CT findings after radiofrequency ablation in rabbit livers: comparison of internally cooled electrodes, perfusion electrodes, and internally cooled perfusion electrodes

[The role of endoscopy in the management of peripheral pulmonary nodules, part 2: Treatment]

The management of peripheral lung nodules is challenging, requiring specialized skills and sophisticated technologies. The diagnosis now appears accessible to advanced endoscopy (see Part 1), which can also guide treatment of these nodules; this second part provides an overview of endoscopy techniques that can enhance surgical treatment through preoperative marking, and stereotactic radiotherapy treatment through fiduciary marker placement. Finally, we will discuss how, in the near future, these advanced endoscopic techniques will help to implement ablation strategy.

Thyroid-dedicated internally-cooled wet electrode for benign thyroid nodules: experimental and clinical study

BACKGROUND

To assess the effects of radiofrequency ablation (RFA) using an internally-cooled wet (ICW) electrode in ex vivo bovine liver and evaluate the feasibility of the ICW electrode for benign thyroid nodules.

METHODS

We developed an 18-gauge ICW electrode with a microhole at the distal tip for tissue infusion of chilled (0 - 4 °C) isotonic saline (rate = 1.5 ml/min). RFA using ICW and IC electrodes were performed in bovine livers (40 pairs, 1-cm active tip, 50 W, 1-min). We compared the morphological characteristics of ablation zones and presence of carbonization. Twenty patients with benign thyroid nodules larger than 5 ml were prospectively enrolled in a clinical study and underwent ultrasound-guided RFA with ICW electrodes. Ultrasound examinations, laboratory data, and symptom and cosmetic scores were evaluated preprocedure and 1 and 6 months after the procedure.

RESULTS

In the ex vivo study, the ICW achieved significantly larger ablation zones than the IC (p<.001). In the clinical study, ICW electrodes were tolerable in all patients. At last follow-up, nodule volume had decreased from 15.6 ± 12.1 ml to 4.1 ± 4.3 ml (p<.001), and the mean volume reduction ratio (VRR) was 73.3 ± 13.7% at 6.0 months follow-up. Cosmetic and symptom scores were reduced from 3.52 ± 1.03 to 2.65 ± 0.88 and 3.10 ± 2.17 to 0.85 ± 0.99 (both p<.001), respectively. After RFA, thyroid function was well preserved in all patients, and mean thyroglobulin level decreased from 36.6 ± 52.1 ng/ml to 26.9 ± 62.2 ng/ml. One patient experienced a temporary voice change that recovered within a week.

CONCLUSIONS

We developed a thyroid-dedicated ICW electrode that we showed to be feasible and effective in patients with benign thyroid nodules.

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.

Design of a Novel Electrode of Radiofrequency Ablation for Large Tumors: In Vitro Validation and Evaluation

In the present study, a monopolar expandable electrode (MEE) in radiofrequency ablation (RFA) proposed in our previous study was validated and evaluated using the in vitro experiment and computer simulation. Two commercial RF electrodes (conventional electrode, CE and umbrella electrode, UE) was used to compare the ablation results with MEE using the in vitro egg white model (experiment and computer simulation) and in vivo liver tumor model (computer simulation) to verify the efficacy of MEE in the large tumor ablation. The sharp increase in impedance during RFA procedures was taken as the termination of RFA protocols. The volume and sphericity of ablation zone generated by MEE, CE, and UE in the in vitro egg white experiment were 75.3 1.6 cm3, 2.7 0.4 cm3, 12.4 1.8 cm3 (P <0.001), and 88.1 0.9%, 12.9 1.3%, 62.0 3.0% (P <0.001), respectively. Correspondingly, a similar result was obtained in the egg white simulation. In the liver tumor simulation, the volume and sphpericity of ablation zone generated by MEE, CE, and UE were 35.4 cm3 and 86.8%, 3.7 cm3 and 17.7%, and 12.7 cm3 and 59.6%, respectively. In summary, MEE has the potential to achieve complete ablation in the treatment of large tumors (>3 cm in diameter) compared with CE and UE due to the larger electrode-tissue interface and more round shape of hooks.

Comparison of switching bipolar ablation with multiple cooled wet electrodes and switching monopolar ablation with separable clustered electrode in treatment of small hepatocellular carcinoma: A randomized controlled trial

OBJECTIVE

A randomized controlled trial was conducted to prospectively compare the therapeutic effectiveness of switching bipolar (SB) radiofrequency ablation (RFA) using cooled-wet electrodes and switching monopolar (SM) RFA using separable clustered (SC) electrodes in patients with hepatocellular carcinomas (HCCs).

