Increasing signal homogeneity and image quality in abdominal imaging at 3 T with very high permittivity materials

The appearance of severe signal drop-outs in abdominal imaging at 3 T arises primarily from areas of very low B1+ transmit field in the body, and is problematic in both obese as well as very thin subjects. In this study, we show how thin patient-friendly pads containing new high permittivity materials can be designed and optimized, and when placed around the subject increase substantially the B1+ uniformity and the image quality. Results from nine healthy volunteers show that inclusion of these dielectric pads results in statistically significant decreases in the coefficient of variance of the B1+ field, with stronger and more uniform fields being produced. In addition there are statistically significant decreases in time-averaged power required for scanning. These differences are present in both quadrature-mode operation (coefficient of variance decrease, P<0.0001, mean 25.4±10%: power decrease, P=0.005, mean 14±14%) and also for the RF-shimmed case (coefficient of variance decrease, P=0.01, mean 16±13%: power decrease, P=0.005, mean 22±11%) of a dual-transmit system.