INVESTIGATION OF MYOCARDIAL SHORT-SCAN SPECT SCHEMES USING A REAL INHOMOGENEOUS ATTENUATING MEDIUM

Abstract

In myocardial perfusion SPECT imaging the effect of photon attenuation may introduce artifacts in the reconstructed image due to the highly non-uniform distribution of tissue in the thorax region, potentially resulting in false-positive interpretations. It was the general consideration that the adequate compensation of photon attenuation requires, that the emission data be measured at projection angles over 2 π in the case the attenuation medium is inhomogeneous. The reduction of the scanning angle in SPECT imaging may be desirable because it can reduce scanning time and thereby minimize patient-motion and other artifacts. In SPECT myocardial imaging emission data is measured historically at projection angles over π from the right anterior oblique (RAO) to the left posterior oblique (LPO). This configuration results in better image contrast and, in some cases, better spatial resolution. However, in this case the reconstructed image may suffer more severely from geometric distortion than 2π angular sampling. It has been proven recently in analytical computer simulation studies that the data function over 2 π in SPECT with non-uniform attenuation contains redundant information; therefore the scanning angle theoretically can be reduced from 2π to π without loss of information. In this study our goal was to investigate how the various short-scan SPECT scheme configurations work in a real myocardial SPECT imaging system with highly inhomogeneous attenuating medium using attenuation correction. The measured projection images were reconstructed using the Maximum Likelihood Expectation Maximization algorithm with attenuation correction. The reconstructed slices of the various short-scan configurations and the full-scan slices were compared by a cardiac stress/rest software package.