title: Improved conjugate view quantitation of I-131 by subtraction of scatter and septal penetration events with a triple energy window method.
abstract: The majority of radiation absorbed dose estimates for radioimmunotherapy (RIT) with I-131 labeled antibodies have been calculated based on in vivo quantitation of activity using the conjugate view approach with planar Anger camera images. Scatter and septal penetration events contributed by a small fraction of high-energy photons emitted by I-131 with an energy exceeding 600 KeV lead to a significant degradation of I-131 images acquired with an Anger camera, which blurs the images of uptake sites and complicates the definition of background regions. The objective of this study was to evaluate a triple energy window (TEW) subtraction method that has been used to remove these interfering events from I-131 images. In the method, a primary photopeak image for I-131 is obtained after sequential subtraction of septal penetration and scatter events by using scatter multipliers derived from a photopeak window and two adjacent scatter window images. Qualitative improvement in image contrast was demonstrated with this technique, together with more accurate and reproducible quantitation for I-131 in the organs of an abdominal phantom. This TEW scatter subtraction method can be used to provide more precise dosimetry estimates for radionuclide therapy and RIT with I-131.
authors.affiliation: University of Texas, M.D. Anderson Cancer Center, Houston 77030, USA.
authors.forename: D J
authors.initials: DJ
authors.lastname: Macey
authors.forename: E J
authors.initials: EJ
authors.lastname: Grant
authors.forename: J E
authors.initials: JE
authors.lastname: Bayouth
authors.forename: H B
authors.initials: HB
authors.lastname: Giap
authors.forename: S J
authors.initials: SJ
authors.lastname: Danna
authors.forename: R
authors.initials: R
authors.lastname: Sirisriro
authors.forename: D A
authors.initials: DA
authors.lastname: Podoloff
mesh_terms: D000005:Abdomen; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008433:Mathematics; D008962:Models, Theoretical; D019047:Phantoms, Imaging; D016499:Radioimmunotherapy / Q000295:instrumentation / Q000379:methods*; D011877:Radionuclide Imaging / Q000295:instrumentation / Q000379:methods; D011879:Radiotherapy Dosage; D012542:Scattering, Radiation
chemical_list: D007457:Iodine Radioisotopes