TITLE:
Method for Improving the Lateral Resolution of Near-Infrared (NIR) Single Optods: Application to Subcutaneous Vein Detection and Localization
AUTHORS:
Yasser S. Fawzy
KEYWORDS:
Reflectance Measurements; Photon Migration; Optical Diagnosis; Fiber Probe Design
JOURNAL NAME:
Optics and Photonics Journal,
Vol.2 No.4,
December
31,
2012
ABSTRACT: NIR backscattering measurements using single
source-detector optical probe (optods) can detect absorption areas within deep
tissue layer. However, such optods, are characterized by large separation
distance between the source and detectors (>2 cm) and poor lateral
resolution (>1 cm), which limits its usage for the localization
of small absorption volumes embedded deep within the tissue such as
subcutaneous veins. In this work a method to improve the accuracy of locating
such absorption volumes (areas) using backscattered NIR measurements is
suggested and investigated with the aim of developing an optical sensor for
detecting and localizing large subcutaneous veins. The method is based on
measuring the differential signal from three overlapping source-detector pairs
arranged within the probe such that the total photon sensitivity profile of the
probe is maximized along a narrow width area (within the central of the probe)
and minimized along its sides. The location of the absorption areas is then
determined when a peak maximum of the measured signal is detected. Monte Carlo
simulation and light transport modeling was used to determine the optimum
arrangement of each source-detector pair within the probe to create the
required spatial sensitivity profile and demonstrate the validity of the
method. The results showed that the differential optode has more than two times
improvement in the lateral resolution compared to the standard optode. The
result also showed that the differential probe can locate subcutaneous veins
with diameter ~5 mm and embedded at ~1.5 cm depth. The method could have a potential for
designing and developing an optical backscattering sensors for detecting and
localizing large subcutaneous veins embedded 2 cm depths