Radiofrequency ablation in a porcine liver model: Effects of transcatheter arterial embolization with iodized oil on ablation time, maximum output, and coagulation diameter as well as angiographic characteristics

Particle swarm optimization solution for roll-off control in radiofrequency ablation of liver tumors: Optimal search for PID controller tuning

The study investigates the efficacy of a bioinspired Particle Swarm Optimization (PSO) approach for PID controller tuning in Radiofrequency Ablation (RFA) for liver tumors. Ex-vivo experiments were conducted, yielding a 9th order continuous-time transfer function. PSO was applied to optimize PID parameters, achieving outstanding simulation results: 0.605% overshoot, 0.314 seconds rise time, and 2.87 seconds settling time for a unit step input. Statistical analysis of 19 simulations revealed PID gains: Kp (mean: 5.86, variance: 4.22, standard deviation: 2.05), Ki (mean: 9.89, variance: 0.048, standard deviation: 0.22), Kd (mean: 0.57, variance: 0.021, standard deviation: 0.14) and ANOVA analysis for the 19 experiments yielded a p-value ≪ 0.05. The bioinspired PSO-based PID controller demonstrated remarkable potential in mitigating roll-off effects during RFA, reducing the risk of incomplete tumor ablation. These findings have significant implications for improving clinical outcomes in hepatocellular carcinoma management, including reduced recurrence rates and minimized collateral damage. The PSO-based PID tuning strategy offers a practical solution to enhance RFA effectiveness, contributing to the advancement of radiofrequency ablation techniques.

Combined trans-arterial embolisation and microwave ablation for the treatment of large unresectable hepatic metastases (>3 cm in maximal diameter)

PURPOSE

To assess the safety and efficacy of a two-step single-session procedure, combining transarterial embolization (TAE) and percutaneous microwave ablation (MWA), in the treatment of > 3 cm unresectable liver metastases. We also compared the final volume obtained by the two techniques (V_E-T) and the expected ablation volume of the stand-alone MWA (V_T).

METHODS

From January 2015 to December 2017, 22 consecutive patients, with a total of 24 unresectable hepatic metastases >3 cm in diameter underwent a two-step single-session combined treatment of TAE and MWA. Follow-up computed tomography scans were performed at 1-, 3-, 6-, 12, and 24 months post-procedure. V_E-T as final ablation volume induced by the combined treatment (TAE-MWA), V_N as initial nodule volume, V_T as expected ablation volume of MWA treatment alone were evaluated and compared.

RESULTS

Tumor dimensions ranged from 32 to 73 mm. Technical success was achieved in all treated tumors with no local tumor recurrence. Final ablation volumes ranged from 50 to 450 cm³ and the short-axis diameter of the ablation zone ranged from 12 to 48 mm. The mean ΔV increment in the final ablation volume with respect to the stand-alone MWA was 196% (ranging from 25 cm³ - 210 cm³) (p < 0.05). The V_E-T mean was four times the V_N mean, while the V_T mean was about twice the V_N mean. No recurrence and only one case of post-embolization bleeding were observed.

CONCLUSIONS

This study demonstrated the safety and efficacy of a combined two-step single-session TAE-MWA treatment of unresectable hepatic metastases > 3 cm in diameter.

Liver Ablation: Best Practice

Tumor ablation in the liver has evolved to become a well-accepted tool in the management of increasing complex oncologic patients. At present, percutaneous ablation is considered first-line therapy for very early and early hepatocellular carcinoma and second-line therapy for colorectal carcinoma liver metastasis. Because thermal ablation is a treatment option for other primary and secondary liver tumors, an understanding of the underlying tumor biology is important when weighing the potential benefits of ablation. This article reviews ablation modalities, indications, patient selection, and imaging surveillance, and emphasizes technique-specific considerations for the performance of percutaneous ablation.

Radiofrequency ablation combined with transcatheter therapy in rabbit VX2 liver tumors: effects and histopathological characteristics

BACKGROUND

Transarterial chemoembolization (TACE) combined with radiofrequency ablation (RFA) treatment (TACE-RFA) has been confirmed superior to TACE or RFA alone in animal liver tumors. TACE before RFA was shown to increase hepatocellular damage. Further optimization of the combination strategy for transcatheter arterial embolization (TAE) or TACE combined with RFA is warranted.

