Treatment of intrahepatic malignancy with radiofrequency ablation

Intra-articular temperature monitoring during radiofrequency ablation in ex-vivo bovine hip joints via Fiber Bragg grating sensors

PURPOSE

Radiofrequency ablation is an increasingly used surgical option for ablation, resection and coagulation of soft tissues in joint arthroscopy. One of the major issues of thermal ablation is the temperature monitoring across the target areas, as cellular mortality is a direct consequence of thermal dosimetry. Temperatures from 45 °C to 50 °C are at risk of damage to chondrocytes. One of the most reliable tools for temperature monitoring is represented by fiber optic sensors, as they allow accurate and real-time temperature measurement via a minimally invasive approach. The aim of this study was to determine, by fiber Bragg grating sensors (FBGs), the safety of radiofrequency ablation in tissue heating applied to ex-vivo bovine hip joints.

METHODS

Ex vivo bovine hips were subjected to radiofrequency ablation, specifically in the acetabular labrum, for a total of two experiments. The WEREWOLF System (Smith + Nephew, Watford, UK) was employed in high operating mode and in a controlled ablation way. One optical fiber embedding seven FBGs was used to record multipoint temperature variations. Each sensor was 1 mm in length with a distance from edge to edge with each other of 2 mm.

RESULTS

The maximum variation was recorded in both the tests by the FBG1 (i.e., the closest one to the electrode tip) and was lower than to 2.8 °C. The other sensors (from FBG2 to FBG7) did not record a significant temperature change throughout the duration of the experiment (maximum up to 0.7 °C for FBG7).

CONCLUSIONS

No significant increase in temperature was observed at any of the seven sites. The sensor nearest to the radiofrequency source exhibited the highest temperature rise, but the variation was only 3 °C. The minimal temperature increase registered at the measurement sites, according to existing literature, is not expected to be cytotoxic. FBGs demonstrate the potential to fulfil the strict requirements for temperature measurements during arthroscopic surgery.

Percutaneous Ablation of T1 Renal Masses: Comparative Local Control and Complications after Radiofrequency and Cryoablation

The efficacy and complication rates of percutaneous radiofrequency ablation (RFA) and cryoablation (CA) in the treatment of T1 renal masses in two Northern Italy hospitals were retrospectively investigated. Eighty-two patients with 80 T1a tumors and 10 T1b tumors treated with thermal ablation from 2015 through 2020 were included. A total of 43 tumors in 38 patients were treated with RFA (2.3 ± 0.9 cm), and 47 tumors in 44 patients were treated with CA (2.1 ± 0.8 cm). The mean follow-up observation period was 26 ± 19 months. The major complications and efficacy, as measured using the technical success and local tumor recurrence rates, were recorded. There were three (6.9%) technical failures with RFA and one (2.1%) with cryoablation (p = 0.30). Among the 40 tumors that were successfully treated with RFA, 1 tumor (2.5%) developed local tumor recurrence; 5/46 tumors that were treated with cryoablation (10.8%) developed local tumor recurrence (p = 0.17). T1b lesions (4.0 ± 0.7 cm) resulted in 1/6 technically unsuccessful cases with RFA and 0/4 with CA. No recurrent disease was detected in the T1b lesions. Major complications occurred after 2.3% (1/43) of RFAs and 0/47 of cryoablation procedures. RFA and cryoablation are both effective in the treatment of renal masses. Major complications with either procedure are uncommon.

Feasibility of the chick chorioallantoic membrane model for preclinical studies on tumor radiofrequency ablation

BACKGROUND

We evaluated the feasibility of a chick chorioallantoic membrane (CAM) tumor model for preclinical research on tumor radiofrequency ablation (RFA).

METHODS

Fertilized chicken eggs were incubated and divided into five cohorts: RFA for 30 s (n = 5), RFA for 60 s (n = 5), RFA for 120 s (n = 4), sham (n = 8), and controls (n = 6). Xenografting using pancreatic neuroendocrine tumor cells of the BON-1 cell line was performed on embryonic day (ED) 8. The RFA was performed on ED 12. Survival, stereomicroscopic observations, and histological observations using hematoxylin-eosin (H&E) and Ki67 staining were evaluated.

RESULTS

The survival rates in the 30-s, 60-s, and 120-s, sham and control cohort were 60%, 60%, 0%, 100%, and 50%, respectively. Signs of bleeding and heat damage were common findings in the evaluation of stereomicroscopic observations. Histological examination could be performed in all but one embryo. Heat damage, bleeding, thrombosis, and leukocyte infiltration and hyperemia were regular findings in H&E-stained cuts. A complete absence of Ki67 staining was recorded in 33.3% and 50% of embryos in the 30-s and 60-s cohorts that survived until ED 14, respectively.

CONCLUSIONS

The CAM model is a feasible and suiting research model for tumor RFA with many advantages over other animal models. It offers the opportunity to conduct in vivo research under standardized conditions. Further studies are needed to optimize this model for tumor ablations in order to explore promising but unrefined strategies like the combination of RFA and immunotherapy.

RELEVANCE STATEMENT

The chick chorioallantoic membrane model allows in vivo research on tumor radiofrequency ablation under standardized conditions that may enable enhanced understanding on combined therapies while ensuring animal welfare in concordance with the "Three Rs."

KEY POINTS

• The chorioallantoic membrane model is feasible and suiting for tumor radiofrequency ablation. • Radiofrequency ablation regularly achieved reduction but not eradication of Ki67 staining. • Histological evaluation showed findings comparable to changes in humans after RFA. • The chorioallantoic membrane model can enable studies on combined therapies after optimization.

A nationwide propensity score analysis comparing ablation and resection for hepatocellular carcinoma

BACKGROUND AND OBJECTIVES

Studies have reported ambiguous results regarding the efficacy of ablation for early-stage hepatocellular carcinoma (HCC). Our study compared outcomes of ablation versus resection for HCC ≤50 mm to identify tumor sizes that would most benefit from ablation in terms of long-term survival.

METHODS

The National Cancer Database was queried for patients with stage I and II HCC ≤50 mm who underwent ablation or resection (2004-2018). Three cohorts were created based on tumor size: ≤20, 21-30, and 31-50 mm. A propensity score-matched survival analysis was performed using the Kaplan-Meier method.

RESULTS

In total, 36.47% (n = 4263) and 63.53% (n = 7425) of patients underwent resection and ablation, respectively. After matching, resection was associated with a significant survival benefit compared to ablation (3-year survival: 78.13% vs. 67.64%; p < 0.0001) in patients with HCC of ≤20 mm. The impact of resection was even more striking among patients with HCC of 21-30 mm (3-year survival: 77.88% vs. 60.53%; p < 0.0001) and 31-50 mm (3-year survival: 67.21% vs. 48.55%; p < 0.0001).

CONCLUSIONS

While resection offers a survival benefit over ablation in the treatment of early-stage HCC ≤50 mm, ablation may provide a feasible bridging strategy in patients awaiting transplantation.

The latest research progress on minimally invasive treatments for hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is the fourth leading cause of cancer-related death worldwide. Due to the high prevalence of hepatitis B virus (HBV) infection in China, the incidence of HCC in China is high, and liver cirrhosis caused by chronic hepatitis also brings great challenges to treatment. This paper reviewed the latest research progress on minimally invasive treatments for HCC, including percutaneous thermal ablation and new nonthermal ablation techniques, and introduced the principles, advantages, and clinical applications of various therapeutic methods in detail.

