Nuutinen J, Lahtinen T, Turunen M, Alanen E, Tenhunen M, Usenius T, Kolle R
Department of Oncology, Kuopio University Hospital, Finland.
Radiother Oncol. 1998 Jun;47(3):249-54. doi: 10.1016/s0167-8140(97)00234-x.
To measure the dielectric constant of irradiated human skin in order to test the feasibility of the dielectric measurements in the quantitation of acute and late radiation reactions.
The dielectric constant of irradiated breast skin was measured at an electromagnetic frequency of 300 MHz in 21 patients during postmastectomy radiotherapy. The measurements were performed with an open-ended coaxial line reflection method. The irradiation technique consisted of an anterior photon field to the lymph nodes and a matched electron field to the chest wall using conventional fractionation of five fractions/week to 50 Gy. Fourteen out of the 21 patients were remeasured 2 years later and the skin was palpated for subcutaneous fibrosis.
At 5 weeks the dielectric constant had decreased by 31 and 39% for the investigated skin sites of the photon and electron fields, respectively. There was a statistically significant inverse correlation between the mean dielectric constant and the clinical score of erythema. An unexpected finding was a decrease of the dielectric constant of the contralateral healthy skin during radiotherapy. Two years later a statistically significant positive correlation was found between the dielectric constant at the irradiated skin sites and the clinical score of subcutaneous fibrosis.
Dielectric measurements non-invasively yield quantitative information concerning radiation-induced skin reactions.
测量受辐照人体皮肤的介电常数，以检验介电常数测量在定量急性和晚期辐射反应方面的可行性。
在21例乳房切除术后放疗患者中，采用开放式同轴电缆反射法，于300 MHz电磁频率下测量受辐照乳房皮肤的介电常数。照射技术包括对淋巴结采用前光子野，对胸壁采用匹配的电子野，采用每周5次分割至50 Gy的常规分割方式。21例患者中有14例在2年后重新测量，并触诊皮肤以检查皮下纤维化情况。
在第5周时，光子野和电子野所研究皮肤部位的介电常数分别下降了31%和39%。平均介电常数与红斑临床评分之间存在统计学显著的负相关。一个意外发现是放疗期间对侧健康皮肤的介电常数下降。2年后，在受辐照皮肤部位的介电常数与皮下纤维化临床评分之间发现了统计学显著的正相关。
介电常数测量可无创地提供有关辐射诱导皮肤反应的定量信息。
