- A new form of endoscopic imaging catheters, named nano optic endoscopes are far efficient than existing catheters.
- They could be used in any complex medium to obtain high-quality focusing and detect diseases, including cancer.
Diagnosing internal organ diseases mostly relies on biopsy samples taken from infected areas. However, the existing endoscopic imaging methods cannot precisely image the affected sites, making it very difficult to collect samples without any errors.
Endoscopic optical imaging based on fiber optic catheters has provided several opportunities to obtain data from hard-to-reach sites. For instance, endoscopic optical coherence tomography (OCT) can extract detailed images of microstructure deep into the tissue. It can effectively monitor diseases in hard-to-reach areas such as pulmonary airways and gastrointestinal tract.
But since this technique is associated with numerous shortcomings (like lack of required penetration depth and necessary field of view) it hasn’t been translated into daily clinical practice in various applications.
Now, researchers at Harvard University and Massachusetts General Hospital have developed a new form of endoscopic imaging catheters, called nano optic endoscopes that is far efficient (in terms of detecting diseases) than existing techniques.
How Did They Develop This?
The nano optic endoscopes catheters are integrated with metalenses that contain arrays of subwavelength-spaced scatterers at the interface. These optical scatterers locally shift the incident light phase and restructure its wavefront according to their geometric parameters and distribution.
This enables metalenses to be free of astigmatism and spherical aberration. The methodology could be used in any complex medium to obtain high-quality focusing. The best thing is it doesn’t require any additional acquisition, processing time, and complicated arrangements of optical equipment.
The end of the nano-optic endoscope | Credit: Harvard University
Technically, the metalens’ chromatic dispersion in the context of spectral interferometry enables resolution beyond the Rayleigh range of the incident light. They compared their technology with a ball lens catheter and a commercial GRIN lens catheter to highlight the output beam quality.
Reference: Nature | doi:10.1038/s41566-018-0224-2 | Harvard University
To demonstrate the imaging quality, they captured fruit flesh, swine airways and human lung tissue with nano optic endoscope. The results were quite impressive: the instrument can see deep into tissue with remarkably higher resolution than existing catheter designs.
The instrument clearly showed cellular structures in tissue layer and fruit flesh, and fine glands in the swine’s bronchial mucosa. In the human lung tissue, it clearly identified structures corresponding to irregular, fine glands, suggesting one of the most prominent kinds of cancerous tumor, adenocarcinoma.
Images of fruit flesh (left) and swine airways (right) captured by a traditional catheter (a,c) and nano optic endoscope (b,d) | Credit: Harvard University
In the coming years, researchers will explore other application of this technology, for example, nano-optic endoscopy sensitive to polarization, which can enable optical axis determination with no ambiguity. This would contrast between highly-organized structural tissues, like smooth muscle and blood vessels.
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Further improvements of imaging depth of focus via light sources with larger bandwidths and manipulation of metalens chromatic dispersion is another crucial aspect. The special characteristics of nano optic endoscopes could also be useful for other endoscopic optical techniques like confocal endomicroscopy for enhanced capabilities.
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