Reconstruction of Optical Vector-Fields With Applications in Endoscopic Imaging.

Milana Gataric,Maria P Alcolea,Alberto Gil C P Ramos,Sarah E Bohndiek,George S D Gordon,Francesco Renna

doi:10.1109/tmi.2018.2875875

Abstract

We introduce a framework for the reconstruction of the amplitude, phase, and polarization of an optical vector-field using measurements acquired by an imaging device characterized by an integral transform with an unknown spatially variant kernel. By incorporating effective regularization terms, this new approach is able to recover an optical vector-field with respect to an arbitrary representation system, which may be different from the one used for device calibration. In particular, it enables the recovery of an optical vector-field with respect to a Fourier basis, which is shown to yield indicative features of increased scattering associated with tissue abnormalities. We demonstrate the effectiveness of our approach using synthetic holographic images and biological tissue samples in an experimental setting, where the measurements of an optical vector-field are acquired by a multicore fiber endoscope, and observe that indeed the recovered Fourier coefficients are useful in distinguishing healthy tissues from tumors in early stages of oesophageal cancer.

Highlights

There has been a significant interest in developing new types of optical fibre endoscopes for medical imaging applications [15, 25, 36, 11, 7]
We investigate the following questions: (i) is there a useful representation of the full optical field reflected from a tissue that can be used for detecting optical aberrations associated with early cancer, and (ii) how can such a representation be recovered by an efficient and reliable algorithm from raw endoscopic measurements, namely from the calibration measurements and the samples of the output optical field?
Having established the utility of Fourier coefficients in quantifying phase scattering using simulated data in Section 3, we apply the reconstruction framework developed in Section 2 to measurements obtained experimentally using the prototype fibre endoscope developed in [21], which can measure optical phase, polarisation and amplitude

Summary

Introduction

There has been a significant interest in developing new types of optical fibre endoscopes for medical imaging applications [15, 25, 36, 11, 7] These new endoscopes aim to be thinner, and less invasive, and/or use different properties of light than conventional white light endoscopes making them more sensitive for detecting diseases such as cancer [41]. Phase is highly sensitive to surface scattering that arises due to microstructural tissue changes in early cancer, creating distorted reflected wavefronts [20, 37, 38, 34]. There are no commercial phase and polarisation endoscopes but a number of prototype devices have been demonstrated [32, 15, 27, 36, 40]

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Conclusion