THz spectroscopy and imaging of major human organ tissues for cancer margin assessment

Summary form only given. The sensitivity of THz waves to tissue hydration levels in excised specimen enables clinical, in-situ discrimination of cancerous vs. normal tissue regions (Z. D. Taylor et al., IEEE Trans. Terahertz Sci. Technol., 1(1), 201-219, 2011 and M. H. Arbab et al., J. Biomed. Opt., 18(7), 077004, 2013). However, previous studies on THz biomedical imaging of human tissue groups have been largely disconnected, with publications focusing on only a few tissue groups at a time. In addition, assessment of cancer margins to differentiate in-situ extent of disease has not been a major focus. As such, a more general consideration of the THz response of major human tissue groups has not been available. To address this shortcoming, we are focusing on a comprehensive assessment of THz spectroscopic properties of major human tissue groups and associated primary and metastatic malignancies using broadband time domain THz spectroscopy in the 60GHz-3THz band. In an effort to document the THz response of different tissue groups and malignancies as uniformly and as completely as possible, we employ a fixed protocol for the preparation and the characterization of all tissue specimens. Freshly excised tissues as well as formalin-fixed paraffin-embedded samples are characterized using a reflection-mode THz imaging system. Subsequently, we extract the refractive index and absorption properties of the samples. Moreover, using various locations in the samples, statistical averages for index and absorption coefficient of normal and cancerous regions are calculated. Among the studied tissue groups are freshly-excised tissues from human heart, pancreas, thyroid, liver, and stomach and formalin-fixed liver and brain tissues. Using formalinfixed liver tissue with metastatic colon cancer, we present a comprehensive study to differentiate cancer margins. In addition, a comparative study is performed to investigate the effect of formalin fixing on THz properties. In all cases, it is demonstrated that discriminatory information can be readily obtained from the THz images. We will present the THz reflection responses and cancer margin detection for the major human organ tissue groups.