PURPOSE

To determine the optimal strategy for radiofrequency ablation combined with transcatheter therapies in VX2 liver tumors in a rabbit model.

MATERIAL AND METHODS

Twenty-four Japanese White rabbits with VX2 liver tumors were randomly divided into four groups: TACE-RFA (TACE-RFA group), transcatheter arterial embolization (TAE) combined with RFA treatment (TAE-RFA group), RFA only group, and TACE only group. Blood samples were collected 1 day before the operation and at 3 and 7 days postoperatively. Seven days after the operation, maximal diameters of coagulation or infarcted zones in the gross specimens, CT images, histopathological characteristics, tumor necrotic rate, and growth rate were compared.

RESULTS

Significantly larger mean long-axis (P < 0.05) and short-axis (P < 0.05) diameters of coagulation and infarction were observed in the TACE-RFA group compared with the TAE-RFA, RFA, and TACE groups on day 7; and the TAE-RFA group showed a significant (P < 0.05) increase versus the RFA and TACE groups on day 7. There were no significant differences in tumor growth rate (109.3 ± 37.5 vs. 119.0 ± 43.1%, P = 0.45) and necrotic rate (89.5 ± 12.0 vs. 83.5 ± 9.3%, P = 0.73) between the TACE-RFA and TAE-RFA groups. TACE-RFA was more effective for achieving tumor destruction than the other treatment strategies, but led to increased rabbits discomfort and more severe liver dysfunction compared with TAE-RFA.

CONCLUSION

TAE-RFA appears to be a beneficial therapeutic modality for treating VX2 liver tumors in a rabbit model.

Superselective particle embolization enhances efficacy of radiofrequency ablation: effects of particle size and sequence of action

PURPOSE

To evaluate the effects of particle size and course of action of superselective bland transcatheter arterial embolization (TAE) on the efficacy of radiofrequency ablation (RFA).

METHODS

Twenty pigs were divided into five groups: group 1a, 40-μm bland TAE before RFA; group 1b, 40-μm bland TAE after RFA; group 2a, 250-μm bland TAE before RFA; group 2b, 250-μm bland TAE after RFA and group 3, RFA alone. A total of 40 treatments were performed with a combined CT and angiography system. The sizes of the treated zones were measured from contrast-enhanced CTs on days 1 and 28. Animals were humanely killed, and the treated zones were examined pathologically.

RESULTS

There were no complications during procedures and follow-up. The short-axis diameter of the ablation zone in group 1a (mean ± standard deviation, 3.19 ± 0.39 cm) was significantly larger than in group 1b (2.44 ± 0.52 cm; P = 0.021), group 2a (2.51 ± 0.32 cm; P = 0.048), group 2b (2.19 ± 0.44 cm; P = 0.02), and group 3 (1.91 ± 0.55 cm; P < 0.001). The greatest volume of ablation was achieved by performing embolization with 40-μm particles before RFA (group 1a; 20.97 ± 9.65 cm(3)). At histology, 40-μm microspheres were observed to occlude smaller and more distal arteries than 250-μm microspheres.

CONCLUSION

Bland TAE is more effective before RFA than postablation embolization. The use of very small 40-μm microspheres enhances the efficacy of RFA more than the use of larger particles.

Radiofrequency ablation in a porcine kidney model: effect of occlusion of the arterial blood supply on ablation temperature, coagulation diameter, and histology

BACKGROUND

Radiofrequency ablation (RFA) is susceptible to the cooling effect of flowing blood. The reduced efficacy of RFA in large tumors reflects the in vivo biophysiological limitations imposed by perfusion-mediated vascular cooling.

PURPOSE

To compare the effects of RFA alone and of RFA combined with occlusion of the arterial blood supply on the tissue temperature, coagulation diameter, and histological changes in the acute phase.

MATERIAL AND METHODS

The temperature at roll-off, the coagulated tissue diameter, and histologic tissue changes were compared in normal porcine kidneys subjected in situ to two pigs each were subjected to RFA alone (four kidneys) or to RFA plus balloon occlusion of the renal artery (four kidneys). The tissue temperature was measured at three sites: area I, the center of the RFA field; area II, the ischemic field 1 cm distant from the edge of the RFA field; and area III, the normal kidney. Tissue samples were stained with hematoxylin and eosin (H&E). Cell viability in the ablated zone was determined by nicotinamide adenine dinucleotide (NADH) staining of frozen sections.

