Percutaneous radiofrequency ablation of lung tumors in a large animal model

PURPOSE: Percutaneous radiofrequency ablation (RFA) is accepted therapy for liver tumors in the appropriate clinical setting, but its use in lung neoplasms remains investigational. We undertook this study to evaluate the feasibility and immediate effectiveness of RFA for treatment of both solitary pulmonary nodules and clusters of lung tumors in a large animal model. MATERIALS AND METHODS: Percutaneous RFA of 14 lung tumors in five dogs was performed under CT guidance. Animals were euthanatized 8-48 hours after the procedure. The lungs and adjacent structures were harvested for gross and histopathologic evaluation. RESULTS: Five solitary pulmonary nodules (range, 17-26 mm) and three clusters of three nodules each (range, 7-17 mm per nodule) were treated with RFA. All ablations were technically successful. Perilesional ground-glass opacity and small asymptomatic pneumothoraces (n = 4) were visualized during the RFA sessions. One dog developed a large pneumothorax treated with tube thoracostomy but was euthanatized 8 hours post-RFA for persistent pneumothorax and continued breathing difficulty. Follow-up CT 48 hours post-RFA revealed opacification of the whole lung segment. Gross and histopathologic evaluation showed complete thermal coagulation necrosis of all treated lesions without evidence of any viable tumor. The region of thermal coagulation necrosis typically extended to the lung surface. Small regions of pulmonary hemorrhage and congestion often surrounded the areas of coagulation necrosis. CONCLUSIONS: RFA can be used to treat both solitary pulmonary nodules and clusters of tumor nodules in the canine lung tumor model. This model may be useful for development of specific RFA protocols for human lung tumors.     

Assessment of cerebral microembolism during percutaneous radiofrequency ablation of lung tumors using diffusion-weighted imaging

OBJECTIVE: It is well known that radiofrequency ablation generates microbubbles in the liver. We hypothesized that microbubbles generated during percutaneous radiofrequency ablation of lung tumors flow into the pulmonary veins and are distributed to the systemic arteries, as with radiofrequency ablation of liver tumors. To assess the risk of cerebral infarction during radiofrequency ablation of lung tumors, we performed diffusion-weighted imaging and, if possible, monitored microemboli in the carotid artery during radiofrequency ablation. SUBJECTS AND METHODS: We prospectively studied 20 patients (19 men and one woman) who underwent radiofrequency ablation of lung tumors. Pre- and postoperative MRI examinations were performed in all 20 patients, and during 17 radiofrequency ablation sessions, sonography was used to monitor whether microemboli were generated. RESULTS: Radiofrequency ablation was technically feasible for the treatment of selected pulmonary tumors. Microemboli, which were believed to represent microbubbles, were seen on sonography during three of the 17 radiofrequency ablation sessions. They were rarely observed when a lung tumor was small, the treatment session was brief, and the radiofrequency emission power was low. No new area of abnormal intensity was seen on postoperative MRI in all 20 patients. Although the microemboli were observed, MRI could not confirm infarction. CONCLUSION: We concluded that cerebral infarction as a result of microbubbles generated during radiofrequency ablation of lung tumors has a low possibility of becoming a clinical problem.     

Improved coagulation with saline solution pretreatment during radiofrequency tumor ablation in a canine model

PURPOSE: To determine whether pretreatment with local NaCl injection can increase radiofrequency (RF)-induced coagulation in a large animal model. MATERIAL AND METHODS: Multiple canine venereal sarcomas (n = 25) were implanted subcutaneously in eight mildly immunosuppressed dogs (25 mg/kg cyclosporin A twice daily). Tumors were incubated for 8-12 weeks to a diameter of 4.2-6.3 cm (5.1 cm +/- 0.7). Internally cooled RF ablation (1-cm tip; 12 min; pulsed technique; 2,000-mA maximum) was performed. Tumors were pretreated with 6 mL of 18%, 24%, or 36% NaCl injected intratumorally under direct ultrasound guidance after RF electrode insertion, and this treatment was compared to RF treatment without NaCl injection and to 36% NaCl injection without RF ablation. Impedance measurements and remote thermometry were performed. These measurements and resultant coagulation were compared. RESULTS: Significantly greater RF heating (73 degrees C +/- 11 degrees C at 20 mm) was observed when the tumors were treated with 24% or 36% NaCl pretreatment, compared to the 47 degrees C +/- 5 degrees C observed when 18% or no NaCl was injected (P <.02). In the 36% NaCl group, the entire tumor (5.2 cm +/- 0.8 diameter) was completely ablated in every case, with coagulation extending several centimeters into the surrounding tissues. By comparison, control tumors (without NaCl injection) contained coagulation measuring 3.1 cm +/- 0.2, surrounded by viable, well-perfused tumor (P <.01), and 36% NaCl alone produced 2.7 cm +/- 0.6 of patchy necrosis. CONCLUSIONS: Pretreatment with intratumoral injection of small volumes of highly concentrated NaCl markedly increases RF heating and coagulation in a large animal tumor model. The complete destruction of tumors 5 cm in diameter or larger suggests that this substantial increase may be achieved for tumor ablation in clinical practice.     

