TY  - INPR
A1  - Dicken, Volker
T1  - Simultaneous activity and attenuation reconstruction in emission tomography
N2  - In single photon emission computed tomography (SPECT) one is interested in reconstructing the activity distribution f of some radiopharmaceutical. The data gathered suffer from attenuation due to the tissue density µ. Each imaged slice incorporates noisy sample values of the nonlinear attenuated Radon transform (formular at this place in the original abstract) Traditional theory for SPECT reconstruction treats µ as a known parameter. In practical applications, however, µ is not known, but either crudely estimated, determined in costly additional measurements or plainly neglected. We demonstrate that an approximation of both f and µ from SPECT data alone is feasible, leading to quantitatively more accurate SPECT images. The result is based on nonlinear Tikhonov regularization techniques for parameter estimation problems in differential equations combined with Gauss-Newton-CG minimization.
T3  - NLD Preprints - 50 
KW  - SPECT
KW  - tomogrphy
KW  - attenuated Radon transform
KW  - nonlinear invers problem
KW  - Tikhonov regularization
KW  - nonlinear optimization
Y1  - 1998
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-14747
ER  - 
TY  - INPR
A1  - Dicken, Volker
A1  - Maaß, Peter
T1  - Wavelet-Galerkin methods for ill-posed problems
N2  - Projection methods based on wavelet functions combine optimal convergence rates with algorithmic efficiency. The proofs in this paper utilize the approximation properties of wavelets and results from the general theory of regularization methods. Moreover, adaptive strategies can be incorporated still leading to optimal convergence rates for the resulting algorithms. The so-called wavelet-vaguelette decompositions enable the realization of especially fast algorithms for certain operators.
T3  - NLD Preprints - 22 
Y1  - 1995
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-13890
ER  -