RESUMEN
PURPOSE: Energy transfer from radiofrequency (RF) applicator to tissue is both precondition and limiting factor. The purpose of this ex vivo study was to examine the influence of form of energy delivery on ablation result during RF ablation with cryo-cooled applicators. MATERIALS AND METHODS: One hundred eight ablations were performed in ex vivo bovine liver under continuous energy delivery (A), pulsed energy delivery with reduced current during ablation pause (B) and impedance-dependent energy delivery. Maximum ablation time was 20âmin. Early termination of ablation in case of loss of conductivity. Optimal ablation parameters were assessed. Short axis diameter of the ablation zone and ablation duration were determined. Ablation results under mode A, B and C were compared with analysis of variance and Tukey-Kramer HSD test. Influence of ablation duration on short axis diameter was evaluated with regression analysis. RESULTS: Significantly largest short axis diameter (51.1âmm ± SD 2.3; pâ=â0.01) was reached with impedance-dependent energy delivery (pulsed: 46.1âmm ± SD 5.6; continuous: 44.4âmm ± SD 4.1). Significantly longest ablation duration (1061.6âs ± SD 42.4; pâ=â0.01) was reached with impedance-dependent energy delivery (pulsed: 815.7âs ±â41.3; continuous: 715.3âs ± SD 82.2). Linear correlation between ablation duration and short axis diameter was calculated (Râ=â0.7). CONCLUSION: Modification of energy delivery during RF ablation with cryo-cooled applicators improves energy transfer to tissue and enables larger ablation zones. KEY POINTS: â¢âImpedance-dependent energy delivery prevents early termination in kryo-based RF-ablation,â¢âImpedance-dependent energy delivery enables larger ablation zones than continuous energy delivery,â¢âReduced current during ablation pause does not improve ablation results.
Asunto(s)
Ablación por Catéter/instrumentación , Ablación por Catéter/métodos , Criocirugía/instrumentación , Criocirugía/métodos , Transferencia Lineal de Energía , Hígado/cirugía , Animales , Bovinos , Diseño de Equipo , Técnicas In Vitro , Hígado/patologíaRESUMEN
BACKGROUND AND OBJECTIVE: A newly developed radio-frequency monopolar needle electrode was evaluated in vitro on porcine tongues. PATIENTS AND METHODS: Porcine tongues with different tissue temperatures (20+/-1) degrees C and (32+/-2) degrees C were coagulated for 90 s. In a second step, 23 coagulations at 7 W were applied (34+/-2) degrees C. RESULTS: The volume of the lesion correlated well with increasing temperature. In step two, the mean energy was 238 J and the mean volume of the lesion was 507 mm(3) (100+/-15)%. Prolonged energy application did not correlate with a larger volume of the lesion. CONCLUSION: The new radio-frequency needle electrode can reduce tongue volume in a precise and controlled manner (SD+/-15%).