A review of the general aspects of radiofrequency ablation

New Ultherapy method: Utilizing novel surgical and anatomical concepts yields outstanding results

BACKGROUND

Micro-focused ultrasound (MFU) is a technique for skin rejuvenation and lifting, targeting the facial SMAS-a fibrous network encompassing the platysma muscle and parotid fascia.

OBJECTIVE

This study aims to propose a novel and cost-effective method (suggested by Fatemi) for Ultherapy, comparing its effectiveness with the conventional approach.

MATERIALS AND METHODS

A prospective double-blind clinical trial was conducted with 30 female volunteers randomly assigned to two groups: The control group (conventional method) and the experimental group (new method). Ultherapy procedures utilized MFU technology with low energy and a higher frequency.

RESULTS

Statistically significant differences in lifting effects and improvement in skin laxity were observed between the two groups. The new method, with a focus on the parotideal area of the SMAS, demonstrated superior outcomes and higher patient satisfaction.

CONCLUSION

The parotideal region's accessibility, increased thickness, and safety profile make it an ideal target for Ultherapy. This not only reduces the risk of nerve injury but also yields effective collagen remodeling and skin-lifting results.

A Review of Recent Advancements in Sensor-Integrated Medical Tools

A medical tool is a general instrument intended for use in the prevention, diagnosis, and treatment of diseases in humans or other animals. Nowadays, sensors are widely employed in medical tools to analyze or quantify disease-related parameters for the diagnosis and monitoring of patients' diseases. Recent explosive advancements in sensor technologies have extended the integration and application of sensors in medical tools by providing more versatile in vivo sensing capabilities. These unique sensing capabilities, especially for medical tools for surgery or medical treatment, are getting more attention owing to the rapid growth of minimally invasive surgery. In this review, recent advancements in sensor-integrated medical tools are presented, and their necessity, use, and examples are comprehensively introduced. Specifically, medical tools often utilized for medical surgery or treatment, for example, medical needles, catheters, robotic surgery, sutures, endoscopes, and tubes, are covered, and in-depth discussions about the working mechanism used for each sensor-integrated medical tool are provided.

A Safety and Feasibility Trial of Ultrasound-Guided Radiofrequency Ablation of Parotid Warthin's Tumor

OBJECTIVE

To determine if ultrasound-guided (USG) radiofrequency ablation (RFA) of Parotid Warthin's tumor under local anesthesia is a safe and effective procedure.

STUDY DESIGN

Safety and feasibility study.

SETTING

Tertiary academic medical center.

METHODS

This is an IDEAL phase 2a trial in a tertiary referral center. Twenty patients with Parotid Warthin's tumor were recruited. RFA was done between September and December 2021 for all 20 patients using a CoATherm AK-F200 machine with a disposable, 18G × 7 mm radiofrequency electrode. Results and follow-up statistics were compared with a historic sample of patients with parotid Warthin's tumor who underwent parotidectomy between 2019 and 2021 in the same center.

RESULTS

Nineteen patients were included in the analysis as 1 patient dropped out after 4 weeks of follow-up. The mean age for the RFA group was 67 years old with most of them being male smokers. At a median of 45 weeks (44-47 weeks) postprocedure there was a 7.48 mL (68.4%) volume reduction compared to baseline. Three patients had transient facial nerve (FN) paresis, 1 recovered within hours, and the other 2 by 12 weeks follow-up. Three patients had great auricular nerve numbness; 1 patient had infected hematoma treated in an out-patient manner. Compared to a historic cohort of parotidectomy patients for Warthin's tumor, there was no significant difference in FN paresis and other minor complications between the 2 treatment modalities.

CONCLUSION

The current analysis suggests that USG RFA of Warthin's Tumor is a safe alternative to parotidectomy with shorter operative time and length of stay.

Thermoablative Techniques to Treat Excessive Central Airway Collapse

Excessive central airway collapse (ECAC) is a condition characterized by the excessive narrowing of the trachea and mainstem bronchi during expiration, which can be caused by Tracheobronchomalacia (TBM) or Excessive Dynamic Airway Collapse (EDAC). The initial standard of care for central airway collapse is to address any underlying conditions such as asthma, COPD, and gastro-esophageal reflux. In severe cases, when medical treatment fails, a stent-trial is offered to determine if surgical correction is a viable option, and tracheobronchoplasty is suggested as a definitive treatment approach. Thermoablative bronchoscopic treatments, such as Argon plasma coagulation (APC) and laser techniques (potassium-titanyl-phosphate [KTP], holmium and yttrium aluminum pevroskyte [YAP]) are a promising alternative to traditional surgery. However, further research is needed to assess their safety and effectiveness in humans before being widely used.

Contemporary advances in the endoscopic management of cholangiocarcinoma: a review of accomplished milestones and prospective opportunities

INTRODUCTION

Cholangiocarcinoma, a primary malignancy of epithelial cells of the bile ducts, has been shown to have increasing incidence rates globally. Many of the current advances aim to improve the accuracy of differentiation between benign biliary strictures and cholangiocarcinoma, which include endoscopic techniques, devices, image processing, and the use of genomic sequencing in acquired specimens.

AREAS COVERED

In this review, the authors explore the historical timeline of changes leading to modern management of cholangiocarcinoma, with special emphasis on endoscopic modalities and novel therapeutic interventions. The authors also expand on the strengths and shortcomings of endoscopic diagnostics and techniques in biliary drainage and finally discuss potential areas to focus for future research and development.

EXPERT OPINION

Despite the advances in diagnosis and management of cholangiocarcinoma, there remain multiple tasks that are still awaiting to be completed. Next-generation sequencing in the diagnosis of cholangiocarcinoma needs to be further tested, validated, and easily obtainable. Other innovative diagnostic modalities, such as the use of artificial intelligence in cholangioscopy, may provide an effective complementary modality to existing techniques. A consensus on biliary drainage needs to be defined and account for longevity and patient convenience.

Radio frequency ablation for the intrauterine treatment of giant placental chorioangioma associated with fetal compromise: A case report

Giant placental chorioangiomas associated with fetal hyperdynamic circulation complications are rare to see. Here, we summarized a case of giant placental chorioangioma associated with fetal anemia and heart failure treated by radiofrequency ablation (RFA) combined with cordocentesis and intrauterine transfusion. The sonographic appearance of the placental chorioangioma was atypical which was isoechoic with unclear boundary. RFA was performed successfully at 27 weeks of gestation, when the chorioangioma has increased to 17.0 × 10.6 × 12.3 cm³ . Unfortunately, intrauterine fetal demise was found on the first day after operation. After induction of labor, it was pathologically confirmed as placental chorioangioma.

Direct and indirect damage zone of radiofrequency ablation in porcine lumbar vertebra

Objectives

To explore the direct and indirect heat damage zone of radiofrequency ablation (RFA) in porcine vertebrae and to verify the safety of RFA in a vascularized vertebral tumor model.

Methods

RFA was performed in the porcine lumbar vertebrae. Magnetic resonance (MR) imaging, hematoxylin and eosin (HE), and terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) were used to assess the extent of direct and indirect injuries after RFA. The cavity of lumbar vertebrae was made, and the adjacent muscle flap was used to fill the cavity to make a vertebrae tumor model. RFA was performed in the vascularized vertebral tumor model.

Results

T1-weighted images showed a hypointensive region in the center surrounded by a more hypointensive rim on day 0 and 14. T2-weighted images showed that RFA zone was hypointensive on day 0. On day 7, hypointensity was detected in the center surrounded by a hyperintensive rim. HE showed that the RFA zone could be clearly observed on day 14. Thin bone marrow loss areas were seen around the RFA zone, which was consistent with the hyperintensive rim on the T2-weighted images. TUNEL showed a large number of apoptotic cells in the RFA zone. During RFA in the vertebral tumor model, the temperature of all monitoring positions was less than 45 °C.

