title: Testis dosimetry in individual patients by combining a small-scale dosimetry model and pharmacokinetic modeling-application of (111)In-Ibritumomab Tiuxetan (Zevalin(®)).
abstract: A heterogeneous distribution of radionuclides emitting low-energy electrons in the testicles may result in a significant difference between an absorbed dose to the radiosensitive spermatogonia and the mean absorbed dose to the whole testis. This study focused on absorbed dose distribution in patients at a finer scale than normally available in clinical dosimetry, which was accomplished by combining a small-scale dosimetry model with patient pharmacokinetic data. The activity in the testes was measured and blood sampling was performed for patients that underwent pre-therapy imaging with (111)In-Zevalin(®). Using compartment modeling, testicular activity was separated into two components: vascular and extravascular. The uncertainty of absorbed dose due to geometry variations between testicles was explored by an assumed activity micro-distribution and by varying the radius of the interstitial tubule. Results showed that the absorbed dose to germ cells might be strongly dependent on the location of the radioactive source, and may exceed the absorbed dose to the whole testis by as much as a factor of two. Small-scale dosimetry combined with compartmental analysis of clinical data proved useful for gauging tissue dosimetry and interpreting how intrinsic geometric variation influences the absorbed dose.
authors.affiliation: Medical Radiation Physics, Department of Clinical Sciences, Lund, Lund University, SE-221 00 Lund, Sweden. University of Duhok, Duhok, Iraq.
authors.forename: Suaad A
authors.initials: SA
authors.lastname: Meerkhan
authors.forename: Katarina
authors.initials: K
authors.lastname: Sjögreen-Gleisner
authors.forename: Erik
authors.initials: E
authors.lastname: Larsson
authors.forename: Sven-Erik
authors.initials: SE
authors.lastname: Strand
authors.forename: Bo-Anders
authors.initials: BA
authors.lastname: Jönsson
mesh_terms: D000911:Antibodies, Monoclonal / Q000493:pharmacokinetics* / Q000627:therapeutic use; D006801:Humans; D007205:Indium Radioisotopes / Q000493:pharmacokinetics* / Q000627:therapeutic use; D016393:Lymphoma, B-Cell / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy*; D008297:Male; D008954:Models, Biological; D058958:Organs at Risk; D011829:Radiation Dosage; D016499:Radioimmunotherapy; D011874:Radiometry / Q000379:methods*; D013737:Testis / Q000378:metabolism / Q000528:radiation effects*; D014018:Tissue Distribution
chemical_list: D000911:Antibodies, Monoclonal; D007205:Indium Radioisotopes; C422802:ibritumomab tiuxetan