New microwave ablation system for unresectable liver tumors that forms large, spherical ablation zones.

Imajo, Kento; Tomeno, Wataru; Kanezaki, Mineo; Honda, Yasushi; Kessoku, Takaomi; Ogawa, Yuji; Yoshida, Keisuke; Yoneda, Masato; Kirikoshi, Hiroyuki; Ono, Masafumi; Kaneta, Tomohiro; Inoue, Tomio; Teratani, Takuma; Saito, Satoru; Nakajima, Atsushi

BACKGROUND AND AIM The aim of this study was to assess the efficacy of a new microwave ablation (MWA) system, the Emprint Ablation System, for the ablation of unresectable large liver tumors (≥ 30 mm). METHODS Twenty-one hepatic tumors (mean diameter, 34.7 mm) from 21 patients who underwent percutaneous MWA were included in this cross-sectional study. A volume analyzer based on computed tomography imaging was used for all patients within the month before and month after the procedure to evaluate the shape and volume of ablation zones. In addition, computed tomography imaging was performed again 3 months after the procedure to evaluate the presence of residual tumors and local recurrence. RESULTS Mean ablation time was 11.3 min, and mean overall procedure time was 33.4 min. An ablated adrenal gland-induced Takotsubo (stress) cardiomyopathy occurred immediately after MWA as a major complication in one patient. Roundness index A, B, and C presented a mean value of 0.94, 0.94, and 1.01, respectively (all values near 1 is a perfect sphere), indicating that a spherical ablation zone was achieved. The mean ablation volume was larger than the volume of tumors (24.5 vs 41.7 cm3 ). Residual tumors were confirmed in only 4.8% of tumors after a single ablation session. There was no local recurrence. CONCLUSIONS In our experience, the new MWA system provides an effective treatment option for unresectable large liver tumors. However, to ablate the liver tumors safely, it is necessary to consider the surrounding organs, such as the adrenal glands.