In this paper we report the effect of the configuration of the orbit of the detector head around the heart during in-vivo SPECT imaging with Tc99m-MIBI. Additional work has also implicated the effect of detector orbit on artifact creation in-vitro using Tl201. Instrumentation factors may also be the cause of artifacts due to center of rotation offset, flood nonuniformity, and nonlinearity of the detector, flaws in collimator construction, or mechanical inaccuracy of the gantry, which have all been reported to be possible sources of artifacts on Tl201 reconstructed slices. Other potential causes of artifacts include patient motion, respiratory motion, cardiac blurring in non-gated studies, and “upward creep” of the heart. Attenuation by the breast, diaphragm, and right ventricle can be the origin of some of these artifacts. Nonetheless the complexity of SPECT makes it more prone to artifact creation than planar imaging. Much work has demonstrated improved detection of coronary artery disease and improved localization of disease in specific coronary artery territories. In particular 2 cases with anterior wall defects had less cardiac centering on the rest images than the stress images on which these defects were no longer visible.Ĭonclusion: Increasing the distance between the COR of a SPECT acquisition and the anatomic center of the heart causes increasing anterior wall defects to be detected in vivo and may be contributing to artifacts in a daily clinical setting when using 180 degree acquisitions.Ĭompared to planar cardiac scintigraphic imaging, SPECT allows separation of superimposed myocardium and provides higher contrast images. Analysis demonstrated increasing number of anterior wall defects as the COR moved from heart centered to body centered with an odds ratio of 2.5 for number of anterior wall defects in body centered vs. Results: Kappa statistics demonstrated good (>0.70) agreement between observers. Kappa statistic was calculated between observers and Maentel-Hentzel test for trend between number of anterior wall defects and increasing body centering in the COR of the SPECT acquisition was calculated.
The SPECT reconstruction data was interpreted for anterior wall defects on rest and stress images. The raw projectional data was rated as body centered, heart centered, or in between using a nominal scale. All image data was evaluated by two radiologists blinded to each others readings.
Methods: 44 patients underwent stress and rest Tc99m-Sestamibi SPECT myocardial scintigraphy using 20-30mCi (740-1070 MBq) and 8-10mCi (259-370 MBq) respectively (64 and 32 views at 30sec/view) using a Siemens Orbiter camera. The purpose of this study was to quantify the effects of center of rotation (COR) placement at the heart, or body centered circular orbits in patients. Purpose: During cardiac SPECT acquisitions in-vitro work has shown that artifacts that may be prospectively interpreted as anterior wall defects can be caused by body centered acquisitions rather than heart centered acquisitions.
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