CT-guided treatment of ultrasonically invisible hepatocellular carcinoma

Change in tissue resistance after irreversible electroporation in liver tumors as an indicator of treatment success - A multi-center analysis with long term follow-up

INTRODUCTION

A nationwide multicenter study was performed to examine whether there is a correlation between decrease in tissue resistance and time to local tumor recurrence after irreversible electroporation (IRE) in patients with hepatocellular carcinoma (HCC) and colorectal cancer liver metastases (CRCLM).

METHODS

All patients treated with IRE for liver tumors in Sweden from 2011 until 2018 were included. Patient characteristics and recurrence patterns were obtained from medical records and radiological imaging. All procedural data from the IRE hardware at the three hospitals performing IRE were retrieved. The resistance during each pulse and the change during each treatment were calculated. The electrode pair with the smallest decrease in tissue resistance was used and compared with the time to LTP.

RESULTS

149 patients with 206 tumors were treated. Exclusion due to missing and inaccurate data resulted in 124 patients with 170 tumors for the analyses. In a multivariable Cox regression model, a smaller decrease in tissue resistance and larger tumor size were associated with shorter time to local tumor recurrence for CRCLM, but not for HCC.

CONCLUSION

There was an association between a decrease in tissue resistance and time to local tumor recurrence for CRCLM. The decrease in resistance, in combination with a rise in current, may be the parameters the interventionist should use during IRE to decide if the treatment is successful.

Ablative and non-surgical therapies for early and very early hepatocellular carcinoma: a systematic review and network meta-analysis

Background

A wide range of ablative and non-surgical therapies are available for treating small hepatocellular carcinoma in patients with very early or early-stage disease and preserved liver function.

Objective

To review and compare the effectiveness of all current ablative and non-surgical therapies for patients with small hepatocellular carcinoma (≤ 3 cm).

Design

Systematic review and network meta-analysis.

Data sources

Nine databases (March 2021), two trial registries (April 2021) and reference lists of relevant systematic reviews.

Review methods

Eligible studies were randomised controlled trials of ablative and non-surgical therapies, versus any comparator, for small hepatocellular carcinoma. Randomised controlled trials were quality assessed using the Cochrane Risk of Bias 2 tool and mapped. The comparative effectiveness of therapies was assessed using network meta-analysis. A threshold analysis was used to identify which comparisons were sensitive to potential changes in the evidence. Where comparisons based on randomised controlled trial evidence were not robust or no randomised controlled trials were identified, a targeted systematic review of non-randomised, prospective comparative studies provided additional data for repeat network meta-analysis and threshold analysis. The feasibility of undertaking economic modelling was explored. A workshop with patients and clinicians was held to discuss the findings and identify key priorities for future research.

Results

Thirty-seven randomised controlled trials (with over 3700 relevant patients) were included in the review. The majority were conducted in China or Japan and most had a high risk of bias or some risk of bias concerns. The results of the network meta-analysis were uncertain for most comparisons. There was evidence that percutaneous ethanol injection is inferior to radiofrequency ablation for overall survival (hazard ratio 1.45, 95% credible interval 1.16 to 1.82), progression-free survival (hazard ratio 1.36, 95% credible interval 1.11 to 1.67), overall recurrence (relative risk 1.19, 95% credible interval 1.02 to 1.39) and local recurrence (relative risk 1.80, 95% credible interval 1.19 to 2.71). Percutaneous acid injection was also inferior to radiofrequency ablation for progression-free survival (hazard ratio 1.63, 95% credible interval 1.05 to 2.51). Threshold analysis showed that further evidence could plausibly change the result for some comparisons. Fourteen eligible non-randomised studies were identified (n ≥ 2316); twelve had a high risk of bias so were not included in updated network meta-analyses. Additional non-randomised data, made available by a clinical advisor, were also included (n = 303). There remained a high level of uncertainty in treatment rankings after the network meta-analyses were updated. However, the updated analyses suggested that microwave ablation and resection are superior to percutaneous ethanol injection and percutaneous acid injection for some outcomes. Further research on stereotactic ablative radiotherapy was recommended at the workshop, although it is only appropriate for certain patient subgroups, limiting opportunities for adequately powered trials.

Limitations

Many studies were small and of poor quality. No comparative studies were found for some therapies.

Conclusions

The existing evidence base has limitations; the uptake of specific ablative therapies in the United Kingdom appears to be based more on technological advancements and ease of use than strong evidence of clinical effectiveness. However, there is evidence that percutaneous ethanol injection and percutaneous acid injection are inferior to radiofrequency ablation, microwave ablation and resection.

Study registration

PROSPERO CRD42020221357.

Funding

This award was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment (HTA) programme (NIHR award ref: NIHR131224) and is published in full in Health Technology Assessment; Vol. 27, No. 29. See the NIHR Funding and Awards website for further award information.

Single medium-sized hepatocellular carcinoma treated with sequential conventional transarterial chemoembolization (cTACE) and microwave ablation at 4 weeks versus cTACE alone: a propensity score

Background

Microwave ablation (MWA) is a potentially curative treatment for unresectable patients with hepatocellular carcinoma (HCC) ≤ 3 cm, while its therapeutic efficacy decreases significantly for HCC > 3cm. Previous studies have demonstrated that conventional transarterial chemoembolization (cTACE) combined with MWA (cTACE-MWA) may improve local tumor control rate and reduce the recurrence rate for HCC > 3cm. However, there have been few study designs to analyze the clinical efficacy of cTACE-MWA for medium-sized HCC (3–5cm). Therefore, this study aims to compare the clinical efficacy and safety of cTACE-MWA with cTACE alone for a single medium-sized HCC of 3–5 cm in diameter.

Methods

We retrospectively investigate the data of 90 patients with a single medium-sized HCC who were referred to our hospital and underwent cTACE-MWA or cTACE alone from December 2017 to March 2020. Then, patients were identified with propensity score-matched (1:1). The local tumor response to treatment and time to progression (TTP) were compared using mRECIST criteria between the cTACE-MWA group and the cTACE group.

Results

A total of 42 patients were included after matching (cTACE-MWA: 21; cTACE: 21). Comparing with cTACE, cTACE-MWA demonstrate significantly better local tumor control (ORR: 95.2% vs 61.9%, p = 0.02; DCR: 95.2% vs 66.7%, p = 0.045) and TTP (median 19.8 months vs 6.8 months, p < 0.001). The 1- and 2-year cumulative probabilities of OS were 100% and 95% in the cTACE-MWA group, which were significantly higher than those in the cTACE group (95% and 76%) (p = 0.032). Multivariate Cox regression analysis illustrates that cTACE-MWA was associated with better TTP (hazard ratio, 0.28; 95% CI: 0.1, 0.76; p = 0.012), but tumor size was associated with worse TTP (hazard ratio, 1.71; 95% CI: 1.01, 2.89; p = 0.045).

Conclusions

cTACE followed by MWA improved TTP and OS in patients with a single medium-sized HCC, and no major complication was observed in this study.

