Suppression of artifacts due to data truncation when using segmented slant hole collimators in ectomography [myocardial perfusion imaging]

Ectomography is a limited view angle method, which involves rotating a slant hole collimator in front of a stationary gamma camera detector. It has been implemented on a mobile system used for acute perfusion studies. Collimators with multiple segments are used to improve system sensitivity and decrease data acquisition times. For myocardial perfusion imaging, collimators with up to 4 segments and a slant angle of 40° have been used clinically. However, severe circular artifacts may occur, if data are truncated in the projection images. The aim of this study was to investigate the effects of these artifacts, and propose ways of artifact suppression by modifying the current reconstruction algorithm; filtered backprojection. To study artifact suppression, simulations were performed using a computerized phantom. Projection data were extrapolated into the truncated region, using various techniques. Reconstructed images from the extrapolated data showed almost no circular artifacts. Successful artifact suppression was also achieved with data from an animal study. In conclusion, the authors have shown that simple extrapolation can effectively reduce data truncation artifacts when using simulated projection data. However, for clinical data, further investigation is required