Terahertz Waves Image Breast Cancer

A team of researchers at Osaka University, in colla­boration with the University of Bordeaux and the Bergonié Institute in France, has succeeded in terahertz imaging of early-stage breast cancer less than 0.5 mm without staining, which is difficult to identify even by patho­logical diagnosis. Their work provides a breakthrough towards rapid and precise on-site diagnosis of various types of cancer and acce­lerates the development of inno­vative terahertz diagnostic devices.

A schematic drawing of the measurement of breast cancer tissue fabricated on a nonlinear optical crystal. (Source: Osaka U.)

Breast cancer is roughly divided into two types: invasive and non-invasive. The former, invasive ductal carcinoma (IDC), begins in the cells of a breast duct, growing through the duct walls and into the surrounding breast tissue, potentially spreading to other parts of the body. The latter, ductal carcinoma in situ (DCIS), is an early-stage small breast cancer confined to the breast duct, but it can lead to invasive cancer. Therefore, early detection of DCIS is crucial. For patho­logical diagnosis of cancer, the tissue sample is chemi­cally stained, and a pathologist makes a diagnosis using an image of the stained tissue. However, the staining process takes time, and it is difficult to distin­guish DCIS from malignant IDC as they look nearly identical.

Terahertz imaging can distinguish cancer tissue from normal tissue without staining and radiation exposure. However, it was still difficult to identify an indi­vidual DCIS lesion (which typically range from 50 to 500 μm) by terahertz imaging due to its dif­fraction-limited spatial resolution of just several millimeters. “To overcome this drawback, we developed a unique imaging technique in which terahertz light sources that are locally generated at irra­diation spots of laser beams in a nonlinear optical crystal directly interact with a breast cancer tissue sample. Consequently, we succeeded in clearly visualizing a DCIS lesion of less than 0.5 mm,” explains Kosuke Okada. The accuracy of this technique is approxi­mately 1000 times higher than that of conventional techniques using terahertz waves.

The researchers also found that terahertz intensity distri­butions were different between DCIS and IDC, suggesting the possibility of quanti­tative deter­mination of cancer malignancy. The breast cancer tissue sample was provided and histo­logically assessed by collaborators from the University of Bordeaux and the Bergonié Institute. “One of the challenges in this research is preparing a high-quality breast cancer tissue sample fabricated on a nonlinear optical crystal. It is one of the great achieve­ments of inter­national joint research,” says Masayoshi Tonouchi. “Combining our technique with machine learning will aid in the early detection of cancer and deter­mination of cancer malig­nancy, as well as development of inno­vative terahertz diagnostic devices using Micro Electro Mechanical Systems.” (Source: Osaka U.)

Reference: K. Okada et al.: Terahertz near-field microscopy of ductal carcinoma in situ(DCIS) of the breast, J. Phys. Phot. 2, 044008 (2020); DOI: 10.1088/2515-7647/abbcda

Link: Institute of Laser Engineering, Osaka University, Osaka, Japan

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