DATA SOURCES

The data of treatments for HCC were systematically collected from the PubMed, ScienceDirect, American Chemical Society and Web of Science databases published in English, using "minimally invasive" and "hepatocellular carcinoma" or "liver cancer" as the keywords.

RESULTS

Percutaneous thermal ablation is still a first-line strategy for the minimally invasive treatment of HCC. The effect of microwave ablation (MWA) on downgrading treatment before liver transplantation is better than that of radiofrequency ablation (RFA), while RFA is more widely used in the clinical practice. High-intensity focused ultrasound (HIFU) is mainly used for the palliative treatment of advanced liver cancer. Electrochemotherapy (ECT) delivers chemotherapeutic drugs to the target cells while reducing the blood supply around HCC. Irreversible electroporation (IRE) uses a microsecond-pulsed electric field that induces apoptosis and necrosis and triggers a systemic immune response. The nanosecond pulsed electric field (nsPEF) has achieved a good response in the ablation of mice with HCC, but it has not been reported in China for the treatment of human HCC.

CONCLUSIONS

A variety of minimally invasive treatments provide a sufficient survival advantage for HCC patients. Nonthermal ablation will lead to a new wave with its unique advantage of antitumor recurrence and metastasis.

Predictors of metastasis in cervical indeterminate lymph nodes after thyroid cancer ablation by long-term ultrasound follow-up

OBJECTIVES

To investigate the pattern of change over time and predictors for metastasis in indeterminate lymph nodes (LNs) among patients with thyroid cancer post-ablation.

METHODS

We enrolled patients who developed new cervical LNs after papillary thyroid carcinoma (PTC) ablation. Changes in the ultrasound characteristics of the indeterminate LN were recorded at months 1, 3, 6 and 12 after ablation. LN puncture pathology and long-term follow-up were standard of diagnosis. The indeterminate LNs were divided into benign and malignant groups, the differences between the two groups were compared, and the risk characteristics of malignant LNs were screened using generalized estimating equations (GEE).

RESULTS

In total, we included 138 LNs from 99 patients, of which 48 were indeterminate LNs. When following up indeterminate LNs, non-cervical lymph node metastasis (non-CLNM) lesions demonstrated a statistically significant gradual decrease in volume (p = 0.012), though there was no significant change in the volume of CLNM lesions (p = 0.779). Compared to non-CLNM lesions, the diagnostic efficiency was the highest for CLNM lesions at 1-3 months after ablation, when the LN volume changed by -0.08 to 0.12 mL (p = 0.048). The third month after ablation became an important time point for review. Moreover, GEE analysis showed that microcalcifications, cystic changes, and vascularity were strongly associated with CLNMs (p = 0.004, p = 0.002, and p = 0.010, respectively).

CONCLUSIONS

There is a pattern of volume change of indeterminate LNs after PTC ablation, which, together with microcalcifications, cystic changes, and vascularity, can be used as criteria for differentiating the benignity and malignancy of indeterminate LNs.

Radio Frequency Ablation for the Treatment of Appendicular Skeleton Chondroblastoma: Is It an Excellent Alternative? Systematic Review and Meta-Analysis

Radio frequency ablation (RFA) is a minimally invasive technique that has become recognized in clinical practice for treating chondroblastoma, although curettage with bone graft is the standard treatment. Chondroblastoma is a locally aggressive cartilaginous bone tumor, representing nearly 5% of benign bone tumors. Chondroblastoma shows a preference toward the epiphysis or apophysis of long bones, but it was also reported in vertebrae and flat bones. The management of chondroblastoma could be challenging due to the risk to injure the epiphyseal plate or difficult location. The aim of this study was to determine if RFA is a suitable alternative to curettage with bone graft for the treatment of chondroblastoma. Moreover, there will be an evaluation of RFA's effectiveness in terms of symptoms relief; we also define the proper size of the lesion to be treated with RFA, and discuss the complications after the procedure, including the recurrence rate. Furthermore, we review the best imaging method to evaluate the therapeutic response of RFA and for the detection of residual disease early after the ablation. A comprehensive PubMed and Google Scholar search followed the Preferred Reporting Items for Systematic Review and Meta-Analysis 2020 checklist guidelines. Ninety-seven patients were identified after reviewing the available full texts of nine articles. The results of the current review provide further evidence to support the use of RFA as an alternative option to surgery.

Update on Percutaneous Local Ablative Procedures for the Treatment of Hepatocellular Carcinoma

BACKGROUND

 Hepatocellular carcinoma (HCC) is the fifth most common tumor worldwide. Because many hepatocellular carcinomas are already unresectable at the time of initial diagnosis, percutaneous tumor ablation has become established in recent decades as a curative therapeutic approach for very early (BCLC 0) and early (BCLC A) HCC. The aim of this paper is to provide a concise overview of the percutaneous local ablative procedures currently in use, based on their technical characteristics as well as clinical relevance, taking into account the current body of studies.

MATERIALS AND METHODS

 The literature search included all original papers, reviews, and meta-analyses available via MEDLINE and Pubmed on the respective percutaneous ablation procedures; the primary focus was on randomized controlled trials and publications from the last 10 years.

RESULTS AND CONCLUSIONS

 Radiofrequency ablation (RFA) and microwave ablation (MWA) are well-established procedures that are considered equal to surgical resection in the treatment of stage BCLC 0 and A HCC with a diameter up to 3 cm due to their strong evidence in international and national guidelines. For tumors with a diameter between 3 and 5 cm, the current S3 guidelines recommend a combination of transarterial chemoembolization (TACE) and thermal ablation using RFA or MWA as combination therapy is superior to thermal ablation alone in tumors of this size and shows comparable results to surgical resection in terms of overall survival. Alternative, less frequently employed thermal procedures include cryotherapy (CT) and laser ablation (LA). Non-thermal procedures include irreversible electroporation (IRE), interstitial brachytherapy (IBT), and most recently, electrochemotherapy (ECT). Due to insufficient evidence, these have only been used in individual cases and within the framework of studies. However, the nonthermal methods are a reasonable alternative for ablation of tumors adjacent to large blood vessels and bile ducts because they cause significantly less damage to these structures than thermal ablation methods. With advances in the technology of the respective procedures, increasingly good evidence, and advancements in supportive techniques such as navigation devices and fusion imaging, percutaneous ablation procedures may expand their indications for the treatment of larger and more advanced tumors in the coming years.

KEY POINTS

· RFA and MWA are considered equal to surgical resection as a first-line therapy for the curative treatment of stage BCLC 0 and A HCCs with a diameter of up to 3 cm.. · For HCCs with a diameter between 3 and 5 cm, a combination of TACE and RFA or MWA is recommended. This combination therapy yields results comparable to those of surgical resection in terms of overall survival.. · Due to insufficient evidence, alternative ablation methods have only been used in individual cases and within the framework of studies. However, nonthermal methods, such as IRE, IBT, and, most recently, ECT, are a reasonable alternative for ablation of HCCs adjacent to large blood vessels and bile ducts because they cause significantly less damage to these structures than thermal ablation methods..

