The principles of the present invention are directed to magnetic resonance imaging systems, and more particularly, but not by way of limitation, to cooling systems for RF coils used on MRI systems.
MR imaging has proven to be a valuable technique for providing information about the internal structure and function of an object under examination. In medical imaging, for example, MR imaging techniques are widely used to provide information on the physiology of human patients.
One limitation, however, on the utility of images and other information generated by MR scanners is the effect of electronic noise. Indeed, signal to noise ratio (SNR) is a key parameter used to evaluate the quality of the information generated by an MR system.
One way to improve the imaging of MRI systems is to increase the signal-to-noise ratio associated with the receiving RF coils. The sources of noise for an RF coil originate either in the coil itself or in the sample being imaged. Typically as the size of a coil increases, the noise in the coil increases in proportion to the length of the coil while the noise from the sample increases as the volume of the sample being imaged. For a relatively small coil, noise is primarily contributed by the coil as opposed to the sample. This is fortunate since sample noise cannot typically be reduced.
Coil noise can be reduced by either using superior materials or by reducing the temperature of the coil. For example, a coil made from a high temperature superconductor (HTS) material typically experiences less noise than a coil made from copper. Similarly cooling the copper in a copper coil will also decrease the noise in the coil. Either approach will increase the signal-to-noise ratio and improve imaging.
Cooling of RF coils has typically been performed only in laboratory settings because the coils are usually immersed in a cold fluid bath such as liquid nitrogen or liquid helium. The cooling fluid typically boils off quickly due to heat transfer, so frequent replacement of the fluid is necessary. Because of the hazards and inconveniences of working with these types of fluids, this type of cooling procedure is not practical for use in MRI machines sited in hospitals and clinics.
A need therefore exists for a new system and method for cooling RF coils in MRI systems, which allows safe and convenient delivery of a cooling fluid to the RF coils. Also needed is a system that will improve the ability of a cooling fluid to cool RF coils by increasing the area of contact between the RF coil and the cooling fluid. Finally, a cooling system is needed that is easily adaptable to RF coils of different sizes and shapes.