The role of late photons in diffuse optical imaging

TL;DR

This paper demonstrates that late, highly diffuse photons contain valuable information for improving image reconstruction in diffuse optical imaging, especially in thick scattering media, highlighting the importance of time-resolved techniques.

Contribution

It reveals that late photons can significantly enhance image quality and alone can produce comparable images to early photons, emphasizing the role of fully time-resolved imaging in highly scattering tissues.

Findings

Late photons improve image reconstruction quality in thick media.

Late photons alone can produce images comparable to early photon data.

Time-resolved imaging is crucial in highly diffusive regimes.

Abstract

The ability to image through turbid media such as organic tissues, is a highly attractive prospect for biological and medical imaging. This is challenging however, due to the highly scattering properties of tissues which scramble the image information. The earliest photons that arrive at the detector are often associated with ballistic transmission, whilst the later photons are associated with complex paths due to multiple independent scattering events and are therefore typically considered to be detrimental to the final image formation process. In this work we report on the importance of these highly diffuse, "late" photons for computational time-of-flight diffuse optical imaging. In thick scattering materials, >80 transport mean free paths, we provide evidence that including late photons in the inverse retrieval enhances the image reconstruction quality. We also show that the late photons alone have sufficient information to retrieve images of a similar quality to early photon gated data. This result emphasises the importance in the strongly diffusive regime discussed here, of fully time-resolved imaging techniques.