Comparison of percutaneous 915 MHz microwave ablation and 2450 MHz microwave ablation in large hepatocellular carcinoma

Microwave ablation eustachian tuboplasty: a preliminary investigation with long-term follow-up

Objectives

This study was performed to evaluate the efficacy of microwave ablation (MWA) eustachian tuboplasty for the treatment of patients with retracted tympanic membrane (TM) due to eustachian tube dysfunction (ETD).

Methods

This was a prospective study of 20 patients with ETD (middle ear atelectasis) who underwent MWA eustachian tuboplasty. Outcomes included the ability to perform a Valsalva maneuver, audiometry results, tympanometry results, ETD Questionnaire (ETDQ-7) score, and TM status.

Results

Eighteen patients (18 ears) were included in this study. There were statistically and clinically significant improvements in the mean ETDQ-7 score at 6 months postoperatively (change in mean score of 16.7 ± 3.6, P < 0.001) and at 30 months postoperatively (change in mean score of 18.9 ± 2.9, P < 0.001).

Type A tympanogram was obtained in 27.8% of patients (5/18) at 6 months postoperatively, and in 77.7% at 30 months postoperatively. A Valsalva maneuver was possible in 72.2% of patients at 6 months postoperatively and in 88.9% of patients at 30 months postoperatively. In addition, the ears of 13 patients (72.2%) showed both normal tympanograms and TM at 30 months postoperatively. Interestingly, 38.5% of patients (5/13) exhibited complete sclerosis of the pars tensa. None of the patients experienced severe MWA-related complications during follow-up.

Conclusions

MWA eustachian tuboplasty is a feasible alternative to conventional tuboplasty, and can improve subjective and objective outcomes in patients with ETD for up to 30 months following treatment. In addition, this study showed that the extent of sclerotic plaque increased over time, whereas the extents of atrophy and tensa retraction decreased following tuboplasty in most patients.

Graphical abstract

Microwave ablation for the removal of pharyngeal benign lesions: A prospective pilot case series

OBJECTIVE

We evaluated microwave ablation (MWA) for treatment of isolated pharyngeal benign lesions, in terms of technical feasibility, efficacy, and safety.

METHODS

The patients with pharyngeal benign lesions were treated with endoscopic MWA with a 2450-MHz single cooled-shaft microwave antenna and sent for histological examination. Postoperative pain intensity was measured via visual analogue scale (VAS) on the 12th hour and the third postoperative days.

RESULTS

Of the 137 patients with pharyngeal benign lesions who met the inclusion criteria. The most commonly involved site was the uvula (n = 66, 48.2%), followed by the lateral pharyngeal wall (n = 37, 27.0%), the nasopharyngeal posterior wall (n = 23, 16.8%) and the soft palate (n = 11, 8.0%). All of the procedures were completed using local anesthesia and were well-tolerated by the patients. The ablation time was 5-10 min, with an average duration of 6.3 ± 1.8 min. The most common pathology was papilloma (n = 96, 70.1%), followed by nasopharyngeal cysts (n = 21, 15.3%), polyp (n = 10, 7.3%), epidermoid cysts (n = 8, 5.8%) and Thornwaldt cysts (n = 2, 1.5%). The mean VAS pain score was 2.36 ± 1.08 on postoperative 12th hour and 1.21 ± 0.54 on postoperative third day. At the 6-month follow-up examination, there were no severe complications, such as recurrence, bleeding, or synechiae of the nasal cavity, eustachian tube injury, in any of the patients.

CONCLUSIONS

The MWA for the treatment of isolated pharyngeal benign lesion is feasible and alternative to conventional surgical methods, it allows excision of the lesion while providing hemostasis, involves only a short ablation time and has a very low risk of complications. Most of our patients well-tolerate the procedure, which may be performed under local anesthesia in the outpatient setting.

Double Slot Antenna for Microwave Thermal Ablation to Treat Bone Tumors: Modeling and Experimental Evaluation

According to statistics of the American Cancer Society, the number of young people diagnosed with bone tumors is growing. Surgery and radiotherapy are the common treatments, however they have several side effects which affect the patient’s life. Therefore, a cheaper and less side-effect therapy called thermal ablation has been explored. The goal of this paper is to measure the therapeutic temperatures and the viability of a double slot antenna designed to treat bone tissue by microwave ablation. The antenna (at an operating frequency of 2.45 GHz) was designed, modeled, constructed, and experimentally evaluated. The finite element method was used to predict the antenna performance by means of 2D axisymmetric models. The modeling parameters were used to build the antenna. The experimental evaluation shows that the antenna behavior is repeatable and the standing wave ratio (SWR) was around 1.5–1.8. Temperatures around 60–100 °C were achieved over the bone tissue. The antenna insertion modifies the antenna performance. An insertion lower than 3.5 cm is not recommended because the convection effects modified the tissue temperature. The thermal patterns showed a heat focus near to the slots, which makes it possible for use in the treatment of small tumors.

Transcatheter arterial chemoembolization combined with simultaneous DynaCT-guided microwave ablation in the treatment of small hepatocellular carcinoma

PURPOSE

To evaluate the method and effectiveness of transcatheter arterial chemoembolization (TACE) combined with simultaneous DynaCT-guided Microwave ablation (MWA) for the treatment of small hepatocellular carcinoma (SHCC).

MATERIALS AND METHODS

From June 2015 to May 2017, a total of 28 consecutive patients with SHCC received single treatment of TACE and 23 subjects received a combination treatment of TACE with simultaneous DynaCT-guided MWA. Following 1 month of treatment, the tumor response was assessed using the mRECIST criteria and the outcomes were analyzed including intervention-associated complications, changes in liver function, imaging response, and progression-free survival (PFS).

RESULTS

The technical success rate was 100%. The rates of CR (65%) in the combined TACE and MWA group were higher than those of the TACE group (46%). The rate of common adverse events, such as liver abscess, spontaneous bacterial peritonitis and liver dysfunction, in the combined TACE and MWA group (56%) was comparable to the corresponding rate of the TACE group (P > 0.411). The median and mean PFS of the TACE group were significantly lower than those of the combined TACE and MWA group (19.00 months vs. 29.00 months, 21.076 months vs. 24.693 months, p = 0.019, log-rank test).

CONCLUSION

Stereotactic DynaCT-guided MWA is a safe and effective method for the treatment of SHCC, which usually provides an effective tumor puncture path, notably for lesions that cannot be detected following TACE. Overall, the data suggested that this treatment method could improve the clinical outcome of patients with SHCC.

Randomized Comparative Study of Microwave Ablation and Electrocautery for Control of Recurrent Epistaxis

OBJECTIVE

To compare the outcomes of adult patients with recurrent epistaxis treated intraoperatively with either bipolar electrocautery or microwave ablation (MWA).

STUDY DESIGN

Prospective randomized control study.

