Reconstructive tomography with diffracting wavefieldst
نویسنده
چکیده
A unified theoretical framework based on the scalar wave equation is presented for transmission tomography of weakly inhomogeneous objects embedded in a known uniform background medium. The developed formulation differs from the usual treatments of diffraction tomography in that it is not limited to applications employing plane-wave illumination and planar measurement boundaries and can be extended to weakly inhomogeneous objects embedded in non-uniform backgrounds and to the class of strongly scattering objects. The new formulation is based on the mathematical operations of propagation and backpropagation which are generalisations of the conventional tomographic operations of projection and backprojection to the case of diffracting wavefields. The projection and hackprojection operations are then obtained from the generalised operations in the zero wavelength limit. A class of reconstruction algorithms are developed within the new formulation that are generalisations, to the case of diffraction tomography, of the class of iterative ART (algebraic reconstruction technique) algorithms of conventional (x-ray) tomography. The reconstruction algorithms developed (called generalised ART algorithms) are shown to be applicable to situations where the tomographic data are sparse (limited-view problem) and to the incorporation of a priori information into the reconstruction process.
منابع مشابه
High contrast microwave tomography using topology optimization techniques
Microwave tomography for medical applications leads to a difficult reconstruction problem for the dielectric properties of biological tissue due to strongly diffracting waves in combination with large dielectric contrasts. We apply the material distribution technique used for topology optimization of elastic structures in order to solve the nonlinear least-squares problem underlying the reconst...
متن کاملTime reversal and its application to tomography with diffracting sources.
An exact time-domain method is proposed to time reverse a transient scalar wave using only the field measured on an arbitrary closed surface enclosing the initial source. Under certain conditions, a time-reversed field can be approximated by retransmitting the measured signals in a reversed temporal order. Exact reconstruction for three-dimensional broadband diffraction tomography (a linearized...
متن کاملNoise limits in the assembly of diffraction data
We obtain an information theoretic criterion for the feasibility of assembling diffraction signals from noisy tomographs when the positions of the tomographs within the signal are unknown. For shot-noise limited data, the minimum number of detected photons per tomograph for successful assembly is much smaller than previously believed necessary, growing only logarithmically with the number of re...
متن کاملQuantitative reconstructions in multi-modal photoacoustic and optical coherence tomography imaging
متن کامل
Chemical and enzymatic synthesis of tRNAs for high-throughput crystallization.
Preparation of large quantities of RNA molecules of a defined sequence is a prerequisite for biophysical analysis, and is particularly important to the determination of high-resolution structure by X-ray crystallography. We describe improved methods for the production of multimilligram quantities of homogeneous tRNAs, using a combination of chemical synthesis and enzymatic approaches. Transfer ...
متن کامل