| Part one: the determination on the essential thermal parameters in visualization phantomObjective: To create a kind of simple, convenient and cheap visualization phantom in order to display the size morphous of the radio frequency ablation focus, assess the radio frequency temperature field preliminarily, and detect the major thermal parameters and compare the differences with the biological tissue.Methods:①the concentration in volume of egg albumen prepared in visualization phantom was 10%, 20% and 30%, respectively.②the radio frequency ablation experiment was carried out by taking the same parameter constitution in each group phantom, and formed the concretionary focus.③the ablation focus photograph was obtained from the digital camera for observing its morphology, and analyzed by computer software to measure the length, breadth and height of the concretionary focus, which can calculated the size of the focus through the volume equation of sphere; the differences of the size and distinctness among the three group were also compared.④Use the principle of heat conservation to measure the specific heat capacity of the phantom.⑤Use the hot-line method to measure the thermal conductivity coefficient of the phantom.Results:①the appearance of solid finished product is transparent and yellowish, which deepen with the concentration of egg albumen increased.②the ablation focus appeared in each group, but the distinctness in 10% concentration group was lower than the other two groups, the differences in observing the size of the ablation focus between 20% group and 30% group reached no statistical significance.③the comparison of the volume ablation focus among the three groups were as followed: Other than the statistically non-significant differences between 20% group and 30% group (P>0.05), the differences among other groups were all statistically significant(P<0.05).④the following was the measurement of the thermotics parameters: the densityρ=1.016 g/ml, the specific heat capacity specific heat Cpw=3611.55 Js/kg/℃, the thermal conductivity coefficient K=0.389±0.044.Conclusions: the creation of visualization phantom was simple and cheap. As compared with other groups, the 20% group can display the ablation focus morphology clearly, and its thermal parameters was similar to the isolated biological tissues, which can be used for foundational research in radio frequency temperature field.Part two: an influence on the morphology and size of the ablation focus as the conditions of radio frequency experiment changed in visualization phantomObjective: In actual operation, there were various kinds of impacted factors on the final morphology of the radio frequency ablation focus; an influence on the morphology and size of the ablation focus was observed by changing the parameter constitution of radio frequency ablation . To make sure the formed focus more close to the condition of real tissues, which make a foundation of the next step to the formal measurement in the distribution of the radio frequency temperature field.Methods:①The radio frequency ablation was performed group by group in phantom; on the installations of other parameters unchanged, five parameter was altered respectively, which included the distance between the radio-frequency electrode and electrode plate, the extent of temperature heightened, the pattern of temperature heightened, the time length and the size of unfolded bursa diameter. The ablation focus photograph was obtained from the digital camera for observing its morphology, and analyzed by computer software to measure the length, breadth and height of the concretionary focus, which can calculated the size of the focus through the volume equation of sphere.②Radio frequency ablation was performed in the same parameter constitution by using the integrity and mono-end radio frequency electrode respectively, and continual temperature in 8 spaces was measured, in order to compare the differences in ablation focus morphology of two groups and temperature changes of same space.Results:①In four experiment groups, which contained the distance between the radio-frequency electrode and electrode plate, the extent of temperature heightened, the time length and the size of unfolded bursa diameter, the alteration of correlated parameter led to the size of the ablation focus changed, and reached significant differences(P<0.05); Among them, the alteration of distance between the radio-frequency electrode and electrode plate can lead to the long diameter of ablation focus changed. In the pattern of temperature heightened group, minimum temperature pattern did not form the valid ablation focus, and the differences in the size of the ablation focus between maximum temperature pattern and average temperature pattern were no significant(P>0.05).②the differences in the ablation focus morphology between the integrity and mono-end radio frequency electrode were statistically significant, and the latter was similar to the one eighth of ellipsoid which was cut off. The results of continual temperature in the same space position reached statistical significance (P<0.05).Conclusions: According to the radio frequency ablation in visualization phantom, we had obtained the initial recognition of the distribution of the radio frequency temperature field which range from 60℃to 70℃. We found that the size of the ablation focus was gradually increased by radio frequency time prolonged, the power reinforced and the bursa diameter unfolded within certain extent, and the correlate parameter constitution of the focus ablation which was relatively suitable for observation was establish in less volume phantom. The alteration of morphology in radio frequency electrode had great impact on the ablation focus morphology, which was possible beneficial to make special electrode for conformal ablation.Part three: the measurement of radio frequency ablation’s real-time temperature field in phantom and isolated tissue Objective: To determine the radio frequency temperature field from two kinds of radio frequency electrodes in the phantom, and compare with the temperature variety of isolated tissue at the radio frequency ablation, guiding the clinical application.Methods: The StarBurst XL electrode and the StarBurst SDE electrode were used in visualization phantom to form ablation focus, and its temperature was detected by temperature sensitive galvanic couple needle respectively according to lattice method. The three-dimension interval of each space point in XL electrode ablation focus was 5 mm, and in SDE electrode was 2.5 mm; sample interval of measure was 0.02 s. All data were collected and recorded by computer, and obtained the radio-frequency electrode temperature field distribution of the two by analytical 3D reconstruction. The radio frequency temperature alterations were detected in ex vivo swine erector spinae of the XL electrode and in ex vivo prostate phantom of the SDE electrode with the same method.(the results measured were only the maximum coronal plane of the ablation focus in each space point ) The differences in isothermal peripheria of the same bitplane and time-dependent temperature of the same space point between the phantom and ex vivo tissue in two kinds of electrodes were compared respectively.Results: The results of the distribution temperature field were obtained from the XL electrode and the SDE electrode and expressed by isothermal peripheria diagram pattern and three dimensional isothermal peripheria district diagram pattern in each space bitplane. The formed ablation focus of the XL electrode in the phantom had the anastomotic isothermal peripheria diagram in each space bitplane on the whole, as compared with that in the ex vivo tissue; and there were no significant difference between them in the time-dependent temperature of the same space point.(P>0.05) However, the results of the XL star polygon electrode were probably the same with those of the SDE electrode.Conclusions: The results of the distribution temperature field were obtained from the radio-frequency electrode, and got better concordance in the phantom and ex vivo tissue, which will be applied to conduct the clinical radio-frequency ablation treatment and has important instructional value in the subtle control of the radio-frequency ablation region.Part four: the detection preliminary study of radio frequency real-time temperature field in vivo cyno-prostateObjective: To verify the correctness of the results from the radio frequency temperature field in the phantom, using living zooperal method.Methods: Adult living Beagle dogs were used in this study. The SDE radio frequency electrode was imported into cyno-prostate for radio-frequency ablation with ultrasound guided. A needle for temperature detection was set in the prostate which was 5 mm from the electrode simultaneously, and the real-time temperature change was recorded. The SDE electrode top itself has three thermocouples for temperature detection, therefore, crush damage of temperature change in four groups was recorded and compared with temperature change in the same space point.Results: In the same space point, the time of maximum temperature in prostate was longer than that in the phantom, but there were no significant differences in final temperature between them.(P>0.05) Conclusions: The results of the temperature field in the phantom were the same with the in vivo study, which may make an accurate estimate for the clinical actual size of the radio frequency focus. |
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