CITATION FORMAT

· Luerken L, Haimerl M, Doppler M et al. Update on Percutaneous Local Ablative Procedures for the Treatment of Hepatocellular Carcinoma. Fortschr Röntgenstr 2022; DOI: 10.1055/a-1768-0954.

Radiofrequency-assisted transection of the pancreas vs stapler in distal pancreatectomy: a propensity score matched cohort analysis

To demonstrate the efficacy of radiofrequency for pancreatic stump closure in reducing the incidence of postoperative pancreatic fistula (POPF) in distal pancreatectomy (DP) compared with mechanical transection methods. Despite all the different techniques of pancreatic stump closure proposed for DP, best practice for avoiding POPF remains an unresolved issue, with an incidence of up to 30% regardless of center volume or surgical expertise. DP was performed in a cohort of patients by applying radiofrequency to stump closure (RF Group) and compared with mechanical closure (Control Group). A propensity score (PS) matched cohort study was carried out to minimize bias from nonrandomized treatment assignment. Cohorts were matched by PS accounting for factors significantly associated with either undergoing RF transection or mechanical closure through logistic regression analysis. The primary end-point was the incidence of clinically relevant POPF (CR-POPF). Of 89 patients included in the whole cohort, 13 case patients from the RF-Group were 1:1 matched to 13 control patients. In both the first independent analysis of unmatched data and subsequent adjustment to the overall propensity score-matched cohort, a higher rate of CR-POPF in the Control Group compared with the RF-Group was detected (25.4% vs 5.3%, p = 0.049 and 53.8% vs 0%; p = 0.016 respectively). The RF Group showed better outcomes in terms of readmission rate (46.2% vs 0%, p = 0.031). No significant differences were observed in terms of mortality, major complications (30.8% vs 0%, p = 0.063) or length of hospital stay (5.7 vs 5.2 days, p = 0.89). Findings suggest that the RF-assisted technique is more efficacious in reducing CR-POPF than mechanical pancreatic stump closure.

Immunofluorescence Assay of Ablated Colorectal Liver Metastases: The Frozen Section of Image-Guided Tumor Ablation?

PURPOSE

To validate an immunofluorescence assay (IFA) detecting residual viable tumor (VT) as intraprocedural thermal ablation (TA) zone assessment and demonstrate its prognostic value for local tumor progression (LTP) after colorectal liver metastasis (CLM) TA.

MATERIALS AND METHODS

This prospective study, approved by the institutional review board, included 99 patients with 155 CLMs ablated between November 2009 and January 2019. Tissue samples from the ablation zone (AZ) center and minimal margin underwent immunofluorescent microscopic examination interrogating cellular morphology and mitochondrial viability (IFA) within 30 minutes after ablation. The same tissue samples were subsequently evaluated with standard morphologic and immunohistochemical methods. The sensitivity, specificity, and overall accuracy of IFA versus standard morphologic and immunohistochemical examination were calculated. The LTP-free survival rates were evaluated for the 12-month follow-up period.

RESULTS

Of the 311 tissue samples stained, 304 (98%) were deemed evaluable. Of these specimens, 27% (81/304) were considered positive for the presence of VT. The accuracy of IFA was 94% (286/304). The sensitivity and specificity were 100% (63/63) and 93% (223/241), respectively. The 18 false-positive IFA assessments corresponded to samples that included viable cholangiocytes. The 12-month LTP-free survival was 59% versus 78% for IFA positive versus negative for VT AZs, respectively (P < .001). There was no difference in LTP between margin positive only and central AZ-positive tumors (25% vs 31%, P = 1).

CONCLUSIONS

The IFA assessment of the AZ can be completed intraprocedurally and serve as a valid real-time biomarker of complete tumor eradication or detect residual VT after TA. This method could improve tumor control by TA.

Biopsy and Margins Optimize Outcomes after Thermal Ablation of Colorectal Liver Metastases

Simple Summary

Thermal ablation (TA) is a non-surgical treatment of cancer that has been used with success in the treatment of colorectal liver metastases (CLM). TA consists of burning the cancer and a rim of surrounding tissue (margin) with a special needle placed in the tumor under image guidance. Despite the technological evolution of TA, tumor progression/recurrence rates remain higher than expected. We present a method that combines tissue and imaging tests performed immediately after ablation to determine whether there is complete tumor destruction or remaining live cancer cells that can cause tumor progression/recurrence. This information can provide guidance for additional treatments for patients with evidence of residual cancer, i.e.,: additional TA at the same or subsequent sitting, or additional chemotherapy and short-interval imaging follow-up to detect recurrence. The presented method proposes a clinical practice paradigm change that can improve clinical outcomes in a large population of patients with CLM treated by TA.

Abstract

Background: Thermal ablation is a definitive local treatment for selected colorectal liver metastases (CLM) that can be ablated with adequate margins. A critical limitation has been local tumor progression (LTP). Methods: This prospective, single-group, phase 2 study enrolled patients with CLM < 5 cm in maximum diameter, at a tertiary cancer center between November 2009 and February 2019. Biopsy of the ablation zone center and margin was performed immediately after ablation. Viable tumor in tissue biopsy and ablation margins < 5 mm were assessed as predictors of 12-month LTP. Results: We enrolled 107 patients with 182 CLMs. Mean tumor size was 2.0 (range, 0.6–4.6) cm. Microwave ablation was used in 51% and radiofrequency ablation in 49% of tumors. The 12- and 24-month cumulative incidence of LTP was 22% (95% confidence interval [CI]: 17, 29) and 29% (95% CI: 23, 36), respectively. LTP at 12 months was 7% (95% CI: 3, 14) for the biopsy tumor-negative ablation zone with margins ≥ 5 mm vs. 63% (95% CI: 35, 85) for the biopsy-positive ablation zone with margins < 5 mm (p < 0.001). Conclusions: Biopsy-proven complete tumor ablation with margins of at least 5 mm achieves optimal local tumor control for CLM, regardless of the ablation modality used.

Dynamic nanoassemblies of nanomaterials for cancer photomedicine

Photomedicine has long been used for treating cancerous diseases. With advances in chemical and material sciences, various types of light-activated photosensitizers (PSs) have been developed for effective photodynamic therapy (PDT) and photothermal therapy (PTT). However, conventional organic/inorganic materials-based PSs lack disease recognition capability and show limited therapeutic effects in addition to side effects. Recently, intelligent dynamic nanoassemblies that are activated in a tumor environment have been extensively researched to target diseased tissues more effectively, for increasing therapeutic effectiveness while minimizing side effects. This paper presents the latest dynamic nanoassemblies for effective PDT or PTT and combination phototherapies, including immunotherapy and image-guided therapy. Dynamic self-assembly exhibits great potential for clinical translation in diagnosis and treatment through its integrated versatility. Nanoassemblies based on multidisciplinary technology are a promising technique for treating incurable cancerous diseases in the future.

