Safety and effect on ablation size of hydrochloric acid-perfused radiofrequency ablation in animal livers

Radiofrequency ablation with sine and square electrical waveforms to enhance ablation range

Radiofrequency ablation (RFA) is a local treatment modality for primary liver cancers. Although various input parameters of the RF generator have been adjusted to improve the ablation ranges, the limited ablation ranges remain an obstacle to RFA. This study aimed to compare the ablation ranges and efficacy of sine and square electrical waveforms in a mouse tumor model. An RF generator with an adjustable electrical waveform was developed, and its ablation range in the porcine liver was compared. For all RF parameters, the square electrical waveform ablation range was greater than that of the sine electrical waveform (all p < 0.001) in the porcine liver. The 45 BALB/c nude mice were used to evaluate the efficacy of the two electrical waveforms after the RFA. The mean tumor volume in the square group was significantly lower than that in the sine group (p < 0.001), indicating a higher survival rate (60%). The cellular coagulative necrosis, inflammatory cell infiltration, heat shock proteins, cellular necrosis, and tumor necrosis were significantly greater in square electrical waveform than in sine electrical waveform (all; p < 0.05). RFA with square electrical waveforms has therapeutic potential for tumor management with an enhanced ablation range.

Highly efficient magnetic ablation and the contrast of various imaging using biocompatible liquid-metal gallium

Background

Although the powerful clinical effects of radiofrequency and microwave ablation have been established, such ablation is associated with several limitations, including a small ablation size, a long ablation time, the few treatment positioning, and biosafety risks. To overcome these limitations, biosafe and efficient magnetic ablation was achieved in this study by using biocompatible liquid gallium as an ablation medium and a contrast medium for imaging.

Results

Magnetic fields with a frequency (f) lower than 200 kHz and an amplitude (H) × f value lower than 5.0 × 10⁹ Am⁻¹ s⁻¹ were generated using the proposed method. These fields could generate an ablation size of 3 cm in rat liver lobes under a temperature of approximately 300 °C and a time of 20 s. The results of this study indicate that biomedical gallium can be used as a contrast medium for the positioning of gallium injections and the evaluation of ablated tissue around a target site. Liquid gallium can be used as an ablation medium and imaging contrast medium because of its stable retention in normal tissue for at least 3 days. Besides, the high anticancer potential of gallium ions was inferred from the self-degradation of 100 µL of liquid gallium after around 21 days of immersion in acidic solutions.

Conclusions

The rapid wireless ablation of large or multiple lesions was achieved through the simple multi-injection of liquid gallium. This approach can replace the currently favoured procedure involving the use of multiple ablation probes, which is associated with limited benefits and several side effects.

Methods

Magnetic ablation was confirmed to be highly efficient by the consistent results obtained in the simulation and in vitro tests of gallium and iron oxide as well as the electromagnetic specifics and thermotherapy performance comparison detailed in this study Ultrasound imaging, X-ray imaging, and magnetic resonance imaging were found to be compatible with the proposed magnetic ablation method. Self-degradation analysis was conducted by mixing liquid gallium in acidic solutions with a pH of approximately 5–7 (to imitate a tumour-containing microenvironment). X-ray diffraction was used to identify the gallium oxides produced by degraded gallium ions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12938-022-01003-9.

Comparison of hydrochloric acid infusion radiofrequency ablation with microwave ablation in an ex vivo liver model

Objectives: To compare sizes and shapes of ablation zones resulting from hydrochloric acid infusion radiofrequency ablation (HRFA) and microwave ablation (MWA), using normal saline infusion radiofrequency ablation (NSRFA) as a control, at a variety of matched power settings and ablation durations, in an ex vivo bovine liver model.Methods: A total of 90 ablation procedures were performed, using each of three modalities: NSRFA, HRFA, and MWA. For each modality, five ablation procedures were performed for each combination of power (80 W, 100 W, or 120 W) and duration (5, 10, 20, 30, 45, or 60 min). The size of ablation zones were compared using ANOVA, the Kruskal-Wallis test, or generalized linear regression.Results: For ablation durations up to 30 min, mean transverse diameter (TD) after HRFA and MWA did not differ significantly (β = 0.13, p = .20). For ablation durations greater than 30 min, mean TD was significantly larger after HRFA than after MWA (β = 1.657, p < .001). The largest TD (9.46 cm) resulted from HRFA performed with 100 W power for 60 min.Conclusions: Compared to MWA, monopolar HRFA with power settings of 80 W-120 W and durations of less than 30 min showed no significant difference. When duration of more than 30 min, HRFA created larger ablation zones than MWA.