MATERIALS AND METHODS

One hundred ten patients with idiopathic recurrent epistaxis who met the inclusion criteria were randomly assigned into MWA group and bipolar electrocautery group. Primary outcomes were the proportion of patients in each group whose bleeding had stopped within 24 hours after treatment and time to achieve successful hemostasis. Secondary outcomes were the rebleeding rate after 3 days, 1 and 12 weeks, and 6 months and complications.

RESULTS

Successful immediate arrest of epistaxis was achieved in all patients. The times to achieve successful hemostasis were 2.13 ± 1.04 minutes in the MWA group and 6.60 ± 2.68 minutes in the bipolar electrocautery group (P = .000). The rates of recurrent bleeding were similar in patients treated with the different approaches (P = .231). However, secondary crusting was observed endoscopically in 59 patients in the bipolar electrocautery group, while pseudomembrane of the ablation zone was seen in 19 (36.5%) patients in the MWA group. Nevertheless, there were no severe postoperative complications, including septal perforation and orbit and brain complications, in either group at the 6-month follow-up.

CONCLUSION

Bipolar electrocautery and MWA had similar outcomes for the treatment of adult patients with recurrent epistaxis. However, MWA resulted in rapid hemostasis with less local nasal pain and less crust. Thus, MWA could be a favorable treatment option for patients with idiopathic recurrent epistaxis.

Microwave Ablation for the Removal of Benign Lesion of Nasal Cavity: "How I Do It"

Background

Isolated benign lesions of the nasal cavity are commonly seen in the rhinology clinic; their treatment using various therapies has been explored in several studies.

Methods

In this retrospective study, isolated lesions of the nasal cavity were removed from 47 patients using microwave ablation (MWA) with a 2450-MHz cooled MWA antenna and sent for histological examination.

Results

The most commonly involved site was the nasal septum (n = 21, 44.7%), followed by the inferior turbinate (n = 12, 25.5%), bulla ethmoidalis (n = 9, 19.1%), and uncinate process (n = 5, 10.6%). The most common pathology was hemangioma (n = 36, 76.6%), followed by nasal polyp (n = 9, 19.1%) and squamous papilloma (n = 2, 4.3%). All lesions were removed endoscopically using MWA in patients administered local anesthesia. The total duration of ablation was 5 to 10 minutes, with an average duration of 7.3 ± 2.6 minutes. Follow-up at 6 months revealed no severe complications, including no cases of recurrent epistaxis, septal perforation, or synechiae of the nasal cavity.

Conclusions

The advantages of MWA are its short ablation time and minimal complications. This was demonstrated in our study in which a single session of MWA was sufficient to excise the isolated lesion while providing hemostasis. Most of the patients well tolerated the procedure, which could be performed using local anesthesia in the outpatient setting.

Microwave ablation compared with radiofrequency ablation for treatment of hepatocellular carcinoma and liver metastases: a systematic review and meta-analysis

Purpose

Percutaneous ablation techniques, including microwave ablation (MWA) and radiofrequency ablation (RFA), have become important minimally invasive treatment options for liver cancer. This systematic review compared MWA with RFA for treatment of liver cancer.

Methods

The systematic review and meta-analysis followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A systematic search of MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials was conducted for randomized and observational studies published from 2006 onwards. A random-effects model was used for meta-analyses and local tumor progression (LTP), technique efficacy, overall survival (OS), disease-free survival (DFS), intrahepatic de novo lesions (IDL), extrahepatic metastases (EHM), length of stay (LOS), and complications were analyzed. Subgroup and sensitivity analyses were also conducted.

Results

Of 1379 studies identified, 28 randomized and observational studies met inclusion criteria. The main analysis demonstrated that LTP was significantly reduced by 30% with MWA versus RFA (RR=0.70; P=0.02) (all studies) and by 45% with MWA versus RFA (RR=0.55; P=0.007) (randomized studies only). There were no significant differences between MWA and RFA for other efficacy and safety outcomes. Higher frequency (2450 MHz) and larger tumor size (≥2.5 cm) are amongst variables that may be associated with improved outcomes for MWA. Sensitivity analyses were generally congruent with the main results.

Conclusion

MWA is at least as safe and effective as RFA for treating liver cancer and demonstrated significantly reduced LTP rates. Future studies should assess time and costs associated with these two treatment modalities.

Comparison of parallel and crossed placement of antennas in microwave ablation of 3-5 cm hepatocellular carcinoma

PURPOSE

To evaluate the effects of ablation strategies on local tumor progression (LTP) after microwave ablation (MWA) of hepatocellular carcinomas (HCCs) measuring 3-5 cm.

MATERIALS AND METHODS

Between December 2011 and May 2017, 71 HCC patients with 71 nodules treated by ultrasound(US)-guided percutaneous MWA were divided into parallel (group A) and crossed (group B) antenna placement groups. All patients underwent MWA using two antennas with four insertions. LTP and overall survival (OS) rates were compared between the two groups.

RESULTS

The median follow-up time was 16.8 months. There was no significant difference in the complete ablation rate and treatment sessions between the two groups. LTP was diagnosed in 8 of 48 nodules (16.7%) in group A and 1 of 23 nodules (4.3%) in group B, with no significant difference between two groups (P = 0.115). The 1-, 2-, and 3-year OS rates were 88.5%, 79%, and 71.8% in group A and 93.8%, 87.5%, and 87.5% in group B, respectively (P = 0.236). Multivariate analysis showed that the tumor diameter (P = 0.017), the distance between the antennas (P = 0.032), and the total emission time (P = 0.015) were associated with LTP.

CONCLUSIONS

There were trends with lower LTP and improved OS in group B, despite the lack of statistically significant differences between the two strategies at a level of P < 0.05. The increase of distance between antennas and total emission time will facilitate reductions in LTP rate.

A comparison between 915 MHz and 2450 MHz microwave ablation systems for the treatment of small diameter lung metastases

PURPOSE

We aimed to retrospectively compare the local tumor control rates between low frequency (LF) and high frequency (HF) microwave ablation devices in the treatment of <3 cm lung metastases.

METHODS

A total of 36 patients (55 tumors) were treated with the LF system (915 MHz) and 30 patients (39 tumors) were treated with the HF system (2450 MHz) between January 2011 and March 2016. Computed tomography (CT) scans performed prior to and 24 hours after the ablation were used to measure the size of the ablation zone and to calculate the ablation margin. The subsequent CTs were used to detect local tumor progression. Possible predictive factors for local progression were analyzed. All patients had a minimum follow-up of 3 months with a median of 13.8 months for the LF group and 11.7 months for the HF group.

RESULTS

The ablation margin (P = 0.015), blood vessel proximity (P = 0.006), and colorectal origin (P = 0.029) were significantly associated with the local progression rate. The local progression rates were 36.3% for LF ablations and 12.8% for HF ablations. The 6, 12, and 18 months local progression-free survival rates were 79%, 65.2% and 53% for the LF group and 97.1%, 93.7%, and 58.4% for the HF group, with a significant difference between the survival curves (P = 0.048).

