title: Pretherapeutic dosimetry in patients affected by metastatic thyroid cancer using 124I PET/CT sequential scans for 131I treatment planning.
abstract: OBJECTIVE
  This study evaluates the use of sequential I PET/CT for predicting absorbed doses to metastatic lesions in patients with differentiated thyroid cancer undergoing I therapy.
  
  
  METHODS
  From July 2011 until July 2013, 30 patients with metastatic differentiated thyroid cancer were enrolled. Each participant underwent PET/CT at 4, 24, 48, and 72 hours with 74 MBq of I. Blood samples and whole-body exposure measurements were obtained to calculate blood and red marrow doses. Activity concentrations and lesion volumes obtained from PET/CT were used to evaluate tumor doses with medical internal radiation dose formalism and spheres modeling. Mean administered I therapeutic dose was 5994 MBq (range, 1953-11,455 MBq).
  
  
  RESULTS
  I PET/CT demonstrated all lesions detected by posttherapy I whole-body scans. Mean dose rates for blood, red marrow, and lesions were as follows: 0.07 ± 0.02 mGy/MBq, 0.05 ± 0.02 mGy/MBq, and 46.5 ± 117 mGy/MBq, respectively. Despite the high level of thyroid-stimulating hormone and CT detectable lesions, 15 of 30 patients did not show any abnormal I uptake.
  
  
  CONCLUSIONS
  The quantitative value of I PET/CT allows simple and accurate evaluation of lesion dosimetry following medical internal radiation dose formalism. Negative I PET/CT predicts absence of iodine avidity, potentially allowing avoidance of therapeutically ineffective I administration.
authors: From the *Department of Medical Physics, Sant'Orsola-Malpighi, Bologna, Italy; †Department of Medical Physics, Velindre Cancer Centre, Cardiff, United Kingdom; ‡Department of Nuclear Medicine, Sant'Orsola-Malpighi, Bologna; §Department of Nuclear Medicine, Santa Maria della Misericordia Hospital, Rovigo; and ¶Department of Radiotherapy, Sant'Orsola-Malpighi, Bologna, Italy; and ∥Department of Radiology, University of Southern California, Los Angeles, CA.
authors: Cinzia
authors: C
authors: Pettinato
authors: Emiliano
authors: E
authors: Spezi
authors: Cristina
authors: C
authors: Nanni
authors: Gaia
authors: G
authors: Grassetto
authors: Fabio
authors: F
authors: Monari
authors: Vincenzo
authors: V
authors: Allegri
authors: Simona
authors: S
authors: Civollani
authors: Simona
authors: S
authors: Cima
authors: Paolo
authors: P
authors: Zagni
authors: Renzo
authors: R
authors: Mazzarotto
authors: Patrick M
authors: PM
authors: Colletti
authors: Domenico
authors: D
authors: Rubello
authors: Stefano
authors: S
authors: Fanti
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D009362:Neoplasm Metastasis / Q000000981:diagnostic imaging / Q000532:radiotherapy; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals / Q000627:therapeutic use; D011879:Radiotherapy Dosage; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy; D014057:Tomography, X-Ray Computed
chemical_list: D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals