In terahertz reflection imaging, a deconvolution process is often employed to extract the impulse function of the sample of interest. A band-pass filter such as a double Gaussian filter is typically incorporated into the inverse filtering to suppress the noise, but this can result in over-smoothing due to the loss of useful information. In this paper, with a view to improving the calculation of terahertz impulse response functions for systems with a low signal to noise ratio, we propose a hybrid Frequency-Wavelet Domain Deconvolution (FWDD) for terahertz reflection imaging. Our approach works well; it retrieves more accurate impulse response functions than existing approaches and these impulse functions can then also be used to better extract the terahertz spectroscopic properties of the sample.

We have previously demonstrated that terahertz pulsed imaging is able to distinguish between rat tissues from different healthy organs. In this paper we report our measurements of healthy and cirrhotic liver tissues using terahertz reflection spectroscopy. The water content of the fresh tissue samples was also measured in order to investigate the correlations between the terahertz properties, water content, structural changes and cirrhosis. Finally, the samples were fixed in formalin to determine whether water was the sole source of image contrast in this study. We found that the cirrhotic tissue had a higher water content and absorption coefficient than the normal tissue and that even after formalin fixing there were significant differences between the normal and cirrhotic tissues' terahertz properties. Our results show that terahertz pulsed imaging can distinguish between healthy and diseased tissue due to differences in absorption originating from both water content and tissue structure.

Terahertz pulsed imaging (TPI) is a non-ionizing and non-destructive imaging technique that has been recently used to study a wide range of biological materials. The severe attenuation of terahertz radiation in samples with high water content means that biological samples need to be very thin if they are to be measured in transmission geometry. To overcome this limitation, samples could be measured in reflection geometry and this is the most feasible way in which TPI could be performed in a clinical setting. In this study, we therefore used TPI in reflection geometry to characterize the terahertz properties of several organ samples freshly harvested from laboratory rats. We observed differences in the measured time domain responses and determined the frequency-dependent optical properties to characterize the samples further. We found statistically significant differences between the tissue types. These results show that TPI has the potential to accurately differentiate between tissue types non-invasively.

For imaging applications involving biological subjects, the strong attenuation of terahertz radiation by water means that terahertz pulsed imaging is most likely to be successfully implemented in a reflection geometry. Many terahertz reflection geometry systems have a window onto which the sample is placed - this window may introduce unwanted reflections which interfere with the reflection of interest from the sample. In this paper we derive a new approach to account for the effects of these reflections and illustrate its success with improved calculations of sample optical properties.

Seven new compounds, named coelovirins A-G (1-7), along with fourteen known constituents were isolated from the rhizomes of Coeloglossom viride var. bracteatum (Orchidaceae). On the basis of chemical and spectroscopic methods, including 2D-NMR techniques, the structures of new compounds were elucidated as 1-(4-beta-D-glucopyranosyloxybenzyl)-(2R,3S)-2-isobutyltartrate (1), 4-(4-beta-glucopyranosyloxybenzyl)-(2R,3S)-2-isobutyltartrate (2), 1-(4-beta-D-glucopyranosyloxybenzyl)-(2R,3S)-2-beta-D-glucopyranosyl-2-isobutyltartrate (3), 4-(4-beta-D-glucopyranosyloxybenzyl)-(2R,3S)-2-beta-D-glucopyranosyl-2-isobutyltartrate (4), (2R,3S)-2-beta-D-glucopyranosyl-2-isobutyltartaric acid (5), bis(4-beta-D-glucopyranosyloxybenzyl)-(2R,3S)-2-[beta-D-glucopyranosyl-(1 --> 4)-beta-D-glucopyranosyl]-2-isobutyltartrate (6) and bis(4-beta-D-glucopyranosyloxybenzyl)-(2R)-2-[beta-D-glucopyranosyl-(1 --> 4)-beta-D-glucopyranosyl]-2-isobutylmalate (7). The known compounds are 4-hydroxybenzaldehyde, 4-hydroxybenzyl alcohol, 4,4'-dihydroxydibenzyl ether, 4,4'-dihydroxydiphenylmethane, 4-(4-hydroxybenzyloxy)benzyl alcohol, gastrodin, quercetin-3,7-diglucoside, thymidine, loroglossin, militarine, dactylorhin A, dactylorhin B, beta-sitosterol and daucosterol.