Erb J, Klautke G, Seegenschmiedt H M, Engelbrecht R, Schaller G, Sauer R
Klinik und Poliklinik für Strahlentherapie, Universität Erlangen-Nürnberg.
Strahlenther Onkol. 1994 Nov;170(11):654-64.
The increased dissemination of interstitial hyperthermia techniques requires suitable action in quality assurance for the used applicators. This work presents physical-technical methods for complete characterisation of interstitial and endocavitary coaxial antennas used for microwave hyperthermia.
After a short introduction about the antennas' physical principle 2 fundamental experiments for acquisition of specific absorption rate (SAR) are described: There are the thermometric method, especially the power pulse technique, using a static solid state phantom and the direct measurement of the amplitude square of emitted electric field using miniaturized E-field probes in a fluid phantom. Principal problems occurring during E-field measurements in the near field zone of insulated antennas in media (phantom fluid) are discussed in detail.
Characteristic relative SAR profiles were found for each tested applicator design. The profiles were described using the following parameters: depths of SAR maximum, effective heating lengths and lengths of the dead end of the antennas relative to the 50%-iso-SAR-surface. Antenna designs for endocavitary and interstitial purposes were measured at variable insertion depths. The changing SAR-patterns were discussed regarding the found measurement data. Additionally measurements of parallel and inclined antenna arrays consisting of 4 interstitial applicators are described.
The final discussion give future perspectives to forthcoming developments for interstitial and endocavitary microwave hyperthermia.
间质热疗技术的日益普及要求对所用施源器进行适当的质量保证措施。本文介绍了用于全面表征微波热疗间质和腔内同轴天线的物理技术方法。
在简要介绍天线的物理原理后，描述了用于获取比吸收率（SAR）的两个基本实验：一个是使用静态固态体模的测温法，特别是功率脉冲技术；另一个是在流体体模中使用小型化电场探头直接测量发射电场的振幅平方。详细讨论了在介质（体模流体）中绝缘天线近场区域进行电场测量时出现的主要问题。
为每个测试的施源器设计找到了特征性的相对SAR分布。这些分布用以下参数描述：SAR最大值深度、有效加热长度以及天线相对于50%等SAR表面的死端长度。对用于腔内和间质目的的天线设计在不同插入深度下进行了测量。根据测量数据讨论了变化的SAR模式。此外，还描述了由4个间质施源器组成的平行和倾斜天线阵列的测量。
最后的讨论给出了间质和腔内微波热疗未来发展的前景。
