Korean J Radiol.  2003 Mar;4(1):27-34. 10.3348/kjr.2003.4.1.27.

Percutaneous Radiofrequency Thermal Ablation with Hypertonic Saline Injection: In Vivo Study in a Rabbit Liver Model

• Lee JM
• Kim YK
• Lee YH
• Kim SW
• Li CA
• Kim CS

• KMID: 754039
• DOI: http://doi.org/10.3348/kjr.2003.4.1.27

Abstract

OBJECTIVE
To determine whether hypertonic saline (HS, 36% NaCl) injection prior to or during radiofrequency ablation (RFA) can increase the extent of thermally mediated coagulation in in-vivo rabbit liver tissue, and also to establish the ideal injection time in relation to RFA in order to maximize its effect on the extent of radiofrequency (RF) -induced coagulation. MATERIALS AND METHODS: In 26 rabbits, 43 RFA lesions were produced using a 17-gauge internally cooled electrode with a 1-cm active tip under ultrasound (US) guidance. Rabbits were assigned to one of three groups: Group A: RFA alone (n=8) ; Group B: RFA after the instillation of 1 mL HS (n=8) ; Group C: RFA after and during the instillation of 0.5 mL HS (n=10). RF energy (30 W) was applied for 3 minutes, and changes occurring in tissue impedance, current, power output, and the temperature of the electrode tip were automatically measured. After RFA, contrast-enhanced spiral CT was performed, and in each group the maximum diameters of the thermal lesions in gross specimens were compared. Technical success and the complications arising were evaluated by CT and on the basis of autopsy findings. RESULTS: All procedures were technically successful. There were six procedure-related complications (6/26; 23%), including five localized perihepatic hematomas and one thermal injury to the stomach. With instillation of HS in group B rabbits, markedly decreased tissue impedance (73 omega+/-5) and increased current (704 mA+/-41) were noted, compared to RF ablation without saline infusion (116.3 omega+/-13, 308 mA+/-80). With instillation of the solution before RFA (group B), coagulation necrosis was greater (14.9 mm+/- 3.8) than in rabbits not injected (group A: 11.5 mm+/-2.4; Group A vs. B: p < .05) and in those injected before and during RFA (group C: 12.5 mm+/-3.1; Group B vs. C: p > .05). CONCLUSION: RFA using HS instillation can increase the volume of RFAinduced necrosis of the liver with a single application, thereby simplifying and accelerating the treatment of larger lesions. In addition, HS instillation before RFA more effectively achieves coagulation necrosis than HS instillation before and during RFA.

Keyword

Experimental study; Liver, interventional procedures; Radiofrequency ablation

Figure

• 

  Fig. 1 Graphic depiction of the changes occurring in tissue impedance, RF current and power during radiofrequency ablation in the four groups. Left: In a Group A rabbit, tissue impedance increased sharply and current decreased during RF energy instillation. Middle and Right: In Group B rabbits (middle) and those of Group C (right), an abrupt increase in tissue impedance after RF energy instillation was prevented by the infusion of NaCl solution.

• 

  Fig. 2 Radiofrequency ablation without the use of saturated saline in a Group A rabbit. A. Left: A 17-gauge RF electrode and a 21-gauge coated Chiba needle (arrow) were placed in the left lobe of the liver under ultrasound guidance. Right: After radiofrequency ablation, an echogenic area (arrow) was produced around the electrode. B. At post-procedural CT scanning, a 10-mm round defect (arrow) corresponding to the area of coagulative necrosis is apparent. C. Gross specimen demonstrating the presence of a light brown, coagulative, 10-mm necrotic zone surrounded by a peripheral hemorrhagic rim (arrows).

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  Fig. 3 Radiofrequency ablation with saturated saline pretreatment in a Group B rabbit. A. At post-procedural CT scanning, a 15-mm diameter, oval-shaped perfusion defect (arrow) is seen. B. Gross specimen shows that the liver contains a light brown coagulative necrotic zone (arrowhead), 15-mm in diameter.

• 

  Fig. 4 Radiofrequency ablation with saturated saline infusion before and during the procedure in a Group C rabbit. A. Contrast-enhanced transverse CT scan of the liver obtained one week after RF ablation; two wedge-shaped defects (arrows) are seen. B. Gross specimen demonstrating the presence of two light brown coagulative necrotic zones (arrows) in the liver. C. Microscopic image shows typical coagulation necrosis (arrows) of the ablated lesions.

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