ADAPTIVE SHIM INSERT COIL SET
Publication Date: 2017-May-24
The IP.com Prior Art Database
Adaptive shim insert coil set is mechanically and electrically separate from the RF Rx coils in MRI systems. The 8-shaped elements are combined to generate various depths B0 penetration, thereby significantly simplifying the technical, commercial and regulatory implementation of B0-on-coil shims in MRI systems.
The present disclosure relates generally to magnetic resonance imaging (MRI), and more particularly to design for shims used in MRI systems.
In high magnetic field of an MRI system, due to magnetic susceptibility of the human body and air-tissue interfaces, the desired main magnetic field B0 is distorted. Such distortions in MR imaging cannot be corrected through MR specific sequences or post-processing. Resistive Shims are built into the MRI system to treat this issue. The B0 shims are classified as a series of scalar spherical harmonics. Current MRI systems have B0 shims up to the 3rd order (in terms of Spherical Harmonics Decomposition). A recent approach to augment RX coils with B0 shimming capability comprised running DC current through each RX element to generate a local B0 field. The DC current is pre-calculated to increase the B0 uniformity. However, utilizing the RX coil conductive traces for B0 shimming affects the intrinsic SNR of the RX coil, and therefore presents an implementation challenge. Further, additional heat dissipated by DC current could exceed pre-existing high heat induced by the TX coils.
Therefore, there exists a need for improving the distortions in MR imaging in the current MRI systems.
BRIEF DESCRIPTION OF DRAWINGS
FIGS. 1A and 1B are a schematic illustration of 8-shaped shim elements in different configurations.
FIG. 2 depicts the magnetic flux of 8-shaped shim elements, for example as shown in FIG. 1.
FIGS. 3A and 3B illustrate the current flows in the 8-shaped eleemnts at the center and the border, respectively.
FIG. 4 is a hand-drawn sketch illustrating the relative arrangements of the RX coil with respect to the adaptive shim insert coil set.
The present disclosure proposes a novel approach in which a separate mesh of vertical figure “8‑shaped” loops with switches are used to increase or decrease the 8-shaped topologies. a separate mesh of vertical 8-shaped saddle coil. The 8-shape along B0 topology assures high purity sectorial sensitivity for correcting B0 field distortion, and is fundamentally orthogonal to traditional loop topologies, providing a topologically decoupled array, as shown in FIGS. 1A and 1B. The shim set is required for reducing B0 field non-uniformity caused by a patient’s magnetic susceptibility. The proposed approach simplifies the implementation of the on-coil shim design, completely separating the shims from RF coil electrically and mechanically. Separating the shims and RF coil elements simplifies the design considerably from an electrical stand point.
Electrically the design comprises independent circuitry connected to multiple DC current sources.
A B0 Shim Insert is placed inside the receive coil, which has an electrically independent circuitry connected to multiple DC current sources. The DC current from such sources are...