Mertyna Pawel, Dewhirst Mark W, Halpern Elkan, Goldberg Wallace, Goldberg S Nahum
Laboratory for Minimally Invasive Tumor Therapies, Department of Radiology, Beth Israel Deaconess Medical Center, Boston, Massachusetts 02215, USA.
Int J Hyperthermia. 2008 Nov;24(7):550-9. doi: 10.1080/02656730802035662.
To determine the effects of applied current, distance from an RF electrode and baseline tissue temperature upon thermal dosimetry requirements to induce coagulation in ex vivo bovine liver and in vivo porcine muscle models.
RF ablation was performed in ex vivo liver at varying baseline temperatures-19-21 degrees C (n = 114), 8-10 degrees C (n = 27), and 27-28 degrees C (n = 27)-using a 3-cm tip electrode and systematically varied current 400-1,300 mA, to achieve defined diameters of coagulation (20, 30 and 40 +/- 2 mm), and in in vivo muscle (n = 18) to achieve 35 mm +/- 2 mm of coagulation. Thermal dose required for coagulation was calculated as the area under the curve and cumulative equivalent minutes at 43 degrees C.
Thermal dose correlated with current in a negative exponential fashion for all three diameters of coagulation in ex vivo experiments (p < 0.001). The temperatures at the end of RF heating at the ablation margin were not reproducible, but varied 38 degrees C-74.7 degrees C, for 30 mm coagulation in ex vivo liver, and 59.8 degrees C-68.4 degrees C in the in vivo experiment. CEM(43) correlated with current as a family of positive exponential functions (r(2) = 0.76). However, a very wide range of CEM(43) values (on the order of 10(15)) was noted. Although baseline temperatures in the ex vivo experiment did not change required thermal dose, the relationships between end temperature at the ablation margin and RF current were statistically different (p < 0.001) as analysed at the 400 mA intercept.
In both models, thermal dosimetry required to achieve coagulation was not constant, but current and distance dependent. Hence, other formulas for thermal dose equivalence may be needed to predict conditions for thermal ablation.
确定施加电流、与射频电极的距离以及基线组织温度对在离体牛肝和活体猪肌肉模型中诱导凝固所需热剂量测定的影响。
使用3厘米尖端电极，在不同基线温度（19 - 21摄氏度，n = 114；8 - 10摄氏度，n = 27；27 - 28摄氏度，n = 27）的离体肝脏中进行射频消融，并系统地改变电流（400 - 1300毫安），以实现特定直径的凝固（20、30和40 ± 2毫米），在活体肌肉中（n = 18）实现35毫米 ± 2毫米的凝固。凝固所需的热剂量计算为曲线下面积和43摄氏度下的累积等效分钟数。
在离体实验中，对于所有三种凝固直径，热剂量与电流呈负指数关系（p < 0.001）。射频加热结束时消融边缘的温度不可重复，在离体肝脏中30毫米凝固时温度在38摄氏度至74.7摄氏度之间变化，在活体实验中为59.8摄氏度至68.4摄氏度。CEM(43)与电流呈正指数函数族关系（r(2) = 0.76）。然而，注意到CEM(43)值的范围非常广泛（约为10(15)）。尽管离体实验中的基线温度并未改变所需热剂量，但在400毫安截距处分析时，消融边缘的最终温度与射频电流之间的关系在统计学上存在差异（p < 0.001）。
在两种模型中，实现凝固所需的热剂量测定并非恒定，而是与电流和距离有关。因此，可能需要其他热剂量等效公式来预测热消融的条件。
