Dielectric-Backed Aperture Resonators for X-Bandin vivoEPR Nail Dosimetry

Abstract

A new resonator for X-band in vivo EPR nail dosimetry, the dielectric-backed aperture resonator (DAR), is developed based on rectangular TE 102 geometry. This novel geometry for surface spectroscopy improves at least a factor of 20 compared to a traditional non-backed aperture resonator. Such an increase in EPR sensitivity is achieved by using a non-resonant dielectric slab, placed on the aperture inside the cavity. The dielectric slab provides an increased magnetic field at the aperture and sample, while minimizing sensitive aperture resonance conditions. This work also introduces a DAR semi-spherical (SS)-TE 011 geometry. The SS-TE 011 geometry is attractive due to having twice the incident magnetic field at the aperture for a fixed input power. It has been shown that DAR provides sufficient sensitivity to make biologically relevant measurements both in vitro and in vivo. Although in vivo tests have shown some effects of physiological motions that suggest the necessity of a more robust finger holder, equivalent dosimetry sensitivity of approximately 1.4 Gy has been demonstrated.

Retrospective and emergency dosimetry in response to radiological incidents and nuclear mass-casualty events: A review

“…The main challenge is to measure EPR signals in the nails while limiting the penetration of the microwave power into the lossy tissue beneath the nail. Surface aperture and coil resonator designs are proposed to address this issue (see also Grinberg et al, 2016 andPetryakov et al, 2016). The challenge of calibration of the fingernails in vivo has not yet been addressed, and questions concerning the effect of the degree of hydration of the in vivo nail, and the stability of the radiationinduced signal while the nail is in vivo also have to be addressed.…”

Developments in Biodosimetry Methods for Triage With a Focus on X-band Electron Paramagnetic Resonance In Vivo Fingernail Dosimetry

“…This approach would be applicable for all individuals regardless of the availability of sufficient nail length and would avoid the need to process nails to remove the interfering mechanically induced signal in nail clippings which occur when the nail is clipped to collect it from a subject (Reyes et al 2008, Black and Swarts 2010, Wilcox et al 2010, He et al 2011, Trompier et al 2014a, Marciniak and Ciesielski 2016). Configurations for in vivo measurements using X-band EPR techniques and specially designed resonators to localize the 9 GHz microwave field from the resonator to interact only with the keratinized fingernails and not the underlying soft tissues on a portable instrument platform for very convenient use in triage are readily envisioned (Sidabras et al 2014, Grinberg et al 2016). Herein is a description of the current status of our in vivo EPR nail dosimetry instrument and the steps needed to move this forward towards a field ready application.…”