Multitined Expandable Electrodes Research Articles

Effective Management of Recurrent Trauma-Induced Neck Pain With Radiofrequency Neurotomy Using the Nimbus Electrosurgical Radiofrequency Multitined Expandable Electrode: A Case Report

BACKGROUND: Radiofrequency neurotomy (RFN) can be an effective treatment for patients with chronic neck pain and cervicogenic headaches resistant to conservative care. However, the degree and duration of pain relief after RFN is dependent upon the thoroughness of target nerve coagulation. CASE REPORT: This is a case of a 37-year-old patient with debilitating neck pain and headaches following a motor vehicle accident. Successful local anesthetic block of the third occipital nerve (TON) confirmed pain of C2-C3 facet joint origin. An initial RFN treatment of the TON, using standard 18G electrodes in bipolar mode, resulted in complete symptom amelioration for 8 months. Repeat RFN, using the same electrode configuration, was unsuccessful in alleviating the severe neck pain and headaches, and produced no demonstrable sensory loss in the distribution of the TON. RFN was then performed using the Nimbus® electrosurgical RF multitined expandable electrode, which provides a larger zone of coagulation in volume than standard RFN electrodes even when used in bipolar configuration. CONCLUSIONS: The Nimbus procedure resulted in successful coagulation of the TON with sensory loss in the TON distribution and reinstatement of palliative relief. KEY WORDS: Cervical pain, radiofrequency neurotomy, third occipital nerve, Nimbus, case report

Phase Contrast Imaging Based Microbubble Monitoring of Radiofrequency Ablation: An ex vivo Study.

BackgroundTo explore the potential of synchrotron radiation (SR) phase contrast imaging (PCI) for real-time microbubble formation monitoring during radiofrequency ablation (RFA).MethodsRFA was performed on ex vivo porcine muscle tissue using unipolar and multi-tined expandable electrodes. Images of microbubble formation in the samples were captured by both SR PCI and absorption contrast imaging. The synchronous ablation temperature was recorded. Each RFA electrode type group contained 6 samples. Ablation size was assessed by histologic examination.ResultsMicrobubble formation during RFA could be visualized by SR PCI. The diameter of the microbubbles revealed on the image ranged from tens of microns to several millimeters, and these microbubbles first appeared at the edge of the RFA electrode when the target region temperature reached approximately 60°C and rapidly extended outwards. The average microbubble range measured on PCI was 17.66 ± 0.74 mm. The average range of coagulation necrosis measured by histological examination was 17.22 ± 0.38 mm. There was no significant difference between them (P > 0.05). The range of microbubbles corresponded to the ablation zone.ConclusionPCI enabled real-time high-resolution visualization of microbubble formation during RFA, indicating a potential for its use in ablation monitoring.

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

To retrospectively evaluate the mid-term outcomes of percutaneous radiofrequency ablation (RFA) with multitined expandable electrodes externally cooled with saline solution in patients with T1a renal cell carcinoma (RCC). In this retrospective study, we evaluated 39 RCC in 35 patients treated with CT-guided RFA in 41 procedures (2011-2017). All patients were staged T1a, N0, M0 prior to RFA. Mean tumor size was 24.48mm. A 4-tined expandable RFA electrode cooled with pump-circulating saline was used. Efficacy was evaluated verifying complete tumor necrosis (no contrast enhancement on imaging) at the end of the procedure and on subsequent controls. Follow-up observation period was 5years. Minor/major complications, hospitalization days, serum creatinine and GFR pre- and post-RFA (compared using paired t test) and post-operative pain (evaluated with NRS after treatment) were considered as safety indicators. Overall survival was also calculated (Kaplan-Meier method). Of 35 patients, 30/35 had 1 treatment (primary effectiveness rate 86%), 4/35 had 2 treatments and 1/35 had 3 treatments for residual disease. There were no relapses and no mid-long-term complications; 3 minor (8%) and 1 major (2.7%) complications during perioperative period were reported. Mean before and after RFA serum creatinine rates were, respectively, 1.08mg/dl and 1.11mg/dl (p value: 0.4117). NRS median value is 0.8. Hospitalization days median value is [2.8 ± 1.9] days. 91.4% of all patients survived, with a median overall survival time of 65months. Mid-term results show that CT-guided RFA with multitined expandable electrodes externally cooled with saline solution is an effective and safe treatment in patients with RCC-staged T1aN0M0. Data reported in our study are in line with data reported in the literature from patients treated with other devices.

