Resolution improvement using enriched Krylov subspace for microwave tomography breast imaging system

摘要

In this work, a resolution improvement strategy has been presented for microwavetomography imaging in the dense and heterogeneous breasts. Whileimproving the spatial resolution by reducing the size of pixels, the resultantimage will be affected by spatial oscillation, and it will also lack to differentiatethe dielectric values of low contrast tissue regions which are the unavoidableproblems in the microwave tomography dense breast imaging. These difficultiesare addressed as discrete ill-posed and ill-condition problems. In thispaper, Enriched Conjugate Gradient Least Square (ECGLS) regularizationmethod has been proposed and it is associated with the Distorted Born IterativeMethod (DBIM) to improve the quality of high-resolution images of heterogeneousand dense type breasts. The Proposed-ECGLS (PECGLS) methodintroduces the span of enriched subspace with external penalization value toresolve the discrete ill-posed problem. The Gram-Schmidt factorization (or QRfactorization) based step length and the external penalization value control thespatial oscillations and resolve the ill-condition problem with quick convergence.The performance of the Proposed-ECGLS method has been tested onheterogeneous and dense breast phantoms for synthetically embedded malignantalong with differences in permittivity value of +8% to +10% in the fibroglandtissues. The results from the simulation studies depict that the Proposed-ECGLS has achieved up to 0.8276 of structural similarity in different level discretizationerror and it is better than the existing methods such as ECGLS andstandard CGLS. This high-resolution microwave tomography imaging methodwill be helpful in malignant detection and fibroadenoma diagnosis in densetype breasts.