Title page for ETD etd-07082011-151635

Document Type Master's Dissertation
Author Katua, Agatha Mary
Email s2763625@tuks.co.za
URN etd-07082011-151635
Document Title Comparison of filtered back projection and Osem in reducing bladder artifacts in pelvic spect imaging
Degree MSc
Department Nuclear Medicine
Advisor Name Title
Prof M M Sathekge Supervisor
  • Osem
  • filtered back projection
  • bladder artifacts
  • pelvic
Date 2011-04-08
Availability unrestricted
Bladder artifacts during bone single photon emission computed tomography (SPECT) is a common source of errors. The extent and severity of bladder artifacts have been described for filtered back projection (FBP) reconstruction. OSEM may help to address this poor record of bladder artifacts, which render up to 20% of the images unreadable.

Aims and objectives

To evaluate the relationship of the bladder to acetabulum ratio in guiding the choice of the number of iterations and subsets used for OSEM reconstruction, for reducing bladder artifacts found on FBP reconstruction.

Materials and Methods

105 patients with various indications for bone scans were selected and planar and SPECT images were acquired. The SPECT images were reconstructed with both filtered back projection and OSEM using four different combinations of iterations and subsets. The images were given to three well experienced Nuclear Physicians who were blinded to the diagnosis and type of reconstruction used. They then labelled images from the best to the worst after which the data was analysed. The bladder to acetabulum ratio for each image was determined which was then correlated with the different iterations and subsets used.


The study demonstrated that reconstruction using OSEM led to better lesion detectability compared to filtered back projection in 87.62% of cases. It further demonstrated that the iterations and subsets used for reconstruction of an image correlates to the bladder to acetabulum ratio. Four iterations and 8 subsets yielded the best results in 48.5% of the images whilst two iterations and 8 subsets yielded the best results in 33.8%. The number of reconstructed images which yielded the best results with 2 iterations and 8 subsets were the same as or more than those with 4 iterations and 8 subsets when the bladder/acetabulum ratio was between 0.2-0.39. A ratio below 0.2 or above 0.39 supports the usage of 4 iterations and 8 subsets over 2 iterations and 8 subsets.


Bladder to acetabulum ratio can be used to select the optimum number of iterations and subsets for reconstruction of bone SPECT for accurate characterization of lesions. This study also confirms that reconstruction with OSEM (vs FBP) leads to better lesion detectability and characterisation.

2010, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria.

Please cite as follows:

Katau, AM 2010, Comparison of filtered back projection and Osem in reducing bladder artifacts in pelvic spect imaging, MSc dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-07082011-151635 / >


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