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This paper proposes a unified shape and coefficient optimization approach for inverse problems governed by diffusion equations. The associated forward problem is considered with a Robin boundary condition, physically motivated in diffuse optical tomography to model partial reflection of light at tissue boundaries. The main objective is the recovery of the piecewise-defined absorption coefficient together with its underlying interface from a single boundary measurement. To this end, a shape-based reconstruction approach is formulated in which the interface is introduced as a geometric unknown governing the piecewise structure of the absorption coefficient. While classical approaches rely on the Fréchet derivative with respect to spatially varying parameters, the Eulerian derivative with respect to the interface is additionally exploited. This leads to a unified framework for the simultaneous recovery of the coefficient and the geometry under the single-measurement setting. Numerical experiments demonstrate the effectiveness of the proposed method, even for complex and non-convex interfaces.
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Figure 17. Results for a circular boundary interface with $ f $ (given by (38) with $ \epsilon = 0.5 $) of various positions and instances near the boundary and parameters $ (\mu_{0}^{\ast}, \mu_{1}^{\ast}) = (1, 1.2) $, under exact (first three columns from the left) and noisy measurements. No perimeter regularization was applied in any of the cases
Figure 20. Results for a peanut-shape boundary interface with source $ f $ (given by (38) with $ \epsilon = 0.2 $) near the boundary, under exact (top row) and noisy measurements. The locations of the point sources are marked by thick black dots. Perimeter penalization was applied in all of the cases with $ \rho_{1} = 0.00003 $
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A radial problem in 2D with
2D radial problem with source function
Results for a 2D radial problem with
Results for a 2D radial problem with
Results for a 2D radial problem with
An example featuring a non-circular boundary interface
An example featuring a non-circular boundary interface with noisy data
Results for a non-circular boundary interface with varying
An example featuring a non-circular boundary interface with noisy data
An example of a peanut-shaped boundary interface with noisy data
Effect of choice of initial guess
Reconstruction results for a non-circular interface with
Results for a smooth non-circular boundary interface with
Results for a smooth non-circular boundary interface with
Results for a square boundary interface
Results for an inverted
Results for a circular boundary interface with
Results for a peanut-shape boundary interface with source
Results for a peanut-shape boundary interface with source
Results for a peanut-shape boundary interface with source
Positioning of sources
Results for a peanut-shape boundary interface with