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Monitoring Thermochemical Ablation Using Fast Chemical Shift Magnetic Resonance Imaging

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C MacLellan

C MacLellan1,2*, F Maier1, E Cressman1, R Stafford1,2, (1) The University of Texas MD Anderson Cancer Center, Houston, Texas, (2) The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas


SU-E-J-180 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: To investigate the feasibility of using fast chemical shift imaging (fCSI) to directly image the chemical species associated with exothermic acid/base reactions during thermochemical ablation (TCA) injections.

Methods: Five different mixtures of 10M acetic acid and 10M sodium hydroxide representing pure reagents, partial neutralization, and complete neutralization (1:0, 3:1, 1:1, 1:3, 0:1) were prepared in 15mL centrifuge tubes to assess impact on fCSI. An MR spectroscopy (MRS) acquisition provided corroborative data. An fCSI acquisition used a multi gradient echo acquisition (n=16) with autoregressive moving average model based spectral estimation. The acquisition was repeated 8 times with shifted echo trains to effectively increase the number of echoes per k-space line to 128 and the spectral bandwidth from 2.82 ppm to 22.7 ppm. The T1 of each sample was measured using inversion recovery FSE.

Results: The 1H chemical shift of acetate measured via MRS was 2.65 ppm and 2.40 ppm to 2.87 ppm (mean=2.63 ppm) on fCSI , with 2.8 ppm expected. The difference between the chemical shift of water and acetate within the same sample and the T1 in each sample increase with the concentration of acetate ion and range from 2.82ppm to 3.90 ppm and 323ms to 1743ms, respectively.

Conclusion: In this work we evaluated a fCSI acquisition for measuring the MR parameters of acid and base solutions that have been investigated for use in TCA. The importance of shimming the main magnetic field was highlighted by the variation in the position of the acetate peak in the fCSI acquisition. The changes in the chemical shift difference between water and acetate and T1 relaxation suggest a dependence on acetate ion concentration that may be useful and must be accounted for in the monitoring of these procedures.

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