MATERIALS AND METHODS

This prospective study was approved by our Institutional Review Board. Between April 2014 and January 2015, sixty-nine patients with 74 HCCs were randomly treated with RFA using either internally cooled-wet (ICW) electrodes in SB mode (SB-RFA, n = 36) or SC electrodes in SM mode (SM-RFA, n = 38). Technical parameters including the number of ablations, ablation time, volume, energy delivery, and complications were evaluated. Thereafter, 1-year and 2-year local tumor progression (LTP) free survival rates were compared between the two groups using the Kaplan-Meier method.

RESULTS

In the SB-RFA group, less number of ablations were required (1.72±0.70 vs. 2.31±1.37, P = 0.039), the ablation time was shorter (10.9±3.9 vs.14.3±5.0 min, p = 0.004), and energy delivery was smaller (13.1±6.3 vs.23.4±12.8 kcal, p<0.001) compared to SM-RFA. Ablation volume was not significantly different between SB-RFA and SM-RFA groups (61.8±24.3 vs.54.9±23.7 cm3, p = 0.229). Technical failure occurred in one patient in the SM-RFA group, and major complications occurred in one patient in each group. The 1-year and 2-year LTP free survival rates were 93.9% and 84.3% in the SB-RFA group and 94.4% and 88.4% in the SM-RFA group (p = 0.687).

CONCLUSION

Both SB-RFA using ICW electrodes and SM-RFA using SC electrodes provided comparable LTP free survival rates although SB-RFA required less ablations and shorter ablation time.

Image-guided tumor ablation: standardization of terminology and reporting criteria--a 10-year update

Image-guided tumor ablation has become a well-established hallmark of local cancer therapy. The breadth of options available in this growing field increases the need for standardization of terminology and reporting criteria to facilitate effective communication of ideas and appropriate comparison among treatments that use different technologies, such as chemical (eg, ethanol or acetic acid) ablation, thermal therapies (eg, radiofrequency, laser, microwave, focused ultrasound, and cryoablation) and newer ablative modalities such as irreversible electroporation. This updated consensus document provides a framework that will facilitate the clearest communication among investigators regarding ablative technologies. An appropriate vehicle is proposed for reporting the various aspects of image-guided ablation therapy including classification of therapies, procedure terms, descriptors of imaging guidance, and terminology for imaging and pathologic findings. Methods are addressed for standardizing reporting of technique, follow-up, complications, and clinical results. As noted in the original document from 2003, adherence to the recommendations will improve the precision of communications in this field, leading to more accurate comparison of technologies and results, and ultimately to improved patient outcomes.

Image-guided tumor ablation: standardization of terminology and reporting criteria--a 10-year update

Image-guided tumor ablation has become a well-established hallmark of local cancer therapy. The breadth of options available in this growing field increases the need for standardization of terminology and reporting criteria to facilitate effective communication of ideas and appropriate comparison among treatments that use different technologies, such as chemical (eg, ethanol or acetic acid) ablation, thermal therapies (eg, radiofrequency, laser, microwave, focused ultrasound, and cryoablation) and newer ablative modalities such as irreversible electroporation. This updated consensus document provides a framework that will facilitate the clearest communication among investigators regarding ablative technologies. An appropriate vehicle is proposed for reporting the various aspects of image-guided ablation therapy including classification of therapies, procedure terms, descriptors of imaging guidance, and terminology for imaging and pathologic findings. Methods are addressed for standardizing reporting of technique, follow-up, complications, and clinical results. As noted in the original document from 2003, adherence to the recommendations will improve the precision of communications in this field, leading to more accurate comparison of technologies and results, and ultimately to improved patient outcomes. Online supplemental material is available for this article .

Comparison of internally cooled wet electrode and hepatic vascular inflow occlusion method for hepatic radiofrequency ablation

Background/Aims

Various strategies to expand the ablation zone have been attempted using hepatic radiofrequency ablation (RFA). The optimal strategy, however, is unknown. We compared hepatic RFA with an internally cooled wet (ICW) electrode and vascular inflow occlusion.

Methods

Eight dogs were assigned to one of three groups: only RFA using an internally cooled electrode (group A), RFA using an ICW electrode (group B), and RFA using an internally cooled electrode with the Pringle maneuver (group C). The ablation zone diameters were measured on the gross specimens, and the volume of the ablation zone was calculated.

