Percutaneous radiofrequency ablation of HCC: reduced ablation duration and increased ablation size using single, internally cooled electrodes with an optimized pulsing algorithm

Figures & data

Table 1. Radiofrequency ablation parameters by internally cooled electrode tip size using the optimized pulse algorithm.

Electrode tip size (cm)	2	3	4
Sample size	2	11	15
Current (mA) (mean ± sd)	1100	1609 ± 356	1980 ± 86
Range (mA)	1100–1100	1300–2200	1800–2200
Minimum impedance (Ω) (mean ± sd)	76.0 ± 5.7	62.2 ± 7.6	58.4 ± 3.7
Range (Ω)	72–80	53–76	52–64
Duration (min) (mean ± sd)	4.5 ± 2.1	8.7 ± 2.5	8.9 ± 2.4
Range (min)	3–6	6–12	6–12
Max temperature post-ablation (°C)	57	71.1 ± 10.3	79.2 ± 6.5
Coagulation necrosis volume (cc) (mean ± sd)	6.4 ± 1.2	19.4 ± 10.9	47.5 ± 25.6
Range (cc)	5.5–7.2	10.1–47.1	8.5–95.7
Coagulation length (cm) (mean ± sd)	2.7 ± 0.35	3.8 ± 0.55	5.3 ± 1.14
Average coagulation diameter (cm) (mean ± sd)	2.4 ± 0.14	3.3 ± 0.62	4.4 ± 1.0
Sphericity (%) (mean ± sd)	81.7 ± 8.2	81.9 ± 8.4	74.9 ± 12.8
Range (%)	75.9–87.5	63.5–97.1	52.5–96.9

Exposed tip and size of coagulation necrosis are expressed in centimeters, time in minutes.

Figure 1. Short course, large volume RF ablation with long term favorable outcome. (a) A 2.2 cm HCC at S8 (arrow) was ablated with a single insertion of a 4 cm exposed tip RF electrode in 6 min with 2000 mA current. (b) At 24-h, CT the dimensions of the necrosis volume achieved were 4.8 × 4.3 × 5.5 cm. At 2- (c) and 4-year (d) follow-up, ablation was complete with no LTP.

Figure 2. Large volume RF ablation from optimized current and longer electrodes. (a) A 4.2 cm HCC at S4 (arrow) was ablated with a single insertion of a 4 cm exposed tip RF electrode in 12 min with 2200 mA current. (b) At 24-h CT, the dimensions of the necrosis volume achieved were 5.2 × 4.1 × 4.4 cm. (c) At 2-year follow-up, ablation was complete with no LTP.

Figure 3. Local tumor progression post-RF ablation from incomplete treatment. (a) A 3.3 cm HCC at S4 (arrow) was ablated with a single insertion of a 3 cm exposed tip RF electrode in 6 min with 1600 mA current. (b) At 24-h CT, the dimensions of the necrosis volume achieved were 3.5 × 3.3 × 3.5 cm. (c) Although the treatment seemed to be complete, at 9-month follow-up CT, a large region of local tumor progression was noted in the anterior portion of the volume of necrosis (arrows). (d) Retrospective assessment of the pre- and post-ablation CT scans non-rigidly co-registered by Ablation-fit software (RAW s.r.l., Milan, Italy) showed that a small portion (15.4%) of the 5-mm ablative margin (green line) was not achieved in the anteromedial part of the HCC, suggesting incomplete treatment was due to an initial technical failure from sub-optimal electrode placement and ablation coverage. The margins of the volume of necrosis (blue line), of the HCC (orange line), and the ablative margin are exactly overlapping.