Rapid Quality Assessment of Nonrigid Image Registration Based on Supervised Learning

When preprocedural images are overlaid on intraprocedural images, interventional procedures benefit in that more structures are revealed in intraprocedural imaging. However, image artifacts, respiratory motion, and challenging scenarios could limit the accuracy of multimodality image registration necessary before image overlay. Ensuring the accuracy of registration during interventional procedures is therefore critically important. The goal of this study was to develop a novel framework that has the ability to assess the quality (i.e., accuracy) of nonrigid multimodality image registration accurately in near real time. We constructed a solution using registration quality metrics that can be computed rapidly and combined to form a single binary assessment of image registration quality as either successful or poor. Based on expert-generated quality metrics as ground truth, we used a supervised learning method to train and test this system on existing clinical data. Using the trained quality classifier, the proposed framework identified successful image registration cases with an accuracy of 81.5%. The current implementation produced the classification result in 5.5 s, fast enough for typical interventional radiology procedures. Using supervised learning, we have shown that the described framework could enable a clinician to obtain confirmation or caution of registration results during clinical procedures.

Image-guided microwave ablation of hepatocellular carcinoma (≤5.0 cm): is MR guidance more effective than CT guidance?

BACKGROUND

Given their widespread availability and relatively low cost, percutaneous thermal ablation is commonly performed under the guidance of computed tomography (CT) or ultrasound (US). However, such imaging modalities may be restricted due to insufficient image contrast and limited tumor visibility, which results in imperfect intraoperative treatment or an increased risk of damage to critical anatomical structures. Currently, magnetic resonance (MR) guidance has been proven to be a possible solution to overcome the above shortcomings, as it provides more reliable visualization of the target tumor and allows for multiplanar capabilities, making it the modality of choice. Unfortunately, MR-guided ablation is limited to specialized centers, and the cost is relatively high. Is ablation therapy under MR guidance better than that under CT guidance? This study retrospectively compared the efficacy of CT-guided and MR-guided microwave ablation (MWA) for the treatment of hepatocellular carcinoma (HCC ≤ 5.0 cm).

METHODS

In this retrospective study, 47 patients and 54 patients received MWA under the guidance of CT and MR, respectively. The inclusion criteria were a single HCC ≤ 5.0 cm or a maximum of three. The local tumor progression (LTP), overall survival (OS), prognostic factors for local progression, and safety of this technique were assessed.

RESULTS

All procedures were technically successful. The complication rates of the two groups were remarkably different with respect to incidences of liver abscess and pleural effusion (P < 0.05). The mean LTP was 44.264 months in the CT-guided group versus 47.745 months in the MR-guided group of HCC (P = 0.629, log-rank test). The mean OS was 56.772 months in the patients who underwent the CT-guided procedure versus 58.123 months in those who underwent the MR-guided procedure (P = 0.630, log-rank test). Multivariate Cox regression analysis further illustrated that tumor diameter (< 3 cm) and the number of lesions (single) were important factors affecting LTP and OS.

CONCLUSIONS

Both CT-guided and MR-guided MWA are comparable therapies for the treatment of HCC (< 5 cm), and there was no difference in survival between the two groups. However, MR-guided MWA could reduce the incidence of complications.

A review on radiofrequency, microwave and high-intensity focused ultrasound ablations for hepatocellular carcinoma with cirrhosis

Importance

Hepatocellular carcinoma (HCC) is usually accompanied by liver cirrhosis, which makes treatment of this disease challenging. Liver transplantation theoretically provides an ultimate solution to the disease, but the maximal surgical stress and the scarcity of liver graft make this treatment option impossible for some patients. In an ideal situation, a treatment that is safe and effective should provide a better outcome for patients with the dilemma.

Objective

This article aims to give a comprehensive review of various types of loco-ablative treatment for HCC.

Evidence Review

Loco-ablative treatment bridges the gap between surgical resection and transarterial chemotherapy. Various types of ablative therapy have their unique ability, and evidence-based outcome analysis is the most important key to assisting clinicians to choose the most suitable treatment modality for their patients.

Findings

Radiofrequency ablation (RFA) has a relatively longer history and more evidence to support its effectiveness. Microwave ablation (MWA) is gaining momentum because of its shorter ablation time and consistent ablation zone. High-intensity focused ultrasound (HIFU) ablation is a relatively new technology that provides non-invasive treatment for patients with HCC. It has been carried out at centers of excellence and it is a safe and effective treatment option for selected patients with HCC and liver cirrhosis.

Conclusion and Relevance

Selective use of different loco-ablative therapies will enhance clinicians' treatment options for treatment of HCC.

Combined Ultrasound and CT-Guided Iodine-125 Seeds Implantation for Treatment of Residual Hepatocellular Carcinoma Located at Complex Sites After Transcatheter Arterial Chemoembolization

Purpose

The purpose of this study was to evaluate the efficacy and safety of iodine-125 (¹²⁵I) seeds implantation under ultrasound and computed tomography (CT) guidance in the treatment of residual hepatocellular carcinoma (HCC) located at complex sites after transcatheter arterial chemoembolization (TACE).

Methods

This retrospective study analyzed the consecutive medical records of 31 HCC patients with residual tumors located at complex sites (such as large blood vessels, gallbladder, diaphragm dome, etc.) after TACE from May 2014 to December 2018, all of whom received ¹²⁵I seeds implantation therapy. Overall survival (OS), progression-free survival (PFS), recurrence, and complications were documented.

Results

A total of 607 seeds were implanted in 31 patients, with an average of 19.6±10.4 (range, 8–48) seeds per patient. Median OS and PFS were 33 months (95% CI: 27.1 months, 38.9 months) and 15 months (95% CI: 9.6 months, 20.4 months), respectively. Although univariate analysis showed that albumin, prothrombin time, alpha-fetoprotein level, Child-Pugh score, and lipiodol deposition in tumor were associated with OS, multivariate analysis showed that none of them was an independent prognostic factor for OS. Multivariate analysis showed that prothrombin time was an independent prognostic factor for PFS. No operation-related deaths in this study. Although pneumothorax was present in two patients and subcutaneous abscess in one patient, symptoms improved in all three patients with appropriate treatment. Common minor complications included fever, abdominal pain and leukopenia and no grade≥3 adverse events were observed.

Conclusions

¹²⁵I seeds implantation under the combined guidance of ultrasound and CT is safe and effective for patients with residual HCC located at complex sites after TACE. This is a promising treatment approach and deserves further discussion.

Percutaneous microwave ablation applications for liver tumors: recommendations for COVID-19 patients

Microwave ablation (MWA) is an alternative locoregional therapy to surgical resection of solid tumors in the treatment of malignancies, and is widely used for hepatic tumors. It has a slightly higher overall survival (OS) rate compared to external beam radiation therapy (EBRT), and proton beam therapy (PBT), and better long-term recurrence-free OS rate compared to radiofrequency ablation (RFA). In this paper, current commercial devices, most recent noncommercial designs, and the principles behind them alongside the recently reported developments and issues of MWA are reviewed. The paper also provides microscopic insights on effects of microwave irradiation in the body. Our review shows that MWA is a safe and effective, minimally invasive method with high ablation completion rates. However, for large tumors, the completion rates slightly decrease, and recurrences increase. Thus, for large tumors we suggest using a cooled shaft antenna or multiple antenna placements. Comparisons of the two common ablation frequencies 915 MHz and 2.45 GHz have shown inconsistent results due to non-identical conditions. This review suggests that 915 MHz devices are more effective for ablating large tumors and the theory behind MWA effects corroborates this proposition. However, for small tumors or tumors adjacent to vital organs, 2.45 GHz is suggested due to its more localized ablation zone. Among the antenna designs, the double-slot antenna with a metallic choke seems to be more effective by localizing the radiation around the tip of the antenna, while also preventing backward radiation towards the skin. The review also pertains to the use of MWA in COVID-19 patients and risk factors associated with the disease. MWA should be considered for COVID-19 patients with hepatic tumors as a fast treatment with a short recovery time. As liver injury is also a risk due to COVID-19, it is recommended to apply liver function tests to monitor abnormal levels in alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bilirubin, and other liver function indicators.