CONCLUSION

HF ablations resulted in larger ablation margins with fewer local progression compared with LF ablations.

The relationship between applied energy and ablation zone volume in patients with hepatocellular carcinoma and colorectal liver metastasis

Objectives

To study the ratio of ablation zone volume to applied energy in computed tomography (CT)-guided radiofrequency ablation (RFA) and microwave ablation (MWA) in patients with hepatocellular carcinoma (HCC) in a cirrhotic liver and in patients with colorectal liver metastasis (CRLM).

Methods

In total, 90 liver tumors, 45 HCCs in a cirrhotic liver and 45 CRLMs were treated with RFA or with one of two MWA devices (MWA_A and MWA_B), resulting in 15 procedures for each tumor type, per device. Device settings were recorded and the applied energy was calculated. Ablation volumes were segmented on the contrast-enhanced CT scans obtained 1 week after the procedure. The ratio of ablation zone volume in milliliters to applied energy in kilojoules was determined for each procedure and compared between HCC (R_HCC) and CRLM (R_CRLM), stratified according to ablation device.

Results

With RFA, R_HCC and R_CRLM were 0.22 mL/kJ (0.14–0.45 mL/kJ) and 0.15 mL/kJ (0.14–0.22 mL/kJ; p = 0.110), respectively. With MWA_A, R_HCC was 0.81 (0.61–1.07 mL/kJ) and R_CRLM was 0.43 (0.35–0.61 mL/kJ; p = 0.001). With MWA_B, R_HCC was 0.67 (0.41–0.85 mL/kJ) and R_CRLM was 0.43 (0.35–0.61 mL/kJ; p = 0.040).

Conclusions

With RFA, there was no significant difference in energy deposition ratio between tumor types. With both MWA devices, the ratios were higher for HCCs. Tailoring microwave ablation device protocols to tumor type might prevent incomplete ablations.

Key Points

• HCCs and CRLMs respond differently to microwave ablation

• For MWA, CRLMs required more energy to achieve a similar ablation volume

• Tailoring ablation protocols to tumor type might prevent incomplete ablations

Management of people with intermediate-stage hepatocellular carcinoma: an attempted network meta-analysis

BACKGROUND

There is significant uncertainty in the treatment of intermediate-stage hepatocellular carcinoma which is defined by the Barcelona Clinic Liver Cancer (BCLC) as hepatocellular carcinoma stage B with large, multi-nodular, Child-Pugh status A to B, performance status 0 to 2, and without vascular occlusion or extrahepatic disease.

OBJECTIVES

To assess the comparative benefits and harms of different interventions used in the treatment of intermediate-stage hepatocellular carcinoma (BCLC stage B) through a network meta-analysis and to generate rankings of the available interventions according to their safety and efficacy. However, we found only one comparison. Therefore, we did not perform the network meta-analysis, and we assessed the comparative benefits and harms of different interventions versus each other, or versus placebo, sham, or no intervention (supportive treatment only) using standard Cochrane methodology.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, Science Citation Index Expanded, World Health Organization International Clinical Trials Registry Platform, and randomised clinical trials registers to September 2016 to identify randomised clinical trials on hepatocellular carcinoma.

SELECTION CRITERIA

We included only randomised clinical trials, irrespective of language, blinding, or publication status, in participants with intermediate-stage hepatocellular carcinoma, irrespective of the presence of cirrhosis, size, or number of the tumours (provided they met the criteria of intermediate-stage hepatocellular carcinoma), of presence or absence of portal hypertension, of aetiology of hepatocellular carcinoma, and of the future remnant liver volume. We excluded trials which included participants who had previously undergone liver transplantation. We considered any of the various interventions compared with each other or with no active intervention (supportive treatment only). We excluded trials which compared variations of the same intervention: for example, different methods of performing transarterial chemoembolisation.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane. We calculated the hazard ratio (HR) with 95% confidence intervals (CI) using both fixed-effect and random-effects models based on available-participant analysis with Review Manager. We assessed risk of bias according to Cochrane, controlled risk of random errors with Trial Sequential Analysis using Stata, and assessed the quality of the evidence using GRADE.

MAIN RESULTS

Three randomised clinical trials, including 430 participants, met the inclusion criteria for this review; however, data from two trials with 412 participants could be included in only one primary outcome (i.e. mortality). All three trials were at high risk of bias. All three trials included supportive care as cointervention. The comparisons included in the two trials reporting on mortality were: systemic chemotherapy with sorafenib versus no active intervention; and transarterial chemoembolisation plus systemic chemotherapy with sorafenib versus transarterial chemoembolisation alone. The trials did not report the duration of follow-up; however, it appeared that the participants were followed up for a period of about 18 to 30 months. The majority of the participants in the trials had cirrhotic livers. The trials included participants with intermediate-stage hepatocellular carcinoma arising from viral and non-viral aetiologies. The trials did not report the portal hypertension status of the participants. The mortality was 50% to 70% over a median follow-up period of 18 to 30 months. There was no evidence of difference in mortality at maximal follow-up between systemic chemotherapy versus no chemotherapy (hazard ratio 0.85, 95% CI 0.60 to 1.18; participants = 412; studies = 2; I2 = 0%; very low quality evidence). A subgroup analysis performed by stratifying the analysis by the presence or absence of transarterial chemoembolisation as cointervention did not alter the results. None of the trials reported on serious adverse events other than mortality, health-related quality of life, recurrence of hepatocellular carcinoma, or length of hospital stay. One of the trials providing data was funded by the pharmaceutical industry, the other did not report the source of funding, and the trial with no data for the review was also funded by the pharmaceutical industry. We found two ongoing trials.

AUTHORS' CONCLUSIONS

Currently, there is no evidence from randomised clinical trials that people with intermediate-stage hepatocellular carcinoma would benefit from systemic chemotherapy with sorafenib either alone or when transarterial chemoembolisation was used as a cointervention (very low quality evidence). We need high-quality randomised clinical trials designed to measure differences in clinically important outcomes (e.g. all-cause mortality or health-related quality of life).

Status and advancement of microwave ablation in China

Tumour ablation is defined as the direct application of chemical or thermal therapy to eradicate or substantially destroy a tumour. Currently, minimally invasive ablation techniques are available for the local destruction of focal tumours in multiple organ sites. Microwave ablation (MWA) is premised on the biological response of solid tumours to tissue hyperthermia, and it is a relatively low-risk procedure. Due to several advantages of MWA, including higher thermal efficiency, higher capability for coagulating blood vessels, faster ablation time and the simultaneous application of multiple antennae, MWA could be a promising minimally invasive ablation technique for the treatment of solid tumours. Therefore, the use of MWA has developed rapidly in China during the last decade. Many successful studies have been performed, and widespread use has been achieved for multiple types of tumours in China, especially for liver cancer. This review will describe the state-of-the-art of MWA in China, including the development of MWA equipment and its application in the treatment of multiple types of tumours.

