title: The Combination of In vivo (124)I-PET and CT Small Animal Imaging for Evaluation of Thyroid Physiology and Dosimetry.
abstract: OBJECTIVE
  A thyroid rat model combining functional and anatomical information would be of great benefit for better modeling of thyroid physiology and for absorbed dose calculations. Our aim was to show that (124)I-PET and CT small animal imaging are useful as a combined model for studying thyroid physiology and dose calculation.
  
  
  METHODS
  Seven rats were subjects for multiple thyroid (124)I-imaging and CT-scans. S-values [mGy/MBqs] for different thyroid sizes were simulated. A phantom with spheres was designed for validation of performances of the small animal PET and CT imaging systems.
  
  
  RESULTS
  Small animal image-based measurements of the activity amount and the volumes of the spheres with a priori known volumes showed a good agreement with their corresponding actual volumes. The CT scans of the rats showed thyroid volumes from 34-70 mL.
  
  
  CONCLUSIONS
  The wide span in volumes of thyroid glands indicates the importance of using an accurate volume-measuring technique such as the small animal CT. The small animal PET system was on the other hand able to accurately estimate the activity concentration in the thyroid volumes. We conclude that the combination of the PET and CT image information is essential for quantitative thyroid imaging and accurate thyroid absorbed dose calculation.
authors: Cluster for Molecular Imaging, Faculty of Health Sciences, University of Copenhagen, Copenhagen DK-2200, Denmark. helali@sund.ku.dk.|Department of Clinical Physiology, Nuclear Medicine & PET, Rigshospitalet, Blegdamsvej 9, Copenhagen 2100, Denmark. helali@sund.ku.dk.
authors: Henrik H
authors: HH
authors: El-Ali
authors: Medical Radiation Physics, Department of Clinical Sciences, University of Lund, Lund SE-221 85, Sweden. martin.eckerwall@siemens.com.
authors: Martin
authors: M
authors: Eckerwall
authors: Cluster for Molecular Imaging, Faculty of Health Sciences, University of Copenhagen, Copenhagen DK-2200, Denmark. dskovgaard@hotmail.com.|Department of Clinical Physiology, Nuclear Medicine & PET, Rigshospitalet, Blegdamsvej 9, Copenhagen 2100, Denmark. dskovgaard@hotmail.com.
authors: Dorthe
authors: D
authors: Skovgaard
authors: Medical Radiation Physics, Department of Clinical Sciences, University of Lund, Lund SE-221 85, Sweden. erik.larsoon@med.lu.se.
authors: Erik
authors: E
authors: Larsson
authors: Medical Radiation Physics, Department of Clinical Sciences, University of Lund, Lund SE-221 85, Sweden. sven-erik.strand@med.lu.se.
authors: Sven-Erik
authors: SE
authors: Strand
authors: Cluster for Molecular Imaging, Faculty of Health Sciences, University of Copenhagen, Copenhagen DK-2200, Denmark. akjaer@sund.ku.dk.|Department of Clinical Physiology, Nuclear Medicine & PET, Rigshospitalet, Blegdamsvej 9, Copenhagen 2100, Denmark. akjaer@sund.ku.dk.
authors: Andreas
authors: A
authors: Kjaer
keywords: 124I-thyroid imaging; animal PET/CT co-registration; molecular imaging; rat S-values; small animal dosimetry; thyroid rat model