Radiofrequency ablation following artificial ascites and pleural effusion creation may improve outcomes for hepatocellular carcinoma in high-risk locations

PURPOSE

To investigate the outcomes of radiofrequency ablation (RFA) following artificial ascites (AA) and artificial pleural effusion (AP) creation for hepatocellular carcinoma (HCC) in high-risk locations.

MATERIALS AND METHODS

Eligible patients were divided into 2 study periods (non-AAAP and AAAP groups) with AAAP performed in the latter period. Local tumor progression, primary technique effectiveness and complications were compared between patients with and without AAAP. Cumulative probability of local tumor progression and overall survival were estimated with Kaplan-Meier curves.

RESULTS

One hundred thirty-eight patients with 195 tumors were evaluated. AAAP was performed in 48 patients with 76 tumors. Local tumor progression rates at 12 and 24 months were 9.3% and 22.2% in the non-AAAP group versus 5.5% and 9% in the AAAP group (p < 0.0001). Primary technique effectiveness was achieved in 76.5% of the non-AAAP group versus 89.5% of the AAAP group (p = 0.046). Night (7.6%) major complications occurred in the non-AAAP group and 2 (2.6%) cases occurred in the AAAP group. Therapy-oriented severity grading system after RFA was lower in the AAAP group (p = 0.02). Overall survival rates at 12 and 24 months were 85.6% and 77.7% in the non-AAAP group versus 97.2% and 89.7% in the AAAP group (p = 0.033).

CONCLUSION

RFA following AA and AP for high-risk located HCC may improve outcomes.

CT-Guided Percutaneous Microwave Ablation of Tumors in the Hepatic Dome: Assessment of Efficacy and Safety

PURPOSE

To evaluate the technique, efficacy, safety, and clinical outcomes of CT-guided microwave ablation of tumors in the hepatic dome.

MATERIALS AND METHODS

Retrospective review was conducted of 46 consecutive patients (31 men and 15 women; mean age, 64 y) treated with CT-guided microwave ablation for hepatic-dome tumors between June 2011 and December 2014. Baseline demographics of sex, tumor diagnosis, tumor location, tumor size, and technical details were recorded. Technical success was evaluated. Treatment response was assessed per European Association for the Study of the Liver criteria. Overall success and overall survival were calculated, and complications were recorded.

RESULTS

Forty-eight tumors were treated. Tumor locations included segments VIII (n = 32), VII (n = 10), and VIa (n = 6). Mean tumor size was 2.4 cm (range, 0.9-5.2 cm). Thirty-four tumors (70%) were treated following creation of artificial ascites with 0.9% normal saline solution (mean volume, 1,237 mL; range, 300-3,000 mL). The technical success rate was 100%, and the complete response rate was 94%. Overall survival rate was 73.9% over 24.7 months of follow-up. There were no major complications. Two patients experienced small, asymptomatic pneumothoraces that were aspirated at the time of the procedure and required no further treatment.

CONCLUSIONS

CT-guided microwave ablation of tumors in the hepatic dome is associated with a high technical success rate, high complete response rate, and low complication rate.

Graphics Processing Unit-Accelerated Nonrigid Registration of MR Images to CT Images During CT-Guided Percutaneous Liver Tumor Ablations

RATIONALE AND OBJECTIVES

Accuracy and speed are essential for the intraprocedural nonrigid magnetic resonance (MR) to computed tomography (CT) image registration in the assessment of tumor margins during CT-guided liver tumor ablations. Although both accuracy and speed can be improved by limiting the registration to a region of interest (ROI), manual contouring of the ROI prolongs the registration process substantially. To achieve accurate and fast registration without the use of an ROI, we combined a nonrigid registration technique on the basis of volume subdivision with hardware acceleration using a graphics processing unit (GPU). We compared the registration accuracy and processing time of GPU-accelerated volume subdivision-based nonrigid registration technique to the conventional nonrigid B-spline registration technique.

MATERIALS AND METHODS

Fourteen image data sets of preprocedural MR and intraprocedural CT images for percutaneous CT-guided liver tumor ablations were obtained. Each set of images was registered using the GPU-accelerated volume subdivision technique and the B-spline technique. Manual contouring of ROI was used only for the B-spline technique. Registration accuracies (Dice similarity coefficient [DSC] and 95% Hausdorff distance [HD]) and total processing time including contouring of ROIs and computation were compared using a paired Student t test.

RESULTS

Accuracies of the GPU-accelerated registrations and B-spline registrations, respectively, were 88.3 ± 3.7% versus 89.3 ± 4.9% (P = .41) for DSC and 13.1 ± 5.2 versus 11.4 ± 6.3 mm (P = .15) for HD. Total processing time of the GPU-accelerated registration and B-spline registration techniques was 88 ± 14 versus 557 ± 116 seconds (P < .000000002), respectively; there was no significant difference in computation time despite the difference in the complexity of the algorithms (P = .71).

CONCLUSIONS

The GPU-accelerated volume subdivision technique was as accurate as the B-spline technique and required significantly less processing time. The GPU-accelerated volume subdivision technique may enable the implementation of nonrigid registration into routine clinical practice.

A simulator for percutaneous hepatic microwave thermal ablation under ultrasound guidance

The purpose of this study was to provide a simulation therapy environment for microwave thermal ablation (MWA) under the guidance of ultrasound, and to present an inexpensive and portable simulator built on real patient-based pre-operative computed tomography (CT) data. We established an experimental simulation system for teaching MWA and present the results of a preliminary evaluation of the simulator's realism and utility for training. The system comprises physical elements of an electromagnetic tracking device and an abdominal phantom, and software elements providing three-dimensional (3D) image processing tools, real-time navigation functions and objective evaluation function module. Details of the novel aspects of this system are presented, including a portable electromagnetic tracking device, adoption of real patient-based pre-operative CT data of liver, operation simulation of MWA, and recording and playback of the operation simulation. Patients with liver cancer were selected for evaluation of the clinical application value of the experimental simulation system. A total of 50 consultant interventional radiologists and 20 specialist registrars in radiology rated the simulator's hardware reality and overall ergonomics. Results show that the simulator system we describe can be used as a training tool for MWA. It enables training with real patient cases prior to surgery, and it can provide a realistic simulation of the actual procedure.

Coil-assisted RFA of poorly visible liver tumors: effectiveness and risk factors of local tumor progression

OBJECTIVES

This study was designed to determine the effectiveness of a percutaneously inserted coil as a landmark before radiofrequency ablation (RFA) of poorly visible liver tumors on unenhanced computed tomography and ultrasound.

METHODS

This was a single-center, retrospective study of 46 consecutive patients treated from January 2008 to June 2012 with RFA under CT guidance for 57 poorly visible liver tumors after percutaneous coil insertion. Effectiveness was evaluated by the rate of local tumor progression (LTP), and the risk factors of LTP were evaluated by multiple univariate analysis.

