Authors: John C Dickson Livia TossiciBolt Terez Sera Kjell Erlandsson Andrea Varrone Klaus Tatsch Brian F Hutton
Publish Date: 2009/07/18
Volume: 37, Issue: 1, Pages: 23-
Abstract
Reconstruction of DaTSCAN brain studies using OSEM iterative reconstruction offers better image quality and more accurate quantification than filtered backprojection However reconstruction must proceed for a sufficient number of iterations to achieve stable and accurate data This study assessed the impact of the number of iterations on the image quantification comparing the results of the iterative reconstruction with filtered backprojection dataA striatal phantom filled with 123I using striatal to background ratios between 21 and 101 was imaged on five different gamma camera systems Data from each system were reconstructed using OSEM which included depthindependent resolution recovery with various combinations of iterations and subsets to achieve up to 200 EMequivalent iterations and with filtered backprojection Using volume of interest analysis the relationships between image reconstruction strategy and quantification of striatal uptake were assessedFor phantom filling ratios of 51 or less significant convergence of measured ratios occurred close to 100 EMequivalent iterations whereas for higher filling ratios measured uptake ratios did not display a convergence pattern Assessment of the count concentrations used to derive the measured uptake ratio showed that nonconvergence of low background count concentrations caused peaking in higher measured uptake ratios Compared to filtered backprojection OSEM displayed larger uptake ratios because of the resolution recovery applied in the iterative algorithmThe number of EMequivalent iterations used in OSEM reconstruction influences the quantification of DaTSCAN studies because of incomplete convergence and possible bias in areas of low activity due to the nonnegativity constraint in OSEM reconstruction Nevertheless OSEM using 100 EMequivalent iterations provides the best linear discriminatory measure to quantify the uptake in DaTSCAN studiesThis investigation was part of a project launched by EANM Research Ltd EARL/European Network of Excellence for Brain Imaging whose aim is to create a European Normal Control Database of DaTSCAN ENCDAT More details can be found at http//wwweanmorg/earl/pilotphpnavId=497 EARL/European Network of Excellence for Brain Imaging would like to thank GE Healthcare and the German Parkinson Association for their financial contribution to this study This work was undertaken at UCLH/UCL where a proportion of the funding was received from the Department of Health’s NIHR Biomedical Research Centres funding scheme
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