation of the breast anatomy for the typically prone patient position with respect to the principal magnetic field is preferable for this design because the primary axis of excitation field is transverse to the principal field, and thus is parallel to the axis of the solenoid. This arrangement provides good isolation between the two coils and allows the RF coil  300  to be designed as a transmit/receive coil or as a receive-only coil. 
     Referring to  FIG. 4 , a pair of solenoid RF coils  300  is shown. Each RF coil  300  includes a tuning module  316 . In one configuration, the tuning module  316  can be in electrical communication with solenoid RF coil  300  and located proximate to a base  310  of the RF coil  300 . The tuning module  316  may include a matching capacitor and a tuning capacitor such that solenoid RF coil  300  can be matched and tuned as known to those of skill in the art. Alternatively, the tuning module  316  can include any other components capable of matching and/or tuning solenoid RF coil  300 . 
     A resistive load  317  with a switch  318  is provided to allow switching between unilateral and bilateral operation if bilateral operation is not needed. Furthermore, a quad hybrid circuit  319  allows excitation-reception of each coil with orthogonal phase between them for separation of the received signals and improved isolation beyond that already provided by the geometrical advantages described above. 
     A coaxial cable  320  can be used to connect the solenoid RF coil  300  with the MRI system, such as described with respect to  FIG. 1 . The coaxial cable may include a transmit line  321  and a receive line  322 . Accordingly, in operation, the RF coil  300  can be used with the MRI system to direct an RF pulse toward a body part that is placed in cup-shaped frame  308 . Furthermore, the RF coil  300  may only be used to receive the resulting NMR signals. 
     During this process or at any time when the breast is located within the RF coil  300 , it is contemplated that the breast may be accessed via a lower window  324  or an upper window  326  of cup-shaped frame  308 . These windows  324 ,  326  provide access for a biopsy/therapy probe (not shown) to access the breast tissue. The lower window  324  is positioned between the first loop  302  and second loop  306 , and the upper window  326  is positioned between the second loop  304  and third loop  306 . In configurations in which the RF coil  200  includes more loops, one or more windows may be provided between each pair of consecutive loops. The lower window  324  and/or upper window  326  can be apertures of any size or shape that allow unobstructed access to the breast or other body part arranged in the RF coil  300 . Alternatively, either or both of the windows  324 ,  326  may include a plurality of apertures through which a medical device can be inserted. 
     Additionally, it is contemplated that more restricted windows may be provided in the cup-shaped frame  308 . Specifically, referring to  FIG. 5 , it is contemplated that multiple portals  327  may be formed in the cup-shaped frame  308  to provide more restricted access to specific portions of the breast. 
     The symmetrical nature of the RF coil  300  provides a plurality of degrees of freedom such that unobstructed three-dimensional access to the breast through the RF coil  300  is provided. A first degree of freedom allows the RF coil  300  to be rotated bi-directionally in a complete circle. Specifically, a rotational axis  328  is created that is substantially perpendicular to the base  310  and that extends through a center of the cup-shaped frame  308 . 
     Referring to  FIG. 6 , to facilitate such rotation, it is contemplated that the RF coil  300  may be coupled with a patient table  330  designed to receive the RF coil  300 . Specifically, the patient table is designed to receive a patient in the prone position illustrated in  FIG. 1 . To this end, the patient table  300  includes a recess  332  configured to receive the RF coil  300 . The recess is formed by providing a passage through an upper portion  334  of the patient table  330 , such that the RF coil  300  may extend down through the upper portion  334  of the patient table  330  toward a lower portion  336  of the patient table  330 . The upper portion  334  of the patient table  330  is separated from the lower portion  336  of the patient table  330  by a plurality of columns  338 . This configuration not only provides a space  340  for the RF coil  300  to extend below the patient, but also provides a space within which the RF coil  300  can be accessed when in use. Accordingly, not only can the RF coil  300  be accessed during use, but the windows  324 ,  326  formed in the RF coil  300  provide a means of accessing the breast arranged within the RF coil during use. 
     It is also contemplated that the RF coil  300  may be removably coupled with the patient table  300  so that the size, dimension, and configuration of the RF coil  300  may be specifically matched to the patient. That is, the RF coil  300  is designed to engage the patient table through a mounting system that allows the RF coil  300  to be removed and replaced with relative ease. For example, the RF coil  300  may be secured to the patient bed  330  through the base  310  engaging the lower portion of the patient table  336 . Additionally or alternatively, the RF coil  300  may include a mounting flange  342  that engages the upper portion  334  of the patient table  330 . 
     As stated above, the RF coil  300  can be rotated about the rotational axis  328 . To this end, it is contemplated that the RF coil  300  may be manually rotated to provide access to the desired portion of the breast through one or more of the windows  324 ,  326 . Furthermore, rotation can be implemented through a rotation controller (not shown) that controls the relative position of the RF coil  300  with respect to the patient bed  330 . 
     It should, however, be noted that the RF coil  300  described above allows a high degree of flexibility regarding the design of the patient support so as to optimally access the breast for diagnosis or therapy. In addition, the coils can be mounted on different sized holders so as to accommodate a range of breast sizes. Furthermore, by removing the close integration of the above-described electronics associated with the RF coil  300  from the patient table  330  support, it is possible to optimize both to improve access in the chest wall and medial regions without limiting the lateral access of conventional MR biopsy devices. 
     The above-described system provides a local breast coil  300  that is optimized for providing homogeneous excite/receive and is therefore well suited to bilateral imaging of breast tissue with minimal cross-talk and improved SNR. This underscores the general applicability of this design for both diagnostic and interventional applications. The design is based on a solenoid geometry that is symmetrical and tailored to conform to the breast shape for more efficient coupling to the tissue and improved SNR. To this end, image quality is not affected by rotating the coil. This is an advantageous feature because it allows the coil to be rotated to optimize the location for needle/probe or insertion for interventional procedures without interfering with the imaging process. Moreover, the combination of two such coils, one positioned on each breast, allows bilateral imaging with very efficient isolation of the signals from the right and left breast bilaterally. This provides a significant advantage for dynamic contrast-enhanced applications where bilateral coverage is desired with high spatial and temporal resolution imaging within a single injection of gadolinium contrast agent. Thus, the design is optimized for any region of the breast tissue intrinsically, well suited to transmit/receive and thus to bilateral imaging of the breast For diagnostic imaging, the design is superior to the receive only saddle designs from the point of view of symmetry, SNR, and access. 
     Referring now to  FIG. 7 , another tapered local breast  400  coil design is provided. In this configuration, a strip of conductor  402  backed by a ground plane extends longitudinally about a cup-shaped frame  404 . The strip conductor  402  forms one RF coil having a region of sensitivity along the x-axis. A second looped conductor  406  is placed around the circumference of a rim of the cup-shaped frame  404 . The magnetic field due to looped conductor  406  extends perpendicular to the x-z plane and, hence, is orthogonal to the field due to the conductor strip  402 . This arrangement ensures good isolation between the two conductors and may, hence, be designed as a transmit/receive coil or as a receive-only coil. However, this design does not have the rotational symmetry advantageously provided by the RF coil  300  described above. That is, unlike the coil  300  described above with respect to  FIGS. 3-6 , the coil design illustrated in  FIG. 7  magnetic field of the strip conductor  400  won&#39;t remain perpendicular to the z-axis as the coil  400  is rotated. 
     The present invention has been described in terms of the various embodiments, and it should be appreciated that many equivalents, alternatives, variations, and modifications, aside from those expressly stated, are possible and within the scope of the invention. Therefore, the invention should not be limited to a particular described embodiment.