Abstract
Terahertz-light imaging is attracting great attention as a new approach in non-invasive/non-staining biopsy of cancerous tissues. Positively, terahertz light has been shown to be sensitive to the cell density, the hydration content, and the chemical composition of biological samples. However, the spatial resolution of terahertz imaging is typically limited to several millimeters, making it difficult to apply the technology to image biological tissues which have sub-terahertz-wavelength-scale inhomogeneity. For overcoming the resolution, we have recently developed a terahertz near-field microscope with a spatial resolution of 10 µm, named scanning point terahertz source (SPoTS) microscope. In contrast to conventional far-field terahertz techniques, this microscope features the near-field interactions between samples and point terahertz sources on a sub-terahertz-wavelength scale. Herein, to evaluate the usefulness of terahertz imaging in cancer tissue biopsy in greater detail, we performed terahertz near-field imaging of a paraffin-embedded human-breast-cancer section having sub-terahertz-wavelength-scale inhomogeneity of the cancer cell density using the SPoTS microscope. The observed terahertz images successfully visualized local (~250 µm) inhomogeneities of the cell density in breast invasive ductal carcinoma. These results may bypass the terahertz limitation in terms of spatial resolution and may further motivate the application of terahertz light to cancer tissue biopsy.
Highlights
In recent years, there has been a significant increase in the number of cancers worldwide; the number of new cancer cases worldwide is predicted to reach 21.6 million by 2030 [1]
To evaluate the usefulness of terahertz microscopic imaging for cancer tissue biopsy in greater detail, we demonstrated the visualization of subwavelength-scale inhomogeneity of cancer cell densities in a single type of human cancer lesion using the scanning point terahertz source (SPoTS) microscope
The APVs corresponding to the ductal carcinoma in situ (DCIS), invasive ductal carcinoma (IDC) (1-3), and fibrous regions in the reflection image are presented in Figure 4i, as well as their SDs
Summary
There has been a significant increase in the number of cancers worldwide; the number of new cancer cases worldwide is predicted to reach 21.6 million by 2030 [1]. Terahertz imaging can visualize morphological, physiological, and some-molecular-complex information of biological tissues [10] These advantages may make it possible to detect various cancer lesions, accurately, rapidly, quantitatively, and non-invasively without stain process required in conventional optical imaging [11,12,13,14,15,16]. It is found that the micrometric (several hundred microns) inhomogeneity of the cancer cell densities can be visualized in the terahertz images in both transmission and reflection modes This outcome may break through the limitation of terahertz imaging in terms of the spatial resolution and may open up the possibility of the terahertz technology for cancer tissue biopsy
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