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Adaptively altering hyper-parameter for Improved Reconstruction in PET

Mondal, PP and Rajan, K and Patnaik, LM (2003) Adaptively altering hyper-parameter for Improved Reconstruction in PET. In: 2003 IEEE Nuclear Science Symposium Conference Record, 19-25 October, Oregon,USA, Vol.5, 3460 -3463.


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It is well known that as the iterations of the maximum likelihood algorithm are continued, density estimates become more and more noisy. In situations where some prior knowledge about the object distribution is available, one may utilize such information in the reconstruction procedure for improving the reconstruction. Fixed prior based image reconstruction process produces over-smooth reconstruction due to the penalizing nature of the potential. As the reconstruction process builds up, image properties like smoothness, frequency content etc., change and hence fixed prior based image reconstruction process may not serve the purpose. A new prior is proposed which is capable of producing improved reconstruction over those obtained by existing fixed prior based Bayesian algorithms. These are termed as dynamic priors, which unlike other priors modify itself recursively according to the noise level in the reconstruction. It is found that inclusion of prior knowledge in the reconstruction algorithm results in local minimums. In the present approach, appropriate prior energy is supplied to the estimate to overcome local minimums by scheduling Gibbs hyperparameter and subsequently the effect of prior is removed recursively as the estimate approaches global minimum.

Item Type: Conference Paper
Publisher: IEEE
Additional Information: �©1990 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.
Keywords: Hyperparameter scheduling;Maximum aposteriori; Maximum likelihood;Positron emission tomography; Dynamic priors;Local minimum
Department/Centre: Division of Physical & Mathematical Sciences > Physics
Date Deposited: 22 Dec 2005
Last Modified: 19 Sep 2010 04:22
URI: http://eprints.iisc.ac.in/id/eprint/4726

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