Determination of individual S-values for 131I using segmented CT data and the EGS4 Monte Carlo code.
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.
Wolf
Ingo
I
Nuklearmedizinische Klinik und Poliklinik der Technischen Universität München, Germany. i.wolf@lrz.tum.de
Zankl
Maria
M
Scheidhauer
Klemens
K
Vabuliene
Eugenia
E
Regulla
Dieter
D
von Schilling
Christoph
C
Schwaiger
Markus
M
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
D007457:Iodine Radioisotopes