Influence of Spatially Heterogeneous Background Activity on “Hot Object” Quantitation in Brain Emission Computed Tomography

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Abstract
Our goal was to evaluate the influence of spatially heterogeneous background activity on "hot object" quantitation in brain emission CT. We studied the effects of spatially heterogeneous background activity on hot object quantitative recovery in simulations of both spheres and realistic brain distributions (utilizing human MRI data). Significant underestimation of object activity concentration was seen for both cortical and subcortical hot objects, with increasing underestimation for increasing hot object/surrounding gray matter contrast. Significant "spill-in" of counts from surrounding activity was present. Hot objects are significantly influenced by both "spill-out" and "spill-in." Qualitative and quantitative analyses of such objects must explicitly consider both spill-out and spill-in; this implies a correction scheme that goes beyond simple division of the observed value by a conventional recovery coefficient.