A promising diagnostic method: Terahertz pulsed imaging and spectroscopy Yiwen Sun, Ming Yiu Sy, Yi-Xiang J Wang, Anil T Ahuja, Yuan-Ting Zhang, Emma Pickwell-MacPherson Yiwen Sun, Ming Yiu Sy, Yuan-ting Zhang, Department of Electronic Engineering, The Chinese University of Hong Kong, Hong Kong, China Yi-Xiang J Wang, Anil T Ahuja, Department of Imaging and Interventional Radiology, The Chinese University of Hong Kong, Hong Kong, China Yuan-ting Zhang, The Institute of Biomedical and Health Engi- neering, Shenzhen Instituted of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518000, Guangdong Province, China Yuan-Tng Zhang, Key Laboratory for Biomedical Informatics and Health Engineering, Chinese Academy of Sciences, Shen- zhen 518000, Guangdong Province, China Emma Pickwell-MacPherson, Department of Electronic and Computer Engineering, Hong Kong University of Science and Technology, Hong Kong, China Author contributions: Wang YXJ gave the idea of the paper was given; Sun Y, Sy MY and Pickwell-MacPherson E collected the data presented; all authors were involved in writing and editing the paper. Supported by in part for this work from the Research Grants Council of the Hong Kong Government and the Shun Hing Insti- tute of Advanced Engineering, Hong Kong Correspondence to: Dr. Emma Pickwell-MacPherson, De- partment of Electronic and Computer Engineering, Hong Kong University of Science and Technology, Hong Kong, China. eeemma@ust.hk Telephone: +852-23585034 Fax: +852-23581485 Received: November 18, 2010 Revised: January 19, 2010 Accepted: January 26, 2010 Published online: March 28, 2011 Abstract The terahertz band lies between the microwave and in- frared regions of the electromagnetic spectrum. This ra- diation has very low photon energy and thus it does not pose any ionization hazard for biological tissues. It is strongly attenuated by water and very sensitive to water content. Unique absorption spectra due to intermolecu- lar vibrations in this region have been found in different biological materials. These unique features make tera- hertz imaging very attractive for medical applications in order to provide complimentary information to existing imaging techniques. There has been an increasing inter- est in terahertz imaging and spectroscopy of biologically related applications within the last few years and more and more terahertz spectra are being reported. This paper introduces terahertz technology and provides a short review of recent advances in terahertz imaging and spectroscopy techniques, and a number of applica- tions such as molecular spectroscopy, tissue character- ization and skin imaging are discussed. © 2011 Baishideng. All rights reserved. Key words: Biomedical; Imaging; Spectroscopy; Tera- hertz Peer reviewer: Yicheng Ni, MD, PhD, Professor, Biomedical Imaging, Interventional Therapy and Contrast Media Research, Department of Radiology, University Hospitals, K.U. Leuven, Herestraat 49, B-3000, Leuven, Belgium Sun Y, Sy MY, Wang YXJ, Ahuja AT, Zhang YT, Pickwell- MacPherson E. A promising diagnostic method: Terahertz pulsed imaging and spectroscopy. World J Radiol 2011; 3(3): 55-65 Available from: URL: http://www.wjgnet.com/1949-8470/full/ v3/i3/55.htm DOI: http://dx.doi.org/10.4329/wjr.v3.i3.55 INTRODUCTION Terahertz (THz, 1 THz = 10 12 Hz) radiation, also known as THz waves, THz light, or T-rays, is situated in the fre- quency regime between optical and electronic techniques. This regime is typically defined as 0.1-10 THz and has become a new area for research in physics, chemistry, bi- ology, materials science and medicine. Experiments with THz radiation date back to measurements of black body radiation using a bolometer in the 1890s [1,2] . However, for a long time, this region remained unexplored due to a lack of good sources and detectors, and it was commonly EDITORIAL World Journal of Radiology WJR Online Submissions: http://www.wjgnet.com/1949-8470ofice wjr@wjgnet.com doi:10.4329/wjr.v3.i3.55 World J Radiol 2011 March 28; 3(3): 55-65 ISSN 1949-8470 (online) © 2011 Baishideng. All rights reserved. 55 March 28, 2011|Volume 3|Issue 3| WJR|www.wjgnet.com