Theoretical Estimations of Safety Thresholds for Terahertz Exposure of Surface Tissues

This paper contributes to the topic of radiation safety in the THz band by providing theoretical estimations of the permissible incident power densities over 100 GHz-10 THz. Microthermal absorption has been characterized and a worst-case analysis has been done to provide thresholds for the tissue-internal electric field strength at THz frequencies. Dielectric models for the skin and the cornea of the eye as exposed surface tissues have been constructed and used to estimate the corresponding thresholds for incident power densities. The findings of this study shall be useful as a new theoretical framework for future studies related to THz radiation safety and regulation.

[1]  S. Alekseev,et al.  Human skin permittivity determined by millimeter wave reflection measurements , 2007, Bioelectromagnetics.

[2]  M C Ziskin,et al.  Millimeter wave dosimetry of human skin , 2008, Bioelectromagnetics.

[3]  Soichi Watanabe,et al.  ICNIRP Guidelines on Limits of Exposure to Laser Radiation of Wavelengths between 180 nm and 1,000 μm. , 2013, Health physics.

[4]  P. Yalavarthy,et al.  Modeling of Terahertz Heating Effects in Realistic Tissues , 2013, IEEE Journal of Selected Topics in Quantum Electronics.

[5]  W S Grundfest,et al.  Stratified Media Model for Terahertz Reflectometry of the Skin , 2011, IEEE Sensors Journal.

[6]  Soichi Watanabe,et al.  Guidelines on limits of exposure to laser radiation of wavelengths between 180 nm and 1,000 microm. International Commission on Non-Ionizing Radiation Protection. , 1996, Health physics.

[7]  W. J. Ellison,et al.  Water: a dielectric reference , 1996 .

[8]  A. Sihvola Mixing Rules with Complex Dielectric Coefficients , 2000 .

[9]  Sonja Huclova,et al.  Modelling and validation of dielectric properties of human skin in the MHz region focusing on skin layer morphology and material composition , 2012 .

[10]  W. Grundfest,et al.  THz Medical Imaging: in vivo Hydration Sensing , 2011, IEEE Transactions on Terahertz Science and Technology.

[11]  U. Pfeiffer,et al.  Attempts for exposure assessment in the THz-frequency range using numerical computations , 2012, International Symposium on Electromagnetic Compatibility - EMC EUROPE.

[12]  W. J. Ellisona Permittivity of Pure Water, at Standard Atmospheric Pressure, over the Frequency Range 0–25 THz and the Temperature Range 0–100 °C , 2007 .

[13]  Jacob Stolarski,et al.  Modeling of surface thermodynamics and damage thresholds in the IR and THz regime , 2007, SPIE BiOS.

[14]  V. Wallace,et al.  Biomedical applications of terahertz technology , 2006 .

[15]  Gerald J. Wilmink,et al.  Invited Review Article: Current State of Research on Biological Effects of Terahertz Radiation , 2011 .

[16]  Peter Uhd Jepsen,et al.  Terahertz Reflection Spectroscopy of Aqueous NaCl and LiCl Solutions , 2009 .

[17]  T. Manabe,et al.  A model for the complex permittivity of water at frequencies below 1 THz , 1991 .

[18]  A. Ahlbom Guidelines for limiting exposure to time-varying electric, magnetic, and electromagnetic fields (up to 300 GHz) , 1998 .

[19]  V. Wallace,et al.  In vivo study of human skin using pulsed terahertz radiation , 2004, Physics in medicine and biology.

[20]  E. Heilweil,et al.  Pulsed terahertz spectroscopy of DNA, bovine serum albumin and collagen between 0.1 and 2.0 THz , 2000 .

[21]  K. Meek,et al.  Refractive indices of the collagen fibrils and extrafibrillar material of the corneal stroma. , 1997, Biophysical journal.

[22]  P. Taday,et al.  Terahertz Pulsed Spectroscopy of Human Basal Cell Carcinoma , 2006, Applied spectroscopy.

[23]  C Gabriel,et al.  The dielectric properties of biological tissues: I. Literature survey. , 1996, Physics in medicine and biology.

[24]  G. Gallerano,et al.  Terahertz Radiation Effects and Biological Applications , 2009 .

[25]  D R Hose,et al.  Modelled current distribution in cervical squamous tissue. , 2002, Physiological measurement.

[26]  Robert E. Miles,et al.  Optical properties of tissue measured using terahertz-pulsed imaging , 2003, SPIE Medical Imaging.

[27]  R. W. Lau,et al.  The dielectric properties of biological tissues: III. Parametric models for the dielectric spectrum of tissues. , 1996, Physics in medicine and biology.

[28]  R. W. Lau,et al.  The dielectric properties of biological tissues: II. Measurements in the frequency range 10 Hz to 20 GHz. , 1996, Physics in medicine and biology.

[29]  Derek Abbott,et al.  Modeling terahertz heating effects on water. , 2010, Optics express.