Percutaneous microwave ablation for benign focal liver lesions: Initial clinical results

Benign focal liver lesions (BFLLs) have become a common disease diagnosed in the clinical setting following the advancement of imaging techniques. The aim of the present study was to evaluate the safety and clinical outcomes of percutaneous microwave (MW) ablation, guided by ultrasound (US), for the treatment of BFLLs. Between May 2005 and January 2011, 44 BFLLs (mean maximum diameter, 33.9±13.1 mm) in 37 patients (23 women and 14 men) were treated by US-guided percutaneous MW ablation with cooled-shaft antennae. The pathological diagnosis of a BFLL was confirmed in 91.9% (34/37) of patients using a US-guided core needle biopsy prior to ablation. The BFLLs in the other 3 cases were diagnosed by typical presentations on contrast-enhanced imaging, as the patients refused to undergo biopsies. Five inclusion criteria, including indeterminate diagnoses of nodules on contrast-enhanced imaging prior to pathological verification, were recommended. The median follow-up period was 27.0 months (range, 6-73 months). The mean MW ablation energy and time were 55.0±41.6 kJ (range, 13.5-207 kJ) and 1,039.9±706.2 sec (range, 270-3,450 sec) per lesion, respectively. In total, 40 nodules (90.9%) were completely ablated, and no evidence of recurrence was demonstrated on contrast-enhanced imaging follow-up. The other 4 nodules (9.1%) were partially ablated due to the proximity of adjacent vital organs. Minor complications without sequelae included local pain and transient hemoglobinuria and no major complications occurred in peri-ablation. Overall, US-guided percutaneous MW ablation is a safe, effective and minimally invasive therapy for BFLLs in selected patients who are non-surgical candidates.

CT-guided percutaneous microwave ablation of pulmonary malignant tumors

BACKGROUND

Microwave ablation (MWA) of lung tumors is a new approach for local tumor control. The purpose of this retrospective study was to evaluate the preliminary results of safety and efficacy of MWA with a dynamic frequency range (902-928 MHz) and power (10-32 W) for local tumor control of thoracic malignancies.

METHODS

From December 1, 2013 to February 1, 2016, there were total 32 lung tumors among 15 patients (7 men, 8 women, age range 43-82 years, mean 57.8±11.1 years of age) receiving MWA of thoracic neoplasms, including lung adenocarcinoma (n=5), metastatic colorectal cancer (n=7), invasive thymoma (n=1), metastatic uterine leiomyosarcoma (n=1), and metastatic ampullary carcinoma (n=1). Mean tumor size was 13.5 mm (range, 3.0-32.0 mm). The mean sequential ablation during each MWA was 2.3±1.1 times (range, 1-5 times). The outcomes of ablation were evaluated by follow-up computed tomography (CT) scans and the complications were assessed by medical records and CT scan after ablation.

RESULTS

The mean follow-up interval of each tumor was 446.8 days (range, 196-902 days). Local tumor recurrence was found in 5 of the 32 tumors resulting in a local control rate 84.4%. No MWA-related mortality was noted. After MWA, the incidence of pneumothorax was 37.5% (12/32). Only one patient with pneumothorax required air evacuation. Third-degree skin burn adjacent to the entry site occurred in one patient and required debridement and closure with flap.

CONCLUSIONS

After appropriate patient selection, MWA with a dynamic frequency range (902-928 MHz) and power (10-32 W) is an effective and safe procedure for local tumor control of recurrent and metastatic lung tumors.

A Review of Therapeutic Ablation Modalities

Understanding basic science and technical aspects is essential for scientists and engineers to develop and enhance ablative modalities, and for clinicians to effectively apply therapeutic ablative techniques. An overview of ablative modalities, anatomical locations, and indications for which ablations are performed is presented. Specifically, basic concepts, parameter selection, and underlying biophysics of tissue injury of five currently used therapeutic ablative modalities are reviewed: radiofrequency ablation (RFA), cryoablation (CRA), microwave ablation (MWA), high-intensity focused ultrasound (HIFU), and chemical ablation (CHA) (ablative agents: acetic acid, ethanol, hypertonic sodium chloride, and urea). Each ablative modality could be refined for expanding applications, either independently or in combination, for future therapeutic use.

Evaluation of percutaneous microwave coagulation therapy for hepatic artery injury

Objectives

To evaluate the in vivo efficacy of 915 MHz percutaneous coagulation in the treatment of hepatic artery injury.

Methods

After inducing hepatic artery injury, 8 dogs in each group underwent 915 MHz microwave percutaneous coagulation therapy and 8 dogs were injected with batroxobin and α-cyanoacrylate.

Results

The hemostatic effects of 915 MHz microwave were better than drug injection, and the amount of bleeding was significantly lower (p < 0.05). Pathological examination showed that vessel wall necrosis were greater.

Conclusion

Contrast ultrasound guided 915 MHz microwave percutaneous coagulation treatment has potent hemostatic effects in the repair of in vivo hepatic artery injury.

Microwave ablation of ex vivo bovine tissues using a dual slot antenna with a floating metallic sleeve

PURPOSE

To study the efficiency of a dual slot antenna with a floating metallic sleeve on the ablation of different ex vivo bovine tissues.

MATERIALS AND METHODS

COMSOL Multiphysics® version 4.4 (Stockholm, Sweden), which is based on finite element methods (FEM), was used to design and simulate monopole and dual slot with sleeve antennas. Power, specific absorption rate (SAR), temperature and necrosis distributions in the selected tissues were determined using these antennas. Monopole and dual slot with sleeve antennas were designed, simulated, constructed and applied in this study based on a semi-rigid coaxial cable. Ex vivo experiments were performed on liver, lung, muscle and heart of bovine obtained from a public animal slaughter house. The microwave energy was delivered using a 2.45 GHz solid-state microwave generator at 40 W for 3, 5 and 10 min. Aspect ratio, ablation length and ablation diameter were also determined on ablated tissues and compared with simulated results. Student's t-test was used to compare the statistically significant difference between the performance of the two antennas.

RESULTS

The dual slot antenna with sleeve produces localised microwave energy better than the monopole antenna in all ablated tissues using simulation and experimental validation methods. There were significant differences in ablation diameter and aspect ratio between the sleeve antenna and monopole antenna. Additionally, there were no significant differences between the simulation and experimental results.

CONCLUSIONS

This study demonstrated that the dual slot antenna with sleeve produced larger ablation zones and higher sphericity index in ex vivo bovine tissues with minimal backward heating when compared with the monopole antenna.

Therapeutic efficacy of percutaneous microwave coagulation versus liver resection for single hepatocellular carcinoma ≤3 cm with Child-Pugh A cirrhosis

AIMS

This study aimed to compare the therapeutic efficacy of liver resection (LR) and percutaneous microwave coagulation therapy (PMCT) for single hepatocellular carcinoma ≤3 cm (HCC) in cirrhotic livers.

