Larger Ablation Research Articles

Percutaneous radiofrequency versus microwave ablation for the treatment of colorectal liver metastases.

401 Background: Microwave (MWA) and radiofrequency (RFA) ablation are commonly used for the treatment of unresectable liver metastases from colorectal cancer (CRC). MWA has a few theoretical advantages over RFA (active heating, less affected by heat sink effect, larger ablation zones, faster) however limited data exists on this field. Our aim was to analyse the safety and efficacy of MWA and RFA in the treatment of CRC liver metastases. Methods: All patients with unresectable CRC liver metastasis who were treated with RFA or MWA in a single center between March 2006 and December 2016 were included. Medical records and imaging studies were reviewed retrospectively for demographic data, to assess for local tumour recurrence and overall survival and to evaluate ablation-related adverse events. Results: 456 ablations were performed in 193 patients (123 men) with a median age of 66 (range 32-91). The majority of patients had a history of surgery of the primary tumour (n=170, 88,1%) and systemic chemotherapy (n=183, 94,8%). 68 patients had a history of liver surgery (35,2%). RFA was used in 343 procedures (75,2%) and MWA in 113 (24,8%). Median number of procedures per patient was 2 (range 1-10). Median lesion size was 17mm (range 3-80mm). Mean follow-up per lesion was 2.0 years in the RFA group and 1.3 years in the MWA group. Local tumour recurrence rate was 45% for RFA and 28% for MWA, with a hazard ratio of 0.6 in favour of MWA (95% CI 0.4-0.9). Two and five year overall survival rates from diagnosis of liver metastasis were 88% and 35% for RFA and 89% and 66% for MWA, respectively. Complications were reported in 43 of 456 procedures (9,4%); In 8,2% of RFAs (n=28) and 13,3% of MWAs (n=15). Complications classified as CTCAE grade 3 or higher were: haemothorax requiring surgery (n=1 for RFA), biloma (n=2 for RFA & MWA), biliary stricture (n=2 for RFA and n=1 MWA), liver failure (n=2 for RFA), liver abscess (n=1 RFA), pneumonia (n=2 for RFA) and pulmonary embolism (n=1 RFA). Segmental portal vein occlusion was only seen with MWA (n=2; 1,8%). One patient died due to multi-organ failure post RFA. Conclusions: MWA could achieve better local tumour control compared with RFA in the treatment of CRC liver metastasis, with slightly higher complication rate.

Thromboembolic prophylaxis protocol with warfarin after radiofrequency catheter ablation of infarct-related ventricular tachycardia.

Ablation in the left ventricle (LV) is associated with a risk of thromboembolism. There are limited data on the use of specific thromboembolic prophylaxis strategies postablation. We aimed to evaluate a thromboembolic prophylaxis protocol after ventricular tachycardia (VT) ablation. The index procedures of 217 patients undergoing ablation for infarct-related VT with open irrigated-tip catheters were included. Patients with large LV endocardial ablation area (>3cm between ablation lesions) were started on low-dose, slowly escalating unfractionated heparin (UFH) infusion 8hours after access hemostasis, followed by 3months of anticoagulation. Patients with less extensive ablation were treated only with antiplatelet agents postablation. Postablation bridging anticoagulation was used in 181 (83%) patients. Of them, 11 (6%) patients experienced bleeding events (1 required endovascular intervention) and 1 (0.6%) experienced lower extremity arterial embolism requiring vascular surgery. Systemic anticoagulation was prescribed in 190 (89%) of 214 patients discharged from the hospital (warfarin in 98%), while the rest received single- or dual-antiplatelet therapy alone. Patients treated with an anticoagulant had significantly longer radiofrequency time compared to patients treated with antiplatelet agents only. One (0.5%) of the patients treated with oral anticoagulation experienced major bleeding 2 weeks postablation. No thromboembolic events were documented in either the anticoagulation or the "antiplatelet only" group postdischarge. A slowly escalating bridging regimen of UFH, followed by 3months of oral anticoagulation, is associated with low thromboembolic and bleeding risks after infarct-related VT ablation. In the absence of extensive ablation, antiplatelet therapy alone is reasonable.