Percutaneous radiofrequency ablation for small hepatocellular carcinoma in hepatic dome under MR-guidance: clinical safety and efficacy

Purpose To evaluate the clinical safety and efficacy of percutaneous radiofrequency ablation (RFA) using multitined expandable electrodes under magnetic resonance imaging (MRI) guidance in the treatment of small hepatocellular carcinomas (HCCs) in the hepatic dome. Materials and methods The data of 49 patients with 50 HCC lesions in the hepatic dome who underwent MRI-guided RFA from April 2010 to January 2018 were retrospectively analyzed. Planning, targeting, and controlling were performed under MR-guidance during the procedure. The complications after RFA were observed. Follow-up MRI was performed to evaluate the curative effect. The local progression-free survival, recurrence-free survival, and overall survival rates were calculated using the Kaplan-Meier survival curve. Results The procedures were successfully accomplished in all patients without major complications. The mean follow-up time was 36.9 ± 25.8 months (range, 3–99 months). Technical success was 100% after one RFA session with MRI assessment after 1 month. Local tumor progression was observed in one patient (2%) with the lesion located in the hepatic dome at 4 months on a subsequent follow-up MRI. The progression-free survival time was 25.0 ± 22.7 months (median, 17.0 months). The 1-,3-, and 5-year local tumor progression-free survival rates were all 98.0%. The 1-,3-, and 5-year recurrence-free survival rates were 68.1%, 39.9%, and 28.5%, respectively, and the estimated overall survival rates were 93.7%, 76.3%, and 54.3%, respectively. Conclusion Planning, targeting, and controlling of RFA were well supported by MRI with acceptable time. MRI-guided RFA for small HCCs in the hepatic dome is safe and effective with fewer RF sessions.

CT-guided radiofrequency ablation of osteoid osteoma using a multi-tined expandable electrode system.

Radiofrequency ablation (RFA) is the gold standard for the treatment of symptomatic osteoid osteoma (OO) as RFA yields both a high success and low complication rate. It has been widely utilized over the years, but recurrences of OO after this treatment have been documented. These recurrences may be the result of various factors, including incomplete tumor ablation, and are significantly higher in lesions greater than 10 mm. Thus, the need to induce thermal ablation in a wider area led us to use a Multi-Tined Expandable Electrode System (MTEES). In this study we examined the efficacy and safety of RFA using a MTEES in symptomatic OO. Between January 2005 and June 2007, 16 patients with symptomatic OO were treated by CT-guided percutaneous RFA using a MTEES. The diameter of OO ranged from 6 to 15 mm (mean 10±2.6 mm). Patients were evaluated for clinical outcomes, complications and recurrence. Pain evaluation was assessed preoperatively, 2 weeks postoperatively and at last follow-up. Clinical follow-up was available for all patients at a mean of 84.3 months (range 73-96 months). Mean preoperative VAS score was 7.4 (range 5-9), two weeks after the procedure mean VAS score was 0.3 (range 0-1) with a mean change of -7.06 points (p<0.0001). At the last follow-up a complete relief from pain has been observed in all patients. No major and minor complications were observed nor recurrences. RFA using a MTEES has been effective, safe and reliable for the treatment of OOs. This system, by increasing the size of the necrosis, could be a viable alternative to the single needle electrode in lesions larger than 10 mm, reducing the risk of recurrence.

Computed tomographic-guided percutaneous radiofrequency ablation with hydrodissection of hepatic malignancies in the subcapsular location: Evaluation of safety and technical efficacy