Conclusion

Using in vivo experiments, the effective zone of RFA was evaluated by MR imaging and pathology, and the direct and indirect damage range were obtained. The safety of RFA was verified by RFA in a vascularized vertebral tumor model.

Development of a Three-Dimensional Multi-Modal Perfusion-Thermal Electrode System for Complete Tumor Eradication

Background: Residual viable tumor cells after ablation at the tumor periphery serve as the source for tumor recurrence, leading to treatment failure. Purpose: To develop a novel three-dimensional (3D) multi-modal perfusion-thermal electrode system completely eradicating medium-to-large malignancies. Materials and Methods: This study included five steps: (i) design of the new system; (ii) production of the new system; (iii) ex vivo evaluation of its perfusion-thermal functions; (iv) mathematic modeling and computer simulation to confirm the optimal temperature profiles during the thermal ablation process, and; (v) in vivo technical validation using five living rabbits with orthotopic liver tumors. Results: In ex vivo experiments, gross pathology and optical imaging demonstrated the successful spherical distribution/deposition of motexafin gadolinium administered through the new electrode, with a temperature gradient from the electrode core at 80 °C to its periphery at 42 °C. An excellent repeatable correlation of temperature profiles at varying spots, from the center to periphery of the liver tumor, was found between the mathematic simulation and actual animal tumor models (Pearson coefficient ≥0.977). For in vivo validation, indocyanine green (ICG) was directly delivered into the peritumoral zones during simultaneous generation of central tumoral lethal radiofrequency (RF) heat (>60 °C) and peritumoral sublethal RF hyperthermia (<60 °C). Both optical imaging and fluorescent microscopy confirmed successful peritumoral ICG distribution/deposition with increased heat shock protein 70 expression. Conclusion: This new 3D, perfusion-thermal electrode system provided the evidence on the potential to enable simultaneous delivery of therapeutic agents and RF hyperthermia into the difficult-to-treat peritumoral zones, creating a new strategy to address the critical limitation, i.e., the high incidence of residual and recurrent tumor following thermal ablation of unresectable medium-to-large and irregular tumors.

Synthesised Conductive/Magnetic Composite Particles for Magnetic Ablations of Tumours

Ablation is a clinical cancer treatment, but some demands are still unsatisfied, such as electromagnetic interferences amongst multiple ablation needles during large tumour treatments. This work proposes a physical synthesis for composite particles of biocompatible iron oxide particles and liquid metal gallium (Ga) with different alternative-current (AC)-magnetic-field-induced heat mechanisms of magnetic particle hyperthermia and superior resistance heat. By some imaging, X-ray diffraction, and vibrating sample magnetometer, utilised composite particles were clearly identified as the cluster of few iron oxides using the small weight ratio of high-viscosity liquid metal Ga as conjugation materials without surfactants for physical targeting of limited fluidity. Hence, well penetration inside the tissue and the promotion rate of heat generation to fit the ablation requirement of at least 60 °C in a few seconds are achieved. For the injection and the post-injection magnetic ablations, the volume variation ratios of mice dorsal tumours on Day 12 were expressed at around one without tumour growth. Its future powerful potentiality is expected through a percutaneous injection.

Integrated, Transparent Silicon Carbide Electronics and Sensors for Radio Frequency Biomedical Therapy

The integration of micro- and nanoelectronics into or onto biomedical devices can facilitate advanced diagnostics and treatments of digestive disorders, cardiovascular diseases, and cancers. Recent developments in gastrointestinal endoscopy and balloon catheter technologies introduce promising paths for minimally invasive surgeries to treat these diseases. However, current therapeutic endoscopy systems fail to meet requirements in multifunctionality, biocompatibility, and safety, particularly when integrated with bioelectronic devices. Here, we report materials, device designs, and assembly schemes for transparent and stable cubic silicon carbide (3C-SiC)-based bioelectronic systems that facilitate tissue ablation, with the capability for integration onto the tips of endoscopes. The excellent optical transparency of SiC-on-glass (SoG) allows for direct observation of areas of interest, with superior electronic functionalities that enable multiple biological sensing and stimulation capabilities to assist in electrical-based ablation procedures. Experimental studies on phantom, vegetable, and animal tissues demonstrated relatively short treatment times and low electric field required for effective lesion removal using our SoG bioelectronic system. In vivo experiments on an animal model were conducted to explore the versatility of SoG electrodes for peripheral nerve stimulation, showing an exciting possibility for the therapy of neural disorders through electrical excitation. The multifunctional features of SoG integrated devices indicate their high potential for minimally invasive, cost-effective, and outcome-enhanced surgical tools, across a wide range of biomedical applications.

Effect of Hashimoto's thyroiditis on the extent of the ablation zone in early stages of ultrasound-guided radiofrequency ablation for papillary thyroid microcarcinoma: a large cohort study of 772 patients

PURPOSE

To evaluate the effect of Hashimoto's thyroiditis (HT) on the extent of ablation zone in ultrasound (US)-guided radiofrequency ablation (RFA) for early stages of papillary thyroid microcarcinoma (PTMC).

METHOD

We selected 772 patients with 797 PTMCs who underwent with RFA from August 2017 to August 2020. They were subdivided into two groups as follows: (i) 216 patients (224 PTMCs) with HT in the 'HT + PTMC' group and (ii) 556 patients (573 PTMCs) with healthy thyroid in the 'PTMC' group. We assessed the extent (maximum diameter and volume) of the ablation zone by contrast-enhanced ultrasound (CEUS) immediately, one day, and 1 week following RFA.

RESULTS

The ablation zone of the 'HT + PTMC' group was smaller than that of the 'PTMC' group at 1 week of RFA (maximum diameter: 14.6 ± 3.1 mm vs. 15.2 ± 3.2 mm and volume: 0.932 ± 0.498 mL vs. 1.028 ± 0.540 mL, respectively, p < .05). However, there were no differences before, immediately, and one day post-RFA (p > .05). Life-threatening complications did not develop in any of the patients.

CONCLUSION

RFA-treated PTMCs were smaller in size in patients with HT than in those with a healthy thyroid at 1 week of RFA. However, the exact mechanism underlying this phenomenon and its clinical significance warrant further investigation.

Ablative therapies of the biliary tree

Cholangiocarcinoma, a malignancy of the epithelial cells in the intrahepatic or extrahepatic biliary tree, is often diagnosed at later stages. Median survival duration ranges from 3 to 9 months with a less than ten percent 5-year survival rate. Thus, often treatment strategies are aimed more towards palliation instead of cure. With the majority of patients presenting with unresectable disease at the time of diagnosis, surgical intervention is not feasible, making less invasive endoscopic therapies more suitable. Initially, biliary stents were utilized for biliary decompression to mitigate cholestatic symptoms and prevent cholangitis; however, this strategy did not prove to provide significant survival benefit. Therefore, efforts to treat the tumor burden itself in addition to maintaining biliary patency became a focus of innovation and research in the endoscopic field. This study has led to the advent of therapies such as photodynamic therapy, radiofrequency ablation, and intraluminal brachytherapy. These options combined with biliary stenting have shown to not only offer the benefit of biliary decompression, but also to potentially improve stent patency and survival. Further, there is an anti-tumor effect of each of these modalities, portending an additional benefit in this subset of patients. Despite numerous retrospective and prospective studies assessing these ablative therapies, there is still a paucity of appropriately powered randomized controlled trials, and further research has yet to be done in the field. This review details the current literature entailing endobiliary ablative strategies.

