FESB, University of Split, HR-21000 Split, Croatia.
Sensors (Basel). 2022 Dec 14;22(24):9806. doi: 10.3390/s22249806.
The aim of this study was to investigate how the freezing and thawing of biological tissues affect their complex permittivity in the microwave frequency range from 0.5 MHz to 18 GHz. We measured the complex permittivity of ex vivo bovine tissues, including brain white and grey matter, liver, and muscle, using an open-ended coaxial probe. Bovine tissues were chosen for their availability and similarity to human tissue permittivity. The samples were measured at 25 °C, before they were frozen either in a commercial freezer below -18 °C or in liquid nitrogen, nominally at -196 °C. The measured permittivity before freezing was compared to the permittivity measured after freezing and thawing the tissues back to 25 °C. Statistical analysis of the results showed a statistically significant change in permittivity after freezing and thawing by both methods for all the measured tissues, at least in some parts of the measured frequency range. The largest difference was observed for the white matter, while the liver had the smallest percent change.
本研究旨在探讨生物组织在微波频率范围 0.5MHz 至 18GHz 内的冷冻和解冻过程如何影响其复介电常数。我们使用开口同轴探头测量了牛的离体组织，包括脑白质和灰质、肝和肌肉的复介电常数。选择牛组织是因为其易得性和与人体组织介电常数的相似性。在 25°C 下对样本进行测量，然后将其冷冻在商用冰箱中（低于-18°C）或液氮中（名义上为-196°C）。将冷冻前的介电常数与冷冻和解冻后再恢复至 25°C 时测量的介电常数进行比较。对结果进行统计分析表明，两种方法在所有测量组织中都观察到冷冻和解冻后介电常数发生了统计学上的显著变化，至少在测量频率范围内的某些部分是如此。观察到最大的差异是在白质中，而肝脏的变化百分比最小。