Ultrasound-Guided Radiofrequency Ablation of Chemodectomas in Five Dogs

Chemodectomas are low prevalence tumors with complex clinical management. Many present as an incidental finding however, in other dogs, they produce pericardial effusion and/or compression, leading to the appearance of severe clinical signs. There are currently several approaches: surgery, radiotherapy, stent placement and chemotherapy. This is the first description of percutaneous echo-guided radiofrequency ablation of aortic body tumors. This minimally invasive treatment is based on high frequency alternating electrical currents from an electrode that produces ionic agitation and generates frictional heat, causing coagulation necrosis. Five dogs with an echocardiographic and cytological diagnosis of chemodectoma underwent percutaneous echo-guided radiofrequency ablation. At the time of presentation, all the dogs showed clinical signs, such as ascites and/or collapse. There were no complications either during the procedure or in the following 24 hours. Rapid clinical improvement associated with a reduction in size and change in sonographic appearance of the mass were achieved with no complications. Six months follow-up was carried out in all dogs. A second percutaneous echo-guided RFA was performed eight months after the first procedure in one dog. Based on our experience, radiofrequency ablation seems to be a feasible and safe technique, making it a potential alternative therapeutic approach in the clinical management of aortic body tumors leading to severe clinical compromise.

Spectral detector CT applications in advanced liver imaging

OBJECTIVE

Spectral detector CT (SDCT) has many applications in advanced liver imaging. If appropriately utilized, this technology has the potential to improve image quality, provide new diagnostic information, and allow for decreased radiation dose. The purpose of this review is to familiarize radiologists with the uses of SDCT in liver imaging.

CONCLUSION

SDCT has a variety of post-processing techniques, which can be used in advanced liver imaging and can significantly add value in clinical practice.

Histological Correlation for Radiofrequency and Microwave Ablation in the Local Control of Hepatocellular Carcinoma (HCC) before Liver Transplantation: A Comprehensive Review

Simple Summary

Liver cancer is a growing problem around the world. Drugs for liver cancer have limited effect, there are not enough donors for liver transplants and many patients are not candidates for surgery to remove the tumor. In many of these cases, hyperthermia can destroy the tumor in situ with minimally invasive methods such as radiofrequency or microwave ablation. In this paper we review the literature evaluating success rates for complete ablation as judged by actual examination of treated tumors that were removed when patients received a liver transplant. While notable successes can be achieved with ablation, the published studies indicate both that complete treatment is not as common as thought and that imaging methods such as computed tomography and magnetic resonance scans do not completely identify residual cancer. There is therefore an important opportunity for improvement in the treatment of this disease.

Abstract

Radiofrequency ablation (RFA) and microwave ablation (MWA) are the most widely studied and applied ablation techniques for treating primary and secondary liver tumors. These techniques are considered curative for small hepatic tumors, with post-ablation outcomes most commonly assessed by an imaging follow up. However, there is increasing evidence of a discrepancy between radiological and pathological findings when ablated lesions are evaluated following liver resection or liver transplantation. A comprehensive review of the available literature reporting the complete pathological response (cPR) following RFA and MWA was performed to estimate the success rate and identify the factors associated with treatment failure. Following RFA, cPR is reported in 26–96% of tumors compared to 57–95% with MWA. Larger tumor size and vessels larger than 3 mm adjacent to the treated tumor are the most important factors identified by previous studies associated with viable residual tumors after RFA. Correlating post-ablation radiological studies with pathological findings shows that computed tomography (CT) and magnetic resonance imaging (MRI) have low sensitivity but high specificity for detecting residual viable or recurrent hepatocellular carcinoma (HCC) tumors. There are promising recent reports combining multiprobe ablation techniques with three-dimensional treatment planning software and stereotactic-aiming instrumentation to achieve more than 90% cPR in both small and large HCC tumors. In conclusion, the reported success for achieving cPR in HCC following RFA and MWA is highly variable in different studies and decreases with increasing lesion size and unfavorable tumor characteristics. Very few studies have reported a high rate of cPR. As these studies are single-center and retrospective, they need to be further validated and reproduced in other clinical settings.

What's New in Percutaneous Ablative Strategies for Hepatocellular Carcinoma and Colorectal Hepatic Metastases? 2020 Update

PURPOSE OF REVIEW

Ablation techniques are now well-established treatment options available for the management of primary and secondary hepatic malignancies. Currently available ablative techniques include radiofrequency ablation (RFA), microwave ablation (MWA), cryoablation, and irreversible electroporation (IRE). Along with advances in navigational devices and targeting technologies, ablation combined with other therapies may be the next therapeutic option in thermal ablation. The purpose of this review is to evaluate the current status of ablative technologies in interventional and medical oncology for management of liver malignancies.

RECENT FINDINGS

With the use of combination techniques (i.e., ablation and transarterial embolization procedures), thermal ablation is now moving toward treating tumors larger than 3 cm in size or tumors with macrovascular invasion. Ongoing trials are examining the optimum timing of combination therapies. Thermal ablation combined with hepatic resection may increase the number of patients with metastatic colorectal carcinoma to the liver who qualify for curative surgery. Combination therapies of thermal ablation and transarterial embolization allow for promising treatment responses for larger HCC. Surgery combined with thermal ablation can potentially increase the number of patients with metastatic colon cancer to the liver who qualify for curative surgery.

Ablation of Small Renal Masses

Renal cell carcinoma is most commonly diagnosed in the sixth or seventh decade of life. Historically, surgical extirpation was the gold standard treatment option for small renal masses. However, given the comorbidities in this elderly population, not all patients are candidates for surgery. The development of minimally invasive ablative therapies has solved the surgical dilemma in this patient population. Furthermore, the 2017 American Urological Association guidelines recommends consideration of percutaneous image guided thermal ablation as a treatment option for masses smaller than 3 cm even in healthy individuals. Percutaneous image guided thermal ablation is an attractive treatment option providing excellent local tumor control, fewer complications, better preservation of the renal functions, faster recovery and shorter hospital stay. Various ablative modalities are available in clinical practice. This includes radiofrequency ablation, cryoablation, microwave ablation, irreversible electroporation, high intensity focused ultrasound, and laser ablation. In this review, we focus on the most commonly used modalities including radiofrequency ablation and cryoablation and to a lesser extent microwave ablation and irreversible electroporation.

Multimodality Approach in Detection and Characterization of Hepatic Metastases

Early detection of liver metastases is important in patients with known primary malignancies. This plays an important role in treatment planning and impacts on further management of certain primary malignancies.

Magnetic resonance imaging (MRI), computed tomography (CT), and positron emission tomography-computed tomography scans are reported to have high accuracy in the diagnosis of intrahepatic lesions. MRI in particular has the advantages of its high tissue sensitivity and its multiparametric approach.

Hepatic metastatic lesions have considerable overlap in their radiological appearance, and in this article the imaging appearance of various hepatic metastasis and approach is described.

Radiofrequency ablation (RFA) of T1a renal cancer with externally cooled multitined expandable electrodes

INTRODUCTION

To retrospectively evaluate the mid-term outcomes of percutaneous radiofrequency ablation (RFA) with multitined expandable electrodes externally cooled with saline solution in patients with T1a renal cell carcinoma (RCC).

MATERIALS AND METHODS

In this retrospective study, we evaluated 39 RCC in 35 patients treated with CT-guided RFA in 41 procedures (2011-2017). All patients were staged T1a, N0, M0 prior to RFA. Mean tumor size was 24.48 mm. A 4-tined expandable RFA electrode cooled with pump-circulating saline was used. Efficacy was evaluated verifying complete tumor necrosis (no contrast enhancement on imaging) at the end of the procedure and on subsequent controls. Follow-up observation period was 5 years. Minor/major complications, hospitalization days, serum creatinine and GFR pre- and post-RFA (compared using paired t test) and post-operative pain (evaluated with NRS after treatment) were considered as safety indicators. Overall survival was also calculated (Kaplan-Meier method).