Evidence based tools to improve efficiency of currently administered oncotherapies for tumors of the hepatopancreatobiliary system

Hepatopancreatobiliary tumors are challenging to treat, and the advanced or metastatic forms have a very low 5-year survival rate. Several drug combinations have been tested, and new therapeutic approaches have been introduced in the last decades, including radiofrequency and heat based methods. Hyperthermia is the artificial heating of tumors by various biophysical methods that may possess immunostimulant, tumoricidal, and chemoradiotherapy sensitizer effects. Both whole-body and regional hyperthermia studies have been conducted since the 1980s after the introduction of deep-seated tumor hyperthermia techniques. Results of the effects of hyperthermia in hepatocellular and pancreatic cancer are known from several studies. Hyperthermia in biliary cancers is a less investigated area. High local and overall responses to treatment, increased progression-free and overall survival, and improved laboratory and quality-of-life results are associated with hyperthermia in all three tumor types. With the evolution of chemotherapeutic agents and the introduction of newer techniques, the combination of adjuvant hyperthermia with those therapies is advantageous and has not been associated with an increase in alarming adverse effects. However, despite the many positive effects of hyperthermia, its use is still only known at the experimental level, and its concomitant utilization in routine cancer treatment is not certain because of the lack of thorough clinical studies.

Impact of radiofrequency ablation (RFA) on bone quality in a murine model of bone metastases

Thermal therapies such as radiofrequency ablation (RFA) are gaining widespread clinical adoption in the local treatment of skeletal metastases. RFA has been shown to successfully destroy tumor cells, yet the impact of RFA on the quality of the surrounding bone has not been well characterized. RFA treatment was performed on femora of rats with bone metastases (osteolytic and osteoblastic) and healthy age matched rats. Histopathology, second harmonic generation imaging and backscatter electron imaging were used to characterize changes in the structure, organic and mineral components of the bone after RFA. RFA treatment was shown to be effective in targeting tumor cells and promoting subsequent new bone formation without impacting the surrounding bone negatively. Mineralization profiles of metastatic models were significantly improved post-RFA treatment with respect to mineral content and homogeneity, suggesting a positive impact of RFA treatment on the quality of cancer involved bone. Evaluating the impact of RFA on bone quality is important in directing the growth of this minimally invasive therapeutic approach with respect to fracture risk assessment, patient selection, and multimodal treatment planning.

Temperature Monitoring in Hyperthermia Treatments of Bone Tumors: State-of-the-Art and Future Challenges

Bone metastases and osteoid osteoma (OO) have a high incidence in patients facing primary lesions in many organs. Radiotherapy has long been the standard choice for these patients, performed as stand-alone or in conjunction with surgery. However, the needs of these patients have never been fully met, especially in the ones with low life expectancy, where treatments devoted to pain reduction are pivotal. New techniques as hyperthermia treatments (HTs) are emerging to reduce the associated pain of bone metastases and OO. Temperature monitoring during HTs may significantly improve the clinical outcomes since the amount of thermal injury depends on the tissue temperature and the exposure time. This is particularly relevant in bone tumors due to the adjacent vulnerable structures (e.g., spinal cord and nerve roots). In this Review, we focus on the potential of temperature monitoring on HT of bone cancer. Preclinical and clinical studies have been proposed and are underway to investigate the use of different thermometric techniques in this scenario. We review these studies, the principle of work of the thermometric techniques used in HTs, their strengths, weaknesses, and pitfalls, as well as the strategies and the potential of improving the HTs outcomes.

Advances in Cancer Therapeutics: Conventional Thermal Therapy to Nanotechnology-Based Photothermal Therapy

In this review, advancement in cancer therapy that shows a transition from conventional thermal therapies to laser-based photothermal therapies is discussed. Laser-based photothermal therapies are gaining popularity in cancer therapeutics due to their overall outcomes. In photothermal therapy, light is converted into heat to destruct the various types of cancerous growth. The role of nanoparticles as a photothermal agent is emphasized in this review article. Magnetic, as well as non-magnetic, nanoparticles have been effectively used in the photothermal-based cancer therapies. The discussion includes a critical appraisal of in vitro and in vivo, as well as the latest clinical studies completed in this area. Plausible evidence suggests that photothermal therapy is a promising avenue in the treatment of cancer.

Study of flow effects on temperature-controlled radiofrequency ablation using phantom experiments and forward simulations

PURPOSE

Blood flow is known to add variability to hepatic radiofrequency ablation (RFA) treatment outcomes. However, few studies exist on its impact on temperature-controlled RFA. Hence, we investigate large-scale blood flow effects on temperature-controlled RFA in flow channel experiments and numerical simulations.

METHODS

Ablation zones were induced in tissue-mimicking, thermochromic phantoms with a single flow channel, using an RF generator with temperature-controlled power delivery and a monopolar needle electrode. Channels were generated by molding the phantom around a removable rod. Channel radius and saline flow rate were varied to study the impact of flow on (i) the ablated cross-sectional area, (ii) the delivered generator power, and (iii) the occurrence of directional effects on the thermal lesion. Finite volume simulations reproducing the experimental geometry, flow conditions, and generator power input were conducted and compared to the experimental ablation outcomes.

RESULTS

Vessels of different channel radii r affected the ablation outcome in different ways. For r = 0.275  mm, the ablated area decreased with increasing flow rate while the energy input was hardly affected. For r = 0.9  mm and r = 2.3  mm, the energy input increased toward larger flow rates; for these radii, the ablated area decreased and increased toward larger flow rates, respectively, while still being reduced overall as compared to the reference experiment without flow. Directional effects, that is, local shrinking of the lesion upstream of the needle and an extension thereof downstream, were observed only for the smallest radius. The simulations qualitatively confirmed these observations. As compared to performing the simulations without flow, including flow effects in the simulations reduced the mean absolute error between experimental and simulated ablated areas from 0.23 to 0.12.

CONCLUSION

While the temperature control mechanism did not detect the heat sink effect in the case of the smallest channel radius, it counteracted the heat sink effect in the case of the larger channel radii with an increased energy input; this explains the increase in ablated area toward high flow rates (for r = 2.3  mm). The experiments in a simple phantom setup, thus, contribute to a good understanding of the phenomenon and are suitable for model validation.

Linear radiofrequency ablation using dual switching-control mode achieves rapid and bloodless liver resection, an experimental research

BACKGROUND

Radiofrequency (RF)-assisted devices are widely used for hemostasis during liver resection. This study compared the use of dual switching (DS) versus single switching (SS) control modes for RF-based liver resections in a pig model.

METHODS

The RF-based system comprised a 200-W generator and three electrodes with 4-cm tips arranged in a linear configuration using an adaptor. Eight Lanyu pigs were used to assess ablation outcomes with electrode spacing of 2 or 3 cm, and ablation durations of 1.5, 2 or 3 min. All combinations were tested in DS and SS modes. Procedures were performed on left lateral, caudal and right anterior liver lobes, and after which transections were performed using a scalpel. Blood loss, complete ablation rate and ablation speed were compared.

RESULTS

DS mode was shown to induce significantly less blood loss than SS mode when the electrode spacing was set at 2 cm and the ablation duration was 2 min or 3 min (p=.010 and .012, respectively). Extended ablation duration and narrow electrode spacing tended to induce less blood loss, regardless of operating mode. Bloodless resection was achieved using DS mode with electrode spacing of 2 cm and ablation duration of 2-3 min. The highest rate of complete ablation (11.3 cm²/min) was achieved using DS mode with electrode spacing of 2 cm and ablation duration of 1.5 min.

