title: Optimal scan time for evaluation of parathyroid adenoma with [(18)F]-fluorocholine PET/CT.
abstract: BACKGROUND
  Parathyroid adenomas, the most common cause of primary hyperparathyroidism, are benign tumours which autonomously produce and secrete parathyroid hormone. [(18)F]-fluorocholine (FCH), PET marker of cellular proliferation, was recently demonstrated to accumulate in lesions representing enlarged parathyroid tissue; however, the optimal time to perform FCH PET/CT after FCH administration is not known. The aim of this study was to determine the optimal scan time of FCH PET/CT in patients with primary hyperparathyroidism.
  
  
  METHODS
  43 patients with primary hyperparathyroidism were enrolled in this study. A triple-phase PET/CT imaging was performed five minutes, one and two hours after the administration of FCH. Regions of interest (ROI) were placed in lesions representing enlarged parathyroid tissue and thyroid tissue. Standardized uptake value (SUVmean), retention index and lesion contrast for parathyroid and thyroid tissue were calculated.
  
  
  RESULTS
  Accumulation of FCH was higher in lesions representing enlarged parathyroid tissue in comparison to the thyroid tissue with significantly higher SUVmean in the second and in the third phase (p < 0.0001). Average retention index decreased significantly between the first and the second phase and increased significantly between the second and the third phase in lesions representing enlarged parathyroid tissue and decreased significantly over all three phases in thyroid tissue (p< 0.0001). The lesion contrast of lesions representing enlarged parathyroid tissue and thyroid tissue was significantly better in the second and the third phase compared to the first phase (p < 0.05).
  
  
  CONCLUSIONS
  According to the results the optimal scan time of FCH PET/CT for localization of lesions representing enlarged parathyroid tissue is one hour after administration of the FCH.
authors.affiliation: Department for Nuclear Medicine, University Medical Centre Ljubljana, Slovenia.
authors.forename: Sebastijan
authors.initials: S
authors.lastname: Rep
authors.affiliation: Department for Nuclear Medicine, University Medical Centre Ljubljana, Slovenia.
authors.forename: Luka
authors.initials: L
authors.lastname: Lezaic
authors.affiliation: Department of Endocrinology, Diabetes and Metabolic Diseases, University Medical Centre Ljubljana, Slovenia.
authors.forename: Tomaz
authors.initials: T
authors.lastname: Kocjan
authors.affiliation: Department of Endocrinology, Diabetes and Metabolic Diseases, University Medical Centre Ljubljana, Slovenia.
authors.forename: Marija
authors.initials: M
authors.lastname: Pfeifer
authors.affiliation: Department of Endocrinology, Diabetes and Metabolic Diseases, University Medical Centre Ljubljana, Slovenia.
authors.forename: Mojca Jensterle
authors.initials: MJ
authors.lastname: Sever
authors.affiliation: Jozef Stefan Institute, Ljubljana, Slovenia.
authors.forename: Urban
authors.initials: U
authors.lastname: Simoncic
authors.affiliation: Department for Nuclear Medicine, University Medical Centre Ljubljana, Slovenia.
authors.forename: Petra
authors.initials: P
authors.lastname: Tomse
authors.affiliation: Department of Oncological Surgery, Institute of Oncology Ljubljana, Ljubljana, Slovenia.
authors.forename: Marko
authors.initials: M
authors.lastname: Hocevar
keywords: [18F]-fluorocholine PET/CT; lesion contrast; lesions representing enlarged parathyroid tissue; retention index; standardized up-take value; triple-phase
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