RESULTS

Of 35 patients, 30/35 had 1 treatment (primary effectiveness rate 86%), 4/35 had 2 treatments and 1/35 had 3 treatments for residual disease. There were no relapses and no mid-long-term complications; 3 minor (8%) and 1 major (2.7%) complications during perioperative period were reported. Mean before and after RFA serum creatinine rates were, respectively, 1.08 mg/dl and 1.11 mg/dl (p value: 0.4117). NRS median value is 0.8. Hospitalization days median value is [2.8 ± 1.9] days. 91.4% of all patients survived, with a median overall survival time of 65 months.

CONCLUSIONS

Mid-term results show that CT-guided RFA with multitined expandable electrodes externally cooled with saline solution is an effective and safe treatment in patients with RCC-staged T1aN0M0. Data reported in our study are in line with data reported in the literature from patients treated with other devices.

MRI Assessment of Hepatocellular Carcinoma after Local-Regional Therapy: A Comprehensive Review

Nearly 80% of cirrhotic patients diagnosed with hepatocellular carcinoma (HCC) are not eligible for surgical resection and instead undergo local-regional treatment. After therapy for HCC, patients undergo imaging surveillance to assess treatment efficacy and identify potential sites of progressive tumor elsewhere within the liver. Accurate interpretation of posttreatment imaging is essential for guiding further management decisions, and radiologists must understand expected treatment-specific imaging findings for each of the local-regional therapies. Of interest, expected imaging findings seen after radiation-based therapies (transarterial radioembolization and stereotactic body radiation therapy) are different than those seen after thermal ablation and transarterial chemoembolization. Given differences in expected posttreatment imaging findings, the current radiologic treatment response assessment algorithms used for HCC (modified Response Evaluation Criteria in Solid Tumors classification, European Association for the Study of Liver Diseases criteria, and Liver Imaging and Reporting Data System Treatment Response Algorithm) must be applied cautiously for radiation-based therapies in which persistent arterial phase hyperenhancement in the early posttreatment period is common and expected. This article will review the concept of tumor response assessment for HCC, the forms of local-regional therapy for HCC, and the expected posttreatment findings for each form of therapy. Keywords: Abdomen/GI, Liver, MR-Imaging, Treatment Effects, Tumor Response © RSNA, 2020.

A Clinical Prototype Transrectal Diffuse Optical Tomography (TRDOT) System for In vivo Monitoring of Photothermal Therapy (PTT) of Focal Prostate Cancer

We describe the rationale, design, fabrication and performance of a clinical transrectal diffuse optical tomography (TRDOT) system for in vivo monitoring of photothermal therapy (PTT) of localized prostate cancer. The system comprises a 32-channel fiberoptic-based, MRI-compatible transrectal probe connected to a computer-controlled instrument that includes laser diode sources, an optical fiber switch and photomultiplier tube detectors. Performance tests were performed in tissue-simulating phantoms and in ex vivo muscle tissue during PTT treatment. The safety and technical feasibility of in vivo transrectal use were tested in a canine prostate model and in a first-in-human study in a patient before PTT treatment. Limitations of the system are discussed, as well as further developments to translate it into planned clinical trials for monitoring the photocoagulation boundary in the prostate during PTT.

Performance of Shear Wave Elastography in Delineating the Radiofrequency Ablation Boundary: An in Vivo experiment

This study was aimed at exploring the cutoff value of Young's modulus of ablated tissue and the optimal scale at which shear wave elastography (SWE) can delineate the ablation boundary. The livers of 30 rabbits were radiofrequency (RF) ablated, and ultrasonic imaging, including SWE and contrast-enhanced ultrasound (CEUS), was performed. The ablation boundary in the SWE image was located using CEUS, and the SWE parameters of the boundary were measured to calculate the cutoff value of Young's modulus. The cutoff value of the ablated tissue was 48-50 kPa 2 h to 28 d post-ablation. The regions of increased stiffness in SWE images at a scale of 0-50 kPa overlapped well with the non-enhanced regions of CEUS images in 88% of specimens. Therefore, elasticity values differed significantly between ablated and non-ablated tissues, and the cutoff value for Young's modulus differentiated these tissues. SWE delineated the ablation boundary well at the optimal SWE scale with respect to the cutoff value.

Fluorescent Tissue Assessment of Colorectal Cancer Liver Metastases Ablation Zone: A Potential Real-Time Biomarker of Complete Tumor Ablation

BACKGROUND

This study aimed to evaluate whether rapid fluorescent tissue examination immediately after colorectal cancer liver metastasis (CLM) ablation correlates with standard pathologic and immunohistochemical (IHC) assessments.

METHODS

This prospective, National Institutes of Health-supported study enrolled 34 consecutive patients with 53 CLMs ablated between January 2011 and December 2014. Immediately after ablation, core needle sampling of the ablation zone was performed. Tissue samples were evaluated with fluorescent viability (MitoTracker Red) and nuclear (Hoechst) stains. Confocal microscope imaging was performed within 30 min after ablation. The same samples were subsequently fixed and stained with hematoxylin and eosin (H&E). Identified tumor cells underwent IHC staining for proliferation (Ki67) and viability (OxPhos). The study pathologist, blinded to the H&E and IHC assessment, evaluated the fluorescent images separately to detect viable tumor cells. Sensitivity, specificity, and overall concordance of the fluorescent versus H&E and IHC assessments were calculated.

RESULTS

A total of 63 tissue samples were collected and processed. The overall concordance rate between the immediate fluorescent and the subsequent H&E and IHC assessments was 94% (59/63). The fluorescent assessment sensitivity and specificity for the identification of tumor cells were respectively 100% (18/18) and 91% (41/45).

CONCLUSIONS

The study showed a high concordance rate between the immediate fluorescent assessment and the standard H&E and IHC assessment of the ablation zone. Given the documented prognostic value of ablation zone tissue characteristics for outcomes after ablation of CLM, the fluorescent assessment offers a potential intra-procedural biomarker of complete tumor ablation.

Multi-fiber distributed thermal profiling of minimally invasive thermal ablation with scattering-level multiplexing in MgO-doped fibers

We propose a setup for multiplexed distributed optical fiber sensors capable of resolving temperature distribution in thermo-therapies, with a spatial resolution of 2.5 mm over multiple fibers interrogated simultaneously. The setup is based on optical backscatter reflectometry (OBR) applied to optical fibers having backscattered power significantly larger than standard fibers (36.5 dB), obtained through MgO doping. The setup is based on a scattering-level multiplexing, which allows interrogating all the sensing fibers simultaneously, thanks to the fact that the backscattered power can be unambiguously associated to each fiber. The setup has been validated for the planar measurement of temperature profiles in ex vivo radiofrequency ablation, obtaining the measurement of temperature over a surface of 96 total points (4 fibers, 8 sensing points per cm2). The spatial resolution obtained for the planar measurement allows extending distributed sensing to surface, or even three-dimensional, geometries performing temperature sensing in the tissue with millimeter resolution in multiple dimensions.