CONCLUSION

RF-based hepatic resection using DS mode is safe and feasible, resulting in less blood loss than SS mode with a higher rate of complete ablation (i.e., superior ablation efficiency).

Modeling of Interstitial Ultrasound Ablation for Continuous Applicator Rotation With MR Validation

The primary objective of cancer intervention is the selective removal of malignant cells while conserving surrounding healthy tissues. However, the accessibility, size and shape of the cancer can make achieving appropriate margins a challenge. One minimally invasive treatment option for these clinical cases is interstitial needle based therapeutic ultrasound (NBTU). In this work, we develop a finite element model (FEM) capable of simulating continuous rotation of a directional NBTU applicator. The developed model was used to simulate the thermal deposition for different rotation trajectories. The actual thermal deposition patterns for the simulated trajectories were then evaluated using magnetic resonance thermal imaging (MRTI) in a porcine skin gelatin phantom. An MRI-compatible robot was used to control the rotation motion profile of the physical NBTU applicator to match the simulated trajectory. The model showed agreement when compared to experimental measurements with Pearson correlation coefficients greater than 0.839 when comparing temperature fields within an area of 12.6 mm radius from the ultrasound applicator. The average temperature error along a 6.3 mm radius profile from the applicator was 1.27 °C. The model was able to compute 1 s of thermal deposition by the applicator in 0.2 s on average with a 0.1 mm spatial resolution and 0.5 s time steps. The developed simulation demonstrates performance suitable for real-time control which may enable robotically-actuated closed-loop conformal tumor ablation.

Evolving role of minimally invasive techniques in the management of symptomatic bone metastases

PURPOSE OF REVIEW

Bone metastases are responsible for considerable morbidity, which can significantly limit a patient's quality of life. This article aims to review minimally invasive, image-guided locoregional treatments for symptomatic bone metastases as an adjunct to conventional treatment modalities.

RECENT FINDINGS

Conservative therapy and radiation therapy (RT) can be effective at addressing pain, however, they require time to achieve optimal efficacy and do not address the instability and progressive collapse of pathological fractures. Vertebral and pelvic augmentation with cement enhances structural stability and can prevent progressive collapse and deformity. Ablative therapies, including radiofrequency ablation (RFA), cryoablation, and photodynamic therapy (PDT), induce cellular destruction of tumor tissue. RFA and PDT can be combined with cement augmentation in a single sitting.

SUMMARY

Minimally invasive image-guided treatments can provide rapid pain relief, enhance mechanical stability, and improve quality of life. These treatments are associated with low complication rates and are suitable for frail patients. They can be used as companion procedures to conventional treatments, or function as an alternative for patients with radioresistant biologies or those with dose limitations from prior RT sessions.

Techniques for Temperature Monitoring of Myocardial Tissue Undergoing Radiofrequency Ablation Treatments: An Overview

Cardiac radiofrequency ablation (RFA) has received substantial attention for the treatment of multiple arrhythmias. In this scenario, there is an ever-growing demand for monitoring the temperature trend inside the tissue as it may allow an accurate control of the treatment effects, with a consequent improvement of the clinical outcomes. There are many methods for monitoring temperature in tissues undergoing RFA, which can be divided into invasive and non-invasive. This paper aims to provide an overview of the currently available techniques for temperature detection in this clinical scenario. Firstly, we describe the heat generation during RFA, then we report the principle of work of the most popular thermometric techniques and their features. Finally, we introduce their main applications in the field of cardiac RFA to explore the applicability in clinical settings of each method.

Role of Intraductal RFA: A Novel Tool in the Palliative Care of Perihilar Cholangiocarcinoma

Background

Patients with irresectable perihilar cholangiocarcinoma (PHC) have a limited prognosis with median survival times still less than 1 year. In addition to the current standard first-line systemic chemotherapy (gemcitabine and a platinum derivate), endoscopic treatment aims to ensure adequate drainage of the biliary system by placing biliary plastic or metal stents. Local ablative procedures like intraluminal biliary brachytherapy (ILBT) or photodynamic therapy (PDT) are used to improve local tumor control and to optimize the stent patency.

Summary

Intraductal radiofrequency ablation (RFA) is another promising tool in the therapeutic armamentarium for the endoscopic management and tumor ablation of extrahepatic cholangiocarcinoma (eCCA). By applying thermal energy to the tissue through high-frequency alternating current, RFA induces coagulative necrosis and causes local destruction of the tumor. It is established as a first line percutaneous treatment of solid liver tumors, and since 2011 an endoscopic catheter is available that allows intraductal RFA in the biliary or pancreatic ducts. While the first pilot studies primarily evaluated this new method in patients with distal eCCA, there is now evidence accumulating also for PHC. Two retrospective and two prospective studies demonstrated a significantly improved overall survival and a longer stent patency with intraductal RFA, which overall had a favorable safety profile and was not associated with a significant increase in adverse events. However, prospective studies comparing the efficacy and safety of intraductal RFA, PDT, and/or ILBT are lacking.

Key Messages

Recent studies suggest that intraductal RFA is an effective and well-tolerated additional treatment option with regard to stent patency but also overall survival. Since RFA has fewer systemic side effects and requires less logistical effort when compared to ILBT and PDT, intraductal RFA should be considered as another safe and feasible adjuvant method for the palliative care of patients with advanced PHC. Since comparative studies are lacking, the choice of the local ablative method remains in each case an individual decision.

A Single-Center Retrospective Analysis of Periprocedural Variables Affecting Local Tumor Progression after Radiofrequency Ablation of Colorectal Cancer Liver Metastases

Background Local tumor progression (LTP) is associated with poorer survival in patients undergoing radiofrequency ablation (RFA) for colorectal liver metastasis (CLM). An algorithmic strategy to predict LTP may help in selection of patients who would benefit most from RFA for CLM. Purpose To estimate local tumor progression-free survival (LTPFS) following RFA of CLM and develop an algorithmic strategy based on clinical variables. Materials and Methods In this retrospective study, between March 2000 and December 2014, patients who underwent percutaneous RFA for CLM were randomly split into development (60%) and internal validation (40%) data sets. Kaplan-Meier method was used to estimate LTPFS and overall survival (OS) rates. Independent factors affecting LTPFS in the development data set were investigated by using multivariable Cox proportional hazard regression analysis. Risk scores were assigned to the risk factors and applied to the validation data set. Results A total of 365 patients (mean age, 60 years ± 11 [standard deviation]; 259 men) with 512 CLMs were evaluated. LTPFS and OS rates were 85% and 92% at 1 year, 73% and 41% at 5 years, 72% and 30% at 10 years, and 72% and 28% at 15 years, respectively. Independent risk factors for LTP included tumor size of 2 cm or greater (hazard ratio [HR], 3.8; 95% CI: 2.3, 6.2; P < .001), subcapsular tumor location (HR, 1.9; 95% CI: 1.1, 3.1; P = .02), and minimal ablative margin of 5 mm or less (HR, 11.7; 95% CI: 4.7, 29.2; P < .001). A prediction model that used the risk factors had areas under the curve of 0.89, 0.92, and 0.90 at 1, 5, and 10 years, respectively, and it showed significantly better areas under the curve when compared with the model using the minimal ablative margin of 5 mm or less alone. Conclusion Radiofrequency ablation provided long-term control of colorectal liver metastases. Although minimal ablative margin of 5 mm or less was the most dominant factor, the multifactorial approach including tumor size and subcapsular location better predicted local tumor progression-free survival. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Soulen and Sofocleous in this issue.

