Zhang Aili, Xu Lisa X, Sandison George A, Zhang Jiayao
School of Mechanical Engineering, Purdue University, 47907, West Lafayette, IN, USA.
Cryobiology. 2003 Oct;47(2):143-54. doi: 10.1016/j.cryobiol.2003.08.002.
The morphology of cancerous breast tissue is characterized by tightly packed groups of small malignant cells, as found in most duct cell carcinoma. This special structure affects the osmotic responses of the cells to freezing and hence their probability of damage from cellular dehydration or intracellular ice formation. A mathematical model has been developed to study the microscale damage to these breast cancer cells during cryosurgery by accounting for their special structure. The model is based on a spherical unit comprised of an extracellular region that surrounds several layers of cancer cells, as experimentally observed of breast duct cell carcinoma by other researchers. Temperature transients in the breast cancer undergoing cryosurgery are calculated numerically using the Pennes equation. When subjected to various thermal histories, both cellular dehydration and intracellular ice formation in the unit structure are examined by considering the cell-to-cell contact and water transport at the microscale level. It is found that the cells in the inner layers hardly dehydrated while those in the outermost layer do greatly. The results help interpret the previously observed experimental phenomena that breast cancer tissues exhibit intracellular ice formation even at a slow cooling rate of -3 degrees C/min. In the attempt to better define an optimal procedure for breast cancer cryosurgery, various freezing protocols are simulated. The constant heat flux protocol induces greater cellular dehydration and higher intracellular ice formation probability simultaneously compared to the other protocols studied.
癌性乳腺组织的形态特征是存在紧密堆积的小恶性细胞群，这在大多数导管细胞癌中都能发现。这种特殊结构会影响细胞对冷冻的渗透反应，进而影响其因细胞脱水或细胞内结冰而受损的概率。已开发出一个数学模型，通过考虑这些乳腺癌细胞的特殊结构来研究冷冻手术过程中对其造成的微观损伤。该模型基于一个球形单元，该单元由围绕几层癌细胞的细胞外区域组成，这是其他研究人员对乳腺导管细胞癌进行实验观察得到的结果。使用彭尼斯方程对接受冷冻手术的乳腺癌中的温度瞬变进行数值计算。当经历各种热历史时，通过考虑微观层面的细胞间接触和水传输，研究单元结构中的细胞脱水和细胞内结冰情况。结果发现，内层细胞几乎不脱水，而最外层细胞脱水严重。这些结果有助于解释先前观察到的实验现象，即乳腺癌组织即使在-3℃/分钟的缓慢冷却速率下也会出现细胞内结冰。为了更好地确定乳腺癌冷冻手术的最佳程序，模拟了各种冷冻方案。与所研究的其他方案相比，恒定热流方案会同时导致更大程度的细胞脱水和更高的细胞内结冰概率。