RESULTS

After a mean follow-up of 15.9 months, the overall rate of LTP was 22.8 % (13/57). An increase in the distance between the coil and the center of the tumor was a predictive factor of LTP (p = 0.005) and resulted in an increase in time to place the RFA probe. LTP was significantly reduced in case of coil placed within the tumor (10 vs. 43.5 %, p = 0.009).

CONCLUSIONS

The effectiveness of the "coil-assisted" RFA for poorly visible liver tumors is improved by centering the coil in the tumor in order to facilitate the placement of the RFA probe and equal to the results of RFA under direct image guidance.

PET/CT-guided interventions: personnel radiation dose

PURPOSE

To quantify radiation exposure to the primary operator and staff during PET/CT-guided interventional procedures.

METHODS

In this prospective study, 12 patients underwent PET/CT-guided interventions over a 6 month period. Radiation exposure was measured for the primary operator, the radiology technologist, and the nurse anesthetist by means of optically stimulated luminescence dosimeters. Radiation exposure was correlated with the procedure time and the use of in-room image guidance (CT fluoroscopy or ultrasound).

RESULTS

The median effective dose was 0.02 (range 0-0.13) mSv for the primary operator, 0.01 (range 0-0.05) mSv for the nurse anesthetist, and 0.02 (range 0-0.05) mSv for the radiology technologist. The median extremity dose equivalent for the operator was 0.05 (range 0-0.62) mSv. Radiation exposure correlated with procedure duration and with the use of in-room image guidance. The median operator effective dose for the procedure was 0.015 mSv when conventional biopsy mode CT was used, compared to 0.06 mSv for in-room image guidance, although this did not achieve statistical significance as a result of the small sample size (p = 0.06).

CONCLUSION

The operator dose from PET/CT-guided procedures is not significantly different than typical doses from fluoroscopically guided procedures. The major determinant of radiation exposure to the operator from PET/CT-guided interventional procedures is time spent in close proximity to the patient.

Review of dynamic contrast-enhanced ultrasound guidance in ablation therapy for hepatocellular carcinoma

Local ablative techniques-percutaneous ethanol injection, microwave coagulation therapy and radiofrequency ablation (RFA)-have been developed to treat unresectable hepatocellular carcinoma (HCC). The success rate of percutaneous ablation therapy for HCC depends on correct targeting of the tumor via an imaging technique. However, probe insertion often is not completely accurate for small HCC nodules, which are poorly defined on conventional B-mode ultrasound (US) alone. Thus, multiple sessions of ablation therapy are frequently required in difficult cases. By means of two breakthroughs in US technology, harmonic imaging and the development of second-generation contrast agents, dynamic contrast-enhanced harmonic US imaging with an intravenous contrast agent can depict tumor vascularity sensitively and accurately, and is able to evaluate small hypervascular HCCs even when B-mode US cannot adequately characterize the tumors. Therefore, dynamic contrast-enhanced US can facilitate RFA electrode placement in hypervascular HCC, which is poorly depicted by B-mode US. The use of dynamic contrast-enhanced US guidance in ablation therapy for liver cancer is an efficient approach. Here, we present an overview of the current status of dynamic contrast-enhanced US-guided ablation therapy, and summarize the current indications and outcomes of reported clinical use in comparison with that of other modalities.

Contrast-enhanced ultrasound-guided microwave ablation for hepatocellular carcinoma inconspicuous on conventional ultrasound

OBJECTIVE

To evaluate the efficiency and feasibility of contrast-enhanced ultrasound (CEUS)-guided microwave ablation for hepatocellular carcinoma inconspicuous on conventional US.

MATERIALS AND METHODS

From March 2006 to February 2010, 107 patients (93 male, 14 female; mean age 58.9±11.0 years) with 107 hepatocellular carcinoma (HCC) nodules (mean maximum diameter 19.5±8.5 mm) inconspicuous on conventional US underwent microwave (MW) ablation under CEUS guidance in this study. US contrast agent was SonoVue (Bracco, Milan, Italy), a second-generation contrast agent. CEUS was performed first, and then MW ablation was carried out by means of CEUS guidance under unconscious intravenous anaesthesia if the tumours were displayed on CEUS.

RESULTS

105 tumours were successfully visualised on CEUS by using 1-2 times contrast agent injection and MW ablation was performed under CEUS guidance. The technical success rate was 98.13% (105/107). The number of antenna insertions for each tumour was 1.89±0.92, and the mean session of MW ablation for each tumour was 1.08±0.28. The mean duration of energy application for each tumour was 7.05±4.03 min. The follow-up time was 12-54 months (median 18 months). The technique effectiveness rate was 99.05% (104/105). The local tumour progression rate was 1.9% (2/105). There were no severe complications in any patients.

CONCLUSION

CEUS-guided MW ablation is an efficient and feasible treatment method for patients with hepatocellular carcinoma inconspicuous on conventional US.

Microwave ablation assisted by a computerised tomography-ultrasonography fusion imaging system for liver lesions: an ex vivo experimental study

PURPOSE

To investigate the feasibility and validity of real-time guidance using a fusion imaging system that combines ultrasonography (US) and computerised tomography (CT) information in the targeting and subsequent microwave ablation of a liver target inconspicuous on US.

MATERIALS AND METHODS

The study was an experimental ex vivo study in calf livers with internal targets, simulating a focal liver lesion, focused on the accuracy of real-time US using a multimodality fusion imaging system in combination with 15 gauge (G) microwave antennae. US image and pre-procedural CT image were fused by the external markers registration procedure. Microwave antennae were inserted into the liver to ablate the target assisted by the CT-US fusion imaging system. Finally, a post-procedural CT with needles in situ and multiplanar reconstructions were performed to compare with pre-procedural CT information in order to calculate the accuracy of positioning (distance between the needle tip and the target).

RESULTS

Eight insertions were planned and eight ablations were performed in four calf livers. The calf livers were undertaken successfully on external markers registration procedure. The mean registration error in the four livers was 2.1 ± 0.1 mm, 2.8 ± 0.1 mm, 3.4 ± 0.1 mm and 2.3 ± 0.1 mm, respectively. The accuracy of the matched US-CT images was very satisfactory in the fact that it was found there was a mean discrepancy of 1.63 ± 1.06 mm.

CONCLUSION

Real-time registration and fusion of pre-procedural CT volume images with intraprocedural US is feasible and accurate for microwave (MW) ablation in experimental setting. Further studies are warranted to validate the system under clinical conditions.

Microwave ablation assisted by a real-time virtual navigation system for hepatocellular carcinoma undetectable by conventional ultrasonography

OBJECTIVES

To evaluate the efficiency and feasibility of microwave (MW) ablation assisted by a real-time virtual navigation system for hepatocellular carcinoma (HCC) undetectable by conventional ultrasonography.

METHODS

18 patients with 18 HCC nodules (undetectable on conventional US but detectable by intravenous contrast-enhanced CT or MRI) were enrolled in this study. Before MW ablation, US images and MRI or CT images were synchronized using the internal markers at the best timing of the inspiration. Thereafter, MW ablation was performed under real-time virtual navigation system guidance. Therapeutic efficacy was assessed by the result of contrast-enhanced imagings after the treatment.

