Experimental evaluation of nonlinearities of small-sized insertable gradient coils

A phase imaging technique is proposed to map out and quantify gradient nonl inearities of small-sized insertable gradient coils, assuming the whole-bod y system gradients are highly linear in the domain of interest. The theory is developed and simple equations are derived to allow quantification. It i s applied to a 4-loop 18-cm diameter cylindrical gradient coil of optimal d esign. Experimental gradient nonlinearity maps are obtained for different f ields of view. Gradient non-linearities are quantified locally and in regio ns of interest, shelving close agreement with model data. (C) 1998 Elsevier Science Inc.