A 3-DIMENSIONAL NMR IMAGING SCHEME UTILIZING DOUBLY RESONANT GRADIENTCOILS

A 3DFT gradient-echo technique has been developed which, in conjunctio n with series-resonant gradient-coil circuits, can produce three-dimen sional NMR images with an echo time of less than 100 mu s. The method involves a read-gradient waveform composed of two sinusoids of differe nt frequencies. This is an improvement on previous imaging sequences u sing a single sinusoid where only half of k space was sampled and wher e the second half was calculated using conjugate symmetry. The inaccur acies involved in the necessary ''cut and paste'' of k space inevitabl y lead to artifacts in the final image. The important features of the new method are that with suitable phase encoding all octants of k spac e are sampled, the RF pulse is applied when the gradients are all zero , and the echo forms when the gradient is essentially constant. This m ethod will allow more extensive application of solid imaging technique s to biological samples in vivo. (C) 1996 Academic Press, Inc.