METHODS OF PRODUCING IMAGE INFORMATION FROM OBJECTS

摘要

PCT No. PCT/GB81/00045 Sec. 371 Date Nov. 9, 1981 Sec. 102(e) Date Nov. 9, 1981 PCT Filed Mar. 13, 1981 PCT Pub. No. WO81/02789 PCT Pub. Date Oct. 1, 1981.To produce image information from an object it is subjected to a continuous static magnetic field along a Z axis and to sets of sequences of gradient Gx, Gy and Gz to the magnetic field. Spins in a selected plane (the X-Z plane) are excited by selective rf pulses and an associated Gy gradient and the selected spins are subjected to a reversed Gy gradient together with a Gx gradient. The Gy gradient is then switched off and the direction of the Gx gradient is then repeatedly reversed. During the action of reversal of the Gx gradient a small Gz gradient is provided. Each reversed Gx gradient is held constant for a sufficient time for a free induction decay signal to be generated thus providing a multiple echo of the spins in the selected plane. Alternate signals are time-reversed and then both the time-reversed and non time-reversed signals are subject to Fourier transformation.