BackgroundImage-guided percutaneous radiofrequency ablation (RFA) has been the most commonly used modality in the treatment of nonresectable hepatic malignancies. However, tumors in the subcapsular location are still technically challenging. This study was undertaken to evaluate the feasibility, safety, and efficacy of computed tomographic-guided percutaneous RFA with hydrodissection for hepatic malignancies in the subcapsular location. MethodsA total of 103 patients with 253 hepatic lesions were treated with computed tomographic-guided percutaneous RFA. Computed tomographic-guided percutaneous RFA with hydrodissection was performed in 15 patients with 15 hepatic nodules. All tumors located in the hepatic subcapsular location were considered difficult to treat on planning sonography. Hydrodissection was performed with 5% dextrose in water or saline solution in displacing adjacent structures ≥ 10 mm away from the liver capsule. Two RFA systems with multitined expandable electrodes or straight internally cooled single electrodes were used for treatment of hepatic malignancies. The feasibility, safety, and efficacy of this technique were analyzed on follow-up contrast-enhanced computed tomography or magnetic resonance imaging. ResultsHydrodissection was successfully achieved in 15 (100%) patients, displacing the adjacent structures ≥ 10 mm that were originally < 10 mm away from the liver capsule with administration of a mean of 376 mL of dextrose in water or saline solution. The average distance between an adjacent structure and the liver capsule after hydrodissection was 1.50 ± 0.40 cm and 0.11 ± 0.15 cm prior to hydrodissection, which was statistically significant (p < 0.001). No complication related to hydrodissection occurred during the follow-up period. The primary technical success rate of percutaneous RFA for tumor was 100% (15/15) at 1-month follow-up imaging. There were three minor complications (20%, 3/15) related to the RFA procedure. ConclusionComputed tomographic-guided percutaneous RFA with hydrodissection is a feasible, safe, and effective technique in the treatment of hepatic malignancies in the subcapsular location.

Radiofrequency Ablation of Lung Tumors Using a Multitined Expandable Electrode: Impact of the Electrode Array Diameter on Local Tumor Progression

PurposeTo retrospectively investigate the impact of the electrode array diameter on local tumor progression after lung radiofrequency ablation. Materials and MethodsThis study included 651 lung tumors treated using multitined expandable electrodes and followed for ≥ 6 months. The mean long-axis tumor diameter was 12 mm ± 7 (range, 2–42 mm). The difference between electrode array diameter and tumor diameter (DAT) was used to investigate the impact of the electrode array diameter. All tumors were classified into 2 groups according to various variables including DAT (≥ 10 mm or < 10 mm). The primary technique efficacy rates were calculated using Kaplan-Meier analysis and compared between the 2 groups of each variable using the log-rank test. In addition, crude and multivariate multilevel survival analyses were performed by sequentially including DAT and the other variables in 5 models. ResultsThe median DAT for 651 tumors was 12 mm (range, −15 to 24 mm). The technique efficacy rate was significantly lower in the < 10 mm DAT group than in the ≥ 10 mm group (P < .001). In the crude and multivariate multilevel survival analyses, < 10 mm DAT was a significant risk factor for local progression in all models except model 5 (P = .067). In the ≥ 10 mm group, the technique efficacy rates were not significantly different between the 2 ≥ 10 mm DAT subgroups (10 to <15 mm DAT vs ≥ 15 mm DAT). ConclusionsDAT is an important risk factor for local progression. We recommend an electrode that is ≥ 10 mm larger than the tumor diameter.

Radiofrequency ablation is a valid treatment option for lung metastases: experience in 566 patients with 1037 metastases

Minimal invasive methods are needed as an alternative to surgery for treatment of lung metastases. The prospective database of two cancer centers including all consecutive patients treated with radiofrequency ablation (RFA) for lung metastasis over 8 years was reviewed. RFA was carried out under general anesthesia, with computed tomography guidance using a 15-gauge multitined expandable electrodes RF needle. Five hundred sixty-six patients including 290 men (51%), 62.7 ± 13.2 years old with primary tumor to the colon (34%), rectum (18%), kidney (12%), soft tissue (9%) and miscellaneous (27%) received 642 RFA for 1037 lung metastases. Fifty-three percent of patients had 1 metastasis, 25% had 2, 14% had 3, 5% had 4 and 4% had 5-8. Metastases were unilateral (75%), or bilateral (25%). The median diameter [extremes] of metastases was 15 mm (4-70). Twenty-two percent of patients had extrapulmonary disease amenable to local therapy including 49 liver, 16 bone and 60 miscellaneous metastases. Median follow-up was 35.5 months. Median overall survival (OS) was 62 months. Four-year local efficacy was 89%. Four-year lung disease control rate was 44.1%, with patient retreated safely up to four times. Primary origin, disease-free interval, size and number of metastases were associated with OS in multivariate analysis. Progression at RFA site was associated with poor OS [P = 0.011, hazard ratio (HR): 1.69 (95% confidence interval 1.13-2.54)]. In the 293 colorectal cancer metastases, size >2 cm (HR = 2.10, P = 0.0027) and a number of metastases ≥3 (HR = 1.86, P = 0.011) remained significantly associated with OS. A prognostic score made of three groups based on the four above-mentioned prognostic factors demonstrated 3-year OS rates of respectively 82.2%, 69.5% and 53.6% (log-rank test, P ≤ 0.0001) among the three groups in the overall population, and of 81.3%, 72.8% and 57.9% (log-rank test, P = 0.005) in the colorectal cancer patients. Radiofrequency is an option for treatment of small size lung metastases, namely the ones below 2-3 cm.

