title: Factors affecting the normality of channel outputs of channelized model observers: an investigation using realistic myocardial perfusion SPECT images.
abstract: The channelized Hotelling observer (CHO) uses the first- and second-order statistics of channel outputs under both hypotheses to compute test statistics used in binary classification tasks. If these input data deviate from a multivariate normal (MVN) distribution, the classification performance will be suboptimal compared to an ideal observer operating on the same channel outputs. We conducted a comprehensive investigation to rigorously study the validity of the MVN assumption under various kinds of background and signal variability in a realistic population of phantoms. The study was performed in the context of myocardial perfusion SPECT imaging; anatomical, uptake (intensity), and signal variability were simulated. Quantitative measures and graphical approaches applied to the outputs of each channel were used to investigate the amount and type of deviation from normality. For some types of background and signal variations, the channel outputs, under both hypotheses, were non-normal (i.e., skewed or multimodal). This indicates that, for realistic medical images in cases where there is signal or background variability, the normality of the channel outputs should be evaluated before applying a CHO. Finally, the different degrees of departure from normality of the various channels are explained in terms of violations of the central limit theorem.
authors.affiliation: Johns Hopkins University, Whiting School of Engineering, Department of Electrical and Computer Engineering, 3400 North Charles street, Baltimore, Maryland 21218, United States; Johns Hopkins Hospital, Russell H. Morgan Department of Radiology and Radiological Science, 601 North Caroline street, Baltimore, Maryland 21287, United States.
authors.forename: Fatma E A
authors.initials: FE
authors.lastname: Elshahaby
authors.affiliation: Johns Hopkins Hospital , Russell H. Morgan Department of Radiology and Radiological Science, 601 North Caroline street, Baltimore, Maryland 21287, United States.
authors.forename: Michael
authors.initials: M
authors.lastname: Ghaly
authors.affiliation: Johns Hopkins Hospital , Russell H. Morgan Department of Radiology and Radiological Science, 601 North Caroline street, Baltimore, Maryland 21287, United States.
authors.forename: Abhinav K
authors.initials: AK
authors.lastname: Jha
authors.affiliation: Johns Hopkins Hospital , Russell H. Morgan Department of Radiology and Radiological Science, 601 North Caroline street, Baltimore, Maryland 21287, United States.
authors.forename: Eric C
authors.initials: EC
authors.lastname: Frey
keywords: channelized Hotelling observer; image quality; model observers
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