The diagnosis of medical conditions and subsequent treatment often involves radionuclide imaging techniques. To refine localisation accuracy and improve diagnostic confidence, compared to the use of a single scanning technique, a combination of two (or more) techniques can be used but with a higher risk of misalignment. For this to be reliable and accurate, recorded data undergoes processing to suppress noise and enhance resolution. A step in image processing techniques for such inverse problems is the inclusion of smoothing. Standard approaches, however, are usually limited to applying identical models globally. In this paper, we propose a novel Laplace and Gaussian mixture prior distribution which incorporates different smoothing strategies with the automatic model-based estimation of mixture component weightings creating a locally adaptive model. A fully Bayesian approach is presented using multi-level hierarchical modelling and Markov Chain Monte Carlo (MCMC) estimation methods to sample from the posterior distribution and hence to perform estimation. The proposed methods are assessed using simulated γ-eye™ camera images and demonstrate greater noise reduction compared to existing methods but without compromising resolution. As well as image estimates, the MCMC methods also provide posterior variance estimates and hence uncertainty quantification takes into consideration any potential sources of variability. The use of mixture prior models, part Laplace random field and part Gaussian random field, within a Bayesian modelling approach is not limited to medical imaging applications but provides a more general framework for analysing other spatial inverse problems. Locally adaptive prior distributions gives a more realistic model which leads to robust results and hence more reliable decision making, especially in nuclear medicine. They can become a standard part of the toolkit of everyone working in image processing applications.
CORE (COnnecting REpositories)
CORE (COnnecting REpositories)