Method and apparatus for magnetic resonance imaging and spectroscopy using microstrip transmission line coils

Abstract

Apparatus and method for MRI imaging using a coil constructed of microstrip transmission line (MTL coil) are disclosed. In one method, a target is positioned to be imaged within the field of a main magnetic field of a magnet resonance imaging (MRI) system, a MTL coil is positioned proximate the target, and a MRI image is obtained using the main magnet and the MTL coil. In another embodiment, the MRI coil is used for spectroscopy. MRI imaging and spectroscopy coils are formed using microstrip transmission line. These MTL coils have the advantageous property of good performance while occupying a relatively small space, thus allowing MTL coils to be used inside restricted areas more easily than some other prior art coils. In addition, the MTL coils are relatively simple to construct of inexpensive components and thus relatively inexpensive compared to other designs. Further, the MTL coils of the present invention can be readily formed in a wide variety of coil configurations, and used in a wide variety of ways. Further, while the MTL coils of the present invention work well at high field strengths and frequencies, they also work at low frequencies and in low field strengths as well.

1 . (canceled)  
   
   
       2 . A method of manufacturing a magnetic resonance coil, the method comprising: 
 providing a strip conductor;    providing a ground plane aligned with the strip conductor;    providing a dielectric material between the strip conductor and the ground plane to form a microstrip transmission line (MTL); and    combining the microstrip transmission line with an RF coil such that the microstrip transmission line excites the magnetizations of the target and generates magnetic resonance signals.    
   
   
       3 . The method of  claim 1  further including providing a signal connection for the microstrip transmission line in the RF coil.  
   
   
       4 . The method of  claim 1  further including configuring the microstrip transmission line for exciting the magnetizations of the target at a magnetic field strength greater than 0.2 Tesla.  
   
   
       5 . The method of  claim 1  wherein combining includes configuring the RF coil to provide a uniform field within a volume.  
   
   
       6 . A method for manufacturing a magnetic resonance volume coil, the method comprising: 
 arranging a plurality of microstrip transmission lines about a volume, each microstrip transmission line including a strip conductor, a ground plane, and a dielectric medium between the conductor and the ground plane; and    providing a signal connection to the plurality of microstrip transmission lines, the signal connection configured for imaging a target within the volume coil and for generating magnetic resonance signals.    
   
   
       7 . The method of  claim 6  wherein the signal connection is configured for exciting the magnetizations of the target.  
   
   
       8 . The method of  claim 6  wherein the signal connection is configured for receiving magnetic resonance signals from the volume coil.  
   
   
       9 . The method of  claim 6  wherein arranging includes configuring the plurality of microstrip transmission lines about a partly or fully semi-cylindrical or full-cylindrical volume.  
   
   
       10 . The method of  claim 6  wherein arranging includes configuring a first microstrip transmission line of the plurality of microstrip transmission lines for a first resonant frequency and configuring a second microstrip transmission line of the plurality of microstrip transmission lines for a second resonant frequency wherein the first resonant frequency differs from the second resonant frequency.  
   
   
       11 . The method of  claim 6  further including providing at least one capacitive termination element for at least one microstrip transmission line.  
   
   
       12 . The method of  claim 11  wherein providing the at least one capacitive termination element includes coupling the element to a first end of the microstrip transmission line.  
   
   
       13 . The method of  claim 11  wherein providing the at least one capacitive termination element includes coupling a first element to a first end of the microstrip transmission line and a second element to a second end of the microstrip transmission line.  
   
   
       14 . The method of  claim 11  wherein providing the at least one capacitive termination element includes providing a variable capacitance.  
   
   
       15 . The method of  claim 6  further including forming a microstrip transmission line using a substantially planar and non-linear shaped conductor.  
   
   
       16 . The method of  claim 6  further including forming a microstrip transmission line in a shape selected from the group of an S-shape, a square, a triangle, and a circular shape.  
   
   
       17 . The method of  claim 6  further including forming a microstrip transmission line in a shape with at least a fraction of one turn.  
   
   
       18 . The method of  claim 6  further including forming a microstrip transmission line in a shape with at least one turn.  
   
   
       19 . The method of  claim 6  wherein the signal connection is configured for coupling to a capacitive impedance matching network.  
   
   
       20 . The method of  claim 6  wherein arranging includes chamfering corners on the conductor to reduce radiation loss.  
   
   
       21 . The method of  claim 6  further including connecting at least one portion of a ground plane relative to the other portions of the ground plane.  
   
   
       22 . The method of  claim 21  wherein connecting the at least one portion of the ground plane relative to the other portions of the ground plane includes connecting a first portion of a bisected ground plane relative to a second portion of the bisected ground plane.  
   
   
       23 . The method of  claim 21  further including coupling at least one pin diode to at least one portion of the ground plane.  
   
   
       24 . The method of  claim 21  further including positioning a pin diode in a gap between at least two portions of the ground plane such that the pin diode is applied to the at least two portions of the ground plane.