Room: Exhibit Hall | Forum 8
Purpose: Thermochemical ablation (TCA) is a novel treatment under development for hepatocellular carcinoma, or liver cancer, and exploits exothermic acid/base neutralization chemistry. The reaction products, a concentrated salt and heat, induce simultaneous osmotic and thermal stress when introduced into tissues. Accurate mapping of both thermal and osmotic mechanisms is required for accurate dose determination as well as to understand and eventually predict tumor response. We previously showed that trifluoracetic acid (TFA) can serve for the acid, can ablate tissues, and can be imaged in this context. In the present work, we test the hypothesis that fluorine-19 magnetic resonance relaxometry (Â¹â?¹F-MRR) of TFA could be applied to thermal imaging in TCA.
Methods: Spin-lattice relaxation time constants (Tâ‚?) were measured for 2.0M TFA over a series of temperatures ranging from 14Â°C to 42Â°C. A rapid acquisition with relaxation enhancement (RARE) sequence was used with 15-, 10-, 5-, 1-, and 0.5-second repetition times, 32 x 32 matrix, 30mm x 30mm field-of-view, 10mm slice thickness, 2 averages, and echo train length of 16. From Tâ‚? values, relaxation rate constants (Râ‚?) were calculated and plotted against temperature. A linear least-squares-weighted regression analysis was used to determine fit.
Results: Â¹â?¹F-MRR of TFA showed a strong linear relationship between Râ‚? and temperature (rÂ²=0.9529) across the full range in the experiment. The relationship is characterized by a slope of -3.46E-06 and vertical intercept of 7.22E-04. Tâ‚? values spanned from 1470.16 to 1651.16 ms over the temperature range of 14Â°C to 42Â°C, resulting in a 1.01E-04 change in Râ‚? value over a span of approximately 28â?°C
Conclusion: Linearity between Râ‚? and temperature in these experiments supports the use of Â¹â?¹F-MRR to study thermal dose in TCA. Determination of absolute temperature should be feasible via direct comparison of baseline data to the Râ‚? values measured in tissue following TCA.