Optimization of Electrode Configuration and Pulse Strength in Irreversible Electroporation for Large Ablation Volumes Without Thermal Damage

The aim of this study was to analyze five factors that are responsible for the ablation volume and maximum temperature during the procedure of irreversible electroporation (IRE). The five factors used in this study were the pulse strength (U), the electrode diameter (B), the distance between the electrode and the center (D), the electrode length (L), and the number of electrodes (N). A validated finite element model (FEM) of IRE was built to collect the data of the ablation volume and maximum temperature generated in a liver tissue. Twenty-five experiments were performed, in which the ablation volume and maximum temperature were taken as response variables. The five factors with ranges were analyzed to investigate their impacts on the ablation volume and maximum temperature, respectively, using analysis of variance. Response surface method (RSM) was used to optimize the five factors for the maximum ablation volume without thermal damage (the maximum temperature ≤ 50 °C for 90 s). U and L were found with significant impacts on the ablation volume (P < 0.001, and P = 0.009, respectively) while the same conclusion was not found for B, D and N (P = 0.886, P = 0.075 and P = 0.279, respectively). Furthermore, U, D, and N had the significant impacts on the maximum temperature with P < 0.001, P < 0.001, and P = 0.003, respectively, while same conclusion was not found for B and L (P = 0.720 and P = 0.051, respectively). The maximum ablation volume of 2952.9960 mm3 without thermal damage can be obtained by using the following set of factors: U = 2362.2384 V, B = 1.4889 mm, D = 7 mm, L = 4.5659 mm, and N = 3. The study concludes that both B and N have insignificant impacts (P = 0.886, and P = 0.279, respectively) on the ablation volume; U has the most significant impact (P < 0.001) on the ablation volume; electrode configuration and pulse strength in IRE can be optimized for the maximum ablation volume without thermal damage using RSM.

EUS-guided radiofrequency ablation: an option for the extrapancreatic region.

Radiofrequency ablation (RFA) achieves tumor necrosis by cell protein denaturation, induced by tissue heating above 45°C to obtain irreversible cellular injury. Energy is supplied by a generator connected to an active electrode tip inserted into the tumor. RFA was developed in the early nineties for percutaneous or intraoperative treatment of hepatocellular carcinoma (HCC). It is recommended by the EASL–EORTC Clinical Practice Guidelines for early-stage disease (not eligible for surgery).[1] Today, RFA is widely used in the treatment of HCC and has been given attention as a potential treatment for many tumors (e.g., kidney, lung, and bone). Recently, new devices have been used to perform RFA through linear echoendoscopes, for targeting focal pancreatic lesions (neuroendocrine tumors, adenocarcinomas, and pancreatic cysts).[234] Moreover, the left lobe of the liver can be well visualized using endoscopic ultrasound (EUS), making it amenable to EUS-guided interventional procedures, including ablations.[5] A 76-year-old HBV/HCV-cirrhotic female presenting with portal hypertension and ascites had been diagnosed with HCC on radiological imaging (Barcelona Clinic Liver Cancer Stage A: Child–Pugh B8/Performance status: 1), but she was deemed unfit for surgery. She was, therefore, referred for EUS-guided sampling of hilar lymph nodes, in view of further management of a suspicious HCC in the fourth segment of her liver [Figure 1a–c]. Sampling of the hepatic nodule and the lymph nodes resulted in a diagnosis of well-differentiated HCC and reactive adenopathies [Figure 2].Figure 1: Abdominal computed tomography shows a 30-mm nodule with diffuse hyperenhancement in the arterial phase, and slow wash out in the portal and late phases (a-c). After 1 month, an abdominal computed tomography scan shows a large ablated area in the arterial, portal, and late phases (d-f)Figure 2: High-power images show pseudoglandular aggregates of atypical epithelial cells (a) (H and E, ×400). Gomori's staining (b) highlights the presence of neoplastic pseudoglandular structures (×400). CD34 immunostaining demonstrates sinusoidal capillarization (c), a typical change that characterizes the endothelial cells of hepatocellular carcinoma (×200)Considering the easy approach provided by EUS and obstacles to the percutaneous route (large umbilical hernia), the nodule was ablated with EUS guidance (GIF-160 Olympus, Tokyo, Japan) using a 20-mm active tip water-cooled electrode needle (EUSRA™ RF Electrode-VIVA RF Generator, STARmed, Seoul Korea). The procedure required three passes at five positions, using a multi-pass technique that allowed a larger ablation. Video 1 shows the insertion of the needle inside the HCC and the development of air bubbles near the electrode tip (first pass). Later, a panoramic view shows a large hyperechoic halo occupying the nodule. This marked the conclusion of the procedure, after a total of 30 min of energy application (starting power 30 W). An ultrasound imaging contrast (Sonovue®, Bracco, Italy) was administered during the procedure for marking the ablated area (nonenhancing tissue) and targeting further insertions. No adverse event was observed, and the patient was discharged on the 3rd postoperative day. One month later, computed tomography scan showed a large ablated area [Figure 1d–f]. This case highlights the possibilities for an EUS-guided transluminal approach to perform RFA of extrapancreatic neoplasms, such as a liver lesion, when percutaneous or surgical treatments are technically challenging or prohibitive. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form the patient has given her consent for her images and other clinical information to be reported in the journal. The patient understands that her name and initial will not be published and due efforts will be made to conceal her identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.