Chest wall temperature during radiofrequency ablation in a normal rabbit lung model

Purpose  

The aim of this study was to examine the actual temperature during lung radiofrequency ablation (RFA) and pathological changes due to thermal damage in the pleural tissue of the chest wall in a rabbit model.     

CT导向下射频消融治疗不能手术切除肺癌患者的临床分析

目的:探讨CT导向下射频消融对不能手术切除肺癌治疗的有效性及安全性。方法:回顾性分析23例经CT导向下射频消融治疗的肺癌患者,其中原发性肺癌患者17例,肺癌术后转移6例,评价其治疗局部有效率和1年无进展生存期。结果:本组共23例患者共行33次射频消融治疗,手术均顺利完成。平均随访时间18.3月(13～30个月),局部控制率在3月、6月及1年分别是96.8%、93.5%及86.7%,1年无进展生存率73.9%。余发生与手术相关的严重并发症。结论:CT导向下射频消融在肺癌治疗中是一种安全有效的局部治疗方法。     

Cerebral microembolization during radiofrequency ablation of lung malignancies

Three patients underwent radiofrequency (RF) ablation for treatment of malignant lung tumors. During three of the four RF ablation sessions, duplex ultrasound was used to intermittently sample the carotid arteries for the presence of emboli; microemboli were detected in all three patients. Embolization occurred within 1 minute of "roll-off." The rate of embolization ranged from 2 to 50 per minute. No new neurologic defects were found on examination. No cognitive, memory, or behavioral changes were noted by any of the three patients or their spouses. Microemboli to the cerebral circulation occurred during RF ablation of lung tumors. The clinical significance of these emboli is unknown.     

Percutaneous radiofrequency ablation of lung tumors with expandable needle electrodes: current status

Percutaneous radiofrequency thermal ablation (RFA) has been used to treat primary and secondary liver tumors under ultrasound, computed tomography (CT), or magnetic resonance imaging (MRI) guidance for the past decade [Park et al., Radiol Clin North Am 38:545–561, 2000; Siperstein and Gotomirski, Cancer J 6:S293–S301, 2000; Kelekis et al., Eur Radiol 13:1100–1105, 2003]. RFA is a low-cost, minimally invasive treatment that has recently attracted attention for treating tumors in different solid organs with promising results [Dupuy and Goldberg, J Vasc Interv Radiol 12:1135–1148, 2001; Friedman et al., Cardiovasc Intervent Radiol 27:427–434, 2004]. It can be provided with minimal hospitalization, and experienced practitioners have reported low complication rates [Dupuy and Goldberg, J Vasc Interv Radiol 12:1135–1148, 2001; Livraghi et al., Radiology 226:441–451, 2003]. Patients with lung malignancies (primary lung cancer or pulmonary metastases), who cannot be operated, might be candidates for RFA treatment. It can also be used in association with other treatments (i.e., chemotherapy, radiotherapy) for better disease control. Combination of the above with RFA may help reduce morbidity and mortality. Many ways to apply energy to the tumor exist (monopolar and bipolar RFA, microwave, laser, brachytherapy). In this review we will focus on expandable monopolar systems, which despite their deficiencies are the most popular in the interventional radiology sector.     

Percutaneous radiofrequency (RF) thermal ablation of rabbit tumors embedded in fat: a model for RF ablation of breast tumors

