Abstract: An array of plural magnetic resonance imaging (MRI) RF coils is provided having different and overlapping fields of view. Controllable switches are connected with each individual coil of the array and are capable of selectively conditioning any one of the coils for individual usage in an MRI procedure. Either mechanical or electrical (e.g., PIN diode) switching control may be utilized. Preferably, controllable electrical switches are located at points having approximately zero RF potential. Distributed capacitance is also preferably employed for reducing terminal inductance, preventing the establishment of spurious magnetic fields and facilitating the use of electrical switching diodes and/or varactor capacitance elements. Such distributed capacitances are also dimensioned so as to cause the terminal inductance of each coil to be within the tuning/matching range of a common tuning/matching RF circuit.

Abstract: A quadrature detection magnetic resonance imaging (MRI) RF coil is constructed from non-overlapping axially-extending conductors arrayed about the circumference of a cylinder in four circumferentially spaced-apart groupings. Axially-extending annular gaps in the fingers (e.g, at their mid-points) are bridged across by RF coupling capacitors. The outer ends of the fingers are also coupled by annular conductors having one or more conductive gaps bridged by coupling capacitance. First and second quadrature detection RF input/output ports are coupled to at least one respective finger element in each of two adjacent groups of elements.

Abstract: A pair of co-located RF surface coils extend axially and part-circumferentially about a volume to be imaged. Because surface coils are employed, the RF field distribution will be non-symmetric, non-homogeneous and non-uniform within the volume. Nevertheless, if the two coils are rotationally offset by the proper amount (and possibly including capactive isolation coupling therebetween), the coils produce a pair of RF signals to/from the volume which are in quadrature phase thus providing signal-to-noise ratio improvements due to: (a) the fact that quadrature detection techniques are employed and (b) the fact that only a portion of the cross-sectional volume is effectively addressed by the surface coils (i.e., due to their non-symmetric, non-homogeneous and non-uniform field distribution).

Abstract: Shaped RF field distributions from separate "surface" coils overlap to define a limited inner-volume deep within a human body or other object under examination. A spin echo MRI signal is effectively elicited only from such limited inner-volume so as to permit conventional MRI signal processing (e.g., utilizing Fourier Transformations) to derive and display magnetic resonance images of desired cross-sections of the limited inner-volume thus avoiding possible motion artifact and/or other potential noise sources located elsewhere in the object. A special receiver coil decoupling circuit is used to automatically increase its resonant frequency during RF transmit times.

Abstract: First and second co-located axially extending RF coils are displaced spatially with respect to one another by 90 degrees so as to produce a pair of RF signals from the enclosed volume which are in phase quadrature. The same coils or one of them may also be utilized for transmitting NMR RF signals into the same volume. The coils have a common open-end through which objects to be imaged may be inserted and a common "closed" end for convenient location of RF coupling and feeding structures. Each of the coils has an RF feedline structure which extends across a diameter of common closed end and the two feedline structures are disposed substantially perpendicular with respect to one another so as to minimize cross coupling. The feedlines are also spatially configured to facilitate mounting of associated tuning and coupling capacitors.