Radiofrequency Ablation of Small Lung Metastases by a Single Application of a 2-cm Expandable Electrode: Determination of Favorable Responders

To determine which lung metastases are most likely to be treated effectively with a single radiofrequency (RF) application (defined as two separate applications of RF energy at a single electrode position) with a multitined expandable electrode with arrays 2 cm in diameter. The authors retrospectively evaluated 88 lung metastases (mean long-axis diameter, 0.9 cm) in 36 patients (20 men and 16 women; mean age, 57 years) treated with a single RF application with a multitined expandable electrode with arrays 2 cm in diameter. Based on follow-up computed tomographic examinations, the technique effectiveness rates were estimated with Kaplan-Meier analysis. Multiple variables were analyzed with the log-rank test to determine risk factors for local progression. Then, the technique effectiveness rates were again estimated when considering only metastases without risk factors and compared with those of other tumors. The median follow-up period was 13.2 months (range, 6.0-24.7 months). Tumor size greater than 1.0 cm (P = .033) and contact with the bronchus with an inner diameter of at least 2 mm (P = .047) were the significant risk factors for local progression. The technique effectiveness rates for metastases 1.0 cm or smaller that were not in contact with the bronchus (n = 59) were 96% at 1 year and at 2 years; those rates were significantly (P = .010) higher than those in other tumors (n = 29). A single RF application with a multitined expandable electrode with arrays 2 cm in diameter is most likely to suffice in small (<or=1 cm) lung metastases not in contact with a bronchus.

Large-volume multi-tined expandable RF ablation in pig livers: comparison of 2D and volumetric measurements of the ablation zone

To compare two-dimensional (2D) and three-dimensional (3D) computed tomography (CT) measurements of ablation zones (AZs) related to the shaft of two different large-volume monopolar multi-tined expandable electrodes. Percutaneous radiofrequency (RF) ablation was performed in 12 pigs (81.6 +/- 7.8 kg) using two electrodes (LeVeen 5 cm, Rita XL 5 cm; n = 6 in each group). Contrast-enhanced CT with the electrode shaft in place evaluated the AZ. The largest sphere centred on the electrode shaft within the AZ was calculated (1) based on the 2D axial CT image in the plane of the shaft assuming rotational symmetry of the AZ and (2) using prototype software and the 3D volume data of the AZ measured with CT. The mean largest diameter of a sphere centred on the electrode shaft was always smaller using the 3D data of the AZ than using 2D CT measurements assuming rotational symmetry of the AZ (3D vs 2D): LeVeen 18.2 +/- 4.8 mm; 24.5 +/- 3.1 mm; p = 0.001; Rita XL 20.0 +/- 3.7 mm; 28.8 +/- 4.9 mm; p = 0.0002. All AZ showed indentations around the tines. Two-dimensional CT measurements assuming rotational symmetry of the AZ overestimate the largest ablated sphere centred on the electrode shaft compared with 3D CT measurements.

Aspergilloma in a Cavity Formed after Percutaneous Radiofrequency Ablation for Lung Cancer

Aspergilloma in a Cavity Formed after Percutaneous Radiofrequency Ablation for Lung Cancer

Infusion of hypertonic saline into the lung parenchyma during radiofrequency ablation of the lungs with multitined expandable electrodes: results using a porcine model.

The present study was performed to clarify the effect of hypertonic saline infusion into the lung parenchyma on radiofrequency ablation (RFA) of the lungs. A total of 20 ablation zones were created in 3 pigs. The ablation zones were divided into 3 groups. Group 1 (n=6) consisted of ablation zones created by applying smaller radiofrequency (RF) power without saline infusion; group 2 (n=5) zones were created by applying greater RF power without saline infusion;and group 3 (n=9) zones were created by applying greater RF power with saline infusion. The techniques of saline infusion included administration of hypertonic saline 1 ml before RFA, followed by continuous administration at a rate of 1 ml/min during the first 2 min after the initiation of RFA. The ablation parameters and coagulation necrosis volumes were compared among the groups. Group 3 had a tendency toward smaller mean impedance than group 1 (p=0.059) and group 2 (p=0.053). Group 3 showed significantly longer RF application time than group 2 (p=0.004) and significantly greater maximum RF power than group 1 (p=0.001) and group 2 (p=0.004). Group 3 showed significantly larger coagulation necrosis volume (mean, 1,421mm3) than group 2 (mean, 858 mm3, p=0.039) and had a tendency toward larger necrosis volume than group 1 (mean, 878 mm3, p=0.077). Although this small study had limited statistical power, hypertonic saline infusion during RFA appeared to enlarge coagulation necrosis of the lung parenchyma.

