A SADDLE QUADRATURE RF COIL for IN VIVO RODENT IMAGING at 21.1 T Jose A. Muniz 1,2, Jens T. Rosenberg 1,2 & S.C. Grant 1,2 1 The National High Magnetic Field Laboratory 2 Chemical & Biomedical Engineering, Florida State University

Introduction Simulated B 1 field distribution Haase et al., 2000

 UWB 21.1-T magnet (900 MHz 1 H)  Vertical system  64 mm gradient clearance  Bruker Avance III Console  Animal care and monitoring  Can accommodate large rodents (> 350 g) In Vivo Animal Imaging at NHMFL Coil assembly mounted on animal cradle Qian et al., 2012

 Readily fits current animal probe  Two RF Channels  External tuning (x4 variable capacitors)  Localized field of view  Rodent head/body imaging  Rat brain  Mouse body  Center of brain located mm away  Deliver Sensitivity for  MR microscopy  MR spectroscopy (selective excitation)  Fast imaging techniques Quadrature Surface Coil Quad Surface Coil pictured next to 21.1 T magnet

 Copper-clad laminates adhered to 35.7mm fiberglass epoxy former  32 x 30 mm  ~100° azimuthal coverage  Two channel saddle design  Transceive coil configuration  Common center conductor  Single decoupling capacitor  Johanson Giga-Trim (0.6 – 4.5 pF)  Tuning & matching  Voltronics (1-8 pF) Coil Design 0.9 pF Quad coil schematic

 Quadrature excitation achieved via 90° hybrid coupler Coil Design Transmission/Reception Schematic

 S 21 = MHz  Loaded Q (-3 dB bandwidth)  Channel 1 Q = 130  Channel 2 Q = 132 Coil Performance S-Parameter Reflection Curve

Coil Performance Water Phantom Absolute signal intensity profile Comparison to same size linear surface coil

In Vivo SNR Comparison Linear BirdcageQuad Surface Image SNR = 14.6 (n = 6) Image SNR = 27.6 (n = 6)

In Vivo Homogeneity Linear BirdcageQuad Surface

In Vivo Homogeneity Linear Birdcage Quad Surface Absolute signal intensity profile (left to right)

In Vivo Homogeneity Linear Birdcage Quad Surface Absolute signal intensity profile (bottom to top)

 Ultrafast In Vivo Diffusion Imaging  Echo-Planar Imaging  segmented 4-shot EPI-DWI  Super-Resolved Ultrafast Single-Shot Spatiotemporally Encoded Imaging  single-shot SPEN DWI Applications (EPI & SPEN)  Frequency sweep insensitive to B 1 inhomogeneities  Quadrature Surface coil provides the necessary sensitivity

 In Vivo MCAO Stroke Rat 21.1 T  Acquisition times for either 4 or 6 b values  SE-DWI (>1.5 h), 2-Shot EPI-DWI (2.4 m), 1-Shot SPEN-DWI & EPI (1.2 m) Applications (EPI & SPEN) In Vivo MCAO stroked rat magnitude DWI and ADC maps

 Longitudinal Relaxation Enhancement (LRE)  Spectrally Selective Excitation  SNR Enhancement Applications (LRE 1 H MRS) Selective excitation pulse based on Shinnar-Le Roux (SLR) algorithm

 In Vivo Stroke Rat Model: Middle cerebral artery occlusion (MCAO)  Male Sprague Dawley rats ~250 g  5 mm 3 voxel Applications (LRE 1 H MRS)

 In Vivo Rat Model: 5 mm 3 voxel Applications (DW Metabolic 1 H MRS) Control Stroke

 900 MHz Quadrature Surface Coil  Localized Field of View  Enhanced Sensitivity  Provides sufficient sensitivity for  Ultrafast imaging techniques  fMRI, water-based diffusion imaging at high field, super-resolution  Spectrally selective MRS  Upfield and Downfield Spectra  Compartmental Diffusion Weighted Metabolic Spectroscopy  Probing compartments in normal & pathological tissue Conclusions

 Prof. Samuel C. Grant  Dr. Jens T. Rosenberg  Funding provided by:  User Collaborative Grant Program (NHMFL) Acknowledgements Posters # 46, 47