title: A novel method to decrease electric field and SAR using an external high dielectric sleeve at 3 T head MRI: numerical and experimental results.
abstract: Materials with high dielectric constant (HDC) have been used in high field MRI to decrease specific absorption rate (SAR), increase magnetic field intensity, and increase signal-to-noise ratio. In previous studies, the HDC materials were placed inside the RF coil decreasing the space available. This study describes an alternative approach that considers an HDC-based sleeve placed outside the RF coil. The effects of an HDC on the electromagnetic (EM) field were studied using numerical simulations with a coil unloaded and loaded with a human head model. In addition, experimental EM measurements at 128 MHz were performed inside a custom-made head coil, fitted with a distilled water sleeve. The numerical simulations showed up to 40% decrease in maximum 10 g-avg. SAR on the surface of the head model with an HDC material of barium titanate. Experimental measurements also showed up to 20% decrease of maximum electric field using an HDC material of distilled water. The proposed method can be incorporated in the design of high field transmit RF coils.
authors.forename: Bu S
authors.initials: BS
authors.lastname: Park
authors.forename: Sunder S
authors.initials: SS
authors.lastname: Rajan
authors.forename: Joshua W
authors.initials: JW
authors.lastname: Guag
authors.forename: Leonardo M
authors.initials: LM
authors.lastname: Angelone
mesh_terms: D017609:Barium Compounds; D003198:Computer Simulation; D004574:Electromagnetic Fields; D006257:Head / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods*; D059629:Signal-To-Noise Ratio; D014025:Titanium
chemical_list: D017609:Barium Compounds; C024547:barium titanate(IV); D014025:Titanium