METHODS

In this study, 190 patients with single HCC ≤3 cm and Child-Pugh A cirrhosis were retrospectively reviewed. Among these patients, 122 patients underwent LR, and 68 patients received PMCT. The therapeutic efficacy and complications were compared between the two procedures.

RESULTS

There was no treatment-related hospital mortality in either group. Major complications were significantly more frequent in the LR group compared to the PMCT group (22.1% vs 5.9%, p = 0.004). The 1-, 3-, and 5-year OS rates for the LR group and PMCT group were 98.4%, 93.6%, 55.2% and 97.1%, 87.7%, 51%, respectively. There was no significant difference in OS rates between the LR group and PMCT group (p = 0.153). The 1-, 3-, and 5-year DFS rates were 96.7%, 70.5% and 43.7%, respectively, in the LR group, which were significantly higher compared to the PMCT group (92.6%, 50.5% and 26.3%, p = 0.006). Subgroup analyses revealed that HCC patients with portal hypertension (PH), OS and DFS were similar between the two groups.

CONCLUSIONS

LR may provide better DFS and lower recurrence rates than PMCT for single HCC ≤3 cm and Child-Pugh A cirrhosis. For HCC patients with PH, PMCT may provide therapeutic effects that are similar to LR.

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.

Microwave ablation of hepatocellular carcinoma

Although surgical resection is still the optimal treatment option for early-stage hepatocellular carcinoma (HCC) in patients with well compensated cirrhosis, thermal ablation techniques provide a valid non-surgical treatment alternative, thanks to their minimal invasiveness, excellent tolerability and safety profile, proven efficacy in local disease control, virtually unlimited repeatability and cost-effectiveness. Different energy sources are currently employed in clinics as physical agents for percutaneous or intra-surgical thermal ablation of HCC nodules. Among them, radiofrequency (RF) currents are the most used, while microwave ablations (MWA) are becoming increasingly popular. Starting from the 90s’, RF ablation (RFA) rapidly became the standard of care in ablation, especially in the treatment of small HCC nodules; however, RFA exhibits substantial performance limitations in the treatment of large lesions and/or tumors located near major heat sinks. MWA, first introduced in the Far Eastern clinical practice in the 80s’, showing promising results but also severe limitations in the controllability of the emitted field and in the high amount of power employed for the ablation of large tumors, resulting in a poor coagulative performance and a relatively high complication rate, nowadays shows better results both in terms of treatment controllability and of overall coagulative performance, thanks to the improvement of technology. In this review we provide an extensive and detailed overview of the key physical and technical aspects of MWA and of the currently available systems, and we want to discuss the most relevant published data on MWA treatments of HCC nodules in regard to clinical results and to the type and rate of complications, both in absolute terms and in comparison with RFA.

High-powered microwave ablation of larger hepatocellular carcinoma: evaluation of recurrence rate and factors related to recurrence

AIM

To evaluate the safety and efficacy of high-powered (80-100 W) percutaneous microwave ablation (MWA) at a frequency of 2450±10 MHz for treating larger hepatocellular carcinoma (HCC) and to predict the risk factors of local recurrence after high-powered MWA.

MATERIALS AND METHODS

The study was approved by the Institutional Review Board, and informed consent was waived because of the retrospective study design. Forty-five patients with a total of 60 lesions received high-power (80-100 W) MWA at a frequency of 2450±10 MHz through a percutaneous approach that was guided by ultrasound. Of the 60 lesions with a maximum tumour measuring 3-8 cm, 46 lesions were 3-5 cm and 14 were 5-8 cm. The complete ablation rates, local recurrence rates, complications, and short-term survival were analysed. Ten possible risk factors for local recurrence were analysed.

RESULTS

The complete ablation rates were 82.61% for the first ablation and 100% for the second ablation for 3-5 cm lesions. The complete ablation rates were 64.29% (82.61% versus 64.29%, p=0.037) for the first ablation and 85.71% (100% versus 85.71%, p=0.055) for the second ablation for 5-8 cm lesions. Local recurrence was observed in 11 out of the 45 (24.44%) successfully treated patients. The 1-year and 2-year survival rates were 95.56% (43/45) and 86.67% (39/45), respectively. No procedure-related mortality was observed and no major bleeding, liver rupture, or liver abscesses occurred. Univariate analysis showed that a positive correlation existed between the number of lesions (p=0.022), proximity to the risk area (p=0.001), pre-ablation alpha-fetoprotein (AFP) levels (p=0.025), hepatitis B virus (HBV)-DNA replication (p=0.027) and local recurrence. Multivariate analysis identified HBV-DNA (p=0.031) and proximity to the risk area (p=0.039) as the independent prognosis factors causing postoperative HCC local recurrence.

CONCLUSION

High-powered MWA of larger hepatocellular carcinomas appears to be a safe and effective treatment. HBV-DNA and proximity to the risk area appear to be independent predictors of local tumour recurrence.

Locoregional therapy of hepatocellular carcinoma

Hepatocellular carcinoma can be treated using minimally invasive, image-guided, catheter-based or percutaneous techniques. Such procedures offer compelling clinical outcomes with a favorable side-effect profile in a population of patients who are poor candidates for surgical or systemic treatment. This article discusses key data regarding the effectiveness of locoregional therapies in treating these patients. Disease-specific treatment is discussed in the context of hepatocellular carcinoma, with additional data discussed in the context of transplantation. As rapid innovation occurs in the realm of oncology, interventional oncology represents a safe, effective alternative that continues to generate impressive data that could potentially change treatment paradigms.

The role of interventional radiology in the management of hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (hcc) is one of the most common causes of cancer-related death worldwide. Overall, liver transplantation and resection are the only available treatments with potential for cure. Various locoregional therapies are widely used to manage patients with advanced hcc or as a bridging therapy for patients with early and intermediate disease. This article reviews and evaluates the role of interventional radiology in the management of such cases by assessing various aspects of each method, such as effect on rates of survival, recurrence, tumour response, and complications.

METHODS

A systemic search of PubMed, medline, Ovid Medline In-Process, and the Cochrane Database of Systematic Reviews retrieved all related scientific papers for review.

RESULTS

Needle core biopsy is a highly sensitive, specific, and accurate method for hcc grading. Portal-vein embolization provides adequate expansion of the future liver remnant, making more patients eligible for resection. In focal or multifocal unresectable early-stage disease, radiofrequency ablation tops all other thermoablative methods. However, microwave ablation is preferred in large tumours and in patients with Child-Pugh B disease. Cryoablation is preferred in recurrent disease and in patients who are poor candidates for anesthesia. Of the various transarterial modalities-transarterial chemoembolization (tace), drug-eluting beads, and transarterial radio-embolization (tare)-tace is the method of choice in Child-Pugh A disease, and tare is the method of choice in hcc cases with portal vein thrombosis.

CONCLUSIONS

The existing data support the importance of a multidisciplinary approach in hcc management. Large randomized controlled studies are needed to provide clear indication guidelines for each method.

