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The Influence of Collimators on SPECT Center of Rotation Measurements: Artifact Generation and Acceptance Testing

Department of Radiology, Division of Nuclear Medicine, and the Department of Medicine, Division of Cardiology, Veterans Administration Medical Center and the University of Washington, Seattle, WA

Correspondence: For reprints contact: Manuel Cerqueira, MD, VA Medical Center, 1660 S. Columbian Way, Seattle, WA 98108

ABSTRACT

Misalignment between the electronic and mechanical axes of rotation will result in artifact generation and image degradation during single photon emission computed tomography (SPECT) reconstruction. Acceptance and quality control testing procedures have not emphasized the variability in center of rotation (COR) measurements caused by collimators and the need to verify uniformity across the full collimator field of view (FOV).Variation from the mean COR across the FOV was tested in four different collimators using multiple point source acquisitions. The mean COR was different for each collimator and two of the four had a >0.5 pixel difference from the mean COR on some area of the FOV. This variation makes these collimators unacceptable for SPECT acquisition. Thus, initial acceptance testing of SPECT collimators should verify a uniform COR across the full FOV and collimators with a variability from the mean COR>0.5 pixels should be rejected.