OFF-RESONANCE BINOMIAL COMPOSITE PULSES IN 2D AND 3D FAT WATER IMAGING AT 0.5 T

A new method of acquiring two-dimensional (2D) and three-dimensional ( 3D) fat/water decomposed images on a 0.5 T magnetic resonance (MR) ima ging system is described. The method uses a gradient-recalled echo (GR E) sequence incorporating a composite 1(2) over bar1$ pulse, originall y used for magnetization transfer contrast (MTC) experiments, for freq uency-selective pre-saturation. By applying the 1(2) over bar1$ pulse off resonance, a sharp discrimination between the chemically shifted w ater and fat signals may be obtained using a composite pulse as short as 4 ms. Phantom studies demonstrate that suppression ratios as high a s 50:1 are achievable. The new method has been applied to volunteers a nd patients, and good fat/water images of limb, abdomen, head and neck obtained. The new method can be incorporated into other pulse sequenc es related to GRE, such as phase contrast (PC) and time-of-flight (TOF ), and represents the first practical (i.e. rapid) method for 3D fat/w ater imaging at an operating held as low as 0.5 T.