THE SIMULATION STUDY ON THE DEFORMATION OF RABBIT CORNEA AFTER REFRACTIVE SURGERY WITH DIFFERENT CUTTING THICKNESS

Based on the inflation tests data of rabbit cornea, finite element analysis has been applied to determine the material parameters, simulate corneal refractive surgery and study postoperative corneal deformations. The corneal profile and apical displacement data were recorded during the inflation experiment of five rabbit corneas. Inverse finite element method was applied to determine the material parameters from the corneal apical displacements. Based on the determined material parameters and the corneal profile information, we established five corneal geometry models that simulate refractive surgery with different cutting amounts. We analyzed displacements at corneal apex and cutting edge, corneal surface curvatures under different pressures. Both Ogden model ([Formula: see text]) and Yeoh model ([Formula: see text]) gave good fits to the experiment data. The maximum of error square sum between the calculated value and the experimental value of the displacements per point at the corneal profile was less than 0.06[Formula: see text]mm. For each model with the increase of pressure, the displacement at cutting edge was larger than that at corneal apex, both of them increased, and curvature radius of anterior and posterior corneal surface increased slowly, but the refractive power decreased slowly and tended to be a stable value. Under the same pressure, the larger the cutting amount, the larger the displacements at corneal apex and cutting edge with a cutting edge displacement of about 1.10 (less ablation model) and 1.02 (larger ablation model) times the corneal vertex displacement. Both Ogden model and Yeoh model can be used to describe corneal mechanical responses of inflation experiment. After refractive surgery, the displacement at cutting edge is larger than that at corneal apex, the curvature radius of anterior (posterior) corneal surface increases (decreases), and the refractive power decreases.

215 Laser Thermal Ablation for Mesiotemporal Epilepsy

Abstract INTRODUCTION Laser interstitial thermal therapy (LiTT) has dramatically changed the management of mesiotemporal epilepsy (mTLE) in recent years. The goal of this study was to identify features of ablations and trajectories that correlate with optimal seizure control and minimize the risk of neurocognitive deficits in patients undergoing LiTT for mTLE. METHODS Clinical and radiographic data were reviewed from a prospectively maintained database of patients undergoing LiTT for epilepsy at the University of Miami. Standard preoperative and postoperative evaluations, including contrast-enhanced MRI and neurocognitive testing, were performed in all patients. Laser trajectory and ablation volumes were computed both by manual tracing of mesiotemporal structures and by nonrigid registration of ablation cavities to a common reference system based on 7T MRI data. RESULTS >Of the 28 patients with at least 1-year follow-up, sparing of the mesial hippocampal head was significantly correlated with persistent disabling seizures (P = 0.01). Projecting all ablation cavities onto a common reference frame showed a clear tendency towards lateral placement of the laser with inadequate mesial hippocampal head ablation in these patients compared to those free of seizures. Patients that suffered deficits in memory, on the other hand, tended to have larger ablations with greater insult to entorrhinal and perirhinal cortex than those free of memory deficits. CONCLUSION Better understanding of the impact of ablation volume and location through the use of image normalization tools could potentially fine-tune this novel technique to improve seizure-freedom rates and associated neurocognitive deficits.

Patients' and procedural characteristics of AV-block during slow pathway modulation for AVNRT-single center 10 year experience

BackgroundPermanent AV-block is a recognized and feared complication of slow pathway modulation for AVNRT. We aimed to assess incidence of transient and permanent AV-block as well as consequences of transient AV-block in a large contemporary AVNRT ablation cohort. MethodsWe searched our single center prospective ablation database for occurrence of transient and permanent AV-block during slow pathway modulation between January 2004 and October 2015. We analyzed patients' and procedural characteristics as well as outcome of patients in whom transient or permanent AV-block occurred. ResultsOf 9170 patients who underwent a catheter ablation at our institution between January 2004 and October 2015, 2101 patients (64% women, mean age 50±18years) underwent slow pathway modulation. In three patients, permanent AV-block occurred during RF application. Additional two patients had transient AV-block that recovered (after a few minutes and 25min), but recurred within two days of the procedure. All five patients underwent dual chamber pacemaker implantation (0.2%). Transient AV-block related to RF delivery occurred in 44 patients (2%). Transient mechanical AV-block occurred in additional 17 patients (0.8%). In 12 patients, ablation was continued despite transient AV-block. One of these patients developed permanent AV-block. ConclusionPermanent AV-block following slow pathway modulation is a rare event, occurring in 0.2% of patients in a large contemporary single center cohort. Transient AV-block is more frequent (2%).