Tumefactive Fat Necrosis with Multinucleate Giant Cell Reaction Mimicking Recurrent Renal Cell Carcinoma following Percutaneous Renal Cryoablation

Multinucleate Giant Cell (GC) reaction is a biological response that occurs secondary to infection, an implanted foreign body, tissue injury, or inflammation. In rare instances GC reactions have been reported following tissue ablation. Multinucleate GC reactions and tumefactive fat necrosis both have the ability to mimic cancer recurrence or metastasis and can appear as enhancing masses. We discuss a case of a surgically resected retroperitoneal perinephric mass thought to be recurrent renal cell carcinoma (RCC) that was pathologically confirmed as tumefactive fat necrosis with multinucleate GC reaction 2 years following percutaneous cryoablation of a small renal mass.

Whole tumor ablation of locally recurred hepatocellular carcinoma including retained iodized oil after transarterial chemoembolization improves progression-free survival

OBJECTIVES

To evaluate and compare clinical outcomes of two different radiofrequency ablation (RFA) methods for locally recurred hepatocellular carcinoma (LrHCC) after locoregional treatment.

METHODS

Our institutional review board approved this study with a waiver of informed consent. A total of 313 patients previously treated with transarterial chemoembolization (TACE) (n = 167) and RFA (n = 146) with a single LrHCC ≤ 3 cm was included from five tertiary referral hospitals. RFA was done for LrHCCs using either viable tumor alone ablation (VTA) method (VTA: n = 61 in the TACE group and n = 127 in the RFA group) or whole tumor ablation (WTA) method which includes both viable tumor and retained iodized oil or previously ablated zone (WTA: n = 106 in the TACE group and n = 19 in the RFA group). Local tumor progression (LTP)-free survival as well as progression-free survival (PFS) were estimated using the Kaplan-Meier method, and prognostic factors were evaluated using the Cox proportional hazards regression model.

RESULTS

In 167 patients with LrHCC who underwent TACE, the 5-year LTP-free survival after RFA was significantly higher with the VTA method than with the WTA method (26.9% vs. 87.8%; p < 0.001; hazard ratio (HR) = 8.53 [4.16-17.5]). The estimated 5-year PFS after RFA for LrHCC after TACE using the VTA method was 5.7%, which was significantly lower than that with the WTA method (26.4%) (p = 0.014; HR = 1.62 [1.10-2.38]). However, in 146 patients with LrHCC after initial RFA, there were no significant differences in cumulative incidence of LTP (p = 0.514) or PFS (p = 0.905) after RFA between the two ablation methods.

CONCLUSIONS

For RFA of LrHCC after TACE, the WTA method including both viable tumor and retained iodized oil could significantly lower LTP and improve PFS than VTA.

KEY POINTS

• Whole tumor ablation (WTA) could provide significantly better local tumor control for locally recurred HCC (LrHCC) after TACE than viable tumor alone ablation (VTA). • WTA for LrHCC after TACE could also provide significantly better progression-free survival than VTA. • Regarding LrHCC after RFA, VTA would provide a comparable clinical outcome to WTA.

The Role of a Curved Electrode with Controllable Direction in the Radiofrequency Ablation of Liver Tumors Behind Large Vessels

PURPOSE

To investigate the role of a novel curved radiofrequency ablation (RFA) electrode with controllable direction in the ablation of tumors behind large hepatic vessels in ex vivo bovine and in vivo canine liver experiments.

MATERIALS AND METHODS

Approval from the institutional animal care and use committee was obtained. In ex vivo experiments, conventional multi-tines expandable electrodes, conventional monopolar straight electrodes and novel curved electrodes were used in the ablation of the bovine liver (n = 90). The ablated area, parallel axis, vertical axis and shape of different electrodes were compared. Then, 24 beagle dogs (10 months old, female) were used for in vivo experiments. Visual tumor targets deeply located in the portal vein were established, and ultrasound-guided liver ablation was performed with different electrodes. The ablation range, target coverage rate, percentage of normal tissue injury and damage to adjacent vessels were evaluated. The Kruskal-Wallis test and the Chi-squared test were used for statistical analysis.

RESULTS

For the ex vivo study with a 3-cm electrode, the ablation area of the multi-tines expandable electrode group (7.14 ± 0.16 cm²) was significantly larger than that of the novel curved electrode group (5.01 ± 0.30 cm², P < 0.001) and the monopolar straight electrode group (5.43 ± 0.15 cm², P < 0.001). The results obtained with the 4-cm electrode in the three groups were in accordance with those of the 3-cm electrode. In vivo, the normal tissue damage area of the novel curved electrode group was smaller than that of the multi-tines expandable electrode group (1.10 ± 0.18 cm² vs. 4.00 ± 0.18 cm², P < 0.001). The target coverage rate of the novel curved electrode group was better than that of the monopolar straight electrode group (100% vs. 80.86 ± 1.68%, P < 0.001). The hematoxylin and eosin (H&E) and TUNEL staining results showed that the ablation necrosis area was adjacent to large vessels, but the vascular wall was not significantly damaged in the novel curved electrode group.

CONCLUSION

Our preliminary results showed that the novel curved RFA electrode with controllable direction could achieve accurate ablation for tumors behind large hepatic vessels, with a better target coverage rate and less damage to normal tissue, than conventional multi-tines expandable electrodes and monopolar straight electrodes.

Post Locoregional Therapy Treatment Imaging in Hepatocellular Carcinoma Patients: A Literature-based Review

Imaging plays a crucial role in the diagnosis of hepatocellular carcinoma (HCC) as well as in determining treatment efficacy, or complications, following therapy. Unlike other cancers, HCC is most commonly treated by locoregional therapies (LRTs) such as thermal ablation, transarterial chemoembolization, and transarterial radioembolization. These treatments can lead to changes on imaging that make determination of residual/recurrent disease difficult. This literature-based review discusses the expected postimaging findings following LRT.

Comparison of Chronologic Change in the Size and Contrast-Enhancement of Ablation Zones on CT Images after Irreversible Electroporation and Radiofrequency Ablation

Objective

To compare short-, mid-, and long-term follow-up ablation zone volume alterations as well as imaging features on contrast-enhanced computed tomography (CT) after irreversible electroporation (IRE) of primary and secondary liver tumors with findings subsequent to radiofrequency ablation (RFA).

Materials and Methods

Volume assessment of 39 ablation zones (19 RFA, 20 IRE) after intervention was performed at four time intervals (day 0 [t1; n = 39], day 1-7 [t2; n = 25], day 8-55 [t3; n = 28], after day 55 [t4; n = 23]) on dual-phase CT. Analysis of peripheral rim enhancement was conducted. Lesion's volume decrease relative to the volume at t1 was calculated and statistically analyzed with respect to patient's sex, age, ablation modality (IRE/RFA), and history of platinum-based chemotherapy (PCT).

Results

No influence of patient's sex or age on ablation volume was detected. The decrease in ablation zones' volume was significantly larger (p < 0.05 for all time intervals) after IRE (arterial phase, 7.5%; venous phase, 9.7% of initial volume) compared to RFA (arterial phase, 39.6%; venous phase, 45.3% of initial volume). After RFA, significantly smaller decreases in the ablation volumes, in general, were detected in patients treated with PCT in their history (p = 0.004), which was not detected after IRE (p = 0.288). In the arterial phase, peripheral rim enhancement was frequently detected after both IRE and RFA. In the venous phase, rim-enhancement was depicted significantly more often following IRE at t1 and t2 (pt1 = 0.003, pt2 < 0.001).

