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Simultaneous MR temperature imaging and radiofrequency ablation of liver tumor: A pilot study
O. Seror1, M. Lepetit Coiffé2, B. Denis De Senneville3, H. Laumonié4, H. Trillaud4, C. Moonen5, B. Quesson5;
1Hôpital Jean Verdier, AP-HP, Bondy, FRANCE, 2IMF/ ERT CNRS/ Université Bordeaux 2, Bordeaux, FRANCE, 3IMF/ ERT CNRS / Université Bordeaux 2, Bordeaux, FRANCE, 4Service de Radiologie / Hôpital Universitaire St André, Bordeaux, FRANCE, 5IMF / ERT CNRS / Université Bordeaux 2, Bordeaux, FRANCE.
Background: To demonstrate the clinical usefulness of real time quantitative MR temperature imaging for the monitoring of radiofrequency (RF) ablation of liver tumor with a commercially available RF apparatus. Methods: The RF generator was filtered (>100 dB attenuation) for the MR proton frequency (63.5 MHz). Continuous temperature maps were acquired with gradient echo images. Proton resonance frequency method was used to calculate thermal dose (TD) map according Sapareto formula. Height patients (4 men, 4 women, median age 54 years [49-87 years]) with liver tumors (7 HCC, 1 metastasis) poorly visible by US or CT and who were ineligible for surgery were included in this pilot study. The patients were positioned inside a standard 1.5T MR system. Under general anaesthesia, an internally cooled MR compatible radiofrequency electrode was inserted in the tumor to perform a standard RF ablation protocol simultaneously with MR thermometry. Follow-up images were recorded just after RF procedure (D0), 45 days later (D45) and every 3 months using T1-w with gadolinium injection (T1-wGd) and T2-w sequences. Results: No technical failure or complication occurred. Total procedure duration was 3.25+/-0.75 hours (mainly due to electrode positioning). The standard deviation of the MR temperature estimation was 2°C during the ablation procedure. The shape and position of local contrast changes on T1-wGd and T2-w in the heated region corresponded with those of final TD maps. During follow up (median: 7 months) locale tumor progression was observed for two patients who had TD estimations of the size of ablation zone equal or smaller to the size of tumor according at least to one axis (fig.1). Conversely, none of patients who had TD estimation of the size of ablation encompassing widely the two axis of the tumor had tumor local progression after successful primary treatment (fig 1). Conclusions: Quantitative MR temperature imaging using thermal dose concept can predict in real time insufficient RF ablation of liver tumor. Further clinical and radiological follow-up are mandatory to confirm our encouraging results. 
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