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Influence of spatially heterogeneous background activity on "hot object" quantitation in brain emission computed
J M Links1, J K Zubieta, C C Meltzer
1Department of Radiology, School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA.
Purpose:
Our goal was to evaluate the influence of spatially heterogeneous background activity on "hot object" quantitation in brain emission CT.
Method:
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).
Results:
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.
Conclusion:
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.