MP100-12 SHOULD PATHOLOGIC DIAGNOSIS BE OBTAINED PRIOR TO RENAL MASS ABLATION?

You have accessJournal of UrologyKidney Cancer: Ablative Therapy1 Apr 2017MP100-12 SHOULD PATHOLOGIC DIAGNOSIS BE OBTAINED PRIOR TO RENAL MASS ABLATION? Amy H. Lim, Shane Wells, Matthew Grimes, Tyler Wittmann, Sara Best, James Louis Hinshaw, Fred T. Lee, Meghan Lubner, Timothy Ziemiewicz, Stephen Y. Nakada, and E. Jason Abel Amy H. LimAmy H. Lim More articles by this author , Shane WellsShane Wells More articles by this author , Matthew GrimesMatthew Grimes More articles by this author , Tyler WittmannTyler Wittmann More articles by this author , Sara BestSara Best More articles by this author , James Louis HinshawJames Louis Hinshaw More articles by this author , Fred T. LeeFred T. Lee More articles by this author , Meghan LubnerMeghan Lubner More articles by this author , Timothy ZiemiewiczTimothy Ziemiewicz More articles by this author , Stephen Y. NakadaStephen Y. Nakada More articles by this author , and E. Jason AbelE. Jason Abel More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2017.02.3119AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Pathologic diagnosis of cancer in renal masses allows for optimal patient selection before treatment and appropriate follow-up after thermal ablation. However, biopsy is still often performed at the same time as ablation and pathologic findings are either non-diagnostic or benign in 7-45% of tumors in large ablation series. The objective of this study was to compare findings for renal mass biopsies obtained prior to treatment (priorbx) to biopsies obtained on the same day as ablation (samedaybx). METHODS An institutional database identified consecutive patients with renal masses treated with thermal ablation from 2001-2015. Patients treated without biopsy (37) were excluded. Radiologic tumor and patient data were reviewed. Fischer's exact or chi-square tests were used to evaluate differences between groups, non-diagnostic biopsy rate and the rate of ablation for benign tumors. RESULTS A total of 280 renal tumors were treated with ablation including 197 (70.4%) with priorbx and 83 (29.6%) with samedaybx. There was nodifference in patient or tumor characteristics between samedaybx and priorbx groups (table). Priorbx patients had longer skin-to-tumor distance median 10.5 vs. 8cm, p=0.0001. Non-diagnostic biopsy findings were significantly more common in patients with samedaybx compared to priorbx, 14.5% vs. 1.5%, p<0.001. Ablation of oncocytoma was also more common in patients with samedaybx compared to priorbx, 15.7% vs. 3.0%, p<0.001. RCC diagnosis was obtained in only 69.9% of tumors with samedaybx compared to 95.4% of tumors with priorbx, p<0.001. CONCLUSIONS Pre-ablation biopsy is associated with a decreased rate of treatment for benign and unidentified renal tumors and better diagnostic yield than same day renal biopsy. This approach has clear benefits to patients considering thermal ablation of small renal masses. © 2017FiguresReferencesRelatedDetails Volume 197Issue 4SApril 2017Page: e1334-e1335 Advertisement Copyright & Permissions© 2017MetricsAuthor Information Amy H. Lim More articles by this author Shane Wells More articles by this author Matthew Grimes More articles by this author Tyler Wittmann More articles by this author Sara Best More articles by this author James Louis Hinshaw More articles by this author Fred T. Lee More articles by this author Meghan Lubner More articles by this author Timothy Ziemiewicz More articles by this author Stephen Y. Nakada More articles by this author E. Jason Abel More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Microwave ablation of liver malignancies: comparison of effects and early outcomes of percutaneous and intraoperative approaches with different liver conditions : New advances in interventional oncology: state of the art.

