Hyperspectral rigid-scope set to assist imaging of tissues, blood vessels, nerves

01 May 2024

Industrial applications should also benefit from Tokyo University of Science near-infrared platform.

A team at Tokyo University of Science (TUS) has developed a rigid endoscope system cable of carrying out hyperspectral imaging (HSI) over wavelengths ranging from visible to more than 1000 nanometers.

The device, described in Optics Express and said to be the first such rigid-scope system, could bring HSI to applications for which existing platforms have been too cumbersome or inconvenient.

HSI has become a valuable technique in some medical and industrial situations, from assisting clinicians in determining the margins of tumors to monitoring environmental and atmospheric conditions from orbit. The practicalities of the HSI imaging platforms themselves has kept the technique from being widely utilized in some general scenarios, however.

"Various types of HSI device have been developed to suit different imaging targets and situations, such as for imaging under a microscope or portable imaging and imaging in confined spaces," commented the TUS team.

"However, for over-thousand-nanometer wavelengths ordinary visible cameras lose sensitivity and only a few commercially available lenses exist that can correct chromatic aberration. Moreover it is necessary to construct cameras, optical systems and illumination systems for portable near-IR HSI devices, but no device that can acquire NIR-HSI with a rigid scope, crucial for portability, has been reported."

The TUS breakthrough is built around a supercontinuum (SC) light source and an acoustic-opto tunable filter (AOTF). A SC light source can output intense coherent white light, while the AOTF can extract light containing a specific wavelength.

This combination offers easy light transmission to the light guide and the ability to electrically switch between a broad range of wavelengths within a millisecond, according to the researchers.

Identify cancer and improve surgical navigation

The project's customized rigid scope device was designed to perform HSI in the range of 490 to 1600 nanometers, enabling visible as well as NIR-HSI, and in trials was used to acquire the spectra of six types of colored resins including fiber-reinforced plastic, nylon and polycarbonate.

A neural network was then applied to the data, classifying the spectra pixel-by-pixel in multiple wavelengths. Results showed that the platform could classify seven different targets, the six resins and a white reference, with an accuracy and specificity both above 99 percent. This means that the system can successfully extract molecular vibration information of each resin at each pixel, noted the project.

Having demonstrated that HSI from its portable rigid-scope platform is feasible, TUS will now work on enhancing image quality, refining the design of the rigid endoscope, and tackling chromatic aberrations. The team predicts that its HSI technology can then facilitate new applications in industrial inspection and quality control, as well as enhance specific clinical imaging applications.

"This breakthrough enables the identification of invaded cancer areas and the visualization of deep tissues such as blood vessels, nerves, and ureters during medical procedures, leading to improved surgical navigation," commented Hiroshi Takemura from TUS.

"Additionally it enables measurement using light previously unseen in industrial applications, potentially creating new areas of non-destructive testing."