微波消融能量传递：功率脉冲对离体和活体肝脏模型中消融结果的影响
Microwave ablation energy delivery: influence of power pulsing on ablation results in an ex vivo and in vivo liver model.
作者信息
Bedoya Mariajose, del Rio Alejandro Muñoz, Chiang Jason, Brace Christopher L
机构信息
Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin 53705 and Department of Radiology, University of Wisconsin-Madison, Madison, Wisconsin 53705.
Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53705 and Department of Radiology, University of Wisconsin-Madison, Madison, Wisconsin 53705.
出版信息
Med Phys. 2014 Dec;41(12):123301. doi: 10.1118/1.4901312.
PURPOSE
The purpose of this study was to compare the impact of continuous and pulsed energy deliveries on microwave ablation growth and shape in unperfused and perfused liver models.
METHODS
A total of 15 kJ at 2.45 GHz was applied to ex vivo bovine liver using one of five delivery methods (n = 50 total, 10 per group): 25 W continuous for 10 min (25 W average), 50 W continuous for 5 min (50 W average), 100 W continuous for 2.5 min (100 W average), 100 W pulsed for 10 min (25 W average), and 100 W pulsed for 5 min (50 W average). A total of 30 kJ was applied to in vivo porcine livers (n = 35, 7 per group) using delivery methods similar to the ex vivo study, but with twice the total ablation time to offset heat loss to blood perfusion. Temperatures were monitored 5-20 mm from the ablation antenna, with values over 60 °C indicating acute cellular necrosis. Comparisons of ablation size and shape were made between experimental groups based on total energy delivery, average power applied, and peak power using ANOVA with post-hoc pairwise tests.
RESULTS
No significant differences were noted in ablation sizes or circularities between pulsed and continuous groups in ex vivo tissue. Temperature data demonstrated more rapid heating in pulsed ablations, suggesting that pulsing may overcome blood perfusion and coagulate tissues more rapidly in vivo. Differences in ablation size and shape were noted in vivo despite equivalent energy delivery among all groups. Overall, the largest ablation volume in vivo was produced with 100 W continuous for 5 min (265.7 ± 208.1 cm(3)). At 25 W average, pulsed-power ablation volumes were larger than continuous-power ablations (67.4 ± 34.5 cm(3) versus 23.6 ± 26.5 cm(3), P = 0.43). Similarly, pulsed ablations produced significantly greater length (P ≤ 0.01), with increase in diameter (P = 0.09) and a slight decrease in circularity (P = 0.97). When comparing 50 W average power groups, moderate differences in size were noted (P ≥ 0.06) and pulsed ablations were again slightly more circular.
CONCLUSIONS
Pulsed energy delivery created larger ablation zones at low average power compared to continuous energy delivery in the presence of blood perfusion. Shorter duty cycles appear to provide greater benefit when pulsing.
目的
本研究旨在比较连续和脉冲能量传输对未灌注和灌注肝脏模型中微波消融生长及形状的影响。
方法
使用五种传输方法之一，将2.45 GHz的15 kJ能量施加于离体牛肝（每组10个，共50个）：25 W连续传输10分钟（平均25 W）、50 W连续传输5分钟（平均50 W）、100 W连续传输2.5分钟（平均100 W）、100 W脉冲传输10分钟（平均25 W）以及100 W脉冲传输5分钟（平均50 W）。使用与离体研究相似的传输方法，但将总消融时间延长一倍以抵消向血液灌注的热损失，将30 kJ能量施加于体内猪肝脏（每组7个，共35个）。在距消融天线5 - 20 mm处监测温度，温度超过60°C表明发生急性细胞坏死。基于总能量传输、施加的平均功率和峰值功率，使用方差分析及事后两两检验对各实验组之间的消融大小和形状进行比较。
结果
在离体组织中，脉冲组和连续组之间的消融大小或圆度未发现显著差异。温度数据表明脉冲消融加热更快，这表明脉冲可能克服血液灌注并在体内更快地凝固组织。尽管所有组的能量传输相当，但在体内仍观察到消融大小和形状的差异。总体而言，体内最大消融体积是由100 W连续传输5分钟产生的（265.7 ± 208.1 cm³）。在平均25 W时，脉冲功率消融体积大于连续功率消融体积（67.4 ± 34.5 cm³对23.6 ± 26.5 cm³，P = 0.43）。同样，脉冲消融产生的长度显著更长（P ≤ 0.01），直径增加（P = 0.09），圆度略有下降（P = 0.97）。比较平均功率为50 W的组时，发现大小存在适度差异（P ≥ 0.06），且脉冲消融再次略更接近圆形。
结论
在存在血液灌注的情况下，与连续能量传输相比，脉冲能量传输在低平均功率下产生更大的消融区。脉冲时较短的占空比似乎能带来更大益处。
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