Liver thermal ablation is an alternative treatment for hepatocellular carcinoma (HCC) and secondary liver malignancies. Microwave ablation (MWA) produces large ablation zones (AZ) in short time; however, AZ prediction is based on preclinical ex vivo models, rising concerns about reproducibility and safety in humans. We aimed to investigate the effects produced by a new-generation MWA system on human liver in vivo with different approaches (percutaneous or intraoperative) and liver conditions (cirrhosis or previous chemotherapy treatment), in comparison with manufacturer-provided predictions based on ex vivo animal models. Complete tumor ablation (CA) and early clinical outcomes were also assessed. From October 2014, 60 consecutive patients (cirrhotic=31; non-cirrhotic=10; chemotherapy-treated=19) with 81 liver nodules (HCC=31; mets=50) underwent MWA procedures (percutaneous=30; laparotomic=18; laparoscopic=12), with a 2450MHz/100W generator with Thermosphere™ Technology (Emprint™, Medtronic). A contrast-enhanced CT or MR was performed after one month to assess CA and measure AZ. A linear correlation between AZ volumes and ablation times was observed in vivo, without differences from manufacturer-provided ex vivo predictions in all operative approaches and liver conditions. Other independent variables (sex, age, nodule location) showed no relationship when added to the model. Median (IQR) longitudinal and transverse roundness-indexes of the AZs were, respectively, 0.77(0.13) and 0.93(0.11). CA at 1 month was 93% for percutaneous and 100% for intraoperative procedures (p=0.175). Thirty-day morbidity and mortality were 3% and 0%. MWA with Thermosphere™ Technology produces predictable AZs on human liver in vivo, according to manufacturer-provided ex vivo predictions. In our experience, this new-generation MWA system is effective and safe to treat liver malignancies in different operative and clinical settings.

Risk Factors of Liver Dysfunction Induced by Microwave Ablation in Patients with Hepatocellular Carcinoma

To investigate the risk factors of the aggravation of liver function induced by microwave ablation (MWA) of patients with hepatocellular carcinoma (HCC). We retrospectively reviewed the liver function of 498 patients with HCC undergoing MWA treatment. The dynamic changes of liver enzymes and Child-Pugh scores were observed. The potential risk factors, including the relative position between the tumor and portal vein (PV), tumor numbers, ablation volumes, Child-Pugh classifications, platelet, APRI and MELD scores, were analyzed. Based on the relative position between the tumor and PV, the tumors of the patients were divided into four groups, (1) far away from PV; (2) close to the third branch of PV (< 5mm); (3) close to the second branch of PV (< 5mm); (4) close to the first branch of PV (< 5mm). Complete response was achieved in 409 (98.08%) of 417 patients with tumors far away from the PV and in 89 (95.70%) of 93 patients with tumors close to a branch of the PV. Large fluctuations in the levels of ALB, ALT, AST and TBIL were observed three days after treatment, while the concentrations of ALP and γ-GGT were relative stable. 13.86% (69/498) patients suffered from liver function damage, that is, having an increase of Child-Pugh score by two three days after MWA. The incidences of liver dysfunction of the patients with tumors close to PV, more than three tumors, ablation volumes lager than or equal to 22.5 cm3, Child-Pugh classification B, APRI > 1.6, MELD > 30 or PLT < 110 × 109/L were 53.85%, 46.15%, 20.60%, 24.24%, 31.53%, 22.55% or 18.92%, respectively, much higher than those of patients without above characteristics. MWA can cause a transient deterioration of liver function. Patients with tumors close to PV, large numbers of tumors or large ablation volumes may present a great fluctuation of liver enzymes and an aggravation of liver dysfunction. In addition, poor liver reserve function is a risk factor of liver function damage but not the elevations of liver enzymes after MWA.

Abstract 13948: High Intraprocedural Atrial Fibrillation Termination Rate by Large Area Rotor Ablation Combined With Pulmonary Vein Isolation

Introduction: There remains contradictory data about the optimal ablation technique and the type of termination of atrial fibrillation (AF) ablation particularly in patient (pt) with persistent AF. The aim of this study was to determine the type of the termination of persistent AF during combined conventional and rotor ablation. Method: This is a single-center, prospective, observational study enrolled thirty-eight pts (24/63% male, mean age 63 years) with AF (mean left atrial size: 46,2 ± 7 mm), who underwent focal impulse and rotor modulation (FIRM) mapping and large area ablation around the core of the identified rotor(s), followed by conventional pulmonary vein isolation(PVI) using contact force catheter aiming 10-20 gr depending on the location. Two distinctive types of the AF termination were defined: sub-acute termination related to rotor elimination, furthermore acute termination due to PVI. Electric cardioversion (ECV) was executed only in the absence of spontaneous conversion to sinus rhythm (SR). Result: In 10(26%) pts acute AF termination after PVI was observed. In further 12 (31%) pts sub-acute termination of the AF could be observed after the identified rotor ablation. The combined technique of conventional and rotor ablation of pts with persistent AF resulted in 57,8% of termination rate. Spontaneous cardioversion could not be reached in 16 (42%) pts however 15 out of them were converted to SR by ECV. Procedural complication occurred in 3 pts presenting with groin hematoma, in one patient left atrial appendage (LAA) thrombus was revealed by transoesophageal echocardiography performed right after the ablation for guiding the planned LAA closure. Conclusion: Large area rotor ablation drag technique combined with contact force sensing technique results in a high termination rate of persistent AF. More studies are warranted to define the clinical significance and long term success rate of rotor ablation in pts with persistent atrial fibrillation.