Advances in managing hepatocellular carcinoma

Multiple modalities for treatment of hepatocellular carcinoma are available, depending on tumor size and number. Surgical resection remains the gold standard, so long as the residual liver function reserve is sufficient. In patients with advanced cirrhosis, liver transplantation is the preferred option, as these patients may not have adequate hepatic reserve after resection. Salvage liver transplantation has also become an option for a select few patients who recur after surgical resection. Ablative techniques have been used for palliation as well as to either completely destroy the tumor, act as an adjunct to resection, or downstage the tumor to meet Milan criteria such that a patient may be a candidate for liver transplantation. Radiofrequency ablation, microwave ablation, chemoembolization, radioembolization, and irreversible electroporation have all been used in this capacity. Currently, sorafenib is the only US Food and Drug Administration-approved chemotherapeutic for hepatocellular carcinoma. The efficacy of sorafenib, in combination with other agents, transarterial chemoembolization, and surgical resection is currently being investigated. Sunitinib and brivanib, tyrosine kinase inhibitors, have failed as potential first- or second-line options for chemotherapy. Bevacizumab in combination with erlotinib is also currently being studied. Final analysis for ramucirumab and axitinib are pending. Tivantinib, a selective mesenchymal-epithelial transition factor (MET) inhibitor, is also undergoing clinical trials for efficacy in MET-high tumors. This review serves to emphasize the current and new technologies emerging in the treatment of hepatocellular carcinoma.

Microwave ablation for hepatic malignancies: a call for standard reporting and outcomes

BACKGROUND

Clinical standards of reporting microwave ablation outcomes have not been defined with regard to ablation success, 90-day morbidity, local recurrence after ablation, and nonablation hepatic recurrence. We propose recommendations for microwave ablation reporting and quality standards.

METHODS

Literature review of clinical studies focusing on microwave ablation of primary and metastatic hepatic tumors was reported.

RESULTS

Ablation success remains the highest quality reporting standard with variations in nomenclature, but with a universal agreement of complete destruction of the target lesion within 1 month after initial microwave ablation. Local recurrence after ablation remains highly variable, with reports as low as 2.2% to as high as 22%; standards lack a common, clearly defined distance from the initial target ablated lesion and the requirement that the target lesion be defined as an ablation success before it can be called a recurrence. Nonablation hepatic recurrence, nonhepatic recurrence, and 90-day morbidity and mortality remain limited in the current literature.

CONCLUSIONS

Standardization of hepatic microwave ablation reporting standards are proposed. Current reporting standards in microwave ablation of hepatic malignancies are suboptimal and lack standardization for comparison across institutions.

Contrast-enhanced sonographically guided percutaneous 915-MHz microwave ablation therapy compared to local hemostatic drug injection in a renal artery injury model

OBJECTIVES

The purpose of this study was to show the contrast-enhanced sonographic features of various levels of renal artery rupture and to validate the therapeutic effects of percutaneous 915-MHz microwave ablation compared to hemostatic drug injection (batroxobin) using an in vivo canine renal artery injury model.

METHODS

Three renal artery hemorrhage models (A, diameter <1 mm, subcapsular artery; B, diameter 1-2 mm, interlobar artery; and C, diameter 2-3 mm, segmental artery) were created in 24 canines for this study. Contrast-enhanced sonography was used to show the bleeding features and guide hemostatic therapies using 915-MHz microwave ablation and local batroxobin injection. Success rates were assessed according to amounts of bleeding, times required for hemostatic action, and volumes of fluid infusion required using pathologic examination as a reference standard.

RESULTS

Contrast-enhanced sonography clearly showed renal artery ruptures with active bleeding at various levels and degrees and was very useful to make diagnoses and guide therapies. The success rate in the microwave treatment group was higher than that in the drug injection group (except group A; P< .05). The time required for hemostasis and the volume of fluid infusion required in the microwave group were notably less than those in the drug injection group (P < .05).

CONCLUSIONS

Contrast-enhanced sonography is a useful imaging method for assessing renal vessel injury and guide interventional therapies. Contrast-enhanced sonographically guided percutaneous 915-MHz microwave ablation is a preferred hemostatic technique for treatment of renal artery injury, with greater effectiveness and less tissue damage compared to local drug injection.

Percutaneous microwave ablation for hepatocellular carcinoma adjacent to large vessels: a long-term follow-up

PURPOSE

To retrospectively evaluate the effectiveness and safety of ultrasound (US)-guided percutaneous microwave ablation (MWA) in the treatment of hepatocellular carcinoma (HCC) adjacent to large vessels.

MATERIALS AND METHODS

From February 2006 to February 2013, 452 patients with 605 HCC nodules were treated with US-guided percutaneous MWA. Into large vessels group (Group L), 139 patients with 163 lesions (diameter, 1.0-7.0 cm; mean, 2.5±1.1 cm) located less than 5mm away from large vessels were enrolled. And 313 patients with 442 lesions (diameter, 1.0-8.0 cm; mean, 2.5±1.2 cm) located more than 5mm away from hepatic surface, large vessels, gallbladder and gastrointestinal tract were included in control group (Group C). During the ablation, the temperature of marginal ablation tissues was monitored and controlled.

RESULTS

The median follow-up time was 24.5 months (range 2.1-87.7 months) in Group L, and 25.7 months (range 1.6-93.9 months) in Group C. Technical effectiveness was achieved in 157 of 163 (96.3%) tumors in Group L and 429 of 442 (97.1%) tumors in Group C, respectively (p>0.05). The 1-, 3- and 5-year local tumor progression rates and the 1-, 3- and 5-year accumulative survival rates in the two groups have no significantly statistical differences. In addition, no immediate or periprocedural major complications, no delayed complication of vessels or bile ducts injury were found in both of the two groups.

CONCLUSIONS

With strict temperature monitoring, US-guided percutaneous MWA is an efficient and safe technology in treating hepatocellular carcinoma adjacent to large vessels.

Radiofrequency ablation for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common causes of cancer-related mortality worldwide. Unfortunately, only 20% of HCC patients are amenable to curative therapy (liver transplantation or surgical resection). Locoregional therapies such as radiofrequency ablation (RFA), percutaneous ethanol injection, microwave coagulation therapy, and transcatheter arterial chemoembolisation play a key role in the management of HCC. The choice of the treatment modality depends on the size of the tumour, tumour location, anatomic considerations and the number of tumours present and liver function. RFA therapy for HCC can be performed safely using a percutaneous, laparoscopic, or an open approach, even in patients with poor functional reserve. Since the introduction of RFA, several randomised controlled trials and non-randomised studies comparing RFA and other therapies for HCC have been conducted. In addition, in the last decade there have been technical advances in RFA therapy for HCC, resulting in significant improvement in the prognosis of HCC patients treated with this modality. In this review, we primarily focus on percutaneous RFA therapy for HCC and refer to current knowledge and future perspectives for this therapy. We also discuss new emerging ablation techniques.

