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首页> 外文期刊>Bioelectrochemistry >Measurement and simulation of Joule heating during treatment of B-16 melanoma tumors in mice with nanosecond pulsed electric fields
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Measurement and simulation of Joule heating during treatment of B-16 melanoma tumors in mice with nanosecond pulsed electric fields

机译：纳秒脉冲电场治疗小鼠B-16黑色素瘤的过程中焦耳热的测量和模拟

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摘要

Experimental evidence shows that nanosecond pulsed electric fields (nsPEF) trigger apoptosis in skin tumors.We have postulated that the energy delivered by nsPEF is insufficient to impart significant heating to the treated tissue. Here we use both direct measurements and theoretical modeling of the Joule heating in order to validate this assumption. For the temperature measurement, thermo-sensitive liquid crystals (TLC) were used to determine the surface temperature while a micro-thermocouple (made from 30 μm wires) was used for measuring the temperature inside the tissue. The calculation of the temperature distribution used an asymptotic approach with the repeated calculation of the electric field, Joule heating and heat transfer, and the subsequent readjustment of the electrical tissue conductivity. This yields a temperature distribution both in space and time. It can be shownthat for themeasured increase in temperature an unexpectedly high electrical conductivity of the tissue would be required, which was indeed found by using voltage and current monitoring during the experiment. Using impedance measurements within t_(after) = 50 μs after the pulse revealed a fast decline of the high conductivity state when the electric field ceases. The experimentally measured high conductance of a skin fold (mouse) between plate electrodes was about 5 times higher than those of the maximally expected conductance due to fully electroporated membrane structures (G_(max)/G_(electroporated)) ≈ 5. Fully electroporated membrane structure assumes that 100% of themembranes are conductive which is estimated from an impedance measurement at 10MHzwheremembranes are capacitively shorted. Since the temperature rise in B-16mouse melanoma tumors due to equally spaced (Δt=2 s) 300 ns-pulseswith E=40 kV/cmusually does not exceed ΔΤ=3Katall parts of the skin fold between the electrodes, a hyperthermic effect on the tissue can be excluded.
机译：实验证据表明，纳秒脉冲电场（nsPEF）会触发皮肤肿瘤的细胞凋亡。我们推测nsPEF传递的能量不足以给被治疗的组织带来明显的热量。在这里，我们使用焦耳加热的直接测量和理论模型来验证该假设。对于温度测量，使用热敏液晶（TLC）确定表面温度，同时使用微热电偶（由30μm导线制成）测量组织内部的温度。温度分布的计算采用渐近方法，其中包括重复计算电场，焦耳热和热传递以及随后重新调整组织电导率。这产生了空间和时间上的温度分布。可以看出，对于所测量的温度升高，将需要组织的出乎意料的高电导率，这确实是通过在实验期间使用电压和电流监测来发现的。在脉冲显示t_（after）= 50μs后使用阻抗测量表明，当电场停止时，高电导率状态快速下降。由于完全电穿孔的膜结构（G_（max）/ G_（electroporated））≈5，实验测得的板电极之间皮肤褶皱（鼠标）的高电导率比最大预期电导率高约5倍。该结构假定100％的膜是导电的，这是根据10MHz处的阻抗测量（其中膜被电容性短路）估算的。由于等距间隔（Δt= 2 s）的300 ns脉冲（E = 40 kV / cm）引起的B-16小鼠黑素瘤肿瘤的温度升高通常不超过ΔΤ= 3，电极之间皮肤的所有部分都会折叠，因此对可以排除组织。

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