Numerical Simulations as Means for Tailoring Electrically Conductive Hydrogels Towards Cartilage Tissue Engineering by Electrical Stimulation

Cartilage regeneration is a clinical challenge. In recent years, hydrogels have emerged as implantable scaffolds in cartilage tissue engineering. Similarly, electrical stimulation has been employed to improve matrix synthesis of cartilage cells, and thus to foster engineering and regeneration of cartilage tissue. The combination of hydrogels and electrical stimulation may pave the way for new clinical treatment of cartilage lesions. To find the optimal electric properties of hydrogels, theoretical considerations and corresponding numerical simulations are needed to identify well-suited initial parameters for experimental studies. We present the theoretical analysis of a hydrogel in a frequently used electrical stimulation device for cartilage regeneration and tissue engineering. By means of equivalent circuits, finite element analysis, and uncertainty quantification, we elucidate the influence of the geometric and dielectric properties of cell-seeded hydrogels on the capacitive-coupling electrical field stimulation. Moreover, we discuss the possibility of cellular organisation inside the hydrogel due to forces generated by the external electric field. The introduced methodology is easily reusable by other researchers and allows to directly develop novel electrical stimulation study designs. Thus, this study paves the way for the design of future experimental studies using electrically conductive hydrogels and electrical stimulation for tissue engineering.

Comparison of hydrochloric acid infusion radiofrequency ablation with microwave ablation in an ex vivo liver model

Objectives: To compare sizes and shapes of ablation zones resulting from hydrochloric acid infusion radiofrequency ablation (HRFA) and microwave ablation (MWA), using normal saline infusion radiofrequency ablation (NSRFA) as a control, at a variety of matched power settings and ablation durations, in an ex vivo bovine liver model.Methods: A total of 90 ablation procedures were performed, using each of three modalities: NSRFA, HRFA, and MWA. For each modality, five ablation procedures were performed for each combination of power (80 W, 100 W, or 120 W) and duration (5, 10, 20, 30, 45, or 60 min). The size of ablation zones were compared using ANOVA, the Kruskal-Wallis test, or generalized linear regression.Results: For ablation durations up to 30 min, mean transverse diameter (TD) after HRFA and MWA did not differ significantly (β = 0.13, p = .20). For ablation durations greater than 30 min, mean TD was significantly larger after HRFA than after MWA (β = 1.657, p < .001). The largest TD (9.46 cm) resulted from HRFA performed with 100 W power for 60 min.Conclusions: Compared to MWA, monopolar HRFA with power settings of 80 W-120 W and durations of less than 30 min showed no significant difference. When duration of more than 30 min, HRFA created larger ablation zones than MWA.

Direct treatment versus indirect: Thermo-ablative and mild hyperthermia effects

Hyperthermia is a rapidly growing field in cancer therapy and many advances have been made in understanding and applying the mechanisms of hyperthermia. Secondary effects of hyperthermia have been increasingly recognized as important in therapeutic effects and multiple studies have started to elucidate their implications for treatment. Immune effects have especially been recognized as important in the efficacy of hyperthermia treatment of cancer. Both thermo-ablative and mild hyperthermia activate the immune system, but mild hyperthermia seems to be more effective at doing so. This may suggest that mild hyperthermia has some advantages over thermo-ablative hyperthermia and research into immune effects of mild hyperthermia should continue. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Therapeutic Approaches and Drug Discovery > Emerging Technologies Implantable Materials and Surgical Technologies > Nanoscale Tools and Techniques in Surgery.

Hepatic Ablation Promotes Colon Cancer Metastases in an Immunocompetent Murine Model

OBJECTIVE

To determine the impact of radiofrequency (RF) and microwave (MW) energy compared to direct cautery on metatstatic colon cancer growth.

BACKGROUND

Hepatic ablation with MW and RF energy creates a temperature gradient around a target site with temperatures known to create tissue injury and cell death. In contrast, direct heat application (cautery) vaporizes tissue with a higher site temperature but reduced heat gradient on surrounding tissue. We hypothesize that different energy devices create variable zones of sublethal injury that may promote tumor recurrence. To test this hypothesis we applied MW, RF, and cautery to normal murine liver with a concomitant metastatic colon cancer challenge.

METHODS

C57/Bl6 mice received hepatic thermal injury with MW, RF, or cautery to create a superficial 3-mm lesion immediately after intrasplenic injection of 50K MC38 colon cancer cells. Thermal imaging recorded tissue temperature during ablation and for 10 seconds after energy cessation. Hepatic tumor location and volume was determined at day 7.

RESULTS

Cautery demonstrated the highest maximum tissue temperatures (129°C) with more rapid return to baseline compared to MW or RF energy. All mice had metastasis at the ablation site. Mean tumor volume was significantly greater in the MW (95.3 mm; P = 0.007) and RF (55.7 mm; P = 0.015) than cautery (7.13 mm). There was no difference in volume between MW and RF energy (P = 0.2).

CONCLUSIONS

Hepatic thermal ablation promotes colon cancer metastasis at the injury site. MV and RF energy result in greater metastatic volume than cautery. These data suggest that the method of energy delivery promotes local metastasis.

Bronchial Thermoplasty

Bronchial thermoplasty is an advanced therapy for severe asthma. It is a bronchoscopic procedure in which radiofrequency energy is applied to the airway wall, resulting in decreased airway smooth muscle burden. Human trials have shown that bronchial thermoplasty may reduce asthma exacerbations and improve quality of life in patients with severe uncontrolled asthma. It has been demonstrated to be a safe procedure, with most adverse events being early and mild. More studies are required to understand the precise effects of bronchial thermoplasty on the asthmatic airway and optimal parameters to appropriately select patients for this novel procedure.

Pictorial Imaging-Histopathology Correlation in a Rabbit with Hepatic VX2 Tumor Treated by Transarterial Vascular Disrupting Agent Administration

Cancer vasculature is immature, disorganized and hyperpermeable and can serve as a target for anti-cancer therapies. Vascular disrupting agents (VDAs) are tubulin protein binding and depolymerizing agents that induce rapid tumoral vascular shutdown and subsequent cancer necrosis. However, two clinical problems exist with all VDAs, i.e. 1) incomplete anticancer effect and 2) dose-dependent toxicity. To tackle these problems, in our ongoing research, a novel VDA C118P is applied by transarterial administration of half the intravenous dose in rabbits with implanted VX2 liver tumor to assess its therapeutic efficacy. Nearly complete tumor necrosis was achieved by only a single arterial dose of C118P at 5 mg/kg, which was documented in a representative case by in vivo digital subtraction arteriogram (DSA) and magnetic resonance imaging (MRI), and further confirmed by ex vivo microangiogram and histopathology. This convincing and promising preliminary outcome would warrant further comprehensive studies to explore the potentials of VDAs by transarterial administration either in mono-drug or in combination for management of solid cancers.

A Review on Curability of Cancers: More Efforts for Novel Therapeutic Options Are Needed

Cancer remains a major cause of death globally. Given its relapsing and fatal features, curing cancer seems to be something hardly possible for the majority of patients. In view of the development in cancer therapies, this article summarizes currently available cancer therapeutics and cure potential by cancer type and stage at diagnosis, based on literature and database reviews. Currently common cancer therapeutics include surgery, chemotherapy, radiotherapy, targeted therapy, and immunotherapy. However, treatment with curative intent by these methods are mainly eligible for patients with localized disease or treatment-sensitive cancers and therefore their contributions to cancer curability are relatively limited. The prognosis for cancer patients varies among different cancer types with a five-year relative survival rate (RSR) of more than 80% in thyroid cancer, melanoma, breast cancer, and Hodgkin's lymphoma. The most dismal prognosis is observed in patients with small-cell lung cancer, pancreatic cancer, hepatocellular carcinoma, oesophagal cancer, acute myeloid leukemia, non-small cell lung cancer, and gastric cancer with a five-year RSR ranging between 7% and 28%. The current review is intended to provide a general view about how much we have achieved in curing cancer as regards to different therapies and cancer types. Finally, we propose a small molecule dual-targeting broad-spectrum anticancer strategy called OncoCiDia, in combination with emerging highly sensitive liquid biopsy, with theoretical curative potential for the management of solid malignancies, especially at the micro-cancer stage.

