1. Fig. 1. Images of the three E-field cells. Two cells fit inside a 5 mm NMR tube (a) and produce and E-field  (b) and // (c) to the B o field. The third cell (d) is located inside an MRI phantom. 1 cm NMR Tube Copper Wires Teflon Rod Platinum Electrodes Propylene Carbonate Tube Spinner a EBoEBo Electrodes b E//B o Electrodes c Electric Cell d Experimental Methods Two electric field cells were constructed to fit inside a standard 5 mm NMR tube. (See Fig. 1.) One produced an electric field perpendicular (  ) to B o and had platinum electrodes separated by 3 mm. The second cell produced an electric field parallel (//) to B o with copper electrodes separated by 2 mm. We estimate that ~90% of the sample experiences the applied E in the  cell while 100% does in the // cell. The signal was calculated as the integrated absorption signal. NMR measurements from these cells were made on a 7 T NMR spectrometer (Bruker Biospin). R 1 values were measured using a 32 or 128 point inversion recovery (IR) sequence. R 2 measurements were made using a 32 point CPMG with t=500  s and single-echo, spin- echo (SE) sequences. Another larger, 7.6 ml volume cell with copper electrodes separated by 2 cm was constructed inside a Teflon® container and imaged with a 1.5 T imager (GE Healthcare) within an MRI resolution phantom with additional R 2 standards. R 2 measurements were made on this cell using a series of four-echo SE sequences and their magnitude images. All cells were filled with pure propylene carbonate (Sigma-Aldrich) and measurements made at 20 °C. All the cells were connected to a battery pack located outside the magnet which could supply 0 to 235 V DC. Relaxation rates were determined using either mono- or bi-exponential fits or an inverse Laplace transform. [1] Magnetic Resonance Laboratory OCHESTER MEDICAL CENTER UNIVERSITY of R Yujie Qiu, 1 Wing-Chi E. Kwok, 2 Joseph P. Hornak 1 1 Rochester Institute of Technology, Rochester, NY 14623; 2 University of Rochester, Rochester, NY 14642 Electric Field NMR and Spin Relaxation in Propylene Carbonate Motivation & Background We were motivated to study the effect of an electric field on the 1 H spin-lattice and spin-spin relaxation rates (R 1 and R 2 respectively) in our search for a dynamic functional MRI (fMRI) phantom. Our goal is to rapidly and reversibly change the R 2 of a polar liquid by the application of an electrical potential (E), thus mimicking the change in R 2 * from the blood oxygen level dependent (BOLD) response used in fMRI. Electric fields can change the dipole-dipole interaction, anisotropic part of the scalar interaction, and chemical-shift anisotropy of spins in polar molecules, and hence R 1 and R 2. Results & Discussion The R 1 and R 2 values were different for the four 1 H types in propylene carbonate without E. (See Fig. 2.) The four proton chemical shifts were not resolvable in any of the three cells due to B o inhomogeneities. In the NMR cell, the inhomogeneities were from the electrodes. The mean R 1 value did not change with the application of E, but their distribution became broader. This might explain the conflicting literature on R 1. [2,3] The CPMG signal decay for E//B o and E  B o was clearly bi-exponential with R 2 values of approximately 0.77 and 21.5 s - 1. Both R 2 values remained approximately the same for E//B o, but for E  B o the small R 2 value increased at a linear dR 2 /dE = 1.5×10 -5 ms -1 V - 1 while the large R 2 value decreased at -4.9×10 -5 ms -1 V -1. E is having an effect on R 1 and R 2, however, these changes are insufficient to base an fMRI phantom on. [4,5] The spin echo signal intensity decreases with the R 2 rate constant values in Table 1, and is also modulated by the four J couplings between the four unique proton types. (See Fig. 3.) The echo modulation causes the signal in our inhomogeneous B o systems to decrease as a function of the echo time (TE). The echo modulation is not visible and the decay appears mono-exponential for the NMR data when 7.5 < TE < 60 ms and for the MRI data when 15 < TE < 150 ms. (See Fig. 4.) These decays were fit with an apparent R 2 (R’ 2 ). Table 1. R 1 and R 2 values of propylene carbonate with E=0. H  (ppm) R 1 (s -1 )R 2(CPMG) (s -1 ) ab a1.4970.670.6342.4 B4.0310.460.5830.2 C4.5610.440.5619.4 D4.8630.320.4732.2 (d) (c) (b) (a) Conclusions We conclude the following about the propylene carbonate system. An E field has an effect on the R 1 and R 2. The effect is largest for R 2 with E  B o, but too small to use as an fMRI dynamic phantom. On the other hand, the echo modulation frequencies change with the application of E  B o, but not E//B o, causing a change in the effective R 2. This change is suitable to mimic the BOLD response in fMRI and use in a dynamic fMRI phantom. References 1.SW Provencher, Phys Comm 27:229-242 (1982). 2.GP Jones, A Bradbury, PA Bradley. Mol Cryst Liq Cryst 55:143-150 (1979). 3.TM Plantenga, HA Lopes Cardozo, J Bulthuis, C. Maclean. Chem Phys Lett 81:223-226 (1981). 4. S Ogawa, DW Tank, et al., Proc Natl Acad Sci 89:5951-5955 (1992). 5. J Olsrud, A Nilsson, et al., Magn Reson Imag 26:279-286 (2008). Results & Discussion For E  B o, dR’ 2 /dE = 9.2×10 -4 and 4.5×10 -4 ms -1 V -1 for 7 and 1.5 T respectively. At both field strengths, dR’ 2 /dE  0 for E//B o. We believe the application of E  B o changes the echo modulation frequencies slightly thus changing R’ 2. Fig. 5. is a magnetic resonance image of the fMRI phantom with center electric cell. The artifact from the electric wire leading to the cell is visible in the mid upper right of the image. Table 2. Relaxation rates of propylene carbonate and their change with E. Relaxation Type R1R1 R2R2 R’ 2 B o (T)7771.5 SequenceIRCPMGSE E:B o Orientation EBoEBo E//B o EBoEBo EBoEBo EBoEBo R i (s -1 )0.4210.7821.130.7521.8057.8365.3520.2522.47 dR i /dE (m s -1 V -1 ) 01.6×10 -8 4.5×10 -6 1.5×10 -5 -4.9×10 -5 8.5×10 -6 9.2×10 -4 6.4×10 -5 4.5×10 -4 Electric Cell R 2 Standard H(a) H(b) H(d) H(c) H(a)+H(b)+H(c)+H(d) Fig. 3. Echo modulation pattern for the four chemical shift com- ponents and the summation. Highlighted portion represents R 2 ’ fit region. Fig. 4. Spin echo signal of propylene carbonate as a function of TE with and without electric field at 1.5 T. Fig. 5. Spin echo signal of the fMRI phantom showing electric field cell, R 2 standards, and resolution grid. Fig. 2. Structure of propylene carbonate indicating the four proton types. For a poster copy, see http://www.cis.rit.edu/people/faculty/hornak/conf-pre/ENC-2012/.