There are three major challenges in cancer imaging using terahertz electromagnetic waves, which are the limited penetration depth into wet tissues, the difficulty to observe terahertz fingerprints (resonance markers) of cancers, and the poor contrast between healthy and diseased tissues. This presentation addresses such issues in detail and explains the potential solutions to them with recent results.
In this report, a novel type of highly sensitive small molecule sensing tool has been employed to detect residual pesticide molecules including e. g. methomyl using terahertz (THz) time-domain spectroscopy (TDS) system with nano-slotantenna array. Enhance THz wave by the nano-slot-antenna array induces strong THz field enhancement around nano antenna and thus increases an absorption cross section leading to the detection sensitivity upto ppm level even in solution state. Measured spectrums in transmission and reflection show an excellent performance in both sensitivity and selectivity. We also tested the performance of our nano-antenna array in reflection imaging geometry to simply detect the contained residual pesticide at the real fruit surface as it is, without any extraction or sampling preprocess. The clear difference in the obtained THz reflection image distinguishes the stained area with methomyl from the bare area. Our observation can offer the possibility for further application as a prompt and an accurate small molecule monitoring tool in real time. A quantitative analysis tool for such small molecule can be also developed by this method.
In this study, we measured the optical characteristics of pesticides by terahertz time-domain spectroscopy. Pesticide samples were prepared as pellets that were mixed with polyethylene powder and placed in the center of the path of a terahertz electromagnetic (EM) wave in the spectroscopy system. The absorbance of each sample showed obvious differences in absorption peaks. From this result, we showed that these pesticide products had resonance modes in the terahertz range, and this method can be used to make a sensor that is able to measure low concentrations of pesticides in farm produce.
We show that terahertz (THz) time-domain spectroscopy (TDS) can be used to characterize the blood. The complex optical constants of blood and its constituents, such as water, plasma, and red blood cells (RBCs), were obtained in the THz frequency region. The volume percentage of RBCs in blood was extracted and compared with the conventional RBC counter results. The THz absorption constants are shown to vary linearly with the RBC concentration in both normal saline and whole blood. The excellent linearity between the THz signal and the RBC concentration was also confirmed in a polyurethane resin tube using a THz imaging method. These results demonstrate that THz-TDS imaging can facilitate the quantitative analysis of blood.