Coil system for an mr apparatus and an mr apparatus provided with such a coil system

Abstract

A coil system ( 210 ) for an apparatus operating in conformity with the spin resonance or magnetic resonance (MR) method encloses an examination space ( 217 ) which extends along an axis ( 218 ) and is intended to receive a patient ( 215 ). It includes an inner RF coil ( 219 ), an inner sub-coil ( 213 ') which externally encloses the RF coil ( 219 ) and projects beyond the RF coil ( 219 ) in the axial direction at both sides, and an active shield ( 212 ) which externally encloses the inner sub-coil ( 213 ') and constitutes a gradient coil arrangement in conjunction with the inner sub-coil ( 213 '). For specified gradients, the energy required for the gradient coil arrangement ( 213', 212 ) in such a coil system is reduced in that the volume occupied by the inner sub-coil ( 213 ') is extended in the axial direction by way of regions extending beyond the RF coil ( 219 ) in the direction of the axis ( 218 ). It is an essential aspect that generally three gradient coils are accommodated in the volume enclosed by the gradient coil arrangement ( 213', 212 ). This layered arrangement produces three mutually perpendicular gradient fields as usual. However, it is not necessary to calculate these fields to be such that they extend perpendicularly to one another. All three coil arrangements per se require a smaller energy component in comparison with the normal case.

Description

technical field [0001] The invention relates to the field of magnetic resonance tomography. More specifically, it relates to a coil system as disclosed in the introductory part of claim 1 . It also relates to MR devices comprising this type of coil system. [0002] A coil system of the proposed type is known, for example, from EP-A1-0 304 126 . Background of the invention [0003] Magnetic resonance imaging (MRI), which utilizes the interaction between magnetic fields and atomic nucleus spins to form two-dimensional or three-dimensional images, is being remarkably used for numerous applications in the field of medical diagnosis, because in many Imaging them is superior to other imaging methods in that they do not require ionizing radiation and are generally not invasive. [0004] According to the MR method, the body to be examined is introduced into a strong and homogeneous magnetic field whose direction at the same time defines the axis (usually the z-axis) of the coordi...

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Problems solved by technology

[0009] Furthermore, in order to reduce the energy required by the gradient and RF coils, document EP-A1-0 307981 proposes the use of a combined RF and gradient coil system, which enables a reduction of the free inner diameter of the coil system

[0010] In both cases, the coil system adapted to achieve the reduced energy consumption of gradient coils is relatively sophisticated and complex

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