title: Impact of the Fano Factor on Position and Energy Estimation in Scintillation Detectors.
abstract: The Fano factor for an integer-valued random variable is defined as the ratio of its variance to its mean. Light from various scintillation crystals have been reported to have Fano factors from sub-Poisson (Fano factor < 1) to super-Poisson (Fano factor > 1). For a given mean, a smaller Fano factor implies a smaller variance and thus less noise. We investigated if lower noise in the scintillation light will result in better spatial and energy resolutions. The impact of Fano factor on the estimation of position of interaction and energy deposited in simple gamma-camera geometries is estimated by two methods - calculating the Cramér-Rao bound and estimating the variance of a maximum likelihood estimator. The methods are consistent with each other and indicate that when estimating the position of interaction and energy deposited by a gamma-ray photon, the Fano factor of a scintillator does not affect the spatial resolution. A smaller Fano factor results in a better energy resolution.
authors.affiliation: Department of Medical Imaging and College of Optical Sciences, University of Arizona, Tucson, AZ 85225 USA ( bora.vaibhav@gmail.com ).
authors.forename: Vaibhav
authors.initials: V
authors.lastname: Bora
authors.affiliation: Department of Medical Imaging and College of Optical Sciences, University of Arizona, Tucson, AZ 85225 USA.
authors.forename: Harrison H
authors.initials: HH
authors.lastname: Barrett
authors.affiliation: Division of Medical Imaging Physics, Department of Radiology and Radiological Sciences, Johns Hopkins University, Baltimore, MD 21287 USA.
authors.forename: Abhinav K
authors.initials: AK
authors.lastname: Jha
authors.affiliation: Department of Medical Imaging and College of Optical Sciences, University of Arizona, Tucson, AZ 85225 USA.
authors.forename: Eric
authors.initials: E
authors.lastname: Clarkson
keywords: Cramér-Rao bound; Fano factor; Fisher information matrix; energy estimation; energy resolution; maximum-likelihood estimator; position estimation; scintillators; spatial resolution