Radio-frequency thermal ablation with NaCl solution injection: effect of electrical conductivity on tissue heating and coagulation-phantom and porcine liver study.

PURPOSE To characterize the effects of NaCl concentration on tissue electrical conductivity, radio-frequency (RF) deposition, and heating in phantoms and optimize adjunctive NaCl solution injection for RF ablation in an in vivo model. MATERIALS AND METHODS RF was applied for 12-15 minutes with internally cooled electrodes. For phantom experiments (n = 51), the NaCl concentration in standardized 5% agar was varied (0%-25.0%). A nonlinear simplex optimization strategy was then used in normal porcine liver (n = 44) to determine optimal pre-RF NaCl solution injection parameters (concentration, 0%-38.5%; volume, 0-25 mL). NaCl concentration and tissue conductivity were correlated with RF energy deposition, tissue heating, and induced coagulation. RESULTS NaCl concentration had significant but nonlinear effects on electrical conductivity, RF deposition, and heating of agar phantoms (P<.01). Progressively greater heating was observed to 5.0% NaCl, with reduced temperatures at higher concentrations. For in vivo liver, NaCl solution volume and concentration significantly influenced both tissue heating and coagulation (P<.001). Maximum heating 20 mm from the electrode (102.9 degrees C +/- 4.3 [SD]) and coagulation (7.1 cm +/- 1.1) occurred with injection of 6 mL of 38.5% (saturated) NaCl solution. CONCLUSION Injection of NaCl solution before RF ablation can increase energy deposition, tissue heating, and induced coagulation, which will likely benefit clinical RF ablation. In normal well-perfused liver, maximum coagulation (7.0 cm) occurs with injection of small volumes of saturated NaCl solution.

[1]  G. Gazelle,et al.  Percutaneous tumor ablation: increased coagulation by combining radio-frequency ablation and ethanol instillation in a rat breast tumor model. , 2000, Radiology.

[2]  R. Paczynski,et al.  Automated measurement of infarct size with scanned images of triphenyltetrazolium chloride-stained rat brains. , 1996, Stroke.

[3]  A L Baert,et al.  Ex vivo experiment on radiofrequency liver ablation with saline infusion through a screw-tip cannulated electrode. , 1997, The Journal of surgical research.

[4]  P. S. Hamilton,et al.  Creation of large thermal lesions in liver using saline-enhanced RF ablation , 1997, Proceedings of the 19th Annual International Conference of the IEEE Engineering in Medicine and Biology Society. 'Magnificent Milestones and Emerging Opportunities in Medical Engineering' (Cat. No.97CH36136).

[5]  R. Lufkin,et al.  Preliminary experience with MR-guided thermal ablation of brain tumors. , 1995, AJNR. American journal of neuroradiology.

[6]  E F Halpern,et al.  Radio-frequency tissue ablation: effect of pharmacologic modulation of blood flow on coagulation diameter. , 1998, Radiology.

[7]  S. Deming,et al.  An automated iterative algorithm for the quantitative analysis of in vivo spectra based on the simplex optimization method , 1989, Magnetic resonance in medicine.

[8]  L Solbiati,et al.  Hepatic metastases: percutaneous radio-frequency ablation with cooled-tip electrodes. , 1997, Radiology.

[9]  G. Gazelle,et al.  Thermal ablation therapy for focal malignancy: a unified approach to underlying principles, techniques, and diagnostic imaging guidance. , 2000, AJR. American journal of roentgenology.

[10]  J. Lewin,et al.  Invited. Interactive MRI‐guided radiofrequency interstitial thermal ablation of abdominal tumors: Clinical trial for evaluation of safety and feasibility , 1998, Journal of magnetic resonance imaging : JMRI.

[11]  G. Gazelle,et al.  Variables affecting proper system grounding for radiofrequency ablation in an animal model. , 2000, Journal of vascular and interventional radiology : JVIR.

[12]  D I Rosenthal,et al.  Radiofrequency tissue ablation: importance of local temperature along the electrode tip exposure in determining lesion shape and size. , 1996, Academic radiology.

