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Increased ablation zones using a cryo-based internally cooled bipolar RF applicator in ex vivo bovine liver.

Abstract：

PURPOSE:To evaluate the feasibility of ex vivo ablation implementing a cryo-based internally cooled bipolar radiofrequency (RF) applicator and to determine the influence of power and gas pressure on the size and shape of the resulting ablation zones. MATERIALS AND METHODS:Two hundred twenty-five ablations were performed using a custom-built internally CO2-cooled bipolar cryo RF applicator in ex vivo bovine livers. The active tip of the applicator was 55 mm long. RF power (32-50 watts) and gas pressure of cooling medium (500-600 psi) were varied independently. Power was applied in continuous mode. Control group experiments were carried out solely using the RF function at 32, 40, and 50 watts. Ablation duration was 15 minutes for all applications. Experiments were repeated 5 times for all parameter combinations. Short and long axes of the induced white ablation zone were macroscopically assessed. The ablation zone was referred to as homogeneous if complete ablation was observed without spots of untreated tissue. The short axis diameters for the simultaneous application of cryo and RF function were analyzed using a multiple linear regression analysis. An unpaired Mann-Whitney U test was used to analyze the differences between the short axes with RF alone and RF using cryo cooling. RESULTS:All ablation zones were homogeneous. Using simultaneous RF ablation function and gas cooling with a single applicator, the long axes of the ablation zones ranged between 42 +/- 2 mm (mean +/- SD) and 59 +/- 5 mm, the short axes between 24 +/- 1 and 44 +/- 1 mm, depending on the parameter combination. At a stable gas pressure level, short axes increased with rising power levels and decreased after reaching a maximum. The maxima of the short axis increased with higher gas pressure levels and were shifted to higher power values. Optimal parameter settings were 46 to 50 watts and 600 psi gas pressure, resulting in a short axis of 44 +/- 1 mm. Short axis weakly correlated with gas pressure (r2 = 0.10) and power (r2 = 0.34) alone, whereas the correlation was r2 = 0.76 for the combined factors. Without cooling, short axis diameters were significantly shorter (P < 0.05), ranging between 13 +/- 2 mm at 50 watts and 15 +/- 2 mm at 32 watts. CONCLUSION:The results of this initial ex vivo study show that the combined cryo RF ablation device allows for large ablation volumes using a single needle, which is superior to RF ablation alone.

journal_name

Invest Radiol

journal_title

Investigative radiology

authors

Rempp H,Voigtländer M,Clasen S,Kempf S,Neugebauer A,Schraml C,Schmidt D,Claussen CD,Enderle MD,Goldberg SN,Pereira PL

doi

10.1097/RLI.0b013e3181b66d11

subject

Has Abstract

pub_date

2009-12-01 00:00:00

pages

763-8

issue

eissn

0020-9996

issn

1536-0210

journal_volume

pub_type

杂志文章

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Increased ablation zones using a cryo-based internally cooled bipolar RF applicator in ex vivo bovine liver.