Diffuse optical tomography (DOT) has been employed to derive spatial maps of physiologically important chromophores in the human breast, but the fidelity of these images is often compromised by boundary effects such as those due to the chest wall. We explore the image quality in fast, data-intensive analytic and algebraic linear DOT reconstructions of phantoms with subcentimeter target features and large absorptive regions mimicking the chest wall. Experiments demonstrate that the chest wall phantom can introduce severe image artifacts. We then show how these artifacts can be mitigated by exclusion of data affected by the chest wall. We also introduce and demonstrate a linear algebraic reconstruction method well suited for very large data sets in the presence of a chest wall.
We discuss image reconstruction algorithms for diffuse optical tomography that allow utilization of extremely large data sets. Image reconstruction is performed with experimental data obtained with the use of a CCD camera-based noncontact imager. We demonstrate that more than 107 measurements can be acquired and utilized. This is two orders of magintude or more larger than the data sets which are typically used in diffuse optical imaging.
We introduce a set of corrections to the integral equations of scattering theory within the diffusion approximation to the radiative transport equation. We use this result to obtain an image reconstruction algorithm for optical tomography with spatial resolution below the transport mean free path.
We consider the inverse scattering problem for the diffusion equation with general boundary conditions. Computer simulations are used to illustrate our approach in model systems.
KEYWORDS: Near field, Inverse scattering, Scattering, Image resolution, 3D image processing, Signal to noise ratio, Microscopy, Inverse scattering problem, Near field optics, Spatial resolution
In classical microscopy and inverse scattering, images are made from far field measurements. It will be shown that the standard Abbe or Rayleigh resolution limits arise as a result of assumptions which do not hold in the near field. Existing technologies such as TIRM and PSTM that exploit these properties of the near field produce two dimensional images which exhibit structure on a subwavelength scale. These images have proven difficult to interpret when the sample presents variations in structure and optical properties simultaneously in three dimensions. We present the analytic singular value decomposition of the linearized scattering operator. This representation leads to a robust inversion algorithm for the inverse scattering problem in the near zone. Numerical implementation of the algorithm is demonstrated using simulated noisy data to produce tomographic images of a three dimensional scatterer.
We consider the scattering and inverse-scattering of scalar waves in the near field. By exploiting the similarity to the corresponding problems for diffusing waves, an analytic solution to the near-field inverse scattering problem is obtained. Applications to near-field microscopy are described.
We consider the problem of emission tomography in a highly- scattering medium probed by diffusing waves. Experimental validation of an algorithm that gives a direct solution to the image reconstruction problem is reported.
We consider the problem of imaging the optical absorption of a highly-scatering medium probed by diffusive light. An analytic solution to the image reconstruction problem is presented.
We discuss algorithms for solving the image reconstruction problem in photon diffusion imaging. Experimental verification including an absorption image of a bovine brain at one centimeter resolution is provided.
We consider the problem of imaging the optical absorption of a highly-scattering medium probed by diffusing waves. We present a path integral formulation of this inverse scattering problem that is used to obtain explicit inversion formulas for diffusion imaging.
Pulse propagation is measured in a highly scattering medium and the photon mean free path is measured for different densities of scatterers. We analyze the effect of detector orientation relative to the light source, which is a probe of the anisotropy of the photon current. We compare pulse transmission in an effectively infinite geometry to pulse transmission in a backscattering experiment. We determine the boundary condition at the interface between the scattering medium and the free medium. This consists of linear combinations of absorbing and reflecting conditions.
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