Methods of deriving image information from objects

A method of deriving image information using nuclear magnetic resonance signals from an object subjected to a static magnetic field along one axis comprising the steps of:

• applying a first gradient to said magnetic field which varies in a direction orthogonal to said axis together with a 90.degree. high frequency pulse, reversing the direction of said magnetic field gradient and applying a second gradient to said magnetic field which varies in a direction orthogonal to said first gradient and then reversing the direction of said second gradient while reading out the free induction signal from said object to obtained an So signal;
• applying a third gradient to said magnetic field which varies in a direction orthogonal both to the first and second gradient and applying an inverting high frequency pulse to the object in the presence of said third gradient to invert nuclear spins in a selected plane therein, then immediately applying the first gradient to said magnetic field together with a 90.degree. high frequency pulse, reversing the direction of said first gradient and applying the second gradient to said magnetic field and then reversing the direction of said second gradient while reading out the free induction signal from said object to obtain an S1 signal;
• and
• calculating a signal which is the difference between the So and S1 signals.