New Therapies for Emerging Endotypes of Asthma

The presentation, pathobiology, and prognosis of asthma are highly heterogeneous and challenging for clinicians to diagnose and treat. In addition to the adaptive immune response that underlies allergic inflammation, innate immune mechanisms are increasingly recognized to be critical mediators of the eosinophilic airway inflammation present in most patients with asthma. Efforts to classify patients by severity and immune response have identified a number of different clinical and immune phenotypes, indicating that the innate and adaptive immune responses are differentially active among patients with the disease. Advances in the detection of these subgroups using clinical characteristics and biomarkers have led to the successful development of targeted biologics. This has moved us to a more personalized approach to managing asthma. Here we review the emerging endotypes of asthma and the biologics that have been developed to treat them.

Large placental chorioangioma: a potential effective in-utero treatment modality for radio frequency ablation

Background

Placenta chorioangiomas are common benign placental tumours. While microscopic chorioangiomas are frequent, macroscopic chorioangiomas of more than 5 cm are rare and often associated with fetal complications such as high output cardiac failure, fetal anaemia and stillbirth. Close monitoring and in-utero treatment are sometimes necessary to prevent adverse pregnancy outcome.

Case presentation

We present two cases of large placenta chorioangiomas with one case requiring surgical therapy with radiofrequency ablation (RFA) of tumour vessels, which resulted in a successful outcome of a live birth at term.

Conclusion

We conclude that RFA is an effective alternative treatment modality to fetoscopic laser therapy in utero for cases at risk of fetal cardiac failure and intrauterine demise in the presence of large chorioangiomas.

Photoacoustic imaging in percutaneous radiofrequency ablation: device guidance and ablation visualization

Percutaneous radiofrequency ablation (RFA) is gaining importance as a locoregional treatment for tumors in several organs including the liver, lung, kidney and bone. In RFA, the tumor is eradicated with the direct application of heat using alternating current through a needle electrode positioned under imaging guidance. Various imaging methods are used in the RFA ablation procedure but these have drawbacks. In this work, we introduce photoacoustic (PA) imaging as a new method with potential to visualize the targeting of RFA needle into a region of interest and to report on the extent of ablation achieved. We demonstrate the proof-of-concept in using PA imaging together with ultrasound imaging on ex vivo biological samples in the laboratory simulating relevant clinical scenarios in RFA. These include guidance of the RFA needle to target tissue, mapping of simulated blood vessels during needle insertion and differentiation between ablated and surrounding tissue. The results of this first investigation into the use of PA imaging to assist RFA procedures are encouraging. We discuss the challenges encountered, the scope for future work and envisaged clinical application.

The combination of electroporation and electrolysis (E2) employing different electrode arrays for ablation of large tissue volumes

Background

The combination of electroporation with electrolysis (E2) has previously been introduced as a novel tissue ablation technique. E2 allows the utilization of a wide parameter range and may therefore be a suitable technology for development of tissue-specific application protocols. Previous studies have implied that it is possible to achieve big lesions in liver in a very short time. The goal of this study was to test a variety of electrode configurations for the E2 application to ablate large tissue volumes.

Materials and methods

27 lesions were performed in healthy porcine liver of five female pigs. Four, two and bipolar electrode-arrays were used to deliver various E2 treatment protocols. Liver was harvested approx. 20h after treatment and examined with H&E and Masson’s trichrome staining, and via TUNEL staining for selective specimen.

Results

All animals survived the treatments without complications. With four electrodes, a lesion of up to 35x35x35mm volume can be achieved in less than 30s. The prototype bipolar electrode created lesions of 50x18x18mm volume in less than 10s. Parameters for two-electrode ablations with large exposures encompassing large veins were found to be good in terms of vessel preservation, but not optimal to reliably close the gap between the electrodes.

Conclusion

This study demonstrates the ability to produce large lesions in liver within seconds at lower limits of the E2 parameter space at different electrode configurations. The applicability of E2 for single electrode ablations was demonstrated with bipolar electrodes. Parameters for large 4-electrode ablation volumes were found suitable, while parameters for two electrodes still need optimization. However, since the parameter space of E2 is large, it is possible that for all electrode geometries optimal waveforms and application protocols for specific tissues will emerge with continuing research.

Rhein-based necrosis-avid MRI contrast agents for early evaluation of tumor response to microwave ablation therapy

PURPOSE

Early evaluation of tumor response to thermal ablation therapy can help identify untreated tumor cells and then perform repeated treatment as soon as possible. The purpose of this work was to explore the potential of rhein-based necrosis-avid contrast agents (NACAs) for early evaluation of tumor response to microwave ablation (MWA).

METHODS

3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay was performed to test the cytotoxicity of rhein-based NACAs against HepG2 cells. Rat models of liver MWA were used for investigating the effectiveness of rhein-based NACAs in imaging the MWA lesion, the optimal time period for post-MWA MRI examination, and the metabolic behaviors of ⁶⁸ Ga-labeled rhein-based NACAs. Rat models of orthotopic liver W256 tumor MWA were used for investigating the time window of rhein-based NACAs for imaging the MWA lesion, the effectiveness of these NACAs in distinguishing the residual tumor and the MWA lesion, and their feasibility in early evaluating the tumor response to MWA.

RESULTS

Gadolinium 2,2',2''-(10-(2-((4-(4,5-Dihydroxy-9,10-dioxo-9,10-dihydroanthracene-2-carboxamido)butyl)amino)-2-oxoethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetic acid (GdL₂ ) showed low cytotoxicity and high quality in imaging the MWA region. The optimal time period for post-MWA MRI examination using GdL₂ was 2 to 24 h after the treatment. During 2.5 to 3.5 h postinjection, GdL₂ can better visualize the MWA lesion in comparison with gadolinium 2-[4,7,10-tris(carboxymethyl)-1,4,7,10-tetraazacyclododec-1-yl]acetic acid (Gd-DOTA), and the residual tumor would not be enhanced. The tumor response to MWA as evaluated by using GdL₂ -enhanced MRI was consistent with histological examination.

CONCLUSION

GdL₂ appears to be a promising NACA for the tumor response assessment after thermal ablation therapies.

Ultrasound-guided radiofrequency ablation for treatment of Morton's neuroma: initial experience

AIM

To assess the efficacy and safety of ultrasound-guided radiofrequency ablation (RFA) for treatment of symptomatic Morton's neuroma.

MATERIALS AND METHODS

Patients with symptomatic Morton's neuroma of the foot were referred for treatment with RFA, prior to consideration for surgery. All neuromas were proven by ultrasound imaging and had a trial of conservative management including orthotic support and/or steroid injections. Ultrasound-guided RFA was performed as an outpatient procedure under local anaesthetic. Patients were followed up at 8 weeks and 8 months. Outcomes were assessed with a visual analogue scale (VAS) score, Manchester-Oxford Foot and Ankle Questionnaire, overall patient satisfaction, and complications.

