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 B?1+ 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 B?1+ 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 B?1+ 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. Magn Reson Med, 2012. (c) 2012 Wiley Periodicals, Inc.