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Institute researchers are playing a key role in the quest to understand and use terahertz (THz) radiation, or T-rays. Now, they are developing THz technologies for uses that range from security searches for weapons and toxins, to improved detection of breast and skin cancer, to computers that send messages orders of magnitude faster than is now possible.
Although THz radiation always has been part of the electromagnetic spectrum, it received little attention until the early 1990s. THz radiation, which ranges from 100 gigahertz to 10 terahertz, is but one type of the radiation, or waves of energy, that fills the world around us. Radio waves, the lowest frequencies, carry sound through space. Moving up the spectrum to higher frequencies, the electronic waves are found that carry messages on computer chips and the microwaves that rapidly cook food. Higher still are visible rays (light), X-rays, and others.
Michael Shur, the Patricia W. and C. Sheldon Roberts ’48 Professor of Solid State Electronics, brings to the THz Center his fundamentally new concept of superfast plasma-wave signals on solid-state devices. Shur also serves as director of Rensselaer’s new IBM Center for Broadband Data Transport Science and Technology. Photo by Mark McCarty
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While many of these radiation frequencies have been extremely useful, there has been no technology available to exploit the large band that lies between microwaves and visible light — far infrared, or THz, radiation. That changed about 10 years ago.
Xi-Cheng Zhang, the J. Erik Jonsson ’22 Distinguished Professor of Science at Rensselaer, is one of the leaders in the research that has made THz technology possible. He has developed both emitters to send out THz radiation and detectors to pick up the radiation so information can be obtained from it. His Rensselaer research group has explored the uses of T-rays for imaging and for obtaining spectroscopic information about items that range from dollar bills to breast cancer phantoms.
Now he is the founding director of the Center for Terahertz Research, which brings together scientists from diverse disciplines to collaborate on T-ray technology in projects that range from basic science to the tech transfer needed to put THz products into homes, laboratories, and medical centers.
Other members are Michael Shur, the Patricia W. and C. Sheldon Roberts ’48 Professor of Solid State Electronics and director of the Center for Broadband Data Transport Science and Technology; Roland Kersting, assistant professor of physics and a member of the information technology faculty; and Ingrid Wilke, assistant professor of physics. Participants include Toh-Ming Lu, the Ray Palmer Baker Distinguished Professor of Physics, and Gwo-Ching Wang, the chairwoman of the Department of Physics, Applied Physics, and Astrophysics.
“Working together, the investigators at the Center for Terahertz Research have made remarkable accomplishments, with breakthroughs in microscopy, medical imaging, and new research to identify terrorist threats,” says Dean of Science Joseph Flaherty. “We hope to recruit additional faculty in terahertz science to expand the center’s range and influence and secure our leadership position.”
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Focusing on Breast Cancer
Faculty members in Rensselaer's Center for Terahertz Research believe terahertz radiation, or T-rays, could provide sharper, safer, more informative, and less expensive images for breast cancer detection than current X-ray techniques.
Screening mammography is now the only practical method to detect breast cancer lesions of 1 cm or less, when they are 95 percent curable. But mammography subjects large numbers of women to a sometimes painful test that exposes them to potentially harmful radiation.
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Mammography also is less effective when imaging radiographically dense breasts, and it creates the need for many biopsies in women who do not have cancer.
T-rays are non-ionizing and do not require heavy lead shielding, and they can be focused, creating much sharper pictures. They can give spectroscopic information about the chemical composition as well as the shape and location of the tissue being imaged. T-ray techniques provide high-contrast information about tissues with different water concentrations and about the different bond states of water within the cells and tissues. This ability to identify both the physical and the biochemical
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nature of the cancer would be particularly valuable in diagnosis and choice of treatment in breast cancer.
THz Center Director Xi-Cheng Zhang is working with doctors at the Boston Medical Center to assess the potential of T-ray technology for breast cancer screening and diagnosis. His lab has already produced T-ray images of breast phantoms that are equal or superior to images made by traditional mammograms, and they have obtained very promising results with images of human breast tissue.
The group is now working with the Australia Biomedical Center to test skin cancer cells as well.
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