Results

The ablation zone volume was greatest in group B (1.82±1.23 cm³), followed by group C (1.22±0.47 cm³), and then group A (0.48±0.33 cm³). The volumes for group B were significantly larger than the volumes for group A (p=0.030). There was no significant difference in the volumes between groups A and C (p=0.079) and between groups B and C (p=0.827).

Conclusions

Both the usage of an ICW electrode and hepatic vascular occlusion effectively expanded the ablation zone. The use of an ICW electrode induced a larger ablation zone with easy handling compared with using hepatic vascular occlusion, although this difference was not statistically significant.

Radiofrequency ablation combined with transcatheter arterial embolisation in rabbit liver: investigation of the ablation zone according to the time interval between the two therapies

OBJECTIVES

This study was designed to evaluate the extent of the radiofrequency ablation zone in relation to the time interval between transcatheter arterial embolisation (TAE) and radiofrequency ablation (RFA) and, ultimately, to determine the optimal strategy of combining these two therapies for hepatocellular carcinoma.

METHODS

15 rabbits were evenly divided into three groups: Group A was treated with RFA alone; Group B was treated with TAE immediately followed by RFA; and Group C was treated with TAE followed by RFA 5 days later. All animals underwent perfusion CT (PCT) scans immediately after RFA. Serum liver transaminases were measured to evaluate acute liver damage. Animals were euthanised for pathological analysis of ablated tissues 10 days after RFA. Non-parametric analyses were conducted to compare PCT indices, the RFA zone and liver transaminase levels among the three experimental groups.

RESULTS

Group B showed a significantly larger ablation zone than the other two groups. Arterial liver perfusion and hepatic perfusion index represented well the perfusion decrease after TAE on PCT. Although Group B showed the most elevated liver transaminase levels at 1 day post RFA, the enzymes decreased to levels that were not different from the other groups at 10 days post-RFA.

CONCLUSIONS

When combined TAE and RFA therapy is considered, TAE should be followed by RFA as quickly as possible, as it can be performed safely without serious hepatic deterioration, despite the short interval between the two procedures.

Percutaneous radiofrequency ablation using internally cooled wet electrodes for the treatment of hepatocellular carcinoma

OBJECTIVE

The objective of our study was to evaluate the efficacy and safety of percutaneous radiofrequency ablation (RFA) using internally cooled wet electrodes in patients with hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

From March 2008 to October 2010, 122 patients with 129 HCCs (mean size, 2.2 ± 0.6 [SD] cm; range, 0.7-4 cm) were treated with RFA using internally cooled wet electrodes. Primary technical effectiveness, the frequency of major complications, and local tumor progression rates were evaluated.

RESULTS

Two patients (2%) had major complications (liver abscess, significant pleural effusion) after RFA. When evaluated 1 month after RFA, the primary technical effectiveness rate was 99%. The 1- and 2-year local tumor progression rates were 8% and 12%, respectively. Additionally, there was no difference in effectiveness and complication rates between patients with subcapsular HCC and those with nonsubcapsular HCC.

CONCLUSION

Percutaneous RFA using internally cooled wet electrodes is safe and provides successful local tumor control in patients with HCC. The safety and effectiveness of RFA using internally cooled wet electrodes are comparable to those reported in the literature using conventional RFA electrodes and are similar for nonsubcapsular and subcapsular tumors.

A comparison of US-guided percutaneous radiofrequency ablation of medium-sized hepatocellular carcinoma with a cluster electrode or a single electrode with a multiple overlapping ablation technique

PURPOSE

To compare ablation zone, local therapeutic efficacy, and complications of ultrasound (US)-guided percutaneous radiofrequency (RF) ablation of medium-sized hepatocellular carcinomas (HCCs) with a cluster electrode versus a single electrode with multiple overlapping ablations.

MATERIALS AND METHODS

From February 2005 to January 2009, a total of 79 consecutive patients (57 men, 22 women; mean age, 58.6 y) with 79 HCCs (range, 2.5-4.0 cm) underwent percutaneous RF ablation with a cluster electrode (n = 37) or a single electrode with multiple overlapping ablations (n = 42). These methods were compared in terms of ablation zone size on immediate follow-up computed tomography and the rates of technique effectiveness and cumulative local tumor progression on further follow-up (range, 12.0-46.2 mo; median, 24.3 mo).