Probabilistic finite element method for large tumor radiofrequency ablation simulation and planning

A challenging problem of radiofrequency ablation (RFA) in liver surgery is to accurately estimate the shapes and sizes of RFA lesions whose formation depends on intrinsic variations of the thermal–electrical properties of soft tissue. Large tumors, which can be as long as 10 cm or more, further complicate the problem. In this paper, a probabilistic bio-heating finite element (FE) model is proposed and developed to predict RFA lesions. Uncertainties of RFA lesions are caused by the probabilistic nature of five thermal–electrical liver properties: thermal conductivity, liver tissue density, specific heat, blood perfusion rate and electrical conductivity. Confidence levels of shapes and sizes of lesions are generated by the FE model incorporated with the mean-value first-order second-moment (MVFOSM) method. Based on the probabilistic FE method, a workflow of RFA planning is introduced to enable clinicians to preoperatively view the predicted RFA lesions in three-dimension (3D) within a hepatic environment. Accurate planning of the RFA needle placements can then be achieved based on the interactive simulation and confidence level selection.

Synthesis of Spherical ZnO Microcrystals by Laser Ablation in Air

SUMMARYWe have succeeded in synthesizing the zinc oxide (ZnO) microspheres by laser ablation of a ZnO sintered target in air, and have demonstrated ultraviolet whispering‐gallery‐mode lasting from the sphere under ultraviolet pulsed laser excitation. In this study, we investigated the dependence of the laser fluence and the spot size on the growth of the ZnO microspheres. Large sizes of more than 30 μm microspheres were synthesized with increasing the laser fluence up to 440 J/cm2. Although undesired nanoparticles and fragments were also generated at high fluence and large ablation spot size, selective collection of the microspheres can be expected because of different emitting distributions of the microspheres and other fragments.

Microwave ablation of primary and secondary liver tumours: ex vivo, in vivo, and clinical characterisation

Purpose: The aim of this study was to compare the performance of a microwave ablation (MWA) apparatus in preclinical and clinical settings.Materials and method: The same commercial 2.45 GHz MWA apparatus was used throughout this study. In total 108 ablations at powers ranging from 20 to 130 W and lasting from 3 to 30 min were obtained on ex vivo bovine liver; 28 ablations at 60 W, 80 W and 100 W lasting 5 and 10 min were then obtained in an in vivo swine model. Finally, 32 hepatocellular carcinomas (HCCs) and 19 liver metastases in 46 patients were treated percutaneously by administering 60 W for either 5 or 10 min. The treatment outcome was characterised in terms of maximum longitudinal and transversal axis of the induced ablation zone.Results: Ex vivo ablation volumes increased linearly with deposited energy (r2 = 0.97), with higher sphericity obtained at lower power for longer ablation times. Larger ablations were obtained on liver metastases compared to HCCs treated with 60 W for 10 min (p < 0.003), as ablation diameters were 4.1 ± 0.6 cm for metastases and 3.7 ± 0.3 cm for HCC, with an average sphericity index of 0.70 ± 0.04. The results on the in vivo swine model at 60 W were substantially smaller than the ex vivo and clinical results (either populations). No statistically significant difference was observed between ex vivo results at 60 W and HCC results (p > 0.08).Conclusions: For the selected MW ablation device, ex vivo data on bovine liver was more predictive of the actual clinical performance on liver malignancies than an in vivo porcine model. Equivalent MW treatments yielded a significantly different response for HCC and metastases at higher deposited energy, suggesting that outcomes are not only device-specific but must also be characterised on a tissue-by-tissue basis.

Comparative Effects of Irreversible Electroporation, Radiofrequency Ablation, and Partial Nephrectomy on Renal Function Preservation in a Porcine Solitary Kidney Model

