The diagnosis of diseases based in internal organs often relies on biopsy samples collected from affected regions. But collecting such samples is highly error-prone due to the inability of current endoscopic imaging techniques to accurately visualize sites of disease. The conventional optical elements in catheters used to access hard-to-reach areas of the body, such as the gastrointestinal tract and pulmonary airways, are prone to aberrations that obstruct the full capabilities of optical imaging.
Now, experts in endoscopic imaging at Massachusetts General Hospital (MGH) and at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), have teamed up to develop a new class of endoscopic imaging catheters — termed nano-optic endoscopes — that overcome the limitations of current systems. The problem addressed by the researchers is that clinical adoption of many cutting-edge endoscopic microscopy modalities has been hampered due to the difficulty of designing miniature catheters that achieve the same image quality as bulky desktop microscopes. They believe that the use of nano-optic catheters that incorporate metalenses into their design will likely change the landscape of optical catheter design, resulting in a dramatic increase in the quality, resolution, and functionality of endoscopic microscopy. Metalenses based on flat optics are a game-changing new technology because the control of image distortions necessary for high resolution imaging is straightforward compared to conventional optics, which require multiple convex-shaped lenses.
To demonstrate the imaging quality of the nano-optic endoscope, the researchers imaged fruit flesh, swine and sheep airways, and human lung tissue. They showed that the nano-optic endoscope can image deep into the tissue with significantly higher resolution than provided by current imaging catheter designs. The images captured by the nano-optic endoscope clearly show cellular structures in fruit flesh and tissue layers and fine glands in the bronchial mucosa of swine and sheep. In the human lung tissue, the researchers were able to clearly identify structures that correspond to fine, irregular glands indicating the presence of adenocarcinoma, the most prominent type of lung cancer.
According to the researchers, the main advantage of the metalens is that it can be designed to tailor its specifications to overcome spherical aberrations and astigmatism and achieve very fine focus of the light without the need for complex optical components.
They next aim to explore other applications, including a polarization-sensitive nano-optic endoscope, which could contrast between tissues that have highly-organized structures, such as smooth muscle, collagen, and blood vessels.