RESULTS

The target HCC nodules could be detected with fusion images in all patients. The time required for image fusion was 8-30 min (mean, 13.3 ± 5.7 min). 17 nodules were successfully ablated according to the contrast enhanced imagings 1 month after ablation. The technique effectiveness rate was 94.44% (17/18). The follow-up time was 3-12 months (median, 6 months) in our study. No severe complications occurred. No local recurrence was observed in any patients.

CONCLUSIONS

MW ablation assisted by a real-time virtual navigation system is a feasible and efficient treatment of patients with HCC undetectable by conventional ultrasonography.

Utility of contrast-enhanced ultrasonography with Sonazoid in radiofrequency ablation for hepatocellular carcinoma

BACKGROUND AND AIMS

Kupffer imaging in contrast-enhanced ultrasonography (CEUS) with Sonazoid, which lasts for 60 min or longer, may be useful in ultrasound-guided percutaneous tumor ablation. The utility of Sonazoid in radiofrequency ablation (RFA) of hepatocellular carcinoma (HCC) was investigated in this study.

METHODS

We analyzed a total of 716 HCC nodules that were detected on dynamic computed tomography in 316 patients. Detectability of these nodules was compared between CEUS and conventional ultrasonography. The effectiveness in the treatment was assessed by comparing the mean numbers of treatment sessions of RFA in patients treated with CEUS and that in historical controls matched for tumor and background conditions.

RESULTS

Detectability of tumor nodule was 83.5% in conventional ultrasonography and 93.2% in CEUS (P=0.04). Sixty-nine nodules in 52 patients were additionally detected with CEUS. The number of additionally detected tumor nodules was positively correlated with serum albumin level (P=0.016). The number of RFA sessions was 1.33±0.45 with CEUS as compared to 1.49±0.76 in the historical controls (P=0.0019).

CONCLUSIONS

CEUS with Sonazoid is useful for HCC detection in patients with a well-conserved liver function reservoir. The decrease in RFA session numbers indicated the utility of Sonazoid in RFA treatment of HCC.

Multimodality non-rigid image registration for planning, targeting and monitoring during CT-guided percutaneous liver tumor cryoablation

RATIONALE AND OBJECTIVES

The aim of this study was to develop non-rigid image registration between preprocedure contrast-enhanced magnetic resonance (MR) images and intraprocedure unenhanced computed tomographic (CT) images, to enhance tumor visualization and localization during CT imaging-guided liver tumor cryoablation procedures.

MATERIALS AND METHODS

A non-rigid registration technique was evaluated with different preprocessing steps and algorithm parameters and compared to a standard rigid registration approach. The Dice similarity coefficient, target registration error, 95th-percentile Hausdorff distance, and total registration time (minutes) were compared using a two-sided Student's t test. The entire registration method was then applied during five CT imaging-guided liver cryoablation cases with the intraprocedural CT data transmitted directly from the CT scanner, with both accuracy and registration time evaluated.

RESULTS

Selected optimal parameters for registration were a section thickness of 5 mm, cropping the field of view to 66% of its original size, manual segmentation of the liver, B-spline control grid of 5 × 5 × 5, and spatial sampling of 50,000 pixels. A mean 95th-percentile Hausdorff distance of 3.3 mm (a 2.5 times improvement compared to rigid registration, P < .05), a mean Dice similarity coefficient of 0.97 (a 13% increase), and a mean target registration error of 4.1 mm (a 2.7 times reduction) were measured. During the cryoablation procedure, registration between the preprocedure MR and the planning intraprocedure CT imaging took a mean time of 10.6 minutes, MR to targeting CT image took 4 minutes, and MR to monitoring CT imaging took 4.3 minutes. Mean registration accuracy was <3.4 mm.

CONCLUSIONS

Non-rigid registration allowed improved visualization of the tumor during interventional planning, targeting, and evaluation of tumor coverage by the ice ball. Future work is focused on reducing segmentation time to make the method more clinically acceptable.

Is percutaneous ethanol injection therapy still effective for hepatocellular carcinoma in the era of radiofrequency ablation?

Percutaneous ethanol injection (PEI) therapy has been replaced by more-effective thermal ablation techniques that have lower local recurrence rates. However, PEI therapy remains useful in certain settings. Since PEI can be performed in any portion of the liver, PEI therapy can be valuable when tumors are located in close proximity to intestinal loops or other positions that are risky for thermal local ablative techniques. PEI therapy is also valuable in other situations where radiofrequency ablation (RFA) is difficult, including technically difficult masses that are not detected with ultrasound (US), are located in the hepatic dome, in the subcapsular area, and exophytically, or are surrounded by large vessels. PEI therapy contributes to combination therapy with transcatheter arterial chemoembolization or RFA in advanced-stage hepatocellular carcinoma (HCC), and also to the treatment of large HCC or extrahepatic metastasis from HCC. These roles of PEI therapy should be stressed for the treatment of HCCs in appropriate clinical situations. This comprehensive review of articles related to PEI therapy illustrates the recent role and indications of this therapy, which is currently valuable for HCC in the era of RFA.

Contrast-enhanced sonography-guided radiofrequency ablation for the local recurrence of previously treated hepatocellular carcinoma undetected by B-mode sonography

BACKGROUND.: The purpose of this study was to assess the usefulness of contrast-enhanced sonography (CEUS) with Sonazoid to demonstrate local recurrence of hepatocellular carcinoma previously treated with radiofrequency ablation (RFA) and not seen on conventional sonography, prior to repeat RFA. METHODS.: This study included 16 cirrhotic patients with 17 cases of hypervascular locally recurrent hepatocellular carcinoma found by contrast-enhanced multidetector row CT (MDCT) but not seen on noncontrast sonography. We used Kupffer-phase imaging and vascular-phase imaging after re-injection. The morphologic patterns of local recurrence detected on CEUS were compared with those on MDCT. We performed repeat RFA guided by CEUS using Kupffer-phase imaging after re-injection. RESULTS.: We were able to detect on CEUS the location of all local recurrences with positive enhancement after re-injection. The morphologic patterns of local recurrence on CEUS were in concordance with those found on MDCT in all lesions. Repeat percutaneous RFA was successfully performed in all lesions. CONCLUSIONS.: The CEUS appearance of local recurrences correlated well with those on MDCT. A wider use of CEUS to guide repeat of percutaneous RFA may be possible with Sonazoid.

Repeat radiofrequency ablation provides survival benefit in patients with intrahepatic distant recurrence of hepatocellular carcinoma

OBJECTIVES

Intrahepatic distant recurrence (IDR) of hepatocellular carcinoma (HCC) after curative treatment occurs frequently and influences the prognoses. The aim of this study was to determine prognostic factors affecting survival after IDR and the optimum therapy for IDR.

METHODS

A total of 115 patients with a single small primary HCC who had complete radiofrequency (RF) ablation were enrolled in this study. The prognostic factors and the optimum therapy affecting survival were statistically analyzed among patients with IDRs.