RESULTS

The tissue temperatures achieved by RFA in areas I, II, and III were 101°C, 58°C, and 40°C with and 92°C, 44°C, and 38°C without balloon occlusion, respectively. The maximal coagulation diameter was 31 mm with and 23 mm without occlusion. The coagulation diameter was significantly larger and the temperature in area II was significantly higher in kidneys subjected to RFA with renal artery occlusion. H&E staining showed preservation of the normal renal parenchymal structure outside the thermal lesion and an increase in eosinophilic cells with indistinct cell borders and nuclei within the thermal lesion. H&E and NADH staining demonstrated a sharp demarcation between the ablation and normal tissue area and showed that in area II the addition of balloon occlusion did not produce histologic changes different from those in kidneys subjected to RFA alone.

CONCLUSION

A technique that combines RFA and partial renal artery occlusion may be useful in treatment of the non-resectable renal tumors with sizes appropriate for RF ablation.

Effect of interval between transcatheter hepatic arterial embolization and radiofrequency ablation on ablated lesion size in a swine model

PURPOSE

The aim of the study was to clarify the effect of the interval between transcatheter hepatic arterial embolization (TAE) with Lipiodol plus gelatin sponge particles and radiofrequency (RF) ablation on the extent of ablation.

MATERIALS AND METHODS

Eight healthy swine were divided into four groups: RF ablation (ablation only), RF ablation immediately after TAE (immediate ablation), RF ablation 3 days after TAE (3-day ablation), and RF ablation 6 days after TAE (6-day ablation). Five ablated lesions were created in each swine (10 per group). A 2-cm expandable LeVeen needle electrode was used for RF ablation. Ablated lesions are composed of an outer reddish zone and an inner whitish zone.

RESULTS

The average longest length of the major, intermediate, and minor axes and the volume in the immediate ablation, 3-day ablation, and 6-day ablation groups were significant longer and greater (1.52 and 1.52, 1.46 and 1.50, and 1.37 and 1.35 times greater in the red zone and the whitish area, respectively) than those in the ablation-only group (P < 0.05/3). Accumulation of Lipiodol was still noted in the hepatic sinusoids in the 3-day and 6-day ablation groups.

CONCLUSION

RF ablation delayed to 6 days following TAE produced larger ablation volumes than did RF ablation alone.

Effectiveness of hepatic arterial embolization on radiofrequency ablation volume in a swine model: relationship to portal venous flow and liver parenchymal pressure

PURPOSE

To evaluate the effectiveness of transcatheter arterial embolization (TAE) on radiofrequency (RF) ablation volume and compare portal vein (PV) flow and liver parenchymal pressure before and after treatment.

MATERIALS AND METHODS

Eight healthy female swine were divided into four groups to be treated with RF ablation alone (RF-only group), RF ablation after TAE with gelatin sponge particles (GSPs; RF/TAE group), RF ablation after TAE with Lipiodol plus GSPs (RF/TAE/Lipiodol group), and PV embolization (PVE) with GSPs after TAE with Lipiodol plus GSPs (RF/TAE/Lipiodol/PVE group). Five ablations were created in each swine, with 10 ablations per group. A 2-cm expandable LeVeen needle electrode was used for RF ablation.

RESULTS

The greatest ablation volume (18,410.1 mm(3) +/- 3,986.4) was observed in the RF/TAE/Lipiodol/PVE group. Of the RF-only, RF/TAE, and RF/TAE/Lipiodol groups, the RF/TAE/Lipiodol group (14,835.5 mm(3) +/- 2,743.2) had a significantly larger ablation volume than the RF-only (8,002.6 mm(3) +/- 2,788.3) and RF/TAE groups (10,398.5 mm(3) +/- 2965.8; P < .05/3). PV pressures increased significantly after TAE (P < .01) compared with the pressure before TAE in the RF/TAE/Lipiodol and RF/TAE/Lipiodol/PVE groups, but not in the RF/TAE group. A marked increase in liver parenchymal pressure was seen during RF ablation; however, there were no significant differences among groups. Accumulation of Lipiodol was noted in the sinusoids in the RF/TAE/Lipiodol and RF/TAE/Lipiodol/PVE groups.

CONCLUSIONS

TAE with blockade of PV flow before RF ablation was associated with greater ablation volumes. Liver parenchymal pressure showed no correlation with increased ablation volume.