HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Gregoriou, G. K. Articles by Gullberg, G. T. Search for Related Content PubMed PubMed Citation Articles by Gregoriou, G. K. Articles by Gullberg, G. T.

Effect of Truncated Projections on Defect Detection in Attenuation-Compensated Fanbeam Cardiac SPECT

Departments of Biomedical Engineering and Radiology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina at Chapel Hill
Department of Radiology, University of Utah, Salt Lake City, Utah

Correspondence: For correspondence or reprints contact: Benjamin M. W. Tsui, PhD, CB 7575, 152 MacNider Hall, University of North Carolina, Chapel Hill, NC 27599.

ABSTRACT

For some camera systems used in cardiac SPECT, the limited field of view of fanbeam-collimated detectors produces truncation in the projection data. This truncation may generate artifacts and distortions in the transmission CT images and in the attenuation-corrected myocardial SPECT images (that use the transmission CT images as attenuation maps), thus affecting clinical diagnosis. Concern over this problem stimulated us to evaluate the effect of truncation with human observer performance studies. Methods: A three-dimensional mathematical cardiac-torso phantom that realistically models the attenuation and ²⁰¹Tl uptake distributions in different organs of the upper torso was used for the investigation. Five degrees of truncation (from 0% to 40% truncation) in the projection data were simulated by the use of five different detector sizes collimated by fanbeam collimators. The attenuation maps were obtained by reconstructing the truncated transmission data generated from these fanbeam geometries. The emission data obtained with the same fanbeam geometries were reconstructed by using the maximum likelihood-expectation maximization algorithm and were corrected for attenuation using the reconstructed attenuation maps. Two observer performance studies were performed. In Study 1, the images were reconstructed without using the body contour as support, whereas in Study 2, the exact body contour was used in reconstructing both the attenuation maps and the attenuation-corrected SPECT images. Results: The results of the receiver operating characteristics analysis indicate that there is very little difference between detection for the various degrees of truncation, and this difference only becomes noticeable for severe truncation of greater than 40%. Conclusion: Using the acquisition and processing methods, we found the use of the body contour as support in reconstructing truncated transmission CT and SPECT data reduces the loss of defect detectability in attenuation-compensated myocardial SPECT images due to truncated data.

Key Words: fanbeam myocardial SPECT • truncated projection • observer performance study • receiver operating characteristics study