1. In a system for creating an image of in situ biological tissue, using an MRI device to provide sequential epochs of excitation pulses in an inhomogeneous magnetic field, with each epoch generating a measurement of imageable spin echo signals, and wherein each epoch includes an initial 90.degree. tilting pulse followed by at least one 180.degree. refocussing pulse, a method which comprises the steps of: inserting a predetermined x-y encode in each said epoch between said initial 90.degree. tilting pulse and said at least one 180.degree. refocussing pulse, each said encode having a sequential K-space identifier in a form i(1. .. m)+j(1. .. n); alternating said initial 90.degree. tilting pulses between a positive ninety degrees and a negative ninety degrees according to said K-space identifier and where said image has m.times.n pixels, said initial tilting pulse is a negative ninety degrees when i+j is an even number and said initial tilting pulse is a positive ninety degrees when i+j is an odd number; pulsing the tissue with said sequential epochs to obtain a plurality of said measurements; and collating said measurements to create said image.