Computational modelling of microwave tumour ablations

Microwave tissue heating is being increasingly utilised in several medical applications, including focal tumour ablation, cardiac ablation, haemostasis and resection assistance. Computational modelling of microwave ablations is a precise and repeatable technique that can assist with microwave system design, treatment planning and procedural analysis. Advances in coupling temperature and water content to electrical and thermal properties, along with tissue contraction, have led to increasingly accurate computational models. Developments in experimental validation have led to broader acceptability and applicability of these newer models. This review will discuss the basic theory, current trends and future direction of computational modelling of microwave ablations.

Comparison of four microwave ablation devices: an experimental study in ex vivo bovine liver

PURPOSE

To compare volume, sphericity, and short-axis diameter of the coagulation zone of four commercially available microwave ablation systems with three technical concepts in an ex vivo setting and to formulate mathematical models to predict these quantities.

MATERIALS AND METHODS

Two high-power systems (systems A and B), a system that enables simultaneous use of three antennas (system C), and a non-perfusion-cooled system that automatically adapts power and frequency (system D) were tested in ex vivo bovine livers (108 ablations). Coagulation volume, sphericity, and mean short-axis diameter were assessed, and mathematical functions were fitted for each system and assessed with the coefficient of determination (R(2)). Analysis of variance and Tukey post hoc tests were used for interdevice comparison after 5 and 10 minutes and after maximum recommended ablation time.

RESULTS

Volume and short-axis diameter were determined by using a mathematical model for every system, with coefficients of determination of 0.75-0.98 and 0.70-0.97, respectively. Correlation for determination of sphericity was lower (R(2) = 0.01-0.68). Mean results with ablation performed according to manufacturer recommendations were as follows: Volume, sphericity, and short-axis diameter were 57.5 cm(3), 0.75, and 43.4 mm, respectively, for system A; 72.3 cm(3), 0.68, and 45.5 mm, respectively, for system B; 17.1 cm(3), 0.58, and 26.8 mm, respectively, for system C (one antenna); 76.5 cm(3), 0.89, and 50.6 mm, respectively, for system C (three antennas); and 56.0 cm(3), 0.64, and 40.9 mm, respectively, for system D. Systems A (mean volume, 52.4 cm(3) ± 4.5 [standard deviation]) and B (39.4 cm(3) ± 1.7) reach large ablation zones with 5-minute ablation.

CONCLUSION

The largest ablation zone is obtained with systems B and C (three antennas) under maximum recommended ablation duration and with system A under short ablation time. The most spherical zone is obtained with system C (three antennas).

Ultrasound-guided microwave ablation for abdominal wall metastatic tumors: a preliminary study

AIM

To evaluate the feasibility, safety and efficacy of ultrasound-guided microwave (MW) ablation for abdominal wall metastatic tumors.

METHODS

From August 2007 to December 2010, a total of 11 patients with 23 abdominal wall nodules (diameter 2.59 cm ± 1.11 cm, range 1.3 cm to 5.0 cm) were treated with MW ablation. One antenna was inserted into the center of tumors less than 1.7 cm, and multiple antennae were inserted simultaneously into tumors 1.7 cm or larger. A 21 gauge thermocouple was inserted near important organs which required protection (such as bowel or gallbladder) for real-time temperature monitoring during MW ablation. Treatment outcome was observed by contrast-enhanced ultrasound and magnetic resonance imaging (MRI) [or computed tomography (CT)] during follow-up.

RESULTS

MW ablation was well tolerated by all patients. Six patients with 11 nodules had 1 thermocouple inserted near important organs for real-time temperature monitoring and the maximum temperature was 56 °C. Major complications included mild pain (54.5%), post-ablation fever (100%) and abdominal wall edema (25%). All 23 tumors (100%) in this group were completely ablated, and no residual tumor or local recurrence was observed at a median follow-up of 13 mo (range 1 to 32 mo). The ablation zone was well defined on contrast-enhanced imaging (contrast-enhanced CT, MRI and/or contrast-enhanced ultrasound) and gradually shrank with time.

CONCLUSION

Ultrasound-guided MW ablation may be a feasible, safe and effective treatment for abdominal wall metastatic tumors in selected patients.

Ultrasound-guided percutaneous microwave ablation of benign thyroid nodules: experimental and clinical studies

PURPOSE

To obtain the treatment parameters of internally cooled microwave antenna and to evaluate the feasibility of ultrasound-guided percutaneous microwave ablation (MWA) for benign thyroid nodules.

MATERIALS AND METHODS

MWAs were performed by microwave antenna (16G) in ex vivo porcine liver. The lesion diameters achieved in different groups (20, 25, and 30 W for 3, 5, 7, 10, and 12 min) were compared. The clinical study was approved by the ethics committee. Written informed consent was obtained from all patients. MWA was performed in 11 patients (male to female ratio=1:10; mean age, 50±7 years) with 11 benign thyroid nodules. Ultrasound scan, laboratory data, and clinical symptoms were evaluated before and 1 day and 1, 3, 6, 9, and 12 months after the procedure.

RESULTS

In ex vivo study, the ablation lesion at 30 W 12 min tended to have appropriate scope and spherical shape. In clinical study, the follow-up periods ranged from 1 to 9 months. At the last follow-up, the largest diameter decreased from 2.9±1.0 (range, 1.6-4.1) to 1.9±0.7 (range, 0.4-3.0) cm (P<0.01), and the volume decreased from 5.30±4.88 (range, 0.89-14.81) to 2.40±2.06 (range, 0.02-6.35) ml (P<0.01). The volume reduction ratio was 45.99±29.90 (range, 10.56-98.15) %. The cosmetic grading score was reduced from 3.20±0.79 to 2.30±0.95 (P<0.05). One patient experienced temporary nerve palsy and was recovered within 2 months after treatment.

CONCLUSION

The internally cooled microwave antenna can yield ideal ablation lesions, and ultrasound-guided percutaneous MWA is a feasible technique for benign thyroid nodules.

[Microwave tumor ablation. New devices, new applications?]

CLINICAL ISSUE

The majority of patients with hepatic malignancies are not amenable to surgical resection. In some of these cases minimally invasive ablative therapies are a treatment option.

STANDARD TREATMENT

Besides radiofrequency ablation, the most common ablative therapies are cryoablation, laser ablation and microwave ablation.

TREATMENT INNOVATIONS

The classic fields of application of microwave ablation are the treatment of malignancies of the liver, kidneys and lungs. Furthermore, cases of treatment of bone tumors and tumors of the adrenal gland have been reported as well as treatment of secondary hypersplenism.

PERFORMANCE

The manufacturers of microwave systems pursue different strategies to reach an optimal ablation zone, such as water or gas cooling of the antenna, the simultaneous use of different antennas or an automatic modulation of the microwave energy and frequency.