RESULTS

IDRs were observed in 59 (51.3%) patients with the median observation period of 19.6 months. The cumulative rates of IDRs were 11.8, 53.9, and 75.8% at 1, 3, and 5 years, respectively. IDR nodules were present as a single nodule in 38 patients and as multiple nodules in 21 patients. In all, 23 patients died during the follow-up. A total of 30 patients were treated with RF ablation, and 27 were treated with transcatheter arterial chemoembolization (TACE). The overall cumulative survival rates after IDRs were 92.7, 55.4, and 43.7% at 1, 3, and 5 years, respectively. A multivariate analysis showed that treatment with RF ablation for IDR was a significant favorable prognostic factor after IDR (hazard ratio: 0.167, 95% confidence interval: 0.048-0.584, P=0.005). In a comparison of survival after IDR between patients treated with RF ablation and TACE, who were comparable with clinical and tumoral characteristics, the cumulative survival rate of patients treated with RF ablation was significantly higher than that of those treated with TACE (77.2 vs 28.5% at 3 years). The cumulative survival rates obtained from the initial RF ablation of the patients with IDRs treated with repeat RF ablation were similar to those of recurrence-free patients.

CONCLUSIONS

Repeat RF ablation should be attempted for IDR as much as possible despite tumor multiplicity for survival benefit; by reducing the need, it will help solve the problem of the current shortage of donors for liver transplantations.

Sonazoid-enhanced sonography for guiding radiofrequency ablation for hepatocellular carcinoma: better tumor visualization by Kupffer-phase imaging and vascular-phase imaging after reinjection

PURPOSE

The purpose of this study was to assess the usefulness of contrast harmonic sonography with a newly developed sonographic contrast agent as a means of guidance for percutaneous radiofrequency (RF) ablation of hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

A total of 52 consecutive HCC lesions in 42 patients with HCC who underwent percutaneous RF ablation were included in this study. Altogether, 40 lesions in 35 patients were untreated HCC, and 12 lesions in 7 patients were local tumor progression of an HCC that had already been treated by other methods. We investigated tumors by Kupffer-phase imaging and vascular-phase imaging after reinjection. We performed RF ablation guided by Sonazoid-enhanced sonography using Kupffer-phase imaging and vascular-phase imaging after reinjection.

RESULTS

Conventional sonography identified 30 (57%) of 52 HCCs, whereas Sonazoid-enhanced sonography detected 50 (96%) of 52 HCCs (P < 0.01, McNemar's chi2 test). Complete ablation was achieved at a single session in 48 of 50 tumors.

CONCLUSION

Sonazoid-enhanced sonography is a useful technique for guiding RF ablation of HCCs, even when treating local progression of a previously treated HCC.

Ultrasound-guided treatments under low acoustic power contrast harmonic imaging for hepatocellular carcinomas undetected by B-mode ultrasonography

BACKGROUND/AIMS

The aim was to examine the efficacy of contrast-enhanced ultrasound (US) with Sonazoid to demonstrate ultrasonically unrecognizable hypervascular hepatocellular carcinoma (HCC) and apply percutaneous US-guided treatments.

METHODS

The subjects of this prospective study were 44 cirrhotic patients with 55 hypervascular lesions (12.7+/-4.5 mm) found by contrast-enhanced computed tomography but unrecognized by non-contrast US. Contrast-enhanced US was performed to demonstrate these hepatic lesions after an intravenous injection of Sonazoid (0.0075 ml/kg). The sonograms in both the early phase (for 1 min after injection) and the late phase (5-10 min after) were taken in the harmonic imaging mode under a low mechanical index (0.24-0.3).

RESULTS

Fifty-three lesions were demonstrated by contrast-enhanced US, 52 with positive enhancement in the early phase and 44 with negative enhancement in the late phase. Percutaneous US-guided treatments were successfully performed for 42 lesions (ethanol injection in 20 and radiofrequency ablation in 22) in 32 patients with reference to contrast-enhanced US findings. Six patients were treated by transarterial chemoembolization alone because they had more than three lesions in the liver. In the remaining seven lesions in six patients, six were diagnosed as non-HCC lesions: five with vascular abnormalities such as arterioportal or arteriovenous communication and the other one with benign lesion in alcoholic liver disease. These six lesions and one HCC lesion with severe liver damage were followed up without any treatment.

CONCLUSIONS

As the detectability of ultrasonically unrecognizable hypervascular HCC improved by contrast-enhanced US with Sonazoid, a wider application of percutaneous US-guided treatments may be possible.

Radiofrequency ablation assisted by real-time virtual sonography and CT for hepatocellular carcinoma undetectable by conventional sonography

Real-time virtual sonography (RVS) is a diagnostic imaging support system, which provides the same cross-sectional multiplanar reconstruction images as ultrasound images on the same monitor screen in real time. The purpose of this study was to evaluate radiofrequency ablation (RFA) assisted by RVS and CT for hepatocellular carcinoma (HCC) undetectable with conventional sonography. Subjects were 20 patients with 20 HCC nodules not detected by conventional sonography but detectable by CT or MRI. All patients had hepatitis C-induced liver cirrhosis; there were 13 males and 7 females aged 55-81 years (mean, 69.3 years). RFA was performed in the CT room, and the tumor was punctured with the assistance of RVS. CT was performed immediately after puncture, and ablation was performed after confirming that the needle had been inserted into the tumor precisely. The mean number of punctures and success rates of the first puncture were evaluated. Treatment effects were evaluated with dynamic CT every 3 months after RFA. RFA was technically feasible and local tumor control was achieved in all patients. The mean number of punctures was 1.1, and the success rate of the first puncture was 90.0%. This method enabled safe ablation without complications. The mean follow-up period was 13.5 month (range, 9-18 months). No local recurrence was observed at the follow-up points. In conclusion, RFA assisted by RVS and CT is a safe and efficacious method of treatment for HCC undetectable by conventional sonography.

Current role of ultrasound for the management of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) has a decisive influence on the prognosis of cirrhotic patients. Although α-fetoprotein (AFP) is a known and specific tumor maker for HCC, it is not suitable for the screening and surveillance of HCC because of its poor predictive value and low sensitivity. The use of imaging modalities is essential for the screening, diagnosis and treatment of HCC. Ultrasound (US) plays a major role among them, because it provides real-time and non-invasive observation by a simple and easy technique. In addition, US-guided needle puncture methods are frequently required for the diagnosis and/or treatment process of HCC. The development of digital technology has led to the detection of blood flow by color Doppler US, and the sensitivity for detecting tumor vascularity has shown remarkable improvement with the introduction of microbubble contrast agents. Moreover, near real-time 3-dimensional US images are now available. As for the treatment of HCC, high intensity focused ultrasound (HIFU) was developed as a novel technology that provides a transcutaneous ablation effect without needle puncture. These advancements in the US field have led to rapid progress in HCC management, and continuing advances are expected. This article reviews the current application of US for HCC in clinical practice.

Carbon dioxide microbubbles-enhanced sonographically guided radiofrequency ablation: treatment of patients with local progression of hepatocellular carcinoma

PURPOSE

The aim of our study was to evaluate the usefulness of percutaneous radiofrequency ablation (RFA) using CO2 microbubbles-enhanced sonography for patients with local tumor progression of hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

The tumors of 14 patients with local progression of HCC were treated with CO2 microbubbles-enhanced RFA ablation via a catheter that had been placed in the hepatic artery. We assessed tumor detectability and technical effectiveness. The mean follow-up period was 14.1 months.