To evaluate kidney function preservation or regeneration and pathological changes post-irreversible electroporation (IRE) in comparison with partial nephrectomy and radiofrequency ablation (RFA) in a solitary kidney porcine model. Tissue ablation using IRE has been reported to spare critical anatomic structures within or near the ablation zone with associated regeneration of adjacent parenchyma, possibly offering functional preservation. Fifteen pigs initially underwent laparoscopic nephrectomy. The lower third of the remaining kidney was then ablated or removed with either IRE, RFA, or partial nephrectomy. Serum creatinine (SCr) was measured at baseline, 24 hours, 3, 7, 14, and 28 days postoperatively. The impact of the type of procedure on SCr over time was evaluated. Acute and chronic histological changes were analyzed and cellular viability was assessed using nicotinamide adenine dinucleotide staining in the IRE ablations. Ten ablations (5 IRE, 5 RFA) and 5 partial nephrectomies of the entire lower third of a solitary kidney were performed. The type of procedure did not affect SCr significantly at baseline (P = .14) or change in SCr over time (P = .48). Histologically, IRE and RFA lesions showed similar findings including coagulative necrosis that progressively was replaced by reparative stromal changes and fibrous tissue. Nicotinamide adenine dinucleotide staining of the IRE lesions at 14 and 28 days showed no viability in the necrotic areas with viable tissue at the margins demonstrating reparative changes. Large volume IRE ablation of normal renal parenchyma in the porcine model does not provide a functional advantage as compared with conventional renal tumor treatments.

Percutaneous cryoablation of hepatic tumors: long-term experience of a large U.S. series.

To report our long-term experience with percutaneous cryotherapy for primary and metastatic liver tumors, including historical perspectives on complications over time and local recurrence rates. Following IRB approval under HIPAA compliance, 342 CT fluoroscopic-guided, percutaneous cryotherapy procedures were performed for 443 masses in 212 outpatients with hepatocellular carcinoma (HCC; N = 36), or metastatic disease (N = 176), grouped as colorectal carcinoma (CRC) and non-CRC metastases. Tumor and ablation sizes were noted in relation to adjacent vasculature. All complications were graded according to standardized criteria. Patients were followed by CT and/or MRI at 1, 3, 6, 12, 18, 24 months and yearly thereafter. Local recurrences were defined as either "procedural" within the ice ablation zone, or "satellite" within 1 cm of the ablation rim to evaluate recurrence patterns. Average tumor diameter of 2.8 cm was treated by average cryoprobe number of 4.5, which produced CT-visible ice ablation zone diameters averaging 5.2 cm. Grade >3 complications were primarily hematologic [N=20/342; (5.8%)], and appeared related to pre-procedural anemia/thrombocytopenia, carcinoid tumor type, and large ablation volumes. No significant central biliary leak, strictures, or bilomas were noted. At a mean follow-up of 1.8 years, local tumor recurrences were 5.5%, 11.1%, and 9.4% for HCC, CRC, and non-CRC metastases, respectively, consisting mainly of satellite foci. No significant difference was noted for local recurrences near major blood vessels or tumors >3 cm diameter. Percutaneous hepatic cryotherapy is a well-visualized, safe procedure that produces very low local recurrence rates, even for tumors near vasculature and diameters over 3 cm. Cryoablation deserves to be in the armamentarium of percutaneous hepatic ablation, especially with careful patient selection for tumors <4 cm and patients with platelet counts >100,000. Percutaneous hepatic cryoablation represents a highly flexible technique with particular benefits near central biliary structures and/or adjacent crucial structures.

Image-Guided High Intensity Focused Ultrasound System for Large Animal Nerve Ablation Studies.

High intensity focused ultrasound (HIFU) is a form of thermal ablation technique, which can treat a variety of medical afflictions. One promising therapeutic use is the permanent destruction of nerves non-invasively in patients with severe spasticity or certain types of pain (e.g., phantom limb pain). To this end, HIFU requires ultrasound guidance, which allows the non-invasive, target-specific deposition of thermal energy to the targeted nerve, thereby blocking axonal conduction. In this paper, a composite system comprising both ultrasound-imaging and HIFU therapy was developed and used to induce localized non-invasive nerve blockage in an in vivo large animal study. Five pigs were used with the femoral nerve as the target. Calibrated needle thermocouples inserted at the target site were employed to monitor the target tissue temperature. The degree of nerve blockage was assessed by measuring compound action potential (CAP) signal with a clinical nerve electrophysiology system before and after HIFU exposures. An average CAP signal amplitude reduction of 49% of baseline with a standard deviation of 9% was observed after 20–30 min post exposure. These results demonstrate the feasibility of the proposed ultrasound-guided HIFU modality as a potential non-invasive nerve ablation method.

Near-Infrared Light-Activatable Microneedle System for Treating Superficial Tumors by Combination of Chemotherapy and Photothermal Therapy.