Does tumor type affect local control by radiofrequency ablation in the lungs?

Objective : To retrospectively evaluate the effect of tumor type on local control by radiofrequency ablation in the lungs. Materials and methods : This study included 252 lung tumors (mean size, 13.5 mm) in 105 patients (73 men and 32 women; mean age, 66.6 years) who underwent radiofrequency ablation with a multitined expandable electrode. Those tumors comprised five tumor types: primary lung cancer ( n = 35) and pulmonary metastases from colorectal cancer ( n = 117), lung cancer ( n = 23), renal cell carcinoma ( n = 49), and hepatocellular carcinoma ( n = 28). Local control was evaluated with contrast-enhanced computed tomography. The overall local control rates were estimated as well as those for each tumor type using the Kaplan-Meier analysis. Local control rates for a given tumor type were compared with those for the four other types. Then, multivariate multilevel analysis was performed using the variables of tumor type, tumor size, contact with a vessel or bronchus, and procedure period. Results : The overall local control rates were 97%, 86%, 81%, and 76% at 6, 12, 18, and 24 months, respectively. Local control rates varied among the tumor types, and metastatic colorectal cancer showed significantly ( P = .023) higher local control rates than those of the four other types. However, multivariate analysis indicated that the relative risk of local progression for a given tumor type was comparable to the risks for the four other types. Conclusion : Tumor type per se did not significantly influence local control.

Effects of variation in perfusion rates and of perfusion models in computational models of radio frequency tumor ablation

Finite element method (FEM) models are commonly used to simulate radio frequency (RF) tumor ablation. Prior FEM models of RF ablation have either ignored the temperature dependent effect of microvascular perfusion, or implemented the effect using simplified algorithms to reduce computational complexity. In this FEM modeling study, the authors compared the effect of different microvascular perfusion algorithms on ablation zone dimensions with two commercial RF electrodes in hepatic tissue. They also examine the effect of tissue type and inter-patient variation of perfusion on ablation zone dimensions. The authors created FEM models of an internally cooled and multi-tined expandable electrode. RF voltage was applied to both electrodes (for 12 or 15 min, respectively) such that the maximum temperature in the model was 105 degrees C. Temperature dependent microvascular perfusion was implemented using three previously reported methodologies: cessation above 60 degrees C, a standard first-order Arrhenius model with decreasing perfusion with increasing degree of vascular stasis, and an Arrhenius model that included the effects of increasing perfusion at the ablation zone boundary due to hyperemia. To examine the effects of interpatient variation, simulations were performed with base line and +/-1 standard deviation values of perfusion. The base line perfusion was also varied to simulate the difference between normal and cirrhotic liver tissue. The ablation zone volumes with the cessation above 60 degrees C perfusion algorithm and with the more complex Arrhenius model were up to 70% and 25% smaller, respectively, compared to the standard Arrhenius model. Ablation zone volumes were up to 175% and approximately 100% different between the simulations where -1 and +1 standard deviation values of perfusion were used in normal and cirrhotic liver tissue, respectively. The choice of microvascular perfusion algorithm has significant effects on final ablation zone dimensions in FEM models of RF ablation. The authors also found that both interpatient variation in base line tissue perfusion and the reduction in perfusion due to cirrhosis have considerable effect on ablation zone dimensions.