Conclusion

As per our analysis, ablation zone volume decreased significantly in a more rapid and more profound manner after IRE. Lesion's remodeling after RFA but not IRE seems to be influenced by PCT, possibly due to the type of cell death induced by the different ablation modalities.

Magnetic Resonance Mediated Radiofrequency Ablation

To introduce magnetic resonance mediated radiofrequency ablation (MR-RFA), in which the MRI scanner uniquely serves both diagnostic and therapeutic roles. In MR-RFA scanner-induced RF heating is channeled to the ablation site via a Larmor frequency RF pickup device and needle system, and controlled via the pulse sequence. MR-RFA was evaluated with simulation of electric and magnetic fields to predict the increase in local specific-absorption-rate (SAR). Temperature-time profiles were measured for different configurations of the device in agar phantoms and ex vivo bovine liver in a 1.5 T scanner. Temperature rise in MR-RFA was imaged using the proton resonance frequency method validated with fiber-optic thermometry. MR-RFA was performed on the livers of two healthy live pigs. Simulations indicated a near tenfold increase in SAR at the RFA needle tip. Temperature-time profiles depended significantly on the physical parameters of the device although both configurations tested yielded temperature increases sufficient for ablation. Resected livers from live ablations exhibited clear thermal lesions. MR-RFA holds potential for integrating RF ablation tumor therapy with MRI scanning. MR-RFA may add value to MRI with the addition of a potentially disposable ablation device, while retaining MRI's ability to provide real time procedure guidance and measurement of tissue temperature, perfusion, and coagulation.

Technology of irreversible electroporation and review of its clinical data on liver cancers

INTRODUCTION

Irreversible electroporation (IRE) has developed as a novel percutaneous ablative technique over the past decade and its utility in the treatment of primary and metastatic liver disease has progressed rapidly.

AREAS COVERED

After discussing the principles behind the technology and the practical steps in its use, this article offers a detailed analysis of the recent published work that evaluates its safety and efficacy. The strengths and weaknesses of other ablative techniques, including radiofrequency ablation, microwave ablation and cryoablation, are discussed in detail. Other aspects of IRE, including post-treatment clinical follow-up, expected imaging findings, and the most frequently encountered complications, are covered. Finally, the future of IRE is examined as it pertains to advancements in the treatment of hepatic malignancy.

EXPERT COMMENTARY

The characteristics of IRE that make this technology uniquely suited for the treatment of liver tumors have allowed it to gain a significant foothold in interventional oncology. Continued development of IRE will lead to further advances in the management of previously untreatable liver cancers.

[Percutaneous renal ablation: Pre-, per-, post-interventional evaluation modalities and adapted management]

OBJECTIVES

Ablative treatment (AT) rise is foreseen, validation of steps to insure good proceedings is needed. By looking over the process of the patient, this study evaluates the requirements and choices needed in every step of the management.

METHODS

We searched MEDLINE^®, Embase^®, using (MeSH) words and we looked for all the studies. Investigators graded the strength of evidence in terms of methodology, language and relevance.

RESULTS

Explanations of AT proposal rather than partial nephrectomy or surveillance have to be discussed in a consultation shared by urologist and interventional radiologist. Per-procedure choices depend on predictable ballistic difficulties. High volume, proximity of the hilum or of a risky organ are in favor of general anesthesia, cryotherapy and computed tomography/magnetic resonance imaging (CT/MRI). Percutaneous approach should be privileged, as it seems as effective as the laparoscopic approach. Early and delayed complications have to be treated both by urologist and radiologist. Surveillance by CT/MRI insure of the lack of contrast-enhanced in the treated area. Patients and tumors criteria, in case of incomplete treatment or recurrence, are the key of the appropriate treatment: surgery, second session of AT, surveillance.

CONCLUSION

AT treatments require patient's comprehension, excellent coordination of the partnership between urologist and radiologist and relevant choices during intervention.

Imaging of Hepatic Metastases

BACKGROUND

Imaging plays an important role not only in screening, evaluating, staging, and monitoring disease, but also in surveillance following tumor ablation. Advances in imaging techniques have increased our ability to detect and characterize focal liver lesions, resulting in improvements in diagnostic capability and improved monitoring of liver metastases. This has led to increased interest in both hepatic imaging and image-guided hepatic interventions.

METHODS

Several imaging options are reviewed according to their effective application, notably computed tomography (CT), CT during arterial portography, ultrasound, magnetic resonance imaging, positron emission tomography, and integrated PET/CT imaging.

RESULTS

Although there are exceptions regarding imaging options based on patient selection and on institution preference and expertise, multidetector helical CT scanning remains the dominant modality in the evaluation of suspected hepatic metastases, and for preoperative planning, treatment monitoring, and posttreatment follow-up.

CONCLUSIONS

Ultimately, the choice of imaging modality must be based not only on the patient and the clinical situation, but also on the imaging expertise within each institution.

Minimally invasive local ablative therapies in combination with radioiodine therapy in benign thyroid disease: preparation, feasibility and efficiency - preliminary results

PURPOSE

Initial studies of combinations of radioiodine therapy (RIT) and local ablative procedures for the treatment of thyroid nodules have shown promising results. The goal of this study was to evaluate the effectiveness of RIT combined with radiofrequency ablation (RFA) in patients with goitres and to determine which ablative procedure is the most suitable for a combined therapy.

METHODS

Thirty patients with goitres were divided into two subgroups. A test group of 15 patients received combined therapy (RIT + RFA) and a control group of 15 patients received RIT mono therapy. All patients underwent assessments including ultrasound, laboratory evaluation (T3, T4, TSH, TG, TPOAb, TgAbTRAb) and scintigraphic imaging with Tc-99m-Pertechnetate. The 3-month volume reduction was used to evaluate therapy effectiveness.

RESULTS

Combined therapy (subgroup 1) resulted in a significant (p < 0.05) thyroid volume reduction (22.3 ± 54 ml/32.2 ± 58.2%) with better performance (p > 0.05) than the control group (20.2 ± 32.2 ml/29.6 ± 42.1%). All patients became euthyroid after treatment. No major discomfort or complications occurred. A review of the literature investigating combinations of other local ablative procedures with RIT was performed to determine the most promising combination.

CONCLUSIONS

The present study confirms the positive experiences with the combined therapy of RIT and local ablative procedures shown in the current literature and approves this approach for the treatment of goitres with RFA + RIT. These findings, when confirmed by further studies, should expand the indication of combined therapy as a minimally invasive alternative to surgery.

Comparative study of conventional US, contrast enhanced US and enhanced MR for the follow-up of prostatic radiofrequency ablation

The aim of the present study was to evaluate and compare the effectiveness of different imaging methods during follow-up of prostatic radiofrequency ablation. Prostatic radiofrequency ablation (RFA) was performed in 20 healthy beagle dogs. Various imaging examinations were used to monitor the results of RFA, including conventional ultrasound (US), contrast enhanced ultrasound (CEUS) and enhanced magnetic resonance (MR). Imaging exams were performed at five phases: Immediately following RFA, one week later, one month later, three months later and six months later. The morphology for each imaging test and histological results were recorded and compared in each phase. Based on the actual results from autopsy, the accuracy of those imaging exams was evaluated. The canine prostate gland demonstrated typical coagulative necrosis immediately following RFA. The lesion would develop into stable cyst if no other complications occurred within the six-month follow-up. Regarding the RFA lesion volume measurement and the reflection of pathological changes, conventional US was not able to accurately measure the volume of RFA lesion and missed many more details concerning the RFA-treated area than CEUS and MR during the three months. The results from CEUS exhibited comparable accuracy to those from enhanced MR at each phase. However, there were no significant differences in the results from US, CEUS and MR at six months, which may contribute to the complete formation of lesion cyst. In the early phase, conventional US was not sufficient for evaluating the efficacy of RFA. Enhanced US and MR provided clear images and accurate information. However, CEUS has the advantage of being more economical, using more convenient equipment and faster scanning, thus identifying it as the more feasible choice. Furthermore, no notable advantages were observed among any image examinations in the long-term follow-up.

