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Titolo: OBJECTIVE ASSESSMENT OF IMAGE QUALITY  III  ROC METRICS, IDEAL OBSERVERS, AND LIKELIHOODGENERATING FUNCTIONS
Autore: BARRETT HH; ABBEY CK; CLARKSON E;
 Indirizzi:
 UNIV ARIZONA,DEPT RADIOL,CTR OPT SCI TUCSON AZ 85724 UNIV ARIZONA,PROGRAM APPL MATH TUCSON AZ 85724
 Titolo Testata:
 Journal of the Optical Society of America. A, Optics, image science,and vision.
fascicolo: 6,
volume: 15,
anno: 1998,
pagine: 1520  1535
 SICI:
 10847529(1998)15:6<1520:OAOIQ>2.0.ZU;2R
 Fonte:
 ISI
 Lingua:
 ENG
 Soggetto:
 NOISE PROPERTIES; EM ALGORITHM;
 Tipo documento:
 Article
 Natura:
 Periodico
 Settore Disciplinare:
 Science Citation Index Expanded
 Citazioni:
 23
 Recensione:
 Indirizzi per estratti:



 Citazione:
 H.H. Barrett et al., "OBJECTIVE ASSESSMENT OF IMAGE QUALITY  III  ROC METRICS, IDEAL OBSERVERS, AND LIKELIHOODGENERATING FUNCTIONS", Journal of the Optical Society of America. A, Optics, image science,and vision., 15(6), 1998, pp. 15201535
Abstract
We continue the theme of previous papers [J. Opt. Sec. Am. A 7, 1266 (1990); 12, 834 (1995)] on objective (taskbased) assessment of image quality. We concentrate on signaldetection tasks and figures of meritrelated to the ROC (receiver operating characteristic) curve. Many different expressions for the area under an ROC curve (AUC) are derived for an arbitrary discriminant function, with different assumptions on what information about the discriminant function is available. In particular, it is shown that AUC can be expressed by a principalvalue integral that involves the characteristic functions of the discriminant. Then the discussion is specialized to the ideal observer, defined as one who uses the likelihood ratio (or some monotonic transformation of it, such as its logarithm) as the discriminant function. The properties of the ideal observer are examined from first principles. Several strong constraints on the moments of the likelihood ratio or the log likelihood are derived, and it is shown that the probability density functions for these test statistics are intimately related. In particular,some surprising results are presented for the case in which the log likelihood is normally distributed under one hypothesis. To unify theseconsiderations, a new quantity called the likelihoodgenerating function is defined. It is shown that all moments of both the likelihood and the log likelihood under both hypotheses can be derived from this one function. Moreover, the AUC can be expressed, to an excellent approximation, in terms of the likelihoodgenerating function evaluated at the origin. This expression is the leading term in an asymptotic expansion of the AUG; it is exact whenever the likelihoodgenerating function behaves linearly near the origin. It is also shown that the likelihoodgenerating function at the origin sets a lower bound on the AUC in all cases. (C) 1998 Optical Society of America.
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Documento generato il 14/07/20 alle ore 19:51:09