Lahtinen T, Nuutinen J, Alanen E, Turunen M, Nuortio L, Usenius T, Hopewell J W
Department of Oncology, Kuopio University Hospital, Research Institute for Radiotherapy Physics, University of Kuopio, Finland.
Int J Radiat Oncol Biol Phys. 1999 Feb 1;43(3):635-8. doi: 10.1016/s0360-3016(98)00439-8.
Radiation-induced fibrosis is a common late reaction of radiation therapy. Due to a lack of feasible noninvasive techniques to assess this reaction, the long-term development of radiation fibrosis is not well described. In order to develop quantitative means for the purpose, subcutaneous fibrosis of breast cancer patients after postmastectomy radiotherapy was evaluated by clinical scoring and a new technique based on dielectric properties of the skin.
Dielectric properties of biological tissues at radiofrequencies are principally determined by tissue water content. The major skin components are proteins, proteoglycans, and water either free or bound to the surface of proteins and proteoglycans. Since the MR studies have shown that bound water is tightly attached onto the surface of collagen, a dielectric measurement sensitive to bound water could be related to the protein content. Therefore, the dielectric constant of human skin was measured in vivo with an open-ended coaxial probe at electromagnetic (EM) frequencies in the range of delta-dispersion. Since the in vitro experiments with protein-water solutions have indicated that the slope of the dielectric constant vs. the EM frequency is a measure of the protein concentration, a respective slope was determined with irradiated skin of 14 breast cancer patients 2 years after postmastectomy radiotherapy at 63, 100, 300, and 500 MHz. Irradiated skin sites were clinically scored for subcutaneous fibrosis using a scale: none, slight, moderate, or severe fibrosis.
A statistically significant correlation was found between the slope and the clinical score of subcutaneous fibrosis at 63, 100, and 300 MHz but not at 500 MHz. The correlation was best at 100 and 300 MHz.
Considerable changes in the dielectric constant of the irradiated skin were found. The correlation between the dielectric constant and clinical score suggests that this novel technique is a potential tool for the follow-up and quantitative assessment of radiation-induced subcutaneous fibrosis.
放射性纤维化是放射治疗常见的晚期反应。由于缺乏可行的非侵入性技术来评估这种反应，放射性纤维化的长期发展情况尚未得到充分描述。为了开发用于此目的的定量方法，通过临床评分和基于皮肤介电特性的新技术对乳腺癌患者乳房切除术后放疗后的皮下纤维化进行了评估。
生物组织在射频下的介电特性主要由组织含水量决定。皮肤的主要成分是蛋白质、蛋白聚糖以及游离或结合在蛋白质和蛋白聚糖表面的水。由于磁共振研究表明结合水紧密附着在胶原蛋白表面，对结合水敏感的介电测量可能与蛋白质含量相关。因此，使用开放式同轴探头在δ色散范围内的电磁（EM）频率下对人体皮肤的介电常数进行了体内测量。由于蛋白质 - 水溶液的体外实验表明介电常数与EM频率的斜率是蛋白质浓度的一种度量，在63、100、300和500 MHz下对14例乳腺癌患者乳房切除术后放疗2年后的照射皮肤确定了相应的斜率。使用无、轻度、中度或重度纤维化的量表对照射皮肤部位的皮下纤维化进行临床评分。
在63、100和300 MHz时，斜率与皮下纤维化的临床评分之间存在统计学上的显著相关性，但在500 MHz时未发现。在100和300 MHz时相关性最佳。
发现照射皮肤的介电常数有相当大的变化。介电常数与临床评分之间的相关性表明，这种新技术是用于放射性皮下纤维化随访和定量评估的潜在工具。
