University of Exeter researchers have developed a new terahertz imaging approach that can acquire micron-scale resolution images while retaining computational approaches designed to speed up image acquisition. This combination, which was reported recently in the journal Optica, could allow terahertz imaging to be useful for detecting early-stage skin cancer without requiring a tissue biopsy from the patient.
Terahertz wavelengths fall between microwaves and infrared light on the electromagnetic spectrum. Light in this region is ideal for biological applications because, unlike x-rays, it doesn't carry enough energy to harm tissue. Other research has shown that skin cancer cells absorb terahertz light more strongly than healthy cells, demonstrating that terahertz imaging can be useful for distinguishing between cancerous and healthy tissue.
"Ideally, we want to detect cancer early, when it is still small. We hope that high-resolution terahertz images, combined with the ability to take an image quickly, could eventually lead to a device that could detect cancer in the doctor's office," University of Exeter research team leader Rayko Stantchev noted. This is the first experimental demonstration, for any spectral region, showing that compressed sensing and adaptive imaging can be performed at resolutions much smaller than the wavelength of light used for imaging.
Stantchev is now working with researchers in the Chinese University of Hong Kong who have created a different optical setup to see if this approach might make it possible to acquire subwavelength terahertz images using a $200 laser instead of the almost $400,000 laser used for the work reported in the Optica paper.
Image: To enable high-resolution terahertz imaging, the researchers used a digital micromirror device to project laser light onto a silicon wafer in a specific pattern. When a terahertz beam passes through the wafer, a computer can reconstruct an image of the object based on the pattern of terahertz light detected. The inset shows an optical image of the test target (gold pinwheel) on a 6-mm thick silicon wafer. Image courtesy of Rayko Stantchev, University of Exeter.