Evaluation of Multiclass Model Observers in PET LROC Studies.
A localization ROC (LROC) study was conducted to evaluate nonprewhitening matched-filter (NPW) and channelized NPW (CNPW) versions of a multiclass model observer as predictors of human tumor-detection performance with PET images. Target localization is explicitly performed by these model observers. Tumors were placed in the liver, lungs, and background soft tissue of a mathematical phantom, and the data simulation modeled a full-3D acquisition mode. Reconstructions were performed with the FORE+AWOSEM algorithm. The LROC study measured observer performance with 2D images consisting of either coronal, sagittal, or transverse views of the same set of cases. Versions of the CNPW observer based on two previously published difference-of-Gaussian channel models demonstrated good quantitative agreement with human observers. One interpretation of these results treats the CNPW observer as a channelized Hotelling observer with implicit internal noise.
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H. C. Gifford and M. A. King are with the Department of Radiology, University of Massachusetts Medical School, Worcester, MA 01655 USA (e-mail:  howard.gifford@umassmed.edu ).P. E. Kinahan is with the Department of Radiology, University of Washington, Seattle, WA 98195 USA.C. Lartizien is with CREATIS-UMR5515 CNRS-U630 INSERM, 69367 Lyon Cedex 07, France.
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