title: Increasing signal homogeneity and image quality in abdominal imaging at 3 T with very high permittivity materials.
abstract: 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.
authors.affiliation: Department of Telecommunications, Technical University of Delft, Delft, The Netherlands.
authors.forename: P
authors.initials: P
authors.lastname: de Heer
authors.forename: W M
authors.initials: WM
authors.lastname: Brink
authors.forename: B J
authors.initials: BJ
authors.lastname: Kooij
authors.forename: A G
authors.initials: AG
authors.lastname: Webb
mesh_terms: D000005:Abdomen / Q000033:anatomy & histology*; D000328:Adult; D004553:Electric Conductivity; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000295:instrumentation*; D007090:Image Interpretation, Computer-Assisted / Q000295:instrumentation*; D060526:Magnetic Fields; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity