Abstract: A method is provided for fabricating a gradient coil for an MR imaging system having an open magnet. The method includes forming a structure from thin conductive material such as copper, the structure generally comprising a section of a cylinder and a section of an annulus joined to an edge of the cylinder section as a flange. During a first cutting operation, a plurality of first groove segments are cut through the material, each of the first groove segments lying in one of a plurality of cutting zones selectively positioned around the structure, a strip of material positioned between two adjacent groove segments comprising a coil turn segment. The coil turn segments of a cutting zone are rigidly joined to one another and to a support frame comprising the outer edge of the structure by suitable means. Thereafter, a second cutting operation is performed, whereby a plurality of second groove segments are cut through the material to completely form the gradient coil.

Abstract: An NMR imaging system includes an apparatus for producing a magnetic field gradient within an imaging volume into which the object being imaged is placed. The relatively linear region of the magnetic field gradient is adjusted depending upon the size of the object. The apparatus comprises a source of a gradient signal and four saddle coils positioned in quadrant of a sheet that is wrapped around a cylindrical form. Each saddle coil has a spiral shaped conductive pattern on which are located a primary termination point and a pair of secondary termination points. A switch mechanism connects the four saddle coils in series with the source of a gradient signal, so that voltage from the gradient signal is applied between the primary termination point and a selected secondary termination point of each saddle coil. A control signal applied to the switch mechanism indicates selected secondary termination point and the signal varies according to the size of the object.

Abstract: A local gradient coil adapted for use with stereotaxic devices includes an opening in the coil form positioned to minimize the disruption to the gradient fields and a bearing for moving the form with respect to the stereotaxic frame so that the opening may be limited in area and yet provide essentially unrestricted access to the patient. The windings in the neighborhood of the opening may be diverted by modifying the stream function of the windings in a manner to minimize the effect of the opening on the gradient field.

Abstract: A compact local gradient coil is combined with a local RF coil to provide lower powered, higher strength gradient fields and faster gradient response as is useful in magnetic resonance imaging. Interference between the RF coil and gradient coil is minimized by placement of the gradient coil external to the RF coil and by gradient coils that are axially symmetric and/or have conductors substantially orthogonal to the RF coil conductors. Acoustic noise in these smaller, stronger coils is reduced with ports cut into the coil forms.