In recent years, pioneered studies in the field of terahertz (THz) technology followed by great advances in laser technology have opened the new area for a wide range of THz applications including THz imaging of semiconductor characterization, chemical analysis, and biological and medical imaging. Biomedical application of THz technology is based on the fact that the collective vibrational modes of many biomaterials such as proteins and DNA molecules are predicted to occur in the THz range. In addition, biological sample does not suffer from THz radiation thanks to the nonionizing and noninvasive properties.

Label-Free THz DNA Chips

A DNA (deoxyribonucleic acid) molecule consists of two complementary chains of nucleotides. Hydrogen bonds between base pairs of the nucleotides hold the two chains together. Hence, detecting the binding states of DNA is a key process for genetic analysis. By performing the THz transmission experiment, we obtained the relative change of refractive index of single and double stranded DNA. This result demonstrates the potential applications of THz techniques to identify the binding state of DNA molecules.

Collaboration teams : Asan Medical Center and Collage of Medicine, University of Ulsan

Cervical cancer is the second most common malignancy in women worldwide and is the only major gynecological malignancy clinically staged according to the International Federation of Obstetrics and Gynecology (FIGO) recommendations. The prognostic factors identified in cervical cancer patients are tumor size, depth of stromal invasion, presence of lymphovascular tumor emboli, histologic type, and invasion of surgical margins. Lymph node metastasis is also closely associated with poor prognosis and decreased survival rate; moreover, this metastasis is an indicator for adjuvant radiotherapy. Computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography-CT (PET-CT) have been used to detect metastatic lymph nodes in cervical cancer patients, but their accuracies were lower than expected. In one study of cervical cancer patients negative for metastatic lymph nodes by MRI, the sensitivity of PET in detecting metastatic lymph nodes was only 10%. The accurate diagnosis of metastatic lymph nodes is of clinical importance, the lack of sensitive diagnostic methods indicates the need for additional imaging modalities. In recent years, terahertz (THz) imaging technology has shown great promise and has increasingly been performed for cancer diagnosis and treatment. Although THz imaging may improve the diagnosis of metastatic lymph nodes in cervical cancer patients, it has not yet been evaluated in this setting. Therefore, in this work, we report a pilot study for THz imaging to detect lymph node micro-metastases in early-stage cervical cancer patients, which are usually undiagnosed by conventional imaging methods.

THz Imaging of Cervical Cancer Lymph Nodes

In collaboration with Asan Medical Center, Department of Radiology, University of Ulsan, and Department of Orthopedic Surgery, Ajou University

Osteoarthritis (OA), one of the most prevalent chronic diseases in the elderly, is characterized by progressive degeneration of cartilage. Cartilage degeneration is affected by biochemical alterations, including an increase in water content and the loss of proteoglycans. Several studies have shown that the water content in osteoarthritic cartilage may increase by about 10%. Therefore, a precise measurement of the water content in cartilage can aid in the diagnosis of early-stage OA. However, changes in the water content in the early stages of OA cannot be detected using current clinical techniques such as radiography and arthroscopy. Only magnetic resonance imaging (MRI) has been used for the detection of water content in the early stages of OA.

Terahertz time-domain spectroscopy (THz TDS) has recently been developed because of recent advances in THz technology. THz TDS is a coherent and non-ionizing method that can quantify the complex refractive index from both the phase and amplitude information of a medium. Moreover, this method can also probe low frequency vibrational modes of biomolecules, thus providing structural and functional information about biological tissue. Because water has strong absorptions across the entire THz frequency range, THz images will likely show a good image contrast dependent on the changes in medium water content. In this work, for the first time, we report on the THz imaging and characterization of water distribution in human articular cartilage. Although THz pulses imaging technique is still in early stage, our results demonstrate the potential capability of THz pulses imaging as a useful diagnostic tool in biomedicine.