| From top, photos show a basal cell carcinoma. Clinical photo matches a THz Pulsed Image (TPI) which shows the tumor at a depth of 100 祄, highlighted in red due to high absorption of THz. The third photo is of the TPI 1000. Source: TeraView |
Within the EM spectrum lies an underdeveloped frequency range with great potential for medical and military applications.
Sandwiched between microwave and infrared, the THz region has generated a buzz among spectroscopists and researchers alike. Decreased costs and its ability to conduct non-destructive analyses are driving the market to explore this option, particularly in the medical arena. "Advances in T-ray generation sources and detectors have led this once esoteric technology to become mainstream", says Daniel Mittleman, Asst. Prof. at Rice Univ., Houston, Texas.
THz tools
This forward-looking trend is evidenced in offerings such as the Terahertz Pulsed Imaging (TPI) 1000-spectrometer system, developed by TeraView, Cambridge, UK and Bruker Optics, Billerica, Mass. Unveiled at the International Conference on Advanced Vibrational Spectroscopy (ICAVS) this past August, the TPI 1000 is marketed as the world's first stand-alone terahertz spectrometer system. Here, a THz probe, scanner, and a visible laser source are housed into one portable unit, loosely resembling a photocopier on wheels.
The device features a spectral range of 40 GHz -4 THz, spectral resolution of 3 GHz, and the option to have an N2purged chamber, critical for reducing the effects of water absorption. Due to its ability to recognize specific spectral fingerprints of certain cancers, TPI technology, packaged into a portable system, could easily compete with more traditional methods. Its developers note that the system has already been used to successfully image basel cell carcinomas in patients.
Picometrix, Ann Arbor, Mich., is also experimenting with new avenues in THz products. In 2000, it released its response towards the push to THz: the T-Ray 2000. This system with a .02-2 THz bandwith, and ~1 GHz resolution, is finding applications in medical and government markets, with NASA currently using the T-Ray 2000 imaging system to survey the voids in the foam insulation applied to the space shuttle's external tank.
Academia weighs in
One of the largest groups conducting THz research is at the Insitut f黵 Halbleitertechnik, Aachen, Germany. Led by Peter Bolivar, the group is experimenting with the use of non-destructive THz spectroscopy to detect changes in DNA-encoded chain from patients for the early diagnoses of diseases. Their work, presented at the Baltimore CLEO conference this past June, indicates that THz sensing of genes could have the potential to replace or at a minimum, complement traditional DNA sensing devices.
There is also new activity showing that this type of spectroscopy and imaging may be beneficial to drug companies and pharmacists. "There is work being done in scanning pills, says Mittleman, "where because of the ability of terahertz systems' to distinguish between different isomers in pills, generic and name brand versions could be easily picked out.
Fad or Mainstay
All of this activity seems to indicate that this region of the spectrum, and the instruments it has spawned, is providing viable alternatives to the well-known, IR, UV, and x-ray spectroscopies.
Both medical and military applications are just beginning to tap its benefits. "The THz regime has shown that it can be extremely useful in identifying different biological samples by their unique absorption features in the 0.1-10 THz range," says researcher Hakan Altan, NJIT/Rutgers, Newark. "Moreover, because the atmosphere is fairly transparent below 0.3 THz, THz spectroscopy can be used for remote bio-agent detection," a property currently being studied.
