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  • Diffractive Catheter Enhances OCT Imaging

Photonics.com
Mar 2014
BALTIMORE and SEATTLE, March 12, 2014 — A new imaging catheter that enables real-time, ultrahigh-resolution OCT imaging at 800 nm to form a 3-D volumetric dataset could potentially improve image contrast via increased light scattering and less tissue absorption.

Called a diffractive catheter, the device was developed by researchers from Johns Hopkins University and the University of Washington. Currently, such catheters and endoscopes are designed to work at around 1300 nm, but a smaller wavelength is more convenient in achieving an ultrahigh-axial resolution with a broadband light source.


Reflected spectra of the imaging catheters with and without a diffractive lens. Images courtesy of Optics Letters.

The instrument features a diffractive microlens to manage chromatic aberration. Because it was originally designed for longer wavelengths, it can only alleviate the aberration rather than remove it. With further investigation and optimization of the diffractive lens, better image quality can be accomplished.

In the current study, a fiber rotary joint coupled with a broadband Ti:sapphire laser brought the imaging catheter’s lateral resolution to 6.2 µm and the axial resolution to 3µm. This allowed for 3-D full-circumferential endoscopic OCT imaging, something previously not possible with traditional setups.

The instrument’s 3-D capabilities were tested using in vivo imaging.


Schematic of an ultrahigh-resolution OCT imaging catheter with a diffractive lens to alleviate chromatic aberration.

Fine structures, such as a thin layer of muscularis mucosae embedded between lamina propria and submucosa (muscles that are part of the gastrointestinal tract), were easily identified. Such structures have historically been difficult to distinguish in the 1300-nm wavelength.

The research was funded by a National Institutes of Health grant and will be published in Optics Letters.

For more information, visit: www.opticsinfobase.org.


GLOSSARY
broadband
Indicating a capability to deal with a relatively wide spectral bandwidth.
chromatic aberration
The lens aberration resulting from the normal increase in refractive index of all common materials toward the blue end of the spectrum. The change in image size from one color to another is known as lateral color or chromatic difference of magnification.
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