PDMS Microlenses for Focusing Light in Narrow Band Imaging Diagnostics.

Adriana C Costa,Tao Dong,João F Ribeiro,Manuel F Silva,Sara Pimenta,Reinoud F Wolffenbuttel,Zhaochu Yang,José H Correia

doi:10.3390/s19051057

Abstract

Minimally invasive medical devices can greatly benefit from Narrow Band Imaging (NBI) diagnostic capabilities, as different wavelengths allow penetration of distinct layers of the gastrointestinal tract mucosa, improving diagnostic accuracy and targeting different pathologies. An important performance parameter is the light intensity at a given power consumption of the medical device. A method to increase the illumination intensity in the NBI diagnostic technique was developed and applied to minimally invasive medical devices (e.g., endoscopic capsules), without increasing the size and power consumption of such instruments. Endoscopic capsules are generally equipped with light-emitting diodes (LEDs) operating in the RGB (red, green, and blue) visible light spectrum. A polydimethylsiloxane (PDMS) µ-lens was designed for a maximum light intensity at the target area of interest when placed on top of the LEDs. The PDMS µ-lens was fabricated using a low-cost hanging droplet method. Experiments reveal an increased illumination intensity by a factor of 1.21 for both the blue and green LEDs and 1.18 for the red LED. These promising results can increase the resolution of NBI in endoscopic capsules, which can contribute to early gastric lesions diagnosis.

Highlights

Narrow Band Imaging (NBI) is an endoscopic diagnostic technique that uses narrow band filters at red, green, and blue (RGB) wavelengths [1,2]
The μ-lens will be used on top of RGB light-emitting diodes (LEDs) dedicated to NBI technique
Without increasing the power consumption or the dimensions of a medical device, the solution presented here can be applied on gastrointestinal noninvasive platforms, such as an endoscopic capsule with NBI diagnostic capabilities

Summary

Introduction

Narrow Band Imaging (NBI) is an endoscopic diagnostic technique that uses narrow band filters at red, green, and blue (RGB) wavelengths [1,2]. The NBI technique presents a diagnosis improvement over the common white light, because the use of three wavelengths allows the capturing of images at different tissue depths. The blue light (at 415 nm) reproduces superficial images of the mucosa and capillaries, and corresponds to the main absorption peak of hemoglobin, which provides a good contrast of small vessels. The green light (at 540 nm) allows a deeper penetration into the tissue compared to blue light, and provides an intermediate image. The red light (at 600 nm) allows the deepest penetration, corresponding to the imaging of deeper vessels and allowing the analysis of Sensors 2019, 19, 1057; doi:10.3390/s19051057 www.mdpi.com/journal/sensors. The light penetration range into the tissue varies from 0.15 to 0.30 mm with the NBI technique [2]

Methods

Results

Conclusion