Electricity: measuring and testing – Particle precession resonance – Using a nuclear resonance spectrometer system
Patent
1992-11-10
1994-03-29
Arana, Louis
Electricity: measuring and testing
Particle precession resonance
Using a nuclear resonance spectrometer system
324307, G01V 300
Patent
active
052988627
ABSTRACT:
Method of measuring the nuclear magnetic resonance in selected areas of a body in order to present images of body cross-sections according to the slice-selective two dimensional Fourier-transformation. Wherein, the body is in a homogeneous magnetic field, exposed to a selection gradient and excited by a selective RF-pulse. Wherein a time-limited phase encoding gradient is applied, and finally by means of a read gradient at least one nuclear resonance signal is generated by gradient inversion in the form of at least one so-called gradient echo. Wherein, the selection gradient, the phase encoding gradient, as well as, the read gradient are arranged orthogonally with respect to one another. Wherein, RF-pulses have a high frequency excitation profile, of which the base frequencies of the high frequency differ by a value .DELTA.f corresponding to the distance between the centers of adjacent layers or slices. Wherein different slices are excited by RF-pulses in cooperation with the selection gradient, and wherein, the amplitude and/or duration of the phase encoding gradient is varied. Slice selection frequencies for the recording of at least two phase encoding steps or groups of phase encoding steps and at most all phase encoding steps, which are allocated essentially to the same slice, differ by a frequency increment. Wherein, the allocation of the phase encoding steps to the excitation frequencies in each case is effected such that an almost continuous distribution of phase encoding steps across the measuring volume is achieved. Wherein, layers or slices which belong to a complete recording of the entire volume of the body area overlap one another in such a manner that within a random partial volume which: lies within the measuring volume, can be varied almost continuously, and has a thickness corresponding to .delta.f+.DELTA.f, where .DELTA.f corresponds to the layer distance and .delta.f represents the thickness of a selected layer or slice according to the bandwidth of the selective pulses.
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