RATIONALE AND OBJECTIVES: To develop an experimental tumor model for RF ablation of breast tumors surrounded by fat and to investigate the minimally invasive treatment of such tumors by saline-enhanced RF ablation monitored by ultrasound (US). METHODS: Twenty-eight VX2 tumors were implanted into the retroperitoneum of 14 rabbits and monitored by B-mode US at regular intervals of 2 to 3 days. Saline-enhanced RF ablation (25-mm tip length) was performed 16 days after tumor implantation (10-minute treatment time, 28 W, 15 mL/h infusion of 0.9% NaCl, which was increased to 30 mL/h in cases of an impedance increase). Thermal lesion growth was monitored by B-mode US. Treatment was considered complete if no relapse was detectable histopathologically after a follow-up period of up to 3 weeks. RESULTS: All tumor implantations were successful, reaching sizes from 5 to 38 mm 16 days after implantation. Tumors >20 mm showed central necrosis on US. Smaller tumors without signs of necrosis required greater needle perfusion to maintain constant needle-to-tissue impedance. Local relapses occurred in 14 of 27 tumors (51.8%), all with tumors >20 mm. In 12 cases, they were already detected sonographically. In 2 cases, "islands" of vital tumor were detected only during histopathological assessment. CONCLUSIONS: VX2 tumors are implantable into hypovascular adipose tissue with a high success rate and may be used as a model for RF ablation of breast tumors. B-mode US is not suitable for guiding RF ablation of tumors embedded in fat. The method appears to be more successful with smaller tumors.     

肺肿瘤CT引导下经皮射频消融后的影像评估进展

近年来,CT引导下经皮射频消融术在无法手术切除或转移性肺肿瘤的治疗中备受推崇。但因术后病理改变的复杂性,不同影像检查的表现既存在重叠,又存有差异,使得评估充满挑战。就不同影像方法(CT、PET/CT、MRI)对肺肿瘤病人术后不同时期的评估进展予以综述,以期更好地指导临床。     

Percutaneous radiofrequency thermal ablation of lung VX2 tumors in a rabbit model using a cooled tip-electrode: feasibility,safety, and effectiveness

RATIONALE AND OBJECTIVE: To evaluate the feasibility, safety, and effectiveness of percutaneous CT-guided transthoracic radiofrequency ablation (RFA) of lung VX2 tumors implanted in rabbits. MATERIALS AND METHODS: Thirty-five rabbits with implanted lung VX2 tumors were divided into two groups, an RFA group (n = 28) and a control group (n = 7). In the RFA group, RFA was performed on VX2 tumors using a 17-gauge internally cooled-tip electrode. Contrast-enhanced CT was performed before the RFA and on the same day, day 3, weeks 1, 2, 3, and months 1, 2, 6, and 9, after the RFA. The therapeutic efficacy was evaluated by CT and pathologic findings. RESULTS: RFA of lung tumors was technically successful in each instance. Complete tumor ablation was achieved in 19 of the 28 rabbits (67.9%) in the RFA group. Nine rabbits (32.1%) showed local tumor relapse and mediastinal lymph nodal or pleural metastasis. The animals in the control group died of end-stage malignancies with diffuse tumor spread and malignant pleural effusion (mean 26 +/- 2.7 days). There were 17 (60.7%) complications related to the procedure, ie, pneumothorax (n = 12), obstructive pneumonia (n = 3), hemothorax (n = 1), and burn (n = 1). RFA of centrally located VX2 tumors (in inner 2/3 of the lung) was more frequently associated with complications than RFA of peripherally located VX2 tumors ( P= 0.02). CONCLUSION: This experimental study demonstrates the feasibility of RFA therapy for treating lung VX2 tumors in rabbits, although RFA for central tumors carries the potential for major complications, including large pneumothorax or obstructive pneumonia.     

MRI-guided radiofrequency thermal ablation of normal lung tissue: in vivo study in a rabbit model

OBJECTIVE: The purpose of this study was to assess the feasibility of MRI to guide and monitor radiofrequency ablation of normal pulmonary tissue in a rabbit model. MATERIALS AND METHODS: Percutaneous puncture and lung radiofrequency ablation were performed in six New Zealand white rabbits under MRI control using a 0.2-T open MRI scanner. Technical feasibility and complication detection were evaluated. The ablation zone appearance and size were assessed using MRI, CT, and gross pathology. Interclass correlation coefficients (ICCs) of the maximum short-axis diameters of the lesions on gross pathology and the corresponding diameters as measured on each MRI pulse sequence and on CT scans were calculated. RESULTS: MRI guidance of percutaneous puncture and radiofrequency ablation of pulmonary tissue is feasible. A pneumothorax was detected and treated using MRI. In the specimen, the mean coagulation necrosis diameter was 9.8 mm. The T1-weighted spoiled gradient-echo fast low-angle shot images showed the highest ICC (0.81) for the thermal lesion diameter. CONCLUSION: Our results indicate that MRI guidance is feasible and useful for radiofrequency ablation of normal pulmonary tissue.     