Radiofrequency hepatic ablation with internally cooled electrodes and hybrid applicators with distant saline infusion using an in vivo porcine model

Aims Radiofrequency ablation (RFA) of tumors by means of internally cooled (ICE) or multitined expandable electrodes combined with infusion of saline into the tissue may improve results. Our aim was to determine the efficacy of a previously optimized hybrid ICE system (ICE combined with infusion of saline into the tissue at a distance of 2 mm) in comparison with a conventional ICE cluster electrode in porcine liver in vivo. Methods A total of 32 RFA were performed on a total of 10 farm pigs using two RFA systems: Group A ( n = 16): Cluster electrode. Group B ( n = 16): Hybrid system (with continuous infusion of 100 ml/h of 20% NaCl at 2 mm distance from the electrode shaft by an independent isolated needle). Livers were removed for macroscopic and histological assessment after the procedure. Coagulation volume, coagulation diameters, coefficient of variability (CV) of coagulation volume, sphericity ratio (SR), deposited power (DP), deposited energy (DE), deposited energy per coagulation volume (DEV) and rise of animal temperature during the procedure were compared and correlated among groups. Additionally, linear regression analysis was modeled to study the relationship between deposited energy and either coagulation volume and rise of animal temperature during the procedure in both groups. Results Both coagulation volume and short diameter of coagulation were significantly greater ( p < 0.05) in group B compared to group A (22.7 ± 11.0 cm 3 and 3.1 ± 0.7 cm vs. 13.5 ± 7.7 cm 3 and 2.5 ± 0.5 cm, respectively). A similar CV and SR was observed among groups (57.1% and 1.4 ± 0.3 vs. 48.6% and 1.3 ± 0.2 for groups B and A, respectively). In group B, DE and DP were more than double group A, but DEV was nearly twice as high (9782 J/cm 3 vs. 5342 J/cm 3, for groups B and A, respectively). No significant relationship between DE and coagulation volume was encountered. Conclusion Efficacy of a single ICE may be improved with continuous infusion of saline at around 2 mm from the electrode shaft. Coagulation volume obtained with this improved system may be even greater than that obtained with a cluster electrode.

Influence of Surgical Staples on Radiofrequency Ablation Using Multitined Expandable Electrodes

During radiofrequency ablation (RFA), there is a risk that the multitined expandable electrode will come into contact with one of the surgical staples used to treat local recurrence after surgical operations. Our objective was to evaluate whether a surgical staple would influence the RFA of egg white using a multitined expandable electrode. Multitined expandable electrodes, LeVeen needles (expandable diameter 3.0 cm), were sunk into an egg white bath with (a) no surgical staple, (b) a surgical staple touching one of the tines, or (c) a surgical staple touching two of the tines simultaneously. By connecting the LeVeen needle and copper plate at the bottom of the bath, RFA was then performed on the egg whites as a substitute for human tissue. Ten egg white baths were ablated under each of conditions (a), (b), and (c), for a total of 30 sets of coagulated egg white. There was no significant difference in the time from the power-on to the roll-off (i.e., the completion and shutting off of the electric circuit) or in the maximum diameter of the thermal lesion between conditions (a) and (b) or (a) and (c). However, the minimum diameter of the thermal lesion was significantly smaller in (c) compared with (a) (p < 0.01). Surgical staples have the capacity to interfere with the electromagnetic field and decrease the minimum diameter of the thermal lesion in the event that a staple touches two of the tines of a multitined expandable electrode during RFA. Although the difference might be small enough to be neglected under many clinical circumstances, we recommend that, if possible, the tines not be expanded near metallic material.

Risk factors for local progression after percutaneous radiofrequency ablation of lung tumors

The purpose of the study was to retrospectively evaluate the risk factors for local progression after percutaneous radiofrequency (RF) ablation of lung tumors. The study included 128 patients (77 men, 51 women; mean age, 61.3 years) with 342 tumors (25 primary and 317 metastatic lung neoplasms; mean long-axis diameter, 1.7 cm) treated with RF ablation. The overall primary and secondary technique effectiveness rates were estimated using Kaplan-Meier analysis. Multiple variables were analyzed using the log-rank test, followed by multivariate multilevel analysis to determine independent risk factors for local progression. The primary and secondary technique effectiveness rates were again estimated when considering only tumors without independent risk factors. The median follow-up period was 12 months (range, 6-47 months). The overall primary and secondary technique effectiveness rates were 72% and 84% at 1 year, 60% and 71% at 2 years, and 58% and 66% at 3 years, respectively. Larger tumor size (hazard ratio [HR], 1.97; 95% confidence interval [95% CI], 1.47-2.65; P < .00001) and the use of an internally cooled electrode (HR, 2.32; 95% CI, 1.10-4.90; P = .027) were assessed as independent risk factors for local progression. The primary and secondary technique effectiveness rates when considering tumors smaller than 2 cm and treated with a multitined expandable electrode were 89% and 89% at 1 year and 66% and 78% at 2 years, respectively. Larger tumor size and the use of an internally cooled electrode were independent risk factors for local progression after RF ablation of lung tumors.

