Abstract
Purpose To compare the size of the coagulation (CZ) and periablational (PZ) zones created with two commercially available devices in clinical use for radiofrequency (RFA) and microwave ablation (MWA), respectively. Methods Computer models were used to simulate RFA with a 3-cm Cool-tip applicator and MWA with an Amica-Gen applicator. The Arrhenius model was used to compute the damage index (Ω). CZ was considered when Ω > 4.6 (>99% of damaged cells). Regions with 0.6<Ω < 2.1 were considered as the PZ (tissue that has undergone moderate sub-ablative hyperthermia). The ratio of PZ volume to CZ volume (PZ/CZ) was regarded as a measure of performance, since a low value implies achieving a large CZ while keeping the PZ small. Results Ten-min RFA (51 W) created smaller periablational zones than 10-min MWA (11.3 cm3 vs. 17.2−22.9 cm3, for 60−100 W MWA, respectively). Prolonging duration from 5 to 10 min increased the PZ in MWA more than in RFA (2.7 cm3 for RFA vs. 8.3−11.9 cm3 for 60−100 W MWA, respectively). PZ/CZ for RFA were relatively high (65−69%), regardless of ablation time, while those for MWA were highly dependent on the duration (increase of up to 25% between 5 and 10 min) and on the applied power (smaller values as power was raised, 102% for 60 W vs. 81% for 100 W, both for 10 min). The lowest PZ/CZ across all settings was 56%, obtained with 100 W-5 min MWA. Conclusions Although RFA creates smaller periablational zones than MWA, 100 W-5 min MWA provides the lowest PZ/CZ.
Highlights
Energy-based high-temperature ablative therapies such as radiofrequency ablation (RFA) or microwave ablation (MWA) have demonstrated their ability to thermally destroy tumors by creating a coagulation zone that covers a 0.5À1 cm safety margin around the entire tumor
The ratio of periablational zone volume to coagulation zone volume could be considered as a measure of value, since an ideal ablative technique should be able to create a large coagulation zone while keeping the periablational zone as small as possible, i.e., the best technique is the one with the lowest PZ/CZ ratio
Our study compared the size of the coagulation zone and periablational zone created by two commercial devices, i.e., 3-cm Cool-tip RF applicator vs. 14 G AMICA microwave antenna
Summary
Energy-based high-temperature ablative therapies such as radiofrequency ablation (RFA) or microwave ablation (MWA) have demonstrated their ability to thermally destroy tumors by creating a coagulation zone that covers a 0.5À1 cm safety margin around the entire tumor. Evidence is emerging that any tumor regions that do not reach ablative temperatures may be subsequent promoters of tumor growth [1]. This area, called the periablational zone, is always present around the coagulation zone (Figure 1(a)). The ideal ablative technique should be able to create a coagulation zone around the entire tumor plus a 0.5–1 cm margin while keeping the periablational zone beyond the margin as small as possible. The ratio of periablational zone volume to coagulation zone volume could be considered as a measure of value, since an ideal ablative technique should be able to create a large coagulation zone while keeping the periablational zone as small as possible, i.e., the best technique is the one with the lowest PZ/CZ ratio
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