Abstract Session Viewer

Code: PU	Time Slot/Poster Number: 413	Session: 7 Tesla Imaging & Beyond, Poster
Resonance Frequency of Microstrip RF Coil Evaluation Through Circuit Analysis
Jonathan Lu¹; Bing Wu²; Yong Pang²; Chunsheng Wang²; Xiaoliang Zhang²
¹University of California- Berkeley, Berkeley, CA; ²University of California- San Francisco, San Francisco, CA
Abstract
This study performs an evaluation of the harmonic resonance frequency of a microstrip circuit used as a high field MRI RF coil, which would have three capacitors: two terminating and one placed at the midpoint of the two. This work derives two different equations which solve the microstrip's resonance frequency. By comparing these equations' calculated values with real life measurements, each equation was found to have strengths and weaknesses in its accuracy of estimating 1st harmonic and 2nd harmonic resonance frequencies of a microstrip. These equations may be useful in future microstrip RF Coil design.

Code: PU	Time Slot/Poster Number: 414	Session: 7 Tesla Imaging & Beyond, Poster
EM field and SAR Evaluation of RF Coils or Coil Elements for Ultrahigh Field MRI
Jonathan Lu¹; Yong Pang²; Chunsheng Wang²; Bing Wu²; Xiaoliang Zhang²
¹University of California- Berkeley, Berkeley, CA; ²University of California- San Francisco, San Francisco, CA
Abstract
This study is an evaluation of the ratio of electric field to magnetic field (E/B1) and Specific Absorption Rate (SAR) generated by three different RF transceiver coil setups: surface coil, surface coil with shielding, and microstrip using a finite discrete time domain (FDTD) simulation for both unloaded and loaded case. In the presence of a human head load, the microstrip's E/B1 ratio and SAR was on average the smallest of the three setups, suggesting the microstrip may be a better RF Coil choice for MRI concerning patient safety and parallel excitation performance than the other two coils.

Code: PU	Time Slot/Poster Number: 415	Session: 7 Tesla Imaging & Beyond, Poster
Single Cell Analysis of Osmosis as Assessed by 1H and 23Na High Field MRI
John Walsh^{1, 2}; Parastou Foroutan^{1, 2}; Samuel C. Grant^{1, 2}
¹The Florida State University, Tallahassee, FL; ²National High Magnetic Field Laboratory, Tallahassee, FL
Abstract
Vital to every living organism is a delicate homeostatic balance of intracellular and extracellular ion concentrations critical in regulating osmosis. The resulting concentration gradients are the driving forces for transport across the cell membrane and the basis of signal transduction in excitable cells, such as neurons. By examining the cellular response to different insults of the extracellular environment, much can be observed concerning cell volume regulation through osmosis and the influence of changing ionic concentration distributions on cell swelling in diseased states. Changes of the MRI relaxation parameters (T1,T2, and T2*) as well as the apparent diffusion coefficient (ADC) in isolated neurons and neuronal ganglia can be used to assess changing cellular environments under osmotic perturbation.

Code: PU	Time Slot/Poster Number: 416	Session: 7 Tesla Imaging & Beyond, Poster
Optimization of a Transmit Array Pulse Considering Excitation Uniformity, SAR, and Pulse Duration
Bu Park¹; Christopher Collins²
¹NIH/NIMH, Bethesda, MD; ²The Penn State University, Hershey, PA
Abstract
Except for RF shimming, transmit array pulses are generally expected to require more time than their quadrature-drive, single-pulse counterparts. Although many transmit array pulses can achieve better excitation uniformity than a simple pulse (including RF shimming), to do so in the same time duration with no significant increase in SAR is a challenge. Here we explore the effect of pulse duration in an array-optimized composite pulse (ACP) and in RF shimming designed to both improve excitation uniformity in the whole brain and reduce SAR using an 8-channel transmit head array, and compare results with the conventional quadrature drive at 3T and 7T.