Department of Radiation Oncology, Academic Medical Center, University of Amsterdam, The Netherlands.
Int J Hyperthermia. 2010;26(2):171-84. doi: 10.3109/02656730903397321.
Contact flexible microstrip applicators (CFMA) are applied for superficial hyperthermia. In the clinic these flexible applicators are mostly applied bent along the body curvature. This paper investigates the specific absorption rate (SAR) patterns of CFMA applicators, when bent around an elliptical tissue-equivalent phantom.
The 2H (aperture size 14.8 x 14.3 cm(2)), 3H (28.7 x 20.7 cm(2)), 4H (19.6 x 19.6 cm(2)) and 5H (19.7 x 28.5 cm(2)) applicators were examined. Measurements were performed for the 5H applicator; existing measurement data were analysed for the 3H applicator. Finite difference time domain (FDTD) simulations with a resolution of 2 x 2 x 1 mm(3) were performed for all applicators. Applicators were bent around the top and the side of the elliptical phantom to examine different curvatures. The SAR deposition, effective field size (EFS) and effective heating depth (EHD) were evaluated and compared to results for straight applicators.
Bending the applicators generally yielded a focusing effect of the SAR, which was most pronounced with a strong curvature, but especially the 5H applicator showed a stronger power absorption at the sides of the applicator, compared to the centre region. The EFS became smaller when bending the applicators; this effect was also more pronounced for a strong curvature. The EHD increased for bent applicators, but the degree depended strongly on the location.
The behaviour of bent CFMA applicators is not trivial and the SAR deposition is not similar for all applicators. The EFS decreases and the EHD increases, but very locally. Therefore, it is generally advisable to analyse the SAR distribution of flexible applicators in both straight and bent state.
接触式柔性微带贴片（CFMA）应用于浅层热疗。在临床上，这些柔性贴片通常会沿着身体的曲线弯曲使用。本文研究了 CFMA 贴片在围绕椭圆组织等效体模弯曲时的比吸收率（SAR）分布。
研究了 2H（孔径尺寸 14.8 x 14.3 cm(2)）、3H（28.7 x 20.7 cm(2)）、4H（19.6 x 19.6 cm(2)）和 5H（19.7 x 28.5 cm(2)）贴片。对 5H 贴片进行了测量；对 3H 贴片分析了现有的测量数据。对所有贴片都进行了分辨率为 2 x 2 x 1 mm(3)的有限差分时域（FDTD）模拟。围绕椭圆体模的顶部和侧面弯曲贴片，以检查不同的曲率。评估并比较了 SAR 沉积、有效场尺寸（EFS）和有效加热深度（EHD），并与直贴片的结果进行了比较。
弯曲贴片通常会产生 SAR 的聚焦效应，这种效应在曲率较大时最为明显，但特别是 5H 贴片在贴片的侧面显示出比中心区域更强的功率吸收。当弯曲贴片时，EFS 会变小；这种效应在曲率较大时更为明显。弯曲的贴片会增加 EHD，但程度强烈依赖于位置。
弯曲的 CFMA 贴片的行为并非微不足道，而且并非所有贴片的 SAR 沉积都相同。EFS 减小，EHD 增加，但非常局部。因此，通常建议在直和弯曲状态下分析柔性贴片的 SAR 分布。