ACHIEVEMENTS

In contrast to other tumor ablation methods microwave ablation causes a direct heating of a tissue volume, thus this method is less vulnerable to the cooling effect of vessels in the ablation zone. Moreover the electric conductivity of the treated tissue does not influence microwave radiation so that microwave ablation has advantages for the treatment of high-resistance organs, such as the lungs or bone. Some publications have shown that microwave ablation causes larger ablation zones in less time in comparison to radiofrequency ablation.

PRACTICAL RECOMMENDATIONS

Classic indications for microwave ablation are the treatment of malignancies of the liver, lungs and kidneys. Initial technical problems have been solved, so that an increasing significance of the microwave ablation among the ablative therapies is to be expected.

MWA combined with TACE as a combined therapy for unresectable large-sized hepotocellular carcinoma

PURPOSE

To evaluate the efficacy and safety of microwave ablation combined with transcatheter arterial chemoembolization for unresectable large-sized hepotocellular carcinoma.

MATERIALS AND METHODS

Institutional review board approval and informed consent were obtained. Between May 2004 and December 2006, 34 consecutive patients with large unresectable hepatocellular carcinoma (>5 cm) were alternately enrolled in one of two treatment groups: group 1 (n = 18), in which TACE was performed alone, and group 2 (n = 16), in which percutaneous ablation of HCC with microwave ablation was performed 2-4 weeks after TACE. All patients were followed up for 2-28 months to observe long-term therapeutic effects and complications in both groups. Tumor reduction rates, median survival time, and cumulative survival rates in both groups were calculated by using the unpaired Student t test and Kaplan-Meier method.

RESULTS

Follow-up images showed reduction in tumor size was seen in 21 patients (61.7%; 7/18 in group 1, 14/16 in group 2), survival rates were better in group 2 than in group 1 (P = 0.003), during the median follow-up of 8 months, 10 patients (62.5%) remained alive in group 2, whereas 6 patients (33.3%) remained alive in group 1, the mean survival times were 6.13 months ± 0.83 in group 1 and 11.61 months ± 1.59 in group 2.

CONCLUSION

MWA combined with transcatheter arterial chemoembolization appears to be an effective and promising approach for the treatment of large-sized unresectable hepotocellular carcinoma. However, large-scale randomized clinical trials are needed to determine the future role of this treatment.

Comparison of microwave ablation and multipolar radiofrequency ablation, both using a pair of internally cooled interstitial applicators: results in ex vivo porcine livers

PURPOSE

To compare the effectiveness of microwave ablation (MWA) and multipolar radiofrequency ablation (RFA) in ex vivo porcine livers, in both cases using a pair of internally cooled interstitial applicators.

MATERIALS AND METHODS

MWA was performed on ex vivo porcine livers (n = 60) using a pair of simultaneously powered, internally cooled shaft interstitial antennae. Four power settings were used: 50 W, 60 W, 70 W and 80 W (n = 15 per setting). Multipolar RFA was also performed on ex vivo porcine livers (n = 30), also using a pair of simultaneously powered, internally cooled shaft interstitial bipolar applicators. This was performed for two applicator types T30 (3 cm length) and T40 (4 cm length) at a manufacturer prescribed power of 60 W and 80 W, respectively (n = 15 per applicator). Spacing between the two probes was 2 cm in all cases. Each power setting was applied for 15 ablations for 10 min each. The long-axis diameter (Dl), short-axis diameter (Ds) and the ratio Ds/Dl for each ablation were measured. Temperature data were recorded at 10 positions. Temperature curves were recorded at 3 locations, as well as the time required for the temperature to rise to 50°C.

RESULTS

Dl and Ds for all the power settings of MWA were significantly larger than that of both kinds of multipolar RFA (P < 0.05). The rates of temperature to rise to 50°C in all the MW ablations power settings were significantly faster than those in both multipolar RF ablations.

CONCLUSION

MWA by the simultaneous application of double antennae may be more advantageous for treating larger liver tumour than multipolar RFA.

Treatment of liver tumours adjacent to hepatic hilum with percutaneous microwave ablation combined with ethanol injection: a pilot study

PURPOSE

To evaluate the feasibility, safety and efficacy of ultrasound-guided percutaneous microwave ablation combined with percutaneous ethanol injection in the treatment of liver tumours adjacent to the hepatic hilum.

MATERIALS AND METHODS

From December 2005 to April 2008, 18 consecutive patients with 18 pathologically proven or clinically diagnosed liver tumours (15 HCCs, three metastatic tumours) adjacent to the hepatic hilum underwent ultrasound-guided percutaneous microwave ablation combined with percutaneous ethanol injection. One or two microwave antennae were inserted and placed at designated places in the tumour. One or two ethanol needles were placed at the tumour periphery near the hepatic hilum. An aliquot of 2-10 mL of absolute ethanol was injected into the tumour at the same time as microwave emission. A thermocouple was placed directly abutting the bile ducts of the hepatic hilum to monitor temperature in real time during ablation to avoid thermal injury.

RESULTS

No more than two sessions were performed to complete the treatment (one session for 10 patients, two sessions for eight, mean 1.4 sessions per patient). Complete ablation was achieved in 94.4% (17 out of 18 cases). In a median follow up of 15 months (range 4 to 27 months, mean 13.5 months), no mortality or complications occurred. Local tumour progression was noted in one patient 12 months after treatment.

CONCLUSION

A combination of ultrasound-guided percutaneous microwave ablation and percutaneous ethanol injection assisted with real-time temperature monitoring appears to be feasible and effective in the treatment of liver tumours adjacent to the hepatic hilum, and initial experience with safety is promising.

Ultrasound-guided percutaneous microwave ablation of splenic metastasis: report of four cases and literature review

PURPOSE

To investigate the feasibility, safety and efficacy of ultrasound guided percutaneous microwave (MW) ablation for small splenic metastasis.

MATERIALS AND METHODS

A total of four patients with five pathologically proven splenic metastases (from ovarian, pulmonary, gastric adenocarcinoma and hepatocellular carcinoma, respectively) 1.3 to 2.9 cm in diameter were treated with microwave ablation. A cooled-shaft needle antenna was percutaneously inserted into the tumour under ultrasound guidance. One thermocouple was placed about 0.5 cm away from the tumour to monitor temperature in real time during ablation. Microwaves were emitted at 60 W for 600 s routinely and prolonged as necessary to attain temperatures sufficient to ensure tumour killing. Treatment efficacy was assessed by contrast-enhanced imaging at 1, 3 and 6 months, and every 6 months thereafter.

RESULTS

All tumours were completely ablated at a single session and no complications occurred. No local tumour progression was observed at a mean follow up of 22 ± 17.1 months (range 4 to 43 months). The ablation zone was well defined on contrast-enhanced imaging and it gradually shrank with time. One new metastatic lesion was detected in the spleen at 11 months after the ablation and was successfully treated by another MW ablation. The post-ablation survival was mean 22 months. No other complications were observed except for fever and abdominal pain.

CONCLUSIONS

Ultrasound-guided percutaneous MW ablation appears to be a safe and effective minimally invasive technique for management of small splenic metastasis in selected patients.