Abstract: A system for detecting a target substance within a class of explosives and narcotics containing quadrupolar nuclei through the use of nuclear quadrupole resonance (NQR). The system applies an RF signal to a coil (34) to excite the substance under test. If the target material is present, an NQR signal will be picked up by the same coil, That signal is compared with known NQR signals in frequency and amplitude. A signal is displayed in an appropriate way if a threshold value of the NQR signal is equalled or exceeded. The empty coil is statically tuned by means of adjusting the location or capacitance values, or both, of static tuning capacitors (102) in the coil. The coil is tuned after the specimen is inserted into the coil by means of an auto-tune feature (36). Effective RFI shielding (37) is provided to prevent external contaminating signals from being detected by the coil and to prevent RF signals from escaping from the scanner. The invention also includes the method for performing tests with the system.

Abstract: Chemical shift imaging with spectrum modeling (CSISM) models the general chemical shift spectrum as a system with N distinct peaks with known resonant frequencies and unknown amplitudes. Based on the N peak spectrum model, a set of nonlinear complex equations is set up that contains N+1 unknowns of two kdnds: the magnitudes of the N peaks, and a phasor map caused by main magnetic field inhomogeneity. Using these equations, the timing parameters for shifting the 180.degree. RF refocusing pulses for acquiring spin-echo images are optimally chosen. Corresponding timing parameters for other pulse sequences can also be optimized similarly. Using the chosen timing parameters, a plurality of images are acquired. Next, acquired image data are automatically processed to solve the complex linear equations. First, the phasor map is found by fitting various phasor map values over a small number of pixels, or "seeds", that are picked sparsely in a field of view.

Abstract: A snap-in, whole-body radio frequency coil (38) for increasing the diameter of a bore (12) of a toroidal magnetic resonance imaging apparatus includes a plurality of longitudinally extending coil elements (42) having element ends (44). The longitudinally extending coil elements are disposed on a flat, flexible, non-conductive plastic sheet (40) which is capable of being rolled and disposed concentricly in an interior diameter of the bore to form a thin-walled, bird-cage type radio frequency coil. Adjacent element ends are connected with a first capacitance C.sub.0 to resonate the coil at a certain frequency. To permit mechanically switching the resonant frequency of the coil, protruding metal contacts (60) are electrically connected to the element ends. An adjustment end ring includes separated metal pads (66) disposed on a non-conducting ring substrate (64). Adjacent metal pads are connected with second capacitances C.sub.1.