title: Scattered radiation effects on the extrinsic sensitivity and counting efficiency of a gamma camera.
abstract: An evaluation of the effect of scattered radiation on the performance of a gamma camera is carried out using a specially designed home-made homogeneous circular planar flood source filled with 0.2±0.01 GBq of (99m)Tc solution as a scattering medium. The scatter effects are assessed by analyzing the energy spectrum of (99m)Tc for the scatter fraction and calculating the camera's extrinsic counting efficiency and sensitivity, for five flood source thicknesses (12, 50, 100, 150 and 200 mm ) and three source-to-detector distances (0.7, 0.9 and 1.1 m). Results showed an increase in the scatter fraction from 0.29 to 22.96 as the source thickness increased. This increase was associated with a decrease in the extrinsic sensitivity from 121.36 to 49.58 counts/s GBq, and a decrease in counting efficiency as from 3.78 to 1.55%. With the increase in source-to-detector distance, the extrinsic sensitivity decreases from 121.36 to 118.77 counts/s GBq, while the counting efficiency increases from 3.78 to 11.66%. It was found that a source-to-detector distance of 0.96±9×10(-3) m is a good compromise for an acceptable extrinsic sensitivity and a reasonable counting efficiency.
authors.affiliation: Biophysics Department, Faculty of Science, Cairo University, Egypt. waelelshemey@yahoo.com
authors.forename: Wael M
authors.initials: WM
authors.lastname: Elshemey
authors.forename: Mohamed A
authors.initials: MA
authors.lastname: Ghoneim
authors.forename: M H
authors.initials: MH
authors.lastname: Khader
mesh_terms: D016477:Artifacts; D004867:Equipment Design; D019544:Equipment Failure Analysis; D015902:Gamma Cameras; D005720:Gamma Rays; D015203:Reproducibility of Results; D012542:Scattering, Radiation; D012680:Sensitivity and Specificity; D013667:Technetium / Q000032:analysis* / Q000737:chemistry*
chemical_list: D013667:Technetium