Imaging in the highly diffusive regime lies at the heart of various optical medical imaging technologies and other applications such as imaging through fog. However, due to the randomization of the photon propagation direction inside random, complex media, the spatial information of physiological features is degraded such that most diffuse optical imaging techniques are restricted to $<10$ transport mean free paths $\left({\ell }^{*}\right)$. We present an information theoretical analysis of the limits of gathering information in the highly diffusive regime. Our results show that there is still information even when detection is performed at the single-photon level and beyond $200{\ell }^{*}$ (e.g., $\sim 12$ cm tissue). Image reconstructions are enhanced when resolving measurements in both space and time domains. These results provide a general framework for extremely deep diffuse imaging scenarios, such as imaging through the body, and a general context for developing optimized image retrieval strategies.

• Received 27 October 2022
• Accepted 22 December 2022

DOI:https://doi.org/10.1103/PhysRevResearch.5.L022008

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Published by the American Physical Society