Effects of non-optimal acquisition geometry in myocardial perfusion imaging using Ectomography

Ectomography is a limited view angle method, which has been implemented by rotating a slant hole collimator in front of a stationary gamma camera detector. The system is mobile and can be used for acute perfusion studies. To achieve high image quality in myocardial perfusion imaging, the detector should be positioned perpendicular to the long axis of the left ventricle. The aim of this study is to investigate the effects of (1) misalignment of the detector head with respect to the left ventricle, (2) truncation of the myocardial projection images and (3) external activity. Phantom studies were performed with 5 different slant hole collimators. A heart phantom, containing two defects, was placed in a thorax phantom. Studies with different degree of misalignment were performed using a mobile tomographic gamma camera. Studies with external activity present, and truncation of the apex were also performed. Results show that moderate misalignment causes little influence on size and position of the defect in the reconstructed sections, neither does presence of external activity. Effects of apical truncation do not propagate into nontruncated regions. In conclusion, positioning of a mobile system based on Ectomography does not have to be perfect, allowing rapid positioning in acute situations.