A Novel Method to Increase Tumor Ablation Zones With RFA by Injecting the Cationic Polymer Solution to Tissues: In Vivo and Computational Studies

OBJECTIVE

This study aims to examine, for the first time, the introduction of cationic polymer solutions to improve radiofrequency ablation (RFA) in terms of a potentially enlarged ablation zone.

METHODS

By using in vivo and computational RFA studies, two cationic polymers, Chitooligosaccharides (COS) and carboxymethyl chitosan (CMC), diluted in deionized water, were injected into tissues separately surrounding the RF bipolar electrode prior to power application. A total of 9 rabbits were used to 1) measure the increase in electrical conductivity of tissues injected with the cationic polymer solutions, and 2) explore the enhancement of the ablation performance in RFA trials. A computer model of RFA comprising a model of the solution diffusion with an RF thermal ablation model was also built, validated by the in vivo experiment, to quantitatively study the effect of cationic polymer solutions on ablation performances.

RESULTS

Compared to the control group, the electrical conductivity of rabbit liver tissues was increased by 42.20% (0.282 ± 0.006 vs. 0.401 ± 0.048 S/m, P = 0.001) and 43.97% (0.282 ± 0.006 vs. 0.406 ± 0.042 S/m, P = 0.001) by injecting the COS and CMC solution at the concentration of 100 mg/mL into the tissues, denoted COS_DW100 and CMC_DW100, respectively. Consequently, the in vivo experiments show that the ablation zone was enlarged by 95% (47.6 ± 6.3 vs. 92.6 ± 11.5 mm², P < 0.001) and 87% (47.6± 6.3 vs. 88.8 ± 9.6 mm², P < 0.001) by COS_DW100 and CMC_DW100, respectively. The computer simulation shows that the ablation zone was enlarged by 71% (51.9 vs. 88.7 mm²) and 63% (51.9 vs. 84.7 mm²) by COS_DW100 and CMC_DW100, respectively.

CONCLUSION

The injection of the cationic solution can greatly improve the performance of RFA treatment in terms of enlarging the ablation zone, which is due to the increase in the electrical conductivity of liver tissues surrounding the RF electrode.

SIGNIFICANCE

This study contributes to the improvement of RFA in the treatment of large tumors.

Hydrochloric acid enhanced radiofrequency ablation for treatment of large hepatocellular carcinoma in the caudate lobe: Report of three cases

BACKGROUND

To report on the use of percutaneous hydrochloric acid (HCl) enhanced radiofrequency ablation (HRFA) for the treatment of large (maximum diameter ≥ 5 cm) hepatocellular carcinoma (HCC) in the caudate lobe.

CASE SUMMARY

Between August 2013 and June 2016, three patients with a large HCC (maximum diameter: 5.0, 5.7, and 8.1 cm) in the caudate lobe were treated by transarterial chemoembolization followed by computer tomography (CT) guided RFA using a monopolar perfusion RF electrode, which was enhanced by local infusion of 10% HCl at 0.2 mL/min (total volume, 3 to 12 mL). The output power of HRFA reached 100 W, and the average ablation time was 39 min (range, 15 to 60 min). Two patients each underwent one session of HRFA and one patient two sessions. After treatment, CT/magnetic resonance imaging showed that all the three lesions were completely ablated. There was no major complication. Two patients had asymptomatic bile duct dilatation. One patient died of tongue cancer 24 mo after ablation. The remaining two patients were alive and no area of enhancement is detected in the caudate lobe at 28 and 60 mo after ablation, respectively.

CONCLUSION

Percutaneous CT-guided HRFA is safe and efficacious in treating large HCC in the caudate lobe.