RESULTS

Baseline characteristics did not differ between groups. The ablation zone in the cluster group was significantly smaller in the longitudinal dimension (43.7 mm ± 4.8 vs 46.5 mm ± 5.9; P = .03), but greater in the short axial dimension (30.7 mm ± 3.9 vs 27.3 mm ± 5.5; P = .03), compared with that in the overlapping ablation group. Technique effectiveness rates in the cluster and overlap groups were 100% and 92.9% (39 of 42), respectively (P = .24). The cumulative local tumor progression rate was significantly lower in the cluster group than in the overlapping group (1- and 3- year follow-up: 8.1 and 18.8% vs 23.8 and 42.2%, P = .04). Complications were more frequent in the cluster group than in the overlapping group (27.0% vs 7.1%; P = .03).

CONCLUSIONS

In US-guided percutaneous RF ablation of medium-sized HCCs, the cluster electrode showed better local therapeutic efficacy than the single electrode with multiple overlapping ablations, probably because of the favorable shape of the ablation zone; however, complications occurred more frequently.

Radiofrequency ablation using a new type of internally cooled electrode with an adjustable active tip: an experimental study in ex vivo bovine and in vivo porcine livers

PURPOSE

The aims of this study were to evaluate the performance of radiofrequency (RF) ablation using a new type of internally cooled RF electrode with an adjustable active tip in an ex vivo bovine liver model and to determine if adjustment of the active tip length makes a significant difference in the size of ablation zone in an in vivo porcine liver model.

MATERIALS AND METHODS

We performed ex vivo experiments by producing 100 RF ablation zones in 40 extracted bovine livers using a new type of RF electrode that had an adjustable active tip (adjustable electrode) (n = 50) and a conventional internally cooled electrode (conventional electrode) (n = 50). We also performed an in vivo study with the induction of 30 RF ablation zones in ten living porcine livers using the adjustable electrode with 2 cm (n = 15) and 3 cm (n = 15) active tip adjustments. The size (three perpendicular diameters), volume and ratio of the two axes of the ablation zone were macroscopically evaluated and were compared.

RESULTS

For the ex vivo study using a 2 cm and 3 cm active tip, there was no significant difference in ablation performance between the use of conventional and adjustable electrodes. For the use of the conventional and adjustable electrodes with 2 cm active tip, respectively, the volume was 10.75 ± 3.43 cm(3) versus 10.64 ± 3.25 cm(3) and the ratio of the two axes was 1.24 ± 0.16 versus 1.30 ± 0.17; p > 0.05. For the use of the conventional and adjustable electrodes with 3 cm active tip, respectively, the volume was 21.17 ± 4.09 cm(3) versus 21.48 ± 3.51 cm(3) and the ratio of the two axes was 1.28 ± 0.12 versus 1.28 ± 0.07; p > 0.05. For the in vivo study using the adjustable electrode, the ablation volume with the 2 cm adjustment was significantly smaller as compared to the 3 cm adjustment (5.29 ± 2.22 cm(3) versus 13.44 ± 4.25 cm(3); p < 0.05) with no statistical difference for the ratio of the two axes (1.44 ± 0.22 versus 1.49 ± 0.24; p > 0.05).

CONCLUSION

Using a new type of internally cooled RF electrode, we could induce different volumes of the RF ablation zone by means of adjusting the length of the exposed active tip, where performance was similar to the use of a conventional internally cooled RF electrode.

Radiofrequency ablation of primary and metastatic lung cancers

Radiofrequency ablation is an accepted method of therapy for unresectable liver cancer. Most recently, interest in using this technology for treatment of primary and metastatic lung tumors has increased. Early animal studies have led to numerous human trials that suggest that radiofrequency ablation can play a major role in treatment of both early-stage primary lung cancer and metastatic lesions. Technical aspects of this therapy as well as areas of further research are discussed.

Drug-eluting polymer implants in cancer therapy

BACKGROUND

Drug-eluting polymer implants present a compelling parenteral route of administration for cancer chemotherapy. With potential for minimally invasive, image-guided placement and highly localized drug release, these delivery systems are playing an increasingly important role in cancer management. This is particularly true as the use of labile proteins and other bioactive molecules is likely to increase in the upcoming years.

OBJECTIVE

In this review, we present the current trends in the application of Pre-formed and in situ-forming systems as drug-eluting implants for cancer chemotherapy.

METHODS

We outline the clinically available options as well as up-and-coming technologies and their advantages and challenges. We also describe ongoing related innovations with image-guided drug delivery, mathematical modeling of implanted delivery systems and implanted drug delivery in combination with other therapies.

RESULTS/CONCLUSION

Whether used alone or combined with other minimally invasive procedures, drug-eluting polymeric implants will play a significant role in the future of cancer management.