In vitro blood-perfused bovine liver model: a physiologic model for evaluation of the performance of radiofrequency ablation devices

Purpose

To describe an in vitro blood-perfused bovine liver model for the testing of radiofrequency (RF) ablation devices and compare the performance of a specific RF ablation device in the model relative to three other biologic models.

Materials and Methods

Fresh bovine livers were used to create three in vitro models: blood-perfused, Krebs–Henseleit (KH) solution–perfused, and nonperfused. The perfused models were connected to a heart–lung machine via the portal vein and perfused with heparinized autologous blood or KH solution under physiologic conditions. Six swine were used as in vivo liver models. A cluster electrode and RF ablation system was operated in impedance mode for 12 minutes in all models. Ablated livers were sectioned, with long- and short-axis measurements of the ablations obtained, and statistical analysis was performed.

Results

A total of 39, 23, 17, and 12 ablations were performed in 14, 6, 5, and 6 blood-perfused bovine livers, KH solution–perfused bovine livers, nonperfused bovine livers, and in vivo porcine livers, respectively. On cut specimens, the average diameters of ablation zones were 4.00 cm (95% CI, 3.88–4.13) in blood-perfused livers, 4.34 cm (95% CI, 4.14–4.50) in KH solution–perfused livers, 4.67 cm (95% CI, 4.50–4.83) in nonperfused livers, and 3.56 cm (95% CI, 3.26–3.83) in in vivo porcine livers. In all models, the ablation zone diameters were normally distributed.

Conclusions

In the in vitro blood-perfused bovine liver model, the size of ablations produced by an RF ablation device are closer in size to those seen in porcine liver in vivo compared with the lesions produced in KH solution–perfused or nonperfused bovine liver.     

肺癌射频消融治疗进展

近年来射频消融技术治疗肺癌在临床上正得到日趋广泛的应用,取得了较大进展,具有操作方便,并发症轻,患者痛苦少等特点.本文对其基础研究、临床应用、并发症及其处理等方面进行综述.     

Percutaneous radiofrequency ablation of a lung metastasis: delayed cavitation with no infection

A 64-year-old man presented with a lung metastasis of the lower left lobe. After partial response with chemotherapy, a thoracotomy was performed that did not allow a wedge resection, and lobectomy was contraindicated by the patient's ventilatory function. Radiofrequency ablation of this lung metastasis was thus performed, followed by a delayed cavitation with no infection, which, to our knowledge, has not yet been described.     

Percutaneous radiofrequency ablation for patients with malignant lung tumors: a phase II prospective multicenter study (JIVROSG-0702)

Purpose

This prospective multicenter study aimed to evaluate the efficacy and safety of percutaneous radiofrequency (RF) ablation for lung cancer.

Materials and methods

From May 2008 to April 2012, 33 patients (26 men, 7 women; mean age 70.5 years) were enrolled. RF ablation was performed using an internally cooled or expandable multitined electrode. The primary endpoint was complete response (CR) determined using ¹⁸F fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) performed 6 months after RF ablation. The secondary endpoint was the incidence and grade of adverse events (AEs) evaluated using the Common Toxicity Criteria for Adverse Events, version 3.0.

Results

All patients underwent RF ablation and had efficacy analyses evaluated; however, FDG-PET/CT images before RF ablation were not available for two patients. The CR rate was 68 % (21 of 31 patients). One patient had a grade 5 AE unrelated to RF ablation. Grade ≥3 AEs occurred in 12 % of patients. During the follow-up period (median 37 months; range 1–55 months), five patients developed local tumor progression and nine (29 %) died. Overall survival at 1, 2, and 3 years was 97, 82, and 74 %, respectively.

Conclusion

Percutaneous RF ablation is a safe, feasible, and effective treatment for small malignant lung tumors.

     

Technique for creation of artificial pneumothorax for pain relief during radiofrequency ablation of peripheral lung tumors: report of seven cases

This report describes seven cases in which a pneumothorax was artificially created for relief from severe pain that occurred during radiofrequency (RF) ablation of peripheral lung tumors. In this procedure, the multitined probe surrounding the lesion was advanced into the chest, displacing the tines and the peripheral tumor away from the parietal pleura and the chest wall and resulting in pain relief in one patient; in the remaining patients, an intravenous catheter was also introduced, followed by the administration of carbon dioxide (CO(2)) into the space between the tumor and the parietal pleura. The pain decreased considerably immediately after this procedure. No complication related to the creation of the artificial pneumothorax was observed. Creation of an artificial pneumothorax is a safe and effective method for pain relief.