Comparison of elastography, contrast-enhanced ultrasonography, and computed tomography for assessment of lesion margin after radiofrequency ablation in livers of healthy dogs

OBJECTIVE To assess by use of various diagnostic imaging modalities acute changes in livers of healthy dogs after radiofrequency ablation (RFA) and determine the capability of each imaging modality to monitor ablation lesion changes.

ANIMALS 6 healthy Beagles.

PROCEDURES 12 ablation lesions were created in the liver of the dogs (2 lesions/dog). Ablation lesions were evaluated by use of conventional ultrasonography, strain elastography, and contrast-enhanced ultrasonography immediately after (time 0), 30 to 60 minutes after, and 3 days after RFA, and by use of CT 30 minutes and 3 days after RFA. Three dogs were euthanized shortly after RFA, and the other 3 dogs were euthanized on day 3. Lesion size measured by each imaging modality was compared with necropsy findings.

RESULTS Immediately after RFA, clear margins were more visible with elastography and contrast-enhanced ultrasonography than with conventional ultrasonography, which had acoustic shadowing. On triphasic contrast CT, the ablation zone, which indicated necrosis and hemorrhage, was not enhanced and could be measured. Marked enhancement of the periablation rim was observed during the venous phase and was identified as granulation tissue. Size of the ablation area measured on enhanced CT images was strongly correlated with actual lesion size.

CONCLUSIONS AND CLINICAL RELEVANCE For dogs of this study, CT was the most reliable method for lesion size determination. Although ultrasonographic imaging measurements underestimated lesion size, all modalities could be used to provide additional real-time guidance for RFA procedures of the liver as well as for other RFA procedures.

Determination of the electrical conductivity of human liver metastases: impact on therapy planning in the radiofrequency ablation of liver tumors

Background Radiofrequency ablation is used to induce thermal necrosis in the treatment of liver metastases. The specific electrical conductivity of a liver metastasis has a distinct influence on the heat formation and resulting tumor ablation within the tissue. Purpose To examine the electrical conductivity σ of human colorectal liver metastases and of tumor-free liver tissue in surgical specimens. Material and Methods Surgical specimens from patients with resectable colorectal liver metastases were used for measurements (size of metastases <30 mm). A four-needle measuring probe was used to determine the electrical conductivity σ of human colorectal liver metastasis (n = 8) and tumor-free liver tissue (n = 5) in a total of five patients. All measurements were performed at 470 kHz, which is the relevant frequency for radiofrequency ablation. The tissue temperature was also measured. Hepatic resections were performed in accordance with common surgical standards. Measurements were performed in the operating theater immediately after resection. Results The median electrical conductivity σ was 0.57 S/m in human colorectal liver metastases at a median temperature of 35.1℃ and 0.35 S/m in tumor-free liver tissue at a median temperature of 34.9℃. The electrical conductivity was significantly higher in tumor tissue than in tumor-free liver tissue ( P = 0.005). There were no differences in tissue temperature between the two groups ( P = 0.883). Conclusion The electrical conductivity is significantly higher in human colorectal liver metastases than in tumor-free liver tissue at a frequency of 470 kHz.

Microwave ablation of malignant extremity bone tumors

Background

The current application of limb salvage process has some unsolved problems, such as prosthesis loosening, which severely limits the function of the preserved limbs. Innovative approaches are needed to further improve functional outcome.

Patients and methods

Instead of en-bloc resection of tumor-bearing bone, it is dissected from the surrounding normal tissues, followed by devitalizing the bone segment and the extra-cortical bulk by microwave induced hyperthermia in situ through the antenna array. From May 1999 to March 2012, 544 patients with malignant bone tumors of the extremities were treated by the novel method.

Results

The over 3-year survival rate was 59.1 % for high-grade malignancy, 88.7 % for low-grade malignancy. In the majority of the patients, cosmetic and useful limbs were preserved. Local recurrence rate was 9.8 % for the high grade malignancy (mainly occurred at the early stage of the research). The overall fracture rate was 2.6 %. Deep infection rate was 1.8 %. The complication rate is lower than the literature reports. After heat necrosis, the dead bone maintains both the osteoconduction and osteoinduction properties.

Conclusions

The application of microwave induced hyperthermia for treatment of malignant bone tumors, except the late diagnosed cases who’s tumor-bearing bone was destroyed too severe to do biological reconstruction, is an effective, simple, and inexpensive method. The oncological and functional results are encouraging.

Optimizing Irreversible Electroporation Ablation with a Bipolar Electrode

PURPOSE

To optimize single-insertion bipolar irreversible electroporation (IRE) by characterizing effects of electric parameters and controlling tissue electric properties in a porcine model.

MATERIALS AND METHODS

Single-insertion electrode bipolar IRE was performed in 28 in vivo pig livers (78 ablations). First, effects of voltage (2,700-3,000 V), number of pulses, repeated cycles (1-6 cycles), and pulse width (70-100 µs) were studied. Next, electric conductivity was altered by instillation of hypertonic and hypotonic fluids. Finally, effects of thermal stabilization were assessed using internal electrode cooling. Treatment effect was evaluated 2-3 hours after IRE. Dimensions were compared and subjected to statistical analysis.

RESULTS

Delivering 3,000 V at 70 µs for a single 90-pulse cycle yielded 3.8 cm ± 0.4 × 2.0 cm ± 0.3 of ablation. Applying 6 cycles of energy increased ablation to 4.5 cm ± 0.4 × 2.6 cm ± 0.3 (P < .001). Further increasing pulse lengths to 100 µs (6 cycles) increased ablation to 5.0 cm ± 0.4 × 2.9 cm ± 0.3 (P < .001) but resulted in electric spikes and system crashes in 40%-50% of cases. Increasing tissue electric conductivity via hypertonic solution instillation in surrounding tissues increased frequency of generator crashes, whereas continuous instillation of distilled water eliminated this arcing phenomenon but reduced ablation to 2.3 cm ± 0.1. Controlled instillation of distilled water when electric arcing was suspected from audible popping produced ablations of 5.3 cm ± 0.6 × 3.1 cm ±0.3 without crashes. Finally, 3.1 cm ± 0.1 short-axis ablation was achieved without system crashes with internal electrode perfusion at 37°C versus 2.3 cm ± 0.1 with 4°C-10°C perfusion (P < .001).

CONCLUSIONS

Bipolar IRE ablation zones can be increased with repetitive high voltage and greater pulse widths accompanied by either judicious instillation of hypotonic fluids or internal electrode perfusion to minimize unwanted electric arcing.