RESULTS

Only 6 of the tumors could be found on conventional sonography, whereas 14 tumors were detected on CO2 microbubbles-enhanced sonography. These 14 lesions were successfully treated with RFA guided by CO2 microbubbles-guided sonography. Technical effectiveness was complete in all patients. No serious complications were observed, and there was no local tumor progression during the follow-up period.

CONCLUSION

RFA guided by CO2 microbubbles-guided sonography is a feasible technique for treating local progression of HCC lesions that cannot be adequately depicted by conventional sonography.

Application of a new combined guiding technique in RF ablation of subphrenic liver tumors

We present an unreported technique used to treat with RF ablation hepatic subphrenic hepatocellular carcinoma. It consists in the combination of fluoroscopic and computed tomography guidance for lesions already embolized with lipiodol located at the hepatic dome, approached in parallel fashion with a 22-gauge chiba "finder" needle followed by the RF electrode.

Application of percutaneous ultrasound-guided treatment for ultrasonically invisible hypervascular hepatocellular carcinoma using microbubble contrast agent

AIM

To evaluate the efficacy of contrast-enhanced ultrasound for the localization of ultrasonically invisible hypervascular lesions in the liver to facilitate percutaneous ultrasound-guided treatment.

MATERIALS AND METHODS

Forty patients with 47 ultrasonically invisible hypervascular lesions (5-20mm) diagnosed on contrast-enhanced computed tomography were enrolled in the retrospective study. Contrast-enhanced ultrasound (CEUS) with Levovist was performed to localize the lesions both in the early phase and liver-specific phase. Diagnosis of was confirmed by percutaneous needle biopsy where feasible, and on the basis of on treatment outcomes or changes in computed tomography findings in those not amenable to biopsy.

RESULTS

Thirty-two lesions were diagnosed as hepatocellular carcinoma (HCC). Contrast-enhanced ultrasound localized hepatocellular carcinoma in 24/32 (75%) lesions, the mean diameter (15.1+/-4.9mm), as measured using computed tomography, being significantly larger than that of the remaining eight lesions (10.5+/-2.1mm). Ultrasound-guided treatment was performed in 19 of the 24 lesions, and transarterial chemoembolization (TACE) was applied for the other five lesions because of difficult percutaneous access. Five of the eight non-visualised lesions were treated by transarterial chemoembolization, and the other three by surgical resection. The beneficial effect of CEUS was significantly greater when the reason for poor initial visualisation was the coarse liver architecture (17/17) than when it was due to adverse location (seven of 15, p<0.005). Fifteen of the CT-detected hypervascular lesions were considered to represent false positives for HCC, based on their behaviour during follow-up.

CONCLUSION

Contrast-enhanced ultrasound with Levovist facilitates the application of percutaneous ultrasound-guided treatment by improving localization of ultrasonically invisible hypervascular hepatocellular carcinomas in the liver.

Percutaneous ultrasound-guided radiofrequency ablation of hepatocellular carcinoma with artificially induced pleural effusion and ascites

BACKGROUND

Ultrasound-guided procedures are sometimes of limited use because the tumor is located under the diaphragm or near the surface of the liver. We investigated the safety and efficacy of radiofrequency ablation (RFA) with artificial pleural effusion and/or artificial ascites.

METHODS

Between January 2002 and May 2006, 43 lesions in 36 patients with hepatocellular carcinoma (HCC) were treated by RFA with artificial pleural effusion and/or artificial ascites.

RESULTS

Artificial pleural effusion allowed visualization of the whole tumor for 36 (83.7%) of the 43 lesions that were otherwise not detectable or poorly visible. Artificial ascites was also helpful in visualizing whole tumors that could not be visualized with only artificial pleural effusion. In all lesions, artificial pleural effusion and/or artificial ascites were helpful in performing percutaneous RFA. Artificial ascites was useful for creating a space between the liver's surface and the skin or diaphragm to avoid burns. Adverse effects after the induction of artificial pleural effusion included pneumonia in one patient and temporary atelectasis in another patient. Severe side effects were not observed. Complete necrosis after RFA was obtained in 43 (100%) of the 43 lesions. During a mean follow-up period of 31.8 +/- 5.8 months, local recurrence at the ablation site was found in none of the 43 lesions.

CONCLUSIONS

Percutaneous RFA with artificial pleural effusion and/or artificial ascites was a safe and useful treatment that resulted in good local control of HCC.

Efficacy and safety of radiofrequency ablation of hepatocellular carcinoma in the hepatic dome with the CT-guided extrathoracic transhepatic approach

PURPOSE

The purpose of this study was to determine the efficacy and safety of radiofrequency (RF) ablation for the treatment of hepatocellular carcinoma (HCC) in the hepatic dome with CT-guided extrathoracic transhepatic approach.

MATERIALS AND METHODS

Fifteen patients with 15 HCCs (size range: 0.8-4 cm, mean size: 1.8 cm) in the hepatic dome were treated by RF ablation using cooled-tip electrodes and with CT-guided extrathoracic transhepatic approach. Therapeutic response of the tumor to RF ablation and procedure-related complications including hepatic injury, hemoperitoneum, and thermal injury of diaphragm were evaluated.

RESULTS

The average number of needle punctures to ensure the correct needle position in the targeted tumor was 3.7 (range: 1-6 punctures). The average ablation time was 14.7 min (range: 8-25 min). Complete necrosis without marginal recurrence after at least 13-month follow-up was attained in 13 tumors (86.7%). There were no major complications related to the procedures. Six patients had shoulder pain that lasted three days to two weeks after the procedures and their symptoms were resolved with conservative treatment.

CONCLUSIONS

RF ablation using CT-guided extrathoracic transhepatic approach is an effective and safe technique for the treatment of HCC in the hepatic dome.

Virtual Sonographic Radiofrequency Ablation of Hepatocellular Carcinoma Visualized on CT but Not on Conventional Sonography

OBJECTIVE

Some nodules cannot be visualized clearly on conventional sonography but can be visualized on CT. In the present study, we evaluated the usefulness of real-time percutaneous ablation therapy under virtual sonographic guidance for these nodules.

SUBJECTS AND METHODS

In vitro experiments were performed with gelatin gel to evaluate the accuracy of virtual sonography. We also studied 50 patients with 58 hepatocellular carcinoma nodules, of whom 18 patients (21 nodules) underwent radiofrequency ablation by virtual sonography. This was the initial treatment for seven of these patients and an additional treatment for 11 patients. Thirty-two patients (37 nodules) received radiofrequency ablation without virtual imaging. The patients receiving standard radiofrequency ablation were retrospectively selected as the historical control group under the same conditions as the study group.

RESULTS

The in vitro gelatin gel study revealed that all punctures had been performed accurately. In both the initial-treatment group and the additional-treatment group, the mean number of treatments with virtual sonography was significantly lower than that without virtual sonography (p = 0.003 for both groups). The rates of local recurrence and complications did not differ significantly between the two groups.

CONCLUSION

In the treatment of nodules not depicted on sonography, radiofrequency ablation assisted by virtual sonography is an efficacious alternative.

Local therapeutic treatments for focal liver disease

Patients diagnosed with primary hepatic malignancies or metastases to the liver remain a difficult population to treat. A small percentage of these people can undergo surgical resection or transplantation. The remaining nonsurgical aggregate does not often benefit from conventional radiation and chemotherapy; minimally invasive means either to cure or palliate these patients are a requirement for complete cancer care. This article discusses image-guided local therapies used to treat this difficult patient population, focusing predominantly on radiofrequency ablation.