RESULTS

Twenty-two neuromas were treated with RFA under ultrasound guidance. The VAS score at 8 weeks was significantly lower than the VAS score pre-procedure (p<0.001, Wilcoxon signed ranks test) and the VAS score at 8 months was significantly lower than the VAS score at 8 weeks (p=0.008, Wilcoxon signed ranks test). At 8 months, 89% of treated patients were satisfied with the procedure outcome. No significant adverse effects were recorded.

CONCLUSION

Ultrasound-guided RFA is safe, with excellent initial results in treatment of symptomatic Morton's neuroma. Further studies on long-term outcomes and comparison to other management options will be required to establish its role in management of symptomatic Morton's neuroma.

For Whom the Bubble Grows: Physical Principles of Bubble Nucleation and Dynamics in Histotripsy Ultrasound Therapy

Histotripsy is a focused ultrasound therapy for non-invasive tissue ablation. Unlike thermally ablative forms of therapeutic ultrasound, histotripsy relies on the mechanical action of bubble clouds for tissue destruction. Although acoustic bubble activity is often characterized as chaotic, the short-duration histotripsy pulses produce a unique and consistent type of cavitation for tissue destruction. In this review, the action of histotripsy-induced bubbles is discussed. Sources of bubble nuclei are reviewed, and bubble activity over the course of single and multiple pulses is outlined. Recent innovations in terms of novel acoustic excitations, exogenous nuclei for targeted ablation and histotripsy-enhanced drug delivery and image guidance metrics are discussed. Finally, gaps in knowledge of the histotripsy process are highlighted, along with suggested means to expedite widespread clinical utilization of histotripsy.

Endoscopic Retrograde Cholangiopancreatography-Guided Ablation for Cholangiocarcinoma

Most patients with perihilar cholangiocarcinoma present with surgically unresectable disease owing to the insidious nature of this malignancy. Relief of malignant perihilar biliary obstruction is a key aspect of cholangiocarcinoma. Although palliative stenting using uncovered metal stents has been advocated in patients with unresectable malignant perihilar biliary strictures, several endoscopic retrograde cholangiopancreatography-guided ablative modalities have emerged. Palliative photodynamic therapy, radiofrequency ablation, and intraluminal brachytherapy have been associated with improved stent patency and survival, although the ideal treatment approach remains unclear. This article reviews the published evidence for using each of these endobiliary ablative modalities in this difficult-to-treat patient population.

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.

External stimulus responsive inorganic nanomaterials for cancer theranostics

Cancer is a highly intelligent system of cells, that works together with the body to thrive and subsequently overwhelm the host in order for its survival. Therefore, treatment regimens should be equally competent to outsmart these cells. Unfortunately, it is not the case with current therapeutic practices, the reason why it is still one of the most deadly adversaries and an imposing challenge to healthcare practitioners and researchers alike. With rapid nanotechnological interventions in the medical arena, the amalgamation of diagnostic and therapeutic functionalities into a single platform, theranostics provides a never before experienced hope of enhancing diagnostic accuracy and therapeutic efficiency. Additionally, the ability of these nanotheranostic agents to perform their actions on-demand, i.e. can be controlled by external stimulus such as light, magnetic field, sound waves and radiation has cemented their position as next generation anti-cancer candidates. Numerous reports exist of such stimuli-responsive theranostic nanomaterials against cancer, but few have broken through to clinical trials, let alone clinical practice. This review sheds light on the pros and cons of a few such theranostic nanomaterials, especially inorganic nanomaterials which do not require any additional chemical moieties to initiate the stimulus. The review will primarily focus on preclinical and clinical trial approved theranostic agents alone, describing their success or failure in the respective stages.

Recent Advances in the Image-Guided Tumor Ablation of Liver Malignancies: Radiofrequency Ablation with Multiple Electrodes, Real-Time Multimodality Fusion Imaging, and New Energy Sources

Radiofrequency ablation (RFA) has emerged as an effective loco-regional treatment modality for malignant hepatic tumors. Indeed, studies have demonstrated that RFA of early stage hepatocellular carcinomas can provide comparable overall survival to surgical resection. However, the incidence of local tumor progression (LTP) after RFA is significantly higher than that of surgical resection. Thus, to overcome this limitation, multiple electrode radiofrequency (RF) systems that use a multi-channel RF generator have been developed, and they demonstrate better efficiency in creating larger ablation zones than that using the conventional RFA with a single electrode. Furthermore, RFA with multiple electrodes can allow the “no-touch” ablation technique which may also help to reduce LTP. Another technique that would be helpful in this regard is multi-modality-ultrasound fusion imaging, which helps to not only more accurately determine the target lesion by enabling the RFA of small, poorly visible or invisible tumors, but also improve the monitoring of procedures and determine the appropriateness of the ablation margin. In addition, new energy sources, including microwave and cryoablation, have been introduced in imaging-guided tumor ablation. In this review, these recently introduced ablation techniques and the results of the most current animal and clinical studies are discussed.

Increasing radiofrequency ablation volumes with the use of internally cooled electrodes and injected hydrochloric acid in ex vivo bovine livers

PURPOSE

We used an impedance-controlled generator with an internally cooled electrode to perform radiofrequency ablation (RFA) in ex vivo bovine livers, with a single injection of either 38.5% sodium chloride (NaCl) or 10% hydrochloric acid (HCl), to determine the relative effects of these two solutions on tissue impedance, temperature and ablation volume.

MATERIALS AND METHODS

We performed 10 ablations each with injections of NaCl (NaCl-RFA), HCl (HCl-RFA) or nothing (RFA-alone), with a power setting of 200 W for 15 minutes. We recorded tissue impedance before and after injection. We logged temperatures obtained from thermocouple probes positioned 5, 10, 15 and 20 mm from the internally cooled RF electrode. After ablation, we measured ablation zone longitudinal and transverse diameters, and we calculated a spherical ratio (SR) for each ablation.

RESULTS

Mean post-injection impedance of 30.3 (standard deviation [SD] 2.5) ohms for HCl was significantly lower than that of 55.4 (SD 3.5) ohms for NaCl (p < .001). Mean maximum temperatures recorded at each respective distance from the RFA electrode were all highest for HCl-RFA and lowest for RFA-alone (p < .001). Mean longitudinal and transverse diameters after HCl-RFA (5.50 [SD 0.25] cm and 5.28 [SD 0.22] cm, respectively) were significantly larger than those after NaCl-RFA (4.24 [SD 0.35] cm and 3.55 [SD 0.43] cm, respectively) and after RFA-alone (3.60 [SD 0.10] cm and 2.70 [SD 0.13] cm, respectively) (p < .001). Mean SR after HCl-RFA (0.93, SD 0.02) was significantly higher than mean SR after NaCl-RFA (0.76, SD 0.06) and RFA-alone (0.72, SD 0.04) (p < .001).

CONCLUSION

Monopolar, impedance-controlled RFA, with an internally cooled electrode and a single 10% HCl injection may allow larger tumors to be treated, potentially resulting in improved patient outcomes.

Time and temperature dependence of radiofrequency ablation in the human placenta

OBJECTIVE

The objective of the study is to compare radiofrequency (RF) effects on fresh placentae with varying levels of sustained time (Ts) and degrees of target temperature (°t).

METHOD

A total of 108 pieces of fresh placentae were coagulated with a 2-cm RF needle at 60 W in an organ bath. The vertical and horizontal diameters (Vd, Hd) of tissue coagulation visualized by ultrasound were measured. The impacts of 12 different Ts-°t combinations on the ablation size ascertained on pathological examination (Vd_p , Hd_p ) were compared using 2-way ANOVA. The agreement between sonographic and pathological findings was assessed using Bland-Altman analysis.

