A new resonant geometry for X-band in vivo electron paramagnetic resonance (EPR) nail dosimetry has been developed, fabricated, and tested. The dielectric-backed aperture resonator (DAR) was specifically designed for depth-limited surface spectroscopy. The DAR improves EPR sensitivity of surface samples with sub-millimeter thicknesses by at least a factor of 20 compared to other aperture resonator designs. The increase in EPR sensitivity was achieved using a non-resonant dielectric slab which is placed on the aperture inside the cavity. The dielectric slab provides an increased microwave magnetic field, while minimizing the problematic resonance conditions of the aperture. It has been shown that the DAR provides sufficient sensitivity to make biologically-relevant measurements both in vitro and in vivo. This work demonstrates that in vivo tests with an equivalent dosimetry sensitivity of approximately 1.4 Gy are feasible. Plausible ways to further increase the sensitivity are discussed, such as, the introduction and simulations of a DAR based on a semi-spherical TE011 geometry.

中文翻译：

---

用于 X 波段深度受限的体内 EPR 指甲剂量测定的介电支撑孔径谐振器

一种用于 X 波段体内电子顺磁共振 (EPR) 钉剂量测定的新谐振几何结构已被开发、制造和测试。电介质背衬孔径谐振器 (DAR) 专为深度受限的表面光谱而设计。与其他孔径谐振器设计相比，DAR 将亚毫米厚度表面样品的 EPR 灵敏度提高了至少 20 倍。EPR 灵敏度的增加是通过使用放置在腔内孔上的非谐振电介质板实现的。电介质板提供了增强的微波磁场，同时最大限度地减少了孔的共振条件。已经表明，DAR 提供了足够的灵敏度，可以在体外和体内进行生物学相关的测量。这项工作表明，等效剂量测定灵敏度约为 1.4 Gy 的体内试验是可行的。讨论了进一步提高灵敏度的可行方法，例如基于半球形 TE011 几何形状的 DAR 的引入和模拟。