Radiofrequency ablation of chondroblastoma using a multi-tined expandable electrode system: initial results

The standard treatment for chondroblastoma is surgery, which can be difficult and disabling due to its apo- or epiphyseal location. Radiofrequency (RF) ablation potentially offers a minimally invasive alternative. The often large size of chondroblastomas can make treatment with plain electrode systems difficult or impossible. This article describes the preliminary experience of RF treatment of chondroblastomas with a multi-tined expandable RF electrode system. Four cases of CT-guided RF treatment are described.

Radiofrequency ablation in pig lungs:in vivocomparison of internally cooled, perfusion and multitined expandable electrodes

The purpose of this study was to compare the amounts of in vivo coagulation obtained by radiofrequency (RF) ablation in porcine lung, using three types of electrodes. 15 in vivo ablation procedures were performed in the lungs of five pigs using three kinds of currently available RF devices under CT guidance. After placing an electrode in the lung, three ablation zones were created at each of three different regimens: Group A: RF ablation with an internally cooled electrode; Group B: RF ablation with a perfusion electrode, with instillation of 0.9% NaCl solution at a rate of 1.5 ml min(-1); Group C: RF ablation with a multitined expandable electrode. According to the manufacturer's recommendations, RF application times were 12 min in group A and 20 min in group B. In group C, RF energy was delivered for 7 min after a mean temperature of 110 degrees C was reached at 5 cm deployment. 36 min after the procedures, contrast-enhanced CT scans were obtained to evaluate the volume of zone of coagulation, and lungs were harvested for gross measurements. After macroscopic and histopathological analyses of 5 mm-thick lung sections, diameters, volumes and variation coefficients of regions of central coagulation were assessed. During RF ablation, the perfusion electrode allowed a larger energy delivery than the internally cooled or the multitined expandable electrodes, i.e. 33.6+/-4.7 kJ in group A, 40.0+/-8.2 kJ in group B and 23.5+/-6.1 kJ in group C (p<0.05). On gross observation, the cut surface of the gross specimen containing RF-induced coagulation showed that the ablated tissue appeared to be a central, firm, dark-brown area surrounded by an irregular outer margin (approximately 3-10 mm thick) of bright red tissue. In vivo studies showed that RF ablation using the perfusion electrode achieved larger coagulation volume than RF ablation using the other electrodes (p<0.05): 7.2+/-4.1 cm3 in group A; 16.9+/-5.5 cm3 in group B; 7.5+/-3.3 cm3 in group C. The corresponding variation coefficients were 0.55, 0.31, and 0.45, respectively. Our study shows that RF ablation using a perfusion electrode achieves a larger coagulation volume with an irregular margin than RF ablation using internally cooled or multitined expandable electrodes in the porcine lung.

Experimental Radiofrequency Ablation Near the Portal and the Hepatic Veins in Pigs: Differences in Efficacy of a Monopolar Ablation System

We sought to compare the efficacy of a monopolar radiofrequency ablation system in vivo near the portal vein and the hepatic veins in porcine liver. Radiofrequency ablation of healthy livers near the portal vein and the hepatic veins was performed in 10 pigs with a multitined expandable electrode. Volumes and diameters of zones of ablation were assessed by magnetic resonance imaging. Volumes (16.0 +/- 5.5 mL, P = 0.001) and diameters (4.0 +/- 0.7 cm, 3.3 +/- 0.7 cm, 3.0 +/- 0.6 cm, P <or= 0.05) of the zones of ablation near the hepatic veins were larger than that near the portal vein (7.5 +/- 4.1 mL, 3.2 +/- 0.7 cm, 2.6 +/- 0.7 cm, 2.4 +/- 0.6 cm). Energy deposition needed to ablate liver tissue was higher (P = 0.003) for radiofrequency ablation near the portal vein (3.16 +/- 1.58 kJ/mL) than for radiofrequency ablation near the hepatic veins (1.65 +/- 1.14 kJ/mL). Higher energy deposition is needed to ablate liver tissue near the portal vein than near the hepatic veins. As a result, the zone of ablation is larger near the hepatic vein than near the portal vein.