Koninklijke Philips Corporation N.v.

U.S. Philips Corporation

Paul Bernard Bunk

Gerardus Bernardus Jozef Mulder

Gerardus Nerius Peeren

Johannes A Overweg

The invention relates to a circuit arrangement for delivering power to coils ( ), which circuit arrangement includes a first and a second coil ( ) a first and a second voltage source ( ) and a first and a second quadrupole switching network ( ), the input ( ) of the first quadrupole switching network ( ) being connected to the first voltage source ( ) and the second voltage source ( ) being connected to at least one terminal ( ) of the second quadrupole switching network ( ). Known switching arrangements have separate voltage sources for each individual power amplifier. In the circuit arrangement in accordance with the invention the two terminals ( ) at the output ( ) of the first quadrupole switching network ( ) are connected, each time via the first and the second coil ( ), respectively, to the two terminals ( ) at the output ( ) of the second quadrupole switching network ( ). It is advantageous that a common voltage source ( ) with a common capacity for delivering power to a plurality of coil systems can thus be provided.

Circuit arrangement for delivering power to coils

Gradient fields G &equals;&part;B /&part;x etc. are generated in an MRI apparatus in order to indicate the position (x, y, z) of an object pixel to be imaged. In a known MRI system the x and y gradient fields are generated by a combination of four gradient coils, two of which are intended to receive the x and y gradient signals whereas the other two coils are intended to receive a mix of the x and y gradient signals in order to enable a simpler structure of the gradient coils and easier impedance matching. According to the invention, apart from the x, y and z gradient signals, other signals are applied to a conversion system ( ) in order to realize the desired gradient fields but also to achieve degrees of freedom that can be used for optimizing system parameters such as heat dissipation or the uniformity of the distribution of power among the gradient amplifiers.

MRI apparatus with gradient control conversion unit

A magnetic measurement apparatus includes a magnet system (1) for generating a steady magnetic field in a measurement space (35), a gradient coil system (3) for generating gradient fields in the measurement space, and a number of gradient amplifiers (9) with input terminals (38) which are connected to means (7) for generating an input signal exhibiting a predetermined variation as a function of time. The output terminals (39) of at least one of the gradient amplifiers (9) are connected to an output circuit which comprises a series connection of a gradient coil (3) and at least one capacitor (55). The output circuit also includes a transformer (41) with a primary winding (43) and a secondary winding (45), the primary winding being connected to the output terminals (39) of the gradient amplifier (9), the secondary winding constituting a series resonant circuit in conjunction with the gradient coil (3) and the capacitor. The current through the gradient coil (3) and the voltage across this coil can thus be substantially higher than the output current and the output voltage of the gradient amplifier (9).

Magnetic resonance apparatus comprising an improved gradient system

In a magnetic resonance apparatus a system of concentric cylinders of superconductive material maintain an effective steady magnetic field in a measured space within the inner cylinder which field is very homogeneous and is, moreover, very constant in time without requiring a large electric power. In a particular embodiment a magnetic field cylinder produces a strong magnetic field, a stabilization cylinder within the magnetic field cylinder ensures a good homogeneity and stabilization of the effective magnetic field, while a screening cylinder provided outside the magnetic field cylinder reduces the external stray field of the system.

Growing community of inventors

Eindhoven, Netherlands

Paul Bernard Bunk