ABSTRACT
Objective To determine the power-time-ablation scope correlogram of a water-cooled single needle electrode radiofrequency (RF) ablation system and to establish a theoretical basis for its practical application.Methods RF ablations were performed using a water-cooled single needle electrode radiofrequency ablation system developed by the authors using fresh ox liver as well as liver and muscles of healthy adult New Zealand white rabbits.The temperature of the ablation area was monitored using a multichannel thermometric system.The maximum ablation scope was determined by detecting the rim at which the temperature was no less than 50 °C.The specific absorption rate (SAR) of the isolated liver tissue was calculated.Results In the treatment voltage range of 100-130V,the process was smooth and steady.No impedance variation was obvious.The maximum diameter of a single ablation was 51 cm.With the treatment voltage at 140-170 V,a larger ablation area could be reached in less time,but eventually the impedance began to increase while the ablation area was no longer expanded.When the treatment voltage reached the range of 180-200 V the impedance almost always increased rapidly out of limits,and the treatment system stopped automatically.The measured SAR value was consistent with the theoretical value.Pathology confirmed that both liver tissue and muscle tissue manifested typical coagulative necrosis.Conclusions The power amplifier,cooling,thermometric and control sections of the RF ablation system worked stably,and the practical ablation effect met the design and clinical treatment requirements.
ABSTRACT
Effective dose of laser photocoagulation in proliferative diabetic retinopathy. We retrospectively studied 153 eyes of 106 patients to know correlation between the regression and the amount of retinal ablation, and to know clinical result after panretinal photocoagulation. Regression was observed in 100 eyes (65.4%), stationary status in 39 eyes (25.5%) and progression in 14 eyes (9.2%) in the 6 to 8 weeks following treatment. Stabilization was achieved in 98 eyes (64.1%) in the minimum follow-up of one year. Regression was observed in 78 eyes(79.6%) of low risk PDR versus 22 eyes (40.0%) of high risk PDR, and it was statistically significant (p=0.0001). The mean ablation area was 231.01+/-83.54 mm2. In high risk PDR, ablation area of eyes which were regressed was 279.33+/-111.39 mm2, compared to 220.42+/-91.61 mm2 which were not regressed(p=0.0337). In low risk PDR, there are no correlation between the ablation area and regression. Vision was decreased after photocoagulation 31 eyes(20.3%), and cystoid macular edema(CME) was the main cause of visual loss, however, the CME was not correlated with ablation area. Regression of new vessel was highly correlated with ablation area in high risk PDR.