title: Determination of individual S-values for 131I using segmented CT data and the EGS4 Monte Carlo code.
abstract: In individual voxel phantoms, which were segmented from whole-body computed tomography (CT) scans, S-values were calculated for (131)I using the EGS4 Monte Carlo code and compared to Medical Internal Radiation Dose (MIRD) S-values, which were derived from transport calculations in idealized mathematical phantoms. The individually calculated S-values agree very well with the MIRD values for organs, which are source and target simultaneously, when individual organ-mass corrections are applied to the MIRD values. For different source-target combinations, large deviations up to 184% were found. The contribution of the gamma-absorbed fractions to the total dose, however, is small ( approximately 4%). We conclude, therefore, that individual transport calculations in radionuclide-targeted therapies are not necessary for macroscopic dose estimates. Reliable dosimetry is reduced to the problem of accurate activity determination in vivo.
authors.affiliation: Nuklearmedizinische Klinik und Poliklinik der Technischen Universität München, Germany. i.wolf@lrz.tum.de
authors.forename: Ingo
authors.initials: I
authors.lastname: Wolf
authors.forename: Maria
authors.initials: M
authors.lastname: Zankl
authors.forename: Klemens
authors.initials: K
authors.lastname: Scheidhauer
authors.forename: Eugenia
authors.initials: E
authors.lastname: Vabuliene
authors.forename: Dieter
authors.initials: D
authors.lastname: Regulla
authors.forename: Christoph
authors.initials: C
authors.lastname: von Schilling
authors.forename: Markus
authors.initials: M
authors.lastname: Schwaiger
mesh_terms: D001853:Bone Marrow / Q000187:drug effects; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D007668:Kidney / Q000528:radiation effects; D008297:Male; D008962:Models, Theoretical; D009010:Monte Carlo Method; D019047:Phantoms, Imaging; D011874:Radiometry / Q000379:methods; D012984:Software; D014018:Tissue Distribution; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014916:Whole-Body Irradiation
chemical_list: D007457:Iodine Radioisotopes