5296813 Magnetic resonance scanner with improved packaging for circuitry within the magnetic field

Abstract

A magnetic resonance imaging apparatus defines an examination region (14) within which main magnets (10) create a uniform magnetic field. Magnetic resonance is excited in dipoles of a subject within the examination region causing the generation of magnetic resonance signals that are received by either a localized coil (C) or whole body radio frequency coils (22). The radio frequency coils are disposed sufficiently adjacent the examination region that the coils are subject to magnetic fields and magnetic field gradients, that any ferrous metals would alter the magnetic field. Magnetic resonance signal processing circuits (54) which are mounted on the coil are free of ferrous materials, such as iron and nickel, to prevent distortion of the uniform magnetic field. The circuit includes an array of unpackaged component dice which are free of ferrous or other packaging. The dice are supported by an insulating substrate (62) to which they are attached by one of whiskers (82), solder bumps (82'), and electrical conductors (102) on a flexible tape (94). In one embodiment, the component dice include a transistor (Q1) and other circuit components for amplifying the received resonance signals. In another embodiment, the component dice include an analog-to-digital converter for digitizing the received magnetic resonance signals at the coil before noise signals received along connecting leads are superimposed onto the resonance signal. In yet another embodiment, an unpackaged microprocessor die is included for performing digital signal processing operations on the digitized magnetic resonance signals at the radio frequency coil.