title: Count-based monitoring of Anger-camera spectra--local energy shifts due to rotation.
abstract: This study reports on a spectral monitoring method in which (1) a small source fixed to the camera is used, (2) a narrow, offset window is set on the side of the photopeak, and (3) variations in count rate are measured to assess energy shifts in the vicinity of the source. For one camera model, the count rate drops from 100% to 76% over a rotation of 180 degrees, implying a local energy shift of 1.4 keV. Also looked for are local count-rate variations with rotation for (1) wide-symmetric, (2) 20%-symmetric, and (3) 10%-asymmetric windows. The last is in limited use to partially compensate for Compton scattering. The effects of background and time stability are assessed.
authors.affiliation: Department of Internal Medicine, University of Michigan Medical School, Ann Arbor 48109.
authors.forename: F M
authors.initials: FM
authors.lastname: Swailem
authors.forename: K F
authors.initials: KF
authors.lastname: Koral
authors.forename: W L
authors.initials: WL
authors.lastname: Rogers
mesh_terms: D015902:Gamma Cameras / Q000592:standards*; D012399:Rotation