RESULTS

Considerable changes in the Vd_p and Hd_p were associated with increasing the Ts and °t. The impact of RF on tissue coagulation was greatest when the °t was set at 100°C, with further destruction as the Ts progressed to 7 minutes of exposure. The ablation size estimated by ultrasound exhibited an overestimation by an average of 5.65% and 21.02% for Vd and Hd, respectively.

CONCLUSION

A prolonged Ts at a higher °t contributes to progressive placental tissue destruction by RF, with maximum destruction at 100°C for 7 minutes in an ex vivo nonperfused placenta. Tissue injury that is apparent on ultrasound may extend beyond pathological damage.

Three Cycles of Radiofrequency Ablation Are More Efficacious Than Two in the Management of Morton's Neuroma

BACKGROUND

Morton's neuroma is a common cause of forefoot pain. Outcomes of conservative therapy are mixed and many patients undergo operative intervention. Radiofrequency ablation has recently gained favor as a treatment option, although the optimal regime is unknown. This study investigates the effectiveness of 2 versus 3 cycles of radiofrequency ablation for the treatment of Morton's neuroma.

METHODS

We surveyed a cohort of patients with Morton's neuroma who had progressed to radiofrequency ablation after failed conservative treatment. Patients received either 2 or 3 cycles of radiofrequency ablation by a single surgeon. We assessed patients based on their change in numerical pain rating scale, symptom improvement, complications, and progression to surgical excision through a series of telephone interviews. Outcomes between the 2 treatment arms were compared by parametric tests.

RESULTS

Twenty-eight patients were included in the study. Eighteen patients with 21 neuromas received 2 cycles and 10 patients with 11 neuromas received 3 cycles. Mean time of follow-up was 12.9 months. Overall, 88% of patients were either very or moderately satisfied with their outcome. In patients who received 2 cycles mean numerical pain scores decreased from 7.9 ± 1.1 to 3.4 ± 2.4 postprocedure. Three patients progressed to operative excision. In patients who received 3 cycles, numerical pain scores decreased from 8.0 ± 1.0 to 1.5 ± 2.0 postprocedure. One patient progressed to operative excision. Patients who received 3 cycles had reduced medium-term pain postoperatively compared with 2 cycles (3.4 ± 2.4 vs 1.5 ± 2.0, P = .011).

CONCLUSION

Radiofrequency ablation provides a high rate of patient satisfaction in the treatment of Morton's neuroma with few side effects. It appears that 3 cycles may be superior to 2 cycles but a randomized controlled trial will be required to confirm these results.

LEVELS OF EVIDENCE

Intervention, Level III: Comparative study without concurrent controls.

A Phase II Study of Tumor Ablation in Patients with Metastatic Sarcoma Stable on Chemotherapy

Lessons Learned.

Ablation therapy appears to be a reasonably safe and effective approach to obtain a significant treatment‐free interval for a subset of patients with limited sites of metastatic disease for which systemic control can be obtained with six cycles of chemotherapy.

Background.

Metastatic sarcoma often becomes resistant to treatment by chemotherapy. There is sometimes prolonged stable disease from active chemotherapy that provides a window of opportunity for an intervention to prolong disease‐free survival.

Materials and Methods.

We performed a phase II study in patients with metastatic sarcoma who had been stable on six cycles of chemotherapy who then received ablation therapy to their residual disease. Histologies captured in this study included leiomyosarcoma, malignant peripheral nerve sheath tumor, pleiomorphic rhabdomyosarcoma, and myxoid liposarcoma. Sites ablated included lung metastases and retroperitoneal metastatic deposits. In this study, up to three lesions were ablated in any given interventional radiology session. After ablation, patients were not treated with any further therapy but were followed by surveillance imaging to determine progression‐free rate (PFR).

Results.

Although terminated early because of slow accrual, this study demonstrated a 3‐month PFR of 75% for this cohort of eight patients treated with ablation performed after completion of six cycles of chemotherapy with stable disease. Median progression‐free survival (PFS) was 19.74 months, and the median overall survival (OS) was not reached.

Conclusion.

Our data are the first prospective study to suggest that ablation therapy in selected patients who are stable on chemotherapy can provide a significant progression‐free interval off therapy and warrants further study in a randomized trial.

Safety and effect on ablation size of hydrochloric acid-perfused radiofrequency ablation in animal livers

PURPOSE

Our objective was to determine the safety and ablation size of hydrochloric acid-perfused radiofrequency ablation (HCl-RFA) in liver tissues, prospectively using in vivo rabbit and ex vivo porcine liver models.

MATERIALS AND METHODS

The livers in 30 rabbits were treated in vivo with perfusions of normal saline (controls) and HCl concentrations of 5%, 10%, 15%, and 20%, during RFA at 103 °C and 30 W for 3 min. For each experimental setting, six ablations were created. Safety was assessed by comparing baseline weight and selected laboratory values with those at 2, 7, and 14 days' post-ablation, and by histopathological analysis. The livers in 25 pigs were treated ex vivo with the same five perfusions during RFA at 103 °C, at both 30 W and 60 W, for 30 min. Ablation diameters and volumes were measured by two examiners.

RESULTS

Rabbit weights and selected laboratory values did not differ significantly from baseline to 7 and 14 days' post-ablation, liver tissues outside the ablation zones were normal histologically, and adjacent organs showed no macroscopic damage. The mean ablation volumes in the porcine livers treated with HCl-RFA were all larger than those treated with normal saline perfusion during RFA (NS-RFA), at both 30 W and 60 W (p < 0.001). The largest ablation volume and transverse diameter were observed in the porcine livers during 10% HCl-RFA at 60 W, measuring 179.22 (SD = 24.79) cm³ and 6.84 (SD = 0.36) cm, respectively.

CONCLUSIONS

Based on our experiments, HCl-RFA in the liver appears to be as safe as NS-RFA while also resulting in larger ablation zones.

Improved therapeutic outcomes of thermal ablation on rat orthotopic liver allograft sarcoma models by radioiodinated hypericin induced necrosis targeted radiotherapy

Residual tumor resulting in tumor recurrence after various anticancer therapies is an unmet challenge in current clinical oncology. This study aimed to investigate the hypothesis that radioiodinated hypericin (131I-Hyp) may inhibit residual tumor recurrence after microwave ablation (MWA) on rat orthotopic liver allograft sarcoma models.Thirty Sprague-Dawley (SD) rats with hepatic tumors were divided into three groups: Group A received laparotomy MWA and sequential intravenous injection (i.v.) of 131I labelled hypericin (131I-Hyp) in a time interval of 24 h; Group B received only laparotomy MWA; Group C was a blank control. Tumor inhibitory effects were monitored with in vivo magnetic resonance imaging (MRI) and these findings were compared to histopathology data before (baseline, day 0) and 1, 4, and 8 days after MWA. In addition, biodistribution of 131I-Hyp was assessed with in vivo single-photon emission computed tomography-computed tomography (SPECT-CT) imaging, in vitro autoradiography, fluorescent microscopy, and gamma counting.A fast clearance of 131I-Hyp and increasing deposit in necrotic tumors appeared over time, with a significantly higher radioactivity than other organs (0.9169 ± 1.1138 % ID/g, P < 0.01) on day 9. Tumor growth was significantly slowed down in group A compared to group B and C according to MRI images and corresponding tumor doubling time (12.13 ± 1.99, 4.09 ± 0.97, 3.36 ± 0.72 days respectively). The crescent tagerability of 131I-Hyp to necrosis was visualized consistently by autoradiography and fluorescence microscopy.In conclusion, 131I-Hyp induced necrosis targeted radiotherapy improved therapeutic outcomes of MWA on rat orthotopic liver allograft sarcoma models.