Abstract: An MR imaging apparatus includes a magnet assembly having two generally opposed pole pieces. Current flowing in driver coils associated with each pole pieces generates a magnetic field in the imaging region. The driver coils include a conductor having beveled edges, the conductor being wound in a spiral fashion. A layer of electrical insulation is located between the conductor windings. A cooling member fabricated from bifilar wound tubing having a generally rectangular cross section is in thermal communication with each driver coil. Coolant flowing through the cooling member removes heat generated in the driver coils.

Abstract: A magnetic resonance imager has a magnetically permeable core and two pole pieces, each pole piece having a face. The pole pieces are arranged on the core such that the pole piece faces are in opposed relationship forming a first gap therebetween. At least one of the pole pieces is comprised of an outer element 23 connected to the core and an inner element 24 connected between the outer element and the first gap. The outer element 23 forms a cup inside which the inner element 24 is disposed. A plurality of screws 11, 12 and 13 are disposed through the outer element 23 and engage the inner element 24 such that a second gap is formed between the inner and outer element. The homogeneity of the magnetic field in the first gap is affected by adjusting the position of the inner element relative to the outer element via screws 11, 12 and 13.

Abstract: A transducer for Overhauser magnetic resonance imaging comprises a cylindrical NMR coil 11 and a two part VHF applicator 12, 13. The applicator and coil are arranged such that the electric field provided by the applicator in use is substantially perpendicular to the coil wires. The VHF applicator is shaped to give a helical field in the region filled by the RF coil, and the RF coil is arranged to be a helix of the opposite handedness. The applicator can comprise a number of similar elements having an electromagnetic resonance mode whose magnetic fled couple to the imaging volume. The elements can be arranged in spirals to form an electric periodic structure.

Abstract: The invention relates to a method for examination of motion of material employing magnetic resonance imaging methods. A magnetic field, which is referred as an auxiliary field is applied over the first area of the object, this auxiliary field is arranged to get smaller as one moves from the first area to the second area, referred as the area to be examined. Partially simultaneously with the auxiliary field a radio frequency pulse, AHP-pulse, is applied on the object, the frequency of the AHP-pulse is the Larmor-frequency corresponding to the strength of the magnetic field in the area to be examined. The length of the AHP-pulse corresponds to the time, which is required for the material to move from the first area to the area to be examined.

Abstract: Current supply for MRI magnet having an output impedance which has been tailored to have the desired shape by using voltage and current feedback. The impedance is small at frequencies which are large with respect to the magnet L/R and the impedance is large at very low frequencies.

Abstract: Two opposite iron core pole pieces of a magnetic resonance medical imager generate a static magnetic field in a patient imaging volume disposed between the pole pieces. Gradient coils are positioned in the face of a pole piece. Thin disc shaped (42, 44) or ring shaped (41) ferromagnetic parts laminated of layers cut favorably from transformer sheet material are attached to the face of the pole piece. Each layer is electrically insulated from adjacent layers and surfaces by enamel or fixing glue. To reduce eddy currents in these layers, narrow, radially oriented slots (43, 45) are cut in these layers before lamination. The slots are oriented in the adjacent layers so as not to coincide resulting in improved conduction of the magnetic flux in the imaging volume during the production of gradient magnetic fields by the gradient coils.

Abstract: In an apparatus and method for magnetic resonance imaging, an imaging field (B.sub.p) and a pre-polarization field (B.sub.p) are generated by means of electromagnetic coils ALC in an air gap between pole pieces of a magnet core. The pole pieces are designed such that, as the current in the coils is increased, the field strength increases only in the central area between pole pieces up to the strength (B.sub.p) of the pre-polarization field. This is due to the saturation of the edge zones of pole pieces that restricts the increase of field strength in the edge zones of the air gap.

Abstract: An SLP pulse is applied to an object to be imaged preceding one or more excitation pulses (a.sup.o or a) of a known magnetic resonance imaging technique. The SLP pulse tilts the nuclear magnetization away from the direction of B.sub.o, locks the magnetization with the rotating magnetic component and returns the magnetization back to the direction of B.sub.o. The known magnetic resonance imaging technique used with the SLP pulse includes applying at least one excitation pulse to generate transverse magnetization in the object. The excitation pulse causes the angle between the nuclear magnetization and B.sub.o to be less than 90.degree..

Abstract: An electron spin resonator (ESR) is used to compensate for temporally varying instabilities in the main magnetic field B.sub.o of a nuclear magnetic resonance imaging apparatus during the derivation of NMR imaging data from an object being imaged. The ESR monitor is placed at a point outside but close to the object such that the ESR monitor is affected by the temporally varying fields. Variances across the ESR caused by gradient fields are compensated for such that the output of the ESR is independent of the strength of the gradient fields. The ESR output is used to reduce the influence of said instabilities on the imaging data.

Abstract: The invention relates to a supporting cushion intended for aligning or positioning the RF-coils of a magnetic resonance imaging apparatus and a patient, which cushion can serve as a part of the RF-coil and which is capable of providing a support for the RF-coil and the patient in accordance with the anatomy of an individual patient. Air is pumped in the cushion for giving the supporting cushion a desired thickness. The cushion is placed against the RF-coil in a manner that, by pumping air therein, said cushion presses the soft and yielding RF-coil against the patient. The cushion can be used e.g. in back and neck coils. The cushion can also be fitted between a patient's supporting rest and a patient in a manner that a section of the patient to be imaged is immobilized for the duration of imaging. For example, the head can be supported or braced this way by fitting the cushion between the head and a head rest.