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Lowell, MA, United States

Doradla P.,University of Massachusetts Lowell | Doradla P.,Biomedical Terahertz Technology Center | Giles R.H.,University of Massachusetts Lowell | Giles R.H.,Biomedical Terahertz Technology Center
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2014

Low-loss, hollow, flexible, metal-coated waveguides were designed and fabricated for the maximal transmission of terahertz radiation. Since recent terahertz skin, colon, and breast cancer studies showed a contrast between normal and diseased tissues between 500 to 600GHz frequencies, flexible metal-coated waveguides with various bore diameters were studied at both 584GHz and 1.4THz frequencies for endoscopic applications. Attenuation characteristics of 2μm thick silver-coated waveguides with 99% reflective inner surface were measured as a function of wavelength, bore diameter, bending angle and bend radius. Though the theoretical attenuation coefficient in metal-coated waveguide varies directly as square of wavelength, the propagation loss was found to be smaller at higher wavelengths. This study demonstrates that flexible waveguides with bore diameters less-than 10λ preserve the linearly polarized mode and hence exhibit low bending losses even at smaller bend radii. Also, in contrast to the lower propagation losses in larger bore tubes, the analysis shows higher transmission in smaller bore tubes at larger bending angles. Finally, the dual-frequency investigation of bending and modal characteristics confirms the feasibility of using these metal-coated flexible waveguides at various terahertz frequencies, to obtain low transmission losses even at greater flexures, in addition to the Gaussian mode preservation. Source


Doradla P.,University of Massachusetts Lowell | Doradla P.,Biomedical Terahertz Technology Center | Alavi K.,University of Massachusetts Medical School | Joseph C.,University of Massachusetts Lowell | And 3 more authors.
Journal of Biomedical Optics | Year: 2014

We demonstrate the design and development of an innovative single-channel terahertz (THz) prototype endoscopic imaging system based on flexible metalcoated THz waveguides and a polarization specific detection technique. The continuous-wave (CW) THz imaging system utilizes a single channel to transmit and collect the reflected intrinsic THz signal from the sample. Since the prototype system relies on a flexible waveguide assembly that is small enough in diameter, it can be readily integrated with a conventional optical endoscope. This study aims to show the feasibility of waveguide enabled THz imaging. We image various objects in transmission and reflection modes. We also image normal and cancerous colonic tissues in reflectance mode using a polarization specific imaging technique. The resulting cross-polarized THz reflectance images showed contrast between normal and cancerous colonic tissues at 584 GHz. The level of contrast observed using endoscopic imaging correlates well with contrast levels observed in ex vivo THz reflectance studies of colon cancer. This indicates that the single-channel flexible waveguide-based THz endoscope presented here represents a significant step forward in clinical endoscopic application of THz technology to aid in in vivo cancer screening. © The Authors. Source


Doradla P.,University of Massachusetts Lowell | Doradla P.,Biomedical Terahertz Technology Center | Alavi K.,University of Massachusetts Medical School | Joseph C.,University of Massachusetts Lowell | And 3 more authors.
Journal of Biomedical Optics | Year: 2013

We demonstrate a reflective, continuous-wave terahertz (THz) imaging system to acquire ex vivo images of fresh human colonic excisions. Reflection measurements of 5-mm-thick sections of colorectal tissues were obtained using a polarization-specific detection technique. Twodimensional THz reflection images of both normal and cancerous colon tissues with a spatial resolution of 0.6mmwere acquired using an optically pumped far-infrared molecular gas laser. Good contrast has been observed between normal and tumorous tissues at 584 GHz frequency. The resulting THz reflection images compared with the tissue histology showed a correlation between cancerous region and increased reflection. We hypothesize that the imaging system and polarization techniques are capable of registering reflectance differences between cancerous and normal colon. However, further investigations are necessary to completely understand the source mechanism behind the contrast and confirm the hypothesis; if true, it likely represents the first continuous-wave THz reflection imaging technique to show sufficient contrast to identify colon tumor margins. Also, it may represent a significant step forward in clinical endoscopic application of THz technology to aid in in vivo colorectal cancer screening. © The Authors. Source


Martin J.P.,University of Massachusetts Lowell | Martin J.P.,Biomedical Terahertz Technology Center | Joseph C.S.,University of Massachusetts Lowell | Joseph C.S.,Biomedical Terahertz Technology Center | And 2 more authors.
Journal of Biomedical Optics | Year: 2016

Biomedical applications of terahertz (THz) radiation are appealing because THz radiation is nonionizing and has the demonstrated ability to detect intrinsic contrasts between cancerous and normal tissue. A linear polarization-sensitive detection technique for tumor margin delineation has already been demonstrated; however, utilization of a circular polarization-sensitive detection technique has yet to be explored at THz frequencies. A reflective, continuous-wave THz imaging system capable of illuminating a target sample at 584 GHz with either linearly or circularly polarized radiation, and capable of collecting both cross-and copolarized signals remitted from the target, is implemented. To demonstrate the system's utility, a fresh ex vivo human skin tissue specimen containing nonmelanoma skin cancer was imaged. Both polarization-sensitive detection techniques showed contrast between tumor and normal skin tissue, although some differences in images were observed between the two techniques. Our results indicate that further investigation is required to explain the contrast mechanism, as well as to quantify the specificity and sensitivity of the circular polarization-sensitive detection technique. © 2016 Society of Photo-Optical Instrumentation Engineers (SPIE). Source

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