Abstract

Purpose

The accuracy of a numerical simulation of cryoablation ice balls was evaluated in gel phantom data as well as clinical kidney and lung cases.

Materials and methods

To evaluate the accuracy, 64 experimental single-needle cryoablations and 12 multi-needle cryoablations in gel phantoms were re-simulated with the corresponding freeze-thaw-freeze cycles. The simulated temperatures were compared over time with the measurements of thermocouples. For single needles, temperature values were compared at each thermocouple location. For multiple needles, Euclidean distances between simulated and measured isotherms (10 °C, 0 °C, −20 °C, −40 °C) were computed. Furthermore, surface and volume of simulated 0 °C isotherms were compared to cryoablation-induced ice balls in 14 kidney and 13 lung patients. For this purpose, needle positions and relevant anatomical structures defining material parameters (kidney/lung, tumor) were reconstructed from pre-ablation CT images and fused with postablation CT images (from which ice balls were extracted by manual delineation).

Results

The single-needle gel phantom cases showed less than 5 °C prediction error on average. Over all multiple needle experiments in gel, the mean and maximum isotherm distance were less than 2.3 mm and 4.1 mm, respectively. Average Dice coefficients of 0.82/0.63 (kidney/lung) and mean surface distances of 2.59/3.12 mm quantify the prediction performance of the numerical simulation. However, maximum surface distances of 10.57/10.8 mm indicate that locally larger errors have to be expected.

Conclusion

A very good agreement of the numerical simulations for gel experiments was measured and a satisfactory agreement of the numerical simulations with measured ice balls in patient data was shown.

中文翻译：

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冷冻消融数值模拟的评估–与基准数据，临床肾脏和肺部病例的比较

摘要

目的

在凝胶体模数据以及临床肾脏和肺部病例中评估了冷冻消融冰球数值模拟的准确性。

材料和方法

为了评估准确性，凝胶体模中的64个实验性单针冷冻消融和12个多针冷冻消融用相应的冻融-冻结-冷冻周期进行了重新模拟。将模拟温度随时间与热电偶的测量值进行比较。对于单针，在每个热电偶位置比较温度值。对于多针，计算了模拟和测量的等温线（10°C，0°C，-20°C，-40°C）之间的欧几里得距离。此外，将14位肾脏和13位肺部患者的模拟0°C等温线的表面和体积与冷冻消融诱导的冰球进行了比较。为此，针的位置和相关的解剖结构定义了材料参数（肾脏/肺，

结果

单针凝胶体模病例平均显​​示小于5°C的预测误差。在所有的凝胶多针实验中，平均和最大等温线距离分别小于2.3 mm和4.1 mm。平均骰子系数为0.82 / 0.63（肾脏/肺），平均表面距离为2.59 / 3.12 mm，量化了数值模拟的预测性能。但是，最大表面距离为10.57 / 10.8 mm，表明必须预料到更大的局部误差。

结论

测量了凝胶实验数值模拟的很好一致性，并且在患者数据中显示了与测得的冰球数值模拟的令人满意的一致性。