Dose-effect relationships of bipolar radio frequency heating / 中华物理医学与康复杂志

ABSTRACT

Objective To study the effect of the preset temperature,heating time and the spacing of radio frequency electrodes.Methods Fresh egg white was used to study the effects of heater spacing,temperature and heating time.Two electrodes were fixed to keep the needles perpendicular to the center of egg white confined on a square plate.Temperatures from 50 to 90℃ were tested with heating times of 60 and 120 seconds and electrode spac ings of 2.0,1.0,0.5 and 0.25 centimetres.The real-time temperature and the time to the appearance of a spindleshaped bridge between the electrodes was observed.The egg white's impedance and resistance,the lowest temperature of denaturation,and the mass (or volume) denatured at different time points were also observed.Results With an electrode spacing of 2 cm and the thermostat set at 63℃,the true electrode temperatures were 63.7 and 52.6℃,with the secondary electrode the cooler.Significant differences between the secondary electrode temperature and the preset temperature as well as the temperature between the primary and the secondary electrodes were observed.It was also found that different electrode spacing caused significant differences between the preset temperature and the primary as well as the secondary electrode temperature.Denaturation began at 56℃ with a spacing of 0.25 cm.At spacings of 0.25 and 0.50 cm,a spindle-shaped connection between the two electrodes was observed at temperatures above 70℃,but higher temperature was required at 1.00 and 2.00 cm.When the spacing was 0.25 cm and the preset temperature was 75℃,the denatured volume after 60 s of heating was 90.21+0.64 mm3.Heating for 120 s denatured 95.08+ 0.53 mm3 and two 60.s heatings 92.88+0.74 mm3,all significant differences.There were no significant differences in the resistance of the egg white before and after a single heating for 60 s,but after a single heating lasting 120 s it had increased significantly from 128.41+8.04 to 121.29±8.04 Ω.Conclusion Bipolar radio frequency heating can denature egg white.Higher temperature,longer heating and smaller electrode spacing heat more effectively.