skip to main content


This content will become publicly available on September 13, 2024

Title: Efficient algorithm to calculate the optical properties of breast tumors by high-order perturbation theory

An efficient algorithm to obtain the solutions forn-th order terms of perturbation expansions in absorption, scattering, and cross-coupling for light propagating in human tissue is presented. The proposed solution is free of any approximations and makes possible fast and efficient estimates of mammographic, optical tomographic, and fluorescent images, applying a perturbation order of 30 and more. The presented analysis sets the general limits for the applicability of the perturbation approach as a function of tumor size and optical properties of the human tissue. The convergence tests of the efficient calculations for large absorbing objects show excellent agreement with the reference data from finite element method calculations. The applicability of the theory is demonstrated in experiments on breast-like phantoms with high absorbing and low-scattering lesions.

 
more » « less
NSF-PAR ID:
10462474
Author(s) / Creator(s):
; ;
Publisher / Repository:
Optical Society of America
Date Published:
Journal Name:
Journal of the Optical Society of America A
Volume:
40
Issue:
10
ISSN:
1084-7529; JOAOD6
Page Range / eLocation ID:
Article No. 1882
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Abstract

    Electron-phonon (e–ph) interactions are usually treated in the lowest order of perturbation theory. Here we derive next-to-leading ordere–ph interactions, and compute from first principles the associated electron-two-phonon (2ph) scattering rates. The derivations involve Matsubara sums of two-loop Feynman diagrams, and the numerical calculations are challenging as they involve Brillouin zone integrals over two crystal momenta and depend critically on the intermediate state lifetimes. Using Monte Carlo integration together with a self-consistent update of the intermediate state lifetimes, we compute and converge the 2ph scattering rates, and analyze their energy and temperature dependence. We apply our method to GaAs, a weakly polar semiconductor with dominant optical-mode long-rangee–ph interactions. We find that the 2ph scattering rates are as large as nearly half the value of the one-phonon rates, and that including the 2ph processes is necessary to accurately predict the electron mobility in GaAs from first principles.

     
    more » « less
  2. Perturbation Monte Carlo (pMC) has been previously proposed to rapidly recompute optical measurements when small perturbations of optical properties are considered, but it was largely restricted to changes associated with prior tissue segments or regions-of-interest. In this work, we expand pMC to compute spatially and temporally resolved sensitivity profiles, i.e. the Jacobians, for diffuse optical tomography (DOT) applications. By recording the pseudo random number generator (PRNG) seeds of each detected photon, we are able to “replay” all detected photons to directly create the 3D sensitivity profiles for both absorption and scattering coefficients. We validate the replay-based Jacobians against the traditional adjoint Monte Carlo (aMC) method, and demonstrate the feasibility of using this approach for efficient 3D image reconstructions usingin vitrohyperspectral wide-field DOT measurements. The strengths and limitations of the replay approach regarding its computational efficiency and accuracy are discussed, in comparison with aMC, for point-detector systems as well as wide-field pattern-based and hyperspectral imaging systems. The replay approach has been implemented in both of our open-source MC simulators - MCX and MMC (http://mcx.space)

     
    more » « less
  3. When viewed under coherent illumination, scattering materials such as tissue exhibit highly varying speckle patterns. Despite their noise-like appearance, the temporal and spatial variations of these speckles, resulting from internal tissue dynamics and/or external perturbation of the illumination, carry strong statistical information that is highly valuable for tissue analysis. The full practical applicability of these statistics is still hindered by the difficulty of simulating the speckles and their statistics. This paper proposes an efficient Monte Carlo framework that can efficiently sample physically correct speckles and estimate their covariances. While Monte Carlo algorithms were originally derived for incoherent illumination, our approach simulates complex-valued speckle fields. We compare the statistics of our speckle fields against those produced by an exact numerical wave solver and show a precise agreement, while our simulator is a few orders of magnitude faster and scales to much larger scenes. We also show that the simulator predictions accurately align with existing analytical models and simulation strategies, which currently address various partial settings of the general problem.

     
    more » « less
  4. In vivophotoacoustic (PA) flow cytometry (PAFC) has great clinical potential for early, noninvasive diagnosis of cancer, infections (e.g., malaria and bacteremia), sickle anemia, and cardiovascular disorders, including stroke prevention through detection of circulating white clots with negative PA contrast. For clinical applications, this diagnostic platform still requires optimization and calibration. We have already demonstrated that this need can be partially addressed byin vivoexamination of large mouse blood vessels, which are similar to human vessels used. Here, we present an alternative method for PAFC optimization that utilizes novel, clinically relevant phantoms resembling pigmented skin, tissue, vessels, and flowing blood. This phantom consists of a scattering-absorbing medium with a melanin layer and plastic tube with flowing beads to model light-absorbing red blood cells (RBCs) and circulating tumor cells (CTCs), as well as transparent beads to model white blood cells and clots. Using a laser diode, we demonstrated the extraordinary ability of PAFC to dynamically detect fast-moving mimic CTCs with positive PA contrast and white clots with negative PA contrast in an RBC background. Time-resolved detection of the delayed PA signals from blood vessels demonstrated complete suppression of the PA background from the modeled pigmented skin. This novel, medically relevant, dynamic blood flow phantom can be used to calibrate and maintain PAFC parameters for routine clinical applications.

     
    more » « less
  5. Professor Gregory Hartland (Ed.)
    An improved optical design for nanosecond diffuse reflectance (DR) spectroscopy is presented. The in-situ analysis of the electron back-reaction and dye regeneration processes in efficient opaque dye-sensitized solar cell devices (DSCs) was scrutinized for the first time using nanosecond DR spectroscopy. The efficient DSC device is based on an opaque TiO2 double-layer film comprising 400 nm light-scattering particles and 20 nm optically transparent particles. Transmission-based laser techniques are not suitable for studying these or other devices by using the opaque morphologies of TiO2 films. However, time-resolved DR flash photolysis enables the exploration of photophysical processes in a broad variety of opaque or highly light-absorbing and light-scattering materials. We experimentally verified the three important components of DR-based spectroscopy: optical configuration, sample condition, and theoretical quantitative optical models. The large optical angle for diffusive light enables efficient light collection and measurement at a relatively low power. We tested the steady-state and time-resolved concentration dependence of the Kubelka−Munk theory for the quantitative analysis of time-resolved results and observed that the dynamics of electron back-reactions are strongly affected by the morphological parameters of the TiO2 films. With a lifetime of 50 μs, the kinetics of electron back-recombination in the device’s photoanode, which is manufactured with 400 nm TiO2 particles and 20 nm TiO2 particles, are 2 orders of magnitude faster than what has been reported to date for 20 nm particles (1 ms). In contrast to electron back-recombination, the dye regeneration process is not influenced by the TiO2 film morphology. 
    more » « less