title: Individualized dosimetry in patients undergoing therapy with (177)Lu-DOTA-D-Phe (1)-Tyr (3)-octreotate.
abstract: OBJECTIVE
  In recent years, targeted radionuclide therapy with [(177)Lu-DOTA(0), Tyr(3)]octreotate for neuroendocrine tumours has yielded promising results. This therapy may be further improved by using individualized dosimetry allowing optimization of the absorbed dose to the tumours and the normal organs. The aim of this study was to investigate the feasibility and reliability of individualized dosimetry based on SPECT in comparison to conventional planar imaging.
  
  
  METHODS
  Attenuation-corrected SPECT data were analysed both by using organ-based volumes of interest (VOIs) to obtain the total radioactivity in the organ, and by using small VOIs to measure the tissue radioactivity concentration. During the first treatment session in 24 patients, imaging was performed 1, 24, 96 and 168 h after [(177)Lu-DOTA(0), Tyr(3)]octreotate infusion. Absorbed doses in non tumour-affected kidney, liver and spleen were calculated and compared for all three methods (planar imaging, SPECT organ VOIs, SPECT small VOIs).
  
  
  RESULTS
  Planar and SPECT dosimetry were comparable in areas free of tumours, but due to overlap the planar dosimetry highly overestimated the absorbed dose in organs with tumours. Furthermore, SPECT dosimetry based on small VOIs proved to be more reliable than whole-organ dosimetry.
  
  
  CONCLUSIONS
  We conclude that SPECT dosimetry based on small VOIs is feasible and more accurate than conventional planar dosimetry, and thus may contribute towards optimising targeted radionuclide therapy.
authors.affiliation: Department of Oncology, Radiology and Clinical Immunology, Uppsala University Hospital, 751 85, Uppsala, Sweden. mattias.sandstrom@akademiska.se
authors.forename: Mattias
authors.initials: M
authors.lastname: Sandström
authors.forename: Ulrike
authors.initials: U
authors.lastname: Garske
authors.forename: Dan
authors.initials: D
authors.lastname: Granberg
authors.forename: Anders
authors.initials: A
authors.lastname: Sundin
authors.forename: Hans
authors.initials: H
authors.lastname: Lundqvist
mesh_terms: D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D018358:Neuroendocrine Tumors / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D015282:Octreotide / Q000031:analogs & derivatives* / Q000627:therapeutic use; D011874:Radiometry / Q000379:methods*; D019275:Radiopharmaceuticals / Q000627:therapeutic use; D011879:Radiotherapy Dosage; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*
chemical_list: C504257:177Lu-octreotide, DOTA(0)-Tyr(3)-; D019275:Radiopharmaceuticals; D015282:Octreotide