title: Prediction of absorbed dose to normal organs in thyroid cancer patients treated with 131I by use of 124I PET and 3-dimensional internal dosimetry software.
abstract: The objective of this work was to determine normal organ (131)I dosimetry in patients undergoing radioiodide therapy for thyroid cancer by use of serial scanning with (124)I PET.
  
  
  METHODS
  A total of 26 patients who had papillary and follicular metastatic thyroid cancer and who were already enrolled in a Memorial Sloan-Kettering Cancer Center (131)I thyroid cancer protocol were selected for this study. Imaging before (131)I therapy consisted of multiple, whole-body (124)I PET studies over a period of 2-8 d, an (18)F-FDG PET scan and, for some, a diagnostic CT scan. With a set of in-house-developed software tools (3-dimensional internal dosimetry [3D-ID] and Multiple Image Analysis Utility [MIAU]), the following procedures were performed: all PET emission and transmission and CT image sets were aligned; half-life-corrected tomographic images of (131)I activity were integrated voxel by voxel to produce cumulated (131)I activity images; and the latter images were, in turn, convolved with a (131)I electron-photon point kernel to produce images of (131)I dose distribution. Cumulated activity values and calculated residence times obtained from our patient-specific dosimetry software (3D-ID) were used as inputs to OLINDA, and volume difference-adjusted comparisons were made between the mean dose estimates.
  
  
  RESULTS
  With 3D-ID, dose volume histograms and mean doses were calculated for 14 organs, and results were expressed in Gy/GBq. The highest mean dose, 0.26 Gy/GBq, was seen in the right submandibular gland, whereas the lowest mean dose, 0.029 Gy/GBq, was seen in the brain.
  
  
  CONCLUSIONS
  This is the first comprehensive study of normal organ dosimetry in patients by use of a quantitative tomographic imaging modality.
authors.affiliation: Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA. katherinenyc@att.net
authors.forename: Katherine S
authors.initials: KS
authors.lastname: Kolbert
authors.forename: Keith S
authors.initials: KS
authors.lastname: Pentlow
authors.forename: Joel R
authors.initials: JR
authors.lastname: Pearson
authors.forename: Arif
authors.initials: A
authors.lastname: Sheikh
authors.forename: Ronald D
authors.initials: RD
authors.lastname: Finn
authors.forename: John L
authors.initials: JL
authors.lastname: Humm
authors.forename: Steven M
authors.initials: SM
authors.lastname: Larson
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000295:instrumentation* / Q000379:methods; D016499:Radioimmunotherapy / Q000379:methods; D011874:Radiometry; D012984:Software; D013961:Thyroid Gland / Q000000981:diagnostic imaging*; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D014018:Tissue Distribution
chemical_list: D007457:Iodine Radioisotopes