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RADIO FREQUENCY ARRAY COIL SYSTEM AND METHOD FOR MAGNETIC RESONANCE PARALLEL IMAGING

IP.com Disclosure Number: IPCOM000126285D
Publication Date: 2005-Jul-12
Document File: 45 page(s) / 2M

Publishing Venue

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Abstract

The primary design of the RF array coil system 1 of the present invention provides twelve channels/coil elements to image the head, neck and torso regions of a human body. The imaging evaluations for the RF array coil system of present invention have proven that it outperform dedicated regional RF coils, for examples, a quadrature head coil and an 8-channel CTL coil, for head and neck/c-spine imaging.

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RADIO FREQUENCY ARRAY COIL SYSTEM AND METHOD FOR MAGNETIC RESONANCE PARALLEL IMAGING

FIELD OF THE INVENTION

This invention relates generally, to magnetic resonance imaging, and more particularly to, a radio frequency array coil system in magnetic resonance parallel imaging.

BACKGROUND OF THE INVENTION

Magnetic Resonance Imaging (MRI) utilizes hydrogen nuclear spins of the water molecules in the human body, which are polarized by a strong, uniform, static magnetic field of the magnet (named B0 - the main magnetic field in MRI physics). The magnetically polarized nuclear spins generate magnetic moments in the human body. The magnetic moments point in the direction of the main magnetic field in a steady state, and produce no useful information if they are not disturbed by any excitation.

The generation of Nuclear Magnetic Resonance (NMR) signal for MRI data acquisition is accomplished by exciting the magnetic moments with a uniform Radio-Frequency (RF) magnetic field (named B1 field or the excitation field). The B1 field is produced in the imaging region of interest by an RF transmit coil which is driven by a computer-controlled RF transmitter with a power amplifier. During excitation, the nuclear spin system absorbs magnetic energy, and it's magnetic moments precess around the direction of the main magnetic field. After excitation, the precessing magnetic moments will go through a process of Free Induction Decay (FID), releasing their absorbed energy and returning to the steady state. During free induction decay, NMR signals are detected by the use of a receive RF coil, which is placed in the vicinity of the excited volume of the human body. The NMR signal is the secondary electrical voltage (or current) in the receive RF coil that has been induced by the precessing magnetic moments of the human tissue. The receive RF coil can be either the transmit coil itself, or an independent receive-only RF coil. The NMR signal is used for producing MR images by using additional pulsed magnetic gradient fields, which are generated by gradient coils integrated inside the main magnet system. The gradient fields are used to spatially encode the signals and selectively excite a specific volume of the

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human body. There are usually three sets of gradient coils in a standard MRI system, which generate magnetic fields in the same direction of the main magnetic field, varying linearly in the imaging volume.

In MRI, it is desirable for the excitation and reception to be spatially uniform in the imaging volume for better image uniformity. In a standard MRI system, the best excitation field homogeneity is usually obtained by using a "whole-body" volume RF coil for transmission. The "whole-body" transmit coil is the largest RF coil in the system. A large coil, however, produces lower signal-to-noise ratio (SNR or S/N) if it is also used for reception, mainly because of its greater distance from the signal-generating tissues being imaged....