Time and temperature dependence of radiofrequency ablation in the human placenta

Ablative effect of the interstitial laser setting in the human placental model

AIM

To assess the impact of laser power and time on interstitial ablation generated by neodymium-doped yttrium aluminium garnet (Nd:YAG) and diode laser in the human placental model.

METHODS

The experiment was carried out in a simulation model of interstitial laser ablation on ex-vivo placental tissue. One-hundred and forty-four pieces of fresh placentae were interstitially ablated with Nd:YAG or diode laser at various power (15, 20, 25, 30 W)-time (5, 10, 15 s) combinations. The ablation tissues were evaluated using both sonographic and histopathologic measurements.

RESULTS

Laser generator, power, and time significantly affected the ablation size (p < 0.001). The coagulation zone continuously increased with extending time at the power of 15, 20, and 25 W. When adjusting to the power of 30 W, increased time from 10 to 15 s did not induce the larger coagulation diameter. The maximal diameter was obtained at the laser power of 20 W for 15 s. The ablation from the diode laser was greater than that from Nd:YAG laser. The sonographic evaluation overestimated the ablation size by an average of 24%.

CONCLUSION

Diode laser destroys greater tissue than Nd:YAG laser. Different power settings of interstitial laser ablation produce diverse patterns of correlation between laser time and coagulation size.

Prognostic value of enhancement rate by enhanced ultrasound in hepatitis B virus-positive hepatocellular carcinoma undergoing radiofrequency ablation

AIM

To assess the prognostic significance of enhancement rate (ER) measured by contrast-enhanced ultrasonography (CEUS) in patients with hepatocellular carcinoma (HCC) undergoing radiofrequency ablation (RFA).

MATERIALS AND METHODS

A total of 253 patients with single primary HCC undergoing preoperative CEUS and RFA were enrolled in this study. The ER were evaluated though pretreatment CEUS. After a mean follow-up of 36.8 ± 10.2 months, the correlation of ER measured by CEUS and survival after RFA was analyzed by univariate and multivariate analysis. The optimal cutoff ER value to predict survival was determined using receiver-operating characteristic analysis.

RESULTS

Mean follow-up period for all 253 patients was 36.8 ± 10.2 months, 31.2% of patients had died at endpoint. The optimal cutoff ER value predicting survival was 2.2 dB/s. Univariate analysis demonstrated that patients with a high ER level had poorer OS (62.8 months vs 48.8 months, P = 0.02) and recurrence-free survival (RFS = 60.2 months vs 47.4 months, P = 0.03) than patients with a low ER level. ER measured by CEUS also been confirmed as independent risk factor for overall survival (hazard ratio [HR], 1.87; 95% confidence interval [95% CI], 1.21-7.25; P < 0.01) and RFS (HR, 1.67; 95% CI, 1.08-6.21; P < 0.01) in multivariate analysis enrolling gender, BMI, tumor size, antiviral therapy, HBV DNA, histological differentiation, Child-Pugh score and tumor node metastasis (TNM) stage.

CONCLUSIONS

ER measured by CEUS was a significant predictive factor for survival after RFA for HCC.