Because of the aggressive and recurrent nature of cancers, repeated and multimodal treatments are often necessary. Traditional cancer therapies have a risk of serious toxicity and side effects. Hence, it is crucial to develop an alternative treatment modality that is minimally invasive, effectively treats cancers with low toxicity, and can be repeated as required. We developed a light-activatable microneedle (MN) system that can repeatedly and simultaneously provide photothermal therapy and chemotherapy to superficial tumors and exert synergistic anticancer effects. This system consists of embeddable polycaprolactone MNs containing a photosensitive nanomaterial (lanthanum hexaboride) and an anticancer drug (doxorubicin; DOX), and a dissolvable poly(vinyl alcohol)/polyvinylpyrrolidone supporting array patch. Because of this supporting array, the MNs can be completely inserted into the skin and embedded within the target tissue for locoregional cancer treatment. When exposed to near-infrared light, the embedded MN array uniformly heats the target tissue to induce a large thermal ablation area and then melts at 50 °C to release DOX in a broad area, thus destroying tumors. This light-activated heating and releasing behavior can be precisely controlled and switched on and off on demand for several cycles. We demonstrated that the MN-mediated synergistic therapy completely eradicated 4T1 tumors within 1 week after a single application of the MN and three cycles of laser treatment. No tumor recurrence and no significant body weight loss of mice were observed. Thus, the developed light-activatable MN with a unique embeddable feature offers an effective, user-friendly, and low-toxicity option for patients requiring long-term and multiple cancer treatments.

Design, characterization, and performance of a dual aperture, focused ultrasound system for microbubble-mediated, non-thermal ablation in rat brain

Submegahertz ultrasound (US) with microbubbles (µB) can ablate brain tissue: a low amplitude (< 1 MPa) alternative to thermal ablation. Single element transducers at transcranial frequencies have broad axial profiles compared to the size of targets in small animals. Thus, we sought a system to ablate millimeter volumes in normal and tumorous rat brain non-thermally using US and µB. The system consisted of two transducers oriented at 120°, driven at different frequencies (F = 837 kHz, ΔF = 30 Hz) to reduce the depth-of-field by 78%. To monitor cavitation, a passive detector (650 kHz) was confocally aligned with the therapy field. Targets were registered stereotactically. µB injections (100, 200, and 400 µl/kg) with 5-minute sonications proceeded at acoustic pressures relative to the in vivo cavitation threshold (0.3–0.6 MPa) determined a priori. Following MRI and sacrifice (1 h, 4 days, 10 days), tissue was fixed and stained. At 1 h, small lesions (<2 mm) were selectively comprised of stenotic capillaries with macrophage infiltration and neuronal damage. As lesions grew, stenotic capillaries within this escalating margin increased, along with neuronal damage. T2* lesions larger than 4 mm exhibited necrosis, cyst, and tissue removal histologically after four days. Persistent, strong (>5 dB) inharmonic energy indicated formation of large ablation volumes along the US path. Low level (<2 dB) or sporadic (<50%) cavitation indicated incomplete ablation. Results and mechanisms, especially with respect to ischemic stroke, will be discussed.

Two-Dimensional Phased Array Color-Flow Doppler Intracardiac Echo (2D-ICE) in Combination with the 2nd Generation 28 mm Cryoablation Balloon and 20mm Achieve Circular Mapping System (Arctic Front Advance, Medtronic, USA) for Ablation of Atrial Fibrillation: The ICE2 technique (ICE2T): A Retrospective Review of a Community Based Single Center Atrial Fibrillation Ablation Program

Introduction: One eighty five consecutive patients underwent large volume left atrial cryothermal AF ablation with the ICE2 technique (ICE2T). One forty two patients with a follow up of 12±6 months had outcome analysis, all 185 patients had procedural complications and fluoroscopic time analysis. Methods: Cryoablation was performed by direct ICE visualization of antral PV contact, entrance and exit PV block confirmed using Achieve and esophageal temperature monitoring. Additional ablation included left atrial appendage micro reentrant tachycardia and cavotricuspid isthmus performed using focal cryoablation (Freezor Max, Medtronic, USA). Results: The mean age was 62 years, 74.6% of the patients had long-term persistent atrial fibrillation with a mean duration of 4.49 years. Twenty seven patients had congestive heart failure with mean ejection fraction of 37%. Intraprocedural efficacy of PV isolation was 100%. The mean trough temperature was -51 degrees Celsius, lowest esophageal temperature was 9°C. Sinus rhythm was achieved in all patients intra-procedurally with mean heart rate increase of 15±3 bpm. Complications included 1 femoral pseudo aneurysm managed with outpatient thrombin injection and 1 esophageal erosion, spontaneously healed with PPIs (Outcomes). Conclusion: CE2T eliminates contact force sensing erraticism and need for complex mapping techniques, reducing complications and attaining durable PVI. The increase in mean heart rate suggests concomitant ablation of antral ganglionated plexi in conjunction with PV disconnection contributing to increased efficacy. Extrapolated data from CHF patients strongly suggests mortality benefits of rhythm control.