[13]  Toshihito Seki,et al.  Ultrasonically guided percutaneous microwave coagulation therapy for small hepatocellular carcinoma , 1994, Cancer.

[14]  W. R. Lees,et al.  Liver Tumor Ablation by Interstitial Laser Photocoagulation: Review of Experimental and Clinical Studies , 1993 .

[15]  M Takahashi,et al.  Treatment of hepatocellular carcinoma: value of percutaneous microwave coagulation. , 1995, AJR. American journal of roentgenology.

[16]  L Solbiati,et al.  Percutaneous radiofrequency tissue ablation: does perfusion-mediated tissue cooling limit coagulation necrosis? , 1998, Journal of vascular and interventional radiology : JVIR.

[17]  F. Garbagnati,et al.  Percutaneous treatment of small hepatic tumors by an expandable RF needle electrode. , 1998, AJR. American journal of roentgenology.

[18]  P R Mueller,et al.  Radio frequency ablation of renal cell carcinoma via image guided needle electrodes. , 1999, The Journal of urology.

[19]  T. Livraghi,et al.  Hepatocellular carcinoma and cirrhosis in 746 patients: long-term results of percutaneous ethanol injection. , 1995, Radiology.

[20]  G. Gazelle,et al.  Hepatocellular carcinoma: radio-frequency ablation of medium and large lesions. , 2000, Radiology.

[21]  L Solbiati,et al.  Saline-enhanced radio-frequency tissue ablation in the treatment of liver metastases. , 1997, Radiology.

[22]  E. Patterson,et al.  Radiofrequency ablation of porcine liver in vivo: effects of blood flow and treatment time on lesion size. , 1998, Annals of surgery.

[23]  M Deimling,et al.  Malignant liver tumors treated with MR imaging-guided laser-induced thermotherapy: technique and prospective results. , 1995, Radiology.

[24]  H. H. Pennes.  Analysis of tissue and arterial blood temperatures in the resting human forearm. 1948. , 1948, Journal of applied physiology.

[25]  W W Mayo-Smith,et al.  Percutaneous radiofrequency ablation of malignancies in the lung. , 2000, AJR. American journal of roentgenology.

[26]  W R Lees,et al.  Minimally invasive treatment of malignant hepatic tumors: at the threshold of a major breakthrough. , 2000, Radiographics : a review publication of the Radiological Society of North America, Inc.

[27]  G S Gazelle,et al.  Radio-frequency-induced coagulation necrosis in rabbits: immediate detection at US with a synthetic microsphere contrast agent. , 1999, Radiology.

[28]  K. Fujiwara,et al.  Small hepatocellular carcinoma: treatment with US-guided intratumoral injection of acetic acid. , 1994, Radiology.

[29]  L Solbiati,et al.  Small hepatocellular carcinoma: treatment with radio-frequency ablation versus ethanol injection. , 1999, Radiology.

[30]  Eric R. Cosman,et al.  Theoretical aspects of radiofrequency lesions in the dorsal root entry zone. , 1984 .

[31]  G S Gazelle,et al.  Percutaneous radiofrequency tissue ablation: optimization of pulsed-radiofrequency technique to increase coagulation necrosis. , 1999, Journal of vascular and interventional radiology : JVIR.

[32]  W R Lees,et al.  Interstitial laser photocoagulation as a treatment for breast cancer , 1994, The British journal of surgery.

[33]  L Solbiati,et al.  Large-volume tissue ablation with radio frequency by using a clustered, internally cooled electrode technique: laboratory and clinical experience in liver metastases. , 1998, Radiology.

[34]  J. Lewin,et al.  Effects of superparamagnetic iron oxide on radio-frequency-induced temperature distribution: in vitro measurements in polyacrylamide phantoms and in vivo results in a rabbit liver model. , 1999, Radiology.

[35]  F A Jolesz,et al.  Focused US system for MR imaging-guided tumor ablation. , 1995, Radiology.

[36]  G. Gazelle,et al.  Radiofrequency tissue ablation: increased lesion diameter with a perfusion electrode. , 1996, Academic radiology.