Disruption of erythrocytes distinguishes fixed cells/tissues from viable cells/tissues following microwave coagulation therapy

Microwave coagulation therapy (MCT) has recently been applied to treat hepatic tumors. However, the histological changes in the liver following MCT have not been fully elucidated. A type of cell death known as microwave fixation has been reported in areas adjacent to the microwave irradiator electrodes, and these areas are without acid phosphatase (AcP) activity. Diagnosis of microwave-fixed tissue by hematoxylin and eosin (HE) staining is very difficult because morphology is well maintained for months. In an effort to clarify the histological changes and the mechanisms of microwave fixation, we performed HE staining, enzyme histochemistry for AcP, and electron microscopy in both rat and human liver samples after MCT. Although the microwave-fixed tissues maintained their structure on HE staining, membranes of microwave-fixed cells were seriously damaged and there were no apparent organelle structures in these cells on electron microscopy. Erythrocytes were also damaged in these tissues on both light and electron microscopy. The cause of microwave fixation is thought to be injury of the membrane, which is similar to coagulative necrosis. In conclusion, microwave fixation can be considered a type of coagulative necrosis without enzyme digestion. Disruption of erythrocytes on HE staining is an interesting and important diagnostic clue in distinguishing nonviable fixed tissues from viable tissues following MCT.

Transthoracic percutaneous radiofrequency ablation for liver tumors in the hepatic dome

Computed tomography (CT)-guided transthoracic radiofrequency ablation was performed for nine liver tumors of eight patients, which were located in the hepatic dome and undetectable by ultrasound (US). A total 11 sessions of ablation were performed. Complications were noted in five sessions (45%) and no complications were noted in six sessions (55%). Pneumothorax was noted in five sessions (45%), including two sessions (18%) with major pneumothorax requiring a chest tube. Major complications were seen in two sessions (18%), major pneumothorax and both major pneumothorax and moderate pleural effusion, respectively. CT-guided transthoracic radiofrequency ablation may be an alternative for treatments of liver tumor in the hepatic dome.

Treatment of hepatocellular carcinoma with percutaneous radiofrequency ablation: usefulness of contrast harmonic sonography for lesions poorly defined with B-mode sonography

OBJECTIVE

The purpose of this study was to assess the usefulness of contrast harmonic sonography guidance in percutaneous radiofrequency ablation of hepatocellular carcinomas that could not be adequately depicted by B-mode sonography. SUBJECTS AND METHODS. Twenty-one patients with 21 hepatocellular carcinomas prospectively underwent radiofrequency ablation treatment with contrast harmonic sonography as guidance. Twenty-five patients with 25 hepatocellular carcinomas were retrospectively selected as the historical control group under the same conditions as the study group; the control group patients were treated under B-mode sonography guidance.

RESULTS

Twenty (95.2%) of the 21 patients were successfully treated during a single treatment session, and the remaining patient (4.8%) required two treatment sessions with contrast harmonic guidance. On the other hand, only eight (32%) of the 25 control subjects were successfully treated during a single treatment session using B-mode sonographic guidance without contrast imaging. The difference between these two groups was statistically significant (p = 0.002).

CONCLUSION

Contrast harmonic sonography helps in the placement of radiofrequency ablation electrodes in hypervascular hepatocellular carcinomas that cannot be adequately depicted by B-mode sonography.

Other thermal ablation techniques: microwave and interstitial laser ablation of liver tumors

BACKGROUND

Thermal ablation of hepatic malignancies is becoming a widespread treatment approach. In addition to radiofrequency ablation, microwave coagulation (MCT) and laser-induced interstitial thermotherapy (LITT) are being used clinically to treat patients with liver cancers.

METHODS

The principles and clinical indications for MCT and LITT are described. Treatment approaches and results from published clinical studies are reviewed. The evolution of these thermal treatment modalities and limitations of currently available equipment is provided.

RESULTS

The interstitial probes and equipment used for MCT and LITT for liver tumors are undergoing changes to improve treatment efficacy. Both MCT and LITT have been limited by the relatively small zone of coagulation produced with a single probe placement. Both techniques can be performed safely, and local recurrence and long-term survival rates are being established.

CONCLUSIONS

MCT and LITT are two alternative thermal ablation techniques being used to treat patients with primary and metastatic hepatic malignancies. The utility of these two treatments has been limited by the relatively small area of thermal necrosis produced around the interstitial probes, but design modifications and new equipment may improve these limitations.

Chemical-shift MR imaging of acetic acid during percutaneous chemical ablation therapy: preliminary work

The purpose of this study was to test the hypothesis that chemical-shift magnetic resonance (MR) imaging may be used to map the distribution of acetic acid during percutaneous chemical ablation procedures. Chemical-shift MR imaging was performed with use of standard methods on a 1.5-T scanner. Phantom and ex-vivo data demonstrated focal increases in the observed signal in chemical-shift MR imaging that correlate well with the site of injection. Preliminary study in a patient with hepatoma revealed focal signal at the injection site. These preliminary results suggest that chemical-shift MR imaging may be used to visualize acetic acid distribution during percutaneous chemical ablation procedures.

CT-guided transthoracic percutaneous ethanol injection for hepatocellular carcinoma not detectable with US

PURPOSE

To evaluate the safety and effectiveness of computed tomography (CT)-guided percutaneous ethanol injection (PEI) for the treatment of hepatocellular carcinoma (HCC) not detectable with ultrasonography (US).

MATERIALS AND METHODS

Between April 1994 and January 2001, 51 patients with 57 HCC nodules not detectable with US underwent CT-guided transthoracic PEI. Complications associated with the transthoracic approach, effectiveness of transthoracic PEI, and prognosis of the patients were evaluated.

RESULTS

Seventy-one PEI sessions were performed for 57 nodules. Complications included pneumothorax in 21 sessions (30%) for 19 nodules (33%), moderate pleural effusion in four sessions (6%) for four nodules (7%), and hemoptysis in three sessions (4%) for two nodules (4%). A chest tube was required for pneumothorax in five sessions (7%) for five nodules (9%), and pleural effusion drainage was performed in two sessions (3%) for two nodules (4%). Apparent tumor necrosis was noted at CT in 51 nodules (89%). During follow-up (range, 3 months to 5(1/2) years; mean, 29 months +/- 18 [SD]), local recurrence was seen in seven nodules (12%), three of which received repeat treatment with transthoracic PEI. Twenty-six patients survived, and 25 patients died of multiple tumors, hepatic failure, or rupture of esophageal varices.

CONCLUSION

Transthoracic PEI seems to be relatively safe and effective for the treatment of HCC not detectable with US.

Percutaneous ethanol injection therapy for liver tumors

Percutaneous ethanol injection therapy (PEIT) has been widely practiced in the treatment of liver tumors, especially of hepatocellular carcinoma (HCC). Histopathologic examinations, findings in imaging modalities and serum tumor marker levels have shown a remarkable anticancer effect of this procedure. In addition, PEIT has achieved considerably high long-term survival rates. For small HCC, PEIT has been generally accepted as an alternative to surgery. Here we will describe PEIT from the viewpoints of patient selection, technique, various evaluation